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  Subjects -> METEOROLOGY (Total: 88 journals)
Showing 1 - 36 of 36 Journals sorted alphabetically
Acta Meteorologica Sinica     Hybrid Journal   (Followers: 3)
Advances in Atmospheric Sciences     Hybrid Journal   (Followers: 34)
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: 15)
American Journal of Climate Change     Open Access   (Followers: 15)
Atmósfera     Open Access   (Followers: 2)
Atmosphere     Open Access   (Followers: 21)
Atmosphere-Ocean     Full-text available via subscription   (Followers: 12)
Atmospheric and Oceanic Science Letters     Open Access   (Followers: 2)
Atmospheric Chemistry and Physics (ACP)     Open Access   (Followers: 31)
Atmospheric Chemistry and Physics Discussions (ACPD)     Open Access   (Followers: 11)
Atmospheric Research     Hybrid Journal   (Followers: 57)
Atmospheric Science Letters     Open Access   (Followers: 29)
Boundary-Layer Meteorology     Hybrid Journal   (Followers: 24)
Bulletin of the American Meteorological Society     Open Access   (Followers: 33)
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: 30)
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   (Followers: 1)
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: 3)
Dynamics of Atmospheres and Oceans     Hybrid Journal   (Followers: 11)
Earth Perspectives - Transdisciplinarity Enabled     Open Access  
Energy & Environment     Hybrid Journal   (Followers: 18)
Environmental and Climate Technologies     Open Access   (Followers: 3)
Global Meteorology     Open Access   (Followers: 6)
International Journal of Biometeorology     Hybrid Journal   (Followers: 1)
International Journal of Climate Change Strategies and Management     Hybrid Journal   (Followers: 14)
International Journal of Climatology     Hybrid Journal   (Followers: 25)
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: 31)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 136)
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: 15)
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: 21)
Journal of the Atmospheric Sciences     Full-text available via subscription   (Followers: 69)
Journal of the Meteorological Society of Japan     Partially Free   (Followers: 3)
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: 10)
Monthly Weather Review     Full-text available via subscription   (Followers: 27)
Nature Climate Change     Full-text available via subscription   (Followers: 66)
Nature Reports Climate Change     Full-text available via subscription   (Followers: 27)
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: 17)
Studia Geophysica et Geodaetica     Hybrid Journal   (Followers: 1)
Tellus A     Open Access   (Followers: 23)
Tellus B     Open Access   (Followers: 21)
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: 22)
Theoretical and Applied Climatology     Hybrid Journal   (Followers: 8)
Urban Climate     Hybrid Journal  
Weather     Hybrid Journal   (Followers: 14)
Weather and Climate Extremes     Open Access   (Followers: 8)
Weather and Forecasting     Full-text available via subscription   (Followers: 16)
Weatherwise     Hybrid Journal   (Followers: 2)
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]   [136 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1364-6826
   Published by Elsevier Homepage  [3043 journals]
  • Experimental investigation of turbulent transport of momentum and heat in
           the atmospheric surface layer
    • Authors: Guowen Han; X.J. Zheng; Tianli Bo
      Pages: 18 - 28
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Guowen Han, X.J. Zheng, Tianli Bo
      In our study, turbulent transport of momentum and heat is investigated in the neutral and unstable atmospheric surface layer (ASL) over the edge of a desert. Our results reveal that with the increase of wind speed the transport efficiencies for momentum and heat increased, furthermore, transport efficiency of momentum increases faster than that of heat. In addition, the method of quadrant analysis and turbulent events were used to analyze the moment flux and heat flux. Experimental results show that the influence of wind speed on moment flux and heat flux can be quite different, which maybe has a great impact on the turbulent transport of momentum and heat in ASL.

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.017
      Issue No: Vol. 164 (2017)
       
  • Stationary depletions in thermospheric atomic oxygen concentration and
           mass density observed with WINDII, GUVI, GOCE and simulated by NRLMSISE-00
           
    • Authors: Gordon G. Shepherd; Young-Min Cho
      Pages: 29 - 38
      Abstract: Publication date: November 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 164
      Author(s): Gordon G. Shepherd, Young-Min Cho
      Observations of thermospheric atomic oxygen concentrations [O] by the Wind Imaging Interferometer (WINDII) and the Global Ultra Violet Imager (GUVI) derived from daytime airglow observations clearly show a persistent depletion in [O], for WINDII by about 63% below background, in the southern mid-latitudes, near 40° S latitude and 100° longitude. It appears less strongly in the northern hemisphere at about 250° longitude and is not evident in local winter for either hemisphere. The same feature appears strongly in the NRLMSISE-00 empirical model. Mass density observations by the Gravity field and steady-state Ocean Circulation Explorer (GOCE) available at dawn and dusk local times at times show similar depletions with a smaller reduction of about 20% but do not consistently agree with those of [O]. It has been shown elsewhere that Total Electron Content (TEC) observations are strongly related to the column ratio ΣO/N2. These observations clearly show the Weddell Sea Anomaly (WSA) enhancement as well as the [O] depletion at a similar latitude; these are oppositely phased and 180° apart in longitude, suggesting a common source.

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.016
      Issue No: Vol. 164 (2017)
       
  • Analysis of ionospheric disturbances associated with powerful cyclones in
           East Asia and North America
    • Authors: Wang Li; Jianping Yue; Yang Yang; Zhen Li; Jinyun Guo; Yi Pan; Kefei Zhang
      Pages: 43 - 54
      Abstract: Publication date: August 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 161
      Author(s): Wang Li, Jianping Yue, Yang Yang, Zhen Li, Jinyun Guo, Yi Pan, Kefei Zhang
      East Asia and North America are the regions most heavily affected by powerful cyclones. In this paper we investigate the morphological characteristics of ionospheric disturbances induced by cyclones in different continents. The global ionosphere map supplied by the Center for Orbit Determination in Europe (CODE), International Reference Ionosphere Model (IRI) 2012, and Wallops Island ionosonde station data are used to analyse the ionospheric variations during powerful typhoons/hurricanes in East Asia and North America, respectively. After eliminating the ionospheric anomalies due to the solar-terrestrial environment, the total electron content (TEC) time series over the point with maximum wind speed is detected by the sliding interquartile range method. The results indicate that significant ionospheric disturbances are observed during powerful tropical cyclones in East Asia and North America, respectively, and that all the ionospheric anomalies are positive. In addition, the extent and magnitude of travelling ionospheric disturbances are associated with the category of tropical cyclone, and the extent of TEC anomalies in longitude is more pronounced than that in latitude. Furthermore, the maximum ionospheric anomaly does not coincide with the eye of the storm, but appears in the region adjacent to the centre. This implies that ionospheric disturbances at the edges of cyclones are larger than those in the eye of the winds. The phenomenon may be associated with the gravity waves which are generated by strong convective cells that occur in the spiral arms of tropical cyclones. This comprehensive analysis suggests that the presence of powerful typhoons/hurricanes may be a possible source mechanism for ionospheric anomalies.

      PubDate: 2017-07-02T17:30:36Z
      DOI: 10.1016/j.jastp.2017.06.012
      Issue No: Vol. 161 (2017)
       
  • Transport of water vapour over the Tibetan Plateau as inferred from the
           model simulations
    • Authors: S. Jain; S.C. Kar
      Pages: 64 - 75
      Abstract: Publication date: August 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 161
      Author(s): S. Jain, S.C. Kar
      This paper discusses the transport of water vapour in the tropopause region over the Tibetan Plateau, where high water vapour mixing ratio is observed during the Northern Hemisphere (NH) summer-monsoon period. The Weather Research and Forecasting (WRF) model has been used to study the two contrasting cases i.e. when water vapour is high and low at 100 hPa (close to tropopause). The composite distribution of water vapour shows two key results (a) the water vapour appears be transported to the Tibetan plateau region from the extra-tropics under the influence of stronger northwesterly winds and (b) the vertical water vapour flux is relatively higher over the Tibetan Plateau region during the period when water vapour amount at this level is higher. This suggests that in addition to the horizontal transport from the extra-tropics, the local convection occurring over the Tibetan Plateau also contributes to the increase in the water vapour over this region. The differences in the circulation during high and low water vapour cases suggest that a cyclonic circulation difference over the central Indian region limit the transport of water vapour from the Bay of Bengal to the Tibetan Plateau region.

      PubDate: 2017-07-02T17:30:36Z
      DOI: 10.1016/j.jastp.2017.06.016
      Issue No: Vol. 161 (2017)
       
  • Distribution of cloudiness and categorization of rainfall types based on
           INSAT IR brightness temperatures over Indian subcontinent and adjoining
           oceanic region during south west monsoon season
    • Authors: P. Vijaykumar; S. Abhilash; K.R. Santhosh; B.E. Mapes; C. Suvarchal Kumar; I-Kuan Hu
      Pages: 76 - 82
      Abstract: Publication date: Available online 28 June 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): P. Vijaykumar, S. Abhilash, K.R. Santhosh, B.E. Mapes, C. Suvarchal Kumar, Ikuan
      To understand the relationship between rain intensity and brightness temperature, Cloud Top Brightness Temperature (CTBT) derived from INSAT three hourly IR radiances having a resolution of 0.25 × 0.25 deg. is compared with corresponding TRMM PR Rain Rate (TPRR) for the Indian Summer Monsoon periods of 2007 and 2008. BT value ranges corresponding to events of various intensities of rain in the four major raining sub regions identified in Indian subcontinent and surrounding ocean are compared. The sub regions identified are (1) Head Bay of Bengal, (2) Central Indian land region, (3) Eastern Arabians Sea and West coast of India and (4) South West Indian Ocean. BT values are grouped into classes of 10°K bin width between 270 and 180°K. Number of occurrence of three classes of rain (light - >4.5 mm, moderate - 4.5–9 mm and heavy 9.0 mm and above cumulative for 3 h) belonging in each BT classes is calculated. It is observed that the three classes of rainfall have distinct characteristic BT ranges. This rain category - BT range relation has geographical (spatial) variability. This could be due to the variation in types of clouds prevalent in the sub regions considered. The present study improves the understanding of the structure and spatial variability of cloudiness and rainfall in and around Indian region during monsoon season.

      PubDate: 2017-07-02T17:30:36Z
      DOI: 10.1016/j.jastp.2017.06.017
      Issue No: Vol. 161 (2017)
       
  • A new retrieval method for the ice water content of cirrus using data from
           the CloudSat and CALIPSO
    • Authors: Honglin Pan; Lingbing Bu; K. Raghavendra Kumar; Haiyang Gao; Xingyou Huang; Wentao Zhang
      Pages: 134 - 142
      Abstract: Publication date: August 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 161
      Author(s): Honglin Pan, Lingbing Bu, K. Raghavendra Kumar, Haiyang Gao, Xingyou Huang, Wentao Zhang
      The CloudSat and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) are the members of satellite observation system of A-train to achieve the quasi-synchronization observation on the same orbit. With the help of active (CALIOP and CPR) and passive payloads from these two satellites, respectively, unprecedented detailed information of microphysical properties of ice cloud can be retrieved. The ice water content (IWC) is regarded as one of the most important microphysical characteristics of cirrus for its prominent role in cloud radiative forcing. In this paper, we proposed a new joint (Combination) retrieval method using the full advantages of different well established retrieval methods, namely the LIDAR method (for the region Lidar-only), the MWCR method (for the region Radar-only), and Wang method (for the region Lidar-Radar) proposed by Wang et al. (2002). In retrieval of cirrus IWC, empirical formulas of the exponential type were used for both thinner cirrus (detected by Lidar-only), thicker cirrus (detected by radar-only), and the part of cirrus detected by both, respectively. In the present study, the comparison of various methods verified that our proposed new joint method is more comprehensive, rational and reliable. Further, the retrieval information of cirrus is complete and accurate for the region that Lidar cannot penetrate and Radar is insensitive. On the whole, the retrieval results of IWC showed certain differences retrieved from the joint method, Ca&Cl, and ICARE which can be interpreted from the different hypothesis of microphysical characteristics and parameters used in the retrieval method. In addition, our joint method only uses the extinction coefficient and the radar reflectivity factor to calculate the IWC, which is simpler and reduces to some extent the accumulative error. In future studies, we will not only compare the value of IWC but also explore the detailed macrophysical and microphysical characteristics of cirrus.
      Graphical abstract image

      PubDate: 2017-07-12T04:49:43Z
      DOI: 10.1016/j.jastp.2017.07.001
      Issue No: Vol. 161 (2017)
       
  • Modeling study of the ionospheric responses to the quasi-biennial
           oscillations of the sun and stratosphere
    • Authors: Jack C. Wang; Rong Tsai-Lin; Loren C. Chang; Qian Wu; Charles C.H. Lin; Jia Yue
      Abstract: Publication date: Available online 3 August 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jack C. Wang, Rong Tsai-Lin, Loren C. Chang, Qian Wu, Charles C.H. Lin, Jia Yue
      The Quasi-biennial Oscillation (QBO) is a persistent oscillation in the zonal mean zonal winds of the low latitude middle atmosphere that is driven by breaking planetary and gravity waves with a period near two years. The atmospheric tides that dominate the dynamics of the mesosphere and lower thermosphere region (MLT, between heights of 70–120 km) are excited in the troposphere and stratosphere, and propagate through QBO-modulated zonal mean zonal wind fields. This allows the MLT tidal response to also be modulated by the QBO, with implications for ionospheric/thermospheric variability. Interannual oscillations in solar radiation can also directly drive the variations in the ionosphere with similar periodicities through the photoionization. Many studies have observed the connection between the solar activity and QBO signal in ionospheric features such as total electron content (TEC). In this research, we develop an empirical model to isolate stratospheric QBO-related tidal variability in the MLT diurnal and semidiurnal tides using values from assimilated TIMED satellite data. Migrating tidal fields corresponding to stratospheric QBO eastward and westward phases, as well as with the quasi-biennial variations in solar activity isolated by the Multi-dimensional Ensemble Empirical Mode Decomposition (MEEMD) analysis from Hilbert-Huang Transform (HHT), are then used to drive the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). The numerical experiment results indicate that the ionospheric QBO is mainly driven by the solar quasi-biennial variations during the solar maximum, since the solar quasi-biennial variation amplitude is directly proportionate to the solar cycle. The ionospheric QBO in the model is sensitive to both the stratospheric QBO and solar quasi-biennial variations during the solar minimum, with solar effects still playing a stronger role.

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.024
       
  • IFC-Ed. board
    • Abstract: Publication date: August 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 161


      PubDate: 2017-08-03T07:02:04Z
       
  • Numerical study of heating the upper atmosphere by acoustic-gravity waves
           from a local source on the Earth's surface and influence of this heating
           on the wave propagation conditions
    • Authors: I.V. Karpov; S.P. Kshevetskii
      Abstract: Publication date: Available online 31 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): I.V. Karpov, S.P. Kshevetskii
      The propagation of acoustic-gravity waves (AGW) from a source on the Earth's surface to the upper atmosphere is investigated with methods of mathematical modeling. The applied non-linear model of wave propagation in the atmosphere is based on numerical integration of a complete set of two-dimensional hydrodynamic equations. The source on the Earth's surface generates waves with frequencies near to the Brunt-Vaisala frequency. The results of simulation have revealed that some region of heating the atmosphere by propagated upward and dissipated AGWs arises above the source at altitudes nearby of 200 km. The horizontal scale of this heated region is about 1000 km in the case of the source that radiates AGWs during approximately 1 h. The appearing of the heated region has changed the conditions of AGW propagation in the atmosphere. When the heated region in the upper atmosphere has been formed, further a waveguide regime of propagation of waves with the periods shorter the Brunt-Vaisala period is realized. The upper boundary of the wave-guide coincides with the arisen heated region in the upper atmosphere. The considered mechanism of formation of large-scale disturbances in the upper atmosphere may be useful for explanation of connections of processes in the upper and lower atmospheric layers.

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.019
       
  • Characteristics of convective structures of sodium layer in lower
           thermosphere (105–120 km) at Haikou (19.99°N, 110.34°E), China
    • Authors: Jing Jiao; Guotao Yang; Jihong Wang; Tiemin Zhang; Hongyan Peng; Yuchang Xun; Zhengkuan Liu; Chi Wang
      Abstract: Publication date: Available online 29 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Jing Jiao, Guotao Yang, Jihong Wang, Tiemin Zhang, Hongyan Peng, Yuchang Xun, Zhengkuan Liu, Chi Wang
      The atmospheric sodium layer normally occurs in the mesopause (80–105 km) region, but rarely in the lower thermosphere region (>105 km) at low latitude. We observed a kind of peculiar sodium layer in lower thermosphere at Haikou (19.99.00°N, 110.34°E)—the thermospheric convective sodium layer (TCSL) in a lidargram. The TCSL's sodium density unstably developed over time and appeared as several discontinuous convective shapes vertically. It is the first time convective sodium layer observed in the lower thermosphere region (105–120 km). Based on Haikou lidar data, we obtained 14 TCSL events during 180 nights from March 2010 to August 2012. Most of the apogees of the TCSL events are higher than 108 km. A TCSL event lasts several hours and is composed of several convective structures, with each veitical shape lasting ∼5–30 min. All TCSL events occurred during spring and summer, and generally appear near midnight (22:00–00:00 LT). The TCSL has potential regional feature and appears to be related to the thermospheric sporadic E (Es) layers, winds, and field-aligned ionospheric irregularities (FAI).

      PubDate: 2017-08-03T07:02:04Z
      DOI: 10.1016/j.jastp.2017.07.020
       
  • New global electron density observations from GPS-RO in the D- and
           E-Region ionosphere
    • Authors: Dong
      Abstract: Publication date: Available online 27 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Dong L. Wu
      A novel retrieval technique is developed for electron density (N e ) in the D- and E-region (80–120 km) using the high-quality 50-Hz GPS radio occultation (GPS-RO) phase measurements. The new algorithm assumes a slow, linear variation in the F-region background when the GPS-RO passes through the D- and E-region, and extracts the N e profiles at 80–130 km from the phase advance signal caused by N e . Unlike the conventional Abel function, the new approach produces a sharp N e weighting function in the lower ionosphere, and the N e retrievals are in good agreement with the IRI (International Reference Ionosphere) model in terms of monthly maps, zonal means and diurnal variations. The daytime GPS-RO N e profiles can be well characterized by the α-Chapman function of three parameters (N mE , h mE and H), showing that the bottom of E-region is deepening and sharpening towards the summer pole. At high latitudes the monthly GPS-RO N e maps at 80–120 km reveal clear enhancement in the auroral zones, more prominent at night, as a result of energetic electron precipitation (EEP) from the outer radiation belt. The D-/E-region auroral N e is strongly correlated with K p on a daily basis. The new N e data allow further comprehensive analyses of the sporadic E (E s ) phenomena in connection with the background N e in the E-region. The layered (2–10 km) and fluctuated (<2 km) E s components, namely N e_Layer than N e_Pert , are extracted with respect to the background N e_Region on a profile-by-profile basis. The N e_Layer component has a strong but highly-refined peak at ∼105 km, with an amplitude smaller than N e_Region approximately by an order of magnitude. The N e_Pert component, which was studied extensively in the past, is ∼2 orders of magnitude weaker than N e_Layer . Both N e_Layer and N e_Pert are subject to significant diurnal and semidiurnal variations, showing downward progression with local time in amplitude. The 11-year solar cycle dominates the N e interannual variations, showing larger N e_Region and N e_Layer but smaller N e_Pert amplitudes in the solar maximum years. Enhanced N e profiles are often observed in the polar winter, showing good correlation with solar proton events (SPEs) and geomagnetic activity. The new methodology offers great potential for retrieving low N e in the D-region, where radio propagation and communication blackouts can occur due to enhanced ionization. For space weather applications it is recommended for GPS-RO operations to raise the top of high-rate data acquisition to ∼140 km in the future.

      PubDate: 2017-08-03T07:02:04Z
       
  • Fine spatial evolution of leaders and M-components in rocket-triggered
           lightning observed with a broadband interferometer
    • Authors: Mingli Chen; Yanchi Shen; Yaping Du; Wansheng Dong
      Abstract: Publication date: Available online 22 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Mingli Chen, Yanchi Shen, Yaping Du, Wansheng Dong
      Based on measurements of VHF radiation sources and VLF electric fields with a broadband interferometer system, the spatial evolution of leader processes and K-breakdowns and M-components involved in a classically-triggered negative lightning discharge have been analyzed. While a normal classically-triggered negative discharge usually starts with a positive leader initiates from the tip of the ascending triggering-wire and moves upward, there was no such an initial upward positive leader (UPL) being observed for the present discharge, probably due to low resolution and sensitivity of the measurements. Instead, there was a downward negative leader (PDL) at the preliminary stage of the discharge being observed, followed by a 173-ms-long lasting M-component-wise process and two leader/return-stroke processes. The PDL was most likely a leader process along the channel trace possibly built by the undetected UPL, as its speed which ranged from 3.7 × 106 m/s to 0.3 × 106 m/s is similar to that of a dart leader in literature. The long lasting M-component-wise process consisted of a slow negative-going change stage (Ma), followed by a fast negative-going change stage (Mb) and then a slow positive-going change stage (Mc). Ma was found to be intra-cloud negative breakdowns moving towards overhead position of the PDL trace. Mb would be considered as a common M-component (channel brightening), which starts with a K breakdown in cloud (Mb1) moving horizontally towards overhead position of the previous PDL, followed by an event (Mb2) moving up from ground to cloud along PDL trace. As Mb2 reaching the cloud, more new K breakdowns (Mc) appeared in cloud around extremities of the pre-built channels by Ma and Mb. The leader preceding the first return stroke (L1) started inside the cloud and propagated downward to the triggering-wire trace, but with a different channel to that of PDL. As the leader touched the triggering wire trace, it appeared to propagate upward along the same channel of PDL. The upward portion of L1 might be interpreted as a reflection of L1 at top of the triggering-wire trace towards the PDL trace due to the difference in conductivity and potential between the PDL trace, the triggering wire trace and the L1 channel, which was optically invisible but bright in VHF. The speed of the downward portion of L1 decreased from 2.32 to 0.32 × 106 m/s as it descended, while that of the upward portion of L1 increased from 0.85 to 2.7 × 106 m/s as it ascended. The leader preceding the second return stroke (L2) behaved similarly to L1 but with higher speeds.

      PubDate: 2017-07-24T05:50:47Z
      DOI: 10.1016/j.jastp.2017.07.008
       
  • The zonal-mean and regional tropospheric pressure responses to changes in
           ionospheric potential
    • Authors: Limin Zhou; Brian Tinsley; Lin Wang; Gary Burns
      Abstract: Publication date: Available online 21 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Limin Zhou, Brian Tinsley, Lin Wang, Gary Burns
      Global reanalysis data reveal daily surface pressure responses to changes in the global ionospheric potential in both polar and sub-polar regions. We use 21 years of data to show that the pressure response to externally-induced ionospheric potential changes, that are due to the interplanetary magnetic field east-west (IMF B y ) component, are present in two separate decadal intervals, and follow the opposite ionospheric potential changes in the Arctic and Antarctic for a given B y . We use the 4 years of available data to show that the pressure responses to changes in internally generated ionospheric potential, that are caused by low-latitude thunderstorms and highly electrified clouds, agree in sign and sensitivity with those externally generated. We have determined that the daily varying pressure responses are stronger in local winter and spring. The pressure responses at polar latitudes are predominantly over the Antarctic and Greenland ice caps, and those at sub-polar latitudes are of opposite sign, mainly over oceans. A lead-lag analysis confirms that the responses maximize within two days of the ionospheric potential input. Regions of surface pressure fluctuating by about 4 hPa in winter are found with ionospheric potential changes of about 40 kV. The consistent pressure response to the independent external and internal inputs strongly supports the reality of a cloud microphysical mechanism affected by the global electric circuit. A speculative mechanism involves the ionosphere-earth current density J z , which produces space charge at cloud boundaries and electrically charged droplets and aerosol particles. Ultrafine aerosol particles, under the action of electro-anti-scavenging, are enabled to grow to condensation nuclei size, affecting cloud microphysics and cloud opacity and surface pressure on time scales of hours.

      PubDate: 2017-07-24T05:50:47Z
      DOI: 10.1016/j.jastp.2017.07.010
       
  • Temperature properties in the tropical tropopause layer and their
           correlations with Outgoing Longwave Radiation: FORMOSAT-3/COSMIC
           observations
    • Authors: Kaiti Wang; Yi-chao Wu; Jia-Ting Lin; Pei-Hua Tan
      Abstract: Publication date: Available online 21 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Kaiti Wang, Yi-chao Wu, Jia-Ting Lin, Pei-Hua Tan
      The properties of temperature at the level of lapse rate minimum (LRM) in the tropical tropopause layer between 20°S and 20°N are investigated using 3-year radio occultation observations based on the FORMOSAT-3/COSMIC mission from November of 2006 to October of 2009. The correlations between this LRM temperature and Outgoing Longwave Radiation (OLR) are analyzed by 5° × 5° grids in longitude and latitude. Two primary regions, one from 60°E to 180°E and the other from 90°W to 30°E, are found to have higher correlations and can be associated with regions of lower OLR values. The patterns of this spatial distributions of regions with higher correlations begin to change more obviously when the altitude ascends to the level of Cold Point Tropopause (CPT). This correlation at the LRM altitude in annual and seasonal scales also shows spatial distributions associated with OLR intensities. The altitudinal dependence of the correlations between temperature and OLR is further analyzed based on grids of high correlations with significance at LRM altitude, for the two primary regions. The results show that for the different time scales in this analysis (3-year, annual, and seasonal), the correlations all gradually decrease above the LRM levels but maintain a significant level to as high as 2.5–3.5 km. Below the LRM level, the correlation decreases with a slower rate as the altitude descends and still keeps significant at the deep 5 km level. These suggest that the vertical temperature profiles could be affected by the convection mechanism for a wide range of altitudes in the troposphere even above LRM altitude. Applying the same analysis on one complete La Niña event during the survey period also reveals similar features.

      PubDate: 2017-07-24T05:50:47Z
      DOI: 10.1016/j.jastp.2017.07.012
       
  • Solar wind dependence of electric conductances and currents in the auroral
           zone
    • Authors: V. Sergeev; N. Stepanov; Y. Ogawa; S. Käki; K. Kauristie
      Abstract: Publication date: Available online 20 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): V. Sergeev, N. Stepanov, Y. Ogawa, S. Käki, K. Kauristie
      Based on 20 years-long data base of EISCAT incoherent scatter radar and IMAGE magnetometer observations in Scandinavia, we investigate statistically the ionospheric conductance variations in the dark nightside auroral zone. We focus on the relationship of precipitation-caused conductances with the variations of local equivalent current and global AL index, as well as on their dependence on the solar wind (SW) parameters. In terms of paired correlation, the main SW drivers for AL index and for the Pedersen and Hall conductances ( Σ P and Σ H ) are the SW merging electric field (characterized, e.g., with the Kan-Lee function, E k l ) and the solar wind velocity V s w . The relative importance of these SW drivers varies. Whereas E k l is the main driver of AL index, the role of V s w increases for the conductances so that it outruns the E k l as the main driver for the Hall conductance. Quantitatively this dependence is represented as Σ H = ( 7.7 * V + 1.75 * V 2 ) + ( 5.7 * E − 0.86 * E 2 ) − 6.1 Siemens, where E and V are E k l and V s w normalized with < E k l > = 0.79 mV/m and < V s w > = 429 km/s. The strongest influence of V s w is, however, observed for the Hall-to-Pedersen conductance ratio R H P = Σ H / Σ P , indicating solar wind velocity control of the electron acceleration. Physically the energization is a major factor which contributes to the large conductance values. On the nightside, local equivalent currents are significantly controlled by the local Hall conductance (CC = 0.78) and most of the equivalent current increase during active periods is due to the conductivity change. In that sense the AL index variations during active times are controlled by the Hall conductance variations which, to a large extent, are controlled by the processes of magnetospheric electron acceleration.

      PubDate: 2017-07-24T05:50:47Z
      DOI: 10.1016/j.jastp.2017.07.006
       
  • PIC simulations of wave-particle interactions with an initial electron
           velocity distribution from a kinetic ring current model
    • Authors: Yiqun Yu; Gian Luca Delzanno; Vania Jordanova; Ivy Bo Peng; Stefano Markidis
      Abstract: Publication date: Available online 15 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Yiqun Yu, Gian Luca Delzanno, Vania Jordanova, Ivy Bo Peng, Stefano Markidis
      Whistler wave-particle interactions play an important role in the Earth inner magnetospheric dynamics and have been the subject of numerous investigations. By running a global kinetic ring current model (RAM-SCB) in a storm event occurred on Oct 23–24 2002, we obtain the ring current electron distribution at a selected location at MLT of 9 and L of 6 where the electron distribution is composed of a warm population in the form of a partial ring in the velocity space (with energy around 15 keV) in addition to a cool population with a Maxwellian-like distribution. The warm population is likely from the injected plasma sheet electrons during substorm injections that supply fresh source to the inner magnetosphere. These electron distributions are then used as input in an implicit particle-in-cell code (iPIC3D) to study whistler-wave generation and the subsequent wave-particle interactions. We find that whistler waves are excited and propagate in the quasi-parallel direction along the background magnetic field. Several different wave modes are instantaneously generated with different growth rates and frequencies. The wave mode at the maximum growth rate has a frequency around 0.62 ω c e , which corresponds to a parallel resonant energy of 2.5 keV. Linear theory analysis of wave growth is in excellent agreement with the simulation results. These waves grow initially due to the injected warm electrons and are later damped due to cyclotron absorption by electrons whose energy is close to the resonant energy and can effectively attenuate waves. The warm electron population overall experiences net energy loss and anisotropy drop while moving along the diffusion surfaces towards regions of lower phase space density, while the cool electron population undergoes heating when the waves grow, suggesting the cross-population interactions.

      PubDate: 2017-07-24T05:50:47Z
      DOI: 10.1016/j.jastp.2017.07.004
       
  • The fate of meteoric metals in ice particles: Effects of sublimation and
           energetic particle bombardment
    • Authors: T.P. Mangan; V.L. Frankland; B.J. Murray; J.M.C. Plane
      Abstract: Publication date: Available online 8 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): T.P. Mangan, V.L. Frankland, B.J. Murray, J.M.C. Plane
      The uptake and potential reactivity of metal atoms on water ice can be an important process in planetary atmospheres and on icy bodies in the interplanetary and interstellar medium. For instance, metal atom uptake affects the gas-phase chemistry of the Earth's mesosphere, and has been proposed to influence the agglomeration of matter into planets in protoplanetary disks. In this study the fate of Mg and K atoms, incorporated into water-ice films prepared under ultra-high vacuum conditions at temperatures of 110–140 K, was investigated. Temperature-programmed desorption experiments reveal that Mg- and K-containing species do not co-desorb when the ice sublimates, demonstrating that uptake on ice particles causes irreversible removal of the metals from the gas phase. This implies that uptake on ice particles in terrestrial polar mesospheric clouds accelerates the formation of large meteoric smoke particles (≥1 nm radius above 80 km) following sublimation of the ice. Energetic sputtering of metal-dosed ice layers by 500 eV Ar+ and Kr+ ions shows that whereas K reacts on (or within) the ice surface to form KOH, adsorbed Mg atoms are chemically inert. These experimental results are consistent with electronic structure calculations of the metals bound to an ice surface, where theoretical adsorption energies on ice are calculated to be −68 kJ mol−1 for K, −91 kJ mol−1 for Mg, and −306 kJ mol−1 for Fe. K can also insert into a surface H2O to produce KOH and a dangling H atom, in a reaction that is slightly exothermic.

      PubDate: 2017-07-12T04:49:43Z
      DOI: 10.1016/j.jastp.2017.07.002
       
  • Day-night changes in the altitude distribution, physical properties and
           radiative impact of low-altitude clouds over the stratocumulus-dominated
           subtropical oceans
    • Authors: Ashok Kumar Gupta; K. Rajeev; S. Sijikumar
      Abstract: Publication date: Available online 1 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Ashok Kumar Gupta, K. Rajeev, S. Sijikumar
      Properties of low-altitude clouds, their radiative impact and day-night changes over the subtropical oceans of prominent stratocumulus occurrence (the Northeast and the Southeast Pacific, the Southeast Atlantic, and the South Indian Ocean) are investigated using multi-year (2006–2010) CloudSat, CALIPSO and radiative flux observations. In all these regions, the occurrence, thickness and longwave radiative impact of clouds are enhanced during the nighttime, while the altitude of peak cloud occurrence (960–1200 m) remains steady. The observed features provide evidence for the physical mechanisms proposed earlier for the coupling between marine boundary layer and low-level clouds and their day-night variations over these regions.

      PubDate: 2017-07-02T17:30:36Z
      DOI: 10.1016/j.jastp.2017.06.021
       
  • Recent developments in the understanding of equatorial ionization anomaly:
           A review
    • Authors: N. Balan; J. Souza; G.J. Bailey
      Abstract: Publication date: Available online 1 July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): N. Balan, J. Souza, G.J. Bailey
      A brief review of the recent developments in the understanding of the equatorial plasma fountain (EPF) and equatorial ionization anomaly (EIA) under quiet and active conditions is presented. It is clarified that (1) the EPF is not upward ExB plasma drift at the equator followed by downward plasma diffusion, but it is field perpendicular ExB plasma drift and field-aligned plasma diffusion acting together all along the field lines at all altitudes and plasma flowing in the direction of the resultant. (2) The EIA is formed not from the accumulation of plasma at the crests but mainly from the removal of plasma from around the equator by the upward ExB drift with small accumulations when the crests are within approximately ±20° magnetic latitude. The accumulations reduce with increasing latitude and become zero by approximately ±25°. (3) An asymmetric neutral wind makes EPF and EIA asymmetric with stronger fountain and stronger crest usually occurring in opposite hemispheres especially at equinoxes when winter anomaly is absent. (4) During the early stages of daytime main phase of major geomagnetic storms, the plasma fountain becomes a super fountain and the EIA becomes strong not due to the eastward prompt penetration electric field (PPEF) alone but due to the combined effect of eastward PPEF and storm-time equatorward winds (SEW). (5) During the later stages of the storms when EIA gets inhibited a peak sometimes occurs around the equator not due to westward electric fields but mainly due to the convergence of plasma from both hemispheres due to SEW.

      PubDate: 2017-07-02T17:30:36Z
      DOI: 10.1016/j.jastp.2017.06.020
       
  • Study of auroral ionosphere using percolation theory and fractal geometry
    • Authors: A.A. Chernyshov; B.V. Kozelov; M.M. Mogilevsky
      Abstract: Publication date: Available online 27 June 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A.A. Chernyshov, B.V. Kozelov, M.M. Mogilevsky
      In this work, values of the fractal dimension and the connectivity index characterizing the structure of Hall conductivities on the night side of the auroral ionosphere are derived in general form. Restrictions imposed on fractal structure of the ionospheric conductivity are analyzed in terms of the percolation of the ionospheric Hall currents. It is shown that the structure of ionospheric Hall conductivities can be described as asymptotically path-connected fractal. This result is supported by analysis of typical structure observed in auroral electron precipitation which are also the main source of ionization on the night side of the ionosphere. It is demonstrated that crossing the precipitation region in the direction perpendicular to the multiple arcs system, one should observe the structure of the precipitation which looks like a generalized Cantor set.

      PubDate: 2017-07-02T17:30:36Z
      DOI: 10.1016/j.jastp.2017.06.013
       
  • Ten-year climatology of potassium number density at 54° N,
           12° E
    • Authors: J. Lautenbach; J. Höffner; F.-J. Lübken; M. Kopp; M. Gerding
      Abstract: Publication date: Available online 23 June 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): J. Lautenbach, J. Höffner, F.-J. Lübken, M. Kopp, M. Gerding
      In the years from 2002 to 2012 potassium densities observations were performed in the mesopause region at Kühlungsborn using a potassium Doppler lidar. The 10-year diurnal data set comprises 5090 h of potassium number densities at 741 days with 25.2% under full daylight conditions. Potassium number densities show a clear semi-annual variation with two broad maxima reoccurring every year. The first maximum occurs in summer and lasts for about 4 months (May–August) with number densities up to 60 atoms/cc. The second maximum is observed from early December to late February with densities up to 30 atoms/cc. Both the peak density and the column density are higher at solstices than at equinoxes. The large data set shows little variation of the mean layer over the 10 years.

      PubDate: 2017-07-02T17:30:36Z
      DOI: 10.1016/j.jastp.2017.06.010
       
  • The influence of tidal winds in the formation of blanketing sporadic
           e-layer over equatorial Brazilian region
    • Authors: Laysa Cristina Araujo Resende; Inez Staciarini Batista; Clezio Marcos Denardini; Paulo Prado Batista; Alexander José Carrasco; Vânia Fátima Andrioli; Juliano Moro
      Abstract: Publication date: Available online 21 June 2017
      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 Fátima Andrioli, Juliano Moro
      This work analysis the blanketing sporadic layers (Esb) behavior over São Luís, Brazil (2° 31′ S, 44° 16′ W, dip: −4.80) which is classified as a transition region between equatorial and low-latitude. Hence, some peculiarities can appear as Esb occurrence instead of the common Esq, which is a non-blanketing irregularity layer. The analysis presented here was obtained using a modified version of a theoretical model for the E region (MIRE), which computes the densities of the metallic ions (Fe+ and Mg+) and the densities of the main molecular ions (NO+, O2 +, N2 +) by solving the continuity and momentum equations for each one of them. In that model, the Es layer physics driven by both diurnal and semidiurnal tidal winds are taken into account and it was extended in height coverage by adding a novel neutral wind model derived from the all-sky meteor radar measurements. Thus, we provide more trustworthy results related to the Es layer formation in the equatorial region. We verified the contribution of each tidal wind component to the Esb layer formation in this equatorial region. Additionally, we compared the Es layer electron density computed by MIRE with the data obtained by using the blanketing frequency parameter (fbEs) deduced from ionograms. The results show that the diurnal component of the tidal wind is more important in the Esb layer formation whereas the semidiurnal component has a little contribution in our simulations. Finally, it was verified that the modified MIRE presented here can be used to study the Esb layers occurrence over the equatorial region in the Brazilian sector.

      PubDate: 2017-07-02T17:30:36Z
      DOI: 10.1016/j.jastp.2017.06.009
       
  • IFC-Ed. board
    • Abstract: Publication date: July 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics, Volume 160


      PubDate: 2017-06-21T16:19:21Z
       
  • Determination of effective droplet radius and optical depth of liquid
           water clouds over a tropical site in northern Thailand using passive
           microwave soundings, aircraft measurements and spectral irradiance data
    • Authors: P. Nimnuan; S. Janjai; M. Nunez; N. Pratummasoot; S. Buntoung; D. Charuchittipan; T. Chanyatham; P. Chantraket; N. Tantiplubthong
      Abstract: Publication date: Available online 6 June 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): P. Nimnuan, S. Janjai, M. Nunez, N. Pratummasoot, S. Buntoung, D. Charuchittipan, T. Chanyatham, P. Chantraket, N. Tantiplubthong
      This paper presents an algorithm for deriving the effective droplet radius and optical depth of liquid water clouds using ground-based measurements, aircraft observations and an adiabatic model of cloud liquid water. The algorithm derives cloud effective radius and cloud optical depth over a tropical site at Omkoi (17.80°N, 98.43°E), Thailand. Monthly averages of cloud optical depth are highest in April (54.5), which is the month with the lowest average cloud effective radius (4.2 μm), both occurring before the start of the rainy season and at the end of the high contamination period. By contrast, the monsoon period extending from May to October brings higher cloud effective radius and lower cloud optical depth to the region on average. At the diurnal scale there is a gradual increase in average cloud optical depth and decrease in cloud effective radius as the day progresses.

      PubDate: 2017-06-11T16:00:27Z
      DOI: 10.1016/j.jastp.2017.06.002
       
  • Signature of the quasi-27-day oscillation in the MLT and its relation with
           solar irradiance and convection
    • Authors: A. Guharay; P.P. Batista; R.A. Buriti; N.J. Schuch
      Abstract: Publication date: Available online 3 June 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): A. Guharay, P.P. Batista, R.A. Buriti, N.J. Schuch
      Intermittent occurrence of the quasi-27-day oscillation is observed in the mesosphere and lower thermosphere (MLT) zonal wind in the long term database over three southern hemispheric Brazilian locations, i.e. Sao Joao do Cariri (7.4°S, 36.5°W), Cachoeira Paulista (22.7°S, 45°W) and Santa Maria (29.7°S, 53.7°W). The oscillation shows a peak amplitude of ∼15 m/s in the lower MLT. To determine the plausible sources of the quasi-27-day oscillation, the variation of the solar Ly-α flux and outgoing longwave radiation (proxy for convection) have been looked into. The oscillation shows considerable consistency with the solar UV flux implying potential solar influence on excitation. The oscillation in the MLT also exhibits good correlation with the outgoing longwave radiation (a proxy of convection) at Cachoeira Paulista indicating plausible influence of lower atmospheric convective activity. Non-concurrent occurrence of the oscillation among the observational stations indicates potential role of local geophysical conditions. The zonal background wind in the MLT might cause dissipation of the upward propagating waves (modulated by 27-day oscillation) and hence imprint the lower atmospheric 27-day signature in the MLT.

      PubDate: 2017-06-06T15:10:54Z
      DOI: 10.1016/j.jastp.2017.06.001
       
  • Spectral characteristics of ionospheric scintillations of UHF radiosignal
           near magnetic zenith
    • Authors: Roman Vasilyev; Maria Globa Dmitry Kushnarev Andrey Medvedev Konstantin Ratovsky
      Abstract: Publication date: Available online 30 May 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Roman Vasilyev, Maria Globa, Dmitry Kushnarev, Andrey Medvedev, Konstantin Ratovsky
      We present the results of observing the Cygnus-A radio source scintillation in the Earth's ionosphere under quiet and disturbed geomagnetic conditions by using the Irkutsk incoherent scattering radar (IISR). The scintillation method applied for ionosphere testing at IISR confidently determines the Fresnel frequency and power cutoff, the spectral characteristics usually related to the velocities and spatial spectra of ionospheric plasma irregularities. We also use the IGFR magnetic field model to show the relation between the shape of discrete radio source scintillation spectra and the direction to the radio source with respect to the geomagnetic field. The S4 index increase within the magnetic zenith is observed to be conditioned by the scintillation spectrum widening. We also evaluate the zonal velocity of observed ionospheric irregularities as ∼10 m/sec assuming the irregularity height to be equal to the F2-layer maximum height in the ionosphere.

      PubDate: 2017-06-02T14:40:25Z
       
  • Evidence of MLT propagation of the plasmapause inferred from THEMIS data
    • Authors: Mario Bandić; Giuli Verbanac; Viviane Pierrard; Junghee Cho
      Abstract: Publication date: Available online 17 May 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Mario Bandić, Giuli Verbanac, Viviane Pierrard, Junghee Cho
      The cross-correlation analysis is applied to the comprehensive database of THEMIS plasmapause crossings (6840 L PP s) and both solar wind parameters and geomagnetic indices (thereafter L PP indicators). We estimate MLTs of the plasmapause formation and further monitor the motion of the new plasmapause at high MLT resolution. Our results show that plasmapause is firstly formed within 23–07 MLT and then propagates around the Earth with the velocity estimated to amounts for 1.10 and 0.45 of the corotation velocity in sectors 07–15 MLT and 15–23 MLT, respectively. Two branches within 23–07 MLT are identified, one at low time lags (T lag s) and second at high T lag s which we relate to the formation of the new plasmapause and to the propagation of the plasmapause formed one MLT-cycle before. This study can be used to improve the current understanding of the plasmapause formation and propagation.

      PubDate: 2017-05-23T04:28:22Z
      DOI: 10.1016/j.jastp.2017.05.005
       
  • Performance of the Angstrom-Prescott Model (A-P) and SVM and ANN
           Techniques to estimate the daily Global Solar Irradiation in
           Botucatu/SP/Brazil
    • Authors: Maurício Bruno Prado da Silva; João Francisco Escobedo; Cícero Manoel dos Santos; Taiza Juliana Rossi; Sílvia Helena Modenese Gorla da Silva
      Abstract: Publication date: Available online 10 May 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Maurício Bruno Prado da Silva, João Francisco Escobedo, Cícero Manoel dos Santos, Taiza Juliana Rossi, Sílvia Helena Modenese Gorla da Silva
      This study describes the comparative study of different methods for estimating daily global solar irradiation (HG): Angstrom-Prescott (A-P) model and two Machine Learning techniques (ML) - Support Vector Machine (SVM) and Artificial Neural Network (ANN). The HG database was measured from 1996 to 2011 in Botucatu/SP/Brazil. Different combinations of input variables were adopted. Statistical indicatives MBE, RMSE, d Willmott, r and R2 obtained in the validation of A-P and SVM and ANN models showed that: SVM technique has better performance than A-P and ANN models in estimating HG. The A-P model has better performance than ANN in estimating HG.

      PubDate: 2017-05-13T03:49:18Z
      DOI: 10.1016/j.jastp.2017.04.001
       
  • Modulations of solar activity on El Niño Modoki and possible
           mechanisms
    • Authors: Wenjuan Huo; Ziniu Xiao
      Abstract: Publication date: Available online 10 May 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Wenjuan Huo, Ziniu Xiao
      This paper uses the sunspot number (SSN) index and the El Niño modoki index (EMI) to examine the possible modulation of El Niño Modoki events by variations in solar activity. A significant positive correlation was found between SSN and EMI with a lag of two years, and both SSN and EMI have an obvious period of about 11–12 years. The evolution of El Niño Modoki events was investigated using composite analysis. There was a clear evolution of El Niño Modoki events in the three years after the solar peak year. An ocean mixed layer heat budget diagnostic method is used to investigate the contributor to the anomalous patterns in the three years after the solar peak. The atmosphere radiation fluxes are confirmed as the major contributor to the warming response in the central tropical Pacific. Two possible mechanisms are proposed, one is the direct mechanism that the solar radiation warms up the tropical pacific with a geographical difference, due to the cloud distribution. The warming response in the central Pacific is amplified by the coupled positive feedback between the ocean and atmosphere with 1–2 years lag. Another possible way can be described as follows: the solar heating effect propagating from the upper atmosphere modulates the strength and variation of atmospheric anomaly at high and mid-latitudes in the northern hemisphere winter, which results in an anomalous subtropical cyclone over the northeastern Pacific in the winter seasons following the solar peak years. The anomalous cyclone reduces the cloud cover over the northeastern Pacific and enhances the local input of solar radiation. As a result, a positive sea surface temperature (SST) anomaly occurs over the northeastern Pacific and extends towards the central tropical Pacific along the path of anomalous southwesterly winds, which may trigger an El Niño Modoki event in the following years.

      PubDate: 2017-05-13T03:49:18Z
      DOI: 10.1016/j.jastp.2017.05.008
       
  • Variability of OH(3-1) and OH(6-2) emission altitude and volume emission
           rate from 2003 to 2011
    • Authors: Georg Teiser; Christian von Savigny
      Abstract: Publication date: Available online 26 April 2017
      Source:Journal of Atmospheric and Solar-Terrestrial Physics
      Author(s): Georg Teiser, Christian von Savigny
      In this study we report on variability in emission rate and centroid emission altitude of the OH(3-1) and OH(6-2) Meinel bands in the terrestrial nightglow based on spaceborne nightglow measurements with the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) instrument on the Envisat satellite. The SCIAMACHY observations cover the time period from August 2002 to April 2012 and the nighttime observations used in this study are performed at 10:00p.m. local solar time. Characterizing variability in OH emission altitude – particularly potential long-term variations – is important for an appropriate interpretation of ground-based OH rotational temperature measurements, because simultaneous observations of the vertical OH volume emission rate profile are usually not available for these measurements. OH emission altitude and vertically integrated emission rate time series with daily resolution for the OH(3-1) band and monthly resolution for the OH(6-2) band were analyzed using a standard multilinear regression approach allowing for seasonal variations, QBO-effects (Quasi-Biennial Oscillation), solar cycle (SC) variability and a linear long-term trend. The analysis focuses on low latitudes, where SCIAMACHY nighttime observations are available all year. The dominant sources of variability for both OH emission rate and altitude are the semi-annual and annual variations, with emission rate and altitude being highly anti-correlated. There is some evidence for a 11-year solar cycle signature in the vertically integrated emission rate and in the centroid emission altitude of both the OH(3-1) and OH(6-2) bands.

      PubDate: 2017-05-02T03:06:31Z
      DOI: 10.1016/j.jastp.2017.04.010
       
 
 
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