for Journals by Title or ISSN
for Articles by Keywords
help
  Subjects -> METEOROLOGY (Total: 75 journals)
Acta Meteorologica Sinica     Hybrid Journal   (2 followers)
Advances in Atmospheric Sciences     Hybrid Journal   (4 followers)
Advances in Meteorology     Open Access   (4 followers)
Aeolian Research     Hybrid Journal   (1 follower)
Agricultural and Forest Meteorology     Hybrid Journal   (5 followers)
American Journal of Climate Change     Open Access   (5 followers)
Asian Journal of Earth Sciences     Open Access   (16 followers)
Atmósfera     Open Access  
Atmosphere     Open Access   (2 followers)
Atmosphere-Ocean     Full-text available via subscription   (3 followers)
Atmospheric Chemistry and Physics (ACP)     Open Access   (11 followers)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (7 followers)
Atmospheric Research     Hybrid Journal   (14 followers)
Atmospheric Science Letters     Hybrid Journal   (5 followers)
Boundary-Layer Meteorology     Hybrid Journal   (8 followers)
Bulletin of the American Meteorological Society     Open Access   (12 followers)
Carbon Balance and Management     Open Access   (4 followers)
Climate     Open Access   (1 follower)
Climate Change Economics     Hybrid Journal   (16 followers)
Climate Dynamics     Hybrid Journal   (13 followers)
Climate law     Hybrid Journal   (1 follower)
Climate of the Past (CP)     Open Access   (3 followers)
Climate of the Past Discussions (CPD)     Open Access   (2 followers)
Climate Policy     Hybrid Journal   (19 followers)
Climate Risk Management     Open Access  
Climatic Change     Hybrid Journal   (26 followers)
Developments in Atmospheric Science     Full-text available via subscription   (3 followers)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (3 followers)
Energy & Environment     Full-text available via subscription   (12 followers)
Environmental and Climate Technologies     Open Access  
Global Meteorology     Open Access  
International Journal of Atmospheric Sciences     Open Access   (2 followers)
International Journal of Biometeorology     Hybrid Journal   (1 follower)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (5 followers)
International Journal of Climatology     Hybrid Journal   (10 followers)
International Journal of Image and Data Fusion     Hybrid Journal  
ISRN Meteorology     Open Access  
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (7 followers)
Journal of Atmospheric and Oceanic Technology     Full-text available via subscription   (10 followers)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (14 followers)
Journal of Atmospheric Chemistry     Hybrid Journal   (1 follower)
Journal of Climate     Full-text available via subscription   (20 followers)
Journal of Hydrology and Meteorology     Open Access   (2 followers)
Journal of Hydrometeorology     Full-text available via subscription   (3 followers)
Journal of Integrative Environmental Sciences     Hybrid Journal   (3 followers)
Journal of Meteorology and Climate Science     Full-text available via subscription  
Journal of Space Weather and Space Climate     Open Access   (3 followers)
Journal of the Atmospheric Sciences     Full-text available via subscription   (20 followers)
Journal of Weather Modification     Full-text available via subscription  
Large Marine Ecosystems     Full-text available via subscription   (1 follower)
Meteorologica     Open Access  
Meteorological Applications     Hybrid Journal   (1 follower)
Meteorologische Zeitschrift     Full-text available via subscription   (2 followers)
Meteorology and Atmospheric Physics     Hybrid Journal   (2 followers)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (1 follower)
Monthly Notices of the Royal Astronomical Society Letters     Hybrid Journal   (1 follower)
Monthly Weather Review     Full-text available via subscription   (10 followers)
Nature Climate Change     Full-text available via subscription   (29 followers)
Nature Reports Climate Change     Full-text available via subscription   (14 followers)
Open Journal of Modern Hydrology     Open Access   (1 follower)
Revista Brasileira de Meteorologia     Open Access   (1 follower)
Russian Meteorology and Hydrology     Hybrid Journal   (3 followers)
Space Weather     Full-text available via subscription   (3 followers)
Studia Geophysica et Geodaetica     Hybrid Journal   (4 followers)
Tellus A     Open Access   (4 followers)
Tellus B     Open Access   (6 followers)
The Cryosphere (TC)     Open Access   (1 follower)
The Cryosphere Discussions (TCD)     Open Access   (1 follower)
The Quarterly Journal of the Royal Meteorological Society     Hybrid Journal   (5 followers)
Theoretical and Applied Climatology     Hybrid Journal   (2 followers)
Weather     Hybrid Journal   (2 followers)
Weather and Climate Extremes     Open Access   (2 followers)
Weather and Forecasting     Full-text available via subscription   (1 follower)
Weatherwise     Hybrid Journal  
气候与环境研究     Full-text available via subscription  
Journal of Atmospheric and Solar-Terrestrial Physics    [16 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1364-6826
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.955]   [H-I: 56]
  • Chemical composition of aerosols over Bay of Bengal during pre-monsoon:
           Dominance of anthropogenic sources
    • Abstract: Publication date: Available online 17 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Prabha R Nair , Susan George K , S Aryasree , Salu Jacob
      Total suspended particulates were collected from the marine boundary layer of Bay of Bengal (BoB) as part of the Integrated Campaign for Aerosols gases & Radiation Budget (ICARB) conducted under the Geosphere Biosphere Programme of Indian Space Research Organisation during pre-monsoon period. These samples were analyzed to quantify various chemical species and to bring out a comprehensive and quantitative picture of the chemical composition of aerosols in the marine environment of Bay of Bengal. Almost all the species showed highest mass concentration over north/head BoB. On the other hand, their mass fractions were high over mid/south BoB which has implications on the radiative forcing in this region. The source characteristics of various species were identified using specific chemical components as tracers. Presence of significant amount of non-sea-salt aerosols (∼7–8 times of sea-salt and several trace species like Ni, Pb, Zn, etc were observed in this marine environment indicating significant continental/anthropogenic influence. An approximate estimate of the contributions of anthropogenic and natural aerosols to the total aerosol mass loading showed prominence of anthropogenic component over mid and south BoB also. Based on this study first-cut aerosol chemical models were evolved for BoB region.


      PubDate: 2014-01-20T04:31:16Z
       
  • Estimation of the Mixing layer height over a high altitude site in Central
           Himalayan region by using Doppler Lidar
    • Abstract: Publication date: Available online 17 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): K.K. Shukla , D.V. Phanikumar , Rob K. Newsom , K. Niranjan Kumar , M. Venkat Ratnam , M. Naja , Narendra Singh
      A Doppler Lidar was installed at Manora Peak, Nainital (29.4°N; 79.2°E; 1958 amsl) to estimate mixing layer height for the first time by using vertical velocity variance as basic measurement parameter for the period September – November 2011. Mixing layer height is found to be located ∼0.57±0.1km and 0.45±0.05km AGL during day and nighttime, respectively. The estimation of mixing layer height shows good correlation (R2>0.8) between different instruments and with different methods. Our results show that wavelet co-variance transform is a robust method for mixing layer height estimation.


      PubDate: 2014-01-20T04:31:16Z
       
  • Energetics of persistent turbulent layers underneath mid-level clouds
           estimated from concurrent radar and radiosonde data
    • Abstract: Publication date: Available online 18 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R. Wilson , H. Luce , H. Hashiguchi , N. Nishi , Y. Yabuki
      Two Japanese-French field campaigns devoted to studying small-scale turbulence and instabilities in the lower atmosphere were conducted in September 2011 and November 2012 at the Shigaraki Middle and Upper atmosphere (MU) Observatory (34.85°N, 136.15°E; Japan). The Very High Frequency Middle and Upper atmosphere radar (MUR) was operated with a time resolution of the order of 10s in range imaging mode allowing echo power measurements at fine range-resolutions (typically, a few tens of meters). In addition, balloons instrumented with RS92G Vaisala radiosondes were launched from the observatory during the radar operations. From the raw data of temperature, pressure and humidity, temperature turbulent layers can be identified from the detection of overturns by using the Thorpe method (1977). During the two campaigns, both radar and balloon data revealed turbulent layers of about 1.0km in depth, underneath mid-level clouds and meteorological frontal zones. They persisted for about 10 hours in the radar data. The balloon data collected were undoubtedly representative of the conditions met by the radar. Turbulence parameters associated with stably stratified flows were tentatively estimated by using different methods involving both radar and balloon observations for 4 balloon flights. These parameters included the Thorpe, buoyancy, and Ozmidov scales L T , L B and L O , potential and kinetic turbulent energies TPE and TKE, potential kinetic energy dissipation rates ϵ P and ϵ K and tubulent diffusivities K θ . The turbulence scales were found to be consistent between each other within a factor of about 2. Energy dissipation rates of 0.6mW/kg were found for 3 cases and 0.06mW/kg for one case.


      PubDate: 2014-01-20T04:31:16Z
       
  • On the pre-midnight ascent of F-layer in the June solstice during the deep
           solar minimum in 2008 over the Indian sector
    • Abstract: Publication date: Available online 13 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): D. Chakrabarty , B.G. Fejer , S. Gurubaran , Tarun K. Pant , M.A. Abdu , R. Sekar
      Investigations on the variations of the virtual height ( h ′ F ) of the base of the F-layer over Thumba (8.5°N, 77°E, dip lat 0.5°N) in 2002 (high solar activity) and 2008 (very low solar activity) under quiet geomagnetic conditions show characteristic pre-midnight rise of h ′ F in the June solstice of 2008. Comparison of the h ′ F variations in 2008 over Thumba and Fortaleza (3.9°S, 38.4°W, dip lat 1.8°S), Brazil, reveals that the pre-midnight rise of h ′ F is significantly more over Thumba during the June solstice. Drift measurements on-board the Communication/Navigation Outage Forecasting System (C/NOFS) satellite elicit that the midnight upward drift over the Indian sector during the northern summer months of 2009 is the largest, a feature that significantly weakens in 2010. C/NOFS measurements also confirm the electro-dynamical nature of the pre-midnight h ′ F rise over the Indian sector in the June solstice during the low solar activity. As the equatorial F-region vertical drifts during nighttime are controlled by E-region dynamo driven by tidal wind system, systematic wind measurements at upper mesospheric heights by an MF radar (1.98MHz) from Tirunelveli (8.7°N, 77.8°E, dip lat 0.5°S), India, during 2000–2011 are used to derive the tidal components. This reveals that the phases of both the meridional and zonal components of the diurnal tide regress while the phase of the meridional component of the semidiurnal tide significantly advances with decreasing solar activity with concomitant increases in amplitudes during the summer months. These observations suggest the possible semidiurnal tidal influence on the pre-midnight h ′ F rise over the Indian sector in the June solstice during low solar activity.


      PubDate: 2014-01-16T04:31:15Z
       
  • Interplanetary Magnetic Field By Control of Prompt Total Electron Content
           Increases During Superstorms
    • Abstract: Publication date: Available online 16 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): J. Mannucci , G. Crowley , B.T. Tsurutani , O.P. Verkhoglyadova , A. Komjathy , P. Stephens
      Large magnitude increases in ionospheric total electron content (TEC) that occur over 1–3h on the dayside are a significant manifestation of the main phases of superstorms. For the largest superstorms of solar cycle 23 (based on the Dst index), ground networks of GPS receivers measured peak total electron content increases greater than a factor of 2 relative to quiet time TEC averaged over the broad latitude band ±40° for local times 1200–1600LT. Near 30° latitude, the Halloween storms of October 29–30, 2003 appeared to produce storm-time TEC exceeding quiet time values by a factor of 5 within 2–3h of storm onset, at 1300LT. The physical cause of these large positive phase ionospheric storms is usually attributed to prompt penetration electric fields (PPEFs) initiated by Region 1 current closure through the ionosphere (Nopper and Carovillano, 1978 mechanism). An unresolved question is what determines variation of the TEC response for different superstorms. It has been suggested that the cross polar cap potential and Region 1 currents are significant factors in determining PPEF in the equatorial ionosphere, which are related to the solar wind reconnection electric field estimated by Kan-Lee and others. In this paper, we show evidence that suggests B y may be a significant factor controlling the TEC response during the main phase of superstorms. We analyzed the interplanetary conditions during the period that TEC was increasing for eight superstorms. We find that increasing daytime TEC during superstorms only occurs for large reconnection electric fields when B y magnitude is less than B z . The data suggest that B z is a far more important factor in the TEC response than the reconnection electric field. We also find that TEC decreases following its peak storm-time value for two superstorms, even though B z remains large and B y magnitudes are less than B z . Such decreases during the geomagnetic disturbance may indicate the role of magnetospheric shielding currents, or of changes in the thermosphere that have developed over the prolonged period of large solar wind electric field. Further analysis is warranted covering a wider range of storm intensities on the role of B y in affecting the daytime TEC response for a range of storm intensities.


      PubDate: 2014-01-16T04:31:15Z
       
  • Assessing the size distribution of droplets in a cloud chamber from light
           extinction data during a transient regime
    • Abstract: Publication date: Available online 8 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Sorin Nicolae Vajaiac , Valeriu Filip , Sabina Stefan , Andreea Boscornea
      The paper describes a method of assessing the size distribution of fog droplets in a cloud chamber, based on measuring the time variation of the transmission of a light beam during the gravitational settling of droplets. Using a model of light extinction by floating spherical particles, the size distribution of droplets is retrieved, along with characteristic structural parameters of the fog (total droplet concentration, liquid water content and effective radius). Moreover, the time variation of the effective radius can be readily extracted from the model. The errors of the method are also estimated and fall within acceptable limits. The method proves sensitive enough to resolve various modes in the droplet distribution and to point out changes in the distribution due to diverse types of aerosol present in the chamber or to the thermal condition of the fog. It is speculated that the method can be further simplified to reach an in-situ version for real-time field measurements.


      PubDate: 2014-01-12T04:31:18Z
       
  • Evidence of the solar Gleissberg cycle in the nitrate concentration in
           polar ice.
    • Abstract: Publication date: Available online 8 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M.G. Ogurtsov , M. Oinonen
      Two sets of nitrate (NO3 -) concentration data, obtained from Central Greenland and East Antarctic (Dronning Maud Land) ice cores, were analyzed statistically. Distinct century-scale (50–150yr) variability was revealed in both data sets during AD 1576–1990. It was found that century-type variation in Greenland and Antarctic nitrate correlates fairly significantly with the corresponding Gleissberg cycle: (a) in sunspot number over 1700–1970 AD; (b) in 10Be concentration in Central and South Greenland over 1576–1970 AD. Thus, presence of century-scale relationship between polar nitrate and solar activity was confirmed over the last 4 centuries. That proves that NO3 - concentration in polar ice caps could serve as indicator of long-term solar variability.


      PubDate: 2014-01-12T04:31:18Z
       
  • Study of probabilistic modeling of Stratospheric Ozone fluctuations over
           Pakistan and China Regions
    • Abstract: Publication date: Available online 8 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Bulbul Jan , M. Ayub Khan Yousuf Zai , Shaheen Abbas , Shabbir Hussain , Muhammad Ali , M. Rashid Kamal Ansari
      Stratospheric ozone has an essential role in terrestrial life particularly in climatic variability and protects earth biosphere from the harmful UV radiations. The present study investigates the variation of the stratospheric ozone layer over Pakistan and China for the period from 1984–2010. For this purpose a probability distribution approach is applied. In this regard the adequacy of Normal, Gamma and Log-Normal distributions are tested with the help of Kolmogorov-Smirnov D-test. It is found that most of the months, Pakistan region follow Log-normal while China region exhibits Normal probaility distribution. In addition, mean and standard deviations of monthly Ozone are also calculated. It gives more eminence to stratospheric ozone variability behavior. Furthermore, trend models are used to compute the Ozone variations for the above mentioned regions.Most of the months show increasing trend except the decreasing trend in Februery and May for Pakistan and Januray and September for China. Trend analysis contributes the economic development and hydrological planning. This research is a part of a larger research project which compares the climatic variability of Pakistan with the climatic variability of neighboring countries and the other countries of the region which are considered important in this regard. Such comparisons will appear in other communications.


      PubDate: 2014-01-12T04:31:18Z
       
  • Scattering of VHF transmitter signals by seismic-related electric
           discharges in the troposphere
    • Abstract: Publication date: Available online 8 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): V.M. Sorokin , A.K. Yaschenko , M. Hayakawa
      The scattering of VHF electromagnetic waves by random electric discharges occurring in the troposphere over a seismic region has been considered, which are caused by the disturbances of electric current in the global atmosphere–ionosphere circuit. Current disturbances are connected with the injection of charged aerosols as a result of the lifting of soil gases during earthquake preparation. It is shown that the electric field of disturbed current can reach a breakdown value at the altitudes 5–10km. The method for calculating the mean value of electromagnetic wave fields scattered by the random discharges has been elaborated, which show that the electric field of scattered wave exceeds significantly that of diffracted wave over the horizon. The results of our theory are confirmed by the observational data of VHF transmitter signals over the horizon during earthquake preparation.


      PubDate: 2014-01-12T04:31:18Z
       
  • Possible effects of atmospheric teleconnections and solar variability on
           tropospheric and stratospheric temperatures in the Northern Hemisphere
    • Abstract: Publication date: Available online 8 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): L. Sfiˆcă , M. Voiculescu
      Possible relationships between tropospheric and stratospheric temperatures in the Northern Hemisphere and atmospheric oscillations, solar and geomagnetic activity are described using correlation analysis. The dependence of correlations on season, solar activity level and phase of the Quasi Biennial Oscillation (QBO) is also investigated. An important finding is that the variability of the hemispheric tropospheric temperature is well connected to the Scandinavian Pattern, to the Pacific North American teleconnection and less with the North Atlantic Oscillation. There is also a possible link with the Southern Oscillation (SO) for winter. Solar UV and cosmic ray flux might influence tropospheric temperature during warm seasons, solar maximum or QBO West. Significant correlations between the Northern stratospheric temperature and the SO is observed especially during the Eastern phase of QBO and solar minimum. Signatures of geomagnetic variability are seen in the winter stratospheric temperature. The stratospheric temperature correlates with the cosmic ray flux and solar UV at annual level at solar maximum and QBO West. The UV effect at stratospheric level is less clear than expected. The existence of some correlations between tropospheric/stratospheric temperatures and internal and external parameters under certain climatic circumstances and during different solar cycle phases might help in identifying processes that transfer energy from the Sun to different atmospheric layers and in assessing their role in climate variability.


      PubDate: 2014-01-12T04:31:18Z
       
  • Distinctive Features of Radiation Pulses in the Very First Moment of
           Lightning Events
    • Abstract: Publication date: Available online 8 January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M.R.M. Esa , M.R. Ahmad , M. Rahman , V. Cooray
      This paper investigates the existence of distinctive features between 4 different types of lightning discharges, namely negative cloud to ground discharge (−CG), positive cloud to ground discharge (+CG), cloud discharge (IC) and isolated breakdown discharge (IB). A total of 110 very fine structure waveforms of 44 −CG, 16 +CG, 39 IC, and 11 IB discharges have been selected from a collection of 885 waveforms measured using fast electric field broadband antenna system. The measurements were carried out in Uppsala, Sweden from May to August 2010. We found that there are significant distinctions within the first 1ms among different types of lightning discharges (−CG, +CG, IC, and IB). For example, the pulses in −CG discharges are more frequent than other discharges; the pulses in +CG discharges have the highest intensity and the IC discharge pulses tend to have shorter duration.


      PubDate: 2014-01-12T04:31:18Z
       
  • Electron-ion temperature ratio estimations in the summer polar mesosphere
           when subject to HF radio wave heating
    • Abstract: Publication date: Available online 30 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): H. Pinedo , C. La Hoz , O. Havnes , M. Rietveld
      We have inferred the electron temperature enhancements above mesospheric altitudes under Polar Mesospheric Summer Echoes (PMSE) conditions when the ionosphere is exposed to artificial HF radio wave heating.The proposed method uses the dependence of the radar cross section on the electron-to-ion temperature ratio to infer the heating factor from in coherent scatter radar (ISR) power measurements above 90km.Model heating temperatures match our ISR estimations between 90 and 130km with 0.94 Pearson correlation index.The PMSE strength measured by the MORRO MSTradar is about 50% weaker during the heater-on period when the modeled electron-to-ionmesospheric temperature is approximately 10 times greater than the unperturbed value.No PMSE weakening is found when the mesospheric temperature enhancement is by a factor of three or less.The PMSE weakening and its absence are consistent with the modeled mesospheric electron temperatures.This consistency supports to the proposed method for estimating mesospheric electron temperatures achieved by independent MST and ISR radar measurements.


      PubDate: 2014-01-04T04:31:14Z
       
  • ULF Wave Modulation of the Ionospheric Parameters: Radar and Magnetometer
           Observations
    • Abstract: Publication date: Available online 30 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): V. Pilipenko , V. Belakhovsky , A. Kozlovsky , E. Fedorov , K. Kauristie
      The global Pc5 pulsations at the recovery phase of strong magnetic storm on October 31, 2003 are examined using the IMAGE magnetometer and EISCAT radar data from the tri-static Tromsø– Kiruna – Sodankylä system. This radar facility gives possibility to determine the vertical profile of basic ionospheric parameters and their variations with time cadence 30s. The comparison of magnetometer data from Tromsøwith the ionospheric parameters shows a significant (up to ∼ 60 % ) modulation by Pc5 pulsations of the electron density in the E-layer, height-integrated ionospheric conductances, and ion temperature in the F-layer. This modulation has been observed in the absence of quasi-periodic electron precipitation as evidenced by riometer data. The mechanisms underlying the modulation effects, probably, comprise the Joule ion heating by ULF wave electric field, and feeding/depleting the ionospheric electron content by the wave field-aligned current. The impact of ULF waves on the ionosphere results in a non-linear distortion of ULF wave form, as revealed by the phase portrait method.


      PubDate: 2014-01-04T04:31:14Z
       
  • Variation of Radio field strength and Radio Horizon Distance Over Three
           Stations in Nigeria
    • Abstract: Publication date: Available online 31 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.T Adediji , Mahamod Ismail , J.S. Mandeep
      In this work, we present seasonal results of radio field strength and radio horizon distance derived from the computation of surface refractivity through in-situ measurement of temperature, relative humidity and pressure across three stations (Akure, Minna and Enugu) in Nigeria. The measurements of the tropospheric parameters were made using a Davis Wireless Weather Station (Integrated Sensor Suite, ISS) installed on the ground surface at each of the stations. The study utilized data for two years of measurement (January 2008-December 2009). Results show that the values of surface refractivity were low during the dry season months and high during the wet season months. The lowest values of 323, 313 and 281N-units were observed in February for Akure, Enugu and Minna respectively, while maximum values of 372, 375 and 365N-units were observed in September, October and August for the respective locations. Also, the average value of field strength variability was found to be 6.67, 5.62 and 7.48 for Akure, Enugu and Minna respectively.


      PubDate: 2014-01-04T04:31:14Z
       
  • Corrigendum to “Effects of SSC in Geomagnetic field components H, D
           and Z at low-latitude stations during 1995–2001”
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): Remya Remanan , K. Unnikrishnan



      PubDate: 2014-01-04T04:31:14Z
       
  • Corrigendum to “Boundary layer jet on the lee side of Western Ghats
           during southwest monsoon as revealed by high resolution sodar winds”
           
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): B.S. Murthy , R. Latha , P. Sreeja



      PubDate: 2014-01-04T04:31:14Z
       
  • IFC-Ed. board
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107




      PubDate: 2014-01-04T04:31:14Z
       
  • Height-integrated Pedersen conductivity in both E and F regions from
           COSMIC observations
    • Abstract: Publication date: Available online 27 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Cheng Sheng , Yue Deng , Xinan Yue , Yanshi Huang
      Altitudinal distribution of Joule heating is very important to the thermosphere and ionosphere, which is roughly proportional to the Pedersen conductance at high latitudes. Based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites observations from 2008 to 2011, the height-integrated Pedersen conductivities in both E (100–150km) and F (150–600km) regions and their ratio γ P ( ∑ PE / ∑ PF ) have been calculated. The result shows that the maximum ratio in the northern summer hemisphere is ∼5.5, which is smaller than that from the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM v1.94) simulation (∼9). This indicates that the energy inputs into the F region may be underestimated in the model. The seasonal variations of the ratio have been investigated for both hemispheres, and an interhemispheric asymmetry has been identified. The variational trend of the ratio is similar in both hemispheres, which reaches minimum at local summer and maximum at local winter. However, the difference of the ratio from local summer to local winter in the southern hemisphere is larger than that in the northern hemisphere.


      PubDate: 2013-12-31T04:33:27Z
       
  • Threshold Magnitude for Ionospheric Response to Earthquakes
    • Abstract: Publication date: Available online 27 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): N.P. Perevalova , V.A. Sankov , E.I. Astafyeva , А.S. Zhupityaeva
      We have analyzed ionospheric response to earthquakes with magnitudes of 4.1–8.8 which occurred under quiet geomagnetic conditions in different regions of the world (the Baikal region, Kuril Islands, Japan, Greece, Indonesia, China, New Zealand, Salvador, and Chile). This investigation relied on measurements of total electron content (TEC) variations made by ground-based dual-frequency GPS receivers. To perform the analysis, we selected earthquakes with permanent GPS stations installed close by. Data processing has revealed that after 4.1–6.3-magnitude earthquakes wave disturbances in TEC variations are undetectable. We have thoroughly analyzed publications over the period of 1965–2013 which reported on registration of wave TIDs after earthquakes. This analysis demonstrated that the magnitude of the earthquakes having a wave response in the ionosphere was no less than 6.5. Based on our results and on the data from other researchers, we can conclude that there is a threshold magnitude (near 6.5) below which there are no pronounced earthquake-induced wave TEC disturbances. The probability of detection of post-earthquake TIDs with a magnitude close to the threshold depends strongly on geophysical conditions. In addition, reliable identification of the source of such TIDs generally requires many GPS stations in an earthquake zone. At low magnitudes, seismic energy is likely to be insufficient to generate acoustic waves in the neutral atmosphere which are able to induce TEC disturbances observable at the level of background fluctuations.


      PubDate: 2013-12-31T04:33:27Z
       
  • Estimating the lower ionosphere height and lightning location using
           multimode “tweek” atmospherics
    • Abstract: Publication date: February 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 108
      Author(s): A.V. Shvets , T.M. Serdiuk , Y.V. Gorishnyaya , Y. Hobara , M. Hayakawa
      There is proposed a new method of estimating the effective ionospheric height of the Earth–ionosphere waveguide and the propagation distance of tweek-atmospherics. It is based on the compensation of waveguide frequency dispersion of a tweek signal, which enables us to improve the accuracy of deducing the cutoff frequencies, especially in the presence of noise. An approach to solve the inverse problem is suggested that reduces the task of finding both the source range and the waveguide cutoff frequencies by using the multimode characteristics of tweeks to an issue of one-dimensional optimization. Based on the numerical modeling of multimode tweek-atmospherics in the Earth–ionosphere waveguide with exponential vertical conductivity profile of the lower ionosphere, it was shown that the accuracy of estimating the effective waveguide height by the new method is good as about 100–400m for the first and higher order modes. It then allows us to estimate the parameters of vertical conductivity profile of the lower ionosphere for a wide range of source distances from a few hundred to a few thousand kilometers, as long as two or more tweek harmonics can be detected. Preliminary analysis of experimental tweek records show a decrease of the effective height with increasing the mode number, and the scale height of the exponential vertical conductivity profile for the isotropic lower ionosphere model is estimated to be in a range of 0.4–2.5km.


      PubDate: 2013-12-23T04:31:15Z
       
  • Negative Cloud-to-Ground Lightning Flashes in Malaysia
    • Abstract: Publication date: Available online 14 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Z.A. Baharudin , Noor Azlinda Ahmad , J.S. Mäkelä , Mahendra Fernando , Vernon Cooray
      The characteristics of the negative cloud-to-ground lightning flashes in Malaysia are studied by analyzing the electric fields generated by the whole flash in nanosecond resolution. A total of 405 strokes obtained from 100 successive negative cloud-to-ground lightning flashes were analyzed, which were recorded from seven convective thunderstorms during the southwest monsoon period, i.e. from April to June 2009. It was found that the total number of interstroke intervals has an arithmetic mean value of 86ms, a geometric mean value of 67ms and does not depend on the return stroke order. Of the 100 negative ground flashes, 38 flashes (38%) have at least one Subsequent Return-Stroke (SRS) whose electric field peak was greater than that of the first Return-Stroke (RS). Furthermore, 58 (19%) out of 305 SRS have electric field peak larger than those of the first RS. The arithmetic and geometric mean ratio between the peak electric field of the SRS and the peak electric field of the first RS are 0.7 and 0.6, respectively. The percentage of single-stroke flashes was 16% while the mean number of strokes per flash and maximum number of stroke per flash were 4 and 14, respectively.


      PubDate: 2013-12-19T04:21:03Z
       
  • The role of electric fields in sporadic E layer formation over low
           latitudes under quiet and magnetic storm conditions
    • Abstract: Publication date: Available online 14 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M.A. Abdu , J.R. de Souza , I.S. Batista , A.M. Santos , J.H.A. Sobral , R.G. Rastogi , H Chandra
      Sporadic E layers are formed dominantly by wind shear mechanism, but their formation and dynamics are driven also by ionospheric electric fields. Investigation of low latitude sporadic E layers under quiet conditions shows that Es layer formation during post sunset hours can be disrupted or enhanced depending upon the vertical structure of the vertical electric field arising from sunset electrodynamic processes. During magnetic storms the formation and disruption of these layers are also strongly controlled by vertical Hall electric field induced by the zonal magnetospheric electric fields that penetrates to equatorial/low latitude ionosphere. Observational results on storm time Es layer responses in the Brazilian and Indian-Asian longitudes are compared. An under-shielding prompt penetration electric field (PPEF) of westward polarity that dominate the night side ionosphere, or an over-shielding electric field also of westward polarity in the evening sector can cause formation of sporadic E layers near 100km, while an eastward polarity electric field, (under-shielding/over-shielding depending upon local time) can lead to disruption of an E s layer in progress. Ionization convergence/divergence leading to the Es layer formation/disruption is driven by a vertical Hall electric field, induced by the primary zonal PPEF, in the presence of storm associated enhanced ratio of field line integrated Hall to Pedersen conductivity (∑H/(∑P). A downward polarity of the Hall electric field leads to E s layer formation, while an upward polarity causes the E s layer disruption. The ∑H/(∑P ratio can result from the night E layer conductivity enhancement due to energetic particle precipitation peculiar to the longitude of the South Atlantic Magnetic Anomaly (SAMA) and/or from a drastic reduction in integrated Pederson conductivity in the form of reduced foF2 that is observed in all longitudes.
      Graphical abstract image

      PubDate: 2013-12-19T04:21:03Z
       
  • Relationship between wind speed and sea salt aerosol production: A new
           approach
    • Abstract: Publication date: Available online 16 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): S.S. Prijith , Marina Aloysius , Mannil Mohan
      A relationship between ocean surface wind speed and sea salt aerosol production is established through a study carried out using the aerosol flux continuity equation by introducing satellite data on aerosols and ocean surface wind speed into it. This mathematical approach eliminates interferences from background aerosols and aerosol variations due to advection and convergences/divergences in wind field and correctly estimates the rate of sea salt aerosol production by winds. To avoid oceanic biogenic sources and transport from other oceanic and land regions, the study is done over ocean sites substantially remote from the continents with low chlorophyll concentrations (<0.06mg/m3) and restricting to aerosols in the bottom layer (<0.5km altitude) of the atmosphere. The surface wind speed is found to correlate better with the estimated aerosol production rate (R WS=0.99, p<0.0001) than with the bottom layer aerosol optical depth (R WB=0.97, p<0.0001). Aerosol production is observed at wind speeds even below 4m/s and the production rate is found to follow a linear relationship with ocean surface wind speed with a slope 0.0053 and an intercept 0.0163 for low as well as high winds.


      PubDate: 2013-12-19T04:21:03Z
       
  • The spatial structure of ULF-waves in the equatorial resonator localized
           at the plasmapause with the admixture of the heavy ions
    • Abstract: Publication date: Available online 14 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Olga S. Mikhailova
      The paper is devoted to the spatial structure of ULF (ultra-low frequency) Pc1 oscillations with the admixture of heavy ions taken into account. Due to dip of the Alfvén velocity in the plasmapause region and admixture of heavy ions, the wave is located in the two-dimensional resonator located near the plasmapause on the radial coordinate and near the magnetic equator along the magnetic field line. For the purposes of a qualitative analysis of the parallel resonator, the WKB approximation in the coordinate along the magnetic field line was used to obtain the wave eigenfrequencies.


      PubDate: 2013-12-19T04:21:03Z
       
  • Non-stationary corona around multi-point system in atmospheric electric
           field: II. Altitude and time variation of electric field
    • Abstract: Publication date: Available online 16 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): E.M. Bazelyan , Yu.P. Raizer , N.L. Aleksandrov
      The vertical electric field profile during thunderstorms was studied numerically and analytically above the plane ground surface with irregularities that generated ions when the surface electric field was sufficient for ion emission. The computer model of a plane emitting ions into the atmosphere simulated a limiting case of a non-stationary glow corona occurring near the tips of a multi-point ground system in a time-varying thundercloud electric field. The evolution of electric field profiles for various rates of change of thundercloud charges was analyzed and the peculiarities of electric field measurements during thunderstorms were considered. A computer model was developed to estimate the temporal evolution of electric field above a multi-point coronating system. Conditions under which the electric field evolution above a multi-electrode system is similar to that above a plane emitting surface were determined. The evolution of the surface electric field below coronating points in a multi-electrode system was calculated. Conditions when the surface electric field tends to the thundercloud electric field necessary for corona onset in a multi-point system were obtained.


      PubDate: 2013-12-19T04:21:03Z
       
  • Experimental investigation of slope flows via image analysis techniques
    • Abstract: Publication date: Available online 17 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Moroni Monica , Giorgilli Marco , Cenedese Antonio
      A vessel filled with distilled water is used to simulate the local circulation in the surroundings of an urban area that is situated in a mountain valley. The purpose of this study is to establish if the experimental setup is suitable for the investigation of katabatic and anabatic flows and their interaction with an urban heat island. Flow fields are derived by means of Feature Tracking and temperature fields are directly measured with thermocouples. The technique employed allows obtaining a high spatio-temporal resolution, providing robust statistics for the characterization of the fluid-dynamic field. General qualitative comparisons are made with expectations from analytical models. It appeared that the experimental setup as used in this study can be used for reproducing the phenomena occurring in the atmospheric boundary layer.


      PubDate: 2013-12-19T04:21:03Z
       
  • Eliminating the second-order ionospheric error in dual-frequency global
           navigation satellite systems
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): М.V. Tinin , E.V. Konetskaya
      Errors in Global Navigation Satellite Systems (GNSS) measurements, which occur during receiver positioning, are largely associated with the presence of an inhomogeneous dispersive medium (ionosphere) between a satellite and a receiver. In common dual-frequency measurements, only the first-order ionospheric error can be eliminated. The necessity of taking into account the higher-order ionospheric errors stems from high accuracy requirements to receiver positioning (of order of millimetres) for some applications. It has been found before that the second-order error, associated with the geomagnetic field, is approximately proportional to the first-order error. This fact not only simplified the calculation of the second-order error, but provided a method of dual-frequency measurements that can simultaneously eliminate the first- and second-order errors. Here we verify this method by numerical simulation and show possibility of dual-frequency GNSS measurements with the accuracy of order of millimetres.


      PubDate: 2013-12-19T04:21:03Z
       
  • Behaviour of ionospheric magnitudes of F2 region over Tucumán during
           a deep solar minimum and comparison with the IRI 2012 model predictions
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): R.G. Ezquer , J.L. López , L.A. Scidá , M.A. Cabrera , B. Zolesi , C. Bianchi , M. Pezzopane , E. Zuccheretti , M. Mosert
      In this paper we analyze the behaviour of the critical frequency of the F2 region of the ionosphere (foF2) and the height of the maximum density of free electrons in F2 region (hmF2) over Tucumán (26.9°S, 294.6°E), during the deep solar minimum occurred in 2008–2009. Data used were compared with those obtained at solar minimum observed in 1975–1976 In addition, we check the validity of the International Reference Ionosphere model (IRI), in the version 2012, to predict the maximum free electron density in the ionosphere (NmF2) above the mentioned station, for very low solar activity. The results show that: (a) Ionization was lowest for recent solar minimum. (b) The semmianual anomaly which are present in the behaviour of foF2 at times of increased solar activity, was not clearly observed during the period 2008–2009. This phenomenon could be related with the very low solar activity for that period, confirming the relationship of the amplitude of this anomaly with the solar activity reported by other authors. (c) In most cases, the values of hmF2 recorded in the deep solar minimum are lower than those observed in the period 1975–1976, suggesting a decrease in the height of the ionosphere in the course of time, which could be related to the greenhouse effect in the atmosphere and the anomalously low solar extreme-ultraviolet irradiance. (d) IRI predictions show significant deviations from the experimental values, indicating the need for improvements in the model.


      PubDate: 2013-12-19T04:21:03Z
       
  • Space shuttle exhaust plumes in the lower thermosphere: Advective
           transport and diffusive spreading
    • Abstract: Publication date: Available online 12 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Michael H. Stevens , Stefan Lossow , David E. Siskind , R.R. Meier , Cora E. Randall , James M. Russell III , Jo Urban , Donal Murtagh
      The space shuttle main engine plume deposited between 100–115km altitude is a valuable tracer for global-scale dynamical processes. Several studies have shown that this plume can reach the Arctic or Antarctic to form bursts of polar mesospheric clouds (PMCs) within a few days. The rapid transport of the shuttle plume is currently not reproduced by general circulation models and is not well understood. To help delineate the issues, we present the complete satellite datasets of shuttle plume observations by the Sounding of the Atmosphere using Broadband Emission Radiometry instrument and the Sub-Millimeter Radiometer instrument. From 2002–2011 these two instruments observed 27 shuttle plumes in over 600 limb scans of water vapor emission, from which we derive both advective meridional transport and diffusive spreading. Each plume is deposited at virtually the same place off the United States east coast so our results are relevant to northern mid-latitudes. We find that the advective transport for the first 6–18h following deposition depends on the local time (LT) of launch: shuttle plumes deposited later in the day (~13–22 LT) typically move south whereas they otherwise typically move north. For these younger plumes rapid transport is most favorable for launches at 6 and 18 LT, when the displacement is 10° in latitude corresponding to an average wind speed of 30m/s. For plumes between 18–30h old some show average sustained meridional speeds of 30m/s. For plumes between 30–54h old the observations suggest a seasonal dependence to the meridional transport, peaking near the beginning of year at 24m/s. The diffusive spreading of the plume superimposed on the transport is on average 23m/s in 24h. The plume observations show large variations in both meridional transport and diffusive spreading so that accurate modeling requires knowledge of the winds specific to each case. The combination of transport and spreading from the STS-118 plume in August 2007 formed bright PMCs between 75–85° N a day after launch. These are the highest latitude Arctic PMCs formed by shuttle exhaust reported to date.


      PubDate: 2013-12-15T15:04:32Z
       
  • Plasma pressure distribution in the surrounding the Earth plasma ring and
           its role in the magnetospheric dynamics
    • Abstract: Publication date: Available online 12 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): E.E. Antonova , I.P. Kirpichev , M.V. Stepanova
      We analyzed the characteristics of the plasma region surrounding the Earth at the geocentric distances between 6 and 15R E using the data of THEMIS mission from April 2007 to September 2012. The obtained averaged distributions of plasma pressure, of pressure anisotropy, and of magnetic field near the equatorial plane showed the presence of a ring-shaped structure surrounding the Earth. It was found that for quiet geomagnetic conditions the plasma pressure is nearly isotropic for all magnetic local times at geocentric distances >6R E . Taking into consideration that the minimal values of the magnetic field at the field lines near noon are shifted from the equatorial plane, we estimate the value of plasma beta parameter in the region of minimal values of the magnetic field using the Tsyganenko-2001 magnetic field model. It was found that the values of plasma beta parameter are of the order of unity for the nightside part of the ring-shaped structure in the equatorial plane and for the region of minimal values of the magnetic field in the dayside, indicating that the ring-shaped structure should play an active role in the magnetic field distortion. Comparison of obtained distribution of plasma pressure at the equatorial plane with the values of plasma pressure at low altitudes, showed that the considerable part of the auroral oval can be mapped into the analyzed plasma ring. The role of the high-beta plasma ring surrounding the Earth for Earth-Sun System disturbances is discussed.


      PubDate: 2013-12-15T15:04:32Z
       
  • Impact of aerosol on surface reaching solar irradiance over Mohal in the
           northwestern Himalaya, India
    • Abstract: Publication date: Available online 12 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Raj Paul Guleria , Jagdish Chandra Kuniyal , Pitamber Prasad Dhyani , Ranjan Joshi , Nand Lal Sharma
      The present study, for the first time during 2007, is focused to examine the impact of aerosols on surface reaching solar irradiance over Mohal (31.9°N, 77.12°E, 1154m amsl) in the northwestern part of the Indian Himalaya. The study also aims to estimate shortwave aerosol radiative forcing (SWARF) and its effect on regional climate. The multi-wavelength solar radiometer (MWR) is used to measure aerosol optical depth (AOD) over a wider spectrum, i.e. ultraviolet, visible and near-infrared. The AOD is obtained by analyzing the data from MWR following the Langley technique. The radiative transfer model is used along with Optical Properties of Aerosols and Clouds model to estimate the SWARF. Aerosol shows a great efficiency to reduce substantial fraction of energy from the surface reaching direct solar beam, i.e. 154Wm−2 μm−1 per unit AOD at 0.5μm. The SWARF at the surface, top of the atmosphere and the atmosphere is estimated to be −18.5±1.7, +0.6±3.7 and +19.1±3.1Wm−2, respectively. The large SWARF at the surface stood during the summer (April-July), while small during the monsoon (August-September). Moderate SWARF is obtained in the autumn (October-November) and winter (December-March). The study estimates a notable extinction in incoming solar radiation relatively with lower atmospheric heating from 0.41 to 0.73Kday−1. The potential effect of aerosol is found relatively higher on high aerosol loading days. On these days, the lower atmospheric heating increases by a factor 1.8 (during dust events) and 1.7 (during biomass burning). This study concludes that aerosols produce significant reduction in incoming solar radiation with substantial increase in lower atmospheric heating, leading to a remarkable effect on the atmospheric stability. In addition, as a subject of future interest, the present study has also important implications on the atmospheric circulation and regional climate.


      PubDate: 2013-12-15T15:04:32Z
       
  • Simulation of high power-aperture Rayleigh lidar for upper atmospheric
           studies
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): John Westerhoff , Gary R. Swenson
      The objective of this research effort is to investigate the use of a high power-aperture Rayleigh lidar to measure neutral density and temperature in the upper atmosphere, into the lower thermosphere (>100km). The scientific interest with this system is to obtain measurements of atmospheric tides, planetary and gravity wave amplitudes and phase in the lower thermosphere. Measurement of waves into the lower thermosphere is accomplished using Rayleigh lidar methods with high power-aperture (PA) products using new technology lasers and large collecting apertures, resulting in PA of 50–700Wm2. This paper describes the simulation of high PA Rayleigh lidar systems and estimates their capability to measure gravity waves and tides in the mesosphere and lower thermosphere. Both traditional backscatter and bistatic (imaging) methods are simulated. Simulations show that substantive measurements can be achieved for characterizing gravity waves at altitudes >90km and atmospheric tides at altitudes >100km for this lidar system. Measurements of density and temperature to 10% precision are possible up to 120km.


      PubDate: 2013-12-11T10:34:31Z
       
  • High latitude artificial periodic irregularity observations with the
           upgraded EISCAT heating facility
    • Abstract: Publication date: December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 105–106
      Author(s): Juha Vierinen , Antti Kero , Michael T. Rietveld
      We present a recently developed ionospheric modification experiment that produces artificial periodic irregularities in the ionosphere and uses them to make observations of the spatiotemporal behaviour of the irregularities. In addition, the method can be used to measure Faraday rotation and vertical velocities. We also introduce a novel experiment that allows monitoring the formation of the irregularities during heating, in addition to observing their decay after heating. The first measurements indicate, contrary to existing theory, that the amplitude of the radar echoes from the periodic irregularities grows faster than they decay. We focus on the API effects in the D- and E-region of the ionosphere.


      PubDate: 2013-12-07T04:24:44Z
       
  • Observation of VHF incoherent scatter spectra disturbed by HF heating
    • Abstract: Publication date: December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 105–106
      Author(s): Musong Cheng , Bin Xu , Zhensen Wu , Haiying Li , Zhange Wang , Zhengwen Xu , Jun Wu , Jian Wu
      We report on EISCAT ionospheric heating experiments carried out on 13 September 2010 at Tromsø, Norway. This paper focuses on the long-lasting enhanced ion- and plasma-lines observed by the VHF incoherent scatter radar. In previous experiments, the enhanced ion-lines observed by VHF radar lasted ~200ms. Observations of long-lasting enhanced ion- and plasma-lines in the VHF radar have not been reported before. The enhanced lines may be caused by Parametric Decay Instability (PDI). In addition, the VHF data show that the enhanced ion-lines are descending in altitude with time during the heater-on period. Likewise, the temporal and spatial evolution of the enhanced plasma-lines also show a similar morphology and generally occur at the same height. At last a possible mechanism for the altitude evolution is given in this paper.


      PubDate: 2013-12-07T04:24:44Z
       
  • Variability of Aerosol Optical Depth and their impact on cloud properties
           in Pakistan
    • Abstract: Publication date: Available online 3 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Alam Khan , Rehana Khan , Thomas Blaschke , Azam Mukhtiar
      This study analyzes seasonal and temporal variations in aerosol optical depth (AOD), and the impact of these variations on the properties of clouds over five cities in Pakistan, using Moderate Resolution Imaging Spectroradiometer (MODIS) data, obtained from the Terra satellite during the period (2001–2011). The obtained results indicated seasonal variation in AOD, with a high value of 2.3, in summer and low values of 0.2, in winter for the costal part of the region. The relationship between AOD and other cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud optical thickness (COT), cloud liquid water path (CLWP), cloud top temperature (CTT), and cloud top pressure (CTP) were analyzed. On a temporal scale, latitudinal variations of both WV and AOD produce high correlations (>0.6) in some regions, and moderate correlations (0.4–0.6) in the other regions. An increasing trend in CF with AOD was found over urban regions in the period of observations. The CF values were higher for Lahore than the other selected regions during the whole period. During autumn and winter seasons the correlation was found to be positive between AOD and CLWP, while negative correlation was observed during the other seasons for all the selected regions. COT showed negative correlation with AOD at all locations except Karachi during spring and summer seasons. AOD showed a positive correlation with CTP and CTT for the spring season and a negative correlation was observed for summer for all investigated regions. Furthermore, in warm clouds AOD and CTP were negatively correlated for all regions except Peshawar, whereas, AOD and CTT were positively correlated for all regions except Karachi. In cold clouds the relationships between AOD and CTP, and AOD and CTT were negative, except Karachi. Thus meteorological parameters, geographical conditions, as well as warm and cold clouds are the causative factors for AOD and CTP, and AOD and CTT variations.


      PubDate: 2013-12-07T04:24:44Z
       
  • Plasma modifications induced by an X-mode HF heater wave in the high
           latitude F region of the ionosphere
    • Abstract: Publication date: December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 105–106
      Author(s): N.F. Blagoveshchenskaya , T.D. Borisova , T.K. Yeoman , M.T. Rietveld , I. Häggström , I.M. Ivanova
      We presented experimental results of strong plasma modifications induced by X-mode powerful HF radio waves injected towards the magnetic zenith into the high latitude F region of the ionosphere. The experiments were conducted in 2009–2011 using the EISCAT Heating facility, UHF incoherent scatter radar and the EISCAT ionosonde at Tromsø, Norway; and the CUTLASS SuperDARN HF coherent radar at Hankasalmi, Finland. The results showed that the X-mode HF pump wave can generate strong small-scale artificial field aligned irregularities (AFAIs) in the F region of the high-latitude ionosphere. These irregularities, with spatial scales across the geomagnetic field of the order of 9–15m, were excited when the heater frequency (f H) was above the ordinary-mode critical frequency (foF2) by 0.1–1.2MHz. It was found that the X-mode AFAIs appeared between 10s and 4min after the heater is turned on. Their decay time varied over a wide range between 3min and 30min. The excitation of X-mode AFAIs was accompanied by electron temperature (Te) enhancements and an increase in the electron density (Ne) depending on the effective radiated power (ERP). Under ERPs of about 75–180MW the Te enhances up to 50% above the background level and an increase in Ne of up to 30% were observed. Dramatic changes in the Te and Ne behavior occurred at effective radiated powers of about 370–840MW, when the Ne and Te values increased up to 100% above the background ones. It was found that AFAIs, Ne and Te enhancements occurred, when the extraordinary-mode critical frequency (fxF2) lied in the frequency range f H–f ce/2≤fxF2≤f H+f ce/2, where f ce is the electron gyrofrequency. The strong Ne enhancements were observed only in the magnetic field-aligned direction in a wide altitude range up to the upper limit of the UHF radar measurements. In addition, the maximum value of Ne is about 50km higher than the Te enhancement peak. Such electron density enhancements (artificial ducts) cannot be explained by temperature-dependent reaction rates. They can be attributed to HF-induced ionization production by accelerated electrons. The possible mechanisms for plasma modifications induced by powerful X-mode HF radio waves were discussed.
      Highlights ► Strong plasma modification induced by high power X-mode HF radio waves. ► Excitation of artificial irregularities in the F region of the high-latitude ionosphere. ► Enhancements in the electron temperature and density under X-mode HF heating. ► Generation of artificial ducts of strongly enhanced electron density

      PubDate: 2013-12-07T04:24:44Z
       
  • IFC-Ed. board
    • Abstract: Publication date: December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 105–106




      PubDate: 2013-12-07T04:24:44Z
       
  • High-latitude Geospace Environment studied by Incoherent Scatter Radars
    • Abstract: Publication date: December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 105–106
      Author(s): Michael J. Kosch



      PubDate: 2013-12-07T04:24:44Z
       
  • Lower ionosphere electron density profiling with data from VLF receivers
    • Abstract: Publication date: Available online 5 December 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Josef Hubeňák , Jan Šlégr
      In this work we present the method for estimation of Wait's parameters H ′ and β directly from measured electrical intensities of distant VLF transmitters. Very simple approach using Earth-ionosphere waveguide with highly conductive walls is used.


      PubDate: 2013-12-07T04:24:44Z
       
  • A low free-parameter stochastic model of daily Forbush decrease indices
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): Sankar Narayan Patra , Gautam Bhattacharya , Subhash Chandra Panja , Koushik Ghosh
      Forbush decrease is a rapid decrease in the observed galactic cosmic ray intensity pattern occurring after a coronal mass ejection. In the present paper we have analyzed the daily Forbush decrease indices from January, 1967 to December, 2003 generated in IZMIRAN, Russia. First the entire indices have been smoothened and next we have made an attempt to fit a suitable stochastic model for the present time series by means of a necessary number of process parameters. The study reveals that the present time series is governed by a stationary autoregressive process of order 2 with a trace of white noise. Under the consideration of the present model we have shown that chaos is not expected in the present time series which opens up the possibility of validation of its forecasting (both short-term and long-term) as well as its multi-periodic behavior.


      PubDate: 2013-11-29T04:31:29Z
       
  • A method for the automatic calculation of electron density profiles from
           vertical incidence ionograms
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): Chunhua Jiang , Guobin Yang , Zhengyu Zhao , Yuannong Zhang , Peng Zhu , Hengqing Sun , Chen Zhou
      Vertical incidence ionograms indicate ionospheric characteristics over the ionosonde station, from which electron density profiles can be derived. This paper describes a method for the automatic calculation of electron density profiles from vertical incidence ionograms. First, the method calculates the initial parameters of the quasi-parabolic segments (QPS) model by using the International Reference Ionosphere (IRI) model, the Nequick2 model, image processing techniques, and the Empirical Orthogonal Function (EOF). Once the initial parameters have been calculated the method then adjusts those to obtain the electron density profiles and synthesized traces that match the recorded ionograms. The algorithm then selects the best-fit synthesized trace and corresponding parameters as output from the candidate ones. Furthermore, the corresponding electron density profile of the recorded ionogram is calculated by using the best-fit parameters of the QPS model. To further test the feasibility of the proposed method, we apply it to some ionograms that were recorded at Wuhan during different seasons. As a result, our results demonstrate that the proposed method is feasible for the automatic calculation of electron density profiles.


      PubDate: 2013-11-25T04:15:47Z
       
  • Modelling N21P contamination in auroral O+ emissions
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): J.D. Spry , O. Jokiaho , B.S. Lanchester , D.K. Whiter
      Modelling of N21P (5,3) contamination at the O+ doublet emissions in the region of 732nm is presented. The method is derived from a known relationship between emission from the N21P (5,3) band and emissions from the N21P (5,2), (4,1) and (3,0) bands. A synthetic molecular spectrum is used to quantify a temperature-dependent emission ratio of these band systems as a function of filter characteristics and emission altitude. Five optical observations of high-energy auroral periods on 9 January 2008 are compared with results from the synthetic spectrum. Two cameras from a high sensitivity, high frame rate (20Hz) ground based imager in combination with a co-located high resolution spectrograph are used to identify events which are dominated by molecular nitrogen emissions. There is good agreement between the observed and modelled ratios. The temperatures associated with these ratios agree well with temperature profiles extracted from fitting the synthetic spectra to the spectrograph data. A synthetic spectrum is important for future work when the removal of N21P (5,3) contamination from O+ (2P) doublet emissions is required at high temporal resolution.


      PubDate: 2013-11-25T04:15:47Z
       
  • Thunderstorm Ground Enhancements–model and relation to lightning
           flashes
    • Abstract: Publication date: Available online 15 November 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A. Chilingarian
      In the beginning of last century C.T.R. Wilson proposed that strong electric field of the thunderclouds might accelerate electrons to very high energies. However, this and many other electromagnetic processes in our atmosphere are poorly understood till now; the key questions about the thundercloud electrification and lightning initiation remain unanswered. During recent decades several observations of gamma ray, electron and neutron fluxes correlated with thunderstorms were reported. Nonetheless, the origin of these fluxes is under debate till now. The direct registration of the particle showers initiated by the runaway electrons (the most popular theory) was missing. We present the experimental evidence of the microsecond duration electron bursts originated from runaway electrons accelerated in thunderclouds. The electron acceleration downward becomes possible after creation of the Lower Positive Charged Region below the main negative charged layer in the middle of the thundercloud. Our analysis is based on the vast thunderstorm data from the Aragats Mountain in Armenia, 3200m above sea level. Varieties of particle detectors located at Aragats Space Environmental Center are registering neutral and charged particle fluxes correlated with thunderstorms, so-called Thunderstorm Ground Enhancements. Simultaneously the electric mills and lightning detectors are monitoring the near-surface electric field and types of lightning flashes. In the paper we present the comprehensive model of TGE initiation. We demonstrate the necessity of the Lower positive charge region development for the lower dipole operation and TGE initiation. Our observations establish direct relationship of the negative electric field strength and rain rate with TGE amplitude.


      PubDate: 2013-11-17T04:31:28Z
       
  • Turbulent scattering for radars: A summary
    • Abstract: Publication date: January 2014
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 107
      Author(s): Franz-Josef Lübken
      In this paper some classical concepts regarding scattering of radio waves on turbulent structures in the ionosphere are summarized. Spectral representations according to Batchelor and Driscoll & Kennedy are compared and the role of various potential tracer gradients is elucidated. Systematic similarities and differences in the representation of the impact of these tracers on scatter intensity are investigated. The importance of turbulence and background parameters for radar volume reflectivities is discussed. This study highlights the importance of measuring these parameters as completely and reliably as possible when interpreting the strength of backscattered radar signal in terms of turbulent and atmospheric background parameters.


      PubDate: 2013-11-17T04:31:28Z
       
  • Ionospheric quasi-biennial oscillation in global TEC observations
    • Abstract: Publication date: Available online 9 November 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): W. Tang , X.-H. Xue , J. Lei , X.-K. Dou
      The total electron content (TEC) observations were analyzed for the ionospheric quasi-biennial oscillations (QBO) during the period of 1999–2011 in a global perspective. Longitudinal and monthly means of TEC data were calculated to reveal the global characteristics and long-period variations in ionosphere. The Lomb-Scargle periodogram methods and wavelet spectral analysis were applied to the residuals of TEC, which are obtained from subtracting the fittings with solar index, F10.7. The ionospheric QBO signal only appears during solar maximum, existing in all latitudes from 50°S to 50°N, and the period is within 22–34 months. In the equatorial region, the QBO exhibits a significant feature of equatorial ionospheric anomaly (EIA), where the transition of phases occurs 2–6 months later than in high latitude. The correlation coefficient with the stratospheric QBO reaches 0.704. It can be assumed that stratospheric QBO influences the QBO phenomenon in ionosphere; nevertheless, the present results do not permit one to conclude the mechanism.


      PubDate: 2013-11-13T04:31:32Z
       
  • Ground-based observations of the relations between lightning
           charge-moment-change and the physical and optical properties of column
           sprites
    • Abstract: Publication date: Available online 11 November 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Roy Yaniv , Yoav Yair , Colin Price , Jo'zsef Bor , Mitsutero Sato , Yasuhide Hobara , Steve Cummer , Jingbo Li , Adam Devir
      Optical observations of 66 sprites, using a calibrated commercial CCD camera, were conducted in the 2009–2010 and 2010 - 2011 winter seasons as part of the ILAN (Imaging of Lightning And Nocturnal flashes) campaign in the vicinity of Israel and the eastern Mediterranean. We looked for correlations between the properties of the parent lightning (specifically, the charge moment change; CMC) to the properties of column sprites, such as the measured radiance, the length of column sprites and the number of column elements in each sprite event. The brightness of sprites positively correlates with the CMC (0.7) and so does the length of sprite elements (0.83). These results are in agreement with previous studies, and support the QE model of sprite generation.


      PubDate: 2013-11-13T04:31:32Z
       
  • Weighted Mean Temperature Model for Extra Tropical Region of India
    • Abstract: Publication date: Available online 11 November 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): D. Singh , J.K. Ghosh , D. Kashyap
      The Global Positioning System (GPS) estimates Precipitable Water Vapor (PWV) from Zenith Wet Delay (ZWD) using a key parameter called water vapor weighted mean temperature (Tm) of the atmosphere. However, Tm must be tuned to the specific area and location. Therefore, for estimation of PWV using GPS within the region covered between New Delhi and Srinagar, site specific as well as a regional Tm model has been developed as a function of surface temperature using six years radiosonde data. The result shows that the root mean square error (rmse) of the developed site-specific Tm model is about 3.5°K at New Delhi and Patiala. However, the rmse of the developed site-specific Tm model at Srinagar is in the range of 4–5.5°K. It has been found that the site specific Tm model is slightly (0.1–0.5°K) better than the developed regional Tm model at New Delhi and Patiala, however, the error is more at Srinagar. It finds that the site-specific model is better than the regional and the global model in predicting PWV and provides sub mm accuracy within this region. However, the developed regional model provides the same level of accuracy in estimating PWV and more suitable for this region compared to other regional and global model. The GPS PWV has shown an accuracy of about 6.5mm using site specific and regional Tm model and found comparatively better than other regional and global Tm model.


      PubDate: 2013-11-13T04:31:32Z
       
  • Ionospheric effects of the Mt. Kirishima volcanic eruption as seen from
           subionospheric VLF observations
    • Abstract: Publication date: Available online 11 November 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A. Rozhnoi , M. Hayakawa , M. Solovieva , Y. Hobara , V. Fedun
      Data from the Pacific network of VLF receivers have been used to study the response of the lower ionosphere to the January 2011 Mt. Kirishima (South Japan) volcanic eruption. A major explosive eruption occurred on January 27, which was preceded by several small eruptions. Perturbations of nighttime subionospheric VLF signals have been detected on the day of the first small eruption on January 18 (UT) with the maximum observed about 1.5 hours after the eruption. The nighttime signal remained disturbed during the subsequent pre-eruptive and eruptive activity of Mt. Kirishima. The daytime perturbations were not observed. The frequency of the maximum spectral amplitude was found to be in the range of periods of 6–30min, which corresponds to the periods of internal gravity waves. These results suggest that the observed VLF ionospheric effects can possibly be produced by the penetration of gravity waves caused by the volcanic activity into the ionosphere.


      PubDate: 2013-11-13T04:31:32Z
       
  • Markov processes and Zipf's Law in daily solar irradiation at earth's
           surface
    • Abstract: Publication date: Available online 11 November 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): J.M. Vindel , J. Polo
      Sequences of two consecutive days of solar irradiation (global horizontal and direct normal) have been studied here by different approaches. The frequency versus rank relationships have been analysed as an attempt to explore whether the Zifp's law is fulfilled, yielding to a partial fulfilment and observing that a good logarithmic fit can be applied to the data in the whole range. In addition, the pdfs of increments in two consecutive daily irradiation values are also studied, showing a relationship between persistence and the coefficients of the logarithmic fit. Finally, it has been shown that a Markov process can represent properly sequences of two consecutive daily irradiation values, for both global horizontal and direct normal components. Thus, synthetic series can be generated by Markov chains for characterizing daily global and direct irradiation.


      PubDate: 2013-11-13T04:31:32Z
       
  • Why have geomagnetic storms been so weak during the recent solar minimum
           and the rising phase of cycle 24?
    • Abstract: Publication date: Available online 8 November 2013
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): E.K.J. Kilpua , J.G. Luhmann , L.K. Jian , C.T. Russell , Y. Li
      The minimum following solar cycle 23 was the deepest and longest since the dawn of the space age. In this paper we examine geomagnetic activity using Dst and AE indices, interplanetary magnetic field (IMF) and plasma conditions, and the properties and occurrence rate of interplanetary coronal mass ejections (ICMEs) during two periods around the last two solar minima and rising phases (Period 1: 1995–1999 and Period 2: 2006–2012). The data is obtained from the 1-hour OMNI database. Geomagnetic activity was considerably weaker during Period 2 than during Period 1, in particular in terms of Dst. We show that the responses of AE and Dst depend on whether it is solar wind speed or the southward IMF component (B S ) that controls the variations in solar wind driving electric field (E Y ). We conclude that weak Dst activity during Period 2 was primarily a consequence of weak B S and presumably further weakened due to low solar wind densities. In contrast, solar wind speed did not show significant differences between our two study periods and the high-speed solar wind during Period 2 maintained AE activity despite of weak B S . The weakness of B S during Period 2 was attributed in particular to the lack of strong and long-duration ICMEs. We show that for our study periods there was a clear annual north-south IMF asymmetry, which affected in particular the intense Dst activity. This implies that the annual amount of intense Dst activity may rather be determined by the coincidence of what magnetic structure the strong ICMEs encountering the Earth have than by the solar cycle size.


      PubDate: 2013-11-09T05:03:32Z
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2014