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  Subjects -> METEOROLOGY (Total: 87 journals)
Showing 1 - 36 of 36 Journals sorted alphabetically
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 9)
Advances in Climate Change Research     Open Access   (Followers: 1)
Advances in Meteorology     Open Access   (Followers: 12)
Aeolian Research     Hybrid Journal   (Followers: 2)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 8)
American Journal of Climate Change     Open Access   (Followers: 9)
Asian Journal of Earth Sciences     Open Access   (Followers: 17)
Atmósfera     Open Access   (Followers: 1)
Atmosphere     Open Access   (Followers: 4)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 7)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 13)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 6)
Atmospheric Research     Hybrid Journal   (Followers: 20)
Atmospheric Science Letters     Open Access   (Followers: 11)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 13)
Bulletin of the American Meteorological Society     Open Access   (Followers: 21)
Carbon Balance and Management     Open Access   (Followers: 5)
Change and Adaptation in Socio-Ecological Systems     Open Access   (Followers: 1)
Climate     Open Access   (Followers: 1)
Climate Change Economics     Hybrid Journal   (Followers: 10)
Climate Change Responses     Open Access  
Climate Dynamics     Hybrid Journal   (Followers: 14)
Climate law     Hybrid Journal   (Followers: 4)
Climate of the Past (CP)     Open Access   (Followers: 3)
Climate of the Past Discussions (CPD)     Open Access   (Followers: 1)
Climate Policy     Hybrid Journal   (Followers: 28)
Climate Research     Hybrid Journal   (Followers: 3)
Climate Risk Management     Open Access  
Climate Summary of South Africa     Full-text available via subscription  
Climatic Change     Hybrid Journal   (Followers: 41)
Current Climate Change Reports     Hybrid Journal  
Developments in Atmospheric Science     Full-text available via subscription   (Followers: 7)
Dynamics and Statistics of the Climate System     Open Access  
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 4)
Earth Perspectives - Transdisciplinarity Enabled     Open Access  
Energy & Environment     Full-text available via subscription   (Followers: 15)
Environmental and Climate Technologies     Open Access   (Followers: 1)
Global Meteorology     Open Access   (Followers: 3)
International Journal of Atmospheric Sciences     Open Access   (Followers: 5)
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: 18)
International Journal of Image and Data Fusion     Hybrid Journal   (Followers: 1)
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (Followers: 13)
Journal of Atmospheric and Oceanic Technology     Full-text available via subscription   (Followers: 10)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 16)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 5)
Journal of Climate     Full-text available via subscription   (Followers: 25)
Journal of Climatology     Open Access   (Followers: 1)
Journal of Hydrology and Meteorology     Open Access   (Followers: 7)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 3)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Journal of Meteorology and Climate Science     Full-text available via subscription   (Followers: 4)
Journal of Space Weather and Space Climate     Open Access   (Followers: 6)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 29)
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   (Followers: 2)
Mediterranean Marine Science     Open Access  
Meteorologica     Open Access  
Meteorological Applications     Hybrid Journal   (Followers: 2)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 2)
Meteorology and Atmospheric Physics     Hybrid Journal   (Followers: 8)
Mètode Science Studies Journal : Annual Review     Open Access  
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 4)
Monthly Notices of the Royal Astronomical Society Letters     Hybrid Journal   (Followers: 4)
Monthly Weather Review     Full-text available via subscription   (Followers: 17)
Nature Climate Change     Full-text available via subscription   (Followers: 46)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 22)
Open Journal of Modern Hydrology     Open Access   (Followers: 3)
Revista Brasileira de Meteorologia     Open Access   (Followers: 1)
Revista Iberoamericana de Bioeconomía y Cambio Climático     Open Access  
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 2)
Space Weather     Full-text available via subscription   (Followers: 4)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 1)
Tellus A     Open Access   (Followers: 8)
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: 13)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 4)
Weather     Hybrid Journal   (Followers: 8)
Weather and Climate Extremes     Open Access   (Followers: 5)
Weather and Forecasting     Full-text available via subscription   (Followers: 8)
Weatherwise     Hybrid Journal   (Followers: 1)
气候与环境研究     Full-text available via subscription   (Followers: 1)
Journal Cover Journal of Atmospheric and Solar-Terrestrial Physics
  [SJR: 1.045]   [H-I: 61]   [16 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [2817 journals]
  • Inter-hourly variability of total electron content during the quiet
           condition over Nigeria, within the equatorial ionization anomaly region
    • Abstract: Publication date: Available online 7 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): T.T. Ayorinde, A. B Rabiu, C. Amory-Mazaudier
      The inter-hourly variability (IHV) of the Total Electron Content (TEC) over Nigeria during the quiet days (Ap<4) of the year 2013 was examined using ground-based GPS receivers installed at seven (7) different locations across Nigeria by the Nigerian Global Navigation Satellite Systems (GNSS) Reference Network (NIGNET) operated by the office of the surveyor general of Nigeria. Nigeria is a country that lies within equatorial ionospheric anomaly (EIA) region. The IHV was calculated by converting the observed hourly slant TEC (STEC) value into the hourly vertical TEC (VTEC) and the differencing (∆TEC) with its corresponding hourly value from the previous day. There is a clear variation which depicts the expected temporal variability. The IHV in TEC in all the stations ranges between 0-20 TECU (TEC Units). The seasonal variation of the IHV of TEC over Nigeria maximizes (5-20 TECU) during Equinoctial months and minimizes (1-10 TECU) during the Solstice months. The IHV of TEC in September equinox period is higher than that of March equinox. Minimum value of IHV (~7 TECU at equinoxes and ~5 TECU at Solstice) was recorded at the Office of Surveyor General of the Federation (OSGF) station and the maximum value (~12 TECU at equinoxes and ~16 TECU at Solstice) was recorded at the Birni Kebbi Federal Polytechnic (BKFP) station which may be due to the fact that BKFP at 0.72° dip latitude is closer to the dip equator.


      PubDate: 2016-04-09T11:09:44Z
       
  • Cloud cover anomalies at middle latitudes: links to troposphere dynamics
           and solar variability
    • Abstract: Publication date: Available online 6 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): S. Veretenenko, M. Ogurtsov
      In this work we study links between low cloud anomalies (LCA) at middle latitudes of the Northern and Southern hemispheres and galactic cosmic ray (GCR) variations used as a proxy of solar variability on the decadal time scale. It was shown that these links are not direct, but realized through GCR/solar activity phenomena influence on the development of extratropical baric systems (cyclones and troughs) which form cloud field. The violation of a positive correlation between LCA and GCR intensity which was observed in the 1980s–1990s occurred simultaneously in the Northern and Southern hemispheres in the early 2000s and coincided with the sign reversal of GCR effects on troposphere circulation. It was suggested that a possible reason for the correlation reversal between cyclonic activity at middle latitudes and GCR fluxes is the change of the stratospheric polar vortex intensity which influences significantly the troposphere-stratosphere coupling. The evidences for a noticeable weakening of the polar vortices in the Arctic and Antarctic stratosphere in the early 2000s are provided. The results obtained suggest an important role of the polar vortex evolution as a reason for a temporal variability of solar activity effects on the lower atmosphere.


      PubDate: 2016-04-07T10:59:03Z
       
  • Cloud properties during active and break spells of the west african summer
           monsoon from CloudSat-CALIPSO measurements
    • Abstract: Publication date: Available online 3 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): E. Efon, A. Lenouo, D. Monkam, D. Manatsa
      High resolution of daily rainfall dataset from the Tropical Rainfall Measuring Mission (TRMM) was used to identify active and break cloud formation periods. The clouds were characterized based on CloudSat-CALIPSO satellite images over West Africa during the summer monsoon during the period 2006-2010. The active and break periods are defined as the periods during the peak monsoon months of June to August when the normalized anomaly of rainfall over the monsoon core zone is greater than 0.9 or less than − 0.9 respectively, provided the criteria is satisfied for at least three consecutive days. It is found that about 90% of the break period and 66.7% of the active spells lasted 3-4 days. Active spells lasting duration of about a week were observed while no break spell had such a long span. Cloud macrophysical (cloud base height (CBH), cloud top height (CTH) and cloud geometric depth (∆H), microphysical (cloud liquid water content, (LWC), liquid number concentration (LNC), liquid effective radius, ice water content (IWC), ice number concentration (INC) and ice effective radius) and radiative (heating rate properties) over South Central West Africa (5°−15°N; 15°W-10°E) during the active and break spells were also analyzed. High-level clouds are more predominant during the break periods compared to the active periods. Active spells have lower INC compared to the break spells. Liquid water clouds are observed to have more radiative forcing during the active than break periods while ice phase clouds bring more cooling effect during the break spells compared to the active spells.


      PubDate: 2016-04-07T10:59:03Z
       
  • A link between high-speed solar wind streams and explosive extratropical
           cyclones
    • Abstract: Publication date: Available online 7 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Paul Prikryl, Koki Iwao, Donald B. Muldrew, Vojto Rušin, Milan Rybanský, Robert Bruntz
      A link between solar wind magnetic sector boundary (heliospheric current sheet) crossings by the Earth and the upper-level tropospheric vorticity was discovered in the 1970s. These results have been later confirmed but the proposed mechanisms remain controversial. Extratropical-cyclone tracks obtained from two meteorological reanalysis datasets are used in superposed epoch analysis of time series of solar wind plasma parameters and green coronal emission line intensity. The time series are keyed to times of maximum growth of explosively developing extratropical cyclones in the winter season. The new statistical evidence corroborates the previously published results (Prikryl et al., 2009). This evidence shows that explosive extratropical cyclones tend to occur after arrivals of solar wind disturbances such as high-speed solar wind streams from coronal holes when large amplitude magneto-hydrodynamic waves couple to the magnetosphere-ionosphere system. These MHD waves modulate Joule heating and/or Lorentz forcing of the high-latitude thermosphere generating medium-scale atmospheric gravity waves that propagate energy upward and downward from auroral zone through the atmosphere. At the tropospheric level, in spite of significantly reduced amplitudes, these gravity waves can provide a lift of unstable air to release the moist symmetric instability thus initiating slantwise convection and forming cloud/precipitation bands. The release of latent heat is known to provide energy for rapid development and intensification of extratropical cyclones.


      PubDate: 2016-04-07T10:59:03Z
       
  • Signature of a possible relationship between the maximum CME speed index
           and the critical Frequencies of tHE f1 AND f2 Ionospheric Layers: Data
           Analysis FOR A Mid-Latitude Ionospheric Station DURING THE Solar Cycles 23
           AND 24
    • Abstract: Publication date: Available online 31 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Ali Kilcik, Atila Ozguc, Erdal Yiğit, Vasyl Yurchyshyn, Burcin Donmez
      We analyze temporal variations of two solar indices, the monthly mean Maximum CME Speed Index (MCMESI) and the International Sunspot Number (ISSN) as well as the monthly median ionospheric critical frequencies (foF1, and foF2) for the time period of 1996-2013, which covers the entire solar cycle 23 and the ascending branch of the cycle 24. We found that the maximum of foF1 and foF2 occurred respectively during the first and second maximum of the ISSN solar activity index in the solar cycle 23. We compared these data sets by using the cross-correlation and hysteresis analysis and found that both foF1 and foF2 show higher correlation with ISSN than the MCMESI during the investigated time period, but when significance levels are considered correlation coefficients between the same indices become comparable. Cross-correlation analysis showed that the agreement between these data sets (solar indices and ionospheric critical frequencies) is better pronounced during the ascending phases of solar cycles, while they display significant deviations during the descending phase. We conclude that there exists a signature of a possible relationship between MCMESI and foF1 and foF2, which means that MCMESI could be used as a possible indicator of solar and geomagnetic activity, even though other investigations are needed.


      PubDate: 2016-04-03T05:08:31Z
       
  • Locating narrow bipolar events with single-station measurement of
           low-frequency magnetic fields
    • Abstract: Publication date: Available online 30 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Hongbo Zhang, Gaopeng Lu, Xiushu Qie, Rubin Jiang, Yanfeng Fan, Ye Tian, Zhuling Sun, Mingyuan Liu, Zhichao Wang, Dongxia Liu, Guili Feng
      We developed a method to locate the narrow bipolar events (NBEs) based on the single-station measurement of low-frequency (LF, 40-500kHz) magnetic fields. The direction finding of a two-axis magnetic sensor provides the azimuth of NBEs relative to the measurement site; the ionospheric reflection pairs in the lightning sferics are used to determine the range and height. We applied this method to determine the three-dimensional (3D) locations of 1475 NBEs with magnetic signals recorded during the SHandong Artificially Triggered Lightning Experiment (SHATLE) in summer of 2013. The NBE detections are evaluated on a storm basis by comparing with radar observations of reflectivity and lightning data from the World Wide Lightning Location Network (WWLLN) for two mesoscale convective systems (MCSs) of different sizes. As revealed by previous studies, NBEs are predominately produced in the convective regions with relatively strong radar echo (with composite reflectivity ≥30dBZ), although not all the convections with high reflectivity and active lightning production are in favor of NBE production. The NBEs located by the single-station magnetic method also exhibit the distinct segregation in altitude for positive and negative NBEs, namely positive NBEs are mainly produced between 7km and 15km, while negative NBEs are predominantly produced above 14km. In summary, the results of comparison generally show that the single-station magnetic method can locate NBEs with good reliability, although the accuracy of 3D location remains to be evaluated with the traditional multi-station method based on the time-of-arrival technique. This method can be applied to track the motion of storm convection within 800km, especially when they move out to ocean beyond the detection range (typically <400km) of meteorological radars, making it possible to study NBEs in oceanic thunderstorms for which the location with multiple ground-based stations is usually not feasible.


      PubDate: 2016-04-03T05:08:31Z
       
  • Multifractal analysis of lightning channel for different categories of
           lightning
    • Abstract: Publication date: Available online 2 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): F.J. Miranda, S.R. Sharma
      A study from the point of view of complex systems is done for lightning occurred at Diamantina, Sete Lagoas and São José dos Campos, during the summer from September 2009 to April 2010. For the first time, multifractal analyses were performed for different lightning categories: two-dimensional, three-dimensional, non-branched, branched, cloud, cloud-to-ground, single and multiple. We found that when using two-dimensional images of natural lightning embedded in three dimensions to perform multifractal analysis, the interpretation of the multifractal spectrum must be restricted to identification of the multi (mono) fractal character of lightning channel and to estimation of fractal dimension. We have also observed that, on the average, each category has a specific value of fractal dimension. Categories in which branches and tortuosity are more usual, like branched and cloud categories, exhibited largest fractal dimensions due to more complexity of lightning channels. The results suggest that single and multiple lightning have similar complexities in their channels, leading to the same average values of fractal, information and correlation dimensions for both categories.


      PubDate: 2016-04-03T05:08:31Z
       
  • Evaluation of the inter-annual variability of stratospheric chemical
           composition in chemistry-climate models using ground-based multi species
           time series
    • Abstract: Publication date: Available online 1 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): V. Poulain, S. Bekki, M. Marchand, M.P. Chipperfield, M. Khodri, S. Dhomse, G.E. Bodeker, R. Toumi, M. De Maziere, J.-P. Pommereau, A. Pazmino, F. Goutail, D. Plummer, E. Rozanov, E. Mancini, H. Akiyoshi, J.-F. Lamarque, J. Austin
      The variability of stratospheric chemical composition occurs on a broad spectrum of timescales, ranging from day to decades. A large part of the variability appears to be driven by external forcings such as volcanic aerosols, solar activity, halogen loading, levels of greenhouse gases (GHG), and modes of climate variability (quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO)). We estimate the contributions of different external forcings to the interannual variability of stratospheric chemical composition and evaluate how well 3-D chemistry-climate models (CCMs) can reproduce the observed response-forcing relationships. We carry out multivariate regression analyses on long time series of observed and simulated time series of several traces gases in order to estimate the contributions of individual forcings and unforced variability to their internannual variability. The observations are typically decadal time series of ground-based data from the international Network for the Detection of Atmospheric Composition Change (NDACC) and the CCM simulations are taken from the CCMVal-2 REF-B1 simulations database. The chemical species considered are column O3, HCl, NO2, and N2O. We check the consistency between observations and model simulations in terms of the forced and internal components of the total interannual variability (externally forced variability and internal variability) and identify the driving factors in the interannual variations of stratospheric chemical composition over NDACC measurement sites. Overall, there is a reasonably good agreement between regression results from models and observations regarding the externally forced interannual variability. A much larger fraction of the observed and modelled interannual variability is explained by external forcings in the tropics than in the extratropics, notably in polar regions. CCMs are able to reproduce the amplitudes of responses in chemical composition to specific external forcings. However, CCMs tend to underestimate very substantially the internal variability and hence the total interannual variability for almost all species considered. This lack of internal variability in CCMs might partly originate from the surface forcing of these CCMs by analysed SSTs. The results illustrate the potential of NDACC ground-based observations for evaluating CCMs.


      PubDate: 2016-04-03T05:08:31Z
       
  • Visibility effect on the availability of a terrestrial free space optics
           link under a tropical climate
    • Abstract: Publication date: Available online 25 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Ahmed Basahel, Islam Md. Rafiqul, Mohamad Hadi Habaebi, A.Z. Suriza
      Haze, fog and rain limit the visibilities and acts as dominant parameter for free space optics availability estimation. Low visibilities increase atmospheric attenuation and reduce the availability of optical signals from free space optics (FSO) links. Thus, this study determines the effect of visibility on FSO link availability in a tropical climate. Visibility data were measured in Malaysia for three years and used to estimate availability of FSO links. Rain and haze are two phenomena which reduces the visibility in tropical climate like Malaysia. Hence three cases were considered for measured data analysis: rain with dense haze, dense haze, and normal haze cases. In Malaysia, seasonal dense haze is mainly attributed to forest fires in Indonesia and in parts of Malaysia. The atmospheric attenuations predicted based on measured visibility (km) were compared across the three cases. The attenuations in the first two cases are found severe (almost 155dB/km); while in the third case it is very low (almost 6dB/km). The worst case (dense haze) is equivalent to a thick fog in temperate regions and must be examined carefully with respect to FSO deployment in a tropical environment.


      PubDate: 2016-03-29T04:46:56Z
       
  • Spatiotemporal analysis of snow cover variations at mt. Kilimanjaro using
           multi-temporal Landsat images during 27 years
    • Abstract: Publication date: Available online 28 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Sung-Hwan Park, Moung-Jin Lee, Hyung-Sup Jung
      The Landsat TM and ETM+ images have been acquired for the long period from the 1980s until the present with the temporal resolution of a 16-day repeat cycle from the visible, near infrared (NIR), short wave infrared (SWIR) and thermal infrared (TIR) bands. The Landsat multi-temporal images have been successfully used to monitor variations of the Earth surface during 27 years. In this paper, we observe the variations of 1) the snow cover area, 2) the snowline height and 3) the land surface temperature (LST) lapse rate at Mt. Kilimanjaro using a total number of 15 Landsat-5 TM and Landsat-7 ETM+ images from June 1984 to July 2011. Segmentation of normalized difference snow index (NDSI) images with a threshold of 0.6 is used to extract snow cover. Snowline altitude is then determined by combining the snow cover classification maps with a digital elevation model (DEM). And the LST lapse rate is also calculated from the TIR band in the forest area. The results from this study show that 1) the snow cover area largely decreases from 10.1km2 to 2.3km2 during about 27 years, which corresponds to a 77.2% reduction, 2) the snowline height rose from 4,760m to 5,020m by about 260m, and 3) the LST lapse rate shifted from −5.2°C/km to −2.7°C/km. This study demonstrates that multi-temporal Landsat images can be successfully used for the spatiotemporal analysis of long-term snow cover changes.


      PubDate: 2016-03-29T04:46:56Z
       
  • IFC-Ed. board
    • Abstract: Publication date: May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 142




      PubDate: 2016-03-29T04:46:56Z
       
  • Variability of mesospheric water vapor above Bern in relation to the
           27-day solar rotation cycle
    • Abstract: Publication date: Available online 29 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Martin Lainer, Klemens Hocke, Niklaus Kämpfer
      Many studies investigated solar-terrestrial responses (thermal state, O3, OH, H2O) with emphasis on the tropical upper atmosphere. In this paper the focus is switched to water vapor in the mesosphere at a mid-latitudinal location. Eight years of water vapor profile measurements above Bern ( 46.88 ° N / 7.46 ° E ) are investigated to study oscillations with the focus on periods between 10 to 50 days. Different spectral analyses revealed prominent features in the 27-day oscillation band, which are enhanced in the upper mesosphere (above 0.1 hPa , ∼ 64 km ) during the rising sunspot activity of solar cycle 24. Local as well as zonal mean Aura MLS observations support these results by showing a similar behavior. The relationship between mesospheric water and the solar Lyman-α flux is studied by comparing the similarity of their temporal oscillations. The H2O oscillation is negatively correlated to solar Lyman-α oscillation with a correlation coefficient of up to − 0.3 to − 0.4 , and the phase lag is 6–10 days at 0.04 hPa . The confidence level of the correlation is ≥ 99 % . This finding supports the assumption that the 27-day oscillation in Lyman-α causes a periodical photodissociation loss in mesospheric water. Wavelet power spectra, cross-wavelet transform and wavelet coherence analysis (WTC) complete our study. More periods of high common wavelet power of H2O and solar Lyman-α are present when amplitudes of the Lyman-α flux increase. Since this is not a measure of physical correlation a more detailed view on WTC is necessary, where significant (two sigma level) correlations occur intermittently in the 27 and 13-day band with variable phase lock behavior. Large Lyman-α oscillations appeared after the solar superstorm in July 2012 and the H2O oscillations show a well pronounced anti-correlation. The competition between advective transport and photodissociation loss of mesospheric water vapor may explain the sometimes variable phase relationship of mesospheric H2O and solar Lyman-α oscillations. Generally, the WTC analysis indicates that solar variability causes observable photochemical and dynamical processes in the mid-latitude mesosphere.


      PubDate: 2016-03-29T04:46:56Z
       
  • Characterisation of GPS-TEC in the african equatorial and low latitude
           region and the regional evaluation of the IRI model
    • Abstract: Publication date: Available online 22 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): S.J. Adebiyi, I.A. Adimula, O.A. Oladipo
      With the increasing application of Global Navigation Satellite System (GNSS) products and services, knowledge of the Total Electron Content (TEC) variation is vital, particularly in historically under-sampled regions. The ionospheric induced-error, which is the largest and most variable error source of GNSS applications, is proportional to TEC along the satellite-receiver path. Simultaneous Global Positioning System (GPS) measurements from six African equatorial and low latitude stations in the southern hemisphere are used to investigate the latitudinal variation of TEC over the region during the year 2013, a year of moderate solar activity. The analysis reveals some detailed features of seasonal, month-to-month and solar activity dependence of TEC. The seasonal variation of TEC revealed that the daytime and the pre-midnight values of TEC for stations located close to the geographic equator is considerably higher in equinoxes and June solstice compared to stations farther from the equator, however, the difference is insignificant during the December solstice. The month-to-month variation of TEC shows semi-annual symmetry/asymmetry in TEC values for stations closer/farther from the equator. TEC sensitivity to solar activity shows significant seasonal and latitudinal characteristics. Generally, a relatively good correlation exists between TEC and F10.7 for stations around the Equatorial Ionization Anomaly (EIA) region compared to those found at stations close to the equator. Beyond the EIA region, the correlation coefficients drop in all seasons. TEC predicted by the three topside options of the International Reference Ionosphere (IRI) 2012 model [i.e. the NeQuick (NeQ), IRI-2001 Corrected (IRI-01 Corr) and the IRI-2001 (IRI-01) options] exhibits latitudinal and seasonal characteristics. The NeQ option performed better than the other two options at stations located within the equatorial region in most of the months and seasons. Outside the EIA region, the IRI-01 Corr and IRI-01 options give better predictions. Generally, the three model options give improved TEC representations with increasing latitude.


      PubDate: 2016-03-25T04:35:03Z
       
  • Time distribution of heavy rainfall events in south west of IRAN
    • Abstract: Publication date: Available online 24 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Zahra Ghassabi, G. Ali kamali, AmirHosein Meshkati, Sohrab Hajam, Nasrolah Javaheri
      Accurate knowledge of rainfall time distribution is a fundamental issue in many Meteorological-Hydrological studies such as using the information of the surface runoff in the design of the hydraulic structures, flood control and risk management, and river engineering studies. Since the main largest dams of Iran are in the south-west of the country (i.e. South Zagros), this research investigates the temporal rainfall distribution based on an analytical numerical method to increase the accuracy of hydrological studies in Iran. The United States Soil Conservation Service (SCS) estimated the temporal rainfall distribution in various forms. Hydrology studies usually utilize the same distribution functions in other areas of the world including Iran due to the lack of sufficient observation data. However, we first used Weather Research Forecasting (WRF) model to achieve the simulated rainfall results of the selected storms on south west of Iran in this research. Then, a three-parametric Logistic function was fitted to the rainfall data in order to compute the temporal rainfall distribution. The domain of the WRF model is 30.5N-34N and 47.5E-52.5E with a resolution of 0.08 degree in latitude and longitude. We selected 35 heavy storms based on the observed rainfall data set to simulate with the WRF Model. Storm events were scrutinized independently from each other and the best analytical three-parametric logistic function was fitted for each grid point. The results show that the value of the coefficient a of the logistic function, which indicates rainfall intensity, varies from the minimum of 0.14 to the maximum of 0.7. Furthermore, the values of the coefficient B of the logistic function, which indicates rain delay of grid points from start time of rainfall, vary from 1.6 in south-west and east to more than 8 in north and central parts of the studied area. In addition, values of rainfall intensities are lower in south west of IRAN than those of observed or proposed by the SCS values in the US.


      PubDate: 2016-03-25T04:35:03Z
       
  • The inter-annual distribution of cloudless days and nights in Abastumani:
           Coupling with cosmic factors and climate change
    • Abstract: Publication date: April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 141
      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: 2016-03-25T04:35:03Z
       
  • IFC-Ed. board
    • Abstract: Publication date: April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 141




      PubDate: 2016-03-25T04:35:03Z
       
  • Hemispheric differences in the response of the upper atmosphere to the
           August 2011 geomagnetic storm: A simulation study
    • Abstract: Publication date: April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 141
      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: 2016-03-25T04:35:03Z
       
  • Vertical coupling between troposphere and lower ionosphere by electric
           currents and fields at equatorial latitudes
    • Abstract: Publication date: April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 141
      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: 2016-03-25T04:35:03Z
       
  • Influence of solar activity on red sprites and on vertical coupling in the
           system stratosphere–mesosphere
    • Abstract: Publication date: April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 141
      Author(s): Peter T. Tonev, Peter I.Y. Velinov
      The positive downward propagating streamers of sprites are considered as factors of vertical coupling in middle atmosphere. Sprites are initiated in the lower ionosphere (at 75–85km) and their streamers propagate in the mesosphere and upper stratosphere where the solar activity (SA) can have significant influence. The problem considered by us is whether sprites are sensitive to the solar activity. Different possible ways of such influence are considered. They concern: i) relations between solar activity and the occurrence of sprite-producing lightning discharges; ii) sensitivity of streamer inception to solar variability; iii) 11-year variations of conductivity in the night-time mesosphere and stratosphere during solar cycle due to modulation of the galactic cosmic ray flux by solar activity, which can lead to changes in sprite-driving electric fields, and therefore, in sprites. Accounting for the effects of sprites on minor constituents (in particular NO x ), a link between SA level and the che^mical balance in the mesosphere and stratosphere is considered, as well. With respect to this we study by modeling the response of the sprite-driving electric fields to SA variations with the account to a complex of parameters of sprite-producing lightning discharges and atmospheric conductivity. The lightning-driven electric fields needed for streamer propagation show minor dependence on conductivity changes caused by variations in cosmic ray flux during a solar cycle. The long-term changes in sprite's lower boundary by different parameters of lightning discharges and atmospheric conductivity parameters are estimated. During solar minimum, of the vertical dimension of sprites increases by up to 1.5km than those during solar maximum. We estimate also the effect of the reduction of conductivity in thunderclouds with respect to the adjacent air. Reduction of cloud conductivity by a factor of 5–10 leads to larger vertical dimension of sprites due to descending of the sprite lower boundary by up to 5km related to the case of unmodified cloud conductivity. The solar variability has significantly bigger effect on the sprite vertical dimension by larger charge moment change of the parental lightning discharge and by large reduction of the cloud conductivity.


      PubDate: 2016-03-25T04:35:03Z
       
  • Comparison of DMSP and SECS region-1 and region-2 ionospheric current
           boundary
    • Abstract: Publication date: Available online 15 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): J.M. Weygand, S. Wing
      The region-1 and region-2 boundary has traditionally been identified using data from a single spacecraft crossing the auroral region and measuring the large scale changes in the cross track magnetic field. With data from the AUTUMN, CANMOS, CARISMA, GIMA, DTU MGS, MACCS, McMAC, STEP, THEMIS, and USGS ground magnetometer arrays we applied a state-of-art technique based on spherical elementary current system (SECS) method developed by Amm and Viljanen [1999) in order to calculate maps of region-1 and region-2 current system over the North American and Greenland auroral region. Spherical elementary current (SEC) amplitude (proxy for vertical currents) maps can be inferred at 10sec temporal resolution,~1.5° geographic latitude (Glat), and 3.5° geographic longitude (Glon) spatial resolution. We compare the location of the region-1 and region-2 boundary obtained by the DMSP spacecraft with the region-1 and region-2 boundary observed in the SEC current amplitudes. We find that the boundaries typically agree within 0.2°±1.3°. These results indicate that the location of the region-1 and region-2 boundary can reasonably be determined from ground magnetometer data. The SECS maps represent a value-added product from the magnetometer database and can be used for contextual interpretation in conjunction with other missions as well as help with our understanding of magnetosphere-ionosphere coupling mechanisms using the ground arrays and the magnetospheric spacecraft data.


      PubDate: 2016-03-20T04:21:15Z
       
  • Temporal variability patterns in solar radiation estimations
    • Abstract: Publication date: Available online 15 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): José M. Vindel, Ana A. Navarro, Rita X. Valenzuela, Luis F. Zarzalejo
      In this work, solar radiation estimations obtained from a satellite and a numerical weather prediction model in mainland Spain have been compared. Similar comparisons have been formerly carried out, but in this case, the methodology used is different: the temporal variability of both sources of estimation has been compared with the annual evolution of the radiation associated to the different study climate zones. The methodology is based on obtaining behavior patterns, using a Principal Component Analysis, following the annual evolution of solar radiation estimations. Indeed, the adjustment degree to these patterns in each point (assessed from maps of correlation) may be associated with the annual radiation variation (assessed from the interquartile range), which is associated, in turn, to different climate zones. In addition, the goodness of each estimation source has been assessed comparing it with data obtained from the radiation measurements in ground by pyranometers. For the study, radiation data from Satellite Application Facilities and data corresponding to the reanalysis carried out by the European Centre for Medium-Range Weather Forecasts have been used.


      PubDate: 2016-03-20T04:21:15Z
       
  • Parameterization of Large-Scale Turbulent Diffusion in the presence of
           both well-mixed and weakly mixed patchy layers
    • Abstract: Publication date: Available online 17 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M.K. Osman, W.K. Hocking, D.W. Tarasick
      Vertical diffusion and mixing of tracers in the upper troposphere and lower stratosphere (UTLS) is not uniform, but primarily occurs due to patches of turbulence that are intermittent in time and space. The effective diffusivity of regions of patchy turbulence is related to statistical parameters describing the morphology of turbulent events, such as lifetime, number, width, depth and local diffusivity (i.e., diffusivity within the turbulent patch) of the patches. While this has been recognized in the literature, the primary focus has been on well-mixed layers, with few exceptions. In such cases the local diffusivity is irrelevant, but this is not true for weakly and partially mixed layers. Here, we use both theory and numerical simulations to consider the impact of intermediate and weakly mixed layers, in addition to well-mixed layers. Previous approaches have considered only one dimension (vertical), and only a small number of layers (often one at each time step), and have examined mixing of constituents. We consider a two-dimensional case, with multiple layers (10 and more, up to hundreds and even thousands), having well-defined, non-infinite, lengths and depths. We then provide new formulas to describe cases involving well-mixed layers which supersede earlier expressions. In addition, we look in detail at layers that are not well mixed, and, as in interesting variation on previous models, our procedure is based on tracking the dispersion of individual particles, which is quite different to the earlier approaches which looked at mixing of constituents. We develop an expression which allows determination of the degree of mixing, and show that layers used in some previous models were in fact not well mixed and so produced erroneous results. We then develop a generalized model based on two dimensional random-walk theory employing Rayleigh distributions which allows us to develop a universal formula for diffusion rates for multiple two-dimensional layers with general degrees of mixing. We show that it is the largest, most vigorous and less common turbulent layers that make the major contribution to global diffusion. Finally, we make estimates of global-scale diffusion coefficients in the lower stratosphere and upper troposphere. For the lower stratosphere, κ eff ≈ 2 x 10-2 m2 s-1, assuming no other processes contribute to large-scale diffusion.


      PubDate: 2016-03-20T04:21:15Z
       
  • Long-term monthly statistics of mid-latitudinal NmF2 in the northern
           geographic hemisphere during geomagnetically quiet and steadily low solar
           activity conditions
    • Abstract: Publication date: Available online 10 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.V. Pavlov, N.M. Pavlova
      Long-term mid-latitude hourly values of NmF2 measured in 1957-2015 by 10 ionosondes in the Northern geographic hemisphere were processed to select periods of geomagnetically quiet and low solar activity conditions to calculate several descriptive statistics of the noon NmF2 for each month, including the mathematical expectation, most probable value, arithmetic average, and arithmetic average median. The month-to-month variability of these descriptors allowed us to identify months of a year when they reach their extremes (maxima, minima). The calculated month-to-month variations of the NmF2 statistical parameters made it possible to study the winter anomaly and spring-autumn asymmetry in these statistical parameters.


      PubDate: 2016-03-10T17:27:01Z
       
  • The role of deviation of magnetic field direction on the beaming angle:
           Extending of beaming angle theory
    • Abstract: Publication date: May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 142
      Author(s): Mohammad Javad Kalaee, Yuto Katoh
      In the beaming angle theory, the magnetic field direction is assumed perpendicular to the normal boundary, and the prediction of this theory, from beaming angle is base on the Jones' formula. We investigate the effect of deviation the magnetic field direction respect to normal boundary direction. In this study, we present new conditions that under these conditions two modes, extraordinary and ordinary modes waves can match. Also, we show for these cases the beaming angle does not correspond to Jones' formula. This effect leads to the angles larger and smaller than the angle estimated by Jones' formula. This effect on the mode conversion process becomes important in a case where local fluctuations in the direction of the density gradient vector or the magnetic field direction are observed. By comparing the beaming angle from observations with the beaming angles resulting from different ∆ Φ , we showed a ∆ Φ about 3 to 5° are necessary in consistence with observation.


      PubDate: 2016-03-06T17:46:47Z
       
  • Corrigendum to: “On the mimimum length of leader channel and the
           minimum volume of space charge concentration necessary to initiate
           lightning flashes in thunderclouds” [J. Atmos. Sol.-Terr. Phys. 136
           (2015) 39–45]
    • Abstract: Publication date: Available online 24 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Vernon Cooray



      PubDate: 2016-03-06T17:46:47Z
       
  • Variability of Madden Julian Oscillations (MJO) observed over southern
           India using radiosonde observations
    • Abstract: Publication date: May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 142
      Author(s): P.P. Leena, M. Venkat Ratnam, B.V. Krishna Murthy, S. Vijaya Bhaskara Rao
      In the present work, characteristics of 30–50 day oscillations (referred to as the MJO) in tropospheric and lower stratospheric wind and temperature have been studied using long-term high resolution radiosonde observations at a tropical station, Gadanki (13.5°N, 79.2°E) for the period 2006–2012. Wind and temperature perturbations showed clear features of the MJO with higher amplitudes between 10 and 18km altitude. Interestingly, the MJO signal is confined vertically to different altitudes in different seasons. Variability in the perturbations of wind and temperature similar to that of outgoing long-wave radiation (OLR) with a few cases showing an out of phase relation. The amplitudes of these oscillations are larger in the winter and pre-monsoon seasons than in the monsoon season where the largest amplitudes are confined below the Tropical Easterly Jet (~16km). There also exists a large inter-annual variability in the MJO. Spatio-temporal variability of OLR not only showed the features of the MJO but also northward and eastward propagation in the monsoons and winter seasons, respectively, in a few cases. It is found that convection leads the MJO in the zonal wind by 8–12 days in all the seasons except in winter. One intriguing result observed is the vitiation of the MJO pattern by the presence of strong wind shears during monsoon season. We expect this study would be helpful in representing the MJO features in the vertical in the general circulation models (GCMs) which is still a major challenge.


      PubDate: 2016-03-06T17:46:47Z
       
  • A mesospheric airglow multichannel photometer and an optical method to
           measure mesospheric AGW intrinsic parameters
    • Abstract: Publication date: Available online 2 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Anthony Mangognia, Gary Swenson, Fabio Vargas, Alan Liu
      A multichannel photometer (MCP) instrument, designed with filters for three specific airglow emissions, OH Meinel (5-1), (6-2), 840nm; O2 (b) (0,1), 865nm; and O ( S 1 ) , 557.7nm, as well as background, is used to observe atmospheric wave perturbations to layers in the local zenith with high temporal resolution (∼5s). By measuring the relative phase of propagating waves through the layers, with known altitude separation, we deduce the vertical wavelength. We describe here the instrument attributes, a unique background subtraction technique, and the validation of a new method for determining intrinsic wave parameters via MCP and imager data that can be taken from various platforms, including ground-based and spacecraft platforms. Vertical wavelengths deduced using this method are in close agreement with those measured using LIDAR temperatures as well as those calculated with the dispersion relation using a combination of all-sky imager (horizontal wavelength) and meteor radar (winds) data.


      PubDate: 2016-03-06T17:46:47Z
       
  • IFC-Ed. board
    • Abstract: Publication date: March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 140




      PubDate: 2016-03-06T17:46:47Z
       
  • On the polarization relations of diurnal and semidiurnal tide in the
           mesopause region
    • Abstract: Publication date: Available online 3 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Chiao-Yao She, David A. Krueger, Tao Yuan, Jens Oberheide
      The polarization relations for gravity waves are well known and have proven to be very powerful for the investigation of their dynamics. Though tides are sometimes regarded as low-frequency gravity waves, their polarization relations are hardly considered. We derive the polarization relationships of tides from the primitive equations for perturbations of a dissipation-less atmosphere. The vertical wind tide is found to relate directly to temperature tide, independent of tidal structure and geometric location. On the other hand, the relation between meridional wind tide and zonal wind tide is found to depend on the horizontal derivatives of the associated geopotential perturbation, thus depending on tidal structure and geometric location. Lidar observed tides at a local station (tidal period perturbations) in the midlatitude mesopause region (80–105km) and the Climatological Tidal Model of the Thermosphere (CTMT) based on Hough Mode Extension (HME) technique at the lidar site, both of which include the effect of dissipation, are then compared. These tidal amplitudes and phases are employed to discuss the results and implications of the derived tidal wave polarization relations. The dominance of the migrating tide follows from the phase relationship between zonal and meridional wind tides. By comparing the observed and derived vertical wind tides, we reveal qualitatively the altitude dependence of tidal wave dissipation.


      PubDate: 2016-03-06T17:46:47Z
       
  • Global water cycle and solar activity variations
    • Abstract: Publication date: Available online 3 March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Muthanna A. Al-Tameemi, Vladimir V. Chukin
      The water cycle is the most active and most important component in the circulation of global mass and energy in the Earth system. Furthermore, water cycle parameters such as evaporation, precipitation, and precipitable water vapour play a major role in global climate change. In this work, we attempt to determine the impact of solar activity on the global water cycle by analyzing the global monthly values of precipitable water vapour, precipitation, and the Solar Modulation Potential in 1983–2008. The first object of this study was to calculate global evaporation for the period 1983–2008. For this purpose, we determined the water cycle rate from satellite data, and precipitation/evaporation relationship from 10 years of Planet Simulator model data. The second object of our study was to investigate the relationship between the Solar Modulation Potential (solar activity index) and evaporation for the period 1983–2008. The results showed that there is a relationship between the solar modulation potential and evaporation values for the period of study. Therefore, we can assume that the solar activity has an impact on the global water cycle.


      PubDate: 2016-03-06T17:46:47Z
       
  • Impact of Land-Use and Land-Cover Change on urban air quality in
           representative cities of China
    • Abstract: Publication date: May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 142
      Author(s): L. Sun, J. Wei, D.H. Duan, Y.M. Guo, D.X. Yang, C. Jia, X.T. Mi
      The atmospheric particulate pollution in China is getting worse. Land-Use and Land-Cover Change (LUCC) is a key factor that affects atmospheric particulate pollution. Understanding the response of particulate pollution to LUCC is necessary for environmental protection. Eight representative cities in China, Qingdao, Jinan, Zhengzhou, Xi’an, Lanzhou, Zhangye, Jiuquan, and Urumqi were selected to analyze the relationship between particulate pollution and LUCC. The MODIS (MODerate-resolution Imaging Spectroradiometer) aerosol product (MOD04) was used to estimate atmospheric particulate pollution for nearly 10 years, from 2001 to 2010. Six land-use types, water, woodland, grassland, cultivated land, urban, and unused land, were obtained from the MODIS land cover product (MOD12), where the LUCC of each category was estimated. The response of particulate pollution to LUCC was analyzed from the above mentioned two types of data. Moreover, the impacts of time-lag and urban type changes on particulate pollution were also considered. Analysis results showed that due to natural factors, or human activities such as urban sprawl or deforestation, etc., the response of particulate pollution to LUCC shows obvious differences in different areas. The correlation between particulate pollution and LUCC is lower in coastal areas but higher in inland areas. The dominant factor affecting urban air quality in LUCC changes from ocean, to woodland, to urban land, and eventually into grassland or unused land when moving from the coast to inland China.


      PubDate: 2016-03-06T17:46:47Z
       
  • Orientation variation of dayside auroral arc alignments obtained from
           all-sky observation at yellow river station, Svalbard
    • Abstract: Publication date: May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 142
      Author(s): Qi Qiu, Hui-Gen Yang, Quan-Ming Lu, Ze-Jun Hu, De-Sheng Han, Qian Wang
      The orientations of dayside auroral arc alignments were calculated for over 40,000 images from all-sky observation at Yellow River Station, Svalbard. For each arc, its “orientation” and “tilt” are defined as the angle the arc alignment makes with the dusk-dawn direction and the local east-west direction, respectively. The mean arc orientation increases linearly with the increasing magnetic local time (MLT). There is a reversal point of the arc tilt located at near 10.5 MLT. Compared with the mean orientation, auroral arc alignment tilts to morning side in the higher latitude and tilts to evening side in the lower latitude in the prenoon sector, whereas it is the opposite in the postnoon sector. We further studied the effects of the interplanetary magnetic field (IMF) on the location of the arc tilt reversal point. We found that the reversal position shifts toward the midday for negative By.


      PubDate: 2016-03-06T17:46:47Z
       
  • Observation of intensity of cosmic rays and daily magnetic shifts near
           meridian 70° in the south America
    • Abstract: Publication date: Available online 19 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): E.G. Cordaro, D. Gálvez, D. Laroze
      In analysis of experiments carried during September 2008 using secondary cosmic ray detectors located in Chacaltaya (Bolivia) and Niteroi (Brazil), Augusto et al. [Astroparticle Physics 34, 40 (2010)] showed an increase in the intensity of charged particles which takes place 3h after sunrise and lasts until 1h after sunset, furthermore they said that during this period the solar magnetic field lines overtake the Earth′s surface. These stations are located within the South Atlantic Magnetic Anomaly (SAMA), having both different magnetic rigidities. To reproduce data from the Niteroi and Chacaltaya stations, we record data during the same hours and days using our neutron monitors, muon telescopes and magnetometers within the stations Putre and Los Cerrillos. Our observation stations in Putre and Cerrillos are located at 18°11'47.8''S, 33°69''10.9''W at an altitude of 3,600m and 33⁰29'42.3''S, 70⁰42'59.81''W with 570m height above sea level, respectively. These stations are located within the South Atlantic Anomaly (SAMA) and are separated approximately 1700km from each other and 1700km from the center of the anomaly. Our network is composed furthermore by two auxiliary Cosmic Ray and/or Geomagnetic stations located at different latitudes along 70⁰W meridian, LARC and O'Higgins stations, which are located within Antarctic territory, covering a broad part of the Southern Hemisphere. Our magnetometer data shows that for each of the components, shifts in the magnetic field intensity for every station (even for those out of the SAMA) lasted between 3 to 4 hours after sunrise and 1 to 2 hours past sunset, which are the periods when the geomagnetic field is modulated by the transit of the dayside to nightside and nigthside to dayside. We believe that, although the magnetometric data indicates the magnetic reconnection for the Chilean region, there is no direct influence from the SAMA other than the lower rigidity cut-off that leads to an increased count rate. Other details about the magnetic field components such as muon and neutron count rate, diurnal variation and''sunset enhancement' are reported in this work.


      PubDate: 2016-02-23T17:02:22Z
       
  • Balloon-borne cryogenic frost-point hygrometer observations of water
           vapour in the tropical upper troposphere and lower stratosphere over
           India: First results
    • Abstract: Publication date: March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 140
      Author(s): S.V. Sunilkumar, M. Muhsin, Maria Emmanuel, Geetha Ramkumar, K. Rajeev, S. Sijikumar
      Balloon-borne cryogenic frost-point hygrometer (CFH) observations of water vapour in the upper troposphere and lower stratosphere (UTLS) region carried out over India, from Trivandrum [8.5°N, 76.9°E] and Hyderabad [17.5°N, 78.6°E], were compared with that obtained from quasi-collocated Aura-Microwave Limb Sounder (MLS) satellite observations. Comparisons show a small dry bias for MLS in the stratosphere. Saturated or super-saturation layers observed near the base of tropical tropopause layer (TTL) are consistent with the quasi-collocated space-based observations of tropical cirrus from KALPANA-1 and CALIPSO. Disturbance of large scale waves in the upper troposphere appears to modulate the water vapour and cirrus distribution.


      PubDate: 2016-02-23T17:02:22Z
       
  • Simulation of bulk aerosol direct radiative effects and its climatic
           feedbacks in South Africa using RegCM4
    • Abstract: Publication date: Available online 17 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M. Tesfaye, J. Botai, V. Sivakumar, G. Mengistu Tsidu, C.J.deW. Rautenbach, Shadung J. Moja
      In this study, twelve year runs of the Regional Climate Model (RegCM4) have been used to analyze the bulk aerosol radiative effects and its climatic feedbacks in South Africa. Due to the geographical locations where the aerosol potential source regions are situated and the regional dynamics, the South African aerosol spatial-distribution has a unique feature. Across the west and southwest areas, desert dust particles are dominant. However, sulfate and carbonaceous aerosols are primarily distributed over the east and northern regions of the country. Analysis of the Radiative Effects (RE) shows that in South Africa the bulk aerosols play a role in reducing the net radiation absorbed by the surface via enhancing the net radiative heating in the atmosphere. Hence, across all seasons, the bulk aerosol-radiation-climate interaction induced statistically significant positive feedback on the net atmospheric heating rate. Over the western and central parts of South Africa, the overall radiative feedbacks of bulk aerosol predominantly induces statistically significant Cloud Cover (CC) enhancements. Whereas, over the east and southeast coastal areas, it induces minimum reductions in CC. The CC enhancement and RE of aerosols jointly induce radiative cooling at the surface which in turn results in the reduction of Surface Temperature (ST: up to −1K) and Surface Sensible Heat Flux (SSHF: up to −24W/m2). The ST and SSHF decreases cause a weakening of the convectively driven turbulences and surface buoyancy fluxes which lead to the reduction of the boundary layer height, surface pressure enhancement and dynamical changes. Throughout the year, the maximum values of direct and semi-direct effects of bulk aerosol were found in areas of South Africa which are dominated by desert dust particles. This signals the need for a strategic regional plan on how to reduce the dust production and monitoring of the dust dispersion as well as it initiate the need of further research on different aspects of dust particle in South Africa.


      PubDate: 2016-02-23T17:02:22Z
       
  • A Review of Vertical Coupling in the Atmosphere-Ionosphere System: Effects
           of Waves, Sudden Stratospheric Warmings, Space Weather, and of Solar
           Activity
    • Abstract: Publication date: Available online 18 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Erdal Yiğit, Petra Koucká Knizová, Katya Georgieva, William Ward
      This brief introductory review of some recent developments in atmosphere-ionosphere science is written for the “Vertical Coupling Special Issue” that is motivated by the 5th IAGA/ICMA/SCOSTEP Workshop on Vertical Coupling in the Atmosphere-Ionosphere System. Basic processes of vertical coupling in the atmosphere-ionosphere system are discussed, focusing on the effects of internal waves, such as gravity waves and solar tides, sudden stratospheric warmings (SSWs), and of solar activity on the structure of the atmosphere. Internal waves play a crucial role in the current state and evolution of the upper atmosphere-ionosphere system. SSW effects extend into the upper atmosphere, producing changes in the thermospheric circulation and ionospheric disturbances. Sun, the dominant energy source for the atmosphere, directly impacts the upper atmosphere and modulates wave-induced coupling. The emphasis is laid on the most recent developments in the field, while giving credits to older works where necessary. Various international activities in atmospheric vertical coupling, such as SCOSTEP's ROSMIC project, and a brief contextual discussion of the papers published in the special issue are presented.


      PubDate: 2016-02-23T17:02:22Z
       
  • Evaluation of momentum flux with radar
    • Abstract: Publication date: Available online 15 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Dennis M. Riggin, Toshitaka Tsuda, Atsuki Shinbori
      The statistics of gravity wave momentum flux estimation are investigated using data from the MU radar at Shigariki, Japan (136°E, 35°N). The radar has been operating during campaign periods since 1986. The first part of the paper focuses on a multi-day campaign during October 13–31, 1986. The second part of the paper investigates data after 2006 when the radar was operated in a meteor scatter mode. Momentum fluxes are derived from both the turbulent scatter and the meteor scatter measurements, but the techniques are quite different. Probability Distribution Functions are formed using turbulent scatter data. These show that wave packets sometimes have momentum flux magnitudes in excess of 100m2 s−2. The technique for meteor radars, introduced by Hocking (2005), has been widely adopted by the radar community in recent years. The momentum flux estimated using this technique is found to be anti-correlated with the background tidal winds. A validation investigation is carried out for periods with a high meteor echo data rate. The conclusion was that the method can be used to calculate the sign of momentum flux, but does not accurately specify the magnitude.
      Graphical abstract image Highlights

      PubDate: 2016-02-17T16:45:39Z
       
  • Satellite observations of wave disturbances caused by moving solar
           TERMINATOR
    • Abstract: Publication date: Available online 17 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.V. Bespalova, A.K. Fedorenko, O.K. Cheremnykh, I.T. Zhuk
      Wave disturbances caused by moving solar terminator were studied using in situ satellite measurements. Neutral species densities measured by low-latitude satellite Atmosphere Explorer-E in the altitude range of 250–400km were used for analysis. Wave disturbances of neutral species density with amplitudes of 2-4% were observed during few hours after passing the terminator, predominantly in time intervals of 6-9 LST and 20-23 LST. These disturbances were interpreted as the acoustic-gravity waves. Spatial scales of such waves range from few hundred to few thousand kilometers, major part of wave spectral power being concentrated in the horizontal wavelength range from 1000km to 1200km. It was shown that vertical and horizontal components of phase velocity of these waves coincide with vertical and horizontal components of terminator velocity, i.e. observed wave are synchronized with the terminator.


      PubDate: 2016-02-17T16:45:39Z
       
  • Possible impact of solar activity on the convection dipole over the
           tropical pacific ocean
    • Abstract: Publication date: Available online 16 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Ziniu Xiao, Yunchen Liao, Chongyin Li
      The impact of solar activity (F10.7) on tropical Pacific convection during the boreal summer (June-July-August, JJA) has been examined using reanalysis data, revealing a significant lagged (1–2 years) correlation between outgoing long-wave radiation (OLR) over the tropical western Pacific and the F10.7 index. The OLR anomaly over the tropical western Pacific and the maritime continent shows a dipole pattern during the 1–2 years following high solar (HS) years. Furthermore, the first mode of the empirical orthogonal function (EOF) analysis on the OLR with the El Niño/Southern Oscillation (ENSO) signal removed is similar to the distribution of correlation coefficients between the JJA mean F10.7 index and the OLR with ENSO signal removed. The correlation and composite analyses of the OLR, velocity potential and vertical velocity reveals that this convection dipole pattern shows an eastward shift of the central position of deep convection, as related to the influence of solar activity over the tropical western Pacific. Further analyses show that the evolutionary process of the solar signal in the ocean-atmosphere system over the tropical western Pacific is consistent with the analyses of OLR, velocity potential, and vertical velocity. By modulating vertical air temperature, the solar signal in the tropical sea surface temperature (SST) may contribute to the triggering of a lagged convection dipole pattern.


      PubDate: 2016-02-17T16:45:39Z
       
  • Modeling and analysis of ionospheric evening Anomalies with a
           Physics-Based Data AssIMILATION Model
    • Abstract: Publication date: Available online 10 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Levan Lomidze, Ludger Scherliess, Robert W. Schunk
      Anomalous evening enhancements of electron densities in the mid-latitude ionosphere take place during summer and are most prominent over the west of the Antarctic Peninsula (Weddell Sea Anomaly). Although the phenomenon has been known for several decades, its generation mechanism is still being debated and its modeling remains a challenge. In this paper, data assimilation models were used to understand the role of thermospheric winds in the anomalies, and to elucidate the physical mechanism behind them. COSMIC radio occultation data were used and a newly developed Thermospheric Wind Assimilation Model (TWAM) was employed to estimate the horizontal wind components. Next, the TWAM winds were used to drive the Ionosphere-Plasmasphere Model to simulate the anomalies. The model results show close quantitative agreement with the COSMIC measurements and indicate that while the geographic meridional wind alone can drive the electron density evening peak, the zonal wind further enhances the anomaly. Furthermore, for closer agreement with the COSMIC data, the zonal wind effect was found to be important. To understand the physical mechanism behind the anomalies, the plasma production, loss and transport processes were analyzed. It was found that due to the equatorward wind during the evening, the density maximum forms at higher altitudes where the density reduction due to recombination is slow. Furthermore, it was revealed that during the evening, the plasma loss due to transport weakens. As a consequence of the reduced rate of recombination and the weakened plasma loss due to transport, the relative role of solar production increases and the electron density enhancement occurs.


      PubDate: 2016-02-12T16:35:16Z
       
  • Oscillations of a vertically stratified dissipative atmosphere. II. Low
           frequency trapped modes
    • Abstract: Publication date: Available online 11 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): G.V. Rudenko, I.S. Dmitrienko
      Trapped atmosphere waves, such as IGW waveguide modes and Lamb modes, are described using dissipative solution above source (DSAS) (Dmitrienko and Rudenko, 2016). According to this description, the modes are disturbances penetrating without limit in the upper atmosphere and dissipating their energy throughout the atmosphere; leakage from a trapping region to the upper atmosphere is taken into consideration. The DSAS results are compared to those based on both accurate and WKB approximated dissipationless equations. It is shown that the spatial and frequency characteristics of modes in the upper atmosphere calculated by any of the methods are close to each other and are in good agreement with the observed characteristics of traveling ionospheric disturbances.


      PubDate: 2016-02-12T16:35:16Z
       
  • Oscillations of a vertically stratified dissipative atmosphere. I.
           Solution above source
    • Abstract: Publication date: Available online 12 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): I.S. Dmitrienko, G.V. Rudenko
      A method of construction of solution for acoustic-gravity waves (AGW) above a wave source, taking dissipation throughout the atmosphere into account (dissipative solution above source, DSAS), is proposed. The method is to combine three solutions for three parts of the atmosphere: an analytical solution for the upper isothermal part and numerical solutions for the real non-isothermal dissipative atmosphere in the middle part and for the real non-isothermal small dissipation atmosphere in the lower one. In this paper the method has been carried out for the atmosphere with thermal conductivity but without viscosity. The heights of strong dissipation and the total absorption index in the regions of weak and average dissipation are found. For internal gravity waves the results of test calculations for an isothermal atmosphere and calculations for a real non-isothermal atmosphere are shown in graphical form. An algorithm and appropriate code to calculate DSAS, taking dissipation due to finite thermal conductivity into account throughout the atmosphere, are developed. The results of test DSAS calculations for an everywhere isothermal atmosphere are given. The calculation results for DSAS for the real non-isothermal atmosphere are also presented. A method for construction of the 2×2 Green's matrix fully taking dissipation into account and allowing us to find disturbance from some source of AGW in the atmosphere is proposed.


      PubDate: 2016-02-12T16:35:16Z
       
  • Spherical Slepian as a new method for ionospheric modeling in arctic
           region
    • Abstract: Publication date: March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 140
      Author(s): Hossein Etemadfard, Masoud Mashhadi Hossainali
      From the perspective of the physical, chemical and biological balance in the world, the Arctic has gradually turned into an important region opening ways for new researchers and scientific expeditions. In other words, various researches have been funded in order to study this frozen frontier in details. The current study can be seen in the same milieu where researchers intend to propose a set of new base functions for modeling ionospheric in the Arctic. As such, to optimize the Spherical Harmonic (SH) functions, the spatio-spectral concentration is applied here using the Slepian theory that was developed by Simons. For modeling the ionosphere, six International GNSS Service (IGS) stations located in the northern polar region were taken into account. Two other stations were left out for assessing the accuracy of the proposed model. The adopted GPS data starts at DOY 69 (Day of Year) and ends at DOY 83 (totally 15 successive days) in 2013. Three Spherical Slepian models respectively with the maximal degrees of K=15, 20 & 25 were used. Based on the results, K=15 is the optimum degree for the proposed model. The accuracy and precision of the Slepian model are about 0.1 and 0.05 TECU, respectively (TEC Unit=1016 electron/m2). To understand the advantage of this model, it is compared with polynomial and trigonometric series which are developed using the same set of measurements. The accuracy and precision of trigonometric and polynomial models are at least 4 times worse than the Slepian one.
      Graphical abstract image

      PubDate: 2016-02-08T20:52:51Z
       
  • Corrigendum to “Summer time Fe depletion in the Antarctic mesopause
           region” [J. Atmos. Sol.–Terr. Phys.
           127(2015)97–102]
    • Abstract: Publication date: Available online 5 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): T.P. Viehl, J. Höffner, F.-J. Lübken, J.M.C. Plane, B. Kaifler, R.J. Morris



      PubDate: 2016-02-08T20:52:51Z
       
  • Atmospheric changes observed during April 2015 Nepal earthquake
    • Abstract: Publication date: March 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 140
      Author(s): Nandita D. Ganguly
      A massive earthquake shook Nepal on 25 April 2015, with a moment magnitude of 7.9Mw, its hypocenter at a depth of 10km. Atmospheric changes that precede an earthquake might offer the hope of early warning and evacuation. Although the existence of such precursory signals is highly controversial, an attempt has been made to investigate the atmospheric changes from two months prior, to five months following this deadly earthquake. Aerosol optical depth (AOD) and columnar ozone were found to be higher by 40% and 6% respectively prior to the occurrence of the earthquake. The UV aerosol index (UVI), AOD and columnar NO2 increased, while columnar ozone and sea level pressure dropped following the earthquake.


      PubDate: 2016-02-08T20:52:51Z
       
  • Mesospheric signatures observed during 2010 minor stratospheric warming at
           king Sejong station (62° S, 59° W)
    • Abstract: Publication date: Available online 6 February 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): S. Eswaraiah, Yong Ha Kim, Junseok Hong, Jeong-Han Kim, M. Venkat Ratnam, A. Chandran, S.V.B. Rao, Dennis Riggin
      A minor stratospheric sudden warming (SSW) event was noticed in the southern hemisphere (SH) during September (day 259) 2010 along with two episodic warmings in early August (day 212) and late October (day 300) 2010. Among the three warming events, the signature of mesosphere response was detected only for the September event in the mesospheric wind dataset from both meteor radar and MF radar located at King Sejong Station (62°S, 59°W) and Rothera (68°S, 68°W), Antarctica, respectively. The zonal winds in the mesosphere reversed approximately a week before the September SSW event, as has been observed in the 2002 major SSW. Signatures of mesospheric cooling (MC) in association with stratospheric warmings are found in temperatures measured by the Microwave Limb Sounder (MLS). Simulations of specified dynamics version of Whole Atmosphere Community Climate Model (SD-WACCM) are able to reproduce these observed features. The mesospheric wind field was found to differ significantly from that of normal years probably due to enhanced planetary wave (PW) activity before the SSW. From the wavelet analysis of wind data of both stations, we find that strong 14−16 day PWs prevailed prior to the SSW and disappeared suddenly after the SSW in the mesosphere. Our study provides evidence that minor SSWs in SH can result in significant effects on the mesospheric dynamics as in the northern hemisphere.


      PubDate: 2016-02-08T20:52:51Z
       
  • A case study of A mesoscale gravity wave in the MLT region using
           simultaneous multi-instruments in Beijing
    • Abstract: Publication date: Available online 28 January 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Mingjiao Jia, Xianghui Xue, Xiankang Dou, Yihuan Tang, Chao Yu, Jianfei Wu, Jiyao Xu, Guotao Yang, Baiqi Ning, Lars Hoffmann
      In this work, we used observational data from an all-sky airglow imager at Xinglong (40.2°N, 117.4°E), a sodium lidar at Yanqing (40.4°N, 116.0°E) and a meteor radar at Shisanling (40.3°N, 116.2°E) to study the propagation of a mesoscale gravity wave. During the night of March 1, 2011, the imager identified a mesoscale gravity wave structure in the OH airglow that had a wave period of 2hours, propagated along an azimuthal direction (clockwise) with an angle of 163°, a phase speed of 73m/s, and a horizontal wavelength of 566km. Simultaneous measurements provided by the sodium lidar also showed a perturbation in the sodium layer with a 2-hour period. Based on the SABER/TIMED and radar data, we estimated that the momentum flux and the energy flux of the gravity wave were approximately 0.59m2/s2 and 0.22mW/m2, respectively. Ray-tracing analysis showed that the gravity wave was likely generated in the center of Lake Baikal owing to the existence of a jet- front system in the upper troposphere at that time.


      PubDate: 2016-01-28T20:11:43Z
       
  • Solar Daily Variation at Geomagnetic Observatories in Pakistan
    • Abstract: Publication date: Available online 26 January 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Rahim Zain, Kumbher Abdul Salam
      A study of solar daily variation is performed using the famous Chapman-Miller method for solar cycles 22 & 23 (1986-2007). The objective is to study the characteristics of Sq variation at Pakistani geomagnetic observatories using solar harmonics and a more traditional five quietest day's method. The data recorded at the Karachi geomagnetic observatory for SC 22 and 23 and data sets from other Pakistani geomagnetic observatories; Sonmiani, Quetta and Islamabad are analyzed for H, D and Z components of the geomagnetic field. Except for the D and Z components at Karachi and Sonmiani and H component at Islamabad, the two solar daily variations correlated well with each other. Also, the synthesized daily variation from the solar harmonics of H, D and Z components explained the equivalent Sq current system reasonably well for all seasons. For H component, the first solar harmonic (s1) obtained from spherical harmonic analysis of the data, appeared as the largest harmonic with no significant changes for the seasonal division of data. However, for D and Z components, amplitudes are comparable, but undergo distinct variations. s1 for H and D components increases with magnetic activity while for Z component it is the largest for the medium phase of magnetic activity. With the sunspot number division of data, the weighted mean of the Wolf ratio of all three components is in good agreement with the previous studies. The synthesized solar daily variation for D component, S(D), at Karachi, Sonmiani, Quetta and Islamabad did not show any signs of winter anomaly for the period studied. However, S(D) variation at Karachi during winter season showed morning minimum followed by a maximum at local noon and another minimum in the afternoon. We suggest this could be the effects of Equatorial Ionospheric Anomaly (EIA) observable at the Karachi observatory only during the winter season. Similarly, much disturbed in equinoctial and summer months, S(Z) illustrated an unwavering daily variation for the winter season at the Karachi observatory for both solar cycles. We find that it is the vertical component which is more strongly correlated with the mean monthly sunspot number and F10.7 solar radio flux. An interesting result obtained at Islamabad is the semi-diurnal variation of H component with a morning maximum and afternoon minimum and the phase reversal noticed for Z component variation. Attributed to an early eastward current this is, usually, observed for stations close to the Sq focus current system.


      PubDate: 2016-01-28T20:11:43Z
       
  • On the nature of IMF polarity dependent asymmetries in solar wind plasma
           properties during the minimum of sunspot cycles 23 and 24
    • Abstract: Publication date: Available online 22 January 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Felix Pereira B, Bijoy John Philip, Girish T. E
      The monthly solar wind speed and density observed near 1AU in IMF sectors of opposite magnetic polarity are studied during the minimum of sunspot cycles 23 and 24. During sunspot minima, the IMF is pointing away from the sun (Away sector) in the north of the Heliospheric Current Sheet (HCS) and pointing towards the sun (Toward sector) in the south of HCS during odd sunspot cycles and the same process is reversed during the even cycles. During this period, the solar wind plasma parameters (number density and speed) show a systematic month to month variation with solar wind number density decreases and velocity increases from equator to poles (heliomagnetic latitudinal organization) only in ‘Away’ IMF sectors compared to ‘Toward’ IMF sectors. This feature is particularly more evident for low speed solar wind and happens in a helio-hemisphere with a larger polar coronal hole. The association of the above phenomena with north-south asymmetry in coronal and solar wind flow characteristics will be discussed.


      PubDate: 2016-01-23T20:03:28Z
       
  • Investigation of gravity wave activity based on operational radiosonde
           data from 13 years (1997-2009): Climatology and possible induced
           variability
    • Abstract: Publication date: Available online 23 January 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R. Kramer, S. Wüst, M. Bittner
      Atmospheric gravity waves (GWs) are important for the dynamics of the atmosphere. The analysis of 13 years of routine radiosonde data from Prague (50.01°N, 14.27°E) with temporal highly resolved temperature, pressure and wind measurements is presented in order to derive a climatology of gravity wave activity in the lower stratosphere. An annual cycle with a maximum during winter and a minimum during summer is identified. Gravity wave activity is twice as high during winter as during summer. Winter periods are investigated by wavelet analysis. They show similar periods in vertical flux of horizontal momentum and pressure variance time series. These features may be attributed to planetary waves. When analyzing individual years, maxima of gravity wave activity and vertical flux of horizontal momentum often appears together with minima in surface pressure. We speculate therefore that at least parts of the interannual variations of gravity wave activity may due to cyclones.


      PubDate: 2016-01-23T20:03:28Z
       
 
 
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