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  Subjects -> METEOROLOGY (Total: 78 journals)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 2)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 4)
Advances in Meteorology     Open Access   (Followers: 4)
Aeolian Research     Hybrid Journal   (Followers: 2)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 7)
American Journal of Climate Change     Open Access   (Followers: 5)
Asian Journal of Earth Sciences     Open Access   (Followers: 17)
Atmósfera     Open Access  
Atmosphere     Open Access   (Followers: 2)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 4)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 11)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 7)
Atmospheric Research     Hybrid Journal   (Followers: 19)
Atmospheric Science Letters     Hybrid Journal   (Followers: 6)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 9)
Bulletin of the American Meteorological Society     Open Access   (Followers: 13)
Carbon Balance and Management     Open Access   (Followers: 5)
Climate     Open Access   (Followers: 1)
Climate Change Economics     Hybrid Journal   (Followers: 16)
Climate Dynamics     Hybrid Journal   (Followers: 13)
Climate law     Hybrid Journal   (Followers: 3)
Climate of the Past (CP)     Open Access   (Followers: 4)
Climate of the Past Discussions (CPD)     Open Access   (Followers: 2)
Climate Policy     Hybrid Journal   (Followers: 19)
Climate Risk Management     Open Access  
Climatic Change     Hybrid Journal   (Followers: 31)
Developments in Atmospheric Science     Full-text available via subscription   (Followers: 3)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 3)
Earth Perspectives - Transdisciplinarity Enabled     Open Access  
Energy & Environment     Full-text available via subscription   (Followers: 14)
Environmental and Climate Technologies     Open Access   (Followers: 1)
Global Meteorology     Open Access  
International Journal of Atmospheric Sciences     Open Access   (Followers: 2)
International Journal of Biometeorology     Hybrid Journal   (Followers: 1)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (Followers: 7)
International Journal of Climatology     Hybrid Journal   (Followers: 12)
International Journal of Image and Data Fusion     Hybrid Journal  
ISRN Meteorology     Open Access  
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (Followers: 7)
Journal of Atmospheric and Oceanic Technology     Full-text available via subscription   (Followers: 10)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 14)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 2)
Journal of Climate     Full-text available via subscription   (Followers: 23)
Journal of Climatology     Open Access  
Journal of Hydrology and Meteorology     Open Access   (Followers: 2)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 3)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 3)
Journal of Meteorology and Climate Science     Full-text available via subscription  
Journal of Space Weather and Space Climate     Open Access   (Followers: 4)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 23)
Journal of Weather Modification     Full-text available via subscription  
Large Marine Ecosystems     Full-text available via subscription   (Followers: 1)
Meteorologica     Open Access  
Meteorological Applications     Hybrid Journal   (Followers: 1)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 2)
Meteorology and Atmospheric Physics     Hybrid Journal   (Followers: 2)
Michigan Journal of Sustainability     Open Access  
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 1)
Monthly Notices of the Royal Astronomical Society Letters     Hybrid Journal   (Followers: 2)
Monthly Weather Review     Full-text available via subscription   (Followers: 12)
Nature Climate Change     Full-text available via subscription   (Followers: 33)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 14)
Open Journal of Modern Hydrology     Open Access   (Followers: 1)
Revista Brasileira de Meteorologia     Open Access   (Followers: 1)
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 3)
Space Weather     Full-text available via subscription   (Followers: 3)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 3)
Tellus A     Open Access   (Followers: 4)
Tellus B     Open Access   (Followers: 7)
The Cryosphere (TC)     Open Access   (Followers: 1)
The Cryosphere Discussions (TCD)     Open Access   (Followers: 1)
The Quarterly Journal of the Royal Meteorological Society     Hybrid Journal   (Followers: 5)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 2)
Weather     Hybrid Journal   (Followers: 2)
Weather and Climate Extremes     Open Access   (Followers: 2)
Weather and Forecasting     Full-text available via subscription   (Followers: 1)
Weatherwise     Hybrid Journal  
气候与环境研究     Full-text available via subscription  
Journal Cover Journal of Atmospheric and Solar-Terrestrial Physics
   Journal TOC RSS feeds Export to Zotero [16 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1364-6826
     Published by Elsevier Homepage  [2570 journals]   [SJR: 0.955]   [H-I: 56]
  • Role of surface and boundary layer processes in the temporal evolution of
           monsoon low level jet (MLLJ) observed from High resolution Doppler wind
           lidar measurements
    • Abstract: Publication date: Available online 2 October 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R.D. Ruchith , P. Ernest Raj , M.C.R. Kalapureddy , T. Dharmaraj
      Monsoon Low Level Jet (MLLJ) is one of the important components of Indian summer monsoon. Using high-resolution measurements of boundary layer wind profiles from a Doppler wind lidar at Mahbubnagar (16.73°N, 77.98°E and 445m above mean sea level), India, the temporal evolution of the MLLJ has been investigated. Both jet core height and jet speed show clear diurnal variation during the monsoon season. Jet core starts descending down in the evening hours and remains at a height between 600m – 900m (above surface level) during nighttime. Soon after local sunrise, jet core starts ascending and reaches heights above 1800m by afternoon hours. Jet core speed starts strengthening in the nighttime and attains maximum intensity in the early morning hours and then the core speeds decrease around the time when the jet core is at its maximum height. Simultaneous diurnal variations of surface temperature, sensible heat flux, latent heat flux and Richardson number show that daytime heating and turbulence in surface layers enhance mixing in the daytime boundary layer which helps in lifting of the jet core. Shear produced turbulence and momentum fluxes also play a significant role in the diurnal variation of MLLJ. Factors influencing the evolution of the convective boundary layer and factors responsible for formation of nocturnal boundary layer are closely associated with the diurnal variation of MLLJ occurring over the low-latitude south Indian peninsular region during monsoon season. The results emphasize the importance of continuous and high spatial-temporal resolution wind profile measurements in the monsoon boundary layer from a Doppler wind lidar.


      PubDate: 2014-10-06T07:47:17Z
       
  • Atmospheric surface layer responses to the extreme lightning day in
           plateau region in India
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): Arun K. Dwivedi , Sagarika Chandra , Manoj Kumar , Sanjay Kumar , N.V.P. Kiran Kumar
      This paper discusses the observations of the atmospheric surface layer (ASL) parameters during the lightning event. During this event behaviour of surface layer parameters has been observed. Other derived parameters like Monin–Obukhov stability parameter (z/L), turbulent kinetic energy (TKE), momentum flux (MF) and sensible heat flux (SHF) have also been considered during this stochastic phenomenon. Characteristics of these surface layer parameters have been analysed during lightning period and compared with the clear weather day. During the peak period of the lightning, the incoming solar irradiance was reduced by one third of its normal value, resulting in an air-temperature decrement near the surface in the range of 4°C to 6°C. In addition to that a significant reduction in energy exchanges between surface and lower lying atmosphere (viz. TKE, MF and SHF), has also been observed. The rate of instantaneous decay in solar irradiance and SHF from the first strike to its peak strike time was larger than that seen during clear day hours. The normalized standard deviations of wind components during clear day were studied using Monin–Obukhov similarity theory (MOST) and the results have been compared with earlier studies reported in the literature.


      PubDate: 2014-10-01T06:39:25Z
       
  • Improved performance over time of integration in momentum flux estimation
           using Postset Beam Steering technique
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): V.K. Anandan , Shridhar Kumar , V.N. Sureshbabu , T. Narayana Rao , M. Purnachandra Rao , Toshitaka Tsuda
      Using time series of vertical data collected from middle and upper atmospheric (MU) radar, the adaptive Capon beamforming technique is used to synthesize beams in the desired pointing directions within the radar beamwidth. Beam synthesis has been performed at the tilt angle of 1.5° with different beam configurations (4 beams, 8 beams, 16 beams, 32 beams, 48 beams and 64 beams), which are equally separated azimuth plane. The Power Spectral Density (PSD) is obtained from the synthesized beam using the eigenvector (EV) sub-space based spectral estimation method. The first moment is derived from the EV produced spectrum using the adaptive moment estimation method. From the first order moments derived along equally spaced pointing directions, radial wind velocities are readily obtained in the corresponding directions. From radial velocity obtained in various pointing directions, momentum flux of short duration (<2h) is estimated using the symmetric beam method (SBM) which requires 4 symmetric beams separated by 90° in the azimuth plane. A comparative study has been performed to study the optimum beam configuration, required for the flux estimation, which shows that 32 beam configuration is sufficient to estimate the flux with least error. Study with 32 beam configuration, gives 8 sets of symmetric beams (8×4). Using 8 set of beams, the flux is estimated for each set of beams and averaged. The averaged flux is further integrated over different lengths of time up to 14h. This systematic method for the estimation of momentum flux reveals that spatial averaging of beams in azimuth and integration over different lengths of time have reduced the time of integration from 15 to 16h for the conventional approach to 8–9h for the new approach using Postset Beam Steering (PBS) technique. The flux estimated with spatial-averaging of beam using PBS technique has been compared with other standard methods.


      PubDate: 2014-10-01T06:39:25Z
       
  • IFC-Ed. board
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120




      PubDate: 2014-10-01T06:39:25Z
       
  • Clustering of atmospheric data by the deterministic annealing
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): Alexander Ruzmaikin , Alexandre Guillaume
      The Deterministic Annealing (DA) clustering method, which determines the cluster centers, their sizes, and probability with which data are associated with each cluster, is tested using artificial data and applied to atmospheric satellite data. It is also shown how the method can be advantageously used to characterize data outliers. The method is based on the optimization of a cost function that depends both on the averaged distance of data points to cluster centers and the Shannon entropy of the data. The cost function uses two independent parameters in a close analog to the Gibbs' thermodynamics (with the averaged distance similar to the internal energy) allowing a sufficient control of the formation of new clusters as “phase transitions” by changing the clustering parameter similar to the thermodynamical temperature. The satellite data used are a temperature–water vapor data set and the positions of deep convective clouds obtained from the measurements of the Atmospheric InfraRed Sounder (AIRS) on the Aqua satellite. The clustering of these data is demonstrated for the 2D case (at fixed pressure level) and for the 3D case at multiple pressure levels indicating potential applications to investigation of distributions of atmospheric profiles.


      PubDate: 2014-10-01T06:39:25Z
       
  • Latitudinal effect on the diurnal variation of the F2 layer at low solar
           activity
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): J.O. Adeniyi , B.W. Joshua
      The latitudinal effect on the diurnal variation of the F2 layer peak parameters at low solar activity was investigated. Our results reveal that the likelihood of the occurrence of a noon-bite out is reduced with increase in latitude. Beyond 21.770°N geomagnetic latitude, it is hardly noticed. Daytime maximum NmF2 peak occurs mostly after midday in the northern hemisphere. Similar variations occur in the southern hemisphere, although it varies with the seasons, and latitudes. The maximum ionization decreases with increase in latitude and NmF2 values during the equinoxes are higher than those of the solstice seasons, in the northern hemisphere. It is entirely different in the southern hemisphere. The rate of decay is faster during the solstice than during the equinoxes. Maximum hmF2 values occur at the equatorial ionosphere; the least is in the mid-latitude region. The time of formation and position of the EIA crests is observed to be asymmetric. It appears to be more consistent in the northern hemisphere than the south. These types of seasonal variations have been attributed to the daytime meridional wind, equatorial fountain effect and the location of the subsolar point in relation to the magnetic equator.


      PubDate: 2014-09-25T05:32:46Z
       
  • Influence of hadron and atmospheric models on computation of cosmic ray
           ionization in the atmosphere—Extension to heavy nuclei
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): A.L. Mishev , P.I.Y. Velinov
      In the last few years an essential progress in development of physical models for cosmic ray induced ionization in the atmosphere is achieved. The majority of these models are full target, i.e. based on Monte Carlo simulation of an electromagnetic-muon-nucleon cascade in the atmosphere. Basically, the contribution of proton nuclei is highlighted, i.e. the contribution of primary cosmic ray α-particles and heavy nuclei to the atmospheric ionization is neglected or scaled to protons. The development of cosmic ray induced atmospheric cascade is sensitive to the energy and mass of the primary cosmic ray particle. The largest uncertainties in Monte Carlo simulations of a cascade in the Earth atmosphere are due to assumed hadron interaction models, the so-called hadron generators. In the work presented here we compare the ionization yield functions Y for primary cosmic ray nuclei, such as α-particles, Oxygen and Iron nuclei, assuming different hadron interaction models. The computations are fulfilled with the CORSIKA 6.9 code using GHEISHA 2002, FLUKA 2011, UrQMD hadron generators for energy below 80GeV/nucleon and QGSJET II for energy above 80GeV/nucleon. The observed difference between hadron generators is widely discussed. The influence of different atmospheric parametrizations, namely US standard atmosphere, US standard atmosphere winter and summer profiles on ion production rate is studied. Assuming realistic primary cosmic ray mass composition, the ion production rate is obtained at several rigidity cut-offs – from 1GV (high latitudes) to 15GV (equatorial latitudes) using various hadron generators. The computations are compared with experimental data. A conclusion concerning the consistency of the hadron generators is stated.


      PubDate: 2014-09-25T05:32:46Z
       
  • Lidar observations of the middle atmospheric thermal structure over north
           China and comparisons with TIMED/SABER
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): Chuan Yue , Guotao Yang , Jihong Wang , Sai Guan , Lifang Du , Xuewu Cheng , Yong Yang
      According to the observational data for over 120 nights of the Rayleigh lidar located in Beijing, China (40.5°N, 116.2°E), the middle atmospheric thermal structure (35–85km) over North China was obtained. Lidar observation results show good agreements with SABER temperature data sets, which justify that both the two instruments are reliable. Lidar results show significant difference with the NRLMSISE-00 empirical model and lidar temperatures are usually colder than the model data during the observational time, which may be due to the associations of high level of solar activity, greenhouse gases and the frequent haze weather in North China. To characterize the seasonal variations of the atmospheric temperature structure over Beijing, the amplitude and phase profiles of the annual, semi-annual and 3-month sinusoidal oscillations were extracted by multi-parameter sinusoidal regression. A stratospheric temperature enhancement (STE) event and a long-term mesospheric temperature inversion layer (MIL) are observed in the early winter of 2012/2013. The observed STE event could be due to the enhancement of planetary wave (k=1) activity while the long-term MIL could be due to gravity wave-planetary wave interactions in the masopause region.


      PubDate: 2014-09-20T04:55:45Z
       
  • Validation and revision of far-field-current relationship for the
           lightning strike to electrically short objects
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): Qilin Zhang , Wenhao Hou , Tongtong Ji , Lixia He , Jianfeng Su
      In this paper we have validated and revised the general expressions for far-field-current factors presented by Bermudez et al. (2005, 2007) for lightning strike to tall objects on perfectly and finitely conducting ground, respectively. For the perfectly conducting ground, it is found that when the risetime of lightning return stroke current (RT) is larger than 5h/c (h is the height of tall object and c is the light speed), the overestimation caused by the traditional method predicting the lightning current peak is within 10% beyond a distance of 20km from the lightning channel, and with the decrease of observed horizontal distance d, the error will increase due to the effect of induction field component. For example, when d is 10km, the overestimation is about 20% for strike to a 300-m-tall object. For the finite conductivity ranging from 0.01S/m to 0.001S/m, when the lightning strikes the 300-m-tall object, the lightning current peak predicted from the measured magnetic field peak according to the traditional method is overestimated ranging from about +5% to +20% (positive means overestimation while negative means underestimation) and the derivation value is more within a distance of 20km because of induction field component; When the lightning strikes the 50-m-tall object, the predicted current peak according to the traditional method has an error ranging from about +5% to −15%.


      PubDate: 2014-09-20T04:55:45Z
       
  • A new South American network to study the atmospheric electric field and
           its variations related to geophysical phenomena
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): J. Tacza , J.-P. Raulin , E. Macotela , E. Norabuena , G. Fernandez , E. Correia , M.J. Rycroft , R.G. Harrison
      In this paper we present the capability of a new network of field mill sensors to monitor the atmospheric electric field at various locations in South America; we also show some early results. The main objective of the new network is to obtain the characteristic Universal Time diurnal curve of the atmospheric electric field in fair weather, known as the Carnegie curve. The Carnegie curve is closely related to the current sources flowing in the Global Atmospheric Electric Circuit so that another goal is the study of this relationship on various time scales (transient/monthly/seasonal/annual). Also, by operating this new network, we may also study departures of the Carnegie curve from its long term average value related to various solar, geophysical and atmospheric phenomena such as the solar cycle, solar flares and energetic charged particles, galactic cosmic rays, seismic activity and specific meteorological events. We then expect to have a better understanding of the influence of these phenomena on the Global Atmospheric Electric Circuit and its time-varying behavior.


      PubDate: 2014-09-20T04:55:45Z
       
  • Observations of the intraseasonal oscillations over two Brazilian low
           latitude stations: A comparative study
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): A. Guharay , P.P. Batista , B.R. Clemesha , R.A. Buriti
      A comparative study of intraseasonal oscillations (ISO) in the period range 20–110 days is carried out in the mesosphere and lower thermosphere (MLT) zonal wind at two low latitude stations, Cariri (7.4°S, 36.5°W) and Cachoeira Paulista (22.7°S, 45°W) located far from the convective anomaly region. Considerable seasonal and interannual variability is observed. The ISO in the MLT and lower atmosphere are found to be well correlated during winter and spring indicating a coupling of the atmospheric regions through the ISO. On the other hand, relatively less correlation during summer and fall may suggest a dominance of the in situ excitation of the ISO in the MLT relative to the lower atmospheric contribution. The correlation between the MLT and lower atmosphere is found to be a little higher at Cachoeira Paulista than Cariri. The ISO in the MLT shows good correlation between the two stations, but correlation is insignificant in the case of lower atmosphere. The ISO is most prominent in the upper troposphere, upper stratosphere and MLT. The waves responsible for communicating the ISO signature from the troposphere to the middle atmosphere in the tropics are believed to refract through mid-latitudes in course of their propagation. An evident height variation of the high amplitude ISO in the upper troposphere is observed with a clear annual oscillation at Cariri. The observed behaviors of the ISO at the present sites are discussed in the light of plausible physical mechanisms.


      PubDate: 2014-09-20T04:55:45Z
       
  • Physical mechanisms responsible for forming the 4-peak longitudinal
           structure of the 135.6nm ionospheric emission: First results from the
           Canadian IAM
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): O.V. Martynenko , V.I. Fomichev , K. Semeniuk , S.R. Beagley , W.E. Ward , J.C. McConnell , A.A. Namgaladze
      The Canadian Ionosphere and Atmosphere Model (Canadian IAM or C-IAM) is a new project aimed at the development of whole atmosphere modeling capabilities in Canada. The first version of the C-IAM is comprised of the extended Canadian Middle Atmosphere (CMAM) and the Murmansk's Upper Atmosphere Model (UAM), currently coupled in a one-way manner. The model extends from the surface to the inner magnetosphere and is able to describe the impact on the upper atmosphere and ionosphere of self-consistently generated lower atmosphere dynamical variability. In the current study, the C-IAM has been used to investigate the physical mechanisms responsible for forming the 4-peak longitudinal structure of the 135.6nm ionospheric emission observed by the IMAGE satellite over the tropics at 20:00 local time from March 20 to April 20, 2002. To perform this study, the C-IAM has been run for this whole observation period taking into account a realistic day-to-day variation in solar and geomagnetic activity. The 4-peak longitudinal structure produced by the model and averaged over the observation period is in a good agreement with the observations. Analysis of the model results suggests that the main mechanism for generating the longitudinal structure in the ionospheric emission after sunset is a modification of the ionospheric electric field in the E region caused in the course of the daytime by differences in the diurnal evolution of the zonal wind in different longitudinal sectors due to waves penetrating from the lower atmosphere. In agreement with the earlier findings, our study showed that this mechanism is driven mainly by the diurnal eastward propagating tide with zonal number 3. A small contribution to the formation of the 4-peak structure is also provided by longitudinal variations in meridional wind and neutral composition at the F2 layer altitudes. The 4 peaks being clearly visible in the monthly mean result are not, however, present every day. Day-to-day variability of both the diurnal wind evolution and geomagnetic activity can significantly modify the longitudinal structure of the ionospheric emission.


      PubDate: 2014-09-20T04:55:45Z
       
  • Long-term trends in the northern extratropical ozone laminae with focus on
           European stations
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): Jan Lastovicka , Peter Krizan , Michal Kozubek
      Narrow layers of substantially enhanced ozone concentration in ozonesonde-observed ozone profiles, called positive ozone laminae, reveal much stronger trend than the stratospheric and total ozone itself. They seem to be sensitive to both the ozone concentration and even more to changes in the stratospheric dynamics. We are studying long-term trends of strong positive laminae based on balloon-borne ozone sounding in Europe, Japan, North America and Arctic over 1970–2011 with focus on European stations due to their highest frequency of ozone sounding. Laminae characteristics exhibit strong negative trend till the mid-1990s (decrease by 50% or more). In more recent years this negative trend reverses to a positive trend. According to regression analysis, several factors play a role in the trend in laminae in Europe, namely NAO, EESC and the behavior of the winter polar stratospheric vortex represented here by the 10hPa polar temperature. On the other hand, several factors are found not to play a significant role in the long-term trend in laminae.


      PubDate: 2014-09-20T04:55:45Z
       
  • Statistics of ionospheric scintillation occurrence over European high
           latitudes
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): V. Sreeja , M. Aquino
      Rapid fluctuation in the amplitude and phase of transionospheric radio signals caused by small scale ionospheric plasma density irregularities is known as scintillation. Over the high latitudes, irregularities causing scintillation are associated with large scale plasma structures and scintillation occurrence is mainly enhanced during geomagnetic storms. This paper presents a statistical analysis of scintillation occurrence on GPS L1C/A signal at a high latitude station located in Bronnoysund (geographic latitude 65.5°N, geographic longitude 12.2°E; corrected geomagnetic (CGM) latitude 62.77°N), Norway, during the periods around the peaks of solar cycles 23 (2002–2003) and 24 (2011–2013). The analysis revealed that the scintillation occurrence at Bronnoysund during both the solar maximum periods maximises close to the midnight magnetic local time (MLT) sector. A higher occurrence of scintillation is observed on geomagnetically active days during both the solar maximum periods. The seasonal pattern of scintillation occurrence indicated peaks during the summer and equinoctial months. A comparison with the interplanetary magnetic field (IMF) components B y and B z showed an association of scintillation occurrence with the southward IMF B z conditions.


      PubDate: 2014-09-20T04:55:45Z
       
  • Estimation of the plasmasphere electron density and O+/H+ transition
           height from Irkutsk incoherent scatter data and GPS total electron content
           
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): B.G. Shpynev , D.S. Khabituev
      Observations obtained using the Irkutsk Incoherent Scatter Radar (ISR) and GPS Total Electron Content (TEC) were used for estimation of the O+/H+ transition level and electron density distribution in the upper topside ionosphere and in the plasmasphere. We use a modified Chapman function where O+/H+ transition level is one of parameters to develop a model. On the base of this model we consider some examples of O+/H+ transition height dynamics and estimate the uncertainty of the method. We show that the transition height dynamics is very sensitive to parameters of neutral wind and it has specific variation on Irkutsk ISR site. The plasmasphere can contribute more than 50% to GPS TEC, and the input from plasmasphere can produce significant influence on GPS TEC variations.


      PubDate: 2014-09-16T04:18:17Z
       
  • IFC-Ed. board
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119




      PubDate: 2014-09-16T04:18:17Z
       
  • Scattering and absorption characteristics of atmospheric aerosols over a
           semi-urban coastal environment
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): K. Aruna , T.V. Lakshmi Kumar , D. Narayana Rao , B.V. Krishna Murthy , S. Suresh Babu , K. Krishnamoorthy
      The scattering and absorption components of Aerosol Optical Depth (AOD) over a semi-urban coastal location (12.81°N, 80.03°E) near the mega city Chennai in peninsular India are separated using the collocated measurements of Black Carbon concentration and Atmospheric Boundary Layer Height (ABLH) from ERA Interim Reanalysis data assuming that most of the BC is contained and homogeneously mixed in the ABL. It is found that the absorption component to scattering component ratio has a strong seasonal variation with a pronounced maximum in the South West (SW) monsoon season. This is indicative of more effective wet removal of scattering aerosols than absorbing (BC) aerosols. There could also be an effect due to preferential removal of large particles which would have a lower content of BC. The Angstrom wavelength exponent shows a minimum in the SW monsoon season, the minimum being more pronounced for the scattering aerosols implying relative dominance of coarse mode particles. Investigation of the effect of Relative Humidity on scattering and absorption components of AOD revealed that the BC (absorbing) aerosols are non-hydrophilic/not coated with hydrophilic substance.


      PubDate: 2014-09-16T04:18:17Z
       
  • Corrigendum to “The occurrence of coronal holes during the sunspot
           cycle” [J. Atmos. Sol.–Terr. Phys. 113 (2014) 44–46]
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): H. Machiya , S.-I. Akasofu



      PubDate: 2014-09-16T04:18:17Z
       
  • Corrigendum to “On the alleged coherence between the global
           temperature and the sun's movement”
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Sverre Holm
      Corrections to Holm, On the alleged coherence between the global temperature and the sun's movement, J. Atmosph. Solar-Terres. Phys., April 2014.


      PubDate: 2014-09-16T04:18:17Z
       
  • Long-term variabilities and tendencies in zonal mean TIMED–SABER
           ozone and temperature in the middle atmosphere at 10–15°N
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): Oindrila Nath , S. Sridharan
      Long-term variabilities and trends of middle atmospheric (20–100km) ozone volume mixing ratio (OVMR) and temperature and their responses towards quasi-biennial oscillation (QBO), solar cycle (SC) and El Niño-southern oscillation (ENSO) have been investigated using monthly averaged zonal mean Sounding of Atmosphere by Broadband Emission Radiometry (SABER) observations at 10–15°N for the years 2002–2012. Composite monthly mean of OVMR shows semi-annual oscillation (SAO) predominantly in the lower stratosphere (20–30km) and in the upper mesosphere (above 90km), whereas that of temperature shows SAO in the upper stratosphere (45–55km) and lower mesosphere (60–75km). Amplitudes of SAO and annual oscillation (AO) in OVMR show enhancement above 80km and 90km respectively in the mesosphere and both show maximum around 30km in the stratosphere. The amplitudes of SAO and AO in temperature show maxima just below and above 80km in the mesosphere, whereas in the stratosphere, they show maxima around 40km and 20km respectively. The phase profiles of SAO and AO in temperature show downward progressions below 80km, whereas the phase profile of SAO in OVMR shows downward progression only below 40km and the phase remains constant above 80km. Regression analysis of OVMR shows increasing trend at 23km, and small decreasing trend at 30km, 34km and above 80km. Above 92km, the trend sharply decreases. OVMR response to QBO winds at 30hPa shows negative maxima at 30km and 91km, positive maximum at 26km and is insignificant at other heights. The OVMR response to SC is positive in the middle stratosphere peaking at 31km and in the upper mesosphere peaking at 95km. The OVMR response to ENSO shows mixed behavior in stratosphere and positive in the upper mesosphere. It is positive in the lower height region 20–27km with maximum at 25km. The response to ENSO is insignificant up to 70km and it is positive above 80km with two maxima at 87km and 97km. Regression analysis of temperature shows cooling trends in most of the stratosphere and the mesosphere (40–90km). The temperature response to SC is increasingly positive above 40km. The temperature response to ENSO is negative in the middle stratosphere and positive in the lower and upper stratosphere. In mesosphere, it is largely negative in the height range 60–80km and positive above 80km.


      PubDate: 2014-09-16T04:18:17Z
       
  • Ball lightning caused by a semi-relativistic runaway electron avalanche
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): Geron S. Paiva , Carlton A. Taft , Nelson C.C.P. Furtado , Marcos C. Carvalho , Eduardo N. Hering , Marcus Vinícius , F.L. Ronaldo Jr. , Neil M. De la Cruz
      Ball lightning (BL) is observed as a luminous sphere in regions of thunderstorm activity. There are many reports of BL forming in total absence of thunderclouds, associated with earthquakes and volcanoes. In this latter case, BL has been known to appear out of “nowhere”. In this work, a hypothesis on BL formation is presented involving the interaction between very low frequency (VLF) radio waves and atmospheric plasmas. High-velocity light balls are produced by ionic acoustic waves (IAWs) interacting with a stationary plasma. Several physical properties (color, velocity, and fragmentation) observed in the BL phenomenon can be explained through this model.


      PubDate: 2014-09-16T04:18:17Z
       
  • Vlasiator: First global hybrid-Vlasov simulations of Earth's foreshock and
           magnetosheath
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): S. von Alfthan , D. Pokhotelov , Y. Kempf , S. Hoilijoki , I. Honkonen , A. Sandroos , M. Palmroth
      We present results from a new hybrid-Vlasov simulation code, Vlasiator, designed for global magnetospheric simulations. Vlasiator represents ions by a six-dimensional distribution function propagated using a finite volume approach. The distribution functions are self-consistently coupled to electromagnetic fields with electrons modeled as a charge-neutralizing fluid. A novel sparse representation of the distribution function reduces the computational demands of the problem by up to two orders of magnitude. The capabilities of the code are demonstrated by reproducing characteristics of the ion/ion right-hand resonant beam instability, as well as key features of the collisionless bow shock and magnetosheath in front of the Earth's magnetosphere in global five-dimensional (two in ordinary space, three in velocity space) simulations. We find that Vlasiator reproduces the ion velocity distribution functions with quality comparable to spacecraft observations.


      PubDate: 2014-09-16T04:18:17Z
       
  • Vertical profile measurements of lower troposphere ionisation
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): R.G. Harrison , K.A. Nicoll , K.L. Aplin
      Vertical soundings of the atmospheric ion production rate have been obtained from Geiger counters integrated with conventional meteorological radiosondes. In launches made from Reading (UK) during 2013–2014, the Regener–Pfotzer ionisation maximum was at an altitude equivalent to a pressure of (63.1±2.4)hPa, or, expressed in terms of the local air density, (0.101±0.005)kgm−3. The measured ionisation profiles have been evaluated against the Usoskin–Kovaltsov model and, separately, surface neutron monitor data from Oulu. Model ionisation rates agree well with the observed cosmic ray ionisation below 20km altitude. Above 10km, the measured ionisation rates also correlate well with simultaneous neutron monitor data, although, consistently with previous work, measured variability at the ionisation maximum is greater than that found by the neutron monitor. However, in the lower atmosphere (below 5km altitude), agreement between the measurements and simultaneous neutron monitor data is poor. For studies of transient lower atmosphere phenomena associated with cosmic ray ionisation, this indicates the need for in situ ionisation measurements and improved lower atmosphere parameterisations.


      PubDate: 2014-09-11T03:24:26Z
       
  • Ionospheric effects of sudden stratospheric warmings in eastern Siberia
           region
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): A.S. Polyakova , M.A. Chernigovskaya , N.P. Perevalova
      Ionospheric effects observed in Russia's Asia region during sudden stratospheric warmings (SSWs) in the winters 2008/2009 and 2012/2013 corresponding to both extreme solar minimum and moderate solar maximum conditions have been examined. To detect the ionospheric effects which must have been induced by the SSWs, we have carried out a joint analysis of total electron content (TEC) global ionospheric maps (GIM), MLS (Microwave Limb Sounder, EOS Aura) measurements of vertical temperature profiles, as well as NCEP/NCAR and UKMO Reanalysis data. It has been revealed for the first time that during strong SSWs the amplitude of diurnal variation of TEC decreases nearly by half in the mid-latitude ionosphere. Besides, the intensity of TEC deviations from the background level increases during SSWs. It has also revealed that during SSW peak the midday TEC maximum considerably decreases, and the night/morning TEC increases compared to quiet days. The pattern of TEC response to SSW is shown to be identical for both quiet and disturbed geophysical conditions.


      PubDate: 2014-09-11T03:24:26Z
       
  • The effect of the Earth׳s optical shadow on thermal plasma
           measurements in the plasmasphere
    • Abstract: Publication date: December 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 120
      Author(s): G. Kotova , M. Verigin , V. Bezrukikh
      The data processing technique was developed for thermal plasma measurements by wide-angle plasma analyzers, which was successfully used for the Interball mission instruments. This technique considers the effect of spacecraft potential on plasma measurements. When the spacecraft enters the optical shadow of the Earth, the evaluated spacecraft potential suddenly drops, but no abrupt changes of plasma density or temperature are observed. Often observed decrease in temperature of protons in the Earth's shadow is actually associated with shading of ionospheric feet of magnetic field line passing through the spacecraft. This suggests that ionospheric photoelectrons are an important heat source for the plasmasphere. Besides, the Interball 1 data suggest that photoelectrons coming from the nearest ionosphere are more effective in plasmaspheric ion heating than photoelectrons from the conjugate hemisphere.


      PubDate: 2014-09-11T03:24:26Z
       
  • Second-order ionospheric effect on PPP over Hong Kong
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Shengyue Ji , Duojie Weng , Zhenjie Wang , Wu Chen , Wingshan Chan
      In the past few years, precise point positioning (PPP) has become an important positioning method for many practical applications. It is based on ionosphere-free carrier phase combination measurements, in which only first-order ionospheric error is removed. Past research has shown that high-order ionospheric effect can affect PPP performance. In this study, the effect of high-order ionospheric error, the second-order one, on PPP has been evaluated in Hong Kong, a low latitude area. First, a method regarding how to calculate second-order ionospheric error is introduced and the evaluation method is also discussed. After that, the numerical results are shown. Based on the results, it is found that the effect of the second-order ionospheric error on ionosphere-free carrier phase combination measurements reached up to the cm level in 2001 and the effect of the second-order ionospheric error on both kinematic and static PPP also reached the cm level. Further, it is also demonstrated that the effect of second-order ionospheric error on PPP is closely related to solar activity.


      PubDate: 2014-09-01T01:46:33Z
       
  • Solar and lunar ionospheric electrodynamic effects during stratospheric
           sudden warmings
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Yosuke Yamazaki
      Both solar and lunar atmospheric tides are believed to drive ionospheric electrodynamic effects during stratospheric sudden warmings (SSWs), but their relative importance is not well understood. In this study, long-term records (1958–2007) of the geomagnetic field are analyzed to determine the average solar (S) and lunar (L) ionospheric current systems for SSW and non-SSW periods. It is found that the L current intensity is enhanced during SSWs approximately by 75%, while the relative change in the S current intensity is much smaller (~10%). Nonetheless, absolute changes are comparable in the S and L current intensities. At the magnetic equator, semidiurnal perturbations produced by S and L currents reinforce or cancel each other depending on the phase of the moon, creating lunar-dependent recurrent onset in the total effect. These results indicate that both S and L contributions need to be considered to understand ionospheric variability during SSWs.


      PubDate: 2014-09-01T01:46:33Z
       
  • The structure of one-dimensional standing MHD waves in, and at the
           boundary of, the dayside plasmasphere
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Andrey Regenaldovich Polyakov
      Possibilities are demonstrated for finding the basic frequency of eigen-oscillations for various types of wave resonators by means of the amplitude and phase fluctuation correlation functions (APCF) method. The APCF method is based on the fact that in the isotropic resonators with arbitrary parametres of medium the interval between two neighbouring peaks of correlation functions of the oscillations in question is only determined by the first harmonic frequency of one of possible one-dimensional standing waves. In this work the APCF method is used for the first time for processing the real records of geomagnetic disturbances. For the oscillations recorded at “Borok” and “Mondy” geomagnetic observatories, the periods of the first harmonics of standing waves in the magnetospheric resonator were obtained. It was found that all typical magnitudes of these periods correspond to known modes of MHD oscillations in the plasmasphere and at its boundary.


      PubDate: 2014-09-01T01:46:33Z
       
  • Sporadic E tidal variabilities and characteristics observed with the
           Cyprus Digisonde
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Christina Oikonomou , Haris Haralambous , Christos Haldoupis , Chris Meek
      In this study, ionogram observations made with the Cyprus digisonde (35°N; 33°E) are analyzed by applying an ionosonde height–time–intensity (HTI) methodology. The aim is to study dominant periodicities and diurnal patterns in occurrence and altitude transport of sporadic E (Es) and intermediate descending layers (IDL), which are impacted upon by solar thermospheric tides via the windshear layer formation mechanism in the E and lower F region ionosphere. The results show the diurnal occurrence and altitude descent of sporadic E to be dominated by a semidiurnal tide-like periodicity, which prevails, with some differences, in all seasons. It is characterized by a daytime layer starting near sunrise at ~125km, followed by a nighttime layer appearing first in late afternoon at ~130km; both layers descend in altitude with speeds between about 2 and 3km/h, therefore reaching the 100km level in ~10–12h. Also, a terdiurnal tide-like periodicity is present in daily Es occurrence and altitude descent but only in summer solstice. In addition, the data show fast-descending layers to originate at F region altitudes near sunrise and sunset, which are subject to a semidiurnal periodicity. Although these layers are rarely seen by the digisonde below about 180km for most times and never during the night, the data hint that they connect with sporadic E layers below, therefore, both IDLs and Es form an integral tidal ion layer system in the lower ionosphere. An exceptional result is the detection during daytime of strong intermediate descending layers in March equinox, starting at F region and descending downwards with speeds of ~10km/h. Although an effort is made to interpret this equinoctial IDL signature, more work is needed for its understanding.


      PubDate: 2014-09-01T01:46:33Z
       
  • The lunar daily geomagnetic variation and its dependence on sunspot number
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Cengiz Çelik
      A detailed spherical harmonic model of the lunar daily geomagnetic variation, L, is presented and discussed. This model, which is based on a vastly greater data-set than hitherto, is compared to an earlier model of the solar daily geomagnetic variation, S, which is based on the same data. The dependence of L on sunspot number, as measured by the Wolf ratio, is found to be less than that of S by a factor of 2. It is confirmed that the dependence of S, L and E-region conductivity with sunspot cycle differ significantly from one another, casting doubt on that region as the principal location for the L and S dynamo currents.


      PubDate: 2014-09-01T01:46:33Z
       
  • Scattering cross section of mesospheric echoes and turbulence parameters
           from Gadanki radar observations
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): D. Selvaraj , A.K. Patra , H. Chandra , H.S.S. Sinha , U. Das
      We present a comprehensive study on radar scattering cross section of mesospheric echoes and mesospheric turbulence parameters based on several days of observations made during two rocket-radar campaigns, one in July 2004 and another in April 2005, meant for studying mesospheric turbulence. Radar scattering cross section was found to have large local time and day-to-day variability and was found to be as low as 3.1×10−18 m−1 and as high as 1×10−14 m−1 and the median values were in the range of 4.4×10−18–4.7×10−16 m−1. Echoes connected with the low value of scattering cross section could be detected only when a long pulse width was used. Turbulence parameters were found to vary remarkably with time of the day and also from one day to another. In July, the turbulent kinetic energy (TKE) dissipation rate, outer scale and inner scale were in the range of 0.08–150mW/kg, 33–1500m, and 1.9–50m, respectively, and their median values were in the range of 5–52mW/kg, 293–977m, and 2–31m, respectively. In April, these estimates were in the range of 0.9–69mW/kg, 38–1081m, and 4–21m, respectively, and their median values were in the range of 1–12mW/kg, 140–378m, and 8–13m, respectively. These parameters are found to agree quite well with those estimated from rocket-borne observations, which were in the range of 4–117mW/kg, 220–1475m, and 15–31m, respectively, in July and 2–36mW/kg, 170–680m, and 17–37m, respectively, in April. Interestingly, the inner and outer scales estimated using both radar and rocket observations agree exceedingly well with model values. These results are compared in detail with those reported from low, middle and high latitudes including model and discussed in the light of current knowledge of mesospheric turbulence.


      PubDate: 2014-09-01T01:46:33Z
       
  • Laboratory simulation of spontaneous breakup of polluted water drops in
           the horizontal electric field
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Rohini Bhalwankar , Subashini Subramanian , A.K. Kamra
      A laboratory simulation experiment to study the spontaneous breakup of distilled and polluted water drops suspended in horizontal electric field of 0, 100, 300, 500kVm−1 has been performed in a small vertical wind tunnel. Water drops are formed from distilled water and from 100ppm solution of ammonium sulfate and potassium nitrate. Results show that the life time of the both distilled and polluted water drops decreases with the increase in electric field. The water drops formed from both distilled and polluted water become more oblate as the electric field is increased. The results have been interpreted in terms of enhanced instability of water drops due to the changes in surface tension, viscosity, conductivity and hydro-dynamics of the water drop. Significance of the results is discussed in view of the possible modification of the drop size distribution and consequent growth of raindrops and lightning activity due to the combined effect of pollutants and electrical forces in clouds formed over big cities.


      PubDate: 2014-09-01T01:46:33Z
       
  • Eastward electrojet enhancements during substorm activity
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): M. D'Onofrio , N. Partamies , E. Tanskanen
      In this study, we use a semi-automatic routine to identify negative and positive bays in the IMAGE magnetometer data during seven months in 2003. The IMAGE stations have been divided into three latitude regions to monitor the time evolution and temporal relationship between the regions during substorms. In particular, we focus on the events where both positive and negative ground magnetic deflections are observed in different latitude regions. We found 101 events in total. We examine separately a subset of 32 events, for which the local electrojet index values are larger than the global ones, suggesting that the strongest activity at that time takes place within or very close to the local time sector of IMAGE. We systematically analyze the temporal difference and the intensity of the positive and negative bays. Our results show that the magnitude of the positive bay is on average about half of that of the negative bay. Two thirds of the positive bays within the IMAGE network peak earlier than the negative bays. Because the positive and negative bays occur meridionally very close together, we suggest that the enhancements of the westward current at the poleward part of the auroral oval and the eastward current within the return flow are very tightly coupled through field-aligned currents and closing horizontal currents. The substorm current system appears as a superposition on the large-scale current pattern in the vicinity of the evening sector shear flow region.


      PubDate: 2014-08-16T01:22:45Z
       
  • Large-amplitude ULF waves at high latitudes
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): T. Guido , B. Tulegenov , A.V. Streltsov
      We present results from the statistical study of ULF waves detected by the fluxgate magnetometer in Gakona, Alaska during several experimental campaigns conducted at the High Frequency Active Auroral Research Program (HAARP) facility in years 2011–2013. We analyzed frequencies of ULF waves recorded during 26 strongly disturbed geomagnetic events (substorms) and compared them with frequencies of ULF waves detected during magnetically quiet times. Our analysis demonstrates that the frequency of the waves carrying most of the power in almost all these events is less than 1mHz. We also analyzed data from the ACE satellite, measuring parameters of the solar wind in the L1 Lagrangian point between Earth and Sun, and found that in several occasions there is a strong correlation between oscillations of the magnetic field in the solar wind and oscillations detected on the ground. We also found several cases when there is no correlation between signals detected on ACE and on the ground. This finding suggests that these frequencies correspond to the fundamental eigenfrequency of the coupled magnetosphere–ionosphere system, and the amplitude of these waves can reach significant magnitude when the system is driven by the external driver (for example, the solar wind) with this particular frequency. When the frequency of the driver does not match the frequency of the system, the waves still are observed, but their amplitudes are much smaller.


      PubDate: 2014-08-11T00:53:27Z
       
  • Optical observations of meteors generating infrasound—I: Acoustic
           signal identification and phenomenology
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Elizabeth A. Silber , Peter G. Brown
      We analyse infrasound signals from 71 bright meteors/fireballs simultaneously detected by video to investigate the phenomenology and characteristics of meteor-generated near-field infrasound (<300km) and shock production. A taxonomy for meteor generated infrasound signal classification has been developed using the time–pressure signal of the infrasound arrivals. Based on the location along the meteor trail where the infrasound signal originates, we find most signals are associated with cylindrical shocks, with about a quarter of events evidencing spherical shocks associated with fragmentation episodes and optical flares. The video data indicate that all events with ray launch angles >117° from the trajectory heading are most likely generated by a spherical shock, while infrasound produced by the meteors with ray launch angles ≤117° can be attributed to both a cylindrical line source and a spherical shock. We find that meteors preferentially produce infrasound toward the end of their trails with a smaller number showing a preference for mid-trail production. Meteors producing multiple infrasound arrivals show a strong infrasound source height skewness to the end of trails and are much more likely to be associated with optical flares. We find that about 1% of all our optically-recorded meteors have associated detected infrasound and estimate that regional meteor infrasound events should occur on the order of once per week and dominate in numbers over infrasound associated with more energetic (but rarer) bolides. While a significant fraction of our meteors generating infrasound (~1/4 of single arrivals) are produced by fragmentation events, we find no instances where acoustic radiation is detectable more than about 60° beyond the ballistic regime at our meteoroid sizes (grams to tens of kilograms) emphasizing the strong anisotropy in acoustic radiation for meteors which are dominated by cylindrical line source geometry, even in the presence of fragmentation.


      PubDate: 2014-08-11T00:53:27Z
       
  • Artificial excitation of ELF waves with frequency of Schumann resonance
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): A.V. Streltsov , T. Guido , B. Tulegenov , J. Labenski , C.-L. Chang
      We report results from the experiment aimed at the artificial excitation of extremely low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance. Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the Earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range 7.8–8.0Hz when the ionosphere has a strong F layer, the frequency of the HF radiation is in the range 3.20–4.57MHz, and the electric field greater than 5mV/m is present in the ionosphere.


      PubDate: 2014-08-11T00:53:27Z
       
  • IFC-Ed. board
    • Abstract: Publication date: October 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 118, Part A




      PubDate: 2014-07-28T00:16:49Z
       
  • Preface to special issue: Mesospheric smoke and ice
    • Abstract: Publication date: October 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 118, Part B
      Author(s): Jorg Gumbel , Scott Robertson



      PubDate: 2014-07-28T00:16:49Z
       
  • Emissions of ionospheric Alfvén resonator and ionospheric conditions
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): A.S. Potapov , T.N. Polyushkina , B.V. Dovbnya , B. Tsegmed , R.A. Rakhmatulin
      We analyze continuous magnetic observations of ionospheric Alfvén resonator (IAR) emissions at mid-latitude observatory Mondy. The measurements were by a LEMI-30 search-coil magnetometer covering the period from March 2010 to May 2011. The results are compared with data from simultaneous ionospheric sounding data and International Reference Ionosphere (IRI-2012) model parameters. The large amount of observational data allowed us to inspect the daily and seasonal variations in some morphological characteristics of the emissions as well as their relationship to ionospheric conditions. The main factor affecting the duration of the emission is how long the lower ionosphere stays in Earth's shadow. We demonstrate a close inverse correlation between the diurnal and seasonal IAR frequency variations, on the one hand, and changes in the ionospheric critical frequency, f 0F2, on the other. Additionally, the expected emission frequency scale calculated with the IRI-2012 model is in good agreement with the values measured from the emission spectrograms.


      PubDate: 2014-07-28T00:16:49Z
       
  • IFC-Ed. board
    • Abstract: Publication date: October 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 118, Part B




      PubDate: 2014-07-28T00:16:49Z
       
  • Stratospheric and mesospheric concentric gravity waves over tropical
           cyclone Mahasen: Joint AIRS and VIIRS satellite observations
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Jia Yue , Steven D. Miller , Lars Hoffmann , William C. Straka III
      We report on the first simultaneous spaceborne observations of concentric gravity wave patterns in the stratosphere and mesosphere over the Indian Ocean excited by Tropical Cyclone Mahasen. On the nights of 13–14 May 2013, concentric ring patterns in nightglow were observed in close-proximity to Mahasen by the Day/Night Band (DNB) of the Visible/Infrared Imager/Radiometer Suite (VIIRS) on the Suomi NPP satellite. The waves exhibited horizontal wavelengths of 40–60km. On 13 May 2013, long concentric waves of ~500km wavelength were also seen west of India, far away (~1500km) from their estimated center near Mahasen. Concentric gravity waves in the stratosphere were observed nearly simultaneously by the Atmospheric Infrared Sounder on the Aqua satellite. These multi-level observations provide a clearer picture of the complex three-dimensional structure of tropical cyclone-generated gravity waves than a single instrument alone.


      PubDate: 2014-07-28T00:16:49Z
       
  • Traveling planetary wave activity from mesopause region airglow
           temperatures determined by the Network for the Detection of Mesospheric
           Change (NDMC)
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): E.R. Reisin , J. Scheer , M.E. Dyrland , F. Sigernes , C.S. Deehr , C. Schmidt , K. Höppner , M. Bittner , P.P. Ammosov , G.A. Gavrilyeva , J. Stegman , V.I. Perminov , A.I. Semenov , P. Knieling , R. Koppmann , K. Shiokawa , R.P. Lowe , M.J. López-González , E. Rodríguez , Y. Zhao , M.J. Taylor , R.A. Buriti , P.J. Espy , W.J.R. French , K.-U. Eichmann , J.P. Burrows , C. von Savigny
      The global distribution of traveling planetary wave (PW) activity in the mesopause region is estimated for the first time from ground-based airglow measurements. Monthly and total mean climatologies of PW power are determined from rotational temperatures measured at 19 sites from 78° N to 76° S which contribute to the Network for the Detection of Mesospheric Change (NDMC). Wave power is expressed as the standard deviation of nocturnal mean temperature around the seasonal temperature variation. The results from 20° N confirm the SABER traveling PW proxy by Offermann et al. (2009, J. Geophys. Res. 114, D06110) at two altitudes. Most sites between 69° S and 69° N show total mean traveling PW activity of about 6K, and only some high latitude sites have considerably higher activity levels. At the two tropical sites, there is practically no seasonal variation of PW activity. At 70% of the midlatitude sites, the seasonal variation is moderate for most of the year, but it is quite appreciable at all high latitude sites. Results about traveling PW activity at 87km and 95km available from several sites signal similar behavior at both altitudes. The total mean climatological results here obtained have further been used to separate the traveling PW contribution from the superposition of wave types contained in OH rotational temperature fluctuations measured by the SCIAMACHY instrument on Envisat. A narrow equatorial wave activity maximum is probably caused by gravity waves, while a tendency towards greater activity at higher northern latitudes may be due to stationary planetary waves.


      PubDate: 2014-07-28T00:16:49Z
       
  • Westward traveling planetary wave events in the lower thermosphere during
           solar minimum conditions simulated by SD-WACCM-X
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Fabrizio Sassi , Han-Li Liu
      We present numerical simulations with the Whole Atmosphere Community Climate Model, eXtended version (WACCM-X), whose dynamics is constrained by atmospheric specifications during recent and historical solar minimum conditions. The focus of this study is to describe how various dynamical conditions of boreal winter affect the dynamical behavior of the lower thermosphere (90–150km). The model simulations are carried out during solar minimum conditions and the results shown here discuss the period January 1–March 30 for five years (1995, 1996, 2008, 2009, and 2010). These years were selected because they include boreal winters without stratospheric warming (1995 and 1996), with modest or normal stratospheric warming (2008 and 2010), and with a large and persistent stratospheric warming (2009). The ultimate goal of this study is to encapsulate the statistically significant dynamical behavior due to westward propagating, planetary-scale waves (wavenumber 1 and wavenumber 2) in the lower thermosphere that are associated with different stratospheric conditions. To this end we show that the westward zonal acceleration above about 80km is by and large described by traveling waves with periods between 2 and 10 days. We show that the momentum carried by these waves is unlikely to affect directly the momentum budget of the extra-tropical lower thermosphere, where instead gravity-wave drag figures prominently. However, at the times leading to and following large stratospheric disturbances, we show prominent meridional propagation of wave activity from the mid-latitudes toward the tropics. In combination with strong eastward meridional wind shear, our results provide further evidence that such equatorward propagation of momentum in the lower thermosphere might influence the amplitude of equatorially trapped tides.


      PubDate: 2014-07-28T00:16:49Z
       
  • Comparative studies on ionospheric climatological features of NmF2 among
           the Arctic and Antarctic stations
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Sheng Xu , Bei-Chen Zhang , Rui-Yuan Liu , Li-Xin Guo , Ye-Wen Wu
      Climatological features of the maximum electron density of the ionospheric F2 region (NmF2) are investigated and compared among the Arctic and Antarctic stations using long-term observations from the dynasonde measurements at Tromso, the EISCAT Svalbard Radar (ESR) measurements at Longyearbyen, and the digisonde DPS-4 measurements at Zhongshan, Antarctica. The NmF2 data are sorted as monthly medians of NmF2 for each hour, month, and solar activity. Results are presented as follows: (1) On the diurnal variability, the maximum value of NmF2 mainly occurs at local noon at the auroral latitude station Tromso, but at magnetic noon at the cusp latitude station Longyearbyen and between local noon and magnetic noon at Zhongshan, indicating the importance of soft particle precipitation and ionospheric convection in the cusp region. (2) In addition to the daytime peak, there is another peak just before magnetic midnight at Longyearbyen in winter during solar maximum years, which is attributed to the cross-polar transport of EUV ionization from day side to night side. (3) An enhancement of NmF2 is detected at magnetic midnight in winter at Tromso. It may be caused by the nighttime substorms. (4) On the seasonal variability, there are semi-annual anomaly at Tromso and normal variability at both Longyearbyen and Zhongshan during solar minimum years. (5) During solar maximum years there is always semi-annual anomaly for all three stations. The well-known winter anomaly is evident at both Tromso and Zhongshan, but does not exist at Longyearbyen. These anomalies are mainly due to the differences in photoionization and chemical compositions between the three stations.


      PubDate: 2014-07-28T00:16:49Z
       
  • First results on forecasting the spatial occurrence pattern of L-band
           scintillation and its temporal evolution
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): R. Sridharan , Mala S. Bagiya , Surendra Sunda , Rajkumar Choudhary , Tarun K. Pant , Lijo Jose
      After a fairly successful attempt to forecast the temporal evolution of L-band scintillation over a given location, Trivandrum (8.5° N, 76.91° E, dip latitude 0.5° N) (Sridharan et al., 2012, J. Atmos. Sol. Terr. Phys. 80 230–238; Bagiya et al., 2014, J. Atmos. Sol. Terr. Phys. 110–111, 15–22), an attempt has been made here to generate the spatial–temporal maps of the occurrence pattern of L-band scintillation over the Indian region. To start with, the day time fluctuations in [f0F2]2 are used to forecast the temporal evolution of perturbations during the course of the night over Trivandrum. Similar to the earlier studies, here too it is taken that the electron density perturbations retain their characteristics throughout night and traverse with a uniform velocity. This implies that when the integrity of wave train of electron density perturbations is retained, any particular feature that passes over Trivandrum would have crossed over another location west of Trivandrum at an earlier time only dictated by the zonal velocity. With this assumption it becomes feasible to generate the probable spatial and temporal pattern of L-band scintillation. The consequences/limitations of the above assumptions are discussed in detail. The observed relation between the total duration of spread-F and the base height of the F-region (h'F) at 1930LT has been explained in terms of the favourable background neutral atmospheric conditions. Following Bagiya et al. (2013, J. Geophys. Res. 118, 1–8), the relation between h'F at 1930LT and the probable maximum latitudinal extent of the spread-F enables specification of the upper limit for the latitudes likely to be affected by the scintillation. It is believed that the presented results hold enough potential to generate the reliable L-band scintillation forecast maps and provide the necessary alerts to the satellite based air navigation users.


      PubDate: 2014-07-28T00:16:49Z
       
  • The scattering simulation of DSDs and the polarimetric radar rainfall
           algorithms at C-band frequency
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Tanvir Islam
      This study explores polarimetric radar rainfall algorithms at C-band frequency using a total of 162,415 1-min raindrop spectra from an extensive disdrometer dataset. Five different raindrop shape models have been tested to simulate polarimetric radar variables—the reflectivity factor (Z), differential reflectivity (Z dr ) and specific differential phase (K dp ), through the T-matrix microwave scattering approach. The polarimetric radar rainfall algorithms are developed in the form of R(Z), R(K dp ), R(Z, Z dr ) and R(Z dr , K dp ) combinations. Based on the best fitted raindrop spectra models rain rate retrieval information using disdrometer derived rain rate as a reference, the algorithms are further explored in view of stratiform and convective rain regimes. Finally, an “artificial” algorithm is proposed which considers the developed algorithms for stratiform and convective regimes and uses R(Z), R(K dp ) and R(Z, Z dr ) in different scenarios. The artificial algorithm is applied to and evaluated by the Thurnham C-band dual polarized radar data in 6 storm cases perceiving the rationalization in terms of rainfall retrieval accuracy as compared to the operational Marshall–Palmer algorithm (Z=200R 1.6). A dense network of 73 tipping bucket rain gauges is employed for the evaluation, and the result demonstrates that the artificial algorithm outperforms the Marshall–Palmer algorithm showing R 2=0.84 and MAE=0.82mm as opposed to R 2=0.79 and MAE=0.86mm respectively.


      PubDate: 2014-07-28T00:16:49Z
       
  • Plasma bubbles in the topside ionosphere: Estimations of the survival
           possibility
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): L.N. Sidorova , S.V. Filippov
      The question about the survival possibility and the life duration of the topside ionosphere equatorial spread F (ESF) plasma bubbles observed in the separate ion component (He+) is investigated. For this aim the main aeronomy processes, in which plasma bubbles and their He+ ions are involved, were under consideration. It was obtained that the main competition takes place between the He+ loss reactions (He+–N2 reaction) and the uplift during linear growth phase (~10min) of the Rayleigh–Taylor (R–T) instability, when the plasma bubbles are forming. It was revealed that the ambipolar diffusion of the He+ ions inside the plasma bubble is the fastest (~1–2min) in the altitude region up to 500km and becomes slower (~1h) above 500km. On the other hand, the plasma bubbles seen in He+ density are pretty stable structures against the cross-field (Bohm) diffusive collapse. It was concluded that the ESF plasma bubbles, reaching the “ceiling” heights, can exist for a night and several morning hours (~10–13h) and that there is a principal opportunity to observe them in the separate ion component (He+).


      PubDate: 2014-07-28T00:16:49Z
       
  • Comparison of H+ and He+ plasmapause locations based on the resurrected
           and reevaluated OGO-5 ion composition data base
    • Abstract: Publication date: November 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 119
      Author(s): Vladimír Truhlík , Ludmila Třísková , Robert F. Benson , Dieter Bilitza , Joseph Grebowsky , Phil G. Richards
      Orbiting Geophysical Observatory 5 (OGO 5) magnetospheric ion-composition data (H+, He+ and O+) have been retrieved from old magnetic tapes archived at the National Space Science Data Center (NSSDC). The highly compressed binary format was converted into a user-friendly ASCII format and these data have been made available online. We have inspected the reliability and consistency of this data set. Comparisons with the IRI-2012 climatological model and the FLIP theoretical model revealed a shift of absolute and relative ion densities with time. Here we have developed a correction procedure for the individual H+, He+ and O+ ion density measurements. We investigated plasmapause locations based on the density gradients in H+, and He+. The correlation coefficient between these locations was determined to be ~0.886 with the typical difference in L about 0.1. The electron density at the He+ plasmapause location based on the corrected data for all cases was >100cm−3.


      PubDate: 2014-07-28T00:16:49Z
       
  • Prefa Recent progress from networked studies based around MST radar
    • Abstract: Publication date: Available online 29 May 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Wayne K. Hocking , Volker Lehmann , Werner Singer , Masayuki Yamamoto



      PubDate: 2014-06-14T18:17:08Z
       
  • Hybrid model for long-term prediction of the ionospheric global TEC
    • Abstract: Publication date: Available online 24 May 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): P. Mukhtarov , D. Pancheva , B. Andonov
      A new hybrid climatological model for long-term prediction of the global TEC was developed. It is based on the global empirical background TEC model constructed by Mukhtarov et al. (2013a,b) and the availability of regularly/new observations from CODE TEC data. The cornerstone of the hybrid model consists of applying the method of autocorrelation prediction of the error and the respective correction of the background model with the predicted error. An important question is how the efficiency of the correction procedure depends on the given offset, i.e. the time distance between the dates for which the prediction is made to that with real data. It was found that the correction is really effective if the error prediction is made for a date with a distance up to 60 days from the date with real data. Then the RMSE decreases from 3.2 TECU (for the global background TEC model) to 2.76 TECU (for the hybrid model) which demonstrates the advantage of the presented in this paper hybrid model for long-term prediction with respect to the originally built background TEC model.


      PubDate: 2014-06-14T18:17:08Z
       
 
 
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