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  Subjects -> METEOROLOGY (Total: 84 journals)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 4)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 9)
Advances in Climate Change Research     Open Access  
Advances in Meteorology     Open Access   (Followers: 7)
Aeolian Research     Hybrid Journal   (Followers: 3)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 8)
American Journal of Climate Change     Open Access   (Followers: 7)
Asian Journal of Earth Sciences     Open Access   (Followers: 22)
Atmósfera     Open Access  
Atmosphere     Open Access   (Followers: 4)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 6)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 14)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 8)
Atmospheric Research     Hybrid Journal   (Followers: 21)
Atmospheric Science Letters     Hybrid Journal   (Followers: 9)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 10)
Bulletin of the American Meteorological Society     Open Access   (Followers: 16)
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: 17)
Climate Change Responses     Open Access  
Climate Dynamics     Hybrid Journal   (Followers: 15)
Climate law     Hybrid Journal   (Followers: 4)
Climate of the Past (CP)     Open Access   (Followers: 4)
Climate of the Past Discussions (CPD)     Open Access   (Followers: 2)
Climate Policy     Hybrid Journal   (Followers: 22)
Climate Risk Management     Open Access  
Climate Summary of South Africa     Full-text available via subscription  
Climatic Change     Hybrid Journal   (Followers: 33)
Current Climate Change Reports     Hybrid Journal  
Developments in Atmospheric Science     Full-text available via subscription   (Followers: 5)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 2)
Earth Perspectives - Transdisciplinarity Enabled     Open Access   (Followers: 1)
Energy & Environment     Full-text available via subscription   (Followers: 19)
Environmental and Climate Technologies     Open Access   (Followers: 2)
Global Meteorology     Open Access  
International Journal of Atmospheric Sciences     Open Access   (Followers: 4)
International Journal of Biometeorology     Hybrid Journal   (Followers: 1)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (Followers: 9)
International Journal of Climatology     Hybrid Journal   (Followers: 15)
International Journal of Image and Data Fusion     Hybrid Journal   (Followers: 1)
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (Followers: 10)
Journal of Atmospheric and Oceanic Technology     Full-text available via subscription   (Followers: 11)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 15)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 2)
Journal of Climate     Full-text available via subscription   (Followers: 29)
Journal of Climatology     Open Access   (Followers: 1)
Journal of Hydrology and Meteorology     Open Access   (Followers: 5)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 4)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Journal of Meteorology and Climate Science     Full-text available via subscription   (Followers: 1)
Journal of Space Weather and Space Climate     Open Access   (Followers: 4)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 27)
Journal of Weather Modification     Full-text available via subscription  
Large Marine Ecosystems     Full-text available via subscription  
Mathematics of Climate and Weather Forecasting     Open Access  
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: 5)
Mètode Science Studies Journal : Annual Review     Open Access  
Michigan Journal of Sustainability     Open Access  
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 2)
Monthly Notices of the Royal Astronomical Society Letters     Hybrid Journal   (Followers: 3)
Monthly Weather Review     Full-text available via subscription   (Followers: 13)
Nature Climate Change     Full-text available via subscription   (Followers: 44)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 18)
Open Journal of Modern Hydrology     Open Access   (Followers: 4)
Revista Brasileira de Meteorologia     Open Access   (Followers: 1)
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 5)
Space Weather     Full-text available via subscription   (Followers: 3)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 2)
Tellus A     Open Access   (Followers: 5)
Tellus B     Open Access   (Followers: 7)
The Cryosphere (TC)     Open Access   (Followers: 3)
The Cryosphere Discussions (TCD)     Open Access   (Followers: 2)
The Quarterly Journal of the Royal Meteorological Society     Hybrid Journal   (Followers: 8)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 4)
Weather     Hybrid Journal   (Followers: 3)
Weather and Climate Extremes     Open Access   (Followers: 2)
Weather and Forecasting     Full-text available via subscription   (Followers: 3)
Weatherwise     Hybrid Journal  
气候与环境研究     Full-text available via subscription   (Followers: 1)
Journal Cover   Journal of Atmospheric and Solar-Terrestrial Physics
  [SJR: 1.045]   [H-I: 61]   [15 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [2801 journals]
  • Modeling total solar irradiance from PMOD composite using feed-forward
           neural networks
    • Abstract: Publication date: December 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 135
      Author(s): A. Tebabal, B. Damtie, M. Nigussie, A. Bires, E. Yizengaw
      The variability of the solar activity dominates the variability of the earth's atmosphere, which affects human life and technology on earth. To understand the effects of solar activity on earth's atmosphere different efforts are underway to model the variations of total solar irradiance (TSI) associated to the variations of photometric sunspot index (PSI) and core to wing ratio of Mg II index, for example, linear regression approach. In this study, feed-forward neural networks (NNs) algorithm, which takes the non-linear relationship between the dependent and independent variables, has been implemented to model daily TSI using PSI and Mg II index. First, data between 1978 and 2008 have been used to train and validate NNs, through which the parameters such as weights and biases are estimated. Therefore, NNs has been used to predict TSI between the years 2008 and 2013 from test data. The output of NNs have been compared with PMOD composite TSI and result has shown good agreement. Linear correlation between NNs predicted TSI and PMOD composite is found to be about 0.9307 for the years between 1978 and 2013. This means that NNs predicted TSI from solar proxies explains about 86.6% of the variance of TSI for solar cycles 21–24, and over 90% during solar cycle 23. Predicting TSI using NNs further strengthens the view that surface magnetism indeed plays a dominant role in modulating solar irradiance.

      PubDate: 2015-11-23T13:00:31Z
  • Automatically identification of Equatorial Spread-F occurrence on
    • Abstract: Publication date: Available online 20 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Valdir Gil Pillat, Paulo Roberto Fagundes, Lamartine Nogueira Frutuoso Guimarães
      F-region large-scale irregularities, also called plasma bubbles, are one of the most interesting equatorial ionospheric phenomena. These irregularities are generated in the equatorial region and afterwards extend to lower latitudes. They are one of the important topics of investigation in equatorial ionosphere electrodynamics and, therefore, are subject to intense theoretical and experimental research. The ionosonde is the most used scientific equipment to study the ionosphere and the F-region. With advancement of digital ionosonde, it is now possible to carry out an ionospheric sounding with a cadence of 5 minutes or even with 1-minute cadence. To analyse a large amount of ionograms, more sophisticated tools are needed. Thus, development of algorithms to identify and analyse different aspects of ionograms has become very important to space science researchers. Multiple echoes recorded on ionograms are the signature of these irregularities in the ionograms, usually called Spread-F. Spread-F is classified into three types: range, frequency, and mixed. Thus, automatic identification of Spread-F is important in ionospheric studies, because studies usually involve the analysis and interpretation of large numbers of ionograms. The main objective of this paper is to present a new computational tool, based on fuzzy relation, designed to automatically identify the occurrence of Spread-F in ionograms. The test was conducted in ionograms recorded in the Brazilian sector (São José dos Campos (23.2°S, 45.9°W, dip latitude 17.6°S-low latitude) and Palmas (10.2°S, 48.2°W, dip latitude 5.5°S-near the magnetic equatorial)). The automatic identification of Spread-F occurrence was compared with those obtained manually and good agreement was found.

      PubDate: 2015-11-23T13:00:31Z
  • Vertical coupling between troposphere and lower ionosphere by electric
           currents and fields at equatorial latitudes
    • Abstract: Publication date: Available online 17 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): P.T. Tonev, P.I.Y. Velinov
      Thunderstorms play significant role in the upward electrical coupling between the troposphere and lower ionosphere by quasi-static (QS) electric fields generated by quiet conditions (by slow variations of electric charges), as well as during lightning discharges when they can be strong enough to produce in the nighttime lower ionosphere sprites. Changes are caused in lower ionosphere by the QS electric fields before a sprite-producing lightning discharge which can play role in formation of the stronger sprite-driving transient QS electric fields due to lightning. These changes include electron heating, modifications of conductivity and electron density, etc. We demonstrate that such changes depend on the geomagnetic latitude determining the magnetic field lines inclination, and thus, the anisotropic conductivity. Our previous results show that the QS electric fields in the lower ionosphere above equatorial thunderstorms are much bigger and have larger horizontal extension than those generated at high and middle altitudes by otherwise same conditions. Now we estimate by modeling the electric currents and fields generated in lower ionosphere above equatorial thunderstorms of different horizontal dimensions during quiet periods and of their self-consistent effects to conductivity whose modifications can play role in formation of post-lightning sprite-producing electric fields. Specific electric currents configurations and distributions of related electric fields are estimated first by ambient conductivity. Then, these are evaluated self-consistently with conductivity modification. The electric currents are re-oriented above ~85km and flow in a narrow horizontal layer where they dense. Respectively, the electric fields and their effect on conductivity have much larger horizontal scale than at middle latitudes (few hundred of kilometers). Horizontally large sources, such as mesoscale convective structures, cause enhancements of electric fields and their effects. These modified features may affect production of sprites.

      PubDate: 2015-11-23T13:00:31Z
  • Estimating ground-level neutron-flux enhancements in the extreme
           cosmic-ray events of the next 100, 1000 and 10000 years
    • Abstract: Publication date: Available online 17 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Paolo Mason
      Estimates are proposed of the enhancement in neutron flux which may be experienced at ground level in cosmic-ray events of extreme magnitude over the next century, millennium and ten millennia. The estimates are based on a points-over-threshold analysis of hourly neutron counts measured over the last decades by nine neutron-monitor stations located in Europe, North America and Antarctica. The present results are in good agreement with recent studies of extreme solar events based on the direct observation of flares and the abundance of cosmogenic nuclides in terrestrial and lunar archives.

      PubDate: 2015-11-23T13:00:31Z
  • Characteristics of cloud-to-ground lightning activity in hailstorms over
           Yunnan province
    • Abstract: Publication date: Available online 19 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Yiran Xie, Jian Wu, Xuetao Liu, Tengfei Zhang, Yinjian Xie, Yinjie Xu, Deming Zhao
      The characteristics of cloud-to-ground (CG) lightning for nine hailstorms in Yunnan province of China are analyzed statistically. It is determined that the hailstorms were found to present dominant negative CG lightning flashes at any given stage. One specific hailstorm occurring on July 16, 2006, is analyzed in detail by using the data from a CG lightning location network and Doppler radar. This severe hailstorm, which exhibited strong vertical development with cloud tops reaching 15.9km, produced hailstones as large as 15mm and had a lifespan of 3h and 12min. The total CG lightning within the hailstorm showed high levels of activity with flash rates of up to 79fl/5min. The analysis of the storm cell’s lifecycle shows similar trends between the CG lightning flash rates and radar-derived parameters. Cloud-to-ground flashes tended to initiate within the cloud region with reflectivity of more than 30 dBZ at the −10°C isotherm height. A distinct increase in CG flash rate is shown during the rapid development stages of hailstorms. The CG lightning jump pattern appears to be an effective tool for short-term forecasting of possible occurrences of severe weather.

      PubDate: 2015-11-23T13:00:31Z
  • Determination of instantaneous and daily net radiation from TM –
           Landsat 5 data in a subtropical watershed
    • Abstract: Publication date: December 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 135
      Author(s): Bernardo Barbosa da Silva, Susana Maria Gico Lima Montenegro, Vicente de Paulo Rodrigues da Silva, Humberto Ribeiro da Rocha, Josicleda Domiciano Galvíncio, Leidjane Maria Maciel de Oliveira
      Remote sensing makes it possible to identify the changes that occur on the surface of the Earth as a result of natural and/or man-made phenomena. Such changes impact on the net radiation at surface which in turn controls the Earth's climate. The present study aims to determine the impact of land use changes on net radiation at surface in a tropical watershed in Brazil, based on satellite images. The instantaneous net radiation (Rn,ins) (at the time of the satellite overpass) and the daily net radiation (Rn,24h) were both estimated by TM – Landsat 5 images and complementary weather data. The net radiation (Rn) estimated from remote sensing data was compared to the measurements taken from two micrometeorological towers located in the study area. Most Rn,ins values were found to be between 457.4Wm−2 and 760.0Wm−2 during the months with more intense solar radiation (February, March, and November), especially in the areas with more vegetation cover (sugarcane and eucalyptus plantations and areas with woody savanna vegetation, locally called Cerradão). The months with the highest thermal and radiative contrast (June and November) were selected to show the spatial distribution of the daily (Instantaneous) Rn, which ranged from 28.0 (420)Wm−2 to 98.0 (520)Wm−2 in June and from 83.0 (450)Wm−2 to 264.0 (800)Wm−2 in November 9. The model used to calculate Rn,24h provided values close to those taken at surface, even on days with higher cloud cover after the satellite overpass. The Mean Absolute Error (MAE), Mean Relative Error (MRE), and Root Mean Square Error (RMSE) associated with the Rn,24h computations in the sugar cane plantation were 8.3Wm−2, 8.4%, and 10.4Wm−2, respectively, confirming the applicability and accuracy of the results. The Rn patterns registered on the woody savanna throughout the year differ very much from those found in cropped areas, particularly in sugar cane plots. This may cause an impact on the watershed climate.

      PubDate: 2015-11-23T13:00:31Z
  • Modification of the high latitude ionosphere F region by X-mode powerful
           HF radio waves: Experimental results from multi-instrument diagnostics
    • Abstract: Publication date: December 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 135
      Author(s): N.F. Blagoveshchenskaya, T.D. Borisova, T.K. Yeoman, I. Häggström, A.S. Kalishin
      We present experimental results concentrating on a variety of phenomena in the high latitude ionosphere F2 layer induced by an extraordinary (X-mode) HF pump wave at high heater frequencies (f H=6.2–8.0MHz), depending on the pump frequency proximity to the ordinary and extraordinary mode critical frequencies, foF2 and fxF2. The experiments were carried out at the EISCAT HF heating facility with an effective radiated power of 450–650MW in October 2012 and October–November 2013. Their distinctive feature is a wide diapason of critical frequency changes, when the f H/foF2 ratio was varied through a wide range from 0.9 to 1.35. It provides both a proper comparison of X-mode HF-induced phenomena excited under different ratios of f H/foF2 and an estimation of the frequency range above foF2 in which such X-mode phenomena are still possible. It was shown that the HF-enhanced ion and plasma lines are excited above foF2 when the HF pump frequency is lying in range between the foF2 and fxF2, foF2≤f H≤fxF2, whereas small-scale field-aligned irregularities continued to be generated even when f H exceeded fxF2 by up to 1MHz and an X-polarized pump wave cannot be reflected from the ionosphere. Another parameter of importance is the magnetic zenith effect (HF beam/radar angle direction) which is typical for X-mode phenomena under f H/foF2 >1 as well as f H/foF2 ≤1. We have shown for the first time that an X-mode HF pump wave is able to generate strong narrowband spectral components in the SEE spectra (within 1kHz of pump frequency) in the ionosphere F region, which were recorded at distance of 1200km from the HF heating facility. The observed spectral lines can be associated with the ion acoustic, electrostatic ion cyclotron, and electrostatic ion cyclotron harmonic waves (otherwise known as neutralized ion Bernstein waves). The comparison between the O- and X-mode SEE spectra recorded at distance far from HF heating facility clearly demonstrated that variety of the narrowband spectral structures were only observed under X-mode HF pumping. The potential generation mechanisms of the different narrowband spectral components are discussed.

      PubDate: 2015-11-23T13:00:31Z
  • Decadal variability of upper ocean heat content in the Pacific: Responding
           to the 11-year solar cycle
    • Abstract: Publication date: Available online 23 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Gang Wang, Shuangxi Yan, Fangli Qiao
      Ocean heat content anomaly (OHCa) time series in some areas of the Pacific are significantly correlated with the total solar irradiance (TSI). Using the composite mean-difference method, we determined the mean response of OHCa in the upper-700m of the ocean to the TSI. Among the high solar response areas, we figure out two regions, one in the tropical mid-Pacific and the other in the western Pacific, where the OHCa present decadal variations, but different phases. The variation in phase of the solar response indicates that there exists an agency for the OHCa's response to TSI.

      PubDate: 2015-11-23T13:00:31Z
  • A terrestrial gamma-ray flash recorded at the Lightning Observatory in
           Gainesville, Florida
    • Abstract: Publication date: Available online 21 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M.D. Tran, V.A. Rakov, S. Mallick, J.R. Dwyer, A. Nag, S. Heckman
      A terrestrial gamma-ray flash (TGF) observed at ground level is presented. It was recorded at the Lightning Observatory in Gainesville, Florida, on June 13, 2014. Ground-based observations of TGFs are very rare. To date, only two positively identified ones are found in the literature. Our TGF was associated with a single-stroke negative cloud-to-ground discharge. It had a duration of 16 μ s and consisted of 6 pulses, two of which exceeded the upper measurement limit of 5.7MeV. The pulses apparently corresponded to individual photons, which is a characteristic feature of TGFs. The TGF began 191 μ s after the return-stroke electric field peak. The stepped leader duration was as short as 3.9ms. There was essentially no energetic radiation detected during the leader process. The NLDN-reported return-stroke peak current was as high as 224kA. The characteristics and occurrence context of the LOG-recorded TGF are compared to those of the two similar events found in the literature. In all three cases there was evidence of a channel carrying appreciable current to ground at the time of TGF, and the associated (preceding or concurrent) cloud-to-ground discharge processes were unusually intense.

      PubDate: 2015-11-23T13:00:31Z
  • Analysis of Synoptic Scale Controlling Factors in the Distribution of
           Gravity Wave Potential Energy
    • Abstract: Publication date: Available online 24 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Shih-Sian Yang, C.J. Pan, Uma Das, H.C. Lai
      In the past years, global morphology and climatology of gravity waves have been widely studied and the effects of topography and convection systems have been evaluated, but the complete gravity wave distribution could not be explained by these effects. To find the missing controlling factors, a series of synoptic scale analyses is performed in the present study to investigate relationships between synoptic scale factors and potential energy (Ep) associated with gravity waves. Global distribution of Ep during a 12-year period from 2002 to 2013 is derived using temperature profiles retrieved from observations of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. Synoptic scale factors obtained from ECMWF Interim reanalysis data are employed to investigate the correlation between synoptic systems and Ep. It is found that Ep values are high around extratropical cyclones over mid-latitudes (30°–60°) and around the Intertropical Convergence Zone (ITCZ) over low-latitudes (10°–30°). Ep values are low around subtropical highs over both mid- and low-latitudes. This is the first time that a synoptic scale analysis of Ep distribution is performed, and the influence of synoptic scale factors on Ep confirmed.

      PubDate: 2015-11-23T13:00:31Z
  • Local time variation of gravity wave momentum fluxes and their
           relationship with the tides derived from LIDAR measurements
    • Abstract: Publication date: Available online 25 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Ryan Agner, Alan Z. Liu
      Gravity waves and atmospheric tides have strong interactions in the mesopause region and are major contributors to the large variabilities in this region. How these two large perturbations interact with each other is not well understood. Wind and temperature measurements from a Na LIDAR at the Starfire Optical Range (35.0 N, 106.5 W), New Mexico from 24 nights between 1998 and 2000 are used to derive local time variations of gravity wave momentum flux and corresponding local time tidal variation of the background wind. The diurnal component of the momentum flux shows a clear modulation by the tide. The gravity wave forcing on the diurnal tidal amplitudes is shown to have an altitudinal and directional dependence.

      PubDate: 2015-11-23T13:00:31Z
  • Solar wind-atmospheric electricity-cloud microphysics connections to
           weather and climate
    • Abstract: Publication date: Available online 25 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Mai Mai Lam, Brian A. Tinsley
      We review recent research articles that present observations of the large-scale day-to-day dynamic tropospheric response to changes in the downward current density J z of the global atmospheric electric circuit (GEC). The evidence for the global circuit downward current density, J z , causing changes in atmospheric dynamics is now even stronger than as reviewed by Tinsley (2008) (Rep. Prog. Phys. 71, 066801). We consider proposed mechanisms for these responses, and suggest future directions for research.

      PubDate: 2015-11-23T13:00:31Z
  • Duct occurrence and characteristics for Bulgarian Black sea shore derived
           from ECMWF data
    • Abstract: Publication date: Available online 24 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): I. Sirkova
      Non-standard propagation due to sharp gradients in tropospheric refraction is known to have significant impact on radar and communication systems working in microwave range. The formation of tropospheric ducts is the most severe deviation from the standard propagation conditions. The presented study reports results on the tropospheric ducts’ occurrence and properties along the Bulgarian Black sea shore. The meteorology needed to reconstruct the refractivity profiles is derived from ECMWF current operational model, TL799L91, and refers to two-year period. Statistics of essential duct parameters for surface, surface-based and elevated ducts are reported for the summer months and overall duct statistics are given for the other seasons.

      PubDate: 2015-11-23T13:00:31Z
  • Annual Minimum Temperature Variations in Early 21st Century in Punjab,
    • Abstract: Publication date: Available online 30 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Misbah Jahangir, Syeda Maria Ali, Bushra Khalid
      Climate change is a key emerging threat to the global environment. It imposes long lasting impacts both at regional and national level. In the recent era, global warming and extreme temperatures have drawn great interest to the scientific community. As in a past century considerable increase in global surface temperatures have been observed and predictions revealed that it will continue in the future. In this regard, current study mainly focused on analysis of regional climatic change (annual minimum temperature trends and its correlation with land surface temperatures in the early 21st century in Punjab) for a period of 1979–2013. The projected model data European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) has been used for eight Tehsils of Punjab i.e., annual minimum temperatures and annual seasonal temperatures. Trend analysis of annual minimum and annual seasonal temperature in (Khushab, Noorpur, Sargodha, Bhalwal, Sahiwal, Shahpur, Sillanwali and Chinoit) tehsils of Punjab was carried out by Regression analysis and Mann-Kendall test. Landsat 5 Thematic Mapper (TM) data was used in comparison with Model data for the month of May from the years 2000, 2009 and 2010. Results showed that no significant trends were observed in annual minimum temperature. A significant change was observed in Noorpur, Bhalwal, Shahpur, Sillanwali, Sahiwal, Chinoit and Sargodha tehsils during spring season, which indicated that this particular season was a transient period of time.

      PubDate: 2015-11-23T13:00:31Z
  • The response of the ionosphere to intense geomagnetic storms in 2012 using
           GPS-TEC data from East Africa longitudinal sector
    • Abstract: Publication date: Available online 26 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): F. Tesema, B. Damtie, M. Nigussie
      The response of the ionosphere to intense magnetic storms has been studied using total electron content (TEC). TEC data recorded by series of GPS receivers at a longitude ∼ 35 ° E covering a wide range of latitudes ( 32 ° S to 68 ° N , geographic) is analyzed to study spatio-temporal modifications of the vertical TEC (vTEC) during storms on 07 and 09 March 2012 and on 14 July 2012. We have observed main phase positive response at equatorial ionisation anomaly (EIA) crests and mid latitude regions in all the storms. These main phase positive responses are associated with vertical drift enhancement (intensified equatorial electrojet (EEJ)) and the mechanical effect of equatorward neutral wind after an auroral activity. A daytime substantial depletion of TEC at low latitude region was observed on 08 March 2012. This is due to the combined effects of oversheilding and disturbance dynamo electric field that drive large downward drifts during the day. The low latitude and equatorial ionospheric response in the recovery phase days of March storm is found to be largely associated with the disturbance dynamo field that suppressed the upward E × B drift from EEJ observations. The summer negative and winter positive response in July storm as well as mid latitude positive response in March storm were associated with the composition changes as depicted by the O to N 2 ratio from GUVI measurements.

      PubDate: 2015-11-23T13:00:31Z
  • A Prototype Data Acquisition and Processing System for Schumann Resonance
    • Abstract: Publication date: Available online 3 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Giorgos Tatsis, Constantinos Votis, Vasilis Christofilakis, Panos Kostarakis, Vasilis Tritakis, Christos Repapis
      In this paper, a cost-effective prototype data acquisition system specifically designed for Schumann resonance measurements and an adequate signal processing method are described in detail. The implemented system captures the magnetic component of the Schumann resonance signal, using a magnetic antenna, at much higher sampling rates than the Nyquist rate for efficient signal improvement. In order to obtain the characteristics of the individual resonances of the SR spectrum a new and efficient software was developed. The processing techniques used in this software are analyzed thoroughly in the following. Evaluation of system's performance and operation is realized using preliminary measurements taken in the region of Northwest Greece.

      PubDate: 2015-11-23T13:00:31Z
  • IFC-Ed. board
    • Abstract: Publication date: November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 134

      PubDate: 2015-11-23T13:00:31Z
  • Validation of SARAL/AltiKa Significant Wave Height and Wind Speed
           observations over the North Indian Ocean
    • Abstract: Publication date: Available online 4 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): U. Mahesh Kumar, D. Swain, S.K. Sasamal, N. Narendra Reddy, T. Ramanjappa
      SARAL/AltiKa, a Ka-band altimetry joint mission of the Centre National d’Etudes Spatiales (CNES) and Indian Space Research Organisation (ISRO) was successfully launched on February 25, 2013. The main purpose of this mission is to explore the Ocean Surface Topography. As it is a Ka-band altimeter mission unlike other altimeters which were primarily in Ku-band, it is essential to calibrate and validate AltiKa data products before using the data for oceanographic applications. With this objective, two important geophysical parameters, Significant Wave Height (SWH) and Wind Speed (WS) from SARAL/AltiKa are inter-compared with those from 18 moored buoy stations in the North Indian Ocean (NIO) for a two year period from March 2013 to March 2015. SARAL/AltiKa GDR-T patch-2 version products are collocated with moored buoy observations with a collocation criteria of spatio-temporal window of 50km radius about the buoy location and 30 minutes time for all the altimeter measurements. Following this, linear regression relations are developed and statistical analyses carried out to assess the performance of SARAL/AltiKa. The correlation between SARAL/AltiKa derived SWHs and those from moored buoys is 0.98m with a bias of −0.02m and Root Mean Square Error (RMSE) of 0.15m at 95% confidence. The WSs derived from SARAL/AltiKa Ka-band correlates reasonably well with buoy observations with a correlation coefficient of 0.91, bias of −0.28m/s and RMSE of 1.13m/s. The inter-comparison results are found to be interesting with a good agreement between SARAL/AltiKa and moored buoys observations of SWH and WS in the NIO where SWHs are less than ∼4m and WS are less than ∼13m/s during the entire analysis period.

      PubDate: 2015-11-23T13:00:31Z
  • Atmospheric variability of methane over Pakistan, Afghanistan and
           adjoining areas using retrievals from SCIAMACHY/ENVISAT
    • Abstract: Publication date: Available online 4 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Zia ul-Haq, Salman Tariq, Muhammad Ali
      In the present work we have studied spatial and temporal variability of methane total column (MTC) over Pakistan and neighbouring regions of Afghanistan, India and Iran by using observations of SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) aboard EOS ENVISAT. Satellite measurements show large spatio-temporal variations in MTC over the study domain at different time scales. We find an average MTC of 1787±22ppb (annual average±standard deviation) with 3.7% (slope 7.14±1.28, y-intercept 1751±7.19, r=0.91) increase during the period of January 2003 to April 2012. An enhanced MTC is observed mostly over the Indo-Gangetic Plain and areas with high anthropogenic activities. MTC exhibits a seasonal peak of 1804±28ppb in summer followed by autumn (1800±25ppb) and winter (1777±24ppb). We have also discussed anthropogenic emission estimates in the study area obtained from EDGAR database. Substantial increments of 77% and 61% are observed in anthropogenic CH4 emissions for Pakistan and Afghanistan, respectively, during 1990 to 2008. Anthropogenic CH4 emissions from enteric fermentation and livestock sectors are found to be the highest. EDGAR data have also indentified megacity Lahore, Sukkur, megacity Karachi, Dera Ghazi Khan, megacity Delhi and Ahmedabad as large point sources of CH4 emissions in the region. The emissions from Karachi show the highest increase of 107%, while Lahore is found with the highest annual average emissions of 8.8×10−10 kgm−2 s−1.

      PubDate: 2015-11-23T13:00:31Z
  • Impact of the 15 Jan 2010 annular solar eclipse on the equatorial and low
           latitude ionosphere over the Indian region
    • Abstract: Publication date: Available online 7 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): S.K. Panda, S.S. Gedam, G. Rajaram, S. Sripathi, A. Bhaskar
      The annular solar eclipse of Jan 15, 2010 over southern India was studied with a multi-instrument network consisting of magnetometer, ionosonde and GPS receivers. The presence of a counter electrojet (weakened or westward zonal electric field) during the eclipse and adjacent days suggests the strong gravitational tidal effect associated with the exceptional Sun-Moon-Earth alignment around the eclipse day. With a strong backup of magnetometer recordings on the day of eclipse, its adjacent days and the normal electrojet day, it is argued that the regular eastward electric field for the whole day at the equator was not just weakened, but actually was flipped for several hours by the influence of enhanced lunar tides. The effect of flipping the electric field was clearly seen in the equatorial ionosonde data and through the large array of GPS receivers that produced the total electron content (TEC) data. The main impact of flipping the electric field was poor feeding of equatorial ionization anomaly (EIA) due to the severely weakened fountain effect on the eclipse day, with the regular anomaly crest shifting towards the equator. The equatorial ionosonde profile was also showing an enhanced F2 region peak in spite of a reduced vertical TEC. While the plasma density depletion at the lower F region altitude over the equator was due to the temporary lack of photo-ionization, the reductions in high altitude plasma density beyond the equator were caused by the electrodynamics taking place around the eclipse. The important finding of this analysis is that the electrodynamical consequences on the low latitude ionosphere were mainly due to combination of eclipse and lunar tides which were far more significant and influenced the EIA density rather than eclipse alone. Based on these findings, it is argued that prevailing lunar tidal impact also needs to be taken into account while seeking to understand the electrodynamical impact of the solar eclipse on the low latitude ionosphere.

      PubDate: 2015-11-23T13:00:31Z
  • A numerical study of aerosol effects on electrification of thunderstorms
    • Abstract: Publication date: Available online 10 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      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: 2015-11-23T13:00:31Z
  • Relationships between cloud-to-ground flashes and hydrometeors in a
           thunderstorm in Fujian province
    • Abstract: Publication date: Available online 10 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      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: 2015-11-23T13:00:31Z
  • On the dependence on solar cycle of the amplitude modulation
           characterizing the mid-latitude sporadic E layer diurnal periodicity
    • Abstract: Publication date: Available online 17 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M. Pezzopane, A. Pignalberi, M. Pietrella
      Spectral analyses are employed to investigate how the diurnal periodicity of the critical frequency of the sporadic E (Es) layer varies with solar activity. The study is based on ionograms recorded at the ionospheric station of Rome (41.8°N, 12.5°E), Italy, from 1976 to 2009, a period of time covering three solar cycles. It was confirmed that the diurnal periodicity is always affected by an amplitude modulation with periods of several days, which is the proof that Es layers are affected indirectly by planetary waves through their nonlinear interaction with atmospheric tides at lower altitudes. The most striking features coming out from this study is however that this amplitude modulation is greater for high solar activity than for low solar activity.

      PubDate: 2015-11-23T13:00:31Z
  • Spatial gravity wave characteristics obtained from multiple OH(3-1)
           airglow temperature time series
    • Abstract: Publication date: Available online 10 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Paul Wachter, Carsten Schmidt, Sabine Wüst, Michael Bittner
      We present a new approach for the detection of gravity waves in OH-airglow observations at the measurement site Oberpfaffenhofen (11.27°E, 48.08°N), Germany. The measurements were performed at the German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) during the period from February 4th, 2011 to July 6th, 2011. In this case study the observations were carried out by three identical Ground-based Infrared P-branch Spectrometers (GRIPS). These instruments provide OH(3-1) rotational temperature time series, which enable spatio-temporal investigations of gravity wave characteristics in the mesopause region. The instruments were aligned in such a way that their fields of view (FOV) formed an equilateral triangle in the OH-emission layer at a height of 87km. The Harmonic Analysis is applied in order to identify joint temperature oscillations in the three individual datasets. Dependent on the specific gravity wave activity in a single night, it is possible to detect up to four different wave patterns with this method. The values obtained for the waves’ periods and phases are then used to derive further parameters, such as horizontal wavelength, phase velocity and the direction of propagation. We identify systematic relationships between periods and amplitudes as well as between periods and horizontal wavelengths. A predominant propagation direction towards the East and North-North-East characterizes the waves during the observation period. There are also indications of seasonal effects in the temporal development of the horizontal wavelength and the phase velocity. During late winter and early spring the derived horizontal wavelengths and the phase velocities are smaller than in the subsequent period from early April to July 2011.

      PubDate: 2015-11-23T13:00:31Z
  • Elevated aerosols and role of circulation parameters in aerosol vertical
    • Abstract: Publication date: Available online 18 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): S.S. Prijith, Marina Aloysius, Mannil Mohan, P.V.N. Rao
      The study examines aerosol loading in different vertical layers of the atmosphere and explores the role of atmospheric circulation parameters in vertical distribution of aerosols and in its seasonal variability. Aerosol vertical distribution over the globe is examined, using long term satellite observations, by considering aerosol loading in different layers of atmosphere upto ∼6km altitudes from surface and fractional contribution of each of these layers to total columnar aerosol loading. Aerosols are observed residing close to the surface in most of the oceanic environments, except over certain regions which are in the close proximity of continents where upper level winds are conducive for long range aerosol transport. In contrast, considerable vertical spread in aerosol distribution with strong seasonal variability, minimum occurring in winter months and maximum in summer, is observed over the continental regions. Vertical spread in aerosol distribution is observed highest over north eastern and north western parts of Africa during northern hemispheric summer, when the convection activity peaks over these regions due to large solar insolation and associated surface heating. Seasonal variation of aerosol vertical spread over both of these regions is observed in phase with variation in atmospheric convergence and vorticity. During summer months, when the aerosol vertical spread is highest, strong surface level convergence and associated cyclonic vorticity is observed along with an upper level (700 to 600hPa) divergence. The surface level convergence and upper level divergence together induce an upward flow of air which carries aerosols from ground to higher altitudes. This mechanism of aerosol vertical transport is further corroborated through the correlation and regression relations of surface convergence/vorticity with aerosol loading above different elevations and hence the study reveals role of circulation parameters in aerosol vertical distribution.

      PubDate: 2015-11-23T13:00:31Z
  • Producing K indices by the interactive method based on the traditional
           hand-scaling methodology – preliminary results
    • Abstract: Publication date: Available online 17 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Fridrich Valach, Magdaléna Váczyová, Miloš Revallo
      This paper reports on an interactive computer method for producing K indices. The method is based on the traditional hand-scaling methodology that had been practised at Hurbanovo Geomagnetic Observatory till the end of 1997. Here, the performance of the method was tested on the data of the Kakioka Magnetic Observatory. We have found that in some ranges of the K-index values our method might be a beneficial supplement to the computer-based methods approved and endorsed by IAGA. This result was achieved for both very low (K=0) and high ( K ≥ 5 ) levels of the geomagnetic activity. The method incorporated an interactive procedure of selecting quiet days by a human operator (observer). This introduces a certain amount of subjectivity, similarly as the traditional hand-scaling method.

      PubDate: 2015-11-23T13:00:31Z
  • Characteristics of Total Electron Content (TEC) observed from a chain of
           stations near the northern crest of the Equatorial Ionization Anomaly
           (EIA) along 88.5°E meridian in India
    • Abstract: Publication date: Available online 19 November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): K.S. Paul, A. Das, S. Ray, A. Paul
      The equatorial ionosphere presents some of the highest TEC values in the world coupled with observations of periodic structures. Total Electron Content (TEC) and scintillation data were analyzed from a chain of stations Calcutta (22.58°N, 88.38°E geographic; 32°N magnetic dip), Baharampore (24.09°N, 88.25°E geographic; 35°N magnetic dip) and Farakka (24.79°N, 87.89°E geographic; 36.04°N magnetic dip) situated almost same meridian (88.5°E) during September 2011 and March-April 2012 for elevation greater than 20° so that the ionosphere can be tracked from the 15.50°N south of Calcutta to 31.80°N north of Farakka. Periodic variation of TEC was noticed before TEC bite out, predominantly within a particular latitudinal swath (19°N ‒26°N) along 88.5°E meridian. No periodic structures were observed over the magnetic equator during the observation period on ionosonde records from the magnetic equator station Trivandrum and COSMIC, GRACE and C/NOFS electron density measurements. The present paper reports, perhaps for the first time from the Indian longitude sector, confinement of such periodic structures in TEC primarily within a latitude swath of 19.00°N to 26.00°N almost along the same longitude of 88.5°E.

      PubDate: 2015-11-23T13:00:31Z
  • Knee model: Comparison between heuristic and rigorous solutions for the
           Schumann resonance problem
    • Abstract: Publication date: December 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 135
      Author(s): Yu.P. Galuk, A.P. Nickolaenko, M. Hayakawa
      Rapid development of computers allows for application of the direct numerical solution of the global electromagnetic resonance problem in the Earth-ionosphere cavity. Direct numerical solutions exploit the cavity models with the given conductivity profile of atmosphere such as exponential or the knee profiles. These profiles are usually derived from the knee model by Mushtak and Williams (2002) developed for obtaining the realistic ELF propagation constant. It is usually forgotten that profiles of the knee model are only a convenient approximate interpretation for the heuristic relations used in computations. We demonstrate that the rigorous full wave solution of the electromagnetic problem for such profiles deviates from that obtained in the knee model. Therefore the direct numerical solutions must also depart from the heuristic one. We evaluate deviations of the heuristic knee model data from those pertinent to equivalent profile of atmospheric conductivity.

      PubDate: 2015-11-23T13:00:31Z
  • Predicting the maximum amplitude of solar cycle 25 and its timing
    • Abstract: Publication date: December 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 135
      Author(s): K.J. Li, W. Feng, F.Y. Li
      Some classical statistical relations among feature parameters of solar cycle profiles are utilized to predict the maximum amplitude of the next upcoming solar cycle and its timing. Resultantly, cycle 25 should start in November 2019 and have its maximum amplitude of 109.1 in October 2023, being a moderate solar activity cycle.

      PubDate: 2015-11-23T13:00:31Z
  • A neural network based error correction method for radio occultation
           electron density retrieval
    • Abstract: Publication date: December 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 135
      Author(s): Viet-Cuong Pham, Jyh-Ching Juang
      Abel inversion techniques have been widely employed to retrieve electron density profiles (EDPs) from radio occultation (RO) measurements, which are available by observing Global Navigation Satellite System (GNSS) satellites from low-earth-orbit (LEO) satellites. It is well known that the ordinary Abel inversion might introduce errors in the retrieval of EDPs when the spherical symmetry assumption is violated. The error, however, is case-dependent; therefore it is desirable to associate an error index or correction coefficient with respect to each retrieved EDP. Several error indices have been proposed but they only deal with electron density at the F2 peak and suffer from some drawbacks. In this paper we propose an artificial neural network (ANN) based error correction method for EDPs obtained by the ordinary Abel inversion. The ANN is first trained to learn the relationship between vertical total electron content (TEC) measurements and retrieval errors at the F2 peak, 220km and 110km altitudes; correction coefficients are then estimated to correct the retrieved EDPs at these three altitudes. Experiments using the NeQuick2 model and real FORMOSAT-3/COSMIC RO geometry show that the proposed method outperforms existing ones. Real incoherent scatter radar (ISR) measurements at the Jicamarca Radio Observatory and the global TEC map provided by the International GNSS Service (IGS) are also used to valid the proposed method.

      PubDate: 2015-11-23T13:00:31Z
  • Electric discharges produced by clouds of charged water droplets in the
           presence of moving conducting object
    • Abstract: Publication date: December 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 135
      Author(s): Alexander Y. Kostinskiy, Vladimir S. Syssoev, Eugene A. Mareev, Vladimir A. Rakov, Mikhail G. Andreev, Nikolai A. Bogatov, Leonid M. Makal’sky, Dmitry I. Sukharevsky, Alexander S. Aleshchenko, Vladimir E. Kuznetsov, Maria V. Shatalina
      The possibility of initiation of electric discharges by a crossbow bolt (projectile) moving in the electric field of a cloud of negatively charged water droplets has been demonstrated for the first time. Over one hundred of discharges have been produced. For each event, a high-speed video camera recorded the images of upward positive leaders developing from both the nearby grounded sphere and the projectile, followed by the return-stroke-like process. Corresponding currents were measured and integrated photos of the events were obtained. The results can help to improve our understanding of lightning initiation by airborne vehicles and by a vertical conductor rapidly extended below the thundercloud in order to trigger lightning with the rocket-and-wire technique.

      PubDate: 2015-11-23T13:00:31Z
  • On the possible role of zonal dynamics in the formation and evolution of
           F3 layers over equator
    • Abstract: Publication date: November 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 134
      Author(s): N. Mridula, Tarun Kumar Pant
      In the present study, occurrences of F3 layer over Thiruvananthapuram (8.5°N; 77°E; dip latitude ~0.5°N), a dip equatorial station in India have been investigated using ionosonde data for the years 2004–2007. The F3 layers appearing in the ionograms during the pre noon hours only have been included in the analysis. The result indicates that a weak EIA resulting in low ionospheric height and high ionization density prevails before the occurrence of F3 layer and serves as an essential condition for its occurrence. The relative Slant Total Electron Content (rSTEC) measured using collocated ground based coherent low earth orbiting (LEO) radio beacon receiver has also been used along with electron densities measured by CHAMP satellite for the year 2006 and 2007 to illustrate this difference in the evolution of Equatorial Ionization Anomaly (EIA) on F3 and non F3 days. A new mechanism for F3 generation has been proposed. It has been shown that the coupling of the thermospheric zonal wind jet over equator and enhanced ionospheric density at lower heights over Indian longitude can account for the generation of F3 layer through ion-drag. The vertical wind associated with the thermospheric heating resulting from ion-drag causes the generation of an additional eastward field which, along with the prevailing F-region electric field, leads to the upward excursion of the F3 layer.

      PubDate: 2015-10-11T15:57:06Z
  • The inter-annual distribution of cloudless days and nights in Abastumani:
           Coupling with cosmic factors and climate change
    • Abstract: Publication date: Available online 9 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): G.G. Didebulidze, M. Todua
      We examined inter-annual variations and long-term trends of cloudless days (CD) and cloudless nights (CN) in 1957–1993 from Abastumani (41.75N, 42.82E), at different geomagnetic conditions and corresponding galactic cosmic rays (GCRs) flux changes. It showed possible influence of cosmic factors on cloud covering processes and, thus, climate change. It was demonstrated that (1) the inter-annual distribution of monthly mean values of planetary geomagnetic index Ap (for low and moderate disturbances) at CDs can be described by harmonic function with semiannual (with sharp maxima in March and September) and annual (with maximum in August) periodicities; (2) the inter-annual distribution of Ap index for CN has an additional maximum in June, where the largest decrease of GCR flux is observed. This phenomenon is expressed even stronger during Sudden Storm Commencement (SSC) events and strong geomagnetic disturbances (Ap≥50), when their relative numbers are the greatest and are accompanied by bigger reduction of GCRs flux; (3) the long-term trends of mean annual and mean seasonal values of Ap index and GCRs flux at CD and CN are estimated. It was detected that, for the latitudes of this region, long-term decreases (negative trends) of seasonal GCR flux are different at CD and CN, which could affect the radiative balance at the Earth's surface and, as a result, contribute to the climate change.

      PubDate: 2015-10-11T15:57:06Z
  • A case study of multi-annual temperature oscillations in the atmosphere:
           Middle Europe
    • Abstract: Publication date: Available online 9 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): D. Offermann, O. Goussev, Ch. Kalicinsky, R. Koppmann, K. Matthes, H. Schmidt, W. Steinbrecht, J. Wintel
      SABER temperature measurements from 2002 to 2012 are analyzed from 18 to 110km altitude in Middle Europe. Data are complemented by radiosonde measurements in the altitude range from 0 to 30km. Low frequency oscillations with periods of about 2.4-2.2 yr, 3.4 yr, and 5.5 yr are seen in either data set. Surprising vertical structures in amplitudes and phases are observed with alternating minima and maxima of amplitudes, steep phase changes (180°) at the altitudes of the minima, and constant phase values in between. HAMMONIA CCM simulations driven by boundary conditions for the years 1996 to 2006 are analyzed for corresponding features, and very similar structures are found. Data from another CCM, the CESM-WACCM model, are also analyzed and show comparable results. Similar oscillation periods have been reported in the literature for the ocean. A possible forcing of the atmospheric oscillations from below was therefore tested with a special HAMMONIA run. Here, climatological boundary conditions were used, i.e. the boundaries in all eleven years were the same. Surprisingly also in this data set the same atmospheric oscillations are obtained. We therefore conclude that the oscillations are intrinsically forced, self-sustained in the atmosphere. The oscillations turned out to be quite robust as they are still found in a HAMMONIA run with strongly reduced vertical resolution. Here only the form of the vertical amplitude and phase profile of the 2.2 yr feature is lost but the oscillation itself is still there, and the two other oscillations are essentially unchanged. Similar oscillations are seen in the earth surface temperatures. Global Land Ocean Temperature Index data (GLOTI) reaching back to 1880 show such oscillations during all that time. The oscillations are also seen in parameters other than atmospheric temperature. They are found in surface data such as the North Atlantic Oscillation Index (NAO) and in zonal winds in the troposphere and lower stratosphere. The oscillations found are tentatively discussed in terms (of synchronization) of self-sustained non-linear oscillators, as many of their properties resemble such oscillators described in the literature.

      PubDate: 2015-10-11T15:57:06Z
  • Hemispheric differences in the response of the upper atmosphere to the
           August 2011 geomagnetic storm: a simulation study
    • Abstract: Publication date: Available online 9 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Erdal Yiğit, Harald U. Frey, Mark B. Moldwin, Thomas J. Immel, Aaron J. Ridley
      Using a three-dimensional nonhydrostatic general circulation model, we investigate the response of the thermosphere-ionosphere system to the 5–6 August 2011 major geomagnetic storm. The model is driven by measured storm-time input data of the Interplanetary Magnetic Field (IMF), solar activity, and auroral activity. Simulations for quiet steady conditions over the same period are performed as well in order to assess the response of the neutral and plasma parameters to the storm. During the storm, the high-latitude mean ion flows are enhanced by up to 150–180%. Largest ion flows are found in the main phase of the storm. Overall, the global mean neutral temperature increases by up to 15%, while the maximum thermal response is higher in the winter Southern Hemisphere at high-latitudes than the summer Northern Hemisphere: 40% vs. 20% increase in high-latitude mean temperature, respectively. The global mean Joule heating increases by more than a factor of three. There are distinct hemispheric differences in the magnitude and morphology of the horizontal ion flows and thermospheric flows during the different phases of the storm. The largest hemispheric difference in the thermospheric circulation is found during the main and recovery phases of the storm, demonstrating appreciable geographical variations.The advective forcing is found to contribute to the modeled hemispheric differences.

      PubDate: 2015-10-11T15:57:06Z
  • Far-field coseismic ionospheric Disturbances of Tohoku earthquake
    • Abstract: Publication date: Available online 9 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): V.M. Krasnov, Ya.V. Drobzheva, J. Chum
      A computer code has been developed to simulate the generation of infrasonic waves by a strong earthquake at a distance of 9000km from the epicenter, their propagation through the atmosphere and their effects in the ionosphere. We provide estimates of the perturbations in the ionosphere at the height (210–220km) where radiowaves at the sounding frequency (3.595MHz) of a continuous Doppler radar reflect. Ionospheric perturbations have a global character and amplitudes of 1.5%-7.5% of ambient value. Perturbations exist for ~1hour. The form of calculated ionospheric disturbances coincides with the experimental results. The correlation coefficient between calculated and experimental forms was from 0.68 to 0.9.

      PubDate: 2015-10-11T15:57:06Z
  • TEC variation during High and low solar activities OVER SOuth american
    • Abstract: Publication date: Available online 9 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): O.F. Jonah, E.R. de Paula, M.T.A.H. Muella, S.L.G. Dutra, E.A. Kherani, P.M.S. Negreti, Y. Otsuka
      Using dual frequency GPS receivers in the South American sector, the measurement of absolute ionospheric Total Electron Content (TEC) has been estimated applying the Nagoya ionospheric model for both the years of 2009 and 2001, which represent low and high solar activities, respectively. The diurnal, day-to-day, monthly, seasonal, latitudinal and longitudinal variations of TEC were studied for equatorial and low latitude regions of South America. The strength and characteristics of the Equatorial Ionization Anomaly (EIA) were equally analyzed. The analyses reveal the diurnal, seasonal and semidiurnal TEC variation, as well as the nighttime variability during the low and high solar activities. Wavelet power spectra analysis was employed to check the periodicities of the TEC data, F10.7 and zonal and meridional wind velocities measured by Meteor radar at ∼100km altitude. Periods such as 27, 16, 8-10, 1-5 days were found to be dominant in the zonal and meridional wind velocity corresponding with those of TEC periodicities. Hence, besides the solar radiation, we suggest that there are contributions of tides and planetary waves in spatial and temporal TEC enhancement and variations during the geomagnetic quiet periods of both solar activities.

      PubDate: 2015-10-11T15:57:06Z
  • Lightning and middle atmospheric discharges in the atmosphere
    • Abstract: Publication date: Available online 5 October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Devendraa Siingh, R.P. Singh, Sarvan Kumar, T. Dharmaraj, Abhay K. Singh, Ashok K. Singh, M.N. Patil, Shubha Singh
      Recent development in lightning discharges including transient luminous events (TLEs) and global electric circuit are discussed. Role of solar activity, convective available potential energy, surface temperature and difference of land-ocean surfaces on convection process are discussed. Different processes of discharge initiation are discussed. Events like sprites and halos are caused by the upward quasi-electrostatic fields associated with intense cloud-to-ground discharges while jets (blue starter, blue jet, gigantic jet) are caused by charge imbalance in thunderstorm during lightning discharges but they are not associated with a particular discharge flash. Elves are generated by the electromagnetic pulse radiated during lightning discharges. The present understanding of global electric circuit is also reviewed. Relation between lightning activity/global electric circuit and climate is discussed.

      PubDate: 2015-10-08T17:41:04Z
  • Dynamics of plasma density perturbations in the upper ionosphere and the
           magnetosphere under the action of powerful HF radio waves
    • Abstract: Publication date: Available online 30 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): N. Borisov, N. Ryabova, Yu. Ruzhin
      Dynamics of the density perturbations of the main plasma components (electrons, oxygen and hydrogen ions) in the upper ionosphere and the magnetosphere under the action of powerful HF radio waves is discussed theoretically and numerically. For finite heating pulse and different effective powers the variations of the density perturbations in time at various heights are investigated. We argue that due to collisionless damping the magnetospheric duct along the whole field line is not formed. Instead positive and negative perturbations of the main plasma components propagating with the attenuation in the magnetosphere with two different speeds are predicted. Utilization of pulsed heating provides significant information concerning plasma perturbations in the upper ionosphere and the magnetosphere.

      PubDate: 2015-10-04T17:18:56Z
  • IFC-Ed. board
    • Abstract: Publication date: October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 133

      PubDate: 2015-09-30T17:06:20Z
  • Nonlinear acoustic-gravity waves and dust particle redistribution in
           earth's atmosphere
    • Abstract: Publication date: Available online 25 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Yu. N. Izvekova, S.I. Popel, B.B. Chen
      A continuously stratified model of nonadiabatic terrestrial atmosphere with taking into account the temperature profile is developed to study a possibility of instability development of acoustic-gravity (AG-) waves. It is shown that the existence of the regions in the atmosphere where the instability conditions are satisfied is due to the cooperation of thermal flow of solar radiation, infrared emission of the atmosphere, water vapor condensation, as well as thermal conductivity. Large-amplitude vortices in Earth's troposphere and ionosphere and their possible structure as well as redistribution of dust particles in the ionosphere as a result of vortical motions are discussed. The following possibilities for the dust particle redistribution are studied: capture and evolution of dust particles in AG-vortices, formation of dust vortices as a result of involving a great number of dust particles into vortex motions, and formation of vertical and horizontal dust flows (streamers and zonal flows). It is shown that excitation of AG-vortices at the ionospheric altitudes as a result of development of AG-wave instability leads to a substantial transportation of dust particles and their mixing. Layers of dust particles with a thickness of about a kilometer, forming at the altitudes less than 120km, distribute within the region of the existence of AG-vortical structures. As a result, at altitudes of 110–120km, dust vortices can appear, and transportation of particles up to altitudes of 130km becomes possible. One of the ways of transportation of dust particles in the ionosphere is dust flows, which are generated by dust vortices as a result of development of parametric instability.

      PubDate: 2015-09-27T06:24:14Z
  • Decrease in SYM-H during a storm main phase without evidence of a ring
           current injection
    • Abstract: Publication date: Available online 26 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R.E. Lopez, W.D. Gonzalez, V. Vasyliūnas, I.G. Richardson, C. Cid, E. Echer, G.D. Reeves, Pontus C. Brandt
      Changes in the Dst index, or the similarly constructed high-resolution SYM-H index, are thought to indicate changes in the total energy content of the ring current. However, this is not always the case. In this paper we examine an intense (SYM-H ∼ -435nT) magnetic storm that occurred on March 31, 2001. The arrival at Earth of strongly southward IMF produced an immediate negative response in the SYM-H index. While energetic particle and magnetometer data from geosynchronous orbit and inner magnetosphere energetic neutral atom imaging indicate that two substorm injections took place during the main phase, there was about one hour when the SYM-H decreased more than 200nT with no evidence in the data for ring current enhancement. Instead the near-Earth magnetotail exhibited a growth phase indicative of a strong, growing cross-tail current, with the large substorm expansion phase and the associated injection of energetic particles coming significantly later. Data from the DMSP spacecraft demonstrate that the polar cap flux grew rapidly in response to the strongly southward IMF. We present observations showing that the decrease in SYM-H occurred when polar cap flux was increasing and there was no evidence of injection into the ring current. Our findings strongly support the relationship between Dst and the polar cap flux proposed by theoretical studies that determined that the tail current system could be a significant contributor to Dst.

      PubDate: 2015-09-27T06:24:14Z
  • Solar-induced 27-day variations of mesospheric temperature and water vapor
           from the AIM SOFIE experiment: Drivers of polar mesospheric cloud
    • Abstract: Publication date: Available online 26 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Gary E. Thomas, Brentha Thurairajah, Mark E. Hervig, Christian von Savigny, Martin Snow
      Polar Mesospheric Clouds (PMCs) are known to be influenced by changes in water vapor and temperature in the cold summertime mesopause. Solar variability of these constituents has been held responsible for 11-year and 27-day variability of PMC activity, although the detailed mechanisms are not yet understood. It is also known that the solar influence on PMC variability is a minor contributor to the overall day-to-day variability, which is dominated by effects of gravity waves, planetary waves, and inter-hemispheric coupling. To address this issue, we have analyzed 15 seasons of data taken from the Solar Occultation for Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite. The SOFIE data contain precise measurements of water vapor, temperature and ice water content (among other quantities). These high-latitude measurements are made during the PMC season at the terminator, and therefore directly relate to the simultaneous measurements of mesospheric ice. Using a composite data set of Lyman-α irradiance, we correlated the time variation of the atmospheric variables with the 27-day variability of solar ultraviolet irradiance. We used a combination of time-lagged linear regression and Superposed Epoch Analysis to extract the solar contribution as sensitivity values (response/forcing) vs. height. We compare these results to previously published results, and show that the temperature sensitivity is somewhat higher, whereas the water sensitivity is nearly the same as published values. The time lags are shorter than that expected from direct solar heating and photodissociation, suggesting that the responses are due to 27-day variations of vertical winds. An analytic solution for temperature changes forced by solar irradiance variations suggests that if the response is due purely to Lyman-α heating and Newtonian cooling, the response should vary throughout the summertime season and depend primarily upon the height-dependent column density of molecular oxygen.

      PubDate: 2015-09-27T06:24:14Z
  • Daily global solar radiation prediction from air temperatures using kernel
           extreme learning machine: A case study for city of Bandar Abass, Iran
    • Abstract: Publication date: Available online 26 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Shahaboddin Shamshirband, Kasra Mohammadi, Hui-Ling Chen, Ganthan Narayana Samy, Dalibor Petković, Chao Ma
      Lately, the kernel extreme learning machine (KELM) has gained considerable importance in the scientific area due to its great efficiency, easy implementation and fast training speed. In this paper, for the first time the potential of KELM to predict the daily horizontal global solar radiation from the maximum and minimum air temperatures (T max and T min ) is appraised. The effectiveness of the proposed KELM method is evaluated against the grid search based support vector regression (SVR), as a robust methodology. Three KELM and SVR models are developed using different input attributes including: (1) T min and T max , (2) T min and T max ‒T min , and (3) T max and T max ‒T min . The achieved results reveal that the best predictions precision is achieved by models (3). The achieved results demonstrate that KELM offers favorable predictions and outperforms the SVR. For the KELM (3) model, the obtained statistical parameters of mean absolute bias error, root mean square error, relative root mean square error and correlation coefficient are 1.3445MJ/m2, 2.0164MJ/m2, 11.2464% and 0.9057, respectively for the testing data. As further examination, a month-by-month evaluation is conducted and found that in six months from May to October the KELM (3) model provides further accuracy than overall accuracy. Based upon the relative root mean square error, the KELM (3) model shows excellent capability in the period of April to October while in the remaining months represents good performance.

      PubDate: 2015-09-27T06:24:14Z
  • Role of upward leaders in modifying the induced currents in solitary
           down-conductors during a nearby lightning strike to ground
    • Abstract: Publication date: Available online 21 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Udaya Kumar
      Electromagnetic field produced by a lightning strike to ground causes significant induction to tall objects in the vicinity. The frequency of occurrence of such nearby ground strikes can be higher than the number of direct strikes. Therefore, a complete knowledge on these induced currents is of practical relevance. However, limited efforts towards the characterization of such induced currents in tall down-conductors could be seen in the literature. Due to the intensification of the background field caused by the descending stepped leader, tall towers/down-conductors can launch upward leaders of significant length. The nonlinearity in the conductance of upward leader and the surrounding corona sheath can alter the characteristics of the induced currents. Preliminary aspects of this phenomenon have been studied by the author previously and the present work aims to perform a detailed investigation on the role of upward leaders in modifying the characteristics of the induced currents. A consistent model for the upward leader, which covers all the essential electrical aspects of the phenomena, is employed. A first order arc model for representing the conductance of upward leader and a field dependent quadratic conductivity model for the corona sheath is employed. The initial gradient in the upward leader and the field produced by the return stroke forms the excitation. The dynamic electromagnetic response is determined by solving the wave equation using thin-wire time-domain formulation. Simulations are carried out initially to ascertain the role of individual parameters, including the length of the upward leader. Based on the simulation results, it is shown that the upward leader enhances the induced current, and when significant in length, can alter the waveshape of induced current from bipolar oscillatory to unipolar. The duration of the induced current is governed by the length of upward leader, which in turn is dependent on the return stroke current and the effective length of the down-conductor. If the current during the upward leader developmental phase is considered along with that after the stroke termination to ground, it would present a bipolar current pulse.

      PubDate: 2015-09-23T05:56:22Z
  • Analysis of air mass trajectories in the northern plateau of the Iberian
    • Abstract: Publication date: Available online 12 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Isidro A. Pérez, M. Luisa Sánchez, M. Ángeles García, Nuria Pardo
      Air masses reaching the Iberian Peninsula, which is located between two continents and two seas, have been classified. 24-h backward air trajectories were calculated each hour for three years using the METEX model at a site in the centre of the northern plateau of the Iberian Peninsula where the air flow has scarcely been investigated to date. Rather than the usual Euclidean geometry, spherical trigonometry, together with the kernel regression method, was considered to calculate trajectory distances to the site. Numerical indicators allow for an accurate description of the results. Ranges surrounding the site from E to S evidenced a restriction in the movement of the arriving flow. However, the range to the N showed only a slight effect. A noticeable seasonal contrast was observed between winter, whose distances were the greatest, and summer, which displayed the shortest distances. Trajectory clusters, initially not considered in the METEX model, were obtained with different metrics to determine the air mass pathways reaching the site. Five clusters of trajectories were selected so as to easily explain the directions and distances covered. Regional and long range transport were observed in clusters from the NE, NW and SW. The NE cluster presented an orographic deviation and local processes were limited to the SE cluster. Finally, seasonal analysis revealed singular behaviour during autumn, when local processes centred on the N-S direction.

      PubDate: 2015-09-15T05:15:36Z
  • The august 2011 URSI world Day campaign: Initial results
    • Abstract: Publication date: Available online 9 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Thomas J. Immel, Guiping Liu, Scott L. England, Larisa P. Goncharenko, Philip J. Erickson, Mykhaylo V. Lyashenko, Marco Milla, Jorge Chau, Harald U. Frey, Stephen B. Mende, Qihou Zhou, Anja Stromme, Larry J. Paxton
      During a 10-day URSI World Day observational campaign beginning on August 1, 2011, an isolated, major geomagnetic storm occurred. On August 5, Kp reached values of 8- and Dst dropped to -113nT. The occurrence of this isolated storm in the middle of a 10-day URSI World Day campaign provides and unprecedented opportunity to observe the coupling of solar wind energy into the magnetosphere and to evaluate the varied effects that occur in the coupled magnetosphere-ionosphere-thermosphere system. Dramatic changes in the ionosphere are seen at every one of the active radar stations, extending from Greenland down to equatorial Peru in the American sector and at middle latitudes in Ukraine. Data from TIMED and THEMIS are shown to support initial interpretations of the observations, where we focus on processes in the middle latitude afternoon sector during main phase, and the formation of a dense equatorial ionosphere during storm recovery. The combined measurements strongly suggest that the changes in ionospheric conditions observed after the main storm phase can be attributed in large part to changes in the stormtime thermosphere. This is through the generation of disturbance dynamo winds and also global neutral composition changes that either reduce or enhance plasma densities in a manner that depends mainly upon latitude. Unlike larger storms with possibly more sustained forcing, this storm exhibits minimal effects of persistent meridional stormtime wind drag, and little penetration of solar wind electric potentials to low latitudes. It is, therefore, an outstanding example of an impulsive event that exhibits longer-term effects through modification of the background atmosphere.

      PubDate: 2015-09-11T14:11:34Z
  • Estimation of available global solar radiation using sunshine duration
           over south Korea
    • Abstract: Publication date: Available online 9 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Amrita Das, Jin-ki Park, Jong-hwa Park
      Besides designing a solar energy system, accurate insolation data is also a key component for many biological and atmospheric studies. But solar radiation stations are not widely available due to financial and technical limitations; this insufficient number affects the spatial resolution whenever an attempt is made to construct a solar radiation map. There are several models in literature for estimating incoming solar radiation using sunshine fraction. Seventeen of such models among which 6 are linear and 11 non-linear, have been chosen for studying and estimating solar radiation on a horizontal surface over South Korea. The better performance of a non-linear model signifies the fact that the relationship between sunshine duration and clearness index does not follow a straight line. With such a model solar radiation over 79 stations measuring sunshine duration is computed and used as input for spatial interpolation. Finally monthly solar radiation maps are constructed using the Ordinary Kriging method. The cross validation results show good agreement between observed and predicted data.
      Graphical abstract image

      PubDate: 2015-09-11T14:11:34Z
  • Near-field CO-seismic ionospheric response due to the northern Chile Mw
           8.1 Pisagua earthquake on April 1, 2014 from GPS observations
    • Abstract: Publication date: Available online 6 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): C.D. Reddy, A.S. Sunil, G. González, Mahesh N. Shrivastava, Marcos Moreno
      Large earthquakes can induce near and far-field ionospheric perturbations by direct / secondary acoustic and gravity waves through Lithosphere-Atmosphere-Ionosphere (LAI) coupling. We analyze co-seismic induced ionospheric TEC perturbations following the northern Chile Mw 8.1 Pisagua earthquake occurred on April 1, 2014. The continuous Global Positioning System (GPS) data at 15 sites from the Integrated Plate boundary Observatory Chile (IPOC) and International GPS Service (IGS) GPS networks have been used in the present study. The nearest GPS site iqqe, ~98km away from the epicenter, recorded the ionospheric disturbance 12minutes after the event. The maximum co-seismic induced peak-to-peak TEC amplitude is ~1.25 TECU (1TECU=1016 electrons/m2), and the perturbations are confined to less than 1000km radius around the epicenter. The observed horizontal velocity of TEC perturbations has been determined as ~1180m/sec. We could also discern the signatures of acoustic gravity waves (AGW) with velocity~650m/s and frequency~2mHz. The ionospheric signal components due to Rayleigh and/or Tsunami waves could not be observed. This contribution presents characteristics of near-field co-seismic ionospheric response due to the 2014 Pisagua earthquake.

      PubDate: 2015-09-11T14:11:34Z
  • Correlation between the sunspot number and tropospheric refractivity in a
           tropical environment
    • Abstract: Publication date: Available online 20 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Najib Yusuf, B.G. Ayantunji
      In this paper, a study of the tropospheric surface refractivity relationship with sunspots number variability on daily scale was carried out in a tropical region in Nigeria. The data was averaged to hourly mean from the initial five minutes update cycle and then to daily mean using spread sheet. The dependence of surface radio refractivity on sunspots number for the period considered in this work was established using linear regression coefficient and the results for Lagos and Anyigba are R2=0.019, R 2=0.004, R2=0.010, R 2=0.000 and R 2=0.000 for 2007, 2008, 2009, 2010 and 2011 and R 2=0.089, R 2=0.027 and R 2=0.007 for 2010, 2011 and 2012 respectively. However, when the spotless days were filtered the regression coefficient was obtained to be R 2=0.145, R 2=0.01261, R 2=0.00001, R 2=0.0012 and R 2=0.062 for 2007, 2008, 2009, 2010 and 2011 for Lagos and R 2=0.1155, R 2=0.0261 and R 2=0.0071 for 2010, 2011 and 2012 for Anyigba respectively. Meteorological data from 2007 to 2011 was employed for Lagos while meteorological data from 2010 to 2012 was employed for Anyigba. Sunspot data was also obtained from Royal Observatory of Belgium for the period under study. Results obtained show no correlation between Sunspot number and surface refractivity. The sunspot number data was filtered to remove noise due to spotless days. The result obtained after filtering did not show any significant difference.

      PubDate: 2015-07-21T22:05:34Z
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