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  Subjects -> METEOROLOGY (Total: 83 journals)
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 4)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 9)
Advances in Climate Change Research     Open Access  
Advances in Meteorology     Open Access   (Followers: 7)
Aeolian Research     Hybrid Journal   (Followers: 3)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 7)
American Journal of Climate Change     Open Access   (Followers: 7)
Asian Journal of Earth Sciences     Open Access   (Followers: 21)
Atmósfera     Open Access  
Atmosphere     Open Access   (Followers: 4)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 7)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 14)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 8)
Atmospheric Research     Hybrid Journal   (Followers: 21)
Atmospheric Science Letters     Hybrid Journal   (Followers: 9)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 10)
Bulletin of the American Meteorological Society     Open Access   (Followers: 16)
Carbon Balance and Management     Open Access   (Followers: 5)
Change and Adaptation in Socio-Ecological Systems     Open Access   (Followers: 1)
Climate     Open Access   (Followers: 2)
Climate Change Economics     Hybrid Journal   (Followers: 16)
Climate Change Responses     Open Access  
Climate Dynamics     Hybrid Journal   (Followers: 15)
Climate law     Hybrid Journal   (Followers: 3)
Climate of the Past (CP)     Open Access   (Followers: 4)
Climate of the Past Discussions (CPD)     Open Access   (Followers: 2)
Climate Policy     Hybrid Journal   (Followers: 21)
Climate Risk Management     Open Access  
Climate Summary of South Africa     Full-text available via subscription  
Climatic Change     Hybrid Journal   (Followers: 32)
Current Climate Change Reports     Hybrid Journal  
Developments in Atmospheric Science     Full-text available via subscription   (Followers: 5)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 3)
Earth Perspectives - Transdisciplinarity Enabled     Open Access   (Followers: 1)
Energy & Environment     Full-text available via subscription   (Followers: 18)
Environmental and Climate Technologies     Open Access   (Followers: 2)
Global Meteorology     Open Access  
International Journal of Atmospheric Sciences     Open Access   (Followers: 4)
International Journal of Biometeorology     Hybrid Journal   (Followers: 1)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (Followers: 9)
International Journal of Climatology     Hybrid Journal   (Followers: 15)
International Journal of Image and Data Fusion     Hybrid Journal   (Followers: 1)
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (Followers: 9)
Journal of Atmospheric and Oceanic Technology     Full-text available via subscription   (Followers: 10)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 15)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 2)
Journal of Climate     Full-text available via subscription   (Followers: 29)
Journal of Climatology     Open Access   (Followers: 1)
Journal of Hydrology and Meteorology     Open Access   (Followers: 4)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 4)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Journal of Meteorology and Climate Science     Full-text available via subscription   (Followers: 1)
Journal of Space Weather and Space Climate     Open Access   (Followers: 4)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 28)
Journal of Weather Modification     Full-text available via subscription  
Large Marine Ecosystems     Full-text available via subscription  
Meteorologica     Open Access  
Meteorological Applications     Hybrid Journal   (Followers: 1)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 2)
Meteorology and Atmospheric Physics     Hybrid Journal   (Followers: 5)
Mètode Science Studies Journal : Annual Review     Open Access  
Michigan Journal of Sustainability     Open Access  
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 2)
Monthly Notices of the Royal Astronomical Society Letters     Hybrid Journal   (Followers: 3)
Monthly Weather Review     Full-text available via subscription   (Followers: 13)
Nature Climate Change     Full-text available via subscription   (Followers: 42)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 17)
Open Journal of Modern Hydrology     Open Access   (Followers: 3)
Revista Brasileira de Meteorologia     Open Access   (Followers: 1)
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 5)
Space Weather     Full-text available via subscription   (Followers: 3)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 2)
Tellus A     Open Access   (Followers: 5)
Tellus B     Open Access   (Followers: 7)
The Cryosphere (TC)     Open Access   (Followers: 2)
The Cryosphere Discussions (TCD)     Open Access   (Followers: 1)
The Quarterly Journal of the Royal Meteorological Society     Hybrid Journal   (Followers: 8)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 4)
Weather     Hybrid Journal   (Followers: 3)
Weather and Climate Extremes     Open Access   (Followers: 2)
Weather and Forecasting     Full-text available via subscription   (Followers: 3)
Weatherwise     Hybrid Journal  
气候与环境研究     Full-text available via subscription   (Followers: 1)
Journal Cover   Journal of Atmospheric and Solar-Terrestrial Physics
  [SJR: 1.045]   [H-I: 61]   [15 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [2798 journals]
  • IFC-Ed. board
    • Abstract: Publication date: October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 133

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

      PubDate: 2015-09-27T06:24:14Z
  • Formation of sporadic-E (Es) layers under the influence of AGWs evolving
           in a Horizontal shear flow
    • Abstract: Publication date: Available online 26 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): G.G. Didebulidze, G. Dalakishvili, L. Lomidze, G. Matiashvili
      The formation of mid-latitude sporadic-E (Es) layer under the influence of atmospheric gravity waves (AGWs), evolving in the background horizontal wind with a horizontal linear shear (horizontal shear flow), is studied. The AGWs, which are in-situ excited in the horizontal shear flow, interact with metallic ions through ion-neutral collisions and Lorentz forcing, influence the horizontal and vertical motion of ions, and lead to their convergence into thin horizontal layers. In order to investigate the formation of sporadic-E, 2-D numerical simulations are performed and temporal evolution of multilayered sporadic-E is demonstrated. It is found that ion/electron density of Es layer depends on the value of the horizontal shear of a magnetic north-directed background wind. The increase of the shear parameter in the cyclonic type background wind leads to the increase of horizontal convergence of charged particles. It is shown that the plasma density of Es layers also depends on the horizontal and vertical amplitudes of AGWs’ velocity perturbations, which increase in the horizontal shear flow and cause a formation of multilayered sporadic-E. The Es layers mainly move downwards, but at certain spatial location, where temporal changes in wave phase caused by background shear flow and AGW are small, these layers are almost horizontal. The vertical spatial location of the horizontal Es layers is determined by the vertical wavelength of atmospheric gravity waves.

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

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

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

      PubDate: 2015-09-27T06:24:14Z
  • A return stroke model based purely on the current dissipation concept
    • Abstract: Publication date: Available online 24 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Vernon Cooray
      A return stroke model based purely on the current dissipation concept is introduced. With three model parameters the model is capable of generating electric and magnetic fields that are in reasonable agreement with experimentally observed electromagnetic fields.

      PubDate: 2015-09-27T06:24:14Z
  • On the mimimum length of leader channel and the minimum volume of space
           charge concentration necessary to initiate lightning flashes in
    • Abstract: Publication date: Available online 24 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Vernon Cooray
      Minimum length to which a leader channel has to grow before it can propagate continuously as a stable leader as a function of the background electric field inside a thundercloud is estimated. For electric field magnitudes comparable to the values measured inside thunderclouds, the minimum length of the leader channel that is required for it to propagate continuously is about 3–5m. In other words, a leader discharge that originated inside a thundercloud has to grow to a length of 3–5m before it can culminate in a stable and continuously propagating leader discharge that can give rise to a lightning flash. The minimum size of charge concentrations that can make this event possible have radii in the range of 2–4m and should carry about 300–900μC of electric charge, respectively. This in turn shows that the high field regions inside the cloud where electrical discharges that can culminate in stable leader discharges, and hence in lightning discharges, may be confined to volumes which are no larger than a few meters in radius.

      PubDate: 2015-09-27T06:24:14Z
  • A study of changes in apparent ionospheric reflection height within
           individual lightning flashes
    • Abstract: Publication date: Available online 25 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Vijaya B. Somu, Vladimir A. Rakov, Michael A. Haddad, Steven A. Cummer
      Ionospheric reflection heights estimated using the zero-to-zero and peak-to-peak methods to measure skywave delay relative to the ground wave were compared for 108 first and 124 subsequent strokes at distances greater than 100km. For either metric there was a considerable decrease in average reflection height for subsequent strokes relative to first strokes. We showed that the observed difference cannot be explained by the difference in frequency content of first and subsequent return-stroke currents. Apparent changes in reflection height (estimated using the peak-to-peak method) within individual flashes for 54 daytime and 11 nighttime events at distances ranging from 50km to 330km were compared, and significant differences were found. For daytime conditions, the majority of the flashes showed either decrease (57%) or non-monotonic variation (39%) in reflection height with respect to the immediately preceding stroke. With respect to the first stroke, 91% of the flashes showed monotonic decrease in height. For nighttime flashes, patterns in reflection height changes with respect to the immediately preceding stroke were as follows: 46% no change, 27% monotonic decrease, and 27% non-monotonic variation. When changes were measured with respect to the first stroke, 54% of nighttime flashes showed monotonic decrease and 46% no change. Ionospheric reflection height tends to increase with return-stroke peak current. The observed daytime effects can be explained by (a) the dependence of EMP penetration depth on source intensity, which decreases with stroke order, (b) additional ionization associated with elves, or (c) combination of (a) and (b) above.

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

      PubDate: 2015-09-23T05:56:22Z
  • Tropospheric temperature climatology and trends observed over the Middle
    • Abstract: Publication date: October 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 133
      Author(s): Ghouse Basha, P.R. Marpu, T.B.M.J. Ouarda
      In this study, we report for the first time, the upper air temperature climatology, and trends over the Middle East, which seem to be significantly affected by the changes associated with hot summer and low precipitation. Long term (1985–2012) radiosonde data from 12 stations are used to derive the mean temperature climatology and vertical trends. The study was performed by analyzing the data at different latitudes. The vertical profiles of air temperature show distinct behavior in terms of vertical and seasonal variability at different latitudes. The seasonal cycle of temperature at the 100hPa, however, shows an opposite pattern compared to the 200hPa levels. The temperature at 100hPa shows a maximum during winter and minimum in summer. Spectral analysis shows that the annual cycle is dominant in comparison with the semiannual cycle. The time-series of temperature data was analyzed using the Bayesian change point analysis and cumulative sum method to investigate the changes in temperature trends. Temperature shows a clear change point during the year 1999 at all stations. Further, Modified Mann–Kendall test was applied to study the vertical trend, and analysis shows statistically significant lower tropospheric warming and cooling in upper troposphere after the year 1999. In general, the magnitude of the trend decreases with altitude in the troposphere. In all the latitude bands in lower troposphere, significant warming is observed, whereas at higher altitudes cooling is noticed based on 28 years temperature observations over the Middle East.

      PubDate: 2015-09-19T05:25:05Z
  • Analysis of air mass trajectories in the northern plateau of the Iberian
    • Abstract: Publication date: Available online 12 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Isidro A. Pérez, M. Luisa Sánchez, M. Ángeles García, Nuria Pardo
      Air masses reaching the Iberian Peninsula, which is located between two continents and two seas, have been classified. 24-h backward air trajectories were calculated each hour for three years using the METEX model at a site in the centre of the northern plateau of the Iberian Peninsula where the air flow has scarcely been investigated to date. Rather than the usual Euclidean geometry, spherical trigonometry, together with the kernel regression method, was considered to calculate trajectory distances to the site. Numerical indicators allow for an accurate description of the results. Ranges surrounding the site from E to S evidenced a restriction in the movement of the arriving flow. However, the range to the N showed only a slight effect. A noticeable seasonal contrast was observed between winter, whose distances were the greatest, and summer, which displayed the shortest distances. Trajectory clusters, initially not considered in the METEX model, were obtained with different metrics to determine the air mass pathways reaching the site. Five clusters of trajectories were selected so as to easily explain the directions and distances covered. Regional and long range transport were observed in clusters from the NE, NW and SW. The NE cluster presented an orographic deviation and local processes were limited to the SE cluster. Finally, seasonal analysis revealed singular behaviour during autumn, when local processes centred on the N-S direction.

      PubDate: 2015-09-15T05:15:36Z
  • Improvement of automatic scaling of vertical incidence ionograms by
           simulated annealing
    • Abstract: Publication date: Available online 7 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Chunhua Jiang, Guobin Yang, Ting Lan, Peng Zhu, Huan Song, Chen Zhou, Xiao Cui, Zhengyu Zhao, Yuannong Zhang
      The ionogram autoscaling technique is very important for facilitating the statistical investigation of the ionosphere. Jiang et al. (2013) proposed an autoscaling technique for extracting ionospheric characteristics from vertical incidence ionograms. However, extensive efforts are invested in continuously improving the performance of that. The Simulated Annealing (SA) is used to improve the autoscaling technique in this paper. To be capable of automatic scaling of ionograms recorded at different locations, the SA is applied instead of Empirical Orthogonal Functions (EOFs) to search the best-fit parameters in the autoscaling technique. In order to validate the improvement of this autoscaling technique, ionograms recorded at Wuhan (30.5°N, 114.3°E), Puer (22.7°N, 101.05°E) and Leshan (29.6°N, 103.75°E) are investigated by comparing the autoscaled results with the values scaled by an operator. Results show that the presented work is efficient for scaling of ionograms recorded at different geographic positions. Moreover, the additional procedure can improve the accuracy of the autoscaling technique compared to results presented by Jiang et al. (2013).

      PubDate: 2015-09-11T14:11:34Z
  • Shape and oscillations of the water drops freely suspended in a Horizontal
           electric field: A wind tunnel study
    • Abstract: Publication date: Available online 8 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Rohini Bhalwankar, C.G. Deshpande, A K Kamra
      The time-averaged axis ratios, frequency and amplitude of oscillations of water drops of 2.67 to 6.6mm diameter were determined by suspending them in a vertical wind tunnel in the absence and presence of horizontal electric fields using a high speed camera at 1000 frames per second. A systematic decrease in the drop's axis-ratio is observed with increase in its diameter and/or horizontal electric field. The results revealed with high speed photography are in good agreement with earlier results. The drop distortion due to horizontal electric field is more pronounced for the drops in the size-range of 3.36 to 6mm diameter showing that the electrical forces progressively enhance the horizontal elongation of the drop resulting in its instability at 6.6mm. The drop oscillation frequency computed from temporal variation of axis ratio, decreases with increase in drop size but shows no significant change in oscillation frequency in the horizontal electric field of≤500kVm−1. However, the oscillation amplitude increases with increase in drop size up to a threshold value and then flatten-off in the electric field of≤300kVm−1 demonstrating the nonlinear effect of net forces acting on such large drops. In higher electric field of 500kVm-1, gradual increase in the amplitude of oscillation with an increase in drop diameter has been observed. Moreover, for a particular drop size, the amplitude of oscillation decreases with increase in the electric field up to 500kVm−1. The oscillation frequency of the waterdrops experiences multimode oscillations. The dominant fundamental mode of oscillations (2,0) always exists for all drops in our experiments along with the coexistence of higher modes of oscillations i.e. (2,1) and (2,2) mode. Possible effects of electrical forces on shape parameters and their implications on cloud microphysics and in radar meteorology are discussed.

      PubDate: 2015-09-11T14:11:34Z
  • The august 2011 URSI world Day campaign: Initial results
    • Abstract: Publication date: Available online 9 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Thomas J. Immel, Guiping Liu, Scott L. England, Larisa P. Goncharenko, Philip J. Erickson, Mykhaylo V. Lyashenko, Marco Milla, Jorge Chau, Harald U. Frey, Stephen B. Mende, Qihou Zhou, Anja Stromme, Larry J. Paxton
      During a 10-day URSI World Day observational campaign beginning on August 1, 2011, an isolated, major geomagnetic storm occurred. On August 5, Kp reached values of 8- and Dst dropped to -113nT. The occurrence of this isolated storm in the middle of a 10-day URSI World Day campaign provides and unprecedented opportunity to observe the coupling of solar wind energy into the magnetosphere and to evaluate the varied effects that occur in the coupled magnetosphere-ionosphere-thermosphere system. Dramatic changes in the ionosphere are seen at every one of the active radar stations, extending from Greenland down to equatorial Peru in the American sector and at middle latitudes in Ukraine. Data from TIMED and THEMIS are shown to support initial interpretations of the observations, where we focus on processes in the middle latitude afternoon sector during main phase, and the formation of a dense equatorial ionosphere during storm recovery. The combined measurements strongly suggest that the changes in ionospheric conditions observed after the main storm phase can be attributed in large part to changes in the stormtime thermosphere. This is through the generation of disturbance dynamo winds and also global neutral composition changes that either reduce or enhance plasma densities in a manner that depends mainly upon latitude. Unlike larger storms with possibly more sustained forcing, this storm exhibits minimal effects of persistent meridional stormtime wind drag, and little penetration of solar wind electric potentials to low latitudes. It is, therefore, an outstanding example of an impulsive event that exhibits longer-term effects through modification of the background atmosphere.

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

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

      PubDate: 2015-09-11T14:11:34Z
  • Interannual and intraseasonal variability of stratospheric dynamics and
           stratosphere-troposphere coupling during northern winter
    • Abstract: Publication date: Available online 10 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.I. Pogoreltsev, E.N. Savenkova, O.G. Aniskina, T.S. Ermakova, W. Chen, K. Wei
      The UK Met Office reanalysis data have been used to investigate the interannual and intraseasonal variability of the stratospheric dynamics and thermal structure. The results obtained show that the maximum of interannual variability of the mean zonal flow associated with the quasi-biennial oscillation (QBO) is observed at the altitude of about 30km. It is shown that there is a statistically significant influence of the QBO phase on the extratropical stratosphere, the so-called, Holton-Tan effect. The results of data analysis show that the conditions under the easterly QBO phase are more favorable for the development of the sudden stratospheric warmings (SSW). The statistical analysis of 15 major SSW observed during two last decades has been performed. The obtained results demonstrate that in recent years internal processes associated with nonlinear interactions of stationary planetary waves (SPW) with the mean flow played a dominant role. It is shown that the first enhancement of the SPW1 in the upper stratosphere takes place because of an amplification of nonlinear interactions between this wave and the mean flow. This enhancement is accompanied by a subsequent increase in the wave activity flux from the stratosphere into the troposphere with further redistribution of wave activity in the horizontal plane. Then, an increase of the upward flux from the troposphere into the stratosphere in another region occurs. The secondary enhancement of the planetary wave activity in the stratosphere is accompanied by the heating of the polar region and the weakening, or even reversal of the stratospheric jet. Additionally to the well-known result that meridional refraction of SPW to the polar region in stratosphere is one of the preconditions of development SSW, the nonlinear wave-wave and wave-mean flow interactions can play an important role before and during SSW. It is shown that the upper stratosphere can be considered as the region where SPW2 is generated during SSW.

      PubDate: 2015-09-11T14:11:34Z
  • An interpretation of spacecraft and ground based Observations of multiple
           omega band Events
    • Abstract: Publication date: Available online 3 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): J.M. Weygand, M.G. Kivelson, H.U. Frey, J.V. Rodriguez, V. Angelopoulos, R. Redmon, J. Barker-Ream, A. Grocott, O. Amm
      The source of the auroral phenomenon known as omega bands is not yet known. We examine in detail five different intervals when omega bands were observed on March 9th, 2008 between 0400UT and 1100UT over central Canada using both ground and space-based instrumentation. The THEMIS all sky imagers show the development of some of the omega bands from north-south streamers. Spherical elementary currents derived from ground magnetometer data indicate that the omega bands lie near the interface between the region 1and region 2 currents in the post midnight sector. THEMIS spacecraft data from the pre-midnight sector display multiple high speed flows and dipolarization features associated with high levels of geomagnetic activity, whereas four GOES geosynchronous spacecraft show multiple injections and dipolarization features. Magnetic field line tracing suggests that the magnetospheric location of the omega bands is at or just beyond geosynchronous orbit. We discuss in detail two potential source mechanisms for the omega bands: plasma sheet velocity shears and high speed flows in the magnetotail and relate the available data to those mechanisms. Our data and a magnetohydrodynamic (MHD) simulation support high speed flows in the magnetotail as the most likely generation mechanism, although the distribution of the magnetotail spacecraft does not provide unambiguous support for our interpretation of the source mechanism.

      PubDate: 2015-09-06T14:07:09Z
  • Variations in meteor heights at 22.7°S during solar cycle 23
    • Abstract: Publication date: Available online 1 September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): L.M. Lima, L.R. Araújo, E.O. Alves, P.P. Batista, B.R. Clemesha
      The meteor radar measurements obtained at Cachoeira Paulista (22.7°S), Brazil, have been used to study a possible relationship between meteor echo height variations and solar flux during solar cycle 23. A good concordance between the normalized values of the annual mean of the meteor peak heights and F 10.7 solar radio flux and Mg_II solar indexes have been observed during declining phase of the solar cycle 23. After eliminating the solar activity influence, the annual mean of the meteor echo peak heights showed a linear decrease of 30m/year when Mg_II solar index is used and 38m/year when F 10.7 solar radio flux is used. When the trend is eliminated the relationship between meteor peak heights and F 10.7 solar flux indicate a trend of 672m/100sfu (sfu-solar flux unit). The meteor amplitude signals and the decay time drops after mid-2004, which may be attributed to the decreasing of the electron density in the meteor trails. The meteor echo peak height decrease has been interpreted as being caused by a reduction in air density in the upper atmosphere.

      PubDate: 2015-09-01T13:26:29Z
  • The lunar tides in the mesosphere and lower thermosphere over Brazilian
    • Abstract: Publication date: Available online 29 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.R. Paulino, P.P. Batista, L.M. Lima, B.R. Clemesha, R.A. Buriti, N. Schuch
      Meteor radar observations at São João do Cariri (7.4°S; 36.5°W), Cachoeira Paulista (22.7°S; 45°W) and Santa Maria (29.7°S; 53.7°W) have permitted estimates to be made of winds in the mesosphere and lower thermosphere (MLT) over the Brazilian sector simultaneously. Using horizontal winds the semidiurnal lunar tide is determined from January 2005 to December 2008 for these three sites. The lunar tide is observed to reach amplitudes as large as 8m/s. In general, the amplitude increases with height and the phase decreases with height, corresponding to an upwardly-propagating tide. The estimated vertical wavelengths are variable for some month, like December at Cachoeira Paulista for northward wind, April and June at Santa Maria for eastward wind, which indicates possible mode coupling and reflection. Characteristics similar to those seen in the Northern Hemisphere have been observed in June and October at São João do Cariri, in December at Cachoeira Paulista, in March at Santa Maria and in August at all observation sites, which suggest the presence of antisymmetric modes. Different behaviour has been observed in the amplitudes, phases and vertical wavelengths at each station, indicating latitudinal variation even from the low to the equatorial region.

      PubDate: 2015-09-01T13:26:29Z
  • Forecasting geomagnetic activity at monthly and annual horizonsTime series
    • Abstract: Publication date: Available online 24 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Gordon Reikard
      Most of the existing work on forecasting geomagnetic activity has been over short intervals, on the order of hours or days. However, it is also of interest to predict over longer horizons, ranging from months to years. Forecasting tests are run for the Aa index, which begins in 1868 and provides the longest continuous records of geomagnetic activity. This series is challenging to forecast. While it exhibits cycles at 11–22 years, the amplitude and period of the cycles varies over time. There is also evidence of discontinuous trending: the slope and direction of the trend change repeatedly. Further, at the monthly resolution, the data exhibits nonlinear variability, with intermittent large outliers. Several types of models are tested: regressions, neural networks, a frequency domain algorithm, and combined models. Forecasting tests are run at horizons of 1–11 years using the annual data, and 1–12 months using the monthly data. At the 1-year horizon, the mean errors are in the range of 13–17 percent while the median errors are in the range of 10–14 percent. The accuracy of the models deteriorates at longer horizons. At 5 years, the mean errors lie in the range of 21–23 percent, and at 11 years, 23–25 percent. At the 1 year horizon, the most accurate forecast is achieved by a combined model, but over longer horizons (2–11 years), the neural net dominates. At the monthly resolution, the mean errors are in the range of 17–19 percent at 1 month, while the median errors lie in a range of 14–17 percent. The mean error increases to 23–24 percent at 5 months, and 25 percent at 12 months. A model combining frequency and time domain methods is marginally better than regressions and neural networks alone, up to 11 months. The main conclusion is that geomagnetic activity can only be predicted to within a limited threshold of accuracy, over a given range of horizons. This is consistent with the finding of irregular trends and cycles in the annual data, and nonlinear variability in the monthly series.

      PubDate: 2015-08-28T13:04:05Z
  • A model for absorption of solar radiation by mineral dust within liquid
           cloud drops
    • Abstract: Publication date: Available online 28 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Qing Zhang, Jonathan E. Thompson
      Models of light scattering and absorption that consider the effect of insoluble inclusions present within liquid cloud droplets may assume the inclusion occupies random locations within the droplet. In certain cases, external forces can lead to certain orientations or alignments that are strongly preferred. Within this modeling study, we consider one such case in which an insoluble mineral dust inclusion (ρ=2.6g / cm3) is placed within a liquid water drop (ρ=1.0g /cm3). Such an instance mimics mineral dust aerosols being incorporated within cloud drops in Earth's atmosphere. Model results suggest super-micron mineral dust settles to the bottom of cloud droplets. However, Brownian motion largely randomizes the position of sub-micron mineral dust within the droplet. The inherent organization of the particles that result has important consequences for light absorption by mineral dust when present within a cloud drop. Modeled results suggest light absorption efficiency may be enhanced by as much as 4–6 fold for an isolated droplet experiencing direct solar illumination at solar zenith angles of <20deg. For such an isolated droplet, the absorption efficiency enhancement falls rapidly with increasing solar zenith angle indicating a strong angle of incidence dependence. We also consider the more common case of droplets that contain dust inclusions deep within optically dense clouds. Absorption efficiency enhancements for these locales follow a dramatically different pattern compared to the optically isolated droplet due to the presence of diffuse rather than direct solar irradiation. In such cases, light absorption efficiency is decreased through including super-micron dust within water droplets. The study has important implications for modeling the absorption of sunlight by mineral dust aerosol within liquid water clouds. The angle of incidence dependence also reveals that experimental measurement of light absorption for cases in which particle alignment occurs may not always accurately reflect atmospheric absorption of sunlight. Therefore, care must be taken to extrapolate measurement data to climate models.

      PubDate: 2015-08-28T13:04:05Z
  • Three-dimensional imaging of the plasma parameters of a moving cusp aurora
    • Abstract: Publication date: Available online 28 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Satoshi Taguchi, Keisuke Hosokawa, Yasunobu Ogawa
      During a period of negative IMF B Z on 13 January 2013, an all-sky imager at Longyearbyen, Svalbard observed a mesoscale aurora moving towards the east-northeast in the cusp, passing through the field of view of the EISCAT Svalbard Radar (ESR) elevation scan. The elevation scans that were being performed at that time have a horizontal coverage of approximately 300km, at an altitude of 300km. The plasma data obtained from the elevation scans and the 630-nm aurora emission data from the all-sky imager have shown that ion temperature enhanced 50–60s earlier than electron density, and that the maximum auroral intensity in the ESR's field of view occurred about 40s after the electron density enhancement. On the basis of these results we have constructed three-dimensional images of elevated ion temperatures and enhanced electron density associated with the mesoscale moving cusp aurora. The three-dimensional image shows that the enhancement of the ion temperature is prominent in the horizontal area of ~160km×~80km below an altitude of ~300km, and that this volume forms on the forward side of the enhanced electron density region. We interpret these configurations as being a result of a mesoscale twin-cell convection, which is embedded in the background flow such that the symmetrical axis of the twin-cell is inclined from the background flow direction by several tens of degrees. Our method for visualizing three-dimensional features such as these could be an effective approach to understanding the mesoscale dynamics of the cusp, which is usually located in latitudes that are difficult for the currently-operated radars that permit three-dimensional, simultaneous measurements to investigate.

      PubDate: 2015-08-28T13:04:05Z
  • Temporal and structural evolution of a tropical monsoon cloud system: A
           case study using X-band radar observations
    • Abstract: Publication date: Available online 22 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Subrata Kumar Das, Sachin M. Deshpande, Siddarth Shankar Das, Mahen Konwar, Kaustav Chakravarty, Madhu Chandra Reddy Kalapureddy
      A mobile X-band (~9.535GHz) dual-polarization Doppler weather radar system was operated at a tropical site Pune (18.5386°N, 73.8089°E, 582m AMSL) by the Indian Institute of Tropical Meteorology, Pune, India for observing monsoon clouds. The measurement site was on the leeward (eastern) side of the Western Ghats (WG). This study focuses on the horizontal and vertical structure of monsoon precipitating clouds and its temporal evolution as observed by the X-band radar on August 27, 2011. The radar reflectivity factor (Z, dBZ) is used as a proxy for measure of intensity of cloud system. Result shows that the radar reflectivity has a strong temporal variation in the vertical, with a local peak occurring in the afternoon hours. Relatively shallow structure during the late night and early morning hours is noticed. The observed cloud tops were reached up to 8km heights with reflectivity maxima of about 35 dBZ at ∼5km. The spatial and vertical evolution of radar reflectivity is consistent with the large-scale monsoon circulation. The variations in the outgoing longwave radiation (OLR) from the Kalpana-1 satellite and vertical velocity and cloud-mixing ratio from the MERRA reanalysis data are also analyzed. As direct observations of clouds using radars are sparse over the Indian region, the results presented here would be useful to understand the processes related to cloud and precipitation formation in the tropical environment.

      PubDate: 2015-08-24T04:41:46Z
  • Study of fog in Bulgaria by using the GNSS tropospheric products and large
           scale dynamic analysis
    • Abstract: Publication date: Available online 20 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A. Stoycheva, G. Guerova
      The fog formation, development, and dissipation are studied by employing the synergy between surface observations and vertically Integrated Water Vapor (IWV) from Global Navigation Satellite Systems (GNSS). Selected are three fog cases in February and November 2012 and the fog development in 4 locations in north Bulgaria is analysed. It is found that the IWV tends to decrease during fog formation, and densification. Increase of IWV leads to fog dispersion and can be a result of evaporation or advection of new humid air mass. The mixing ratio also decreases during the fog formation and increases during dissipation but has a distinct diurnal variability, which limits its short range forecasting potential. IWV is found to have a very high sensitivity to both air mass transformation and/or advection at altitude. In one case it is found that the arrival time of a new air mass at altitude is of key importance for further fog development or suppression. The change of the air mass leads to change of the diurnal cycle of surface parameters like temperature thus controlling the fog life cycle. Further complication of fog diagnosis is introduced by a dynamic component, reflecting the orography difference in west and east part of Bulgaria. The behaviour of the IWV and mixing ratio can be a valuable additional tool in decision making processes for very short range fog diagnosis and prognosis. For monitoring fog life cycle hourly or sub-hourly data-sets will be an advantage.

      PubDate: 2015-08-20T04:25:02Z
  • Origin of high-frequency TEC disturbances observed by GPS over the
           European mid-latitude region
    • Abstract: Publication date: Available online 12 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Gilles Wautelet, Rene Warnant
      High-frequency variability of the ionospheric Total Electron Content (TEC) can strongly affect precise positioning with GNSS. The occurrence rate as well as the amplitude of such disturbances have been extensively studied over the last decade. Mainly, one can distinguish disturbances due to space-weather events and the others, qualified as “quiet-time” as they are observed during quiet geomagnetic conditions. The latter, which represent more than 75% of the total number of disturbances over mid-latitudes, are then divided into two categories: the Winter Daytime (WD) and the Summer Nighttime (SN). The first category, representing the bulk of quiet-time disturbances, corresponds to classical Medium-Scale Traveling Ionospheric Disturbances (MSTIDs), that are the result of the interaction of gravity waves and the ionospheric plasma. On the other hand, SN disturbances are generally understood as non-classical MSTIDs of electrical origin. The paper investigates the origin of these two types of disturbance based on GPS measurements, ionospheric soundings and wind speed data at tropospheric level. If one cannot exclude the solar terminator as a potential source of gravity waves responsible for WD events, it is thought that the major contribution comes from the lower atmosphere. More precisely, tropospheric jetstream is considered as the favorite candidate for daytime MSTIDs. Turning to SN disturbances, our analysis reveals that they are related to spread-F phenomenon, linked to the appearance of sporadic E-layers. The related instabilities are responsible for field-aligned irregularities in the F-region, which are thought to be responsible for noise-like fluctuations of the GPS TEC observed during SN events.

      PubDate: 2015-08-16T04:21:25Z
  • Lightning-induced voltages caused by lighting strike to tall Objects
           considering the effect of frequency dependent soil
    • Abstract: Publication date: Available online 14 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Qilin Zhang, Yuan Chen, Wenhao Hou
      In this paper we have analyzed the effect of frequency dependent soil (FDS) on the lightning-induced voltages caused by lightning subsequent return stroke for strike to tall objects ranging from 100m to 300m. It is found that the effect of FDS on the induced voltages peak can be approximately ignored when the low frequency conductivity (LFC) is equal to or larger than 0.01S/m, and with the decrease of LFC, the effect of FDS on the lightning induced voltages is more obvious. Compared with the constant LFC, the induced voltage peak becomes less for FDS. For example, for a constant LFC of 0.001S/m, the ratio of the induced voltages peak value for FDS to that for LFC is 83.2% at the line center and 66.8% at the line end for strike to 300-m-tall object, respectively. By using the decomposition method, we divide the lightning induced voltages into two components named by the incident induced waves (Vi) related with the vertical field and scattered induced waves (Vs) related with horizontal field, and it is found that FDS results into a less initial peak of tangential horizontal field along the overhead line and further results into a less induced voltage. Also, compared FDS with LFC, the FDS reduces the disparity of lightning induced voltages caused by different tall objects. For example, for the constant LFC, the induced voltage peak for strike to 300-m-tall object is 1.69 times larger than that for strike to 50-m-tall object. However, for the case of FDS, the corresponding ratio is about 1.2.

      PubDate: 2015-08-16T04:21:25Z
  • Wave like signatures in aerosol optical depth and associated radiative
           impacts over the central Himalayan region
    • Abstract: Publication date: Available online 3 August 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): K.K. Shukla, D.V. Phanikumar, K. Niranjan Kumar, Kishore Reddy, V.R. Kotamarthi, Rob K Newsom, Taha B.M.J Ouarda
      Doppler Lidar and Multi Filter Rotating Shadow band Radiometer (MFRSR) observations are utilized to show wave like signatures in aerosol optical depth (AOD) during daytime boundary layer evolution over the Himalayan region. Fourier analysis depicted 60-80min periods dominant during afternoon hours, implying that observed modulations could be plausible reason for the AOD forenoon-afternoon asymmetry which was previously reported. Inclusion of wave amplitude in diurnal variation of aerosol radiative forcing estimates showed ~40% additional warming in the atmosphere relative to mean AOD. The present observations emphasize the importance of wave induced variations in AOD and radiation budget over the site.

      PubDate: 2015-08-07T03:24:44Z
  • IFC-Ed. board
    • Abstract: Publication date: September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 132

      PubDate: 2015-08-03T03:21:35Z
    • Abstract: Publication date: Available online 31 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Marni Pazos, Blanca Mendoza, Luis Gimeno
      Three tropical cyclogenesis precursors, (absolute vorticity, relative humidity, vertical shear)and, the combined Genesis Potential Index are investigated in order to analyse their behaviour during three different phases(descending, minimum and ascending) of the solar cycle. The correlation between these tropical cyclogenesis precursors and the Dst geomagnetic index is also assessed, with the main finding being that the correlations between both the Genesis Potential Index and the vertical shear with the Dst index are statistically significant. This result suggests that the relationship between geomagnetic activity and tropical cyclones might be modulated by the influence of geomagnetic activity on the vertical wind shear.

      PubDate: 2015-08-03T03:21:35Z
  • Refinement of the background ionospheric conditions and plausible
           explanation based on neutral dynamics for the occurrence/non-occurrence of
           L-band scintillation patches against forecast.
    • Abstract: Publication date: Available online 26 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R. Sridharan, Lijo Jose, Mala S. Bagiya, Surendra Sunda, R.K. Chaudhary, Tarun K. Pant
      The recently evolved L–band scintillation forecast mechanism based on the characteristic features of the daytime F-region electron density fluctuations and also on the basic ionospheric conditions had been successful to a reasonable extent in forecasting the spatio-temporal map of scintillation patches. There had been a few non-compliances in the expected pattern within/outside the forecast windows. The present paper attempts to address such non-compliances and offers a plausible explanation based on neutral dynamics, especially the local time variation of vertical winds over the magnetic equator, while at the same time refining the earlier stipulated background ionospheric conditions. With the above refinements, it is anticipated that the forecast mechanism would become very robust. The present results highlight the importance of the neutral dynamical parameters and the urgent need to concentrate on the efforts to make systematic measurements of the same in order to characterize their variability.

      PubDate: 2015-07-29T21:00:18Z
  • On the variability of the diurnal tide and coupling with planetary waves
           in the MLT over Cachoeira Paulista (22.7°S, 45°W)
    • Abstract: Publication date: Available online 20 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A. Guharay, P.P. Batista, B.R. Clemesha
      Using meteor radar observations of four years in the mesosphere and lower thermosphere (MLT) over a subtropical Brazilian station, Cachoeira Paulista (22.7°S, 45°W), the temporal variability characteristics of the diurnal tide have been studied. In addition to the semiannual, annual and interannual variations, the diurnal tide amplitude exhibits clear intermittent modulation at periods of planetary waves. The tidal amplitude exhibits clear seasonal pattern with largest amplitude in fall equinox. The dominant periods of modulation of the diurnal tide are found to be greater than 10 days in the MLT. The diurnal tide, as detected in the power spectra of the horizontal winds, shows a spread in period around the central period (24h) which is an indication of nonlinear interactions between the diurnal tide and planetary waves. A bispectral analysis reveals prominent triplets (two primary waves and a secondary wave) confirming the interaction of the diurnal tide with planetary waves persistent over a broad spectral range. Also there is an indication of coupling of the diurnal tide with the intraseasonal oscillations at various times of the year.

      PubDate: 2015-07-21T22:05:34Z
  • Correlation between the sunspot number and tropospheric refractivity in a
           tropical environment
    • Abstract: Publication date: Available online 20 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Najib Yusuf, B.G. Ayantunji
      In this paper, a study of the tropospheric surface refractivity relationship with sunspots number variability on daily scale was carried out in a tropical region in Nigeria. The data was averaged to hourly mean from the initial five minutes update cycle and then to daily mean using spread sheet. The dependence of surface radio refractivity on sunspots number for the period considered in this work was established using linear regression coefficient and the results for Lagos and Anyigba are R2=0.019, R 2=0.004, R2=0.010, R 2=0.000 and R 2=0.000 for 2007, 2008, 2009, 2010 and 2011 and R 2=0.089, R 2=0.027 and R 2=0.007 for 2010, 2011 and 2012 respectively. However, when the spotless days were filtered the regression coefficient was obtained to be R 2=0.145, R 2=0.01261, R 2=0.00001, R 2=0.0012 and R 2=0.062 for 2007, 2008, 2009, 2010 and 2011 for Lagos and R 2=0.1155, R 2=0.0261 and R 2=0.0071 for 2010, 2011 and 2012 for Anyigba respectively. Meteorological data from 2007 to 2011 was employed for Lagos while meteorological data from 2010 to 2012 was employed for Anyigba. Sunspot data was also obtained from Royal Observatory of Belgium for the period under study. Results obtained show no correlation between Sunspot number and surface refractivity. The sunspot number data was filtered to remove noise due to spotless days. The result obtained after filtering did not show any significant difference.

      PubDate: 2015-07-21T22:05:34Z
  • “Characteristics of turbulence in the troposphere and lower
           stratosphere over the Indian Peninsula”
    • Abstract: Publication date: Available online 19 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): S.V. Sunilkumar, M. Muhsin, K. Parameswaran, M. Venkat Ratnam, Geetha Ramkumar, K. Rajeev, B.V. Krishna Murthy, K.V. Sambhu Namboodiri, K.V. Subrahmanyam, K. Kishore Kumar, Siddarth Sankar Das
      Characteristics of turbulence in the troposphere and lower stratosphere at Trivandrum (8.5°N, 76.9°E) and Gadanki (13.5°N, 79.2°E), two tropical stations located in the Indian Peninsula, are studied using GPS-radiosonde observations during the period of December 2010 to March 2014 as part of the Tropical Tropopause Dynamics (TTD) Experiment under the CAWSES-India program. This study relies on the detection of turbulence applying Thorpe analysis to the temperature profile, taking into account the impact of atmospheric moisture and instrumental noise on static stability. In general, the tropospheric turbulence is largely intermittent in space and time. The altitude region very close to the convective tropopause (COT), 10–15km, is relatively more turbulent than the lower troposphere from 3 to 8km. Though the occurrence of turbulence decreases significantly above the COT, occasionally a rather thin layer of turbulence (thickness <1km) is observed in the tropical tropopause layer (TTL) very close to the cold point tropopause (CPT). Even though broad turbulent layers, with thickness >2km, are the persisting features that can be observed in the 5–15km altitude region in multiple observations at both the sites at least during Asian Summer Monsoon (ASM) season, prominent multiple thin layers of stratified turbulence in the lower troposphere lasting for a day or less are observed only at Trivandrum in all seasons. In general, the turbulence strength in the 5–15km altitude region at Gadanki is generally larger than that at Trivandrum. Below 15km, while the turbulence is mainly governed by the convective instability at Gadanki, wind-shear driven (dynamic) instability also contributes considerably for the generation of turbulence at Trivandrum. While the generation of turbulence above 15km is dominated by dynamic instability, in the lower stratosphere (LS) it is mainly due to strong wind shears.

      PubDate: 2015-07-21T22:05:34Z
  • Extreme stratospheric springs and their consequences for the onset of
           polar mesospheric clouds
    • Abstract: Publication date: September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 132
      Author(s): David E. Siskind, Douglas R. Allen, Cora E. Randall, V. Lynn Harvey, Mark E. Hervig, Jerry Lumpe, Brentha Thurairajah, Scott M. Bailey, James M. Russell
      We use data from the Aeronomy of Ice in the Mesosphere (AIM) explorer and from the NASA Modern Era Retrospective Analysis for Research and Applications (MERRA) stratospheric analysis to explore the variability in the onset of the Northern Hemisphere (NH) Polar Mesospheric Cloud (PMC) season. Consistent with recently published results, we show that the early onset of the NH PMC season in 2013 was accompanied by a warm springtime stratosphere; conversely, we show that the late onset in 2008 coincides with a very cold springtime stratosphere. Similar stratospheric temperature anomalies for 1997 and 2011 also are connected either directly, through observed temperatures, or indirectly, through an early PMC onset, to conditions near the mesopause. These 4 years, 2008, 1997, 2011, and 2013 represent the extremes of stratospheric springtime temperatures seen in the MERRA analysis and correspond to analogous extrema in planetary wave activity. The three years with enhanced planetary wave activity (1997, 2011 and 2013) are shown to coincide with the recently identified stratospheric Frozen In Anticyclone (FrIAC) phenomenon. FrIACs in 1997 and 2013 are associated with early PMC onsets; however, the dramatic FrIAC of 2011 is not. This may be because the 2011 FrIAC occurred too early in the spring. The link between NH PMC onset and stratospheric FrIAC occurrences represents a new mode of coupling between the stratosphere and mesosphere. Since FrIACs appear to be more frequent in recent years, we speculate that as a result, PMCs may occur earlier as well. Finally we compare the zonal mean zonal winds and observed gravity wave activity for the FrIACs of 2011 and 2013. We find no evidence that gravity wave activity was favored in 2013 relative to 2011, thus suggesting that direct forcing by planetary waves was the key mechanism in accelerating the cooling and moistening of the NH mesopause region in May of 2013.

      PubDate: 2015-07-17T21:49:37Z
  • The influence of PMCs on water vapor and drivers behind PMC variability
           from SOFIE observations
    • Abstract: Publication date: Available online 16 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Mark E. Hervig, David E. Siskind, Scott M. Bailey, James M. Russell III
      Observations from the Solar Occultation For Ice Experiment (SOFIE) are used to quantify relationships between polar mesospheric clouds (PMC) and their environment. Dehydration due to ice growth is found to be greatest ∼1.8km above the height of peak ice mass density on average, and H2O enhancement due to sublimation is greatest near the bottom of the PMC layer. The dehydration and hydration layers contain a similar amount of H2O, although less than is found in ice layers, a difference that may be due to meridional transport. Because PMCs modify the surrounding water vapor, PMC-H2O relationships can be misleading and recommendations are made for dealing with this issue. The dependence of PMCs on water vapor and temperature was quantified, accounting for the effects of ice on water vapor. The approach examined inter-annual variations and considered the subset of PMCs detected by the Solar Backscatter Ultraviolet (SBUV) instruments, which are less sensitive than SOFIE. Results in the Northern Hemisphere indicate that PMC variations are dominated by temperature, but that a combination of temperature and water vapor provides the best explanation of the observations. In the Southern Hemisphere PMC variability is attributed primarily to temperature, with water vapor playing a minor role. The subset of SBUV PMCs are found to be one third as sensitive to changing temperature as the entire PMC population observed by SOFIE. Finally, an approach is presented which allows temperature and water vapor anomalies to be estimated from various PMC data sets such as SBUV. Using recently reported SBUV PMC trends at 64–74°N latitude with the results of this study indicates a cooling trend of −0.27±0.14K decade−1 and a water vapor increase of +0.66±0.34% decade−1 (both at 80–84km). This cooling trend agrees with reports based on observations in the middle atmosphere at similar latitudes. The water vapor increase is lower than expected due to increasing methane, although this difference may be consistent with H2O loss due to photolysis at PMC altitudes.

      PubDate: 2015-07-17T21:49:37Z
  • Stratiform/convective rain delineation for TRMM microwave imager
    • Abstract: Publication date: Available online 14 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Tanvir Islam, Prashant K. Srivastava, Qiang Dai, Manika Gupta, Wan Zurina Wan Jaafar
      This article investigates the potential for using machine learning algorithms to delineate stratiform/convective (S/C) rain regimes for passive microwave imager taking calibrated brightness temperatures as only spectral parameters. The algorithms have been implemented for the Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI), and calibrated as well as validated taking the Precipitation Radar (PR) S/C information as the target class variables. Two different algorithms are particularly explored for the delineation. The first one is metaheuristic adaptive boosting algorithm that includes the real, gentle, and modest versions of the AdaBoost. The second one is the classical linear discriminant analysis that includes the Fisher's and penalized versions of the linear discriminant analysis. Furthermore, prior to the development of the delineation algorithms, a feature selection analysis has been conducted for a total of 85 features, which contains the combinations of brightness temperatures from 10GHz to 85GHz and some derived indexes, such as scattering index, polarization corrected temperature, and polarization difference with the help of mutual information aided minimal redundancy maximal relevance criterion (mRMR). It has been found that the polarization corrected temperature at 85GHz and the features derived from the “addition” operator associated with the 85GHz channels have good statistical dependency to the S/C target class variables. Further, it has been shown how the mRMR feature selection technique helps to reduce the number of features without deteriorating the results when applying through the machine learning algorithms. The proposed scheme is able to delineate the S/C rain regimes with reasonable accuracy. Based on the statistical validation experience from the validation period, the Matthews correlation coefficients are in the range of ~0.60–0.70. Since, the proposed method does not rely on any a priori information, this makes it very suitable to any other microwave sensors having similar channels to the TMI. The method could possibly benefit the constellation sensors in the Global Precipitation Measurement (GPM) mission era.

      PubDate: 2015-07-17T21:49:37Z
  • Comparison of peak height of the F2-layer (hmF2) measurements with
           IRI-2012, IRI-2007 and IRI-2001 models predictions above Roquetes station
           (Spain) during the ascending phase of the solar cycle 24
    • Abstract: Publication date: Available online 10 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Fahmi A. Mohammed
      This research aims to validate IRI-2012 program and examine its accuracy in predicting peak height of the F2- layer (hmF2) above Roquetes. The seasonal hourly means of the ionosphere F2 peak height parameter (hmF2) above Roquetes station, Spain, (located at latitude close to the latitude of Iraq, 41°N) were analyzed and the results were compared with IRI-2012, IRI-2007 and IRI-2001, using CCIR (Comite´ Consultatif International des Radio Communications) option. The analysis covered quiet and disturbed days during various seasons of 2013(the ascending phase of the solar cycle 24). In general, it is found that the predicted values of hmF2 overestimate the observed ones during all seasons, except Summer, whereas it underestimate at day hours. Also, it is found that the maximum percentage relative deviation of hmF2 occurred during Winter at 8LT, while the minimum occurred during Autumnat 22 LT.

      PubDate: 2015-07-13T17:59:33Z
  • Dynamics of vertical ionospheric inhomogeneities over Irkutsk during
           06:00-06:20UT 11/03/2011 caused by Tohoku earthquake
    • Abstract: Publication date: Available online 10 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): O.I. Berngardt , G.V. Kotovich , S.Ya. Mikhailov , A.V. Podlesnyi
      We study dynamics of vertical ionospheric irregularities caused by Tohoku earthquake 11/03/2011 (38.3N, 142.4E) at a distance of 3400km from the epicenter. Equivalent horizontal velocities of propagation in the ionosphere and vertical quasi-wavelength of the wave-like ionospheric irregularities, generated by the earthquake, are calculated. Based on the data of quasi-vertical sounding at Usolie-Tory path (midpoint - 52.3N, 103E, 120km distance), dynamics of vertical mid-scale inhomogeneities of the plasma frequency profile was reconstructed with a fine temporal resolution (60 seconds). As a result of numerical simulation involving the data from TALAYA seismic station (TLY, 51.7N, 103.7E) and comparison with the experiment it is shown that vertical ionospheric irregularities of 5-40km quasi-wavelength observed from 06:00 to 06:20 UT are qualitatively explained by traveling of the acoustic shock wave cone (Mach cone ) from a supersonic ground source - the seismic wave. It is demonstrated that the most likely sources of the shock wave were Z and E components of the seismic oscillations observed at TLY station. Irregularities observed after 06:20UT were apparently linked with other mechanisms. It is found that current temporal resolution of CHIRP ionosonde (60 seconds) and accuracy of the ionogram inversion technique used are not enough for detailed diagnosis of dynamics of the fine spatial vertical structures generated by the earthquake.

      PubDate: 2015-07-13T17:59:33Z
  • Size dependence of ozone lamina characteristics and their correlations
    • Abstract: Publication date: Available online 9 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Peter Krizan , Jan Lastovicka , Michal Kozubek
      Ozone profiles contain narrow layers of substantially enhanced or reduced ozone, called positive and negative laminae, respectively. They reflect both evolutions of stratospheric ozone content and stratospheric dynamics. Here we deal only with positive laminae. The following lamina characteristics are investigated in dependence on lamina size: the number of laminae per profile, the overall ozone amount in laminae per profile and the ozone amount in one lamina at the European ozonosonde stations. An important role of the vertical resolution of ozonesonde measurements is specified. Lamina characteristics for Legionowo and Lindenberg, and small lamina (< 2mPa) characteristics for all stations suffer with effects of vertical resolution of measurements. For this reason they are not used here for long-term trend investigations. The long-term evolution of the ozone amount in one lamina does not display a trend. The results for the three remaining stations, Hohenpeissenberg, Payerne and Uccle, are largely consistent with our previous results on lamina behaviour, which means that our previous results on trends in laminae (e.g., Krizan and Lastovicka, 2005; Lastovicka et al., 2014) are basically correct. The number of laminae per profile and the overall ozone amount in laminae per profile show negative trends before (1979-1995) and rather positive trends after (1996-2011) the reversal of trends in total columnar ozone over Europe. Both parameters reach the highest values for small laminae and with increasing size they decrease. Correlations between characteristics of laminae of different size ranges at individual stations are better for neighbour lamina ranges than for distant lamina ranges. The number of statistically significant correlations of laminae of the same size between pairs of stations is much higher for large laminae above 4mPa, probably due to processes responsible for their formation and their expected larger horizontal size.

      PubDate: 2015-07-13T17:59:33Z
  • Wave-3 and wave-4 patterns in the low- and mid-latitude ionospheric TEC
    • Abstract: Publication date: Available online 6 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Sicheng Wang , Sixun Huang , Hanxian fang
      The JPL global ionospheric maps (GIMs) from January 1, 1999 to December 31, 2013 are analyzed using the space-time spectral analysis method to obtain the tidal patterns in the ionospheric TEC. The results show that noticeable wave-3 and wave-4 signatures can be detected near the crests of equatorial ionospheric anomaly (EIA) regions. Wave-4 structure is comprised predominately by DE3 component, while wave-3 structure is comprised mainly by DE2 component. SPW4 (SPW3) component also accounts for the wave-4 (wave-3) signature. The absolute amplitude of all the aforementioned tidal and SPW signatures shows a saturation effect on the solar activity. The tidal components have significant seasonal variations, with the prominent latitudinal asymmetry. The relative amplitude of zonal mean TEC, however, shows persistent patterns with little solar activity dependence. DE3 is intense in March and September/October, and is weak in northern winter and southern summer. DE2 is strong in the southern hemisphere, and is weak in boreal winter. The amplitude of tide DE3 in TEC is smaller than that of DE2.

      PubDate: 2015-07-09T02:28:34Z
  • Spectral Analysis comparisons of Fourier-Theory-based methods and Minimum
           Variance (Capon) methods
    • Abstract: Publication date: Available online 6 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Marcial Garbanzo-Salas , Wayne. K. Hocking
      In recent years, adaptive (data dependent) methods have been introduced into many areas where Fourier spectral analysis has traditionally been used. Although the data-dependent methods are often advanced as being superior to Fourier methods, they do require some finesse in choosing the order of the relevant filters. In performing comparisons, we have found some concerns about the mappings, particularly when related to cases involving many spectral lines or even continuous spectral signals. Using numerical simulations, several comparisons between Fourier transform procedures and minimum variance method (MVM) have been performed. For multiple frequency signals, the MVM resolves most of the frequency content only for filters that have more degrees of freedom than the number of distinct spectral lines in the signal. In the case of Gaussian spectral approximation, MVM will always underestimate the width, and can misappropriate the location of spectral line in some circumstances. Large filters can be used to improve results with multiple frequency signals, but are computationally inefficient. Significant biases can occur when using MVM to study spectral information or echo power from the atmosphere. Artifacts and artificial narrowing of turbulent layers is one such impact.

      PubDate: 2015-07-09T02:28:34Z
  • The 27-day Rotational Variations in Total Solar Irradiance Observations:
    • Abstract: Publication date: Available online 4 July 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jae N. Lee , Robert F. Cahalan , Dong L. Wu
      During the last decade, observations from SORCE (Solar Radiation and Climate Experiment)/TIM (Total Irradiance Monitor), ACRIMSAT (Active Cavity Radiometer Irradiance Monitor Satellite)/ACRIM III, and SOHO (SOlar and Heliospheric Observatory)/VIRGO (Variability of IRradiance and Gravity Oscillations Sun PhotoMeter) provided Total Solar Irradiance (TSI) measurements with unprecedented accuracy and stability to determine the amount of solar irradiance reaching the top of the atmosphere and how solar irradiance varies on different time scales. These three independent measurements are analyzed using the EEMD (Ensemble Empirical Mode Decomposition) method to characterize the phase and amplitude of the 27-day solar rotational variation in TSI. The mode decomposition clearly identifies a 27-day solar rotational signature on TSI measurements. The rotational variations of TSI from the three independent observations are generally consistent with each other, despite different mean TSI values. During the declining phase of solar cycle 23, the amplitude of TSI 27-day variations is as high as 0.8W/m2 (~0.05%), while during the rising phase of solar cycle 24, the amplitude is up to 0.4W/m2 (~0.04%). During the minimum phase (2008-2009), the amplitude of the rotational mode is only ~0.1W/m2. The correlation of this rotational mode between TIM and ACRIM III is ~0.92 and the slope of the local peak values is ~0.98. The correlation between TIM and VIRGO is ~0.96 and the slope of the local peak values is ~0.98, very similar to the slope with ACRIM III.

      PubDate: 2015-07-05T02:22:05Z
  • Application of aerosol optical properties to estimate aerosol type from
           ground-based remote sensing observation at urban area of northeastern
    • Abstract: Publication date: Available online 27 June 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Huizheng Che , Hujia Zhao , Yunfei Wu , Xiangao Xia , Jun Zhu , Oleg Dubovik , Victor Estelles , Yanjun Ma , Yangfeng Wang , Hong Wang , Yaqiang Wang , Xiaoye Zhang , Guangyu Shi
      Aerosol optical properties were derived from ground-based sunphotometer observations between 2009-2013 at three urban sites of Shenyang, Anshan, Fushun in northeastern China. The annual means for extinction aerosol optical depths (EAOD) at 500nm were 0.57±0.38, 0.52±0.35, and 0.41±0.31 at Shenyang, Anshan, Fushun, respectively. The corresponding annual means for the extinction Angstrom exponents (EAE) computed for the wavelengths of 440 and 870nm were 0.86±0.32, 0.86±0.34 and 0.91±0.35, respectively, indicating that urban area of Northeast China were affected by both coarse and fine particles. Hygroscopic growth in summer and incursions of dust aerosols in spring were evidently revealed from the analysis of the relationship between EAE and δEAE (the EAE difference, δEAE=EAE(440,670)- EAE(670,870)). The annual mean absorption aerosol optical depths (AAOD440nm) values at Shenyang, Anshan, Fushun were 0.15±0.11, 0.10±0.07, 0.08±0.04, respectively. The annual mean absorption Angstrom exponents (AAE440-870nm) values were 0.86±0.24, 1.19±0.39, 1.33±0.36 at Shenyang, Anshan, Fushun, respectively. When the AAEs were close to unity at Anshan, the absorption aerosol particles evidently consisted of black carbon from coal combustion and motor vehicles. Larger AAEs at Fushun were indicative of absorbing aerosols mainly from biomass burning and mineral dust. The AAE at Shenyang was<1 which may be consistent with black carbon particles with absorbing or non-absorbing coatings. Analysis of the relationship between the AAEs and extinction Angstrom exponents showed that the aerosol populations at these three sites could be classified as “mixed-small particles” including anthropogenic particles and secondary organic aerosol with highly variable sphericity fractions.

      PubDate: 2015-06-30T10:52:34Z
  • Review and Testing Analysis of Moupfouma rain rate Model for Southern
    • Abstract: Publication date: Available online 24 June 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Chandrika P , Vijaya Bhaskara Rao S , Kiran Kumar N.V.P , Narayana Rao T
      Suitability of the analytical model by Moupfouma in modeling the one-minute rain rate distributions at tropical stations of Thiruvananthapuram and Gadanki is studied. The Climatic dependent parameters of the model governing the slope of the one-minute rain rate distributions are acclimatized and validated. The paper also presents rain rate distributions for Thiruvananthapuram and Gadanki. Performance of the model with newly refined climatic dependent parameters is assessed. The Moupfouma model is observed to model the one minute rain rate distributions with a maximum percentage relative error of 14% at 0.001% of time, and with approximately zero relative error at 0.01% of time in an average year. The climatic dependent parameters governing the slope of one-minute rain rate distributions are proposed for Southern India.

      PubDate: 2015-06-25T11:12:12Z
  • Analysis of aerosol scattering properties measured by a nephelometer at a
           coastal-rural site in the Atlantic southwest of the Iberian Peninsula
    • Abstract: Publication date: Available online 24 June 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Juan F. López , Victoria E. Cachorro , Angel M. de Frutos
      Aerosol hemispherical scattering and the backscattering coefficients, σsp, σbsc, have been measured using a 3-wavelength(450, 550 and 700nm) integrating nephelometer over two years (January 2006 to May 2008) in the coastal area of the Gulf of Cádiz, in the southwest of the Iberian Peninsula. These coefficients have been carefully analyzed starting with the impact of corrections on the measurements of σsp: i.e., drift calibration constants do not modify the mean value in our data series. However, the selection of dry data (with RH less than 50%) modifies substantially the number of data and the resulting mean value of σsp is now 14% lower, which is compensated when the angular truncation correction is applied. The characterization and features of σsp, σbsc, and the derived parameters αsp (alpha Ångström exponent) and b (the backscatter ratio) has been analysed, as annual, seasonal and diurnal evolution. A general statistic based on hourly data gives mean values and standard deviation of σsp (500 nm) = 48 ±38Mm−1 with a median of 38 Mm-1, and σbsc(500nm)=5.6±3.8Mm-1 with a median of 4.6 Mm-1. Thus, these values show moderate-low values but with a large range of variation considering the existing measured values over the Iberian Peninsula. The median value of σsp (500nm) is an indicator that events of high aerosol burden are frequent presenting a substantial influence on the daily averages. The alpha Ångström exponent, αsp, derived from the pairs 450/700 nm gives a mean value 1.35±0.54 with a median of 1.47 and with the most frequent value of 1.7, thus indicating the prevalence of medium size particles but with a significant influence of fine particles. The b ratio has the same value for mean and median, 0.12±0.02, showing a decrease with increasing values of σsp. Annual and daily cycles have been also analyzed showing the complex behaviour of the optical properties at this coastal site where cold and warn periods show very different characteristics. Besides, the daily cycle is strongly influenced by the breeze conditions. According to the information extracted from the σsp-αsp relationship this rural Atlantic site presents prevalence of mixed marine-continental aerosols but with significant influence of local anthropogenic sources. Desert dust particles were also discriminated which are not frequently reported in the data of “in situ” aerosols.

      PubDate: 2015-06-25T11:12:12Z
  • A statistical study of internal gravity wave characteristics using the
           combined Irkutsk incoherent scatter radar and Digisonde data
    • Abstract: Publication date: Available online 24 June 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.V. Medvedev , K.G. Ratovsky , M.V. Tolstikov , S.S. Alsatkin , A.A. Shcherbakov
      Using previously developed methods for determining the three-dimensional spatial-temporal structure of traveling ionospheric disturbances and the automatic detection of wave disturbances, we analyzed data obtained simultaneously with the Irkutsk Incoherent Scatter Radar and Irkutsk ionosonde. The analysis relies on long continuous series of observations acquired during winter seasons in 2010–2014. We obtained representative statistics of traveling ionospheric disturbances characteristics including the full velocity vector. We analyzed the characteristics of traveling ionospheric disturbances with 1–6 hour periods comparing them against the dispersion relations for internal gravity waves in the Boussinesq and Hines approximations. It was shown that, with due consideration for the horizontal neutral wind, most of the observed ionospheric disturbances agrees with the laws of internal gravity waves propagation in the upper atmosphere. It was found that azimuthal anisotropy of internal gravity waves characteristics allows us to obtain the diurnal variations of zonal and meridional neutral winds in the upper atmosphere.

      PubDate: 2015-06-25T11:12:12Z
  • Night-time light ion transition height behaviour over the Kharkiv
           (50°N, 36°E) IS radar during the equinoxes of 2006–2010
    • Abstract: Publication date: September 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 132
      Author(s): Dmytro V. Kotov , Vladimír Truhlík , Phil G. Richards , Stanimir Stankov , Oleksandr V. Bogomaz , Leonid F. Chernogor , Igor F. Domnin
      This research investigates anomalous nighttime ion density behaviour over the Kharkiv, Ukraine incoherent scatter radar (49.6° N, 36.3° E, 45.3° inv) during the equinoxes of 2006–2010. The observations show that the altitude of the transition from O+ to lighter ions was much lower than empirical and physical models predict. The standard physical model produces very good agreement for the O+ densities but underestimates the H+ densities by a factor of 2 in March 2006 and a factor of 3 in March 2009. The anomalously low transition height is a result of similar lowering of the ionospheric peak height and also of significantly increased H+ density. The lower ionospheric peak height may be caused by weaker nighttime neutral winds. The calculations indicate that the higher measured topside ionosphere H+ densities are most likely due to higher neutral hydrogen densities. Both factors could be the result of weaker than usual magnetic activity, which would reduce the energy input to high latitudes. Prolonged low activity periods could cause a global redistribution of hydrogen and also allow more neutral hydrogen to settle down from the exosphere into the mid-latitude ionosphere. The finding of the need for higher H densities agrees well with recent H-alpha airglow measurements and it is important for accurate modelling of plasmasphere refilling rates and night-time N m F 2 values.

      PubDate: 2015-06-20T13:39:38Z
  • A comparison of stratospheric photochemical response to different
           reconstructions of solar ultraviolet radiative variability
    • Abstract: Publication date: Available online 15 June 2015
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Cassandra Bolduc , Michel S. Bourqui , Paul Charbonneau
      We present calculations of stratospheric chemical abundances variations between different levels of solar activity using a simple photochemistry model in transient chemistry mode. Different models for the reconstruction of the solar spectrum, as well as observations from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) and Spectral Irradiance Monitor (SIM) on the SOlar Radiation and Climate Experiment (SORCE) satellite, are used as inputs to the calculations. We put the emphasis on the MOnte CArlo Spectral Solar Irradiance Model (MOCASSIM) reconstructions, which cover the spectral interval from 150 to 400nm and extend from 1610 to present. We compare our results with those obtained with the Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) model as well as with the Magnesium-Neutron Monitor (MGNM) model over a period of time spanning the ascending phase of Cycle 22. We also perform the calculations using SORCE composite spectra for the descending phase of Cycle 23 and with the reconstructed MOCASSIM, NRLSSI and MGNM spectra for the same period for comparison. Finally, we compare the chemical abundances obtained for the Maunder Minimum with those obtained for the Cycle 23 minimum (in March 2009) and find that stratospheric ozone concentration was slightly higher during the recent minimum, consequent to the small positive variability between the MOCASSIM spectra for both epochs, especially below 260nm. We find that the response in stratospheric ozone is not only dependent on the variability amplitude in the solar spectrum (especially in the 200–240nm band), but also significantly on the base level of the minimum solar spectrum.

      PubDate: 2015-06-20T13:39:38Z
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