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Showing 1 - 36 of 36 Journals sorted alphabetically
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 33)
Advances in Climate Change Research     Open Access   (Followers: 10)
Advances in Meteorology     Open Access   (Followers: 18)
Advances in Statistical Climatology, Meteorology and Oceanography     Open Access   (Followers: 2)
Aeolian Research     Hybrid Journal   (Followers: 5)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 14)
American Journal of Climate Change     Open Access   (Followers: 15)
Atmósfera     Open Access   (Followers: 1)
Atmosphere     Open Access   (Followers: 21)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 12)
Atmospheric and Oceanic Science Letters     Open Access   (Followers: 1)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 28)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 10)
Atmospheric Research     Hybrid Journal   (Followers: 54)
Atmospheric Science Letters     Open Access   (Followers: 28)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 22)
Bulletin of the American Meteorological Society     Open Access   (Followers: 32)
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: 12)
Climate Change Responses     Open Access   (Followers: 4)
Climate Dynamics     Hybrid Journal   (Followers: 28)
Climate law     Hybrid Journal   (Followers: 4)
Climate of the Past (CP)     Open Access   (Followers: 4)
Climate of the Past Discussions (CPD)     Open Access   (Followers: 1)
Climate Policy     Hybrid Journal   (Followers: 29)
Climate Research     Hybrid Journal   (Followers: 5)
Climate Risk Management     Open Access  
Climate Services     Open Access  
Climate Summary of South Africa     Full-text available via subscription  
Climatic Change     Hybrid Journal   (Followers: 54)
Current Climate Change Reports     Hybrid Journal   (Followers: 3)
Developments in Atmospheric Science     Full-text available via subscription   (Followers: 15)
Dynamics and Statistics of the Climate System     Open Access   (Followers: 2)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 10)
Earth Perspectives - Transdisciplinarity Enabled     Open Access  
Energy & Environment     Hybrid Journal   (Followers: 16)
Environmental and Climate Technologies     Open Access   (Followers: 3)
Global Meteorology     Open Access   (Followers: 6)
International Journal of Atmospheric Sciences     Open Access   (Followers: 23)
International Journal of Biometeorology     Hybrid Journal   (Followers: 1)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (Followers: 13)
International Journal of Climatology     Hybrid Journal   (Followers: 24)
International Journal of Image and Data Fusion     Hybrid Journal   (Followers: 2)
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (Followers: 25)
Journal of Atmospheric and Oceanic Technology     Full-text available via subscription   (Followers: 30)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 127)
Journal of Atmospheric Chemistry     Hybrid Journal   (Followers: 21)
Journal of Climate     Full-text available via subscription   (Followers: 40)
Journal of Hydrology and Meteorology     Open Access   (Followers: 14)
Journal of Hydrometeorology     Full-text available via subscription   (Followers: 6)
Journal of Integrative Environmental Sciences     Hybrid Journal   (Followers: 4)
Journal of Meteorology and Climate Science     Full-text available via subscription   (Followers: 7)
Journal of Space Weather and Space Climate     Open Access   (Followers: 20)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 68)
Journal of the Meteorological Society of Japan     Partially Free   (Followers: 1)
Journal of Weather Modification     Full-text available via subscription   (Followers: 1)
Large Marine Ecosystems     Full-text available via subscription  
Mathematics of Climate and Weather Forecasting     Open Access   (Followers: 4)
Mediterranean Marine Science     Open Access   (Followers: 1)
Meteorologica     Open Access   (Followers: 1)
Meteorological Applications     Hybrid Journal   (Followers: 4)
Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 2)
Meteorology and Atmospheric Physics     Hybrid Journal   (Followers: 20)
Mètode Science Studies Journal : Annual Review     Open Access  
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 5)
Monthly Notices of the Royal Astronomical Society Letters     Hybrid Journal   (Followers: 4)
Monthly Weather Review     Full-text available via subscription   (Followers: 25)
Nature Climate Change     Full-text available via subscription   (Followers: 61)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 26)
Open Journal of Modern Hydrology     Open Access   (Followers: 4)
Revista Brasileira de Meteorologia     Open Access   (Followers: 1)
Revista Iberoamericana de Bioeconomía y Cambio Climático     Open Access  
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 3)
Space Weather     Full-text available via subscription   (Followers: 16)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 1)
Tellus A     Open Access   (Followers: 22)
Tellus B     Open Access   (Followers: 20)
The Cryosphere (TC)     Open Access   (Followers: 5)
The Cryosphere Discussions (TCD)     Open Access   (Followers: 3)
The Quarterly Journal of the Royal Meteorological Society     Hybrid Journal   (Followers: 21)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 6)
Urban Climate     Hybrid Journal  
Weather     Hybrid Journal   (Followers: 12)
Weather and Climate Extremes     Open Access   (Followers: 7)
Weather and Forecasting     Full-text available via subscription   (Followers: 15)
Weatherwise     Hybrid Journal   (Followers: 1)
气候与环境研究     Full-text available via subscription   (Followers: 1)
Journal Cover Journal of Atmospheric and Solar-Terrestrial Physics
  [SJR: 0.934]   [H-I: 70]   [127 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [3039 journals]
  • Electrical conductivity channels in the atmosphere produced by
           relativistic-electron microbursts from the magnetosphere
    • Authors: Joseph E. Borovsky
      Pages: 22 - 26
      Abstract: Publication date: March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 155
      Author(s): Joseph E. Borovsky
      The properties of a cylindrical-shaped magnetic-field-aligned channel of electrical conductivity produced by the precipitation of relativistic-electrons into the atmosphere during a spatially localized magnetospheric microburst are estimated. The conducting channel connects the middle atmosphere (~50km) to the ionosphere. A channel diameter of ~ 8km with an electric conductivity of 1.2×10−9 Ω−1m−1 near the bottom and 1.8×10−7 Ω−1m−1 higher up is found. In the fair-weather electric field, the higher-conductivity portions of the channel can carry substantial electrical currents.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.01.004
      Issue No: Vol. 155 (2017)
  • First observations of electron gyro-harmonic effects under X-mode HF
           pumping the high latitude ionospheric F-region
    • Authors: N.F. Blagoveshchenskaya; T.D. Borisova; A.S. Kalishin; T.K. Yeoman; I. Häggström
      Pages: 36 - 49
      Abstract: Publication date: March 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 155
      Author(s): N.F. Blagoveshchenskaya, T.D. Borisova, A.S. Kalishin, T.K. Yeoman, I. Häggström
      We provide the first experimental evidence of the sensitivity of phenomena induced by extraordinary (X-mode) polarized HF high power radio waves to pump frequency stepping across the fifth electron gyro-harmonic (5fce) from below to above. The results were obtained at the EISCAT (European Incoherent Scatter Scientific Association) HF heater facility near Tromsø under effective radiated powers of 456–715MW, when the HF pump wave was transmitted into the magnetic zenith. We have analyzed the behavior and intensities of various spectral lines in the narrowband stimulated electromagnetic emission (SEE) spectra observed far from the heater, HF-enhanced plasma and ion lines (HFPL and HFIL) from EISCAT UHF incoherent scatter radar spectra, and artificial field-aligned irregularities from CUTLASS (Co-operative UK Twin Located Auroral Sounding System) observations, depending on the frequency offset of the pump field relative to the 5fce. At pump frequencies below 5fce the narrowband SEE spectra exhibited very intense so-called stimulated ion Bernstein scatter (SIBS), accompanied by other spectral components, associated with stimulated Brillouin scatter (SBS), which are greatly suppressed and disappeared in the vicinity of 5fce and did not reappear at fH>5fce. As the pump frequency reached 5fce, the abrupt enhancements of the HFPL and HFIL power, the appearance of cascade lines in the plasma line spectra, and the onset of increasing CUTLASS backscatter power occurred. That is opposite to the ordinary mode (O-mode) effects in the vicinity of 5fce. The X-mode pumping at frequencies below and in the vicinity of the fifth electron gyro-harmonic clearly demonstrated an ascending altitude of generation of induced plasma and ion lines from the initial interaction height, whereas for O-mode heating the region of interaction descended. The observations are consistent with the coexistence of the electron acceleration along and across the geomagnetic field at fH<5fce, while only very strong electron acceleration along the magnetic field was observed at fH≥5fce.

      PubDate: 2017-02-10T12:24:31Z
      DOI: 10.1016/j.jastp.2017.02.003
      Issue No: Vol. 155 (2017)
  • ANFIS, SVM and ANN soft-computing techniques to estimate daily global
           solar radiation in a warm sub-humid environment
    • Authors: Victor H. Quej; Javier Almorox; Javier A. Arnaldo; Laurel Saito
      Pages: 62 - 70
      Abstract: Publication date: Available online 6 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Victor H. Quej, Javier Almorox, Javier A. Arnaldo, Laurel Saito
      Daily solar radiation is an important variable in many models. In this paper, the accuracy and performance of three soft computing techniques (i.e., adaptive neuro-fuzzy inference system (ANFIS), artificial neural network (ANN) and support vector machine (SVM)) were assessed for predicting daily horizontal global solar radiation from measured meteorological variables in the Yucatán Peninsula, México. Model performance was assessed with statistical indicators such as root mean squared error (RMSE), mean absolute error (MAE) and coefficient of determination (R2). The performance assessment indicates that the SVM technique with requirements of daily maximum and minimum air temperature, extraterrestrial solar radiation and rainfall has better performance than the other techniques and may be a promising alternative to the usual approaches for predicting solar radiation.

      PubDate: 2017-02-10T12:24:31Z
      DOI: 10.1016/j.jastp.2017.02.002
      Issue No: Vol. 155 (2017)
  • Analysis of a grid ionospheric vertical delay and its bounding errors over
           West African sub-Saharan region
    • Authors: O.E. Abe; X. Otero Villamide; C. Paparini; S.M. Radicella; B. Nava
      Pages: 67 - 74
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): O.E. Abe, X. Otero Villamide, C. Paparini, S.M. Radicella, B. Nava
      Investigating the effects of the Equatorial Ionization Anomaly (EIA) ionosphere and space weather on Global Navigation Satellite Systems (GNSS) is very crucial, and a key to successful implementation of a GNSS augmentation system (SBAS) over the equatorial and low-latitude regions. A possible ionospheric vertical delay (GIVD, Grid Ionospheric Vertical Delay) broadcast at a Ionospheric Grid Point (IGP) and its confidence bounds errors (GIVE, Grid Ionospheric Vertical Error) are analyzed and compared with the ionospheric vertical delay estimated at a nearby user location over the West African Sub-Saharan region. Since African sub-Saharan ionosphere falls within the EIA region, which is always characterized by a disturbance in form of irregularities after sunset, and the disturbance is even more during the geomagnetically quiet conditions unlike middle latitudes, the need to have a reliable ionospheric threat model to cater for the nighttime ionospheric plasma irregularities for the future SBAS user is essential. The study was done during the most quiet and disturbed geomagnetic conditions on October 2013. A specific low latitude EGNOS-like algorithm, based on single thin layer model, was engaged to simulate SBAS message in the study. Our preliminary results indicate that, the estimated GIVE detects and protects a potential SBAS user against sampled ionospheric plasma irregularities over the region with a steep increment in GIVE to non-monitored after local sunset to post midnight. This corresponds to the onset of the usual ionospheric plasma irregularities in the region. The results further confirm that the effects of the geomagnetic storms on the ionosphere are not consistent in affecting GNSS applications over the region. Finally, this paper suggests further work to be investigated in order to improve the threat integrity model activity, and thereby enhance the availability of the future SBAS over African sub-Saharan region.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.015
      Issue No: Vol. 154 (2017)
  • Investigation of atmospheric anomalies associated with Kashmir and Awaran
    • Authors: Irfan Mahmood; Muhammad Farooq Iqbal; Muhammad Imran Shahzad; Saddam Qaiser
      Pages: 75 - 85
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Irfan Mahmood, Muhammad Farooq Iqbal, Muhammad Imran Shahzad, Saddam Qaiser
      The earthquake precursors' anomalies at diverse elevation ranges over the seismogenic region and prior to the seismic events are perceived using Satellite Remote Sensing (SRS) techniques and reanalysis datasets. In the current research, seismic precursors are obtained by analyzing anomalies in Outgoing Longwave Radiation (OLR), Air Temperature (AT), and Relative Humidity (RH) before the two strong Mw>7 earthquakes in Pakistan occurred on 8th October 2005 in Azad Jammu Kashmir with Mw 7.6, and 24th September 2013 in Awaran, Balochistan with Mw 7.7. Multi-parameter data were computed based on multi-year background data for anomalies computation. Results indicate significant transient variations in observed parameters before the main event. Detailed analysis suggests presence of pre-seismic activities one to three weeks prior to the main earthquake event that vanishes after the event. These anomalies are due to increase in temperature after release of gases and physical and chemical interactions on earth surface before the earthquake. The parameter variations behavior for both Kashmir and Awaran earthquake events are similar to other earthquakes in different regions of the world. This study suggests that energy release is not concentrated to a single fault but instead is released along the fault zone. The influence of earthquake events on lightning were also investigated and it was concluded that there is a significant atmospheric lightning activity after the earthquake suggesting a strong possibility for an earthquake induced thunderstorm. This study is valuable for identifying earthquake precursors especially in earthquake prone areas.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.018
      Issue No: Vol. 154 (2017)
  • Response of the middle atmosphere to the geomagnetic storm of November
    • Authors: Klemens Hocke
      Pages: 86 - 91
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Klemens Hocke
      Ozone and temperature profiles of the satellite microwave limb sounder Aura/MLS are used for the derivation of the middle atmospheric response to the geomagnetic superstorm of 9 November 2004. We find a destruction of the tertiary ozone layer at 0.022hPa (77km) in the northern winter hemisphere lasting for about one week. This effect is surely due to the solar proton event (SPE) of November 2004. At the same time, the zonal mean temperature is enhanced by 5–10K in the northern polar mesosphere. On the other hand, the zonal mean temperature is decreased by 5–10K in the northern polar stratosphere. We do not think that the strong temperature perturbations are directly related to the SPE. It seems that the polar vortex was moved by the geomagnetic storm, and this vortex movement caused the strong temperature variations in the zonal mean. However, internal variability of temperature in the polar middle atmosphere in winter without any significant link to the geomagnetic storm cannot be excluded.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.013
      Issue No: Vol. 154 (2017)
  • Advances in lightning research
    • Authors: Vernon Cooray; Farhad Rachidi
      First page: 181
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Vernon Cooray, Farhad Rachidi

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.10.014
      Issue No: Vol. 154 (2017)
  • Cloud-to-ground lightning activity in Colombia and the influence of
    • Authors: D. Aranguren; J. López; J. Inampués; H. Torres; H. Betz
      Pages: 182 - 189
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): D. Aranguren, J. López, J. Inampués, H. Torres, H. Betz
      Lightning activity on the Colombian mountains, where the altitude varies from 0 to more than 5000MSL, is studied based on VLF/LF lightning detection data and using a 2012–2013 dataset. The influence of altitude is observed by evaluating cloud-to-ground lightning incidence at different altitude intervals. The relationship between ground flash density and altitude gradient vectors is studied. Results show a clear dependence of the flash density on elevation.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.08.010
      Issue No: Vol. 154 (2017)
  • X-rays from negative laboratory sparks in air: Influence of the anode
    • Authors: Pasan Hettiarachchi; Mahbubur Rahman; Vernon Cooray; Joseph Dwyer
      Pages: 190 - 194
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Pasan Hettiarachchi, Mahbubur Rahman, Vernon Cooray, Joseph Dwyer
      In this experimental work, the influence of the grounded anode geometry is studied on the X-ray production from the laboratory sparks in air at atmospheric pressure when a negative impulse voltage is applied to a high voltage rod which served as a cathode. The result shows that the smaller the diameter of the anode, the higher the energy of X-ray bursts. This observation can be explained by the mechanism that the encounter of negative and positive streamer fronts just before the final breakdown is the event that accelerates electrons to X-ray generating energies, but may not be the only mechanism that generates X-rays.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.07.012
      Issue No: Vol. 154 (2017)
  • Characteristics of the most intense lightning storm ever recorded at the
           CN Tower
    • Authors: A.M. Hussein; S. Kazazi; M. Anwar; M. Yusouf; P. Liatos
      Pages: 195 - 206
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): A.M. Hussein, S. Kazazi, M. Anwar, M. Yusouf, P. Liatos
      Lightning strikes to the CN Tower have been optically observed since 1978. In 1990, five independent systems started to operate to simultaneously record parameters of lightning strikes to the tower, including the time derivative of the current, the associated electric and magnetic fields, and the channel optical characteristics. On August 24, 2011, during an unusually severe lightning storm, video records showed that the CN Tower was struck with 52 lightning flashes within 84min and 6.9s. Thus, this storm produced, on average, a flash to the tower every 99s. However, the CN Tower lightning current derivative measurement system only recorded 32 flashes, which were perfectly time-matched with 32 of the 52 video-recorded flashes. It is found that the current derivative measurement system recorded every video-recorded flash that contained at least one return stroke. Based on the analysis of video records, it is noted that each of the storm's 52 flashes contains an initial-stage current, proving that all flashes were upward initiated. This unique CN Tower storm – the most intense ever recorded at the tower – is here thoroughly analyzed, based on video and current records. The inter-flash time within the storm is found to vary between 10.6s and 274s, with an overall average of 98s. It is also found that the inter-flash time between successive non-return-stroke flashes is on average 64% longer than that for successive flashes containing return strokes. Statistical analysis of video and current data clearly reveals that the time duration of flashes containing initial-stage currents and return strokes is on average 27% longer than that of flashes that only have initial-stage currents. Furthermore, it is important to note that the time duration of the initial-stage current in flashes containing no return strokes is on average 76% longer than that in flashes containing return strokes. Therefore, it is possible to conclude that if the time duration of the initial-stage current in a flash is long enough, resulting in large charge transfer, then there is less probability of having return strokes following it. The 32 current-recorded flashes contain a total of 156 return strokes, with an average multiplicity of 4.875. It is worth mentioning that during one decade, 1992–2001, the CN Tower current derivative measurement system only recorded 478 return strokes, demonstrating that the number of return strokes recorded at the tower within about 84min is close to one third of those recorded at the tower during one decade. This finding clearly shows the great value and rarity of the presented extensive lightning current derivative data. Only one of the 32 current-recorded flashes is proved to be positive with a single return stroke. Based on current records, out of a total of 124 inter-stroke time intervals, 94% are found to be within 200ms, with an overall inter-stroke time average of 68.1ms. The maximum inter-stroke time recorded during this storm is 726.3ms, the longest ever recorded at the CN Tower.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.05.002
      Issue No: Vol. 154 (2017)
  • Characteristics of the horizontal electric field associated with nearby
           lightning return strokes
    • Authors: J.L. Yu; Y.D. Fan; J.G. Wang; R.H. Qi; M. Zhou; L. Cai; M.J. Cui; Z.J. Yuan
      Pages: 207 - 216
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): J.L. Yu, Y.D. Fan, J.G. Wang, R.H. Qi, M. Zhou, L. Cai, M.J. Cui, Z.J. Yuan
      There exists inherent difficulty in measuring the horizontal electric field (E r) associated with lightning return strokes due to the overshadowing effect of the vertical electric field component, not much progress in E r measurements were observed until now. In order to study the characteristics of E r associated with nearby lightning return strokes, the modified transmission-line model with linear current decay with height (MTLL) return stroke model and Finite Difference Time Domain (FDTD) method were used to calculate E r for 12 observation points with different distances (20, 50 100, and 200m) away from the lightning channel and different heights (0, 10, and 20m) above ground. Four characteristic parameters, namely, the return-stroke speed (v), the total length of the return stroke channel (H), the ground relative permittivity (ε) and the ground conductivity (σ), were considered. Results show that the polarity of E r changes between the ground level and the space. The influence intensity rank of the four characteristic parameters on E r at ground level is: σ>v>ε>H. The influence of the characteristic parameters on E r are more important for v≤0.6c, H≤6000m and σ≤2.5×10−3S/m.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2016.02.017
      Issue No: Vol. 154 (2017)
  • IAR signatures in the ionosphere: Modeling and observations at the
           Chibis-M microsatellite
    • Authors: V. Pilipenko; D. Dudkin; E. Fedorov; V. Korepanov; S. Klimov
      Pages: 217 - 225
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): V. Pilipenko, D. Dudkin, E. Fedorov, V. Korepanov, S. Klimov
      A peculiar feature of geomagnetic variations at middle/low latitudes in the ULF band, just below the fundamental tone of the Schumann resonance, is the occurrence of a multi-band spectral resonant structure, observed by high-sensitivity induction magnetometers during nighttime. The occurrence of such spectral structure was commonly attributed to the Ionospheric Alfvén Resonator (IAR) in the upper ionosphere. Rather surprisingly, while ground observations of the IAR are ubiquitous, there are practically no reports on the IAR signatures from space missions. According to the new paradigm, the multi-band spectral structure excited by a lightning discharge is in fact produced by a regular sequence of an original pulse from a stroke and echo-pulses reflected from the IAR upper boundary. Upon the interaction of initial lightning-generated pulse with the anisotropic lower ionosphere, it partially penetrates into the ionosphere, travels up the ionosphere as an Alfvén pulse, and reflects back from the upper IAR boundary. The superposition of the initial pulse and echo-pulses produces spectra with multiple spectral peaks. Our modeling of Alfvénic pulse propagation in a system with the altitude profile of Alfven velocity modeling the realistic ionosphere has shown that IAR spectral signatures are to be evident only on the ground and above the IAR. Inside the IAR, the superposition of upward and downward propagating pulses produces a more complicated spectral pattern and the IAR spectral signatures deteriorate. We have used electric field data from the low-orbit Chibis-M microsatellite to search for IAR signatures in the ionosphere. We found evidence that the multi-band structure revealed by spectral analysis in the frequency range of interest is indeed the result of a sequence of lightning-produced pulses. According to the proposed conception it seems possible to comprehend why the IAR signatures are less evident in the ionosphere than on the ground.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2015.12.012
      Issue No: Vol. 154 (2017)
  • Relationships between cloud-to-ground flashes and hydrometeors in a
           thunderstorm in Fujian province
    • Authors: Tinglong Zhang; Guo Zhao; Changxiong Wei; Yi Gao; Hai Yu; Fangcong Zhou
      Pages: 226 - 235
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Tinglong Zhang, Guo Zhao, Changxiong Wei, Yi Gao, Hai Yu, Fangcong Zhou
      A local severe thunderstorm, occurring near the coastal region in Fujian province, China, was chosen to study the relationships between hydrometeors and cloud-to-ground (CG) flash activities. This thunderstorm case study was carried out by using vehicle-mounted X-band dual-polarization radar on August 28, 2009. On the basis of polarimetric parameters, the hydrometeors were identified by fuzzy logic hydrometeor classification (FLHC). The results show that the thunderstorm grew into a squall line with a maximum flash rate of 85fl/5min in mature stage. Negative CG constituted approximately 97.3% of total CG flashes. More than 90% of the CG flashes occurred in the convective regions, and less than 10% occurred in the stratiform region. The strong echo volume in convective region had a positive linear correlation with the CG flashes rate. Seven types of hydrometeors, namely, rain (RN), aggregates (AG), low-density graupel (LDG), high-density graupel (HDG), vertically aligned ice crystals (VI), drizzle-light rain (DR), and ice crystals (IC), have been classified; the first five of the hydrometeors are predominant in the thunderstorm. RN is located mainly in regions warmer than 0°C; the HDG is located in the middle and lower regions colder than 0°C; and LDG and VI mainly appear in the upper portion of the thunderstorm. The ice hydrometeors seemly had a close relation with CG flashes because the total CG flash rates had a strong positive correlation with the grid number of AG, LDG, HDG, and VI in the convective region. However, the sufficient ice hydrometeors did not produce frequent CG flashes in the stratiform region. It suggests that the dynamic structure is also very important for triggering lightning flashes.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2015.11.007
      Issue No: Vol. 154 (2017)
  • A numerical study of aerosol effects on electrification of thunderstorms
    • Authors: Y.B. Tan; Z. Shi; Z.L. Chen; L. Peng; Y. Yang; X.F. Guo; H.R. Chen
      Pages: 236 - 247
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Y.B. Tan, Z. Shi, Z.L. Chen, L. Peng, Y. Yang, X.F. Guo, H.R. Chen
      Numerical simulations are performed to investigate the effect of aerosol on microphysical and electrification in thunderstorm clouds. A two-dimensional (2-D) cumulus model with electrification scheme including non-inductive and inductive charge separation is used. The concentration of aerosol particles with distribution fitted by superimposing three log-normal distributions rises from 50 to 10,000cm−3. The results show that the response of charge separation rate to the increase of aerosol concentration is nonmonotonic. When aerosol concentration is changed from 50 to 1000cm−3, a stronger formation of cloud droplet, graupel and ice crystal results in increasing charge separation via non-inductive and inductive mechanism. However, in the range of 1000–3000cm−3, vapor competition arises in the decrease of ice crystal mixing ratio and the reduction of ice crystals size leads to a slightly decrease in non-inductive charge rate, while inductive charging rate has no significant change in magnitude. Above aerosol concentration of 3000cm−3, the magnitude of charging rate which keeps steady is insensitive to the increase in aerosol concentration. The results also suggest that non-inductive charge separation between ice crystal and graupel contributes to the main upper positive charge region and the middle negative charge region. Inductive graupel–cloud droplet charge separation, on the other hand, is found to play an important role in the development of lower charge region.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2015.11.006
      Issue No: Vol. 154 (2017)
  • Impacts of a sudden stratospheric warming on the mesospheric metal layers
    • Authors: Wuhu Feng; Bernd Kaifler; Daniel R. Marsh; Josef Höffner; Ulf-Peter Hoppe; Bifford P. Williams; John M.C. Plane
      Abstract: Publication date: Available online 11 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Wuhu Feng, Bernd Kaifler, Daniel R. Marsh, Josef Höffner, Ulf-Peter Hoppe, Bifford P. Williams, John M.C. Plane
      We report measurements of atomic sodium, iron and temperature in the mesosphere and lower thermosphere (MLT) made by ground-based lidars at the ALOMAR observatory (69°N, 16°E) during a major sudden stratospheric warming (SSW) event that occurred in January 2009. The high resolution temporal observations allow the responses of the Na and Fe layers to the SSW at high northern latitudes to be investigated. A significant cooling with temperatures as low as 136K around 90km was observed on 22–23 January 2009, along with substantial depletions of the Na and Fe layers (an ~80% decrease in the column abundance with respect to the mean over the observation period). The Whole Atmosphere Community Climate Model (WACCM) incorporating the chemistry of Na, Fe, Mg and K, and nudged with reanalysis data below 60km, captures well the timing of the SSW, although the extent of the cooling and consequently the depletion in the Na and Fe layers is slightly underestimated. The model also predicts that the perturbations to the metal layers would have been observable even at equatorial latitudes. The modelled Mg layer responds in a very similar way to Na and Fe, whereas the K layer is barely affected by the SSW because of the enhanced conversion of K+ ions to K atoms at the very low temperatures.

      PubDate: 2017-02-15T12:30:13Z
      DOI: 10.1016/j.jastp.2017.02.004
  • IFC-Ed. board
    • Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154

      PubDate: 2017-02-15T12:30:13Z
  • Quasi-Biennial Oscillation signatures in the diurnal tidal winds over
           Cachoeira Paulista, Brazil
    • Authors: Luciana Rodrigues de Araújo; Lourivaldo Mota Lima; Christoph Jacobi; Paulo Prado Batista
      Abstract: Publication date: Available online 4 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Luciana Rodrigues de Araújo, Lourivaldo Mota Lima, Christoph Jacobi, Paulo Prado Batista
      Mesosphere/lower thermosphere winds obtained by meteor radar over Cachoeira Paulista (22.7°S, 45.0°W), Brazil, have been used to investigate the interannual variability of the diurnal tidal (DT) wind amplitude. The monthly DT displays year to year variations and their amplitudes are strongest during the westerly phase of the quasi-biennial oscillation (QBO) at the 30 hPa level. This can be observed in all seasons in the meridional component, whilst in the zonal component the signal is clearer during austral autumn, when the diurnal tide is strongest in this latitude. The spectrum obtained from the deseasonalized amplitudes shows a peak near 26 months in the meridional component, which can be associated to the stratospheric QBO. The QBO modulation of the DT amplitude shows a quasi-decadal variation, and it is stronger during the maximum of the solar cycle.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.02.001
  • Modelling the descent of nitric oxide during the Elevated Stratopause
           Event of January 2013
    • Authors: Yvan J. Orsolini; Varavut Limpasuvan; Kristell Pérot; Patrick Espy; Robert Hibbins; Stefan Lossow; Katarina Raaholt Larsson; Donal Murtagh
      Abstract: Publication date: Available online 4 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Yvan J. Orsolini, Varavut Limpasuvan, Kristell Pérot, Patrick Espy, Robert Hibbins, Stefan Lossow, Katarina Raaholt Larsson, Donal Murtagh
      Using simulations with a whole-atmosphere chemistry-climate model nudged by meteorological analyses, global satellite observations of nitrogen oxide (NO) and water vapour by the Sub-Millimetre Radiometer instrument (SMR), of temperature by the Microwave Limb Sounder (MLS), as well as local radar observations, this study examines the recent major stratospheric sudden warming accompanied by an elevated stratopause event (ESE) that occurred in January 2013. We examine dynamical processes during the ESE, including the role of planetary wave, gravity wave and tidal forcing on the initiation of the descent in the mesosphere-lower thermosphere (MLT) and its continuation throughout the mesosphere and stratosphere, as well as the impact of model eddy diffusion. We analyse the transport of NO and find the model underestimates the large descent of NO compared to SMR observations. We demonstrate that the discrepancy arises abruptly in the MLT region at a time when the resolved wave forcing and the planetary wave activity increase, just before the elevated stratopause reforms. The discrepancy persists despite doubling the model eddy diffusion. While the simulations reproduce an enhancement of the semi-diurnal tide following the onset of the 2013 SSW, corroborating new meteor radar observations at high northern latitudes over Trondheim (63.4°N), the modelled tidal contribution to the forcing of the mean meridional circulation and to the descent is a small portion of the resolved wave forcing, and lags it by about ten days.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.01.006
  • Raindrop size distribution and vertical velocity characteristics in the
           rainband of Hurricane Bolaven (2012) observed by a 1290MHz wind profiler
    • Authors: Dong-Kyun Kim; Dong-In Lee
      Abstract: Publication date: Available online 1 February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Dong-Kyun Kim, Dong-In Lee
      Microphysics and vertical velocity characteristics between weak and strong rainband regions of Hurricane Bolaven were investigated primarily from 1290MHz (UHF) wind profiler measurements on 27~28 August 2012. With a focus on regions with radar reflectivities greater than 30 dBZ below a melting level, raindrop size distributions (DSDs) and related rain parameters retrieved from profiler Doppler spectra were examined. Temporal variations in vertical structure and bright band from a widespread stratiform to a relatively narrow, intense rainband were examined as the rainbands move over the land in the southern coast of Korea. Based on vertical characteristics in radar reflectivity, Doppler velocity, and vertical air motion (w) profiles, the rainbands were classified into a stratiform (S) region with a strong bright band and mixed stratiform-convective (S-C) region with a weak or non-existent bright band. The retrieved w fields showed that updrafts were dominant in the mixed S-C region and downdrafts in the S region. More broad histograms in both radar reflectivity (Z) and mass-weighted mean diameter (D m ) were found in the S period. Compared to the Z distribution, rain rate (R) was more widely distributed in the mixed S-C region than in the S region. This is largely because R values were more variable in association with stronger updrafts in this region since they depend on fall velocities of raindrops. Higher R and smaller D m mean values were analyzed within relatively strong updrafts in the mixed S-C period compared to those in the S period. Even when the w correction is applied, the mean D m was still slightly smaller in the mixed S-C region, indicating that there is a relatively larger number of small drops than those in the S region.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.01.005
  • First ground-based observations of mesopause temperatures above the
           Eastern-Mediterranean Part II: OH⁎-climatology and gravity wave activity
    • Authors: Sabine Wüst; Carsten Schmidt; Michael Bittner; Israel Silber; Colin Price; Jeng-Hwa Yee; Martin G. Mlynczak; James M. Russell
      Abstract: Publication date: Available online 29 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Sabine Wüst, Carsten Schmidt, Michael Bittner, Israel Silber, Colin Price, Jeng-Hwa Yee, Martin G. Mlynczak, James M. Russell
      In this study, we present an analysis of approximately four years of nightly temperature data, acquired with the OH-spectrometer GRIPS 10 (GRound based Infrared P-branch Spectrometer), which was installed in Tel Aviv (32.11°N, 34.8°E), Israel in November, 2011 for routine measurements. As our instrument does not give any height information, we use TIMED-SABER data in order to answer the question concerning the height region our measurement technique exactly addresses. For the first time, we estimate the density of wave potential energy for periods between some minutes and some hours for this station. These values are typical for gravity waves. Since GRIPS measurements do not currently provide vertically resolved data, the Brunt-Väisälä frequency, which is needed for the estimation of potential energy density, is calculated using TIMED-SABER measurements. The monthly mean density of wave potential energy is presented for periods shorter and longer than 60min. For the winter months (November, December, and January), the data base allows the calculation of a seasonal mean for the different years. This publication is the companion paper to Silber et al. (2016). Here, we focus on oscillations with shorter periods.

      PubDate: 2017-02-04T11:57:29Z
      DOI: 10.1016/j.jastp.2017.01.003
  • Detailed study of Pi2 damped oscillations from low latitude magnetic
    • Authors: Jayashree Bulusu; Kusumita Arora; Nandini Nagarajan
      Abstract: Publication date: Available online 25 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jayashree Bulusu, Kusumita Arora, Nandini Nagarajan
      The study of low latitude damped Pi2 oscillations (40–150sec) are investigated using archived data from Chouttuppal (CPL), geoelctric observatory, operated by National Geophysical Research Institute (NGRI), Hyderabad, India. The period of investigation is during solar cycle 21 (1975–1983). All the Pi2 events identified during this period are subjected to detailed analysis for their association with substorm and non-substorm events. It is interesting to note that there is equal probability of occurrence of Pi2s with or without a substorm. The Pi2 frequencies associated with substorms showed an increased value in the post-midnight sector than compared to the Pre-midnight sectors. The non-substorm Pi2s are seen to be associated with lower levels of geomagnetic activity. The corresponding period of Pi2s decreases with increasing level of activity. While the generation of Pi2s are generally attributed to substorm onset, it is seen that the quiet time non-substorm events are related to plasmaspheric cavity mode resonances at low latitudes.

      PubDate: 2017-01-28T11:46:34Z
      DOI: 10.1016/j.jastp.2017.01.002
  • Study of 1-minute rain rate integration statistic in South Korea
    • Authors: Sujan Shrestha; Dong-You Choi
      Abstract: Publication date: Available online 21 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Sujan Shrestha, Dong-You Choi
      The design of millimeter wave communication links and the study of propagation impairments at higher frequencies due to a hydrometeor, particularly rain, require the knowledge of 1-min. rainfall rate data. Signal attenuation in space communication results are due to absorption and scattering of radio wave energy. Radio wave attenuation due to rain depends on the relevance of a 1-min. integration time for the rain rate. However, in practice, securing these data over a wide range of areas is difficult. Long term precipitation data are readily available. However, there is a need for a 1-min. rainfall rate in the rain attenuation prediction models for a better estimation of the attenuation. In this paper, we classify and survey the prominent 1-min. rain rate models. Regression analysis was performed for the study of cumulative rainfall data measured experimentally for a decade in nine different regions in South Korea, with 93 different locations, using the experimental 1-min. rainfall accumulation. To visualize the 1-min. rainfall rate applicable for the whole region for 0.01% of the time, we have considered the variation in the rain rate for 40 stations across South Korea. The Kriging interpolation method was used for spatial interpolation of the rain rate values for 0.01% of the time into a regular grid to obtain a highly consistent and predictable rainfall variation. The rain rate exceeded the 1-min. interval that was measured through the rain gauge compared to the rainfall data estimated using the International Telecommunication Union Radio Communication Sector model (ITU-R P.837-6) along with the empirical methods as Segal, Burgueno et al., Chebil and Rahman, logarithmic, exponential and global coefficients, second and third order polynomial fits, and Model 1 for Icheon regions under the regional and average coefficient set. The ITU-R P. 837-6 exibits a lower relative error percentage of 3.32 and 12.59% in the 5- and 10-min. to 1-min. conversion, whereas the higher error percentages of 24.64, 46.44 and 58.46% for the 20-, 30- and 60-min. to 1-min., conversion were obtained in the Icheon region. The available experimental rainfall data were sampled on equiprobable rain-rate values where the application of these models to experimentally obtained data exhibits a variable error rate. This paper aims to provide a better survey of various conversion methods to model a 1-min. rain rate applicable to the South Korea regions with a suitable contour plot at 0.01% of the time.

      PubDate: 2017-01-22T11:36:37Z
      DOI: 10.1016/j.jastp.2017.01.001
  • Accuracy assessment of the global ionospheric model over the Southern
           Ocean based on dynamic observation
    • Authors: Xiaowen Luo; Huajun Xu; Zishen Li; Tao Zhang; Jinyao Gao; Zhongyan Shen; Chunguo Yang; Wuziyin
      Abstract: Publication date: Available online 5 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Xiaowen Luo, Huajun Xu, Zishen Li, Tao Zhang, Jinyao Gao, Zhongyan Shen, Chunguo Yang, Wuziyin
      The global ionospheric model based on the reference stations of the Global Navigation Satellite System (GNSS) of the International GNSS Services is presently the most commonly used products of the global ionosphere. It is very important to comprehensively analyze and evaluate the accuracy and reliability of the model for the reasonable use of this kind of ionospheric product. In terms of receiver station deployment, this work is different from the traditional performance evaluation of the global ionosphere model based on observation data of ground-based static reference stations. The preliminary evaluation and analysis of the the global ionospheric model was conducted with the dynamic observation data across different latitudes over the southern oceans. The validation results showed that the accuracy of the global ionospheric model over the southern oceans is about 5 TECu, which deviates from the measured ionospheric TEC by about −0.6 TECu.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.017
  • Turbulent processes in Earth's magnetosheath by Cluster mission
    • Authors: L.V. Kozak; A.T.Y. Lui; E.A. Kronberg; A.S. Prokhorenkov
      Abstract: Publication date: Available online 5 January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): L.V. Kozak, A.T.Y. Lui, E.A. Kronberg, A.S. Prokhorenkov
      Methods and approaches which can be used for the analysis of hydrodynamic and magnetohydrodynamic turbulent flows are chosen for this study. It is defined that the best methods for determination of turbulent process types are the methods of statistical physics. Within the statistical approach the fractal analysis (height of the maximum of probability density fluctuations of the studied parameters) and multifractal analysis (study of a power dependence of high order statistical moments and construction of multifractal spectrum) are considered. It is indicated that the statistical analysis of turbulent process properties can be supplemented with spectral studies (wavelet analysis). Physical processes in the transition regions of the magnetosphere: foreshock, shock, post-shock and magnetosheath are investigated using high frequency measurements by Cluster satellites. Extended self-similarity analysis and structure function analysis demonstrate the presence of super-diffusion processes and the highest values of generalized diffusion coefficients observed in post-shock region. It can be noted that different approaches for the analysis of turbulent processes give similar results and indicate the presence of super-diffusion processes in the transition region of the Earth's magnetosphere. This fact must be taken into account when constructing quantitative models of a transfer process. Wavelet analysis shows the presence of cascade and inverse cascade processes in the Earth's magnetosheath. Good agreement with other studies and our new results contribute to improvement of our understanding of turbulence.

      PubDate: 2017-01-06T15:45:09Z
      DOI: 10.1016/j.jastp.2016.12.016
  • A new tool for spatiotemporal pattern decomposition based on empirical
           mode decomposition: A case study of monthly mean precipitation in Taihu
           Lake Basin, China
    • Authors: Shen Chenhua; Yan Yani
      Pages: 10 - 20
      Abstract: Publication date: February 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 154
      Author(s): Shen Chenhua, Yan Yani
      We present a new tool for spatiotemporal pattern decomposition and utilize this new tool to decompose spatiotemporal patterns of monthly mean precipitation from January 1957 to May 2015 in Taihu Lake Basin, China. Our goal is to show that this new tool can mine more hidden information than empirical orthogonal function (EOF). First, based on EOF and empirical mode decomposition (EMD), the time series which is an average over the study region is decomposed into a variety of intrinsic mode functions (IMFs) and a residue by means of EMD. Then, these IMFs are supposed to be explanatory variables and a time series of precipitation in every station is considered as a dependent variable. Next, a linear multivariate regression equation is derived and corresponding coefficients are estimated. These estimated coefficients are physically interpreted as spatial coefficients and their physical meaning is an orthogonal projection between IMF and a precipitation time series in every station. Spatial patterns are presented depending on spatial coefficients. The spatiotemporal patterns include temporal patterns and spatial patterns at various timescales. Temporal pattern is obtained by means of EMD. Based on this temporal pattern, spatial patterns at various timescales will be gotten. The proposed tool has been applied in decomposition of spatiotemporal pattern of monthly mean precipitation in Taihu Lake Basin, China. Since spatial patterns are associated with intrinsic frequency, the new and individual spatial patterns are detected and explained physically. Our analysis shows that this new tool is reliable and applicable for geophysical data in the presence of nonstationarity and long-range correlation and can handle nonstationary spatiotemporal series and has the capacity to extract more hidden time-frequency information on spatiotemporal patterns.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.008
      Issue No: Vol. 154 (2016)
  • Rain attenuation statistics over millimeter wave bands in South Korea
    • Authors: Sujan Shrestha; Dong-You Choi
      Pages: 1 - 10
      Abstract: Publication date: January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 152–153
      Author(s): Sujan Shrestha, Dong-You Choi
      Rain induced degradations are significant for terrestrial microwave links operating at frequencies higher than 10GHz. Paper presents analyses done on rain attenuation and rainfall data for three years between 2013 till 2015, in 3.2km experimental link of 38GHz and 0.1km link at 75GHz. The less link distance is maintained for 75GHz operating frequency in order to have better recording of propagation effect as such attenuation induced by rain. OTT Parsivel is used for collection of rain rate database which show rain rate of about 50mm/h and attenuation values of 20.89 and 28.55dB are obtained at 0.01% of the time for vertical polarization under 38 and 75GHz respectively. Prediction models, namely, ITU-R P. 530-16, Da Silva Mello, Moupfouma, Abdulrahman, Lin and differential equation approach are analyzed. This studies help to identify most suitable rain attenuation model for higher microwave bands. While applying ITU-R P. 530-16, the relative error margin of about 3%, 38% and 42% along with 80, 70, 61% were obtained in 0.1%, 0.01% and 0.001% of the time for vertical polarization under 38 and 75GHz respectively. Interestingly, ITU-R P. 530-16 shows relatively closer estimation to measured rain attenuation at 75GHz with relatively less error probabilities and additionally, Abdulrahman and ITU-R P. 530-16 results in better estimation to the measured rain attenuation at 38GHz link. The performance of prominent rain attenuation models are judged with different error matrices as recommended by ITU-R P. 311-15. Furthermore, the efficacy of frequency scaling technique of rain attenuation between links distribution are also discussed. This study shall be useful for making good considerations in rain attenuation predictions for terrestrial link operating at higher frequencies.

      PubDate: 2016-11-30T09:27:24Z
      DOI: 10.1016/j.jastp.2016.11.004
      Issue No: Vol. 152-153 (2016)
  • A method for detecting equidistant frequencies in the spectrum of a
           wideband signal
    • Authors: A.R. Polyakov
      Pages: 30 - 40
      Abstract: Publication date: January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 152–153
      Author(s): A.R. Polyakov
      Examples are presented of using a signal processing technique that allows equidistant frequencies to be detected in broad-band oscillation spectra. This technique is based on analyzing the amplitude and phase correlation functions (APCF) of the oscillations. Equidistant frequencies can be detected in any broad-band spectrum based on the presence of periodic peaks related to such frequencies in APCF functions. An example of processing 1D resonator oscillations serves to show that the relationship between the eigenfrequencies in the spectrum and the APCF function peaks is similar to that between the optical grating slits and the interference line image on the screen. The proposed signal processing technique allows the difference between two adjacent frequencies of such a "grating" to be measured. The same analogy is true for a 2D resonator. In the latter case, two equidistant eigenfrequency gratings are shown to be present in the spectrum. Each grating corresponds to the eigenfrequencies of a 1D standing wave along each of the coordinates of a 2D resonator. The effect of small non-equidistance of the eigenfrequencies on the distortion and the location of the correlation function peaks is examined. The examples of processing two 1-h intervals of geomagnetic pulsation records are used to demonstrate the applicability of the APCF technique for real recorded magnetospheric oscillations.

      PubDate: 2016-12-07T12:12:48Z
      DOI: 10.1016/j.jastp.2016.11.007
      Issue No: Vol. 152-153 (2016)
  • Modeling of the middle atmosphere response to 27-day solar irradiance
    • Authors: Timofei Sukhodolov; Eugene Rozanov; William T. Ball; Thomas Peter; Werner Schmutz
      Pages: 50 - 61
      Abstract: Publication date: January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 152–153
      Author(s): Timofei Sukhodolov, Eugene Rozanov, William T. Ball, Thomas Peter, Werner Schmutz
      The solar rotational variability (27-day) signal in the Earth's middle atmosphere has been studied for several decades, as it was believed to help in the understanding of the Sun's influence on climate at longer timescales. However, all previous studies have found that this signal is very uncertain, likely due to the influence of the internal variability of the atmosphere. Here, we applied an ensemble modeling approach in order to decrease internal random variations in the modeled time series. Using a chemistry-climate model (CCM), SOCOLv3, we performed two 30-member 3-year long (2003–2005) ensemble runs: with and without a rotational component in input irradiance fluxes. We also performed similar simulations with a 1-D model, in order to demonstrate the system behavior in the absence of any dynamical feedbacks and internal perturbations. For the first time we show a clear connection between the solar rotation and the stratospheric tropical temperature time-series. We show tropical temperature and ozone signal phase lag patterns that are in agreement with those from a 1-D model. Pronounced correlation and signal phase lag patterns allow us to properly estimate ozone and temperature sensitivities to irradiance changes. While ozone sensitivity is found to be in agreement with recent sensitivities reported for the 11-year cycle, temperature sensitivity appears to be at the lowest boundary of previously reported values. Analysis of temperature reanalysis data, separate ensemble members, and modeling results without a rotational component reveals that the atmosphere can produce random internal variations with periods close to 27 days even without solar rotational forcing. These variations are likely related to tropospheric wave-forcing and complicate the extraction of the solar rotational signal from observational time-series of temperature and, to a lesser extent, of ozone. Possible ways of further improving solar rotational signal extraction are discussed.

      PubDate: 2016-12-14T14:09:21Z
      DOI: 10.1016/j.jastp.2016.12.004
      Issue No: Vol. 152-153 (2016)
  • Statistical cloud coverage as determined from sunshine duration: a model
           applicable in daylighting and solar energy forecasting
    • Authors: Ladislav Kómar; Miroslav Kocifaj
      Pages: 1 - 8
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Ladislav Kómar, Miroslav Kocifaj
      A radiative/luminous energy budget is difficult to predict on a daily or hourly base if cloud coverage is obtained by subjective methods in discrete time points. A simple theoretical model that overcomes this shortcoming through interrelation of absolute cloud fraction and sunshine duration is presented. The latter is measured routinely at the meteorological stations worldwide. The model is based on statistical probability of clear line of sight, where Poisson spatial cloud distribution is analyzed for three different cloud shapes. A validation of the model using long-term measurements show a good correlation between experimentally determined and theoretically predicted data. The absolute cloud fraction obtained this way are a base for daylighting and solar energy applications including simulations of luminance/radiance sky distributions under different meteorological conditions. A simple calculation tool is developed and demonstrated on global horizontal illuminance (GHI).

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.011
      Issue No: Vol. 150-151 (2016)
  • Characterization of aerosol events based on the column integrated optical
           aerosol properties and polarimetric measurements
    • Authors: Florian Mandija; Krzysztof Markowicz; Olga Zawadzka
      Pages: 9 - 20
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Florian Mandija, Krzysztof Markowicz, Olga Zawadzka
      Aerosol optical properties are very useful tools for analyzing their radiative effects, which are directly or indirectly related to the global radiation budget. Investigation of column-integrated aerosol optical properties is a worldwide and well-accepted method. The introduction of new methodologies, like those of operation with polarimetric measurements, represent a new challenge to interpret the measurement data and give more detailed information about the aerosol events and their characteristics. Aerosol optical properties during the period June – August 2015 in AERONET Strzyzow station in Poland were analyzed. The aerosol properties like aerosol optical depth, Ångström exponent, fine mode fraction, fine mode contribution on AOD, asymmetry parameter, single scattering angle are analyzed synergistically with the polarimetric measurements of the degree of polarization in different solar zenith and zenith viewing angles at several wavelengths. The overall results show that aerosol events in Strzyzow were characterized mostly by fine mode aerosols. Backward-trajectories suggest that the majority of air masses come from the west. The principal component of the aerosol load was urban/industrial contamination, especially from the inner part of the continent. Additionally, the maximal values of the degree of linear polarization were found to be dependent on the solar zenith and zenith viewing angles and aerosol optical properties like aerosol optical depth and Ångström exponent. These dependencies were further analyzed in a specific case with very high mean values of AOD500 (0.59) and AE440–870 (1.91). The diurnal variations of aerosol optical properties investigated during this special case, suggest that biomass burning products are the main cause of that aerosol load over the stations.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.012
      Issue No: Vol. 150-151 (2016)
  • A scanning Raman lidar for observing the spatio-temporal distribution of
           water vapor
    • Authors: Masanori Yabuki; Makoto Matsuda; Takuji Nakamura; Taiichi Hayashi; Toshitaka Tsuda
      Pages: 21 - 30
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Masanori Yabuki, Makoto Matsuda, Takuji Nakamura, Taiichi Hayashi, Toshitaka Tsuda
      We have constructed a scanning Raman lidar to observe the cross-sectional distribution of the water vapor mixing ratio and aerosols near the Earth's surface, which are difficult to observe when a conventional Raman lidar system is used. The Raman lidar is designed for a nighttime operating system by employing a ultra-violet (UV) laser source and can measure the water vapor mixing ratio at an altitude up to 7km using vertically pointing observations. The scanning mirror system consists of reflective flat mirrors and a rotational stage. By using a program-controlled rotational stage, a vertical scan can be operated with a speed of 1.5°/s. The beam was pointed at 33 angles over range of 0–48° for the elevation angle with a constant step width of 1.5°. The range-height cross sections of the water vapor and aerosol within a 400m range can be obtained for 25min. The lidar signals at each direction were individually smoothed with the moving average to spread proportionally with the distance from the laser-emitting point. The averaged range at a distance of 200m (400m) from the lidar was 30.0m (67.5m) along the lidar signal in a specific direction. The experimental observations using the scanning lidar were conducted at night in the Shigaraki MU radar observatory located on a plateau with undulating topography and surrounded by forests. The root mean square error (RMSE) between the temporal variations of the water vapor mixing ratio by the scanning Raman lidar and by an in-situ weather sensor equipped with a tethered balloon was 0.17g/kg at an altitude of 100m. In cross-sectional measurements taken at altitudes and horizontal distances up to 400m from the observatory, we found that the water vapor mixing ratio above and within the surface layer varied vertically and horizontally. The spatio-temporal variability of water vapor near the surface seemed to be sensitive to topographic variations as well as the wind field and the temperature gradient over the site. From the wide-range cross-sectional observations of the water vapor mixing ratio and the backscatter ratio of aerosols within a 2000m range, we can detect small-scale water vapor structures on a horizontal scale of several hundred meters in the atmospheric boundary layer.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.013
      Issue No: Vol. 150-151 (2016)
  • The solar dimming/brightening effect over the Mediterranean Basin in the
           period 1979–2012
    • Authors: H.D. Kambezidis; D.G. Kaskaoutis; G.K. Kalliampakos; A. Rashki; M. Wild
      Pages: 31 - 46
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): H.D. Kambezidis, D.G. Kaskaoutis, G.K. Kalliampakos, A. Rashki, M. Wild
      Numerous studies have shown that the solar radiation reaching the Earth's surface is subjected to multi-decadal variations with significant spatial and temporal heterogeneities in both magnitude and sign. Although several studies have examined the solar radiation trends over Europe, North America and Asia, the Mediterranean Basin has not been studied extensively. This work investigates the evolution and trends in the surface net short-wave radiation (NSWR, surface solar radiation - reflected) over the Mediterranean Basin during the period 1979–2012 using monthly re-analysis datasets from the Modern Era Retrospective-Analysis for Research and Applications (MERRA) and aims to shed light on the specific role of clouds on the NSWR trends. The solar dimming/brightening phenomenon is temporally and spatially analyzed over the Mediterranean Basin. The spatially-averaged NSWR over the whole Mediterranean Basin was found to increase in MERRA by +0.36Wm−2 per decade, with higher rates over the western Mediterranean (+0.82Wm−2 per decade), and especially during spring (March-April-May; +1.3Wm−2 per decade). However, statistically significant trends in NSWR either for all-sky or clean-sky conditions are observed only in May. The increasing trends in NSWR are mostly associated with decreasing ones in cloud optical depth (COD), especially for the low (<700hPa) clouds. The decreasing COD trends (less opaque clouds and/or decrease in absolute cloudiness) are more pronounced during spring, thus controlling the increasing tendency in NSWR. The NSWR trends for cloudless (clear) skies are influenced by changes in the water-vapor content or even variations in surface albedo to a lesser degree, whereas aerosols are temporally constant in MERRA. The slight negative trend (not statistically significant) in NSWR under clear skies for nearly all months and seasons implies a slight increasing trend in water vapor under a warming and more humid climatic scenario over the Mediterranean.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.006
      Issue No: Vol. 150-151 (2016)
  • Modelling the CO2 atmosphere-ocean flux in the upwelling zones using
           radiative transfer tools
    • Authors: Vladimir F. Krapivin; Costas A. Varotsos
      Pages: 47 - 54
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Vladimir F. Krapivin, Costas A. Varotsos
      An advanced mathematical model of the radiation forcing on the ocean surface is proposed for the assessment of the CO2 fluxes between atmosphere and ocean boundary in the upwelling zones. Two types of the upwelling are considered: coastal and local in the open ocean that are closely associated with changes in solar irradiance. The proposed model takes into account the maximal number of the carbon fluxes in the upwelling ecosystem considering that in the latter the only original source of energy and matter for all forms of life is the energy of the solar radiation. The vertical structure of the upwelling zone is represented by four levels: the upper mixed layer above the thermocline, the intermediate photic layer below the thermocline, the deep ocean and the near-bottom layer. Peruvian upwelling and typical local upwelling of tropical pelagic region are considered as examples for the model calculations.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.015
      Issue No: Vol. 150-151 (2016)
  • Point discharge current measurements beneath dust devils
    • Authors: Ralph D. Lorenz; Lynn D.V. Neakrase; John P. Anderson; R. Giles Harrison; Keri A. Nicoll
      Pages: 55 - 60
      Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151
      Author(s): Ralph D. Lorenz, Lynn D.V. Neakrase, John P. Anderson, R. Giles Harrison, Keri A. Nicoll
      We document for the first time observations of point discharge currents under dust devils using a novel compact sensor deployed in summer 2016 at the USDA-ARS Jornada Experimental Range in New Mexico, USA. A consistent signature is noted in about a dozen events seen over 40 days, with a positive current ramping up towards closest approach, switching to a decaying negative current as the devil recedes. The currents, induced on a small wire about 10cm above the ground, correlate with dust devil intensity (pressure drop) and dust loading, and reached several hundred picoAmps.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.10.017
      Issue No: Vol. 150-151 (2016)
  • Thermospheric density variations following the March 2013 geomagnetic
           storm from GRACE GPS-determined precise orbits
    • Authors: Andres Calabia; Shuanggen Jin
      Abstract: Publication date: Available online 28 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Andres Calabia, Shuanggen Jin
      The thermospheric mass density variations and thermosphere-ionosphere coupling during geomagnetic storms are not clear due to lack of observations and large uncertainty in the models. Although accelerometers on-board Low-Orbit-Earth (LEO) satellites can measure non-gravitational accelerations and derive thermospheric mass density variations with unprecedented details, their measurements are not always available. In order to cover accelerometer data gaps of GRACE, in this paper we estimate thermospheric mass densities from the GPS determined precise orbit ephemeris (POE) of GRACE satellites for the period 2011–2016. Our results show good correlation with accelerometer-based mass densities and a better estimation than the NRLMSISE00 empirical model. Furthermore, we statistically analyze the thermospheric density variations and responses to the March 2013 geomagnetic storm. The results show density variations with good correlations to the Dst, Kp and AE indices during the March 2013 geomagnetic storm. With the increasing resolution and accuracy of precise orbit determination (POD) products and LEO satellites, the straightforward technique of determining non-gravitational accelerations and thermospheric mass densities through numerical differentiation of POD promises potentially good applications for the upper atmosphere research.

      PubDate: 2016-12-28T15:04:05Z
  • Ionospheric response to the 2006 sudden stratospheric warming event over
           the equatorial and low latitudes in the Brazilian sector using GPS
    • Authors: R. de Jesus; I.S. Batista; P.R. Fagundes; K. Venkatesh; A.J. de Abreu
      Abstract: Publication date: Available online 27 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R. de Jesus, I.S. Batista, P.R. Fagundes, K. Venkatesh, A.J. de Abreu
      The main purpose of this paper is to study the response of the ionospheric F-region using GPS-TEC measurements at equatorial and low latitude regions over the Brazilian sector during an sudden stratospheric warming (SSW) event in the year 2006. In this work, we present vertical total electron content (VTEC) and phase fluctuations derived from GPS network in Brazil. The continuous wavelet transform (CWT) was employed to check the periodicities of the ∆VTEC during the SSW event. The results show a strong decrease in VTEC and ∆VTEC values in the afternoon over low latitudes from DOY 05 to 39 (during the SSW event) mainly after the second SSW temperature peak. The ionospheric ∆VTEC pattern over Brazilian sector shows diurnal and semidiurnal oscillations during the 2006 SSW event. In addition, for the first time, variations in ∆VTEC (low latitude stations) with periods of about 02–08day have been reported during an SSW event. Using GPS stations located in the Brazilian sector, it is reported for the first time that equatorial ionospheric irregularities were not suppressed by the SSW event.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.005
  • Assessment of scintillation proxy maps for a scintillation study during
           geomagnetically quiet and disturbed conditions over Uganda
    • Authors: Emirant B. Amabayo; Edward Jurua; Pierre J. Cilliers
      Abstract: Publication date: Available online 27 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Emirant B. Amabayo, Edward Jurua, Pierre J. Cilliers
      The objective of this paper is demonstrate the validity and usefulness of scintillation proxies derived from IGS data, through its comparison with data from dedicated scintillation monitors and its application to GNSS scintillation patterns. The paper presents scintillation patterns developed by using data from the dedicated scintillation monitors of the scintillation network decision aid (SCINDA) network, and proxy maps derived from IGS GPS data for 2011 and 2012 over low latitude stations in Uganda. The amplitude and phase scintillation indicies (S 4 and σ Φ ) were obtained from the Novatel GSV4004B ionospheric scintillation and total electron content (TEC) monitor managed by SCINDA at Makerere (0.340N, 32.570E). The corresponding IGS GPS proxy data were obtained from the receivers at Entebbe (0.040N, 32.440E) and Mbarara (0.600S, 30.740E). The derived amplitude (S 4p) and phase (sDPR) scintillation proxy maps were compared with maps of S 4 and σ Φ during geomagnetic storms (moderate and strong) and geomagnetically quiet conditions. The scintillation patterns using S 4 and σ Φ and their respective proxies revealed similar diurnal and seasonal patterns of strong scintillation occurrence. The peaks of scintillation occurrence with mean values in the range 0.3 < ( S 4 p , sDPR ) ≤ 0.6 were observed during nighttime (17:00–22:00 UT) and in the months of March-April and September-October. The results also indicate that high level scintillations occur during geomagnetically disturbed (moderate and strong) and quiet conditions over the Ugandan region. The results show that SCINDA and IGS based scintillation patterns reveal the same nighttime and seasonal occurrence of irregularities over Uganda irrespective of the geomagnetic conditions. Therefore, the amplitude and phase scintillation proxies presented here can be used to fill gaps in low-latitude data where there are no data available from dedicated scintillation receivers, irrespective of the geomagnetic conditions.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.009
    • Authors: R.G. Ezquer; L.A. Scidá; Y.O. Migoya Orué; G.E. Lescano; K. Alazo-Cuartas; M.A. Cabrera; S.M. Radicella
      Abstract: Publication date: Available online 27 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): R.G. Ezquer, L.A. Scidá, Y.O. Migoya Orué, G.E. Lescano, K. Alazo-Cuartas, M.A. Cabrera, S.M. Radicella
      The performance of NeQuick 2 model in computing the vertical total electron content (VTEC) over a wide region placed at middle latitudes of North America during the deep solar minimum that occurred in 2008 has been checked. The long term relationship between EUV irradiance and F10.7 solar flux has changed markedly during the cycle 23/24 minimum with EUV levels decreasing more than expected from F10.7 proxy. A decrease of ionization in the ionosphere could have occurred. Thus, it could be expected that the models overestimate the value of ionospheric parameters for that deep solar minimum. For this study a high density VTEC data grid that covers the Continental United States (CONUS) has been compared with monthly median maps constructed with NeQuick 2. The results show that NeQuick 2 generally gives good predictions for the region which lies between 35°N to 50°N suggesting that nothing exceptional was happening during the 2008 minimum in terms of VTEC NeQuick 2's predictive capabilities. Taking into account that the modelled value is obtained by integration in height of the electron density profile, NeQuick2 would be assuming an inadequate profile for the few highest deviations observed, between 30°N and 35°N. Overall, the model does not give significant overestimation of VTEC as could be expected.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.014
    • Authors: Laysa Cristina Araujo Resende; Inez Staciarini Batista; Clezio Marcos Denardini; Paulo Prado Batista; Alexander José Carrasco; Vânia de Fátima Andrioli; Juliano Moro
      Abstract: Publication date: Available online 26 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Laysa Cristina Araujo Resende, Inez Staciarini Batista, Clezio Marcos Denardini, Paulo Prado Batista, Alexander José Carrasco, Vânia de Fátima Andrioli, Juliano Moro
      This work presents new results about simulations of blanketing sporadic E-layers, Esb, using a modified version of a theoretical model for the E region (MIRE) for a Brazilian region: Cachoeira Paulista, a low latitude station. MIRE computes the densities of the metallic ions (Fe+ and Mg+) and of the main molecular ions (NO+, O2 +, N2 +) by solving the continuity and momentum equations for each one of them. Additionally, this model includes the physics of Es layer development driven by tidal winds. In this study, we extend MIRE adding a novel neutral wind model derived from the all-sky meteor radar measurements, which provides more trustworthy results related to the Es layer formation in the Brazilian sector. Afterwards, this new model is validated comparing the computed electron density for the Es layer with the electron density obtained using the blanketing frequency parameter (fbEs) deduced from ionograms in the analyzed region. The results show that the values computed by the extended MIRE are in good agreement with the observational data for the Es layers formed by the wind shear mechanism. Therefore, the extended MIRE presented in this work is the only available model that allows simulating Esb layers with a much higher confidence level for the low-latitude in the Brazilian sector.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.012
  • The Role of Charged Ice Hydrometeors in Lightning Initiation
    • Authors: L.P. Babich; E.I. Bochkov; T. Neubert
      Abstract: Publication date: Available online 24 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): L.P. Babich, E.I. Bochkov, T. Neubert
      In connection with the lightning initiation problem, we consider positive streamer formation around charged, needle-shaped ice hydrometeors in an external electric field. We present results of numerical simulations of the streamer discharges that include the ice dielectric polarization and conductivity, and determine the external field intensity, at which stable streamer development is possible for different hydrometeor sizes and charge magnitudes. We find that the required charge is within the range of measured precipitation charges while the required external field is higher than observed in thunderclouds. We conclude, therefore, that a second mechanism for amplification of thundercloud fields is required for the streamer inception.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.010
  • Comparison of mesospheric winds from a high-altitude meteorological
           analysis system and meteor radar observations during the boreal winters of
           2009–2010 and 2012–2013
    • Authors: J. McCormack; K. Hoppel; D. Kuhl; R. de Wit; G. Stober; P. Espy; N. Baker; P. Brown; D. Fritts; C. Jacobi; D. Janches; N. Mitchell; B. Ruston; S. Swadley; K. Viner; T. Whitcomb; R. Hibbins
      Abstract: Publication date: Available online 24 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): J. McCormack, K. Hoppel, D. Kuhl, R. de Wit, G. Stober, P. Espy, N. Baker, P. Brown, D. Fritts, C. Jacobi, D. Janches, N. Mitchell, B. Ruston, S. Swadley, K. Viner, T. Whitcomb, R. Hibbins
      We present a study of horizontal winds in the mesosphere and lower thermosphere (MLT) during the boreal winters of 2009–2010 and 2012–2013 produced with a new high-altitude numerical weather prediction (NWP) system. This system is based on a modified version of the Navy Global Environmental Model (NAVGEM) with an extended vertical domain up to ∼116km altitude coupled with a hybrid four-dimensional variational (4DVAR) data assimilation system that assimilates both standard operational meteorological observations in the troposphere and satellite-based observations of temperature, ozone and water vapor in the stratosphere and mesosphere. NAVGEM-based MLT analyzed winds are validated using independent meteor radar wind observations from nine different sites ranging from 69°N–67°S latitude. Time-averaged NAVGEM zonal and meridional wind profiles between 75–95km altitude show good qualitative and quantitative agreement with corresponding meteor radar wind profiles. Wavelet analysis finds that the 3-hourly NAVGEM and 1-hourly radar winds both exhibit semi-diurnal, diurnal, and quasi-diurnal variations whose vertical profiles of amplitude and phase are also in good agreement. Wavelet analysis also reveals common time-frequency behavior in both NAVGEM and radar winds throughout the Northern extratropics around the times of major stratospheric sudden warmings (SSWs) in January 2010 and January 2013, with a reduction in semi-diurnal amplitudes beginning around the time of a mesospheric wind reversal at 60°N that precedes the SSW, followed by an amplification of semi-diurnal amplitudes that peaks 10–14 days following the onset of the mesospheric wind reversal. The initial results presented in this study demonstrate that the wind analyses produced by the high-altitude NAVGEM system accurately capture key features in the observed MLT winds during these two boreal winter periods.

      PubDate: 2016-12-28T15:04:05Z
      DOI: 10.1016/j.jastp.2016.12.007
  • IFC-Ed. board
    • Abstract: Publication date: January 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 152–153

      PubDate: 2016-12-21T14:33:31Z
  • Case study of convective instability observed in airglow images over the
           Northeast of Brazil
    • Authors: A.J.A. Carvalho; I. Paulino; A.F. Medeiros; L.M. Lima; R.A. Buriti; A.R. Paulino; C.M. Wrasse; H. Takahashi
      Abstract: Publication date: Available online 21 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.J.A. Carvalho, I. Paulino, A.F. Medeiros, L.M. Lima, R.A. Buriti, A.R. Paulino, C.M. Wrasse, H. Takahashi
      An intense activity of ripples during the nighttime was observed in airglow images over São João do Cariri (36.5 o W, 7.4 o S) on 10 October 2004 which lasted for two hours. Those ripples appeared simultaneously with the crossing of a mesospheric front and medium scale gravity waves. The ripples occurred ahead of the mesospheric front and their phase front were almost parallel to the phase of the mesospheric front and were almost perpendicular to the phase front of the gravity wave. Using wind measurements from a meteor radar located at São João do Cariri and simultaneous vertical temperature profiles from the TIMED/SABER satellite, on the night of the events and within the imager field of view, the atmospheric background environment in the mesosphere and lower thermosphere (MLT) was investigated in order to understand the instability process that caused the appearance of the ripples. Dynamic and convective instabilities have been pointed out as responsible for creation of ripples in the MLT. The observed ripples were advected by the neutral wind, they occurred into a region with negative lapse rate of the potential temperature and the Richardson number was negative as well. According to these characteristics, the ripple structures could be generated in the MLT region due to the predominance of convective instability.

      PubDate: 2016-12-21T14:33:31Z
      DOI: 10.1016/j.jastp.2016.12.003
  • An Overturning-like Thermospheric Na Layer and its Relevance to
           Ionospheric Field Aligned Irregularity and Sporadic E
    • Authors: Xianghui Xue; Guozhu Li; Xiankang Dou; Xinan Yue; Guotao Yang; Jinsong Chen; Tingdi Chen; Baiqi Ning; Jihong Wang; Guojun Wang; Weixing Wan
      Abstract: Publication date: Available online 19 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Xianghui Xue, Guozhu Li, Xiankang Dou, Xinan Yue, Guotao Yang, Jinsong Chen, Tingdi Chen, Baiqi Ning, Jihong Wang, Guojun Wang, Weixing Wan
      We report an overturning-like structure of the thermospheric sodium layer (TSL) in the altitude region of ∼100–120km observed by a sodium lidar at Haikou (20.0°N), China, on July 29, 2012. The overturning-like sodium layer was first seen as upwelling from the top of the sodium layer (∼102km) to an altitude of ∼118km from 14:55–15:50 UT and then descending gradually from its apex with a speed of 3.5km/hr. The ionospheric observations from the COSMIC radio occultation and three ionosondes exhibited abrupt perturbations in the radio occultation (RO) SNR profiles and spread Es in the ionograms, respectively, indicating the existence of complex Es around Haikou. On the other hand, VHF radars located at Sanya (18.4°N, 220km away from Haikou) and Fuke (19.5°N, 130km away from Haikou) both recorded strong E region field-aligned irregularity (FAI) echoes altitude-extended structure covering altitudes of 100–140km, which are well correlated with the overturning-like structure of the thermospheric sodium layer. The good agreement between occurrence time of sodium layer (and FAI) structure and of complex Es could indicate a close correlation between them. One possibility is that the chemical reaction in the course of the complex Es (with altitude-deformed structure) could produce sufficient sodium atoms and thus lead to the formation of sodium layer upwelling structure. Correspondingly, FAI altitude-extended structure could be generated through the gradient drift instability in the altitude-extend (deformed) Es which provide plasma density gradients to support the instability development.

      PubDate: 2016-12-21T14:33:31Z
      DOI: 10.1016/j.jastp.2016.12.006
  • Use of multivariate relevance vector machines in forecasting multiple
           geomagnetic indices
    • Authors: T. Andriyas; S. Andriyas
      Abstract: Publication date: Available online 11 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): T. Andriyas, S. Andriyas
      The forecasting ability of Multivariate Relevance Vector Machines (MVRVM), used previously to generate forecasts for the Dst index, is extended to forecast the Dst, AL, and PC indices during the years 1975–2007. Such learning machines are used in forecasting because of their robustness, efficiency, and sparseness. The MVRVM model was trained on solar wind and geomagnetic activity data sampled every hour with activity periods of various intensities, durations, and features. It was found that during the training phase, for a given error threshold, 14.60% of the training data was needed to explain the features of the data. The trained model was then tested on 177 different storm intervals, at various levels of geomagnetic activity, to generate simultaneous forecasts of the three indices at a lead time of one hour (1-h). The focus of the modeling was to assess the forecasts during main storm (MS) time periods when the indices show enhanced activity above quiet time values. The forecasts obtained by the MVRVM model reported in this paper returned a MS time average prediction efficiency, PE ¯ of 82.42%, 84.40%, and 76.00% and RMSE ¯ of 13.70nT, 97.00nT, and −0.77mV/m, for the Dst, AL, and PC indices, respectively. The qualitative numbers indicated that the model underestimated the peak amplitude of the indices during the geomagnetic activity, but the peaks were forecasted on time by the model, on average. The forecasting results indicate a robust model generalization and the MVRVM's ability to learn the input-output relationship through a sparse model framework. A qualitative comparison with the previous univariate RVM forecast of Dst indicates that the model goodness of fit numbers improved in the present study.

      PubDate: 2016-12-14T14:09:21Z
      DOI: 10.1016/j.jastp.2016.11.002
  • Prediction of global solar radiation and comparison with satellite data
    • Authors: Kadir Bakirci
      Abstract: Publication date: Available online 5 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Kadir Bakirci
      Data on solar radiation at a related location is very necessary for many solar applications. In the present study, the models are derived to forecast the daily global solar radiation on horizontal plane for the Eastern Anatolia Region (EAR) of Turkey, covering thirteen provinces. The measured data on horizontal plane for the period of 1991–2005 are analyzed. The comparisons of calculated and measured values have been carried out with various statistical test methods. These statistical test methods are the mean bias error (MBE), the main percentage error (MPE), the root mean square error (RMSE) and t-statistic (t-stat). In addition, the comparisons of the solar radiation values of the National Aeronautics and Space Administration - Surface meteorology and Solar Energy (NASA-SSE) and calculated from the Model 3 with the higher determination coefficient is performed.

      PubDate: 2016-12-07T12:12:48Z
  • Source spectra of the gravity waves obtained from momentum flux and
           kinetic energy over Indian region: Comparison between observations and
           model results
    • Authors: M. Pramitha; M. Venkat Ratnam; B.V. Krishna Murthy; S. Vijaya Bhaskar Rao
      Abstract: Publication date: Available online 3 December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): M. Pramitha, M. Venkat Ratnam, B.V. Krishna Murthy, S. Vijaya Bhaskar Rao
      Using 8 years (May 2006 to March 2014) of high resolution and high accuracy GPS radiosonde observations available from a tropical station Gadanki (13.5°N, 79.2°E), India, we have investigated the climatology of gravity wave energy and zonal momentum fluxes in the lower stratosphere. We also obtained best fit spectrum model for the gravity waves (GWs) for this tropical station. In general, strong annual variation in the energy and momentum flux with maximum during Indian summer monsoon is observed in the lower stratospheric region (18–25km). By considering different source spectra, we have applied Gravitywave Regional or Global RAy Tracer (GROGRAT) model run on monthly basis using the source spectrum values at different altitudes on the ERA-Interim background fields to obtain the kinetic energy and zonal momentum fluxes for each of the spectra considered. These simulated fluxes are compared with the observed fluxes to arrive at the best fit spectrum model. It is found that the spectrum which represents the convection transient mountain mechanism that is purely anti-symmetric and anisotropic in nature is the best fit model for Gadanki location. This information would be useful in parameterization of the GWs in numerical models over Indian region.

      PubDate: 2016-12-07T12:12:48Z
      DOI: 10.1016/j.jastp.2016.12.001
  • IFC-Ed. board
    • Abstract: Publication date: December 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volumes 150–151

      PubDate: 2016-11-23T06:38:05Z
  • Seasonal, inter-annual and solar cycle variability of the quasi two day
           wave in the low-latitude mesosphere and lower thermosphere
    • Authors: N. Venkateswara Rao; M. Venkat Ratnam; C. Vedavathi; T. Tsuda; B.V. Krishna Murthy; S. Sathishkumar; S. Gurubaran; K. Kishore Kumar; K.V. Subrahmanyam; S. Vijaya Bhaskara Rao
      Abstract: Publication date: Available online 22 November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): N. Venkateswara Rao, M. Venkat Ratnam, C. Vedavathi, T. Tsuda, B.V. Krishna Murthy, S. Sathishkumar, S. Gurubaran, K. Kishore Kumar, K.V. Subrahmanyam, S. Vijaya Bhaskara Rao
      We analyzed 17 years (1993–2009) of horizontal winds measured by the medium frequency (MF) radar located at Tirunelveli (8.7°N, 77.8°E) and 10 years (2005–2014) of horizontal winds measured by a meteor radar located at Thumba (8.5°N, 77°E) to examine the seasonal, inter-annual, and solar cycle variability of the Quasi-Two Day Wave (QTDW) in the mesosphere and lower thermosphere region. These two radars are nearly co-located, but differ in their measurement technique. Comparison of the estimated QTDW amplitudes by the two radars shows that the amplitudes are larger in the meteor radar than those in the MF radar. The difference between the amplitudes is larger in May in the zonal component and in April and September in the meridional one. Furthermore, the differences are larger in the meridional component. The QTDWs in both the radars show a strong semi-annual oscillation (SAO). In addition, the meridional QTDW amplitudes of both the MF and meteor radars show a distinct enhancement in the month of October. While the whole spectra of QTDWs contribute to the SAO amplitudes, only 45–50 h waves contribute to the October enhancement. The amplitudes of the QTDWs, in general, show large inter-annual variability. The QTDW amplitudes from both the radars show modulation at period of quasi-biennial oscillation. The QTDWs of the MF radar show a small negative correlation with solar activity while those of meteor radar do not show any correlation. The above aspects are discussed in the light of current understanding of the QTDWs.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.11.005
  • Spatiotemporal assessment of CO2 emissions and its satellite remote
           sensing over Pakistan and neighboring regions
    • Authors: Zia ul-Haq; Salman Tariq; Muhammad Ali
      Abstract: Publication date: Available online 9 November 2016
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Zia ul-Haq, Salman Tariq, Muhammad Ali
      For the first time, anthropogenic CO2 emissions and spatiotemporal variability of mid-tropospheric CO2 has been discussed using EDGAR database and Atmospheric Infrared Sounder (AIRS) onboard Aqua satellite observations. The EDGAR data indicate an increase of 147% in anthropogenic CO2 emissions from 66101 to 163737 Gg for Pakistan during the period of 1990−2008. Dera Ghazi Khan (Pakistan) is found with the highest increase of 260% of anthropogenic CO2 emissions followed by Delhi (India) 153%, Karachi (Pakistan) 66% and Lahore (Pakistan) 59% whereas a decreasing trend of −53% is observed for Kabul (Afghanistan) during 1990−2008. Industrial activities, road transportation, open field crop-waste burning, and energy production have been identified as major anthropogenic emission sources of CO2 in the studied region. AIRS CO2 retrievals over Pakistan and adjoining areas of India and Afghanistan show an averaged CO2 to be 383±5 ppm with a positive trend of 5.05% during December 2002 to February 2012. An elevated value of CO2 has been observed over northern mountainous and high human settlement regions. The seasonal analysis shows a spring maximum 385±5 ppm with a secondary peak in late autumn, and the highest increasing trend of 5.5% associated with winter. May and August showed maximum and minimum mean monthly values of 385±5 ppm and 382±5 ppm respectively. HYSPLIT trajectories of air masses movement have been drawn to track CO2 transport.

      PubDate: 2016-11-23T06:38:05Z
      DOI: 10.1016/j.jastp.2016.11.001
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