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  Subjects -> METEOROLOGY (Total: 90 journals)
Showing 1 - 36 of 36 Journals sorted alphabetically
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 34)
Advances in Climate Change Research     Open Access   (Followers: 10)
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: 15)
American Journal of Climate Change     Open Access   (Followers: 15)
Atmósfera     Open Access   (Followers: 2)
Atmosphere     Open Access   (Followers: 21)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 12)
Atmospheric and Oceanic Science Letters     Open Access   (Followers: 2)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 29)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 11)
Atmospheric Research     Hybrid Journal   (Followers: 54)
Atmospheric Science Letters     Open Access   (Followers: 29)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 22)
Bulletin of the American Meteorological Society     Open Access   (Followers: 33)
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: 4)
Climate Dynamics     Hybrid Journal   (Followers: 29)
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: 16)
Dynamics and Statistics of the Climate System     Open Access   (Followers: 2)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 11)
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: 14)
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: 31)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 131)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 20)
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: 6)
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: 20)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 68)
Journal of the Meteorological Society of Japan     Partially Free   (Followers: 2)
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: 26)
Nature Climate Change     Full-text available via subscription   (Followers: 62)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 28)
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: 23)
Tellus B     Open Access   (Followers: 21)
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: 22)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 7)
Urban Climate     Hybrid Journal  
Weather     Hybrid Journal   (Followers: 13)
Weather and Climate Extremes     Open Access   (Followers: 8)
Weather and Forecasting     Full-text available via subscription   (Followers: 15)
Weatherwise     Hybrid Journal   (Followers: 2)
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]   [131 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [3041 journals]
  • Excitation mechanism of non-migrating tides
    • Authors: Yasunobu Miyoshi; Dora Pancheva; Plamen Mukhtarov; Hidekatsu Jin; Hitoshi Fujiwara; Hiroyuki Shinagawa
      Pages: 24 - 36
      Abstract: Publication date: April 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 156
      Author(s): Yasunobu Miyoshi, Dora Pancheva, Plamen Mukhtarov, Hidekatsu Jin, Hitoshi Fujiwara, Hiroyuki Shinagawa
      Using an atmosphere-ionosphere coupled model, the excitation source and temporal (seasonal and interannual) variations in non-migrating tides are investigated in this study. We first focus our attention on temporal variations in eastward moving diurnal tide with zonal wavenumber 3 (DE3), which is the largest of all the non-migrating tides in the mesosphere and lower thermosphere (MLT). Our simulation results indicate that upward propagation of the DE3 excited in the troposphere is sensitive to the zonal mean zonal wind in the stratosphere and mesosphere. The DE3 amplitude is enhanced in the region where the vertical shear of the zonal mean zonal wind is positive (westerly shear). Quasi-2-year variation in the DE3 amplitude in the MLT region is generated by quasi-2-year variation in the zonal mean zonal wind between 40 and 70km, which is modulated by the stratospheric QBO. The excitation mechanisms of SW3 (westward moving semidiurnal tide with zonal wavenumber 3) and SW1 (westward moving semidiurnal tide with zonal wavenumber 1) are also investigated. During equinoxes, the SW3 and SW1 are excited by tropospheric heating (latent heat release and solar radiative heating) associated with cumulus convection in the tropics, and propagate upward into the MLT region. On the other hand, during solstices, SW3 and SW1 are generated in the winter stratosphere and mesosphere through the nonlinear interaction between the stationary planetary wave and migrating semidiurnal tide, and propagate upward to the lower thermosphere. The excitation sources of other non-migrating tides are also discussed.

      PubDate: 2017-03-02T13:00:13Z
      DOI: 10.1016/j.jastp.2017.02.012
      Issue No: Vol. 156 (2017)
       
  • Terrestrial gamma-ray flashes in the BeppoSAX data archive
    • Authors: A. Ursi; C. Guidorzi; M. Marisaldi; D. Sarria; F. Frontera
      Pages: 50 - 56
      Abstract: Publication date: April 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 156
      Author(s): A. Ursi, C. Guidorzi, M. Marisaldi, D. Sarria, F. Frontera
      Up to now, Terrestrial Gamma-ray Flashes (TGFs) have been mostly observed by instruments on-board satellites devoted to astrophysics: after the discovery by the BATSE/CGRO experiment in the early 90's, this elusive phenomenon has been further detected by RHESSI, by the AGILE satellite and by the Fermi space telescope. The Italian/Dutch satellite BeppoSAX (1996–2002) was one of the most important high-energy astrophysics missions, especially for what concerns the field of Gamma-Ray Bursts (GRBs). Its payload housed the Gamma-Ray Burst Monitor (GRBM), a segmented detector that could, in principle, have observed TGFs as well. Motivated by this possibility, we carried out, for the first time, a systematic search for TGFs in the BeppoSAX data archive, ending up with a sample of 12 TGF candidates. Among them, we also found a peculiar event, whose light curve characteristics may represent the signature of a mirrored Terrestrial Electron Beam (TEB).

      PubDate: 2017-03-08T13:15:44Z
      DOI: 10.1016/j.jastp.2017.02.014
      Issue No: Vol. 156 (2017)
       
  • THE EFFECT OF SEASONALITY AND STATIONARITY ON SPECIFIC HUMIDITY FORECAST
           OVER NIGERIA
    • Authors: B. Adeyemi; M.I. Akerele
      Pages: 57 - 71
      Abstract: Publication date: Available online 3 March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): B. Adeyemi, M.I. Akerele
      This paper investigates the importance of seasonality and stationarity of climatological data to effective forecast of a meteorological parameter – the specific humidity, ‘q’. This was done by computing q using monthly datasets of temperature and relative humidity from twenty carefully selected stations for twenty-six (26) years (1970–1995). The data were retrieved from the archives of the Nigerian Meteorological Agencies. The data were analysed to examine its seasonality as well as stationarity which are considered to be the basic requirements for good and accurate forecasting in climate studies. The stations were grouped into four climatic regions namely: the Sahel, Guinea Savanna, Rainforest and Derived Savanna regions. It was found that stations from the Guinea Savanna and Sahelian regions show more seasonality and stationarity compared to stations in Rainforest and Derived Savanna regions. Forecast was then carried out using three techniques which are: the ordinary Autoregressive model, Harmonic Analysis and Exponential Smoothing modelling techniques. These were analysed and evaluated using series of statistical error analysis methods. Exponential smoothing technique, which incorporates the seasonal components of the data into its model, was found to give the most accurate and reliable results with minimal statistical errors, re-iterating the importance of seasonality and stationarity in effective climate forecast.

      PubDate: 2017-03-08T13:15:44Z
      DOI: 10.1016/j.jastp.2017.03.001
      Issue No: Vol. 156 (2017)
       
  • “Long-hissler” fine structure within auroral hiss: A review
           and synthesis
    • Authors: Howard F. Kim; James LaBelle; Maria Spasojević
      Pages: 72 - 79
      Abstract: Publication date: April 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 156
      Author(s): Howard F. Kim, James LaBelle, Maria Spasojević
      One of the most prominent fine-structures of auroral hiss is the “long-hissler”, defined here as a dispersed feature embedded within broadband auroral hiss emissions in the frequency range 1–40kHz and lasting longer than 0.3s. While theory is limited, there is evidence that hisslers can be used in remote sensing of density characteristics at altitudes of thousands of km. By applying an automatic threshold algorithm to VLF data collected at South Pole 2230–0130 UT daily during June–August 2014, 22h of auroral hiss are identified on 49 of 93 days analyzed, for an occurrence rate of 9.7% during the applicable MLT interval. From manual inspection of these intervals, 414 groups (trains) of long hisslers are identified on 34 of the 49 days on which hiss occurred. Median lower (upper) frequency bounds of these features are 8 (22)kHz, median frequency–time slope is −10kHz/s, and median hissler repetition time within a train (hissler period) is 1.2s. Hissler period and frequency–time slope are inversely related. Data from previous studies are reviewed to provide a comprehensive description of the phenomenon. Contrary to some previous studies, subsequent long hissler features are found to commonly overlap in time, and no evidence is found for an inverse relationship between hissler train duration and geomagnetic activity.

      PubDate: 2017-03-16T13:57:21Z
      DOI: 10.1016/j.jastp.2017.03.002
      Issue No: Vol. 156 (2017)
       
  • On the relationship between the QBO/ENSO and atmospheric temperature using
           COSMIC radio occultation data
    • Authors: Pan Gao; Xiaohua Xu; Xiaohong Zhang
      Pages: 103 - 110
      Abstract: Publication date: April 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 156
      Author(s): Pan Gao, Xiaohua Xu, Xiaohong Zhang
      In this paper, the spatial patterns and vertical structure of atmospheric temperature anomalies, in both the tropics and the extratropical latitudes, associated with the El Niño-Southern Oscillation (ENSO) and quasi-biennial oscillation (QBO) in the upper troposphere and stratosphere are investigated using global positioning system (GPS) radio occultation (RO) measurements from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Formosa Satellite Mission 3 mission from July 2006 to February 2014. We find that negative correlations between the atmospheric temperature in the tropics and ENSO are observed at 17–30km in the lower stratosphere at a lag of 1–4 months and at a lead of 1 month. Out-of-phase temperature variation is observed in the troposphere over the mid-latitude band and in-phase behaviour is observed in the lower stratosphere. Interestingly, we also find that there is a significant negative correlation at a lag of 1–3 months from 32km to 40km in the mid-latitude region of the Northern Hemisphere. The atmospheric temperature variations over mid-latitude regions in both hemispheres are closely related to the QBO. There are also two narrow zones over the subtropical jet zone where the QBO signals are strong in both hemispheres, approximately parallel to the equator. Finally, we develop a new robust index to describe the strength of the ENSO and QBO signal.

      PubDate: 2017-03-20T14:01:16Z
      DOI: 10.1016/j.jastp.2017.03.008
      Issue No: Vol. 156 (2017)
       
  • Electrical conductivity channels in the atmosphere produced by
           relativistic-electron microbursts from the magnetosphere
    • Authors: Joseph E. Borovsky
      Pages: 22 - 26
      Abstract: Publication date: March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 155
      Author(s): Joseph E. Borovsky
      The properties of a cylindrical-shaped magnetic-field-aligned channel of electrical conductivity produced by the precipitation of relativistic-electrons into the atmosphere during a spatially localized magnetospheric microburst are estimated. The conducting channel connects the middle atmosphere (~50km) to the ionosphere. A channel diameter of ~ 8km with an electric conductivity of 1.2×10−9 Ω−1m−1 near the bottom and 1.8×10−7 Ω−1m−1 higher up is found. In the fair-weather electric field, the higher-conductivity portions of the channel can carry substantial electrical currents.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.01.004
      Issue No: Vol. 155 (2017)
       
  • First observations of electron gyro-harmonic effects under X-mode HF
           pumping the high latitude ionospheric F-region
    • Authors: N.F. Blagoveshchenskaya; T.D. Borisova; A.S. Kalishin; T.K. Yeoman; I. Häggström
      Pages: 36 - 49
      Abstract: Publication date: March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 155
      Author(s): N.F. Blagoveshchenskaya, T.D. Borisova, A.S. Kalishin, T.K. Yeoman, I. Häggström
      We provide the first experimental evidence of the sensitivity of phenomena induced by extraordinary (X-mode) polarized HF high power radio waves to pump frequency stepping across the fifth electron gyro-harmonic (5fce) from below to above. The results were obtained at the EISCAT (European Incoherent Scatter Scientific Association) HF heater facility near Tromsø under effective radiated powers of 456–715MW, when the HF pump wave was transmitted into the magnetic zenith. We have analyzed the behavior and intensities of various spectral lines in the narrowband stimulated electromagnetic emission (SEE) spectra observed far from the heater, HF-enhanced plasma and ion lines (HFPL and HFIL) from EISCAT UHF incoherent scatter radar spectra, and artificial field-aligned irregularities from CUTLASS (Co-operative UK Twin Located Auroral Sounding System) observations, depending on the frequency offset of the pump field relative to the 5fce. At pump frequencies below 5fce the narrowband SEE spectra exhibited very intense so-called stimulated ion Bernstein scatter (SIBS), accompanied by other spectral components, associated with stimulated Brillouin scatter (SBS), which are greatly suppressed and disappeared in the vicinity of 5fce and did not reappear at fH>5fce. As the pump frequency reached 5fce, the abrupt enhancements of the HFPL and HFIL power, the appearance of cascade lines in the plasma line spectra, and the onset of increasing CUTLASS backscatter power occurred. That is opposite to the ordinary mode (O-mode) effects in the vicinity of 5fce. The X-mode pumping at frequencies below and in the vicinity of the fifth electron gyro-harmonic clearly demonstrated an ascending altitude of generation of induced plasma and ion lines from the initial interaction height, whereas for O-mode heating the region of interaction descended. The observations are consistent with the coexistence of the electron acceleration along and across the geomagnetic field at fH<5fce, while only very strong electron acceleration along the magnetic field was observed at fH≥5fce.

      PubDate: 2017-02-10T12:24:31Z
      DOI: 10.1016/j.jastp.2017.02.003
      Issue No: Vol. 155 (2017)
       
  • ANFIS, SVM and ANN soft-computing techniques to estimate daily global
           solar radiation in a warm sub-humid environment
    • Authors: Victor H. Quej; Javier Almorox; Javier A. Arnaldo; Laurel Saito
      Pages: 62 - 70
      Abstract: Publication date: Available online 6 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Victor H. Quej, Javier Almorox, Javier A. Arnaldo, Laurel Saito
      Daily solar radiation is an important variable in many models. In this paper, the accuracy and performance of three soft computing techniques (i.e., adaptive neuro-fuzzy inference system (ANFIS), artificial neural network (ANN) and support vector machine (SVM)) were assessed for predicting daily horizontal global solar radiation from measured meteorological variables in the Yucatán Peninsula, México. Model performance was assessed with statistical indicators such as root mean squared error (RMSE), mean absolute error (MAE) and coefficient of determination (R2). The performance assessment indicates that the SVM technique with requirements of daily maximum and minimum air temperature, extraterrestrial solar radiation and rainfall has better performance than the other techniques and may be a promising alternative to the usual approaches for predicting solar radiation.

      PubDate: 2017-02-10T12:24:31Z
      DOI: 10.1016/j.jastp.2017.02.002
      Issue No: Vol. 155 (2017)
       
  • On the role of horizontal wind shears in the generation of F0.5 layers
           over the dip equatorial location of Thiruvananthapuram: A numerical
           simulation study
    • Authors: N. Mridula; Tarun Kumar Pant
      Pages: 79 - 85
      Abstract: Publication date: March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 155
      Author(s): N. Mridula, Tarun Kumar Pant
      A numerical simulation is carried out to estimate the rate of convergence of ionization required to produce a F0.5 layer with peak plasma frequency (foF0.5) of 3.2MHz from three different background layer densities, over Thiruvananthapuram (8.5°N; 77°E; dip latitude ~ 0.5°N), a dip equatorial station in India. Further the simulation study is extended to understand the convergences required by considering the seasonal mean peak F0.5 layer frequencies also. One possible mechanism by which this convergence can be produced is by a horizontal shear in the meridional wind. The corresponding shears required to generate the layer with the above convergence conditions are estimated. It is found that gravity waves are capable of generating wind shears, leading to the pooling of ionization and the generation of the layer over the dip equator. A meridional wind with the gravity wave induced wind shear is numerically estimated. Finally, the short scale gravity waves of periods around 3–23min have been inferred to be more efficient in generating the wind shear when compared to large scale horizontal waves leading to the generation of F0.5 layer.

      PubDate: 2017-02-23T12:45:38Z
      DOI: 10.1016/j.jastp.2017.02.005
      Issue No: Vol. 155 (2017)
       
  • Statistical analysis of mesospheric gravity waves over King Sejong
           Station, Antarctica (62.2°S, 58.8°W)
    • Authors: Hosik Kam; Geonhwa Jee; Yong Kim; Young-bae Ham; In-Sun Song
      Pages: 86 - 94
      Abstract: Publication date: March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 155
      Author(s): Hosik Kam, Geonhwa Jee, Yong Kim, Young-bae Ham, In-Sun Song
      We have investigated the characteristics of mesospheric short period (<1h) gravity waves which were observed with all-sky images of OH Meinel band and OI 557nm airglows over King Sejong Station (KSS) (62.22°S, 58.78°W) during a period of 2008–2015. By applying 2-dimensional FFT to time differenced images, we derived horizontal wavelengths, phase speeds, and propagating directions (188 and 173 quasi-monochromatic waves from OH and OI airglow images, respectively). The majority of the observed waves propagated predominantly westward, implying that eastward waves were filtered out by strong eastward stratospheric winds. In order to obtain the intrinsic properties of the observed waves, we utilized winds simultaneously measured by KSS Meteor Radar and temperatures from Aura Microwave Limb Sounder (MLS). More than half the waves propagated horizontally, as waves were in Doppler duct or evanescent in the vertical direction. This might be due to strong eastward background wind field in the mesosphere over KSS. For freely propagating waves, the vertical wavelengths were in the interquartile range of 9–33km with a median value of 15km. The vertical wavelengths are shorter than those observed at Halley station (76°S, 27°W) where the majority of the observed waves were freely propagating. The difference in the wave propagating characteristics between KSS and Halley station suggests that gravity waves may affect mesospheric dynamics in this part of the Antarctic Peninsula more strongly than over the Antarctic continent. Furthermore, strong wind shear over KSS played an important role in changing the vertical wavenumbers as the waves propagated upward between two airglow layers (87 and 96km).

      PubDate: 2017-02-23T12:45:38Z
      DOI: 10.1016/j.jastp.2017.02.006
      Issue No: Vol. 155 (2017)
       
  • First ground-based observations of mesopause temperatures above the
           Eastern-Mediterranean Part I: Multi-day oscillations and tides
    • Authors: Israel Silber; Colin Price; Carsten Schmidt; Sabine Wüst; Michael Bittner; Emilio Pecora
      Pages: 95 - 103
      Abstract: Publication date: March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 155
      Author(s): Israel Silber, Colin Price, Carsten Schmidt, Sabine Wüst, Michael Bittner, Emilio Pecora
      The mesopause region (~90km altitude) is the coldest region of our atmosphere, and is found at the boundary between the upper mesosphere and lower thermosphere. Ground-based spectrometers, which are sensitive to the emissions from the hydroxyl (OH*) airglow layer (lying at ~87km altitude), are used to monitor the temperature variability within the mesosphere-lower-thermosphere (MLT), at high temporal resolution. The variability of the MLT region of the atmosphere is driven by momentum deposition from gravity waves, atmospheric tides and planetary waves. The displacement of air caused by these waves can produce strong temperature, wind and species concentration perturbations. In this study we present an analysis of 4-years of OH* rotational temperature data, acquired with the German Aerospace Center (DLR) GRIPS-10 (Ground Based Infrared P-branch Spectrometer) instrument, which was installed in Israel in November 2011. This instrument provided the first long-term ground-based observations of airglow emissions in the Eastern Mediterranean. We show the nocturnal mean temperature analysis, which includes time series as well as spectral analysis of the data. In addition, we obtain (migrating) tidal oscillation estimates from the high resolution (1min) data, by using harmonic fitting, and we analyze the variability of planetary wave signatures in the residual temperature data, which are retrieved after the removal of the tidal harmonic fits from the data. In this analysis of the residual data we find a dominant quasi-5–7 day planetary wave influence on the mesopause temperatures above the Eastern Mediterranean.

      PubDate: 2017-03-02T13:00:13Z
      DOI: 10.1016/j.jastp.2016.08.014
      Issue No: Vol. 155 (2017)
       
  • 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
           Earthquakes
    • 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
           2004
    • 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)
       
  • Advances in lightning research
    • Authors: Vernon Cooray; Farhad Rachidi
      First page: 181
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Vernon Cooray, Farhad Rachidi


      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.10.014
      Issue No: Vol. 154 (2017)
       
  • Cloud-to-ground lightning activity in Colombia and the influence of
           topography
    • Authors: D. Aranguren; J. López; J. Inampués; H. Torres; H. Betz
      Pages: 182 - 189
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): D. Aranguren, J. López, J. Inampués, H. Torres, H. Betz
      Lightning activity on the Colombian mountains, where the altitude varies from 0 to more than 5000MSL, is studied based on VLF/LF lightning detection data and using a 2012–2013 dataset. The influence of altitude is observed by evaluating cloud-to-ground lightning incidence at different altitude intervals. The relationship between ground flash density and altitude gradient vectors is studied. Results show a clear dependence of the flash density on elevation.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.08.010
      Issue No: Vol. 154 (2017)
       
  • X-rays from negative laboratory sparks in air: Influence of the anode
           geometry
    • Authors: Pasan Hettiarachchi; Mahbubur Rahman; Vernon Cooray; Joseph Dwyer
      Pages: 190 - 194
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Pasan Hettiarachchi, Mahbubur Rahman, Vernon Cooray, Joseph Dwyer
      In this experimental work, the influence of the grounded anode geometry is studied on the X-ray production from the laboratory sparks in air at atmospheric pressure when a negative impulse voltage is applied to a high voltage rod which served as a cathode. The result shows that the smaller the diameter of the anode, the higher the energy of X-ray bursts. This observation can be explained by the mechanism that the encounter of negative and positive streamer fronts just before the final breakdown is the event that accelerates electrons to X-ray generating energies, but may not be the only mechanism that generates X-rays.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.07.012
      Issue No: Vol. 154 (2017)
       
  • Characteristics of the most intense lightning storm ever recorded at the
           CN Tower
    • Authors: A.M. Hussein; S. Kazazi; M. Anwar; M. Yusouf; P. Liatos
      Pages: 195 - 206
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): A.M. Hussein, S. Kazazi, M. Anwar, M. Yusouf, P. Liatos
      Lightning strikes to the CN Tower have been optically observed since 1978. In 1990, five independent systems started to operate to simultaneously record parameters of lightning strikes to the tower, including the time derivative of the current, the associated electric and magnetic fields, and the channel optical characteristics. On August 24, 2011, during an unusually severe lightning storm, video records showed that the CN Tower was struck with 52 lightning flashes within 84min and 6.9s. Thus, this storm produced, on average, a flash to the tower every 99s. However, the CN Tower lightning current derivative measurement system only recorded 32 flashes, which were perfectly time-matched with 32 of the 52 video-recorded flashes. It is found that the current derivative measurement system recorded every video-recorded flash that contained at least one return stroke. Based on the analysis of video records, it is noted that each of the storm's 52 flashes contains an initial-stage current, proving that all flashes were upward initiated. This unique CN Tower storm – the most intense ever recorded at the tower – is here thoroughly analyzed, based on video and current records. The inter-flash time within the storm is found to vary between 10.6s and 274s, with an overall average of 98s. It is also found that the inter-flash time between successive non-return-stroke flashes is on average 64% longer than that for successive flashes containing return strokes. Statistical analysis of video and current data clearly reveals that the time duration of flashes containing initial-stage currents and return strokes is on average 27% longer than that of flashes that only have initial-stage currents. Furthermore, it is important to note that the time duration of the initial-stage current in flashes containing no return strokes is on average 76% longer than that in flashes containing return strokes. Therefore, it is possible to conclude that if the time duration of the initial-stage current in a flash is long enough, resulting in large charge transfer, then there is less probability of having return strokes following it. The 32 current-recorded flashes contain a total of 156 return strokes, with an average multiplicity of 4.875. It is worth mentioning that during one decade, 1992–2001, the CN Tower current derivative measurement system only recorded 478 return strokes, demonstrating that the number of return strokes recorded at the tower within about 84min is close to one third of those recorded at the tower during one decade. This finding clearly shows the great value and rarity of the presented extensive lightning current derivative data. Only one of the 32 current-recorded flashes is proved to be positive with a single return stroke. Based on current records, out of a total of 124 inter-stroke time intervals, 94% are found to be within 200ms, with an overall inter-stroke time average of 68.1ms. The maximum inter-stroke time recorded during this storm is 726.3ms, the longest ever recorded at the CN Tower.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.05.002
      Issue No: Vol. 154 (2017)
       
  • Characteristics of the horizontal electric field associated with nearby
           lightning return strokes
    • Authors: J.L. Yu; Y.D. Fan; J.G. Wang; R.H. Qi; M. Zhou; L. Cai; M.J. Cui; Z.J. Yuan
      Pages: 207 - 216
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): J.L. Yu, Y.D. Fan, J.G. Wang, R.H. Qi, M. Zhou, L. Cai, M.J. Cui, Z.J. Yuan
      There exists inherent difficulty in measuring the horizontal electric field (E r) associated with lightning return strokes due to the overshadowing effect of the vertical electric field component, not much progress in E r measurements were observed until now. In order to study the characteristics of E r associated with nearby lightning return strokes, the modified transmission-line model with linear current decay with height (MTLL) return stroke model and Finite Difference Time Domain (FDTD) method were used to calculate E r for 12 observation points with different distances (20, 50 100, and 200m) away from the lightning channel and different heights (0, 10, and 20m) above ground. Four characteristic parameters, namely, the return-stroke speed (v), the total length of the return stroke channel (H), the ground relative permittivity (ε) and the ground conductivity (σ), were considered. Results show that the polarity of E r changes between the ground level and the space. The influence intensity rank of the four characteristic parameters on E r at ground level is: σ>v>ε>H. The influence of the characteristic parameters on E r are more important for v≤0.6c, H≤6000m and σ≤2.5×10−3S/m.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.02.017
      Issue No: Vol. 154 (2017)
       
  • IAR signatures in the ionosphere: Modeling and observations at the
           Chibis-M microsatellite
    • Authors: V. Pilipenko; D. Dudkin; E. Fedorov; V. Korepanov; S. Klimov
      Pages: 217 - 225
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): V. Pilipenko, D. Dudkin, E. Fedorov, V. Korepanov, S. Klimov
      A peculiar feature of geomagnetic variations at middle/low latitudes in the ULF band, just below the fundamental tone of the Schumann resonance, is the occurrence of a multi-band spectral resonant structure, observed by high-sensitivity induction magnetometers during nighttime. The occurrence of such spectral structure was commonly attributed to the Ionospheric Alfvén Resonator (IAR) in the upper ionosphere. Rather surprisingly, while ground observations of the IAR are ubiquitous, there are practically no reports on the IAR signatures from space missions. According to the new paradigm, the multi-band spectral structure excited by a lightning discharge is in fact produced by a regular sequence of an original pulse from a stroke and echo-pulses reflected from the IAR upper boundary. Upon the interaction of initial lightning-generated pulse with the anisotropic lower ionosphere, it partially penetrates into the ionosphere, travels up the ionosphere as an Alfvén pulse, and reflects back from the upper IAR boundary. The superposition of the initial pulse and echo-pulses produces spectra with multiple spectral peaks. Our modeling of Alfvénic pulse propagation in a system with the altitude profile of Alfven velocity modeling the realistic ionosphere has shown that IAR spectral signatures are to be evident only on the ground and above the IAR. Inside the IAR, the superposition of upward and downward propagating pulses produces a more complicated spectral pattern and the IAR spectral signatures deteriorate. We have used electric field data from the low-orbit Chibis-M microsatellite to search for IAR signatures in the ionosphere. We found evidence that the multi-band structure revealed by spectral analysis in the frequency range of interest is indeed the result of a sequence of lightning-produced pulses. According to the proposed conception it seems possible to comprehend why the IAR signatures are less evident in the ionosphere than on the ground.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2015.12.012
      Issue No: Vol. 154 (2017)
       
  • Relationships between cloud-to-ground flashes and hydrometeors in a
           thunderstorm in Fujian province
    • Authors: Tinglong Zhang; Guo Zhao; Changxiong Wei; Yi Gao; Hai Yu; Fangcong Zhou
      Pages: 226 - 235
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Tinglong Zhang, Guo Zhao, Changxiong Wei, Yi Gao, Hai Yu, Fangcong Zhou
      A local severe thunderstorm, occurring near the coastal region in Fujian province, China, was chosen to study the relationships between hydrometeors and cloud-to-ground (CG) flash activities. This thunderstorm case study was carried out by using vehicle-mounted X-band dual-polarization radar on August 28, 2009. On the basis of polarimetric parameters, the hydrometeors were identified by fuzzy logic hydrometeor classification (FLHC). The results show that the thunderstorm grew into a squall line with a maximum flash rate of 85fl/5min in mature stage. Negative CG constituted approximately 97.3% of total CG flashes. More than 90% of the CG flashes occurred in the convective regions, and less than 10% occurred in the stratiform region. The strong echo volume in convective region had a positive linear correlation with the CG flashes rate. Seven types of hydrometeors, namely, rain (RN), aggregates (AG), low-density graupel (LDG), high-density graupel (HDG), vertically aligned ice crystals (VI), drizzle-light rain (DR), and ice crystals (IC), have been classified; the first five of the hydrometeors are predominant in the thunderstorm. RN is located mainly in regions warmer than 0°C; the HDG is located in the middle and lower regions colder than 0°C; and LDG and VI mainly appear in the upper portion of the thunderstorm. The ice hydrometeors seemly had a close relation with CG flashes because the total CG flash rates had a strong positive correlation with the grid number of AG, LDG, HDG, and VI in the convective region. However, the sufficient ice hydrometeors did not produce frequent CG flashes in the stratiform region. It suggests that the dynamic structure is also very important for triggering lightning flashes.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2015.11.007
      Issue No: Vol. 154 (2017)
       
  • A numerical study of aerosol effects on electrification of thunderstorms
    • Authors: Y.B. Tan; Z. Shi; Z.L. Chen; L. Peng; Y. Yang; X.F. Guo; H.R. Chen
      Pages: 236 - 247
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Y.B. Tan, Z. Shi, Z.L. Chen, L. Peng, Y. Yang, X.F. Guo, H.R. Chen
      Numerical simulations are performed to investigate the effect of aerosol on microphysical and electrification in thunderstorm clouds. A two-dimensional (2-D) cumulus model with electrification scheme including non-inductive and inductive charge separation is used. The concentration of aerosol particles with distribution fitted by superimposing three log-normal distributions rises from 50 to 10,000cm−3. The results show that the response of charge separation rate to the increase of aerosol concentration is nonmonotonic. When aerosol concentration is changed from 50 to 1000cm−3, a stronger formation of cloud droplet, graupel and ice crystal results in increasing charge separation via non-inductive and inductive mechanism. However, in the range of 1000–3000cm−3, vapor competition arises in the decrease of ice crystal mixing ratio and the reduction of ice crystals size leads to a slightly decrease in non-inductive charge rate, while inductive charging rate has no significant change in magnitude. Above aerosol concentration of 3000cm−3, the magnitude of charging rate which keeps steady is insensitive to the increase in aerosol concentration. The results also suggest that non-inductive charge separation between ice crystal and graupel contributes to the main upper positive charge region and the middle negative charge region. Inductive graupel–cloud droplet charge separation, on the other hand, is found to play an important role in the development of lower charge region.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2015.11.006
      Issue No: Vol. 154 (2017)
       
  • Solar effect on the Rayleigh-Taylor instability growth rate as simulated
           by the NCAR TIEGCM
    • Authors: Qian
      Abstract: Publication date: April 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 156
      Author(s): Qian Wu
      The TIEGCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) is used to investigate the solar effect on the equatorial ionospheric Rayleigh-Taylor (R-T) instability growth rate, which is responsible for the occurrence of the plasma bubbles. The R-T growth rate is calculated for the solar maximum year 2003 and minimum 2009. The growth rate is strongly dependent on the solar activity. During solar maximum, the pre-reversal enhancement is much stronger leading to higher R-T growth rate. The R-T growth rates from the TIEGCM follow the same solar dependence as the observed occurrence of equatorial plasma bubbles by DMSP satellites. The R-T growth rate also enhances when the day/night terminator is parallel to the magnetic field line near the equator. The R-T growth rate does not correlate well with the solar F10.7 index on a short time scale (~10 days) because the field-line integrated electron content gradient cancels out the positive correlation between the vertical ion drift with the F10.7 index. The TIEGCM result shows the importance of the electron content gradient to the R-T growth rate and the plasma bubble occurrence. The bubble occurrence rates were estimated based on the vertical ion drift simulation results.

      PubDate: 2017-03-20T14:01:16Z
       
  • A review of recent progress in trends in the upper atmosphere
    • Authors: Jan
      Abstract: Publication date: Available online 19 March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jan Laštovička
      The anthropogenic emissions of greenhouse gases affect not only the weather and climate in the troposphere; they affect also long-term trends in the mesosphere-thermosphere-ionosphere system, where the amplitudes of anthropogenic changes are substantially larger than in the troposphere. The last four years have seen significant progress in investigating these trends but also some new puzzles have been created. Observations of the CO2 trend in the lower thermosphere appeared but their interpretation is a matter of debate. The role of ozone in mesospheric temperatures and E-region ionosphere has been confirmed and quantified. Agreement between observational and simulated trends in the thermospheric density, supported by satellite observations of radiative cooling was reached but the most recent result re-opened the problem. Much new partial information about trends in the ionospheric F region was reported. Also new information on other experimental trends helped to improve our understanding of long-term trends in the upper atmosphere. Significant progress has been reached in modelling the long-term trends; in a few parameters the agreement with observed trends is now not only quantitative but also qualitative. Several attempts to explain ionospheric trends without CO2 appeared but they are shown not to be correct; CO2 remains to be the primary (although not the only) trend driver. On the other hand, many open questions or puzzles, listed in Concluding remarks, remain to be investigated.

      PubDate: 2017-03-20T14:01:16Z
       
  • A TIEGCM Numerical Study of the Source and Evolution of Ionospheric
           F-region Tongues of Ionization: Universal Time and Interplanetary Magnetic
           Field Dependence
    • Authors: Jing Liu; Wenbin Wang; Alan Burns; Libo Liu; Joe McInerney
      Abstract: Publication date: Available online 12 March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jing Liu, Wenbin Wang, Alan Burns, Libo Liu, Joe McInerney
      The National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM) has been employed to systematically study the source and evolution of the ionospheric F-region Tongue of Ionization (TOI), which is electron density enhancement in the polar region. The model is run for different Universal Times (UT), season and Interplanetary Magnetic Field (IMF) conditions. It is found that: (1) The TOI formation is critically dependent on UT, preferentially near 2000 UT in the Northern Hemisphere (NH) and near 1600 UT in the Southern Hemisphere (SH). These are the intervals when the high-latitude ion convection throat is closer to the middle-latitude high plasma density source region, so that more plasma can be directly transported into the polar cap region; (2) this different UT dependence between the two Hemispheres occurs, not only because of the different separation of the magnetic poles from the geographic poles in the two hemispheres, but also because of the UT dependence of the mid-latitude source locations (local time, latitude) and the magnitude of plasma density enhancements; (3) the TOI is generally stronger in the SH than it is in the NH, and in winter than in summer; (4) IMF By operates in the opposite sense in the two hemispheres in terms of the TOI pattern such that positive/negative IMF By tends to deflect the TOI toward the morning/afternoon sector in the NH. The opposite condition occurs in the SH.

      PubDate: 2017-03-16T13:57:21Z
      DOI: 10.1016/j.jastp.2017.03.005
       
  • Some new insights of the characteristics of equatorial plasma bubbles
           obtained from Indian region
    • Authors: V.L. Narayanan; S. Gurubaran; M.B. Berlin Shiny; K. Emperumal; P.T. Patil
      Abstract: Publication date: Available online 12 March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): V.L. Narayanan, S. Gurubaran, M.B. Berlin Shiny, K. Emperumal, P.T. Patil
      All-sky imaging observations of OI 630.0nm airglow were carried out in campaign mode from Panhala (16.8°N, 74.1°E geographic; 11.1°N dip latitude), India, during January to March 2008. On 14 of 37 nights, equatorial plasma bubbles were observed. The drift speeds were observed to decrease with time in concurrence with the previous results. The tilts were mostly westward while on rare occasions the plasma bubbles tilt eastwards. The drifts were found to be relatively lesser on disturbed nights while the tilts appear to be marginally larger. The interdepletion distances (or bubble spacings) also showed a decreasing trend with time till midnight indicating that the bubbles approach each other with the passage of time. Such a behavior is not reported earlier and it seems to have important implications for understanding the time evolution of plasma bubbles. On occasions, the bubbles occurred in groups. An ionosonde operating over Indian dip equatorial site Tirunelveli (1.1°N dip latitude) was used to study the variations in the base height of the ionosphere during the plasma bubble observations. The ionosonde measurements indicate lack of significant pre-reversal enhancement (PRE) during geomagnetic quiet days in which the bubbles were observed.

      PubDate: 2017-03-16T13:57:21Z
      DOI: 10.1016/j.jastp.2017.03.006
       
  • Earth's magnetic field effect on MUF calculation and consequences for hmF2
           trend estimates
    • Authors: Ana G. Elias; Bruno S. Zossi; Erdal Yiğit; Zenon Saavedra; Blas F. de Haro Barbas
      Abstract: Publication date: Available online 11 March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Ana G. Elias, Bruno S. Zossi, Erdal Yiğit, Zenon Saavedra, Blas F. de Haro Barbas
      Knowledge of the state of the upper atmosphere, and in particular of the ionosphere, is essential in several applications such as systems used in radio frequency communications, satellite positioning and navigation. In general, these systems depend on the state and evolution of the ionosphere. In all applications involving the ionosphere an essential task is to determine the path and modifications of ray propagation through the ionospheric plasma. The ionospheric refractive index and the maximum usable frequency (MUF) that can be received over a given distance are some key parameters that are crucial for such technological applications. However, currently the representation of these parameters are in general simplified, neglecting the effects of Earth's magnetic field. The value of M(3000)F2, related to the MUF that can be received over 3000km is routinely scaled from ionograms using a technique which also neglects the geomagnetic field effects assuming a standard simplified propagation model. M(3000)F2 is expected to be affected by a systematic trend linked to the secular variations of Earth's magnetic field. On the other hand, among the upper atmospheric effects expected from increasing greenhouse gases concentration is the lowering of the F2-layer peak density height, hmF2. This ionospheric parameter is usually estimated using the M(3000)F2 factor, so it would also carry this “systematic trend”. In this study, the geomagnetic field effect on MUF estimations is analyzed as well as its impact on hmF2 long-term trend estimations. We find that M(3000)F2 increases when the geomagnetic field is included in its calculation, and hence hmF2, estimated using existing methods involving no magnetic field for M(3000)F2 scaling, would present a weak but steady trend linked to these variations which would increase or compensate the few kilometers decrease (~2km per decade) expected from greenhouse gases effect.

      PubDate: 2017-03-16T13:57:21Z
      DOI: 10.1016/j.jastp.2017.03.004
       
  • Observational indications of downward-propagating gravity waves in middle
           atmosphere lidar data
    • Authors: N. Kaifler; B. Kaifler; B. Ehard; S. Gisinger; A. Dörnbrack; M. Rapp; R. Kivi; A. Kozlovsky; M. Lester; B. Liley
      Abstract: Publication date: Available online 10 March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): N. Kaifler, B. Kaifler, B. Ehard, S. Gisinger, A. Dörnbrack, M. Rapp, R. Kivi, A. Kozlovsky, M. Lester, B. Liley
      Two Rayleigh lidars were employed at a southern-hemisphere mid-latitude site in New Zealand (45°S) and a northern-hemisphere high-latitude site in Finland (67°N) in order to observe gravity waves between 30 and 85km altitude under wintertime conditions. Two-dimensional wavelet analysis is used to analyze temperature perturbations caused by gravity waves and to determine their vertical wavelengths and phase progression. In both datasets, upward phase progression waves occur frequently between 30 and 85km altitude. Six cases of large-amplitude wave packets are selected which exhibit upward phase progression in the stratosphere and/or mesosphere. We argue that these wave packets propagate downward and we discuss possible wave generation mechanisms. Spectral analysis reveals that superpositions of two or three wave packets are common. Furthermore, their characteristics often match those of upward-propagating waves which are observed at the same time or earlier. In the dataset means, the contribution of upward phase progression waves to the potential energy density E p is largest in the lower stratosphere above Finland. There, E p of upward and downward phase progression waves is comparable. At 85km one third of the potential energy carried by propagating waves is attributed to upward phase progression waves. In some cases E p of upward phase progression waves far exceeds E p of downward phase progression waves. The downward-propagating waves might be generated in situ in the middle atmosphere or arise from reflection of upward-propagating waves.

      PubDate: 2017-03-16T13:57:21Z
      DOI: 10.1016/j.jastp.2017.03.003
       
  • IFC-Ed. board
    • Abstract: Publication date: March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 155


      PubDate: 2017-03-02T13:00:13Z
       
  • Effect of Tropospheric Models on Derived Precipitable Water Vapor over
           Southeast Asia
    • Authors: Zhoobin Rahimi; Helmi Zulhaidi Mohd Shafri; Faridah Binti Othman; Masayu Norman
      Abstract: Publication date: Available online 24 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Zhoobin Rahimi, Helmi Zulhaidi Mohd Shafri, Faridah Binti Othman, Masayu Norman
      An interesting subject in the field of GPS technology is estimating variation of precipitable water vapor (PWV). This estimation can be used as a data source to assess and monitor rapid changes in meteorological conditions. So far, numerous GPS stations are distributed across the world and the number of GPS networks is increasing. Despite these developments, a challenging aspect of estimating PWV through GPS networks is the need of tropospheric parameters such as temperature, pressure, and relative humidity (Liu et al., 2015). To estimate the tropospheric parameters, global pressure temperature (GPT) model developed by (Boehm et al., 2007) is widely used in geodetic analysis for GPS observations. To improve the accuracy, (Lagler et al., 2013) introduced GPT2 model by adding annual and semi-annual variation effects to GPT model. Furthermore,(Boehm et al., 2015)(Boehm et al., 2015)(Boehm et al., 2015) (Boehm et al., 2015) proposed the GPT2 wet (GPT2w) model which uses water vapor pressure to improve the calculations. The global accuracy of GPT2 and GPT2w models has been evaluated by previous researches (Fund et al., 2011) (Munekane and Boehm, 2010); however, investigations to assess the accuracy of global tropospheric models in tropical regions such as Southeast Asia is not sufficient. This study tests and examines the accuracy of GPT2w as one of the most recent versions of tropospheric models (Boehm et al., 2015). We developed a new regional model called Malaysian Pressure Temperature (MPT) model, and compared this model with GPT2w model. The compared results at one international GNSS service (IGS) station located in the south of Peninsula Malaysia shows that MPT model has a better performance than GPT2w model to produce PWV during monsoon season. According to the results, MPT has improved the accuracy of estimated pressure and temperature by 30% and 10%, respectively, in comparison with GPT2w model. These results indicate that MPT model can be a good alternative tool in the absence of meteorological sensors at GPS stations in Peninsula Malaysia. Therefore, for GPS-based studies, we recommend MPT model to be used as a complementary tool for the Malaysia Real-Time Kinematic Network to develop a real-time PWV monitoring system.

      PubDate: 2017-03-02T13:00:13Z
      DOI: 10.1016/j.jastp.2017.02.011
       
  • Parametric study of density cavities caused by ion outflow in the topside
           ionosphere
    • Authors: Liyuan Mei; William Lotko; Roger H. Varney; Joe D. Huba
      Abstract: Publication date: Available online 24 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Liyuan Mei, William Lotko, Roger H. Varney, Joe D. Huba
      Plasma density cavities are correlated with heavy ion outflow where ions are heated transversely by wave particle interactions (WPIs). This paper presents the first result of a 3D ionospheric fluid model that incorporates plasma temperature anisotropies and a phenomenological treatment of WPIs, leading to transversely accelerated ions (TAIs). It is demonstrated that O+ outflow can generate density cavities in the topside ionosphere. With the empirical heating rate applied in a designated heating region on the dayside, the O+ species in the heating region is accelerated upward by the mirror force. The O+ species below the heating region upflows under the parallel pressure gradient force and the parallel electric force. As the O+ species flows upward, the plasma is eroded both below and inside the heating region. Parametric modeling studies show that the depth of density cavities in the upper ionosphere increases as the heating rate increases. The percent change in the density of the cavity relative to the local background density is practically independent of the low-altitude cutoff of the heating region, but the altitude of the relative density minimum moves upward with the increasing altitude of cutoff. The O+ flux is insensitive to the change of the heating rate, while depends strongly on the altitude of cutoff. Using empirical values of the initial heating rate and the height of the low-altitude boundary as input, the ranges of the modeled electron density and the O+ outflow moments are in reasonable agreement with observations of a storm-time density cavity observed by the FAST satellite. The 3D ionospheric model has the potential to be coupled to magnetospheric models for magnetosphere-ionosphere (MI) coupling.

      PubDate: 2017-03-02T13:00:13Z
      DOI: 10.1016/j.jastp.2017.02.013
       
  • Ionospheric Plasma Disturbances Generated by Naturally Occurring
           Large-scale Anomalous Heat Sources
    • Authors: Rezy Pradipta; Min-Chang Lee; Anthea J. Coster; Craig A. Tepley; Michael P. Sulzer; Sixto A. Gonzalez
      Abstract: Publication date: Available online 22 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Rezy Pradipta, Min-Chang Lee, Anthea J. Coster, Craig A. Tepley, Michael P. Sulzer, Sixto A. Gonzalez
      We report the findings from our investigation on the possibility of large-scale anomalous thermal gradients to generate acoustic-gravity waves (AGWs) and traveling ionospheric disturbances (TIDs). In particular, here we consider the case of summer 2006 North American heat wave event as a concrete example of such large-scale natural thermal gradients. This special scenario of AGW/TID generation was formulated based on the results of our experiments at the Arecibo Observatory in July 2006, followed by a systematic monitoring/surveillance of total electron content (TEC) fluctuations over North America in 2005-2007 using the MIT Haystack Observatory's Madrigal database. The data from our Arecibo experiments indicate a continual occurrence of intense AGW/TID over the Caribbean on 21-24 July 2006, and the Madrigal TEC data analysis shows that the overall level of TID activity over North America had increased by ∼0.2 TECU during the summer 2006 heat wave event. Our proposed scenario is in agreement with these empirical observations, and is generally consistent with a number of past ionospheric HF heating experiments related to AGW/TID generation.

      PubDate: 2017-02-23T12:45:38Z
      DOI: 10.1016/j.jastp.2017.02.010
       
  • Ionospheric F-region observations over American sector during an intense
           space weather event using multi-instruments
    • Authors: A.J. de Abreu; I.M. Martin; P.R. Fagundes; K. Venkatesh; I.S. Batista; R. de Jesus; M. Rockenback; A. Coster; M. Gende; M.A. Alves; M. Wild
      Abstract: Publication date: Available online 21 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.J. de Abreu, I.M. Martin, P.R. Fagundes, K. Venkatesh, I.S. Batista, R. de Jesus, M. Rockenback, A. Coster, M. Gende, M.A. Alves, M. Wild
      The critical interaction between the magnetosphere and ionosphere during intense geomagnetic storms continues to be important to space weather studies. In this investigation, we present and discuss the ionospheric F-region observations in the equatorial, low- and mid-latitude regions in both hemispheres over American sector during the intense geomagnetic storm on 01–03 June 2013. The geomagnetic storm reached a minimum Dst of −119 nT at 0900 UT on 01 June. For this investigation, we present vertical total electron content (VTEC) and phase fluctuations (in TECU/min) from a chain of 10 GPS stations and the ionospheric parameters foF2 and h’F from a chain of 4 digital ionosonde stations, covering from equatorial to mid-latitudes regions over American sector during the entire storm-time period 31 May–03 June 2013. In addition, the plasma density observed from DMSP satellites is presented. The results obtained show that during the sudden impulse/SSC and throughout the main phase of the storm, a large positive phase was observed in mid-latitudes of the northern hemisphere, which could be due to changes in the thermospheric wind circulation. On the other hand, in the mid-latitudes of the southern hemisphere, no deviations are observed in VTEC and foF2 when compared to the quiet period. During the long recovery phase of the storm on 01–02 June, a north-south asymmetry is observed in the F-region. The study confirms the dominant role of the thermospheric winds on north-south asymmetry in the ionospheric F-region. The ionospheric irregularities are found to be confined in the equatorial region, of the bottomside spread-F type, before and during the geomagnetic storm. It shows that the geomagnetic storm did not affect the generation or suppression of ionospheric irregularities at the stations investigated.

      PubDate: 2017-02-23T12:45:38Z
      DOI: 10.1016/j.jastp.2017.02.009
       
  • Interplanetary Drivers of Daytime Penetration Electric Field into
           Equatorial Ionosphere during CIR-Induced Geomagnetic Storms
    • Authors: Thana Yeeram
      Abstract: Publication date: Available online 21 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Thana Yeeram
      Observations based on the magnetometer data of the response of the daytime equatorial electric field to the geomagnetic storms induced by corotating interaction regions (CIRs) during 2007 – 2010 reveal many events of striking long duration of multiple short-lived prompt penetration electric fields (PPEFs). The PPEFs essentially occurred in the main phase of the storms, which are associated with the ring current and magnetic reconnection of the southward z-component of the interplanetary magnetic field (IMF Bz) in relation to the Alfvén waves. The behaviors of the electric field penetration during the storms are consistent with the shielding theory. Particularly, the PPEF is found to be complex due to transient variations in the solar wind dynamic pressure (SWDP) and the IMF Bz in the CIRs. The PPEF is temporary suppressed for about an hour under a shock in association with a drop in the SWDP. The interplanetary electric field Ey is the main driver of the PPEFs, when the solar wind speed, SWDP, and the symmetric ring current are nearly constant, even in the recovery phase. The PPEF is allowed under the condition of high and variable SWDP. The shocks with a northward IMF Bz shield the PPEFs when the SWDP is nearly constant. The partial ring current is strongest in the large and northward IMF Bz, where the shielding effect is greater than the undershielding caused by the large SWDP. The results may provide an important step to study equatorial and low latitude ionospheric electrodynamics in the solar minimum conditions.

      PubDate: 2017-02-23T12:45:38Z
      DOI: 10.1016/j.jastp.2017.02.008
       
  • Long-term variations and trends in the polar E-region
    • Authors: L.M. Bjoland; Y. Ogawa; C. Hall; M. Rietveld; U.P. Løvhaug; C. La Hoz; H. Miyaoka
      Abstract: Publication date: Available online 20 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): L.M. Bjoland, Y. Ogawa, C. Hall, M. Rietveld, U.P. Løvhaug, C. La Hoz, H. Miyaoka
      As the EISCAT UHF radar system in Northern Scandinavia started its operations in the early 1980s, the collected data cover about three solar cycles. These long time-series provide us the opportunity to study long-term variations and trends of ionospheric parameters in the high latitude region. In the present study we have used the EISCAT Tromsø UHF data to investigate variations of the Hall conductivity and ion temperatures in the E-region around noon. Both the ion temperature and the peak altitude of the Hall conductivity are confirmed to depend strongly on solar zenith angle. However, the dependence on solar activity seems to be weak. In order to search for trends in these parameters, the ion temperature and peak altitude of the Hall conductivity data were adjusted for their seasonal and solar cycle dependence. A very weak descent (∼0.2km/ decade) was seen in the peak altitude of the Hall conductivity. The ion temperature at 110km shows a cooling trend (∼10K/ decade). However, other parameters than solar zenith angle and solar activity seem to affect the ion temperature at this altitude, and a better understanding of these parameters is necessary to derive a conclusive trend. In this paper, we discuss what may cause the characteristics of the variations in the electric conductivities and ion temperatures in the high latitude region.

      PubDate: 2017-02-23T12:45:38Z
      DOI: 10.1016/j.jastp.2017.02.007
       
  • Impacts of a sudden stratospheric warming on the mesospheric metal layers
    • Authors: Wuhu Feng; Bernd Kaifler; Daniel R. Marsh; Josef Höffner; Ulf-Peter Hoppe; Bifford P. Williams; John M.C. Plane
      Abstract: Publication date: Available online 11 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Wuhu Feng, Bernd Kaifler, Daniel R. Marsh, Josef Höffner, Ulf-Peter Hoppe, Bifford P. Williams, John M.C. Plane
      We report measurements of atomic sodium, iron and temperature in the mesosphere and lower thermosphere (MLT) made by ground-based lidars at the ALOMAR observatory (69°N, 16°E) during a major sudden stratospheric warming (SSW) event that occurred in January 2009. The high resolution temporal observations allow the responses of the Na and Fe layers to the SSW at high northern latitudes to be investigated. A significant cooling with temperatures as low as 136K around 90km was observed on 22–23 January 2009, along with substantial depletions of the Na and Fe layers (an ~80% decrease in the column abundance with respect to the mean over the observation period). The Whole Atmosphere Community Climate Model (WACCM) incorporating the chemistry of Na, Fe, Mg and K, and nudged with reanalysis data below 60km, captures well the timing of the SSW, although the extent of the cooling and consequently the depletion in the Na and Fe layers is slightly underestimated. The model also predicts that the perturbations to the metal layers would have been observable even at equatorial latitudes. The modelled Mg layer responds in a very similar way to Na and Fe, whereas the K layer is barely affected by the SSW because of the enhanced conversion of K+ ions to K atoms at the very low temperatures.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2017.02.004
       
  • IFC-Ed. board
    • Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154


      PubDate: 2017-02-15T12:30:13Z
       
  • Quasi-Biennial Oscillation signatures in the diurnal tidal winds over
           Cachoeira Paulista, Brazil
    • Authors: Luciana Rodrigues de Araújo; Lourivaldo Mota Lima; Christoph Jacobi; Paulo Prado Batista
      Abstract: Publication date: Available online 4 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Luciana Rodrigues de Araújo, Lourivaldo Mota Lima, Christoph Jacobi, Paulo Prado Batista
      Mesosphere/lower thermosphere winds obtained by meteor radar over Cachoeira Paulista (22.7°S, 45.0°W), Brazil, have been used to investigate the interannual variability of the diurnal tidal (DT) wind amplitude. The monthly DT displays year to year variations and their amplitudes are strongest during the westerly phase of the quasi-biennial oscillation (QBO) at the 30 hPa level. This can be observed in all seasons in the meridional component, whilst in the zonal component the signal is clearer during austral autumn, when the diurnal tide is strongest in this latitude. The spectrum obtained from the deseasonalized amplitudes shows a peak near 26 months in the meridional component, which can be associated to the stratospheric QBO. The QBO modulation of the DT amplitude shows a quasi-decadal variation, and it is stronger during the maximum of the solar cycle.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.02.001
       
  • Modelling the descent of nitric oxide during the Elevated Stratopause
           Event of January 2013
    • Authors: Yvan J. Orsolini; Varavut Limpasuvan; Kristell Pérot; Patrick Espy; Robert Hibbins; Stefan Lossow; Katarina Raaholt Larsson; Donal Murtagh
      Abstract: Publication date: Available online 4 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Yvan J. Orsolini, Varavut Limpasuvan, Kristell Pérot, Patrick Espy, Robert Hibbins, Stefan Lossow, Katarina Raaholt Larsson, Donal Murtagh
      Using simulations with a whole-atmosphere chemistry-climate model nudged by meteorological analyses, global satellite observations of nitrogen oxide (NO) and water vapour by the Sub-Millimetre Radiometer instrument (SMR), of temperature by the Microwave Limb Sounder (MLS), as well as local radar observations, this study examines the recent major stratospheric sudden warming accompanied by an elevated stratopause event (ESE) that occurred in January 2013. We examine dynamical processes during the ESE, including the role of planetary wave, gravity wave and tidal forcing on the initiation of the descent in the mesosphere-lower thermosphere (MLT) and its continuation throughout the mesosphere and stratosphere, as well as the impact of model eddy diffusion. We analyse the transport of NO and find the model underestimates the large descent of NO compared to SMR observations. We demonstrate that the discrepancy arises abruptly in the MLT region at a time when the resolved wave forcing and the planetary wave activity increase, just before the elevated stratopause reforms. The discrepancy persists despite doubling the model eddy diffusion. While the simulations reproduce an enhancement of the semi-diurnal tide following the onset of the 2013 SSW, corroborating new meteor radar observations at high northern latitudes over Trondheim (63.4°N), the modelled tidal contribution to the forcing of the mean meridional circulation and to the descent is a small portion of the resolved wave forcing, and lags it by about ten days.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.01.006
       
  • Raindrop size distribution and vertical velocity characteristics in the
           rainband of Hurricane Bolaven (2012) observed by a 1290MHz wind profiler
    • Authors: Dong-Kyun Kim; Dong-In Lee
      Abstract: Publication date: Available online 1 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Dong-Kyun Kim, Dong-In Lee
      Microphysics and vertical velocity characteristics between weak and strong rainband regions of Hurricane Bolaven were investigated primarily from 1290MHz (UHF) wind profiler measurements on 27~28 August 2012. With a focus on regions with radar reflectivities greater than 30 dBZ below a melting level, raindrop size distributions (DSDs) and related rain parameters retrieved from profiler Doppler spectra were examined. Temporal variations in vertical structure and bright band from a widespread stratiform to a relatively narrow, intense rainband were examined as the rainbands move over the land in the southern coast of Korea. Based on vertical characteristics in radar reflectivity, Doppler velocity, and vertical air motion (w) profiles, the rainbands were classified into a stratiform (S) region with a strong bright band and mixed stratiform-convective (S-C) region with a weak or non-existent bright band. The retrieved w fields showed that updrafts were dominant in the mixed S-C region and downdrafts in the S region. More broad histograms in both radar reflectivity (Z) and mass-weighted mean diameter (D m ) were found in the S period. Compared to the Z distribution, rain rate (R) was more widely distributed in the mixed S-C region than in the S region. This is largely because R values were more variable in association with stronger updrafts in this region since they depend on fall velocities of raindrops. Higher R and smaller D m mean values were analyzed within relatively strong updrafts in the mixed S-C period compared to those in the S period. Even when the w correction is applied, the mean D m was still slightly smaller in the mixed S-C region, indicating that there is a relatively larger number of small drops than those in the S region.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.01.005
       
  • First ground-based observations of mesopause temperatures above the
           Eastern-Mediterranean Part II: OH⁎-climatology and gravity wave activity
           
    • Authors: Sabine Wüst; Carsten Schmidt; Michael Bittner; Israel Silber; Colin Price; Jeng-Hwa Yee; Martin G. Mlynczak; James M. Russell
      Abstract: Publication date: Available online 29 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Sabine Wüst, Carsten Schmidt, Michael Bittner, Israel Silber, Colin Price, Jeng-Hwa Yee, Martin G. Mlynczak, James M. Russell
      In this study, we present an analysis of approximately four years of nightly temperature data, acquired with the OH-spectrometer GRIPS 10 (GRound based Infrared P-branch Spectrometer), which was installed in Tel Aviv (32.11°N, 34.8°E), Israel in November, 2011 for routine measurements. As our instrument does not give any height information, we use TIMED-SABER data in order to answer the question concerning the height region our measurement technique exactly addresses. For the first time, we estimate the density of wave potential energy for periods between some minutes and some hours for this station. These values are typical for gravity waves. Since GRIPS measurements do not currently provide vertically resolved data, the Brunt-Väisälä frequency, which is needed for the estimation of potential energy density, is calculated using TIMED-SABER measurements. The monthly mean density of wave potential energy is presented for periods shorter and longer than 60min. For the winter months (November, December, and January), the data base allows the calculation of a seasonal mean for the different years. This publication is the companion paper to Silber et al. (2016). Here, we focus on oscillations with shorter periods.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.01.003
       
  • Detailed study of Pi2 damped oscillations from low latitude magnetic
           observatory
    • Authors: Jayashree Bulusu; Kusumita Arora; Nandini Nagarajan
      Abstract: Publication date: Available online 25 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jayashree Bulusu, Kusumita Arora, Nandini Nagarajan
      The study of low latitude damped Pi2 oscillations (40–150sec) are investigated using archived data from Chouttuppal (CPL), geoelctric observatory, operated by National Geophysical Research Institute (NGRI), Hyderabad, India. The period of investigation is during solar cycle 21 (1975–1983). All the Pi2 events identified during this period are subjected to detailed analysis for their association with substorm and non-substorm events. It is interesting to note that there is equal probability of occurrence of Pi2s with or without a substorm. The Pi2 frequencies associated with substorms showed an increased value in the post-midnight sector than compared to the Pre-midnight sectors. The non-substorm Pi2s are seen to be associated with lower levels of geomagnetic activity. The corresponding period of Pi2s decreases with increasing level of activity. While the generation of Pi2s are generally attributed to substorm onset, it is seen that the quiet time non-substorm events are related to plasmaspheric cavity mode resonances at low latitudes.

      PubDate: 2017-01-28T11:46:34Z
      DOI: 10.1016/j.jastp.2017.01.002
       
  • Study of 1-minute rain rate integration statistic in South Korea
    • Authors: Sujan Shrestha; Dong-You Choi
      Abstract: Publication date: Available online 21 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Sujan Shrestha, Dong-You Choi
      The design of millimeter wave communication links and the study of propagation impairments at higher frequencies due to a hydrometeor, particularly rain, require the knowledge of 1-min. rainfall rate data. Signal attenuation in space communication results are due to absorption and scattering of radio wave energy. Radio wave attenuation due to rain depends on the relevance of a 1-min. integration time for the rain rate. However, in practice, securing these data over a wide range of areas is difficult. Long term precipitation data are readily available. However, there is a need for a 1-min. rainfall rate in the rain attenuation prediction models for a better estimation of the attenuation. In this paper, we classify and survey the prominent 1-min. rain rate models. Regression analysis was performed for the study of cumulative rainfall data measured experimentally for a decade in nine different regions in South Korea, with 93 different locations, using the experimental 1-min. rainfall accumulation. To visualize the 1-min. rainfall rate applicable for the whole region for 0.01% of the time, we have considered the variation in the rain rate for 40 stations across South Korea. The Kriging interpolation method was used for spatial interpolation of the rain rate values for 0.01% of the time into a regular grid to obtain a highly consistent and predictable rainfall variation. The rain rate exceeded the 1-min. interval that was measured through the rain gauge compared to the rainfall data estimated using the International Telecommunication Union Radio Communication Sector model (ITU-R P.837-6) along with the empirical methods as Segal, Burgueno et al., Chebil and Rahman, logarithmic, exponential and global coefficients, second and third order polynomial fits, and Model 1 for Icheon regions under the regional and average coefficient set. The ITU-R P. 837-6 exibits a lower relative error percentage of 3.32 and 12.59% in the 5- and 10-min. to 1-min. conversion, whereas the higher error percentages of 24.64, 46.44 and 58.46% for the 20-, 30- and 60-min. to 1-min., conversion were obtained in the Icheon region. The available experimental rainfall data were sampled on equiprobable rain-rate values where the application of these models to experimentally obtained data exhibits a variable error rate. This paper aims to provide a better survey of various conversion methods to model a 1-min. rain rate applicable to the South Korea regions with a suitable contour plot at 0.01% of the time.

      PubDate: 2017-01-22T11:36:37Z
      DOI: 10.1016/j.jastp.2017.01.001
       
  • 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)
       
  • 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
       
  • NeQUICK 2 TOTAL ELECTRON CONTENT PREDICTIONS FOR MIDDLE LATITUDES OF NORTH
           AMERICAN REGION DURING A DEEP SOLAR MINIMUM
    • 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
       
  • 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
       
  • 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
       
 
 
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