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  Subjects -> METEOROLOGY (Total: 88 journals)
Showing 1 - 36 of 36 Journals sorted alphabetically
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 26)
Advances in Climate Change Research     Open Access   (Followers: 1)
Advances in Meteorology     Open Access   (Followers: 13)
Aeolian Research     Hybrid Journal   (Followers: 5)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 11)
American Journal of Climate Change     Open Access   (Followers: 9)
Asian Journal of Earth Sciences     Open Access   (Followers: 19)
Atmósfera     Open Access   (Followers: 1)
Atmosphere     Open Access   (Followers: 15)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 11)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 13)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 6)
Atmospheric Research     Hybrid Journal   (Followers: 33)
Atmospheric Science Letters     Open Access   (Followers: 21)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 15)
Bulletin of the American Meteorological Society     Open Access   (Followers: 23)
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: 10)
Climate Change Responses     Open Access  
Climate Dynamics     Hybrid Journal   (Followers: 16)
Climate law     Hybrid Journal   (Followers: 4)
Climate of the Past (CP)     Open Access   (Followers: 4)
Climate of the Past Discussions (CPD)     Open Access   (Followers: 1)
Climate Policy     Hybrid Journal   (Followers: 28)
Climate Research     Hybrid Journal   (Followers: 4)
Climate Risk Management     Open Access  
Climate Services     Open Access  
Climate Summary of South Africa     Full-text available via subscription  
Climatic Change     Hybrid Journal   (Followers: 43)
Current Climate Change Reports     Hybrid Journal  
Developments in Atmospheric Science     Full-text available via subscription   (Followers: 9)
Dynamics and Statistics of the Climate System     Open Access  
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 8)
Earth Perspectives - Transdisciplinarity Enabled     Open Access  
Energy & Environment     Full-text available via subscription   (Followers: 15)
Environmental and Climate Technologies     Open Access   (Followers: 3)
Global Meteorology     Open Access   (Followers: 3)
International Journal of Atmospheric Sciences     Open Access   (Followers: 8)
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: 19)
International Journal of Image and Data Fusion     Hybrid Journal   (Followers: 1)
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (Followers: 15)
Journal of Atmospheric and Oceanic Technology     Full-text available via subscription   (Followers: 17)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 28)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 6)
Journal of Climate     Full-text available via subscription   (Followers: 26)
Journal of Climatology     Open Access   (Followers: 1)
Journal of Hydrology and Meteorology     Open Access   (Followers: 6)
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: 5)
Journal of Space Weather and Space Climate     Open Access   (Followers: 7)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 43)
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: 10)
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: 48)
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: 5)
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: 15)
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]   [28 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [2970 journals]
  • Bottom-side profile parameters (B0, B1) characteristics over the brazilian
           equatorial and low latitudes and their comparison with different options
           in the IRI-2012 model during the 24th solar minimum (2010-2011)
    • Abstract: Publication date: Available online 12 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): K. Venkatesh, P.R. Fagundes
      The present study reports the characteristics of the bottom-side profile thickness (B0) and shape (B1) parameters from ionosonde and IRI-2012 model over the Brazilian sector. The ionosonde data from an equatorial station Fortaleza and a low latitude station Cachoera Paulista during a two year period from 2010 to 2011 are considered in this study. Simultaneous comparison is made on the performance of three different options ‘Gul-1987’, ‘Bil-2000’ and the ‘ABT-2009’ for bottom-side profile estimation in the latest available IRI-2012. The diurnal and seasonal characteristics of the B0 and B1 from ionosonde measurements are studied and compared with those from the IRI-2012 model using the three different options. It is seen that the Gul-1987 method shows better predictions of the observed B0 at the equatorial and low latitudes values when compared with the other options. The latest option ‘ABT-2009’ has shown improved predictions in the estimation of B1 compared with those from the other methods particularly during the night-time hours. A comparison on the seasonal characteristics of the day maximum values of B0 between observations and the three different options in IRI-2012 reveals that the Gul-1987 method shows better predictions of the seasonal variations in B0 while ABT-2009 method shows better predictions of seasonal variations in B1. Further, an insight into the percentage of deviations in the estimation of B0 and B1 reveals that the models overestimate the B0 during night-time and underestimate the B0 (at equator) during day-time while they underestimate the B1 during night-time hours at both locations. Also, the variations in the bottom-side total electron content are studied using the three different methods in the IRI-2012 model and compared with those derived from the ionosonde observations.


      PubDate: 2016-05-15T15:15:42Z
       
  • An ionospheric assimilation model along a meridian plane
    • Abstract: Publication date: Available online 7 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Huijun Le, Libo Liu, Zhipeng Ren, Lianhuan Hu, Yiding Chen, Weixing Wan
      In this paper, we developed a two-dimensional ionospheric assimilation model that assimilates the observations of peak electron density of F2-layer (NmF2) and the peak height of F2-layer (hmF2) derived from five ionosonde stations along the 120°E meridian, using three-dimensional variation techniques (3DVAR) based on a physics-based ionosphere theoretical model. The assimilation system can well produce the assimilated results along the 120°E meridian plane by using the data of NmF2 and hmF2 at five ionosonde stations from Mohe (52.0°N) to Sanya (18.3°N). The root mean square error (RMSE) between the analysis results of the assimilation model and the ionosonde observations is much lower than that between the results from international reference ionosphere (IRI) and the ionosonde observations. In addition, we carried out the assimilation test by taking the IRI results as the observations to check the assimilated results in the regions without observations. The assimilated result in the southern hemisphere (RMSE=0.29) is much worse than that in the northern hemisphere (RMSE=0.10) because no observations in the southern hemisphere were used. If the data derived from the four ionosonde stations in Australia are used, the assimilated result in the southern hemisphere would be much more accurate. In addition to NmF2 and hmF2, the assimilation model can also adjust the total electron content (TEC). The RMSE between the TEC after assimilation and the observed GPS TEC is much lower than that between the TEC from the IRI model and the observed GPS TEC.


      PubDate: 2016-05-09T20:52:04Z
       
  • Rain rate intensity model for communication link design for indian region
    • Abstract: Publication date: Available online 7 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Aravind. Kilaru, Sarat K Kotamraju, Nicholas Avlonitis, K.Ch. Sri Kavya
      A study on rain statistical parameters such as one minute rain intensity, possible number of minute occurrences with respective percentage of time in a year has been evaluated for the purpose of communication link design at Ka, Q, V bands as well as at Free-Space Optical communication links (FSO). To understand possible outage period of a communication links due to rainfall and to investigate rainfall pattern, Automatic Weather Station (AWS) rainfall data is analysed due its ample presence across India. The climates of the examined AWS regions vary from desert to cold climate, heavy rainfall to variable rainfall regions, cyclone effective regions, mountain and coastal regions. In this way a complete and unbiased picture of the rainfall statistics for Indian region is evaluated. The analysed AWS data gives insight into yearly accumulated rainfall, maximum hourly accumulated rainfall, mean hourly accumulated rainfall, number of rainy days and number of rainy hours from 668 AWS locations. Using probability density function the one minute rainfall measurements at KL University is integrated with AWS measurements for estimating number of rain occurrences in terms of one minute rain intensity for annual rainfall accumulated between 100 mm to 5000mm to give an insight into possible one minute accumulation pattern in an hour for comprehensive analysis of rainfall influence on a communication link for design engineers. So that low availability communications links at higher frequencies can be transformed into a reliable and economically feasible communication links for implementing High Throughput Services (HTS).


      PubDate: 2016-05-09T20:52:04Z
       
  • Substorm probabilities are best predicted from solar wind speed
    • Abstract: Publication date: Available online 6 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): P.T. Newell, K. Liou, J.W. Gjerloev, T. Sotirelis, S. Wing, E.J. Mitchell
      Most measures of magnetospheric activity – including auroral power (AP), magnetotail stretching, and ring current intensity – are best predicted by solar wind-magnetosphere coupling functions which approximate the frontside magnetopause merging rate. However radiation belt fluxes are best predicted by a simpler function, namely the solar wind speed, v. Since most theories of how these high energy electrons arise are associated with repeated rapid dipolarizations such as associated with substorms, this apparent discrepancy could be reconciled under the hypothesis that the frequency of substorms tracks v rather than the merging rate – despite the necessity of magnetotail flux loading prior to substorms. Here we investigate this conjecture about v and substorm probability. Specifically, a continuous list of substorm onsets compiled from SuperMAG covering January 1, 1997 through December 31, 2007 are studied. The continuity of SuperMAG data and near continuity of solar wind measurements minimize selection bias. In fact v is a much better predictor of onset probability than is the overall merging rate, with substorm odds rising sharply with v. Some loading by merging is necessary, and frontside merging does increase substorm probability, but nearly as strongly as does v taken alone. Likewise, the effects of dynamic pressure, p, are smaller than simply v taken by itself. Changes in the solar wind matter, albeit modestly. For a given level of v (or B z ), a change in v (or B z ) will increase the odds of a substorm for at least 2h following the change. A decrease in driving elevates substorm probabilities to a greater extent than does an increase, partially supporting external triggering. Yet current v is the best single predictor of subsequently observing a substorm. These results explain why geomagnetically quiet years and active years are better characterized by low or high v (respectively) than by the distribution of merging estimators. It appears that the flow of energy through the magnetosphere is determined by frontside merging, but the burstiness of energy dissipation depends primarily on v.


      PubDate: 2016-05-09T20:52:04Z
       
  • Characteristics of the most intense lightning storm ever recorded at the
           CN tower
    • Abstract: Publication date: Available online 7 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.M. Hussein, S. Kazazi, M. Anwar, M. Yusouf, P. Liatos
      Lightning strikes to the CN Tower have been optically observed since 1978. In 1990, five independent systems started to operate to simultaneously record parameters of lightning strikes to the tower, including the time derivative of the current, the associated electric and magnetic fields, and the channel optical characteristics. On August 24, 2011, during an unusually severe lightning storm, video records showed that the CN Tower was struck with 52 lightning flashes within 84 minutes and 6.9 seconds. Thus, this storm produced, on average, a flash to the tower every 99 seconds. However, the CN Tower lightning current derivative measurement system only recorded 32 flashes, which were perfectly time-matched with 32 of the 52 video-recorded flashes. It is found that the current derivative measurement system recorded every video-recorded flash that contained at least one return stroke. Based on the analysis of video records, it is noted that each of the storm's 52 flashes contains an initial-stage current, proving that all flashes were upward initiated. This unique CN Tower storm – the most intense ever recorded at the tower – is here thoroughly analyzed, based on video and current records. The inter-flash time within the storm is found to vary between 10.6 s and 274 s, with an overall average of 98 s. It is also found that the inter-flash time between successive non-return-stroke flashes is on average 64% longer than that for successive flashes containing return strokes. Statistical analysis of video and current data clearly reveals that the time duration of flashes containing initial-stage currents and return strokes is on average 27% longer than that of flashes that only have initial-stage currents. Furthermore, it is important to note that the time duration of the initial-stage current in flashes containing no return strokes is on average 76% longer than that in flashes containing return strokes. Therefore, it is possible to conclude that if the time duration of the initial-stage current in a flash is long enough, resulting in large charge transfer, then there is less probability of having return strokes following it. The 32 current-recorded flashes contain a total of 156 return strokes, with an average multiplicity of 4.875. It is worth mentioning that during one decade, 1992-2001, the CN Tower current derivative measurement system only recorded 478 return strokes, demonstrating that the number of return strokes recorded at the tower within about 84 minutes is close to one third of those recorded at the tower during one decade. This finding clearly shows the great value and rarity of the presented extensive lightning current derivative data. Only one of the 32 current-recorded flashes is proved to be positive with a single return stroke. Based on current records, out of a total of 124 inter-stroke time intervals, 94% are found to be within 200ms, with an overall inter-stroke time average of 68.1ms. The maximum inter-stroke time recorded during this storm is 726.3ms, the longest ever recorded at the CN Tower.


      PubDate: 2016-05-09T20:52:04Z
       
  • Atmospheric ionization induced by precipitating electrons: Comparison of
           CRAC:EPII model with a parametrization model
    • Abstract: Publication date: Available online 7 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.A. Artamonov, A.L. Mishev, I.G. Usoskin
      Results of a comparison of a new model CRAC:EPII (Cosmic Ray Atmospheric Cascade: Electron Precipitation Induced Ionization) with a commonly used parametric model of atmospheric ionization is presented. The CRAC:EPII is based on a Monte Carlo simulation of precipitating electrons propagation and interaction with matter in the Earth's atmosphere. It explicitly considers energy deposit: ionization, pair production, Compton scattering, generation of Bremsstrahlung high energy photons, photo-ionization and annihilation of positrons, multiple scattering as physical processes accordingly. Propagation of precipitating electrons and their interactions with air is simulated with the GEANT4 simulation tool PLANETOCOSMICS code using NRLMSISE00 atmospheric model. Ionization yields are computed and compared with a parametrization model for different energies of incident precipitating energetic electrons, using simulated fluxes of mono-energetic particles. A good agreement between the two models is achieved in the mesosphere but the contribution of Bremsstrahlung in the stratosphere, which is not accounted for in the parametric models, is found significant. As an example, we calculated profiles of the ion production rates in the middle and upper atmosphere (below 100km) on the basis of balloon-born measured spectra of precipitating electrons for 30-Oct-2002 and 07-Jan-2004.


      PubDate: 2016-05-09T20:52:04Z
       
  • Equatorward evolution of auroras from the poleward auroral boundary
    • Abstract: Publication date: Available online 29 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): O. Saka, K. Hayashi, M.F. Thomsen
      An all-sky imager installed at the midnight sector in Dawson City (66.0° in geomagnetic latitude) recorded the equatorward evolution of auroras from the auroral poleward boundary. The auroras evolved as shear layers expanding southeastward with velocities of 1 to 4km/s, referred to as N-S auroras, and occurred during the transient intensification of the convection electric fields in the nighttime magnetosphere, as inferred from an electron spectrogram at geosynchronous altitudes. A continuous increase in the inclination angle of the field lines and magnetic field perturbations associated with propagating ionospheric loop currents were observed in the auroral zone during the N-S auroras. Simultaneously, Pc4 pulsations were observed at low latitudes from night to day sectors. We conclude the following: (1) the N-S auroras are an auroral manifestation of the earthward drift of plasma sheet electrons in the equatorial plane associated with transient and localized convection electric fields; (2) the Pc4 pulsations are produced in the magnetosphere by plasma sheet ions in the plasmasphere. The localized convection fields produce a vortical motion of plasmas in the equatorial plane, which may initiate the N-S auroras and ionospheric loop currents in the auroral zone.


      PubDate: 2016-05-04T20:27:09Z
       
  • Features of Positive Ground Flashes Observed in Kathmandu Nepal
    • Abstract: Publication date: Available online 1 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Pitri Bhakta Adhikari, Shriram Sharma, Kedarnath Baral
      Lightning vertical electric fields pertinent to the subtropical thunderstorms occuring over the rugged terrain have been measured and recorded at a hilly station Kathmandu, Nepal. In the present work, waveforms of the positive ground flashes have been selected from all the records and were analyzed. To the best of our knowledge, this is the first time that fine structure of electric field signature pertinent to the positive return stroke; have been analyzed and presented from Nepal. One hundred and thirty three (133) of the total of four hundred twenty-five (425) flashes were selected from seven thunderstorm days and analyzed. Of the data recorded for seven days, 133 flashes (31.3%) were positive flashes and 276 flashes (64.9%) were cloud flashes. Majority of the positive ground flashes were found to be single stroke ones, whereas, the average number of strokes per flash is found to be 1.1 with a maximum value of 4. Majority of the positive ground flashes were found either lacking the initial breakdown process and the leader stage or these processes could not be detected. The return strokes are found to be succeded by large incloud activity in the continuing current portion of the flash. The average zero-crossing time of the positive return strokes was found to be 60.45µs with a range of 447.81µs and the average rise time was found to be 9.44µs with a range of 42.56µs.


      PubDate: 2016-05-04T20:27:09Z
       
  • The influence of Middle Range Energy Electrons on atmospheric chemistry
           and regional climate
    • Abstract: Publication date: Available online 13 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): P. Arsenovic, E. Rozanov, A. Stenke, B. Funke, J.M. Wissing, K. Mursula, F. Tummon, T. Peter
      We investigate the influence of Middle Range Energy Electrons (MEE; typically 30-300keV) precipitation on the atmosphere using the SOCOL3-MPIOM chemistry-climate model with coupled ocean. Model simulations cover the 2002-2010 period for which ionization rates from the AIMOS dataset and atmospheric composition observations from MIPAS are available. Results show that during geomagnetically active periods MEE significantly increase the amount of NO y and HO x in the polar winter mesosphere, in addition to other particles and sources, resulting in local ozone decreases of up to 35%. These changes are followed by an intensification of the polar night jet, as well as mesospheric warming and stratospheric cooling. The contribution of MEE also substantially enhances the difference in the ozone anomalies between geomagnetically active and quiet periods. Comparison with MIPAS NO y observations indicates that the additional source of NO y from MEE improves the model results, however substantial underestimation above 50km remains and requires better treatment of the NO y source from the thermosphere. A surface air temperature response is detected in several regions, with the most pronounced warming occurring in the Antarctic during austral winter. Surface warming of up to 2K is also seen over continental Asia during boreal winter.


      PubDate: 2016-05-04T20:27:09Z
       
  • Comparing the influence of sunspot activity and geomagnetic activity on
           winter surface climate
    • Abstract: Publication date: Available online 23 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): I. Roy, T. Asikainen, V. Maliniemi, K. Mursula
      We compare here the effect of geomagnetic activity (using the aa index) and sunspot activity on surface climate using sea level pressure dataset from Hadley centre during northern winter. Previous studies using the multiple linear regression method have been limited to using sunspots as a solar activity predictor. Sunspots and total solar irradiance indicate a robust positive influence around the Aleutian Low. This is valid up to a lag of one year. However, geomagnetic activity yields a positive NAM pattern at high to polar latitudes and a positive signal around Azores High pressure region. Interestingly, while there is a positive signal around Azores High for a 2-year lag in sunspots, the strongest signal in this region is found for aa index at 1-year lag. There is also a weak but significant negative signature present around central Pacific for both sunspots and aa index. The combined influence of geomagnetic activity and Quasi Biannual Oscillation (QBO 30 hPa) produces a particularly strong response at mid to polar latitudes, much stronger than the combined influence of sunspots and QBO, which was mostly studied in previous studies so far. This signal is robust and insensitive to the selected time period during the last century. Our results provide a useful way for improving the prediction of winter weather at middle to high latitudes of the northern hemisphere.


      PubDate: 2016-05-04T20:27:09Z
       
  • Validation of NeQuick 2 model over the kenyan region through data
           ingestion and the model application in ionospheric studies
    • Abstract: Publication date: Available online 26 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): O. J Olwendo, C Cesaroni
      NeQuick 2 is an ionospheric electron density model which provides electron density for a given location. Its output depends on solar activity expressed by 12-month running average sunspot number (R12) or solar radio flux (F10.7). To improve the model capabilities to reproduce electron density, data ingestion techniques have been implemented which replace the standard solar activity indices input with effective parameters that allow adapting a model to a certain data sets. In regions like the Sub-Saharan Africa where few observational data were available until recently, the performance of the ingested model needs some validation. This study investigates the performance of NeQuick 2 in the Kenya region, a low latitude region by assisting the model with total electron content measurement from a single GNSS station. These measurements are used to calculate effective ionization level parameters, which enable the difference between the measured and modelled TEC over the station to be less or equal to 0.5 TECU. The results show that by using computed effective parameters values as inputs in nearby stations, the model performance is greatly improved for both the low and moderate solar activity. This work has also demonstrated the capability of the model to describe spatial distribution of the total electron content in the low- latitude ionosphere.


      PubDate: 2016-05-04T20:27:09Z
       
  • Large ice particles associated with small ice water content observed by
           AIM CIPS imagery of polar mesospheric clouds: Evidence for microphysical
           coupling with small-scale dynamics
    • Abstract: Publication date: Available online 2 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): D. Rusch, G. Thomas, A. Merkel, J. Olivero, A. Chandran, J. Lumpe, J. Carstans, C. Randall, S. Bailey, J. Russell
      Observations by the Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite have demonstrated the existence of Polar Mesospheric Cloud (PMC) regions populated by particles whose mean sizes range between 60 and 100nm (radii of equivalent volume spheres). It is known from numerous satellite experiments that typical mean PMC particle sizes are of the order of 40–50nm. Determination of particle size by CIPS is accomplished by measuring the scattering of solar radiation at various scattering angles at a spatial resolution of 25km2. In this size range we find a robust anti-correlation between mean particle size and albedo. These very-large particle-low-ice (VLP-LI) clouds occur over spatially coherent areas. The surprising result is that VLP-LI are frequently present either in the troughs of gravity wave-like features or at the edges of PMC voids. We postulate that an association with gravity waves exists in the low-temperature summertime mesopause region, and illustrate the mechanism by a gravity wave simulation through use of the 2D Community Aerosol and Radiation Model for Atmospheres (CARMA). The model results are consistent with a VLP-LI population in the cold troughs of monochromatic gravity waves. In addition, we find such events in Whole Earth Community Climate Model/CARMA simulations, suggesting the possible importance of sporadic downward winds in heating the upper cloud regions. This newly-discovered association enhances our understanding of the interaction of ice microphysics with dynamical processes in the upper mesosphere.


      PubDate: 2016-05-04T20:27:09Z
       
  • Impacts of Air–Sea Exchange Coefficients on Snowfall Events over the
           Korean Peninsula
    • Abstract: Publication date: Available online 2 May 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jung-Yoon Kang, Young Cheol Kwon
      Snowfall over the Korean Peninsula is mainly associated with air mass transformation by the fluxes across the air–sea interface during cold-air outbreaks over the warm Yellow Sea. The heat and momentum exchange coefficients in the surface flux parameterization are key parameters of flux calculations across the air–sea interface. This study investigates the effects of the air–sea exchange coefficients on the simulations of snowfall events over the Korean Peninsula using the Weather Research and Forecasting (WRF) model. Two snowfall cases are selected for this study. One is a heavy snowfall event that took place on January 4, 2010, and the other is a light snowfall event that occurred on December 23–24, 2011. Several sensitivity tests are carried out with increased and decreased heat and momentum exchange coefficients. The domain-averaged precipitation is increased (decreased) with increased (decreased) heat exchange coefficient because the increased (decreased) surface heat flux leads to more (less) moist conditions in the low level of the atmosphere. On the other hand, the domain-averaged precipitation is decreased (increased) with increased (decreased) momentum exchange coefficient because the increased (decreased) momentum coefficient causes reduction (increase) of wind speed and heat flux. The variation of precipitation in the heat exchange coefficient experiments is much larger than that in the momentum exchange coefficient experiments because the change of heat flux has a more direct impact on moisture flux and snowfall amount, while the change of momentum flux has a rather indirect impact via wind speed changes. The low-pressure system is intensified and moves toward North when the heat exchange coefficient is increased because warming and moistening of the lower atmosphere contributes to destabilize the air mass, resulting in the change of precipitation pattern over the Korean Peninsula in the heat exchange coefficient experiments.


      PubDate: 2016-05-04T20:27:09Z
       
  • IFC-Ed. board
    • Abstract: Publication date: June 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 143–144




      PubDate: 2016-05-04T20:27:09Z
       
  • Identifying the occurrence of lightning and transient luminous events by
           nadir spectrophotometric observation
    • Abstract: Publication date: July 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 145
      Author(s): Toru Adachi, Mitsuteru Sato, Tomoo Ushio, Atsushi Yamazaki, Makoto Suzuki, Masayuki Kikuchi, Yukihiro Takahashi, Umran S. Inan, Ivan Linscott, Yasuhide Hobara, Harald U. Frey, Stephen B. Mende, Alfred B. Chen, Rue-Ron Hsu, Kenichi Kusunoki
      We propose a new technique to identify the occurrence of lightning and transient luminous events (TLEs) using multicolor photometric data obtained by space borne nadir measurements. We estimate the spectral characteristics of lightning and TLEs by converting the optical data obtained by the ISUAL limb experiment to the GLIMS nadir geometry. We find that the estimated spectral shapes of TLE-accompanied lightning are clearly different from those of pure lightning. The obtained results show that (1) the intensity of FUV signals and (2) the ratio of 337/red (609–753nm) spectral irradiance are useful to identify the occurrence of TLEs. The occurrence probabilities of TLEs are 10%, 40%, 80%, in the case of lightning events having the 337/red spectral irradiance ratio of 0.95, 2.95, 14.79, respectively. By using the 60% criterion of the 337/red ratio and the existence of FUV emissions, we classify the 1039 GLIMS-observed lightning events into 828 pure lightning and 211 TLE-accompanied lightning. Since the GLIMS trigger level is adjusted to observe extremely-bright events, the occurrence probability of TLEs obtained here most probably reflects the characteristics of energetic lightning. The estimated global map is consistent with previously determined distributions: the highest activities of lightning and TLEs are found over the North/South American continents, African continent, and Asian maritime regions. While the absolute occurrence number of pure lightning and TLE-accompanied lightning are found to maximize in the equatorial region, the occurrence probability of TLEs possibly increase somewhat in the mid-latitude region. Since the occurrence probabilities of TLEs are higher over the ocean than over land, it is likely that the GLIMS-observed TLEs are due primarily to elves which tends to occur more frequently over the ocean.


      PubDate: 2016-05-04T20:27:09Z
       
  • Particle precipitation: How the spectrum fit impacts atmospheric chemistry
    • Abstract: Publication date: Available online 26 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): J.M. Wissing, H. Nieder, O.S. Yakovchouk, M. Sinnhuber
      Particle precipitation causes atmospheric ionization. Modeled ionization rates are widely used in atmospheric chemistry/climate simulations of the upper atmosphere. As ionization rates are based on particle measurements some assumptions concerning the energy spectrum are required. While detectors measure particles binned into certain energy ranges only, the calculation of a ionization profile needs a fit for the whole energy spectrum. Therefore the following assumptions are needed: (a) fit function (e.g. power-law or Maxwellian), (b) energy range, (c) amount of segments in the spectral fit, (d) fixed or variable positions of intersections between these segments. The aim of this paper is to quantify the impact of different assumptions on ionization rates as well as their consequences for atmospheric chemistry modeling. As the assumptions about the particle spectrum are independent from the ionization model itself the results of this paper are not restricted to a single ionization model, even though the Atmospheric Ionization Module OSnabrück (Aimos, Wissing and Kallenrode, 2009) is used here. We include protons only as this allows us to trace changes in the chemistry model directly back to the different assumptions without the need to interpret superposed ionization profiles. However, since every particle species requires a particle spectrum fit with the mentioned assumptions the results are generally applicable to all precipitating particles. The reader may argue that the selection of assumptions of the particle fit is of minor interest, but we would like to emphasize on this topic as it is a major, if not the main, source of discrepancies between different ionization models (and reality). Depending on the assumptions single ionization profiles may vary by a factor of 5, long-term calculations may show systematic over- or underestimation in specific altitudes and even for ideal setups the definition of the energy-range involves an intrinsic 25% uncertainty for the ionization rates. The effects on atmospheric chemistry (HO x , NO x and Ozone) have been calculated by 3dCTM, showing that the spectrum fit is responsible for a 8% variation in Ozone between setups, and even up to 50% for extreme setups.


      PubDate: 2016-05-04T20:27:09Z
       
  • Global structure of ionospheric TEC anomalies driven by geomagnetic storms
    • Abstract: Publication date: Available online 29 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): D. Pancheva, P. Mukhtarov, B. Andonov
      This study examines the structure and variability of the ionospheric TEC anomalies driven by geomagnetic storms. For this purpose the CODE global ionospheric TEC data from four geomagnetically disturbed periods (29 October-1 November 2003, 7–10 November 2004, 14-15 December 2006, and 5-6 August 2011) have been considered. By applying the tidal analysis to the geomagnetically forced TEC anomalies we made an attempt to identify the tidal or stationary planetary wave (SPW) signatures that may contribute to the generation of these anomalies. It has been found that three types of positive anomalies with different origin and different latitudinal appearance are observed. These are: (i) anomalies located near latitudes of ±40° and related to the enhancement and poleward moving of the equatorial ionization anomaly (EIA) crests; (ii) anomalies located near latitudes of ±60° and seen predominantly in the night-side ionosphere, and (iii) very high latitude anomalies having mainly zonally symmetric structure and related to the auroral heating and thermospheric expansion. The decomposition analysis revealed that these anomalies can be reconstructed as a result of superposition of the following components: zonal mean (ZM), diurnal migrating (DW1), zonally symmetric diurnal (D0), and stationary planetary wave 1 (SPW1).


      PubDate: 2016-05-04T20:27:09Z
       
  • Probing geomagnetic storm-driven magnetosphere-ionosphere dynamics in
           D-region via propagation characteristics of very low frequency radio
           signals
    • Abstract: Publication date: Available online 29 April 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Victor U.J. Nwankwo, Sandip K. Chakrabarti, Olugbenga Ogunmodimu
      The amplitude and phase of VLF/LF radio signals are sensitive to changes in electrical conductivity of the lower ionosphere which imprints its signature on the Earth-ionosphere waveguide. This characteristics makes it useful in studying sudden ionospheric disturbances, especially those related to prompt X-ray flux output from solar flares and gamma ray bursts (GRBs). However, strong geomagnetic disturbance and storm conditions are known to produce large and global ionospheric disturbances, which can significantly affect VLF radio propagation in the D region of the ionosphere. In this paper, using the data of three propagation paths at mid-latitudes (40° – 54°), we analyze the trend of aspects of VLF diurnal signal under varying solar and geomagnetic space environmental conditions in order to identify possible geomagnetic footprints on the D region characteristics. We found that the trend of variations generally reflect the prevailing space weather conditions in various time scales. In particular, the ‘dipping’ of mid-day signal amplitude (MDP) of VLF always occurs after geomagnetic perturbed or storm conditions in the time scale of 1–2days. The mean signal before sunrise (MBSR) and mean signal after sunset (MASS) also exhibit storm-induced dipping, but they appear to be influenced by event's exact occurrence time and highly variable conditions of dusk-to-dawn ionosphere. We observed fewer cases of the signals rise (e.g., MDP, MBSR or MASS) following a significant geomagnetic event, though this effect may be related to storms associated phenomena or effects arising from sources other than solar origin. The magnitude of induced dipping (or rise) significantly depends on the intensity and duration of event(s), as well as the propagation path of the signal. The post-storm day signal (following a main event, with lesser or significantly reduced geomagnetic activity), exhibited a tendency of recovery to pre-storm day level. In the present analysis, We do not see a well defined trend of the variations of the post-storm sunrise terminator (SRT) and sunset terminator (SST). The SRT and SST signals show more post-storm dipping in GQD-A118 propagation path but generally an increase along DHO-A118 propagation path. Thus the result could be propagation path dependent and detailed modeling is required to understand these phenomena.


      PubDate: 2016-05-04T20:27:09Z
       
  • Study of high-latitude ionosphere: One-year campaign over Husafell,
           Iceland
    • Abstract: Publication date: July 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 145
      Author(s): S.A. Bahari, M. Abdullah, A.M. Hasbi, B. Yatim, W. Suparta, A. Kadokura, G. Bjornsson
      This paper reports on the effects of diurnal, seasonal, geomagnetic and solar activity on GPS Vertical Total Electron Content (VTEC) measurements at a high-latitude station in Husafell, Iceland (64.7°N, 21.0°W) from March 2009 to February 2010. According to the diurnal VTEC pattern, there was generally a build-up region at sunrise (0500-1000 LT), a daytime plateau in the afternoon (1200-1400 LT), and a decay region from evening to pre-dawn (1800-0400 LT). The month-to-month analysis showed high VTEC variability, particularly in February 2010, due to an increase in solar activity. The VTEC showed a high variability during both winter and the equinoxes, with the highest value being 90%, but showed a low variability in summer. Two abnormal peaks appeared at sunrise and sunset in winter and the equinoxes. These peaks were the result of steep density gradients caused by the onset and turnoff of solar radiation. The correlation analysis yielded almost no correlation between the VTEC and geomagnetic activity but showed a high correlation with solar activity for all the seasons, particularly at night-time.


      PubDate: 2016-05-04T20:27:09Z
       
  • Temperature distribution and evolution characteristic in lightning return
           stroke channel
    • Abstract: Publication date: July 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 145
      Author(s): Yali Mu, Ping Yuan, Xuejuan Wang, Caixia Dong
      According to the time-resolved spectra of four lightning return strokes, the temperatures of arc core channel and the peripheral optical channel surrounding the arc core are investigated by different methods; the temperature distribution along the radial direction of channel on the peak current stage is discussed. The results show that a temperature gradient is formed along the radial direction of channel during the discharge process. With the increasing of the radius, the temperature decreases gradually. The temperature of arc core channel is about 4000–5000K higher than that of the peripheral optical channel. The time evolution of channel temperature shows that the falling of the temperature is very slow compared with the decreasing of the current after their peak values. After the peak current, the channel temperature is still maintained at around 20,000K up to 200–400 μ s . The heat effect resulting from such a long-time high temperature is the main source of most direct lightning disasters.


      PubDate: 2016-05-04T20:27:09Z
       
  • Large-scale traveling ionospheric disturbances using ionospheric imaging
           at storm time: A case study on 17 march 2013
    • Abstract: Publication date: July 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 145
      Author(s): Jun Tang, Yibin Yao, Jian Kong, Liang Zhang
      A moderate geomagnetic storm occurred on March 17, 2013, during which large-scale traveling ionospheric disturbances (LSTIDs) are observed over China by ionosondes and GPS from Crustal Movement Observation Network of China (CMONOC) and the International GNSS Service (IGS). Ionosonde data and computerized ionospheric tomography (CIT) technique are employed to analyze the disturbances in our study. The maximum entropy cross spectral analysis (MECSA) method is used to obtain the propagation parameters of the LSTIDs. Spatio-temporal variations of ionospheric electron density (IED) and total electron content (TEC) during this geomagnetic storm over China are investigated. Disturbance images of IED and TEC are also presented in the paper. The results show two LSTID events at about 12:00UT and 15:00UT during the main phase of the storm. Besides, the LSTIDs with a duration of 40min are detected over China. It is confirmed that the LSTIDs travel from north to south with a horizontal velocity of 400–500m/s, and moved southwestwards with a horizontal velocity of 250–300m/s, respectively.


      PubDate: 2016-05-04T20:27:09Z
       
  • 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 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
 
 
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