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Showing 1 - 36 of 36 Journals sorted alphabetically
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 33)
Advances in Climate Change Research     Open Access   (Followers: 8)
Advances in Meteorology     Open Access   (Followers: 18)
Advances in Statistical Climatology, Meteorology and Oceanography     Open Access   (Followers: 2)
Aeolian Research     Hybrid Journal   (Followers: 5)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 13)
American Journal of Climate Change     Open Access   (Followers: 13)
Atmósfera     Open Access   (Followers: 1)
Atmosphere     Open Access   (Followers: 21)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 12)
Atmospheric and Oceanic Science Letters     Open Access   (Followers: 1)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 28)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 10)
Atmospheric Research     Hybrid Journal   (Followers: 54)
Atmospheric Science Letters     Open Access   (Followers: 28)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 22)
Bulletin of the American Meteorological Society     Open Access   (Followers: 31)
Carbon Balance and Management     Open Access   (Followers: 5)
Change and Adaptation in Socio-Ecological Systems     Open Access   (Followers: 1)
Climate     Open Access   (Followers: 2)
Climate Change Economics     Hybrid Journal   (Followers: 12)
Climate Change Responses     Open Access   (Followers: 3)
Climate Dynamics     Hybrid Journal   (Followers: 28)
Climate law     Hybrid Journal   (Followers: 4)
Climate of the Past (CP)     Open Access   (Followers: 4)
Climate of the Past Discussions (CPD)     Open Access   (Followers: 1)
Climate Policy     Hybrid Journal   (Followers: 29)
Climate Research     Hybrid Journal   (Followers: 5)
Climate Risk Management     Open Access  
Climate Services     Open Access  
Climate Summary of South Africa     Full-text available via subscription  
Climatic Change     Hybrid Journal   (Followers: 54)
Current Climate Change Reports     Hybrid Journal   (Followers: 3)
Developments in Atmospheric Science     Full-text available via subscription   (Followers: 15)
Dynamics and Statistics of the Climate System     Open Access   (Followers: 2)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 10)
Earth Perspectives - Transdisciplinarity Enabled     Open Access  
Energy & Environment     Hybrid Journal   (Followers: 16)
Environmental and Climate Technologies     Open Access   (Followers: 3)
Global Meteorology     Open Access   (Followers: 6)
International Journal of Atmospheric Sciences     Open Access   (Followers: 23)
International Journal of Biometeorology     Hybrid Journal   (Followers: 1)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (Followers: 13)
International Journal of Climatology     Hybrid Journal   (Followers: 24)
International Journal of Image and Data Fusion     Hybrid Journal   (Followers: 2)
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (Followers: 25)
Journal of Atmospheric and Oceanic Technology     Full-text available via subscription   (Followers: 30)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 122)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 21)
Journal of Climate     Full-text available via subscription   (Followers: 40)
Journal of Hydrology and Meteorology     Open Access   (Followers: 14)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 5)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Journal of Meteorology and Climate Science     Full-text available via subscription   (Followers: 7)
Journal of Space Weather and Space Climate     Open Access   (Followers: 19)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 68)
Journal of the Meteorological Society of Japan     Partially Free   (Followers: 1)
Journal of Weather Modification     Full-text available via subscription   (Followers: 1)
Large Marine Ecosystems     Full-text available via subscription  
Mathematics of Climate and Weather Forecasting     Open Access   (Followers: 4)
Mediterranean Marine Science     Open Access   (Followers: 1)
Meteorologica     Open Access   (Followers: 1)
Meteorological Applications     Hybrid Journal   (Followers: 4)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 2)
Meteorology and Atmospheric Physics     Hybrid Journal   (Followers: 20)
Mètode Science Studies Journal : Annual Review     Open Access  
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 5)
Monthly Notices of the Royal Astronomical Society Letters     Hybrid Journal   (Followers: 4)
Monthly Weather Review     Full-text available via subscription   (Followers: 25)
Nature Climate Change     Full-text available via subscription   (Followers: 59)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 25)
Open Journal of Modern Hydrology     Open Access   (Followers: 4)
Revista Brasileira de Meteorologia     Open Access   (Followers: 1)
Revista Iberoamericana de Bioeconomía y Cambio Climático     Open Access  
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 3)
Space Weather     Full-text available via subscription   (Followers: 16)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 1)
Tellus A     Open Access   (Followers: 22)
Tellus B     Open Access   (Followers: 20)
The Cryosphere (TC)     Open Access   (Followers: 5)
The Cryosphere Discussions (TCD)     Open Access   (Followers: 3)
The Quarterly Journal of the Royal Meteorological Society     Hybrid Journal   (Followers: 21)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 6)
Urban Climate     Hybrid Journal  
Weather     Hybrid Journal   (Followers: 12)
Weather and Climate Extremes     Open Access   (Followers: 7)
Weather and Forecasting     Full-text available via subscription   (Followers: 15)
Weatherwise     Hybrid Journal   (Followers: 1)
气候与环境研究     Full-text available via subscription   (Followers: 1)
Journal Cover Journal of Atmospheric and Solar-Terrestrial Physics
  [SJR: 0.934]   [H-I: 70]   [122 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [3040 journals]
  • Analysis of a grid ionospheric vertical delay and its bounding errors over
           West African sub-Saharan region
    • Authors: O.E. Abe; X. Otero Villamide; C. Paparini; S.M. Radicella; B. Nava
      Pages: 67 - 74
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): O.E. Abe, X. Otero Villamide, C. Paparini, S.M. Radicella, B. Nava
      Investigating the effects of the Equatorial Ionization Anomaly (EIA) ionosphere and space weather on Global Navigation Satellite Systems (GNSS) is very crucial, and a key to successful implementation of a GNSS augmentation system (SBAS) over the equatorial and low-latitude regions. A possible ionospheric vertical delay (GIVD, Grid Ionospheric Vertical Delay) broadcast at a Ionospheric Grid Point (IGP) and its confidence bounds errors (GIVE, Grid Ionospheric Vertical Error) are analyzed and compared with the ionospheric vertical delay estimated at a nearby user location over the West African Sub-Saharan region. Since African sub-Saharan ionosphere falls within the EIA region, which is always characterized by a disturbance in form of irregularities after sunset, and the disturbance is even more during the geomagnetically quiet conditions unlike middle latitudes, the need to have a reliable ionospheric threat model to cater for the nighttime ionospheric plasma irregularities for the future SBAS user is essential. The study was done during the most quiet and disturbed geomagnetic conditions on October 2013. A specific low latitude EGNOS-like algorithm, based on single thin layer model, was engaged to simulate SBAS message in the study. Our preliminary results indicate that, the estimated GIVE detects and protects a potential SBAS user against sampled ionospheric plasma irregularities over the region with a steep increment in GIVE to non-monitored after local sunset to post midnight. This corresponds to the onset of the usual ionospheric plasma irregularities in the region. The results further confirm that the effects of the geomagnetic storms on the ionosphere are not consistent in affecting GNSS applications over the region. Finally, this paper suggests further work to be investigated in order to improve the threat integrity model activity, and thereby enhance the availability of the future SBAS over African sub-Saharan region.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.015
      Issue No: Vol. 154 (2017)
  • Investigation of atmospheric anomalies associated with Kashmir and Awaran
    • Authors: Irfan Mahmood; Muhammad Farooq Iqbal; Muhammad Imran Shahzad; Saddam Qaiser
      Pages: 75 - 85
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Irfan Mahmood, Muhammad Farooq Iqbal, Muhammad Imran Shahzad, Saddam Qaiser
      The earthquake precursors' anomalies at diverse elevation ranges over the seismogenic region and prior to the seismic events are perceived using Satellite Remote Sensing (SRS) techniques and reanalysis datasets. In the current research, seismic precursors are obtained by analyzing anomalies in Outgoing Longwave Radiation (OLR), Air Temperature (AT), and Relative Humidity (RH) before the two strong Mw>7 earthquakes in Pakistan occurred on 8th October 2005 in Azad Jammu Kashmir with Mw 7.6, and 24th September 2013 in Awaran, Balochistan with Mw 7.7. Multi-parameter data were computed based on multi-year background data for anomalies computation. Results indicate significant transient variations in observed parameters before the main event. Detailed analysis suggests presence of pre-seismic activities one to three weeks prior to the main earthquake event that vanishes after the event. These anomalies are due to increase in temperature after release of gases and physical and chemical interactions on earth surface before the earthquake. The parameter variations behavior for both Kashmir and Awaran earthquake events are similar to other earthquakes in different regions of the world. This study suggests that energy release is not concentrated to a single fault but instead is released along the fault zone. The influence of earthquake events on lightning were also investigated and it was concluded that there is a significant atmospheric lightning activity after the earthquake suggesting a strong possibility for an earthquake induced thunderstorm. This study is valuable for identifying earthquake precursors especially in earthquake prone areas.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.018
      Issue No: Vol. 154 (2017)
  • Response of the middle atmosphere to the geomagnetic storm of November
    • Authors: Klemens Hocke
      Pages: 86 - 91
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Klemens Hocke
      Ozone and temperature profiles of the satellite microwave limb sounder Aura/MLS are used for the derivation of the middle atmospheric response to the geomagnetic superstorm of 9 November 2004. We find a destruction of the tertiary ozone layer at 0.022hPa (77km) in the northern winter hemisphere lasting for about one week. This effect is surely due to the solar proton event (SPE) of November 2004. At the same time, the zonal mean temperature is enhanced by 5–10K in the northern polar mesosphere. On the other hand, the zonal mean temperature is decreased by 5–10K in the northern polar stratosphere. We do not think that the strong temperature perturbations are directly related to the SPE. It seems that the polar vortex was moved by the geomagnetic storm, and this vortex movement caused the strong temperature variations in the zonal mean. However, internal variability of temperature in the polar middle atmosphere in winter without any significant link to the geomagnetic storm cannot be excluded.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.013
      Issue No: Vol. 154 (2017)
  • Turbulent processes in Earth's magnetosheath by Cluster mission
    • Authors: L.V. Kozak; A.T.Y. Lui; E.A. Kronberg; A.S. Prokhorenkov
      Abstract: Publication date: Available online 5 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): L.V. Kozak, A.T.Y. Lui, E.A. Kronberg, A.S. Prokhorenkov
      Methods and approaches which can be used for the analysis of hydrodynamic and magnetohydrodynamic turbulent flows are chosen for this study. It is defined that the best methods for determination of turbulent process types are the methods of statistical physics. Within the statistical approach the fractal analysis (height of the maximum of probability density fluctuations of the studied parameters) and multifractal analysis (study of a power dependence of high order statistical moments and construction of multifractal spectrum) are considered. It is indicated that the statistical analysis of turbulent process properties can be supplemented with spectral studies (wavelet analysis). Physical processes in the transition regions of the magnetosphere: foreshock, shock, post-shock and magnetosheath are investigated using high frequency measurements by Cluster satellites. Extended self-similarity analysis and structure function analysis demonstrate the presence of super-diffusion processes and the highest values of generalized diffusion coefficients observed in post-shock region. It can be noted that different approaches for the analysis of turbulent processes give similar results and indicate the presence of super-diffusion processes in the transition region of the Earth's magnetosphere. This fact must be taken into account when constructing quantitative models of a transfer process. Wavelet analysis shows the presence of cascade and inverse cascade processes in the Earth's magnetosheath. Good agreement with other studies and our new results contribute to improvement of our understanding of turbulence.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.016
  • Accuracy assessment of the global ionospheric model over the Southern
           Ocean based on dynamic observation
    • Authors: Xiaowen Luo; Huajun Xu; Zishen Li; Tao Zhang; Jinyao Gao; Zhongyan Shen; Chunguo Yang; Wuziyin
      Abstract: Publication date: Available online 5 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Xiaowen Luo, Huajun Xu, Zishen Li, Tao Zhang, Jinyao Gao, Zhongyan Shen, Chunguo Yang, Wuziyin
      The global ionospheric model based on the reference stations of the Global Navigation Satellite System (GNSS) of the International GNSS Services is presently the most commonly used products of the global ionosphere. It is very important to comprehensively analyze and evaluate the accuracy and reliability of the model for the reasonable use of this kind of ionospheric product. In terms of receiver station deployment, this work is different from the traditional performance evaluation of the global ionosphere model based on observation data of ground-based static reference stations. The preliminary evaluation and analysis of the the global ionospheric model was conducted with the dynamic observation data across different latitudes over the southern oceans. The validation results showed that the accuracy of the global ionospheric model over the southern oceans is about 5 TECu, which deviates from the measured ionospheric TEC by about −0.6 TECu.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.017
  • A new tool for spatiotemporal pattern decomposition based on empirical
           mode decomposition: A case study of monthly mean precipitation in Taihu
           Lake Basin, China
    • Authors: Shen Chenhua; Yan Yani
      Pages: 10 - 20
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Shen Chenhua, Yan Yani
      We present a new tool for spatiotemporal pattern decomposition and utilize this new tool to decompose spatiotemporal patterns of monthly mean precipitation from January 1957 to May 2015 in Taihu Lake Basin, China. Our goal is to show that this new tool can mine more hidden information than empirical orthogonal function (EOF). First, based on EOF and empirical mode decomposition (EMD), the time series which is an average over the study region is decomposed into a variety of intrinsic mode functions (IMFs) and a residue by means of EMD. Then, these IMFs are supposed to be explanatory variables and a time series of precipitation in every station is considered as a dependent variable. Next, a linear multivariate regression equation is derived and corresponding coefficients are estimated. These estimated coefficients are physically interpreted as spatial coefficients and their physical meaning is an orthogonal projection between IMF and a precipitation time series in every station. Spatial patterns are presented depending on spatial coefficients. The spatiotemporal patterns include temporal patterns and spatial patterns at various timescales. Temporal pattern is obtained by means of EMD. Based on this temporal pattern, spatial patterns at various timescales will be gotten. The proposed tool has been applied in decomposition of spatiotemporal pattern of monthly mean precipitation in Taihu Lake Basin, China. Since spatial patterns are associated with intrinsic frequency, the new and individual spatial patterns are detected and explained physically. Our analysis shows that this new tool is reliable and applicable for geophysical data in the presence of nonstationarity and long-range correlation and can handle nonstationary spatiotemporal series and has the capacity to extract more hidden time-frequency information on spatiotemporal patterns.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.008
      Issue No: Vol. 154 (2016)
  • Rain attenuation statistics over millimeter wave bands in South Korea
    • Authors: Sujan Shrestha; Dong-You Choi
      Pages: 1 - 10
      Abstract: Publication date: January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 152–153
      Author(s): Sujan Shrestha, Dong-You Choi
      Rain induced degradations are significant for terrestrial microwave links operating at frequencies higher than 10GHz. Paper presents analyses done on rain attenuation and rainfall data for three years between 2013 till 2015, in 3.2km experimental link of 38GHz and 0.1km link at 75GHz. The less link distance is maintained for 75GHz operating frequency in order to have better recording of propagation effect as such attenuation induced by rain. OTT Parsivel is used for collection of rain rate database which show rain rate of about 50mm/h and attenuation values of 20.89 and 28.55dB are obtained at 0.01% of the time for vertical polarization under 38 and 75GHz respectively. Prediction models, namely, ITU-R P. 530-16, Da Silva Mello, Moupfouma, Abdulrahman, Lin and differential equation approach are analyzed. This studies help to identify most suitable rain attenuation model for higher microwave bands. While applying ITU-R P. 530-16, the relative error margin of about 3%, 38% and 42% along with 80, 70, 61% were obtained in 0.1%, 0.01% and 0.001% of the time for vertical polarization under 38 and 75GHz respectively. Interestingly, ITU-R P. 530-16 shows relatively closer estimation to measured rain attenuation at 75GHz with relatively less error probabilities and additionally, Abdulrahman and ITU-R P. 530-16 results in better estimation to the measured rain attenuation at 38GHz link. The performance of prominent rain attenuation models are judged with different error matrices as recommended by ITU-R P. 311-15. Furthermore, the efficacy of frequency scaling technique of rain attenuation between links distribution are also discussed. This study shall be useful for making good considerations in rain attenuation predictions for terrestrial link operating at higher frequencies.

      PubDate: 2016-11-30T09:27:24Z
      DOI: 10.1016/j.jastp.2016.11.004
      Issue No: Vol. 152-153 (2016)
  • A method for detecting equidistant frequencies in the spectrum of a
           wideband signal
    • Authors: A.R. Polyakov
      Pages: 30 - 40
      Abstract: Publication date: January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 152–153
      Author(s): A.R. Polyakov
      Examples are presented of using a signal processing technique that allows equidistant frequencies to be detected in broad-band oscillation spectra. This technique is based on analyzing the amplitude and phase correlation functions (APCF) of the oscillations. Equidistant frequencies can be detected in any broad-band spectrum based on the presence of periodic peaks related to such frequencies in APCF functions. An example of processing 1D resonator oscillations serves to show that the relationship between the eigenfrequencies in the spectrum and the APCF function peaks is similar to that between the optical grating slits and the interference line image on the screen. The proposed signal processing technique allows the difference between two adjacent frequencies of such a "grating" to be measured. The same analogy is true for a 2D resonator. In the latter case, two equidistant eigenfrequency gratings are shown to be present in the spectrum. Each grating corresponds to the eigenfrequencies of a 1D standing wave along each of the coordinates of a 2D resonator. The effect of small non-equidistance of the eigenfrequencies on the distortion and the location of the correlation function peaks is examined. The examples of processing two 1-h intervals of geomagnetic pulsation records are used to demonstrate the applicability of the APCF technique for real recorded magnetospheric oscillations.

      PubDate: 2016-12-07T12:12:48Z
      DOI: 10.1016/j.jastp.2016.11.007
      Issue No: Vol. 152-153 (2016)
  • Modeling of the middle atmosphere response to 27-day solar irradiance
    • Authors: Timofei Sukhodolov; Eugene Rozanov; William T. Ball; Thomas Peter; Werner Schmutz
      Pages: 50 - 61
      Abstract: Publication date: January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 152–153
      Author(s): Timofei Sukhodolov, Eugene Rozanov, William T. Ball, Thomas Peter, Werner Schmutz
      The solar rotational variability (27-day) signal in the Earth's middle atmosphere has been studied for several decades, as it was believed to help in the understanding of the Sun's influence on climate at longer timescales. However, all previous studies have found that this signal is very uncertain, likely due to the influence of the internal variability of the atmosphere. Here, we applied an ensemble modeling approach in order to decrease internal random variations in the modeled time series. Using a chemistry-climate model (CCM), SOCOLv3, we performed two 30-member 3-year long (2003–2005) ensemble runs: with and without a rotational component in input irradiance fluxes. We also performed similar simulations with a 1-D model, in order to demonstrate the system behavior in the absence of any dynamical feedbacks and internal perturbations. For the first time we show a clear connection between the solar rotation and the stratospheric tropical temperature time-series. We show tropical temperature and ozone signal phase lag patterns that are in agreement with those from a 1-D model. Pronounced correlation and signal phase lag patterns allow us to properly estimate ozone and temperature sensitivities to irradiance changes. While ozone sensitivity is found to be in agreement with recent sensitivities reported for the 11-year cycle, temperature sensitivity appears to be at the lowest boundary of previously reported values. Analysis of temperature reanalysis data, separate ensemble members, and modeling results without a rotational component reveals that the atmosphere can produce random internal variations with periods close to 27 days even without solar rotational forcing. These variations are likely related to tropospheric wave-forcing and complicate the extraction of the solar rotational signal from observational time-series of temperature and, to a lesser extent, of ozone. Possible ways of further improving solar rotational signal extraction are discussed.

      PubDate: 2016-12-14T14:09:21Z
      DOI: 10.1016/j.jastp.2016.12.004
      Issue No: Vol. 152-153 (2016)
  • Statistical cloud coverage as determined from sunshine duration: a model
           applicable in daylighting and solar energy forecasting
    • Authors: Ladislav Kómar; Miroslav Kocifaj
      Pages: 1 - 8
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Ladislav Kómar, Miroslav Kocifaj
      A radiative/luminous energy budget is difficult to predict on a daily or hourly base if cloud coverage is obtained by subjective methods in discrete time points. A simple theoretical model that overcomes this shortcoming through interrelation of absolute cloud fraction and sunshine duration is presented. The latter is measured routinely at the meteorological stations worldwide. The model is based on statistical probability of clear line of sight, where Poisson spatial cloud distribution is analyzed for three different cloud shapes. A validation of the model using long-term measurements show a good correlation between experimentally determined and theoretically predicted data. The absolute cloud fraction obtained this way are a base for daylighting and solar energy applications including simulations of luminance/radiance sky distributions under different meteorological conditions. A simple calculation tool is developed and demonstrated on global horizontal illuminance (GHI).

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.011
      Issue No: Vol. 150-151 (2016)
  • Characterization of aerosol events based on the column integrated optical
           aerosol properties and polarimetric measurements
    • Authors: Florian Mandija; Krzysztof Markowicz; Olga Zawadzka
      Pages: 9 - 20
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Florian Mandija, Krzysztof Markowicz, Olga Zawadzka
      Aerosol optical properties are very useful tools for analyzing their radiative effects, which are directly or indirectly related to the global radiation budget. Investigation of column-integrated aerosol optical properties is a worldwide and well-accepted method. The introduction of new methodologies, like those of operation with polarimetric measurements, represent a new challenge to interpret the measurement data and give more detailed information about the aerosol events and their characteristics. Aerosol optical properties during the period June – August 2015 in AERONET Strzyzow station in Poland were analyzed. The aerosol properties like aerosol optical depth, Ångström exponent, fine mode fraction, fine mode contribution on AOD, asymmetry parameter, single scattering angle are analyzed synergistically with the polarimetric measurements of the degree of polarization in different solar zenith and zenith viewing angles at several wavelengths. The overall results show that aerosol events in Strzyzow were characterized mostly by fine mode aerosols. Backward-trajectories suggest that the majority of air masses come from the west. The principal component of the aerosol load was urban/industrial contamination, especially from the inner part of the continent. Additionally, the maximal values of the degree of linear polarization were found to be dependent on the solar zenith and zenith viewing angles and aerosol optical properties like aerosol optical depth and Ångström exponent. These dependencies were further analyzed in a specific case with very high mean values of AOD500 (0.59) and AE440–870 (1.91). The diurnal variations of aerosol optical properties investigated during this special case, suggest that biomass burning products are the main cause of that aerosol load over the stations.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.012
      Issue No: Vol. 150-151 (2016)
  • A scanning Raman lidar for observing the spatio-temporal distribution of
           water vapor
    • Authors: Masanori Yabuki; Makoto Matsuda; Takuji Nakamura; Taiichi Hayashi; Toshitaka Tsuda
      Pages: 21 - 30
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Masanori Yabuki, Makoto Matsuda, Takuji Nakamura, Taiichi Hayashi, Toshitaka Tsuda
      We have constructed a scanning Raman lidar to observe the cross-sectional distribution of the water vapor mixing ratio and aerosols near the Earth's surface, which are difficult to observe when a conventional Raman lidar system is used. The Raman lidar is designed for a nighttime operating system by employing a ultra-violet (UV) laser source and can measure the water vapor mixing ratio at an altitude up to 7km using vertically pointing observations. The scanning mirror system consists of reflective flat mirrors and a rotational stage. By using a program-controlled rotational stage, a vertical scan can be operated with a speed of 1.5°/s. The beam was pointed at 33 angles over range of 0–48° for the elevation angle with a constant step width of 1.5°. The range-height cross sections of the water vapor and aerosol within a 400m range can be obtained for 25min. The lidar signals at each direction were individually smoothed with the moving average to spread proportionally with the distance from the laser-emitting point. The averaged range at a distance of 200m (400m) from the lidar was 30.0m (67.5m) along the lidar signal in a specific direction. The experimental observations using the scanning lidar were conducted at night in the Shigaraki MU radar observatory located on a plateau with undulating topography and surrounded by forests. The root mean square error (RMSE) between the temporal variations of the water vapor mixing ratio by the scanning Raman lidar and by an in-situ weather sensor equipped with a tethered balloon was 0.17g/kg at an altitude of 100m. In cross-sectional measurements taken at altitudes and horizontal distances up to 400m from the observatory, we found that the water vapor mixing ratio above and within the surface layer varied vertically and horizontally. The spatio-temporal variability of water vapor near the surface seemed to be sensitive to topographic variations as well as the wind field and the temperature gradient over the site. From the wide-range cross-sectional observations of the water vapor mixing ratio and the backscatter ratio of aerosols within a 2000m range, we can detect small-scale water vapor structures on a horizontal scale of several hundred meters in the atmospheric boundary layer.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.013
      Issue No: Vol. 150-151 (2016)
  • The solar dimming/brightening effect over the Mediterranean Basin in the
           period 1979–2012
    • Authors: H.D. Kambezidis; D.G. Kaskaoutis; G.K. Kalliampakos; A. Rashki; M. Wild
      Pages: 31 - 46
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): H.D. Kambezidis, D.G. Kaskaoutis, G.K. Kalliampakos, A. Rashki, M. Wild
      Numerous studies have shown that the solar radiation reaching the Earth's surface is subjected to multi-decadal variations with significant spatial and temporal heterogeneities in both magnitude and sign. Although several studies have examined the solar radiation trends over Europe, North America and Asia, the Mediterranean Basin has not been studied extensively. This work investigates the evolution and trends in the surface net short-wave radiation (NSWR, surface solar radiation - reflected) over the Mediterranean Basin during the period 1979–2012 using monthly re-analysis datasets from the Modern Era Retrospective-Analysis for Research and Applications (MERRA) and aims to shed light on the specific role of clouds on the NSWR trends. The solar dimming/brightening phenomenon is temporally and spatially analyzed over the Mediterranean Basin. The spatially-averaged NSWR over the whole Mediterranean Basin was found to increase in MERRA by +0.36Wm−2 per decade, with higher rates over the western Mediterranean (+0.82Wm−2 per decade), and especially during spring (March-April-May; +1.3Wm−2 per decade). However, statistically significant trends in NSWR either for all-sky or clean-sky conditions are observed only in May. The increasing trends in NSWR are mostly associated with decreasing ones in cloud optical depth (COD), especially for the low (<700hPa) clouds. The decreasing COD trends (less opaque clouds and/or decrease in absolute cloudiness) are more pronounced during spring, thus controlling the increasing tendency in NSWR. The NSWR trends for cloudless (clear) skies are influenced by changes in the water-vapor content or even variations in surface albedo to a lesser degree, whereas aerosols are temporally constant in MERRA. The slight negative trend (not statistically significant) in NSWR under clear skies for nearly all months and seasons implies a slight increasing trend in water vapor under a warming and more humid climatic scenario over the Mediterranean.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.006
      Issue No: Vol. 150-151 (2016)
  • Modelling the CO2 atmosphere-ocean flux in the upwelling zones using
           radiative transfer tools
    • Authors: Vladimir F. Krapivin; Costas A. Varotsos
      Pages: 47 - 54
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Vladimir F. Krapivin, Costas A. Varotsos
      An advanced mathematical model of the radiation forcing on the ocean surface is proposed for the assessment of the CO2 fluxes between atmosphere and ocean boundary in the upwelling zones. Two types of the upwelling are considered: coastal and local in the open ocean that are closely associated with changes in solar irradiance. The proposed model takes into account the maximal number of the carbon fluxes in the upwelling ecosystem considering that in the latter the only original source of energy and matter for all forms of life is the energy of the solar radiation. The vertical structure of the upwelling zone is represented by four levels: the upper mixed layer above the thermocline, the intermediate photic layer below the thermocline, the deep ocean and the near-bottom layer. Peruvian upwelling and typical local upwelling of tropical pelagic region are considered as examples for the model calculations.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.015
      Issue No: Vol. 150-151 (2016)
  • Point discharge current measurements beneath dust devils
    • Authors: Ralph D. Lorenz; Lynn D.V. Neakrase; John P. Anderson; R. Giles Harrison; Keri A. Nicoll
      Pages: 55 - 60
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Ralph D. Lorenz, Lynn D.V. Neakrase, John P. Anderson, R. Giles Harrison, Keri A. Nicoll
      We document for the first time observations of point discharge currents under dust devils using a novel compact sensor deployed in summer 2016 at the USDA-ARS Jornada Experimental Range in New Mexico, USA. A consistent signature is noted in about a dozen events seen over 40 days, with a positive current ramping up towards closest approach, switching to a decaying negative current as the devil recedes. The currents, induced on a small wire about 10cm above the ground, correlate with dust devil intensity (pressure drop) and dust loading, and reached several hundred picoAmps.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.017
      Issue No: Vol. 150-151 (2016)
  • Quantification of scaling exponents and dynamical complexity of microwave
           refractivity in a tropical climate
    • Authors: Ibiyinka A. Fuwape; Samuel T. Ogunjo
      Pages: 61 - 68
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Ibiyinka A. Fuwape, Samuel T. Ogunjo
      Radio refractivity index is used to quantify the effect of atmospheric parameters in communication systems. Scaling and dynamical complexities of radio refractivity across different climatic zones of Nigeria have been studied. Scaling property of the radio refractivity across Nigeria was estimated from the Hurst Exponent obtained using two different scaling methods namely: The Rescaled Range (R/S) and the detrended fluctuation analysis(DFA). The delay vector variance (DVV), Largest Lyapunov Exponent (λ 1) and Correlation Dimension (D 2) methods were used to investigate nonlinearity and the results confirm the presence of deterministic nonlinear profile in the radio refractivity time series. The recurrence quantification analysis (RQA) was used to quantify the degree of chaoticity in the radio refractivity across the different climatic zones. RQA was found to be a good measure for identifying unique fingerprint and signature of chaotic time series data. Microwave radio refractivity was found to be persistent and chaotic in all the study locations. The dynamics of radio refractivity increases in complexity and chaoticity from the Coastal region towards the Sahelian climate. The design, development and deployment of robust and reliable microwave communication link in the region will be greatly affected by the chaotic nature of radio refractivity in the region.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.010
      Issue No: Vol. 150-151 (2016)
  • Ball lightning passage through a glass without breaking it
    • Authors: Vladimir L. Bychkov; Anatoly I. Nikitin; Ilia P. Ivanenko; Tamara F. Nikitina; Alexander M. Velichko; Igor A. Nosikov
      Pages: 69 - 76
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Vladimir L. Bychkov, Anatoly I. Nikitin, Ilia P. Ivanenko, Tamara F. Nikitina, Alexander M. Velichko, Igor A. Nosikov
      In long history of ball lightning (BL) theory development there is a struggle of two concepts. According to the first one, BL – is a high frequency electrical discharge, burning in the air due to action of alternating electric field or a continuous current generated by an external source of energy. According to the second one, the BL is a material body, storing energy within itself. Data banks of BL observations give evidence that BL can pass through glasses, leaving no traces on them. Supporters of the first concept consider this as the proof of the correctness of the “electric field” BL nature. Representation of BL as a material body with internal source of energy explains most of its features, but has difficulties in explanation of BL penetration through glasses. We describe results of research of the glass, through which BL freely passed, that was observed by one of the authors. They proved the presence of traces left by BL. With a help of optical and scanning microscopes and laser beam probing of the glass, that experienced action of 20cm BL, we have found traces in it: in the glass we found a region of 1–2mm, at the center of which a cavity of 0.24mm diameter is located. This gives evidence to a “material” nature of BL. BL possibility to pass through small holes and its ability to “make” such holes poses a number of difficult issues to researchers indicated in the article.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.018
      Issue No: Vol. 150-151 (2016)
  • Mid-latitude mesospheric clouds and their environment from SOFIE
    • Authors: Mark E. Hervig; Michael Gerding; Michael H. Stevens; Robert Stockwell; Scott M. Bailey; James M. Russell; Gunter Stober
      Pages: 1 - 14
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Mark E. Hervig, Michael Gerding, Michael H. Stevens, Robert Stockwell, Scott M. Bailey, James M. Russell, Gunter Stober
      Observations from the Solar Occultation For Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite are used to examine noctilucent clouds (NLC) and their environment at middle latitudes (~56°N and ~52°S). Because SOFIE is uniquely capable of measuring NLC, water vapor, and temperature simultaneously, the local cloud environment can be specified to examine what controls their formation at mid-latitudes. Compared to higher latitudes, mid-latitude NLCs are less frequent and have lower ice mass density, by roughly a factor of five. Compared to higher latitudes at NLC heights, mid-latitude water vapor is only ~12% lower while temperatures are more than 10K higher. As a result the reduced NLC mass and frequency at mid-latitudes can be attributed primarily to temperature. Middle and high latitude NLCs contain a similar amount of meteoric smoke, which was not anticipated because smoke abundance increases towards the equator in summer. SOFIE indicates that mid-latitude NLCs may or may not be associated with supersaturation with respect to ice. It is speculated that this situation is due in part to SOFIE uncertainties related to the limb measurement geometry combined with the non-uniform nature of NLCs. SOFIE is compared with concurrent NLC, temperature, and wind observations from Kühlungsborn, Germany (54°N) during the 2015 summer. The results indicate good agreement in temperature and NLC occurrence frequency, backscatter, and height. SOFIE indicates that NLCs were less frequent over Europe during 2015 compared to other longitudes, in contrast to previous years at higher latitudes that showed no clear longitude dependence. Comparisons of SOFIE and the Solar Backscatter Ultraviolet (SBUV) indicate good agreement in average ice water column (IWC), although differences in occurrence frequency were often large.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.004
      Issue No: Vol. 149 (2016)
  • Dependency of rain integral parameters on specific rain drop sizes and its
           seasonal behaviour
    • Authors: Saurabh Das; Debaleena Ghosh
      Pages: 15 - 20
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Saurabh Das, Debaleena Ghosh
      This paper investigates the variability of raindrop size distribution (DSD) and rain integral parameters at Ahmedabad, a tropical location, in relation to the radar estimation of rainfall. Rain DSDs for the years 2006–2007 at Ahmedabad (23°04′N, 72°38′E) have been measured using a disdrometer. Variability of DSD is evaluated for different seasons and its effect on the integral rain parameters like radar reflectivity, rainfall intensity and attenuation are examined. A percentage contribution of different drop diameters on rain integral parameters is studied to understand the seasonal behaviour of rain attenuation and radar reflectivity. It is observed that drops with diameter around 3mm contribute maximum to the radar reflectivity while drops having a diameter around 2mm contribute the maximum to the rainfall intensity for the present location. The critical diameter range responsible for the maximum contribution in rain attenuation found to shift towards large drops with an increase in rain rate for a fixed frequency. Linear and non-linear regression analysis between radar reflectivity and rainfall intensity show significant variations in different seasons but does not differ much for different regression techniques. Results point to the necessity of considering the seasonal variability of rain DSD in radar remote sensing and will be helpful for better characterizing of rain parameters from radar measurements.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.003
      Issue No: Vol. 149 (2016)
  • Wavelet neural networks using particle swarm optimization training in
           modeling regional ionospheric total electron content
    • Authors: Mir Reza Ghaffari Razin; Behzad Voosoghi
      Pages: 21 - 30
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Mir Reza Ghaffari Razin, Behzad Voosoghi
      Wavelet neural networks (WNNs) are a new class of neural networks (NNs) that has been developed using a combined method of multi-layer artificial neural networks and wavelet analysis (WA). In this paper, WNNs is used for modeling and prediction of total electron content (TEC) of ionosphere with high spatial and temporal resolution. Generally, back-propagation (BP) algorithm is used to train the neural network. While this algorithm proves to be very effective and robust in training many types of network structures, it suffers from certain disadvantages such as easy entrapment in a local minimum and slow convergence. To improve the performance of WNN in training step, the adjustment of network weights using particle swarm optimization (PSO) was proposed. The results obtained in this paper were compared with standard NN (SNN) by BP training algorithm (SNN-BP), SNN by PSO training algorithm (SNN-PSO) and WNN by BP training algorithm (WNN-BP). For numerical experiments, observations collected at 36 GPS stations in 5 days of 2012 from Iranian permanent GPS network (IPGN) are used. The average minimum relative errors in 5 test stations for WNN-PSO, WNN-BP, SNN-BP and SNN-PSO compared with GPS TEC are 10.59%, 12.85%, 13.18%, 13.75% and average maximum relative errors are 14.70%, 17.30%, 18.53% and 20.83%, respectively. Comparison of diurnal predicted TEC values from the WNN-PSO, SNN-BP, SNN-PSO and WNN-BP models with GPS TEC revealed that the WNN-PSO provides more accurate predictions than the other methods in the test area.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.005
      Issue No: Vol. 149 (2016)
  • Multifractal detrended fluctuation analysis of ionospheric total electron
           content data during solar minimum and maximum
    • Authors: E. Chandrasekhar; Sanjana S. Prabhudesai; Gopi K. Seemala; Nayana Shenvi
      Pages: 31 - 39
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): E. Chandrasekhar, Sanjana S. Prabhudesai, Gopi K. Seemala, Nayana Shenvi
      The spatio-temporal variations in ionospheric vertical total electron content (TEC) data, which often reflect their scale invariant properties, can well be studied with multifractal analysis. We discuss the multifractal behaviour of TEC recorded at a total of 27 stations confined to a narrow longitude band (35°W-80°W) spanning from equator to high-latitude regions (30°S to 80°N) (geographic coordinates) during solar minimum (2008) and solar maximum (2014), using multifractal detrended fluctuation analysis (MFDFA). MFDFA provides an understanding of the multifractal scaling behaviour of a signal using the multifractal singularity spectra and the generalised Hurst exponents as diagnostic tools. The objectives of this study are to (i) understand the latitudinal dependence of the multifractal behaviour of TEC, (ii) compare the multifractal behaviour of TEC corresponding to the well-known 27-day variation (solar rotation period) and its harmonics and the 1-day (solar diurnal) periodicities, during 2008 and 2014 and (iii) understand the lunar tidal influence on TEC. Results indicate that except for the 1-day period, the TEC at all other periods shows a higher degree of multifractality during solar maximum compared to solar minimum. Further, irrespective of the solar activity, the degree of mutifractality in general decreases with increase in period for all latitude zones for periods of 27-day and its harmonics. However, the 1-day period exhibits monofractal behaviour regardless of the solar activity. The influence of semi-lunar tidal effects (having a periodicity of about 14.5 days) as a function of latitude is clearly seen in the 13.5-day periodicity (i.e., the 2nd harmonic of 27-day variation) of TEC. It manifests in the form of decreasing differences in the widths of the multifractal singularity spectra corresponding to the years 2008 and 2014, with increase in latitude. Results are discussed in the light of these observations.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.007
      Issue No: Vol. 149 (2016)
  • A temperature error correction method for a naturally ventilated radiation
    • Authors: Jie Yang; Qingquan Liu; Wei Dai; Rrenhui Ding
      Pages: 40 - 45
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Jie Yang, Qingquan Liu, Wei Dai, Rrenhui Ding
      Due to solar radiation exposure, air flowing inside a naturally ventilated radiation shield may produce a measurement error of 0.8°C or higher. To improve the air temperature observation accuracy, a temperature error correction method is proposed. The correction method is based on a Computational Fluid Dynamics (CFD) method and a Genetic Algorithm (GA) method. The CFD method is implemented to analyze and calculate the temperature errors of a naturally ventilated radiation shield under various environmental conditions. Then, a temperature error correction equation is obtained by fitting the CFD results using the GA method. To verify the performance of the correction equation, the naturally ventilated radiation shield and an aspirated temperature measurement platform are characterized in the same environment to conduct the intercomparison. The aspirated temperature measurement platform serves as an air temperature reference. The mean temperature error given by measurements is 0.36°C, and the mean temperature error given by correction equation is 0.34°C. This correction equation allows the temperature error to be reduced by approximately 95%. The mean absolute error (MAE) and the root mean square error (RMSE) between the temperature errors given by the correction equation and the temperature errors given by the measurements are 0.07°C and 0.08°C, respectively.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.010
      Issue No: Vol. 149 (2016)
  • Phase synchronization between tropospheric radio refractivity and rainfall
           amount in a tropical region
    • Authors: Ibiyinka A. Fuwape; Samuel T. Ogunjo; Joseph B. Dada; Gabriel A. Ashidi; Israel Emmanuel
      Pages: 46 - 51
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Ibiyinka A. Fuwape, Samuel T. Ogunjo, Joseph B. Dada, Gabriel A. Ashidi, Israel Emmanuel
      This study investigated linear and nonlinear relationship between the amount of rainfall and radio refractivity in a tropical country, Nigeria using forty seven locations scattered across the country. Correlation and Phase synchronization measures were used for the linear and nonlinear relationship respectively. Weak correlation and phase synchronization was observed between seasonal mean rainfall amount and radio refractivity while strong phase synchronization was found for the detrended data suggesting similar underlying dynamics between rainfall amount and radio refractivity. Causation between rainfall and radio refractivity in a tropical location was studied using Granger causality test. In most of the Southern locations, rainfall was found to Granger cause radio refractivity. Furthermore, it was observed that there is strong correlation between mean rainfall amount and the phase synchronization index over Nigeria. Coupling between rainfall and radio refractivity has been found to be due to water vapour in the atmosphere. Frequency planning and budgeting for microwave propagation during periods of high rainfall should take into consideration this nonlinear relationship.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.009
      Issue No: Vol. 149 (2016)
  • The association between space weather conditions and emergency hospital
           admissions for myocardial infarction during different stages of solar
    • Authors: J. Vencloviene; J. Antanaitiene; R. Babarskiene
      Pages: 52 - 58
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): J. Vencloviene, J. Antanaitiene, R. Babarskiene
      A number of studies have established the effects of space weather on the human cardio-vascular system. We investigated whether geomagnetic storms (GS), solar proton events (SPEs), and X-class solar flare affect the risk of emergency hospitalization for acute myocardial infarction (MI) separately during declining (2004–2006) and rising (2010–2012) phases of solar activity. The data on hospital admissions for MI were obtained from the computer database of Lithuanian University of Health sciences from January 1, 2004 to December 31, 2012. We evaluated the associations between space weather conditions and the daily number of emergency admissions for MI by Poisson regression, controlling for seasonal variation and weekdays. During 2004–2006, an increase in the risk of hospital admission for MI was observed on days of the daily mean proton >10MeV flux >100pfu (by 63%, p<0.001) and on days of GS concomitant with SPE, 1–2 days following these events, and on days of SPE occurring 1–2 days before GS concomitant with SPE (by 26%, p=0.019). During 2010–2012, an increase in the risk of hospital admission for MI was observed on days of the daily mean proton >10MeV flux >100pfu (by 52%, p=0.015) and on days of GS and 1–2 days after GS (by 17%, p=0.024). These findings suggest that the impact of hazardous space weather conditions on human health depends of the strength of space storm during the investigated period.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.012
      Issue No: Vol. 149 (2016)
  • Preliminary observations and simulation of nocturnal variations of airglow
           temperature and emission rates at Pune (18.5°N), India
    • Authors: S. Fadnavis; W. Feng; Gordon G. Shepherd; J.M.C. Plane; S. Sonbawne; Chaitri Roy; S. Dhomse; S.D. Ghude
      Pages: 59 - 68
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): S. Fadnavis, W. Feng, Gordon G. Shepherd, J.M.C. Plane, S. Sonbawne, Chaitri Roy, S. Dhomse, S.D. Ghude
      Preliminary observations of the nocturnal variations of the OH(6-2) and O2b(0-1) nighttime airglow in the mesosphere and lower thermosphere are investigated in the context of tidal influence for the tropical latitude station Pune (18.5°N, 73.85°E). This is the only tropical Spectral Airglow Temperature Imager (SATI) station where the tidal variations of mesosphere and lower thermosphere (MLT) temperature have been determined from ground based SATI observations. The SATI observations obtained since October 2012 reveal the influence of the migrating semidiurnal tides during solstice at this tropical station. There is variability in amplitude and phase obtained from SATI observations. In this paper, SATI observations on 10 Dec 2012 and 3 March 2013 are compared with Whole Atmosphere Community Climate Model (WACCM) simulations. The amplitude of semidiurnal tides is ~25K/30K on 10 Dec 2012 during solstice for OH/O2 temperature. During equinox SATI data indicates existence of semidiurnal tide also. The airglow observations are compared with simulations from the WACCM. The model underestimates the amplitude of the semi diurnal tide during equinox (1.6K/2.7K at 87km/96km) and solstice (~3.8K/4.8K at 87km/96km) for these days. The reason may be related to dampening of tides in the model due to the effect of strong latitudinal shear in zonal wind. The diurnal variation of airglow emission – which the model simulates well – is related to the vertical advection associated with the tides and downward mixing of atomic oxygen.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.002
      Issue No: Vol. 149 (2016)
  • Performance assessment of different day-of-the-year-based models for
           estimating global solar radiation - Case study: Egypt
    • Authors: Gasser E. Hassan; M. Elsayed Youssef; Mohamed A. Ali; Zahraa E. Mohamed; Ali I. Shehata
      Pages: 69 - 80
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Gasser E. Hassan, M. Elsayed Youssef, Mohamed A. Ali, Zahraa E. Mohamed, Ali I. Shehata
      Different models are introduced to predict the daily global solar radiation in different locations but there is no specific model based on the day of the year is proposed for many locations around the world. In this study, more than 20 years of measured data for daily global solar radiation on a horizontal surface are used to develop and validate seven models to estimate the daily global solar radiation by day of the year for ten cities around Egypt as a case study. Moreover, the generalization capability for the best models is examined all over the country. The regression analysis is employed to calculate the coefficients of different suggested models. The statistical indicators namely, RMSE, MABE, MAPE, r and R2 are calculated to evaluate the performance of the developed models. Based on the validation with the available data, the results show that the hybrid sine and cosine wave model and 4th order polynomial model have the best performance among other suggested models. Consequently, these two models coupled with suitable coefficients can be used for estimating the daily global solar radiation on a horizontal surface for each city, and also for all the locations around the studied region. It is believed that the established models in this work are applicable and significant for quick estimation for the average daily global solar radiation on a horizontal surface with higher accuracy. The values of global solar radiation generated by this approach can be utilized in the design and estimation of the performance of different solar applications.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.011
      Issue No: Vol. 149 (2016)
  • A study on the main periodicities in interplanetary magnetic field Bz
           component and geomagnetic AE index during HILDCAA events using wavelet
    • Authors: A.M. Souza; E. Echer; M.J.A. Bolzan; R. Hajra
      Pages: 81 - 86
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): A.M. Souza, E. Echer, M.J.A. Bolzan, R. Hajra
      The interplanetary and geomagnetic characteristics of High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events are studied using wavelet analysis technique. The Morlet wavelet transform was applied to the 1min interplanetary magnetic field (IMF) Bz component and the geomagnetic AE index during HILDCAA events. We have analyzed the AE data for the events occurring between 1975 and 2011, and the IMF Bz data (both in GSE and GSM) for the events between 1995 and 2011. We analyzed the scalograms and the global wavelet spectrum of the parameters. For 50% of all HILDCAA events, the main periodicities of the AE index are generally between 4 and 12h. For the Bz component, the main periodicities were found to be less than 8h for ~56% of times in GSM system and for ~54% of times in GSE system. It is conjectured that the periodicities might be associated with the Alfvén waves which have typical periods between 1 and 10h. The results are discussed in the light of self organized criticality theory where the physical events have the capacity of releasing a considerable amount of energy in a short interval of time.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.09.006
      Issue No: Vol. 149 (2016)
  • Balloon measurements of the vertical ionization profile over southern
           Israel and comparison to mid-latitude observations
    • Authors: Roy Yaniv; Yoav Yair; Colin Price; Keri Nicoll; Giles Harrison; Anton Artamonov; Ilya Usoskin
      Pages: 87 - 92
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Roy Yaniv, Yoav Yair, Colin Price, Keri Nicoll, Giles Harrison, Anton Artamonov, Ilya Usoskin
      Airborne measurements using meteorological balloons were conducted for the first time from southern Israel (geographic 30°35’N, 34°45’E geomagnetic 27°6’N 112°23’E) for measuring the vertical ionization profile during solar cycle 24. The results show the differences (increase of ~30%) in count rates as we proceed from solar maximum toward solar minimum. The observed altitude of maximum ionization (the Regener-Pfotzer maximum) was between 17–20km, and it agrees well with results from other simultaneous measurements conducted at different latitudes (Reading, UK and Zaragoza-Barcelona, Spain). When compared with predictions of an analytical model, we find a highly significant correlation (R2=0.97) between our observations and the computed ionization profiles. The difference in count rates can be attributed to the height of the tropopause due to the model using a US standard atmosphere that differs from the measured atmospheric parameters above Israel.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.003
      Issue No: Vol. 149 (2016)
  • Spatial and temporal variability of the atmospheric turbidity in Tunisia
    • Authors: Mohamed Saad; Amel Trabelsi; Mohamed Masmoudi; Stephane C. Alfaro
      Pages: 93 - 99
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Mohamed Saad, Amel Trabelsi, Mohamed Masmoudi, Stephane C. Alfaro
      Atmospheric turbidity is an important parameter in meteorology, climatology and for providing hindsight on particulate air pollution in local areas. In this work we exploit 1260 direct solar radiation measurements performed in Sfax (Center Tunisia), from March 2015 to February 2016. These measurements were made with a pyrheliometer only when clouds did not obstruct the solar disk. The atmospheric turbidity is quantified by the means of both the Linke's turbidity factor (T LI ) and Angström's coefficient (β). Over the year, values of T LI and β are found to vary in the ranges 1–15 and 0–0.7, with the most probable values around 3.5 and 0.05, respectively. However, a marked seasonal pattern is observed for the two turbidity parameters. They achieve their maximum in the spring and summer months, their minimum in winter and autumn appears as a transitional period. The comparison of the results obtained in Sfax with those of three AERONET stations located in north (Carthage), central-north (Ben Salem), and south (Medenine) Tunisia, reveals that this seasonal pattern of the atmospheric turbidity is valid for all the Tunisian territory, and probably beyond. At shorter (hourly) time scales, the diurnal behavior of the turbidity in Sfax is different in the summer months from the one observed during the rest of the year. Indeed, an enhancement of T LI is observed during the day. This is assumedly attributed to the production of secondary aerosols by atmospheric photochemistry.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.001
      Issue No: Vol. 149 (2016)
  • Temporal and spatial characteristics of lightning-produced nitrogen oxides
           in China
    • Authors: Guo Fengxia; Bao Min; Mu Yijun; Liu Zupei; Li Yawen; Shi Haifeng
      Pages: 100 - 107
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): Guo Fengxia, Bao Min, Mu Yijun, Liu Zupei, Li Yawen, Shi Haifeng
      Tropospheric NO2 vertical column densities (NO2VCDs) retrieved from the Global Ozone Monitoring Experiment-2 satellite spectrometer, as well as lightning flashes measured by an Optical Transient Detector and Lightning Image Sensor from 1997 to 2013 are used to investigate spatial and temporal characteristics of lightning-produced nitrogen oxides (LNOX) under the recent period of rapid and locally-unbalanced economic development in China. Correlations between spatial distributions of lightning flashes and monthly mean tropospheric NO2VCDs were analyzed over this period. Mean production of LNOX per flash is 330mol[N]/flash which was estimated using the correlation between lightning flashes and monthly mean tropospheric NO2VCD for the Tibetan Plateau. Using this correlation, the spatial and temporal characteristics of the ratio of LNOX to tropospheric NOX in China were determined. Results show that the ratio of LNOX to the tropospheric NOX is small in eastern regions, having a developed industrial sector and dense population, but relatively large in western regions, with a developing industrial sector and sparser population. The annual mean value of LNOX contributing to tropospheric NOX is 7.5% in China, which is lower than global averages (10–20%). The difference in interannual variability of LNOX production contributing to tropospheric NOX in different areas is distinct, ranging from high to low values for the Tibetan Plateau, Pearl River Delta, Yangtze River Delta and Beijing–Tianjin–Hebei regions, respectively. This indicates that lightning had a large influence on the column density of tropospheric NOX on the Tibetan Plateau, a region typically used as a sensitivity indicator for climate change. Lightning had less influence on atmospheric environments of the Pearl River Delta, Yangtze River Delta and Beijing–Tianjin–Hebei regions.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.007
      Issue No: Vol. 149 (2016)
  • Vertical winds and momentum fluxes due to equatorial planetary scale waves
           using all-sky meteor radar over Brazilian region
    • Authors: F. Egito; V.F. Andrioli; P.P. Batista
      Pages: 108 - 119
      Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149
      Author(s): F. Egito, V.F. Andrioli, P.P. Batista
      In the equatorial region planetary scale waves play an important role transporting significant amount of energy and momentum through atmosphere. Quantifying the momentum transported by these waves and its effects on the mean flow is rather important. Direct estimates of the momentum flux transported by waves require horizontal and vertical wind measurements. Ground-based meteor radars have provided continuous and reliable measurements of the horizontal wind components in the Mesosphere and Lower Thermosphere (MLT) region and have contributed to improve our knowledge of the dynamics of this region. However, instrumental limitations hinder its use for measuring vertical winds and momentum fluxes. On the other hand, according to Babu et al (2012), all- sky meteor radars are able to infer tridimensional winds when using a large number of meteor echoes centered at the meteor ablation peak. Following this approach, we have used measurements performed by a Meteor Radar installed at São João do Cariri, Brazil (7.4°S; 36.5°W) in order to measure vertical winds and calculate the momentum flux transported by equatorial planetary scale waves. In order to evaluate the accuracy of vertical wind values we have performed several tests based on a simple model considering real meteor distributions and theoretical equations for the MLT winds motion. From our tests, we inferred that Brazilian meteor radar data can be used for this purpose with an accuracy of ~ 1.8m/s. The results show that the vertical wind presents magnitudes of a few meters per second and occasionally reaches magnitudes around 10m/s. Below 92km the vertical wind is predominantly upward during the whole year and above exhibits a semi-annual oscillation with downward phase during the equinoxes. Variations associated to planetary scale waves in the vertical wind are also observed and some of them appear simultaneously in the zonal and meridional wind as well. Largest wave induced amplitudes in the vertical wind are found in the 3–4d band, reaching up to 4m/s. From the vertical and zonal wind measurements, we calculated the vertical transport of zonal momentum in the 3–4d band and found it to be maximum near autumn equinox, when its value reaches almost 20m2/s2, while minimum momentum flux is observed after the winter solstice.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.005
      Issue No: Vol. 149 (2016)
  • Assessment of scintillation proxy maps for a scintillation study during
           geomagnetically quiet and disturbed conditions over Uganda
    • Authors: Emirant B. Amabayo; Edward Jurua; Pierre J. Cilliers
      Abstract: Publication date: Available online 27 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Emirant B. Amabayo, Edward Jurua, Pierre J. Cilliers
      The objective of this paper is demonstrate the validity and usefulness of scintillation proxies derived from IGS data, through its comparison with data from dedicated scintillation monitors and its application to GNSS scintillation patterns. The paper presents scintillation patterns developed by using data from the dedicated scintillation monitors of the scintillation network decision aid (SCINDA) network, and proxy maps derived from IGS GPS data for 2011 and 2012 over low latitude stations in Uganda. The amplitude and phase scintillation indicies (S 4 and σ Φ ) were obtained from the Novatel GSV4004B ionospheric scintillation and total electron content (TEC) monitor managed by SCINDA at Makerere (0.340N, 32.570E). The corresponding IGS GPS proxy data were obtained from the receivers at Entebbe (0.040N, 32.440E) and Mbarara (0.600S, 30.740E). The derived amplitude (S 4p) and phase (sDPR) scintillation proxy maps were compared with maps of S 4 and σ Φ during geomagnetic storms (moderate and strong) and geomagnetically quiet conditions. The scintillation patterns using S 4 and σ Φ and their respective proxies revealed similar diurnal and seasonal patterns of strong scintillation occurrence. The peaks of scintillation occurrence with mean values in the range 0.3 < ( S 4 p , sDPR ) ≤ 0.6 were observed during nighttime (17:00–22:00 UT) and in the months of March-April and September-October. The results also indicate that high level scintillations occur during geomagnetically disturbed (moderate and strong) and quiet conditions over the Ugandan region. The results show that SCINDA and IGS based scintillation patterns reveal the same nighttime and seasonal occurrence of irregularities over Uganda irrespective of the geomagnetic conditions. Therefore, the amplitude and phase scintillation proxies presented here can be used to fill gaps in low-latitude data where there are no data available from dedicated scintillation receivers, irrespective of the geomagnetic conditions.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.009
  • Comparison of mesospheric winds from a high-altitude meteorological
           analysis system and meteor radar observations during the boreal winters of
           2009–2010 and 2012–2013
    • Authors: J. McCormack; K. Hoppel; D. Kuhl; R. de Wit; G. Stober; P. Espy; N. Baker; P. Brown; D. Fritts; C. Jacobi; D. Janches; N. Mitchell; B. Ruston; S. Swadley; K. Viner; T. Whitcomb; R. Hibbins
      Abstract: Publication date: Available online 24 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): J. McCormack, K. Hoppel, D. Kuhl, R. de Wit, G. Stober, P. Espy, N. Baker, P. Brown, D. Fritts, C. Jacobi, D. Janches, N. Mitchell, B. Ruston, S. Swadley, K. Viner, T. Whitcomb, R. Hibbins
      We present a study of horizontal winds in the mesosphere and lower thermosphere (MLT) during the boreal winters of 2009–2010 and 2012–2013 produced with a new high-altitude numerical weather prediction (NWP) system. This system is based on a modified version of the Navy Global Environmental Model (NAVGEM) with an extended vertical domain up to ∼116km altitude coupled with a hybrid four-dimensional variational (4DVAR) data assimilation system that assimilates both standard operational meteorological observations in the troposphere and satellite-based observations of temperature, ozone and water vapor in the stratosphere and mesosphere. NAVGEM-based MLT analyzed winds are validated using independent meteor radar wind observations from nine different sites ranging from 69°N–67°S latitude. Time-averaged NAVGEM zonal and meridional wind profiles between 75–95km altitude show good qualitative and quantitative agreement with corresponding meteor radar wind profiles. Wavelet analysis finds that the 3-hourly NAVGEM and 1-hourly radar winds both exhibit semi-diurnal, diurnal, and quasi-diurnal variations whose vertical profiles of amplitude and phase are also in good agreement. Wavelet analysis also reveals common time-frequency behavior in both NAVGEM and radar winds throughout the Northern extratropics around the times of major stratospheric sudden warmings (SSWs) in January 2010 and January 2013, with a reduction in semi-diurnal amplitudes beginning around the time of a mesospheric wind reversal at 60°N that precedes the SSW, followed by an amplification of semi-diurnal amplitudes that peaks 10–14 days following the onset of the mesospheric wind reversal. The initial results presented in this study demonstrate that the wind analyses produced by the high-altitude NAVGEM system accurately capture key features in the observed MLT winds during these two boreal winter periods.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.007
  • Ionospheric response to the 2006 sudden stratospheric warming event over
           the equatorial and low latitudes in the Brazilian sector using GPS
    • Authors: R. de Jesus; I.S. Batista; P.R. Fagundes; K. Venkatesh; A.J. de Abreu
      Abstract: Publication date: Available online 27 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R. de Jesus, I.S. Batista, P.R. Fagundes, K. Venkatesh, A.J. de Abreu
      The main purpose of this paper is to study the response of the ionospheric F-region using GPS-TEC measurements at equatorial and low latitude regions over the Brazilian sector during an sudden stratospheric warming (SSW) event in the year 2006. In this work, we present vertical total electron content (VTEC) and phase fluctuations derived from GPS network in Brazil. The continuous wavelet transform (CWT) was employed to check the periodicities of the ∆VTEC during the SSW event. The results show a strong decrease in VTEC and ∆VTEC values in the afternoon over low latitudes from DOY 05 to 39 (during the SSW event) mainly after the second SSW temperature peak. The ionospheric ∆VTEC pattern over Brazilian sector shows diurnal and semidiurnal oscillations during the 2006 SSW event. In addition, for the first time, variations in ∆VTEC (low latitude stations) with periods of about 02–08day have been reported during an SSW event. Using GPS stations located in the Brazilian sector, it is reported for the first time that equatorial ionospheric irregularities were not suppressed by the SSW event.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.005
  • Thermospheric density variations following the March 2013 geomagnetic
           storm from GRACE GPS-determined precise orbits
    • Authors: Andres Calabia; Shuanggen Jin
      Abstract: Publication date: Available online 28 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Andres Calabia, Shuanggen Jin
      The thermospheric mass density variations and thermosphere-ionosphere coupling during geomagnetic storms are not clear due to lack of observations and large uncertainty in the models. Although accelerometers on-board Low-Orbit-Earth (LEO) satellites can measure non-gravitational accelerations and derive thermospheric mass density variations with unprecedented details, their measurements are not always available. In order to cover accelerometer data gaps of GRACE, in this paper we estimate thermospheric mass densities from the GPS determined precise orbit ephemeris (POE) of GRACE satellites for the period 2011–2016. Our results show good correlation with accelerometer-based mass densities and a better estimation than the NRLMSISE00 empirical model. Furthermore, we statistically analyze the thermospheric density variations and responses to the March 2013 geomagnetic storm. The results show density variations with good correlations to the Dst, Kp and AE indices during the March 2013 geomagnetic storm. With the increasing resolution and accuracy of precise orbit determination (POD) products and LEO satellites, the straightforward technique of determining non-gravitational accelerations and thermospheric mass densities through numerical differentiation of POD promises potentially good applications for the upper atmosphere research.

      PubDate: 2016-12-28T15:04:05Z
  • The Role of Charged Ice Hydrometeors in Lightning Initiation
    • Authors: L.P. Babich; E.I. Bochkov; T. Neubert
      Abstract: Publication date: Available online 24 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): L.P. Babich, E.I. Bochkov, T. Neubert
      In connection with the lightning initiation problem, we consider positive streamer formation around charged, needle-shaped ice hydrometeors in an external electric field. We present results of numerical simulations of the streamer discharges that include the ice dielectric polarization and conductivity, and determine the external field intensity, at which stable streamer development is possible for different hydrometeor sizes and charge magnitudes. We find that the required charge is within the range of measured precipitation charges while the required external field is higher than observed in thunderclouds. We conclude, therefore, that a second mechanism for amplification of thundercloud fields is required for the streamer inception.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.010
    • Authors: Laysa Cristina Araujo Resende; Inez Staciarini Batista; Clezio Marcos Denardini; Paulo Prado Batista; Alexander José Carrasco; Vânia de Fátima Andrioli; Juliano Moro
      Abstract: Publication date: Available online 26 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Laysa Cristina Araujo Resende, Inez Staciarini Batista, Clezio Marcos Denardini, Paulo Prado Batista, Alexander José Carrasco, Vânia de Fátima Andrioli, Juliano Moro
      This work presents new results about simulations of blanketing sporadic E-layers, Esb, using a modified version of a theoretical model for the E region (MIRE) for a Brazilian region: Cachoeira Paulista, a low latitude station. MIRE computes the densities of the metallic ions (Fe+ and Mg+) and of the main molecular ions (NO+, O2 +, N2 +) by solving the continuity and momentum equations for each one of them. Additionally, this model includes the physics of Es layer development driven by tidal winds. In this study, we extend MIRE adding a novel neutral wind model derived from the all-sky meteor radar measurements, which provides more trustworthy results related to the Es layer formation in the Brazilian sector. Afterwards, this new model is validated comparing the computed electron density for the Es layer with the electron density obtained using the blanketing frequency parameter (fbEs) deduced from ionograms in the analyzed region. The results show that the values computed by the extended MIRE are in good agreement with the observational data for the Es layers formed by the wind shear mechanism. Therefore, the extended MIRE presented in this work is the only available model that allows simulating Esb layers with a much higher confidence level for the low-latitude in the Brazilian sector.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.012
    • Authors: R.G. Ezquer; L.A. Scidá; Y.O. Migoya Orué; G.E. Lescano; K. Alazo-Cuartas; M.A. Cabrera; S.M. Radicella
      Abstract: Publication date: Available online 27 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R.G. Ezquer, L.A. Scidá, Y.O. Migoya Orué, G.E. Lescano, K. Alazo-Cuartas, M.A. Cabrera, S.M. Radicella
      The performance of NeQuick 2 model in computing the vertical total electron content (VTEC) over a wide region placed at middle latitudes of North America during the deep solar minimum that occurred in 2008 has been checked. The long term relationship between EUV irradiance and F10.7 solar flux has changed markedly during the cycle 23/24 minimum with EUV levels decreasing more than expected from F10.7 proxy. A decrease of ionization in the ionosphere could have occurred. Thus, it could be expected that the models overestimate the value of ionospheric parameters for that deep solar minimum. For this study a high density VTEC data grid that covers the Continental United States (CONUS) has been compared with monthly median maps constructed with NeQuick 2. The results show that NeQuick 2 generally gives good predictions for the region which lies between 35°N to 50°N suggesting that nothing exceptional was happening during the 2008 minimum in terms of VTEC NeQuick 2's predictive capabilities. Taking into account that the modelled value is obtained by integration in height of the electron density profile, NeQuick2 would be assuming an inadequate profile for the few highest deviations observed, between 30°N and 35°N. Overall, the model does not give significant overestimation of VTEC as could be expected.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.014
  • An Overturning-like Thermospheric Na Layer and its Relevance to
           Ionospheric Field Aligned Irregularity and Sporadic E
    • Authors: Xianghui Xue; Guozhu Li; Xiankang Dou; Xinan Yue; Guotao Yang; Jinsong Chen; Tingdi Chen; Baiqi Ning; Jihong Wang; Guojun Wang; Weixing Wan
      Abstract: Publication date: Available online 19 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Xianghui Xue, Guozhu Li, Xiankang Dou, Xinan Yue, Guotao Yang, Jinsong Chen, Tingdi Chen, Baiqi Ning, Jihong Wang, Guojun Wang, Weixing Wan
      We report an overturning-like structure of the thermospheric sodium layer (TSL) in the altitude region of ∼100–120km observed by a sodium lidar at Haikou (20.0°N), China, on July 29, 2012. The overturning-like sodium layer was first seen as upwelling from the top of the sodium layer (∼102km) to an altitude of ∼118km from 14:55–15:50 UT and then descending gradually from its apex with a speed of 3.5km/hr. The ionospheric observations from the COSMIC radio occultation and three ionosondes exhibited abrupt perturbations in the radio occultation (RO) SNR profiles and spread Es in the ionograms, respectively, indicating the existence of complex Es around Haikou. On the other hand, VHF radars located at Sanya (18.4°N, 220km away from Haikou) and Fuke (19.5°N, 130km away from Haikou) both recorded strong E region field-aligned irregularity (FAI) echoes altitude-extended structure covering altitudes of 100–140km, which are well correlated with the overturning-like structure of the thermospheric sodium layer. The good agreement between occurrence time of sodium layer (and FAI) structure and of complex Es could indicate a close correlation between them. One possibility is that the chemical reaction in the course of the complex Es (with altitude-deformed structure) could produce sufficient sodium atoms and thus lead to the formation of sodium layer upwelling structure. Correspondingly, FAI altitude-extended structure could be generated through the gradient drift instability in the altitude-extend (deformed) Es which provide plasma density gradients to support the instability development.

      PubDate: 2016-12-21T14:33:31Z
      DOI: 10.1016/j.jastp.2016.12.006
  • IFC-Ed. board
    • Abstract: Publication date: January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 152–153

      PubDate: 2016-12-21T14:33:31Z
  • Case study of convective instability observed in airglow images over the
           Northeast of Brazil
    • Authors: A.J.A. Carvalho; I. Paulino; A.F. Medeiros; L.M. Lima; R.A. Buriti; A.R. Paulino; C.M. Wrasse; H. Takahashi
      Abstract: Publication date: Available online 21 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.J.A. Carvalho, I. Paulino, A.F. Medeiros, L.M. Lima, R.A. Buriti, A.R. Paulino, C.M. Wrasse, H. Takahashi
      An intense activity of ripples during the nighttime was observed in airglow images over São João do Cariri (36.5 o W, 7.4 o S) on 10 October 2004 which lasted for two hours. Those ripples appeared simultaneously with the crossing of a mesospheric front and medium scale gravity waves. The ripples occurred ahead of the mesospheric front and their phase front were almost parallel to the phase of the mesospheric front and were almost perpendicular to the phase front of the gravity wave. Using wind measurements from a meteor radar located at São João do Cariri and simultaneous vertical temperature profiles from the TIMED/SABER satellite, on the night of the events and within the imager field of view, the atmospheric background environment in the mesosphere and lower thermosphere (MLT) was investigated in order to understand the instability process that caused the appearance of the ripples. Dynamic and convective instabilities have been pointed out as responsible for creation of ripples in the MLT. The observed ripples were advected by the neutral wind, they occurred into a region with negative lapse rate of the potential temperature and the Richardson number was negative as well. According to these characteristics, the ripple structures could be generated in the MLT region due to the predominance of convective instability.

      PubDate: 2016-12-21T14:33:31Z
      DOI: 10.1016/j.jastp.2016.12.003
  • Use of multivariate relevance vector machines in forecasting multiple
           geomagnetic indices
    • Authors: T. Andriyas; S. Andriyas
      Abstract: Publication date: Available online 11 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): T. Andriyas, S. Andriyas
      The forecasting ability of Multivariate Relevance Vector Machines (MVRVM), used previously to generate forecasts for the Dst index, is extended to forecast the Dst, AL, and PC indices during the years 1975–2007. Such learning machines are used in forecasting because of their robustness, efficiency, and sparseness. The MVRVM model was trained on solar wind and geomagnetic activity data sampled every hour with activity periods of various intensities, durations, and features. It was found that during the training phase, for a given error threshold, 14.60% of the training data was needed to explain the features of the data. The trained model was then tested on 177 different storm intervals, at various levels of geomagnetic activity, to generate simultaneous forecasts of the three indices at a lead time of one hour (1-h). The focus of the modeling was to assess the forecasts during main storm (MS) time periods when the indices show enhanced activity above quiet time values. The forecasts obtained by the MVRVM model reported in this paper returned a MS time average prediction efficiency, PE ¯ of 82.42%, 84.40%, and 76.00% and RMSE ¯ of 13.70nT, 97.00nT, and −0.77mV/m, for the Dst, AL, and PC indices, respectively. The qualitative numbers indicated that the model underestimated the peak amplitude of the indices during the geomagnetic activity, but the peaks were forecasted on time by the model, on average. The forecasting results indicate a robust model generalization and the MVRVM's ability to learn the input-output relationship through a sparse model framework. A qualitative comparison with the previous univariate RVM forecast of Dst indicates that the model goodness of fit numbers improved in the present study.

      PubDate: 2016-12-14T14:09:21Z
      DOI: 10.1016/j.jastp.2016.11.002
  • Source spectra of the gravity waves obtained from momentum flux and
           kinetic energy over Indian region: Comparison between observations and
           model results
    • Authors: M. Pramitha; M. Venkat Ratnam; B.V. Krishna Murthy; S. Vijaya Bhaskar Rao
      Abstract: Publication date: Available online 3 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M. Pramitha, M. Venkat Ratnam, B.V. Krishna Murthy, S. Vijaya Bhaskar Rao
      Using 8 years (May 2006 to March 2014) of high resolution and high accuracy GPS radiosonde observations available from a tropical station Gadanki (13.5°N, 79.2°E), India, we have investigated the climatology of gravity wave energy and zonal momentum fluxes in the lower stratosphere. We also obtained best fit spectrum model for the gravity waves (GWs) for this tropical station. In general, strong annual variation in the energy and momentum flux with maximum during Indian summer monsoon is observed in the lower stratospheric region (18–25km). By considering different source spectra, we have applied Gravitywave Regional or Global RAy Tracer (GROGRAT) model run on monthly basis using the source spectrum values at different altitudes on the ERA-Interim background fields to obtain the kinetic energy and zonal momentum fluxes for each of the spectra considered. These simulated fluxes are compared with the observed fluxes to arrive at the best fit spectrum model. It is found that the spectrum which represents the convection transient mountain mechanism that is purely anti-symmetric and anisotropic in nature is the best fit model for Gadanki location. This information would be useful in parameterization of the GWs in numerical models over Indian region.

      PubDate: 2016-12-07T12:12:48Z
      DOI: 10.1016/j.jastp.2016.12.001
  • Prediction of global solar radiation and comparison with satellite data
    • Authors: Kadir Bakirci
      Abstract: Publication date: Available online 5 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Kadir Bakirci
      Data on solar radiation at a related location is very necessary for many solar applications. In the present study, the models are derived to forecast the daily global solar radiation on horizontal plane for the Eastern Anatolia Region (EAR) of Turkey, covering thirteen provinces. The measured data on horizontal plane for the period of 1991–2005 are analyzed. The comparisons of calculated and measured values have been carried out with various statistical test methods. These statistical test methods are the mean bias error (MBE), the main percentage error (MPE), the root mean square error (RMSE) and t-statistic (t-stat). In addition, the comparisons of the solar radiation values of the National Aeronautics and Space Administration - Surface meteorology and Solar Energy (NASA-SSE) and calculated from the Model 3 with the higher determination coefficient is performed.

      PubDate: 2016-12-07T12:12:48Z
  • High-Resolution Observations and Modeling of Turbulence Sources,
           Structures, and Intensities in the Upper Mesosphere
    • Authors: David C. Fritts; Ling Wang; Gerd Baumgarten; Amber D. Miller; Marvin A. Geller; Glenn Jones; Michele Limon; Daniel Chapman; Joy Didier; Carl B. Kjellstrand; Derek Araujo; Seth Hillbrand; Andrei Korotkov; Gregory Tucker; Jerry Vinokurov
      Abstract: Publication date: Available online 24 November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): David C. Fritts, Ling Wang, Gerd Baumgarten, Amber D. Miller, Marvin A. Geller, Glenn Jones, Michele Limon, Daniel Chapman, Joy Didier, Carl B. Kjellstrand, Derek Araujo, Seth Hillbrand, Andrei Korotkov, Gregory Tucker, Jerry Vinokurov
      New capabilities for imaging small-scale instabilities and turbulence and for modeling gravity wave (GW), instability, and turbulence dynamics at high Reynolds numbers are employed to identify the major instabilities and quantify turbulence intensities near the summer mesopause. High-resolution imaging of polar mesospheric clouds (PMCs) reveal a range of instability dynamics and turbulence sources that have their roots in multi-scale GW dynamics at larger spatial scales. Direct numerical simulations (DNS) of these dynamics exhibit a range of instability types that closely resemble instabilities and turbulence seen in PMC imaging and by ground-based and in-situ instruments at all times and altitudes. The DNS also exhibit the development of “sheet-and-layer” (S&L) structures in the horizontal wind and thermal stability fields that resemble observed flows near the mesopause and at lower altitudes. Both observations and modeling suggest major roles for GW breaking, Kelvin-Helmholtz instabilities (KHI), and intrusions in turbulence generation and energy dissipation. Of these, larger-scale GW breaking and KHI play the major roles in energetic flows leading to strong turbulence. GW propagation and breaking can span several S&L features and induce KHI ranging from GW to turbulence scales. Intrusions make comparable contributions to turbulence generation as instabilities become weaker and more intermittent. Turbulence intensities are highly variable in the vertical and typically span 3 or more decades. DNS results that closely resemble observed flows suggest a range of mechanical energy dissipation rates of ε ~10-3-10 Wkg-1 that is consistent with the range of in-situ measurements at ~80–90km in summer.

      PubDate: 2016-11-30T09:27:24Z
      DOI: 10.1016/j.jastp.2016.11.006
  • IFC-Ed. board
    • Abstract: Publication date: November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 149

      PubDate: 2016-11-23T06:38:05Z
  • Spatiotemporal assessment of CO2 emissions and its satellite remote
           sensing over Pakistan and neighboring regions
    • Authors: Zia ul-Haq; Salman Tariq; Muhammad Ali
      Abstract: Publication date: Available online 9 November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Zia ul-Haq, Salman Tariq, Muhammad Ali
      For the first time, anthropogenic CO2 emissions and spatiotemporal variability of mid-tropospheric CO2 has been discussed using EDGAR database and Atmospheric Infrared Sounder (AIRS) onboard Aqua satellite observations. The EDGAR data indicate an increase of 147% in anthropogenic CO2 emissions from 66101 to 163737 Gg for Pakistan during the period of 1990−2008. Dera Ghazi Khan (Pakistan) is found with the highest increase of 260% of anthropogenic CO2 emissions followed by Delhi (India) 153%, Karachi (Pakistan) 66% and Lahore (Pakistan) 59% whereas a decreasing trend of −53% is observed for Kabul (Afghanistan) during 1990−2008. Industrial activities, road transportation, open field crop-waste burning, and energy production have been identified as major anthropogenic emission sources of CO2 in the studied region. AIRS CO2 retrievals over Pakistan and adjoining areas of India and Afghanistan show an averaged CO2 to be 383±5 ppm with a positive trend of 5.05% during December 2002 to February 2012. An elevated value of CO2 has been observed over northern mountainous and high human settlement regions. The seasonal analysis shows a spring maximum 385±5 ppm with a secondary peak in late autumn, and the highest increasing trend of 5.5% associated with winter. May and August showed maximum and minimum mean monthly values of 385±5 ppm and 382±5 ppm respectively. HYSPLIT trajectories of air masses movement have been drawn to track CO2 transport.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.11.001
  • Sensitivity of equatorial atomic oxygen in the MLT region to the 11-year
           and 27-day solar cycles
    • Authors: Olexandr Lednyts'kyy; Christian von Savigny; Mark Weber
      Abstract: Publication date: Available online 19 November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Olexandr Lednyts'kyy, Christian von Savigny, Mark Weber
      We report on 27-day and 11-year solar cycle signatures in atomic oxygen (O) concentrations ([O]) in the MLT (Mesosphere/Lower Thermosphere) region of the terrestrial atmosphere. MLT [O] profiles were retrieved on the base of green line (557.7nm) nightglow data sets provided by the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard Envisat from 2002 to 2012. A statistically significant solar 27-day signature was identified (and then quantified with respect to the sensitivity and phase relationship to solar forcing) in time series of MLT [O] profiles with use of cross-correlation and superposed epoch analysis techniques. It was the first identification of the solar 27-day signature in MLT atomic oxygen on the base of such experimental data sets. The sensitivity of [O] to solar cycle variability at the 11-year time scale was quantified with use of cross-correlation and multiple-linear regression analysis techniques, which yield results consistent with known studies and, particularly, indicate that the sensitivity of [O] to solar forcing increases with increasing altitude. A comparison of obtained values of atomic oxygen sensitivity in response to solar forcing at the 27-day and 11-year time scales reveals the fact that the sensitivities agree well to each other within their uncertainties during the descending phase of the last (23rd) 11-year cycle of solar activity, whereas the [O] sensitivity values at the 27-day time scale during the last solar minimum phase were lower than those ones during the descending phase. It was also determined that atomic oxygen is in-phase with the solar forcing (in agreement with model results) at the 11-year time scale, whereas the time lag of the 27-day signature in response to solar forcing was about 12 – 14 days.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.11.003
  • Seasonal, inter-annual and solar cycle variability of the quasi two day
           wave in the low-latitude mesosphere and lower thermosphere
    • Authors: N. Venkateswara Rao; M. Venkat Ratnam; C. Vedavathi; T. Tsuda; B.V. Krishna Murthy; S. Sathishkumar; S. Gurubaran; K. Kishore Kumar; K.V. Subrahmanyam; S. Vijaya Bhaskara Rao
      Abstract: Publication date: Available online 22 November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): N. Venkateswara Rao, M. Venkat Ratnam, C. Vedavathi, T. Tsuda, B.V. Krishna Murthy, S. Sathishkumar, S. Gurubaran, K. Kishore Kumar, K.V. Subrahmanyam, S. Vijaya Bhaskara Rao
      We analyzed 17 years (1993–2009) of horizontal winds measured by the medium frequency (MF) radar located at Tirunelveli (8.7°N, 77.8°E) and 10 years (2005–2014) of horizontal winds measured by a meteor radar located at Thumba (8.5°N, 77°E) to examine the seasonal, inter-annual, and solar cycle variability of the Quasi-Two Day Wave (QTDW) in the mesosphere and lower thermosphere region. These two radars are nearly co-located, but differ in their measurement technique. Comparison of the estimated QTDW amplitudes by the two radars shows that the amplitudes are larger in the meteor radar than those in the MF radar. The difference between the amplitudes is larger in May in the zonal component and in April and September in the meridional one. Furthermore, the differences are larger in the meridional component. The QTDWs in both the radars show a strong semi-annual oscillation (SAO). In addition, the meridional QTDW amplitudes of both the MF and meteor radars show a distinct enhancement in the month of October. While the whole spectra of QTDWs contribute to the SAO amplitudes, only 45–50 h waves contribute to the October enhancement. The amplitudes of the QTDWs, in general, show large inter-annual variability. The QTDW amplitudes from both the radars show modulation at period of quasi-biennial oscillation. The QTDWs of the MF radar show a small negative correlation with solar activity while those of meteor radar do not show any correlation. The above aspects are discussed in the light of current understanding of the QTDWs.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.11.005
  • IFC-Ed. board
    • Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151

      PubDate: 2016-11-23T06:38:05Z
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