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Journal of Atmospheric and Solar-Terrestrial Physics
Journal Prestige (SJR): 0.696
Citation Impact (citeScore): 2
Number of Followers: 177  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1364-6826
Published by Elsevier Homepage  [3177 journals]
  • Multiple attractors and periodicity on the Vallis model for El Niño/La
           Niña-Southern oscillation model
    • Abstract: Publication date: Available online 21 November 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): J.F. Gómez-AguilarAbstractIn this paper, we obtain multiple attractors and periodicity using differential and integral operators with power-law and Mittag-Leffler law for the coupled dynamical El Niño/La Niña-Southern oscillation model and the continuous-time Vallis model for El Niño. Also, we consider the extension of these models considering a stochastic approach where the given parameters are converted to normal distributions. Additionally, we consider for both models novel differential and integral operators with fractional order and fractal dimension. These novel operators predict chaotic behaviors involving the fractal derivative in convolution with power-law and the Mittag-Leffler function, also, these operators can capture self-similarities for both chaotic attractors. We have presented the conditions of existence of uniquely exact solutions of the system using the fixed-point theorem approach. Each model is solved numerical via the Adams-Bashforth-Moulton, Adams-Moulton and the Atangana-Toufik schemes. We presented numerical simulations for different values of fractional order to show the applicability and computational efficiency of these methods. The results obtained presents more information that were not revealed in the models with local derivative.
  • A case study of isolated auroral spots based on DMSP data
    • Abstract: Publication date: Available online 21 November 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Su Zhou, Yuqing Chen, Jin ZhangAbstractThis study employed ultraviolet images and particle data to investigate isolated auroral spots away from the Earth’s auroral oval. Data from SSUSI (Special Sensor Ultraviolet Spectrographic Imager) and SSJ (Special Sensor J) mounted on the DMSP (Defence Meteorological Satellite Program) spacecraft were examined. The isolated auroral spots were observed by DMSP F16/SSUSI and F17/SSUSI on 29 May 2010 during the recovery phase of a moderate geomagnetic storm with a minimum SYM-H index of -70 nT. The auroral spots were observed between 18:00-21:00 MLT and corotated with the Earth, but stayed almost at the same magnetic latitude (MLAT) of -60°. It is found that the isolated auroral spots were produced mainly by energetic ring current ions at energies above ∼10 keV. The enhancement in the electron flux with energy below ∼200 eV was also observed for the isolated auroral spots. The MLAT of the electron flux was nearly 2°higher than that for the precipitating ions.
  • Possible influence of the tropospheric polar vortex on the Barents Sea ice
           extent in winter
    • Abstract: Publication date: Available online 18 November 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Ekaterina SavelievaabstractThe Arctic seas are mainly located inside the polar vortex under conditions of low temperature. Sea ice extent in these seas in the winter-spring period reaches maximum values with negligible interannual changes. The exception is the Barents Sea, where interannual variability of sea ice extent increases from December to February. In winter, the vortex edge is often located near the Barents Sea, which leads to an increase in surface temperature and a decrease in sea ice extent. We show that the Barents Sea ice extent in winter can be determined by the shape and location of the tropospheric polar vortex.
  • Validation of Physical Radiative Transfer Equation-Based Land Surface
           Temperature Using Landsat 8 Satellite Imagery and SURFRAD In-situ
    • Abstract: Publication date: Available online 30 October 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Aliihsan SekertekinAbstractLand Surface Temperature (LST) is a key criterion in the physics of the earth surface that controls the interactions between the land and atmosphere. The objective of this study is to evaluate the performance of physics-based Radiative Transfer Equation (RTE) method on LST retrieval using Landsat 8 satellite imagery and simultaneous in-situ LST data. In order to validate the satellite-based LST, in-situ LST measurements were obtained from Surface Radiation Budget Network (SURFRAD) stations simultaneous with satellite data acquisitions. In the study, four SURFRAD stations (BND, FPK, TBL and GWN) and five images for each SURFRAD station, totally twenty cloud-free images, were used for RTE-based LST validation. RTE method uses the atmospheric parameters acquired from radiosounding data simultaneous with satellite pass; however, these parameters were retrieved from NASA’s atmospheric correction parameter calculator since radiosounding data are not available every time. Thus, this situation is another contribution of this study. As a result of the validation process of all data, the statistical measures, namely, R2, RMSE, MAE and RSR were calculated as 0.96, 3.12 K, 2.30 K and 0.33, respectively. However, the accuracy of RTE method on LST retrieval increased (R2=0.97, RMSE=2.17 K, MAE=1.44 K and RSR=0.25) after removing TBL station from the analysis, since LST differences in this station were high for all scenes. RSR (ranging from 0 to high positive vlues) is an important measure for model evaluation, and the lower RSR value means high performance of the model. The obtained results revealed that physics-based RTE method is an effective and practical way for LST retrieval from Landsat 8 data despite using interpolated atmospheric parameters.
  • Optical characteristics of branched downward positive leader associated
           with recoil leader activity
    • Abstract: Publication date: Available online 23 October 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): X. Wang, X. Zhao, H. Cai, G. Liu, M. Liao, L. QuAbstractThe propagation characteristics of one downward positive leader with mainly four forked branches in one natural positive lightning have been investigated based on high-speed video observations. One branch develops horizontally; one branch travels downward eventually reaching the ground, and two faint branches are reilluminated by recoil leader (RL) activity multiple times. Four branches share some interesting correlation during their development. At the early phase, the horizontal branch and descending branch are inactive or propagate slowly when RL activity is more active. After the appearance of RL activity each time, the horizontal branch propagates slightly faster. After that, the two luminous branches propagate more actively and faster, while RL process becomes diminished and suppressed. Both downward and horizontal branches speed up as the downward one is approaching the ground. The two-dimensional (2-D) propagation speed for the downward branch ranges from 4.25×104 m/s to 3.85 ×105 m/s, with an average value of 1.01×105 m/s, and it ranges from 2.69×104 m/s to 3.61×105 m/s with an average speed of about 1.22×105 m/s for the horizontal one.
  • Ionosphere D-layer lowering in the region of the South Atlantic Magnetic
    • Abstract: Publication date: Available online 9 October 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): António A.S. Magalhães, Gabriel Guerche, Jean-Pierre RaulinAbstractIn this paper we analyse the effects of 25 solar flare events over long VLF propagation paths, one of them with the very remarkable property of crossing nearly the centre with the lowest magnetic field intensity in the South Atlantic Magnetic Anomaly (SAMA). The phase of the VLF transmitter signal (NPM: 21.4 kHz) on Lualualei, Hawaii, was recorded at the stations Punta Lobos (PLO, Peru) and Atibaia (ATI, Brazil) between 2007 March and 2011 September. Both paths NPM-PLO and NPM-ATI are collinear, and the comparison of the recorded phases suggests a descent of the lower ionosphere quiescent reflection height, possibly associated with the weakening of the Earth magnetic field in the SAMA region.
  • Modeling Schumann resonances with schupy
    • Abstract: Publication date: Available online 8 October 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Tamás Bozóki, Ernő Prácser, Gabriella Sátori, Gergely Dálya, Kornél Kapás, János TakátsyAbstractschupy is an open-source python package aimed at modeling and analyzing Schumann resonances (SRs), the global electromagnetic resonances of the Earth-ionosphere cavity resonator in the lowest part of the extremely low frequency band (
  • VLF wave propagation and middle polar atmosphere as a detector of
    • Abstract: Publication date: Available online 7 October 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): G.F. Remenets, V.A. ShishaevAbstractIn this paper we present a catalog of the new geophysical phenomena, Ultra-energetic Relativistic Electron Precipitations (UREP), and relying on our previous physics analysis of it, describe its specific quantitative characteristics. This full dataset was created based on the continuous very low frequency measurements of a polar radio path with three working frequencies during the years 1988 – 1992. As discussed in our previous works, the main feature of this phenomenon is that ultra-energetic relativistic electrons precipitate into the middle polar atmosphere and cause additional ionization at the altitudes 10-45 km by the bremsstrahlung X-rays and gamma rays which are generated by the ∼ 100 MeV penetrating electrons. This new geophysical phenomenon was detected by the ground-based measurements of the Very Low Frequency (VLF) signal variations due to the signals’ passing along the terrestrial waveguide with a sporadic layer of ionization created by the X-ray radiation in the middle atmosphere. Therefore, in all these abnormal cases the middle atmosphere and the processes of VLF wave propagation are the detector of this new effect.In the dataset presented, each event is identified by the abnormal values of VLF signals variations which are not typical for the measurements in the distance zone of measurements. In a case of this moderate distance from a VLF ground based source (∼ 900 km), which is investigated here, the abnormality manifests in the qualitatively similar negative type of variations in both phase and amplitude of the detected signals for all 3 used radio wave frequencies. Such similarity appears due to the signal of strait seeing turns into the diffraction wave, the 1-st hop (ray) becomes ∼ 2 times less. The indicated abnormality in the experimental variations proves that the second sky wave does not reach a receiver and there is an anti-phase interference effect between two field terms at the middle distance zone, previously unknown. Over 1988 -1992 years, 135 VLF disturbances have been observed (with 17 events during the night) with mentioned abnormal behavior: 7 powerful disturbances, 72 strong disturbances and 56 moderate disturbances. It is known that the corresponding minimal values of effective height (altitude) of these VLF disturbances are: 25 - 35 km for powerful, 35 - 45 km for strong, and 45 - 55 km for moderate disturbances.The catalog may be used in the future researches.
  • PC index as a proxy of the solar wind energy that entered into the
           magnetosphere: (5) Verification of the solar wind parameters presented at
           OMNI website.
    • Abstract: Publication date: Available online 7 October 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): O.A.Troshichev, D.A.SormakovThe polar cap magnetic activity (PC) index is regarded as a proxy for energy that input into the magnetosphere during the solar wind-magnetosphere coupling [Resolutions of XXII IAGA Assembly, 2013]. The PC index variations usually follow the changes of the interplanetary electric field EKL, which is estimated by the solar wind parameters fixed in the Lagrange point and published in the OMNI database. However, the correspondence between EKL and PC is often violated under disturbed conditions. To reveal the regularity of violations, the correlation between the PC index and “estimated” EKL field was examined in course of magnetic disturbances, the magnetic substorms occurrence being regarded as independent evidence of the geoeffective solar wind affecting the magnetosphere. Analysis, carried out separately for PCN and PCS indices, showed that magnetic activity in the winter polar cap (PCwinter) ensures statistically more correct results than that in the summer polar cap (PCsummer). Correlation between the PCwinter index and “estimated” EKL field proved to be good (R>0.5) in about 80% of the examined substorm events. In other 20% of events the correlation was poor or negative, even though the magnetic substorms occurred in evident association with the preceding PC growth. It implies that “estimated” EKL field did not impact on the Earth’s magnetosphere in these cases. Thus, the PC index makes it possible to verify the actual EKL field affecting the magnetosphere, and to check, in such manner, whether or not the solar wind fixed in the Lagrange point (presented at the OMNI database) encountered the magnetosphere in actuality.
  • Estimation of integrated water vapor derived from Global Navigation
           Satellite System observations over Central-Western Argentina (2015-2018).
           Validation and usefulness for the understanding of regional precipitation
    • Abstract: Publication date: Available online 7 October 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): M.F. Camisay, J.A. Rivera, M.L. Mateo, P.V. Morichetti, M.V. MackernAbstractThis study assesses the possibility of using Global Navigation Satellite System (GNSS) observations in combination with measurements of surface pressure and temperature to derive Integrated Water Vapor (IWVGNSS) estimates in Central-Western Argentina (CWA), a semi-arid region with complex topography. A significant agreement (coefficient of determination> 0.9) is observed between IWVGNSS and IWV estimates from radiosonde measurements, highlighting the capability of the GNSS stations to provide IWVGNSS estimates for a denser network. The variability of the IWV estimates, the atmospheric pressure and precipitation totals for a case study are compared. The results show that the occurrence of the increase in IWV values (positive IWV anomalies) precedes abundant precipitation over the CWA, in conjunction with the presence of mid-troposphere low-pressure anomalies acting as synoptic forcing. This kind of information provides a more comprehensive picture about the atmospheric processes involved in the development of deep convection, and it can be used for the development of contingency plans in the region. Heavy precipitation events and the difference in timing between positive IWV anomalies, both on-site and for their surroundings, should be considered.
  • Water vapor study using MODIS and GPS data at 64 continuous GPS stations
           (2002-2017) in Indian subcontinent.
    • Abstract: Publication date: Available online 1 October 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Sridevi Jade, T.S. Shrungeshwara, Boddapati AnilABSTRACTPrecipitable Water Vapor (PWV) is estimated using MODIS (Moderate Resolution Imaging Spectro-radio-meter) Terra level 3 data with daily resolution i.e MOD08_D3 at 64 cGPS (continuous Global Positioning System) stations spatially spread over Indian subcontinent between geodetic latitude 5º to 35º N and geodetic longitude of 70º to 96º E. MODIS-PWV is compared with GPS-PWV estimated at these cGPS stations to check the validity of water vapor retrieved from MODIS data in Indian subcontinent. Correlation coefficient (R2) between daily values of MODIS and GPS water vapor is above 0.9 with RMSE (root mean square error) of 2 to 5 mm for 22 cGPS in peninsular India, above 0.9 with RMSE of 3 to 6 mm for 5 cGPS in northeast India and above 0.8 with RMSE of 1 to 9 mm for 26 cGPS in Himalayas. PWV time series at all the cGPS stations indicated distinct seasonal cycle for both MODIS and GPS PWV with high RMSE (∼ 6 mm) in wet months and low RMSE (∼ 3 mm) during dry months. Taking advantage of broad spatial spread of stations and long span of data, model for spatial variability of GPS-PWV for Indian subcontinent is proposed. Inter-annual and seasonal variability of GPS-PWV is discussed in detail for peninsular India, northeast India and Himalayas.
  • Advances in Ball Lightning Research
    • Abstract: Publication date: Available online 26 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Mikhail L. Shmatov, Karl D. StephanAbstractBall lightning is a rarely observed phenomenon whose existence is attested to by thousands of eyewitness reports, but which has so far evaded a widely accepted scientific explanation. This review paper summarizes theoretical, observational, and experimental work in the field since approximately 2000. In particular, several situations when mobile phone cameras as well as scientific instruments have been used to capture numerous events that are candidates for ball lightning sightings are considered. We evaluate recent experimental attempts to produce laboratory ball lightning, review what is known about possible ball lightning hazards, and conclude with recommendations for future research in this area.
  • Storm-time Mesoscale Field-Aligned Currents and Interplanetary Parameters
    • Abstract: Publication date: Available online 26 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): A. Adero Ochieng, Geeta Vichare, Paul Baki, Pierre Cilliers, Pieter Kotze, Chao Xiong, Ashwini Kumar SinhaAbstractPresent paper studies Field aligned currents (FACs) estimated by employing Ampere’s law to the magnetic field recorded by CHAMP satellite during 24 geomagnetic storms. Low-pass filtered FACs with a cutoff period of 20 s (scale size∼150 km) are used to determine FAC range, which is defined as a peak-to-peak amplitude of FAC density. Thus we are considering only the strongest positive and negative FACs emerging either from Region 1, Region 2, Region 0, or substorm current wedge systems. It is known that the FACs significantly depend on the highly variable solar wind (SW) and interplanetary magnetic field (IMF) conditions and also on the processes internal to magnetospheric-ionospheric system such as substorm. The correlation analysis carried out here shows that sometimes the FAC range, correlates well with SymH, AsyH, AsyD, AL, am and Kp indices (>95% significance), but not always. The variation of the FAC range with magnetic local times shows distinctly different patterns during southward and northward IMF conditions, with peaks near dawn-dusk during southward IMF and near local noon-midnight during northward IMF. These results are in agreement with the earlier reports. However, the seasonal dependence reveals that the noon time peak is essentially associated with the summer season. We have determined a new parameter called ‘occurrence rate of FAC range ≥ 1 μA/m2’ and examined it under various solar wind and IMF conditions. It is found that the probability of FAC range ≥1 μA/m2 have a clear dependence on the clock angle, suggesting more frequent intensifications during southward IMF. Clear linear dependence on the cone angle demonstrates higher occurrence probability of FAC range ≥ 1μA/m2 when the IMF is perpendicular to the Sun-Earth line (cone angle nearing 90°). All these results based on the newly defined parameters such as FAC range and probability of FAC range ≥ 1 μA/m2, for the storm time mesoscale FAC are consistent with the previous studies. The FAC ranges are found to have a linear dependence on the values of IMF BY, BYZ, BT and BZ, though saturation is apparent at higher values of the IMF parameters. FAC range shows distinctly different dependence for slow and fast solar wind, suggesting the importance of the composition and properties of SW in controlling the FAC strengths.
  • Arctic polar vortex splitting in early January: the role of Arctic sea ice
    • Abstract: Publication date: Available online 26 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Vladimir V. Zuev, Ekaterina SavelievaAbstractThe Arctic stratospheric polar vortex usually forms in autumn, reaches its peak intensity in mid-winter and decays in spring. The polar vortex strength and persistence in the winter–spring period play an important role in stratospheric ozone depletion with the return of solar radiation in late winter. The polar vortex breakdown in most cases occurs under the influence of vertically propagating planetary Rossby waves. The increased activity of planetary waves was observed in 1984/1985, 1998/1999 and 2012/2013 and led to the polar vortex breakdown in mid-winter, after which it was not observed for more than a month. In this study, Arctic sea ice loss is considered as the most likely cause of the increased activity of planetary waves resulting in the unusual weakening of the Arctic polar vortex. Arctic sea ice extent was a record low in autumn 1984, 1998 and 2012 in the Beaufort Sea, the Canadian Arctic Archipelago and the Central Arctic.
  • Spatio -Temporal Trend Detection of Hydro -Meteorological Parameters for
           Climate Change Assessment in Lower Tapi River Basin of Gujarat State,
    • Abstract: Publication date: Available online 26 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Vishal Chandole, Geeta S. Joshi, Shilpesh CAbstractThe present research aims to assess the climate change in Lower Tapi River Basin (LTRB) of the state of Gujarat in India. The Mann-Kendall (MK) test with Sen's slope estimator and Sen's Innovative Trend Analysis (ITA) have been used for detecting the trend of the hydro-meteorological parameters- temperature and rainfall. The temperature trend during the period 1979 - 2014 has been analyzed using MK test and ITA method. The annual maximum, annual minimum and annual mean temperature analysis is carried out for 5 weather stations in the basin. Also, the trend has been analyzed using MK test and ITA method for annual rainfall for 9 raingauging stations for three time periods i.e. 1928-2013, 1955-2013, and 1970-2013. Most of the results obtained from these two methods for trend detection of these hydro-meteorological parameters are found to be matching. Further, the results of this study shown that the annual maximum, minimum and mean temperature increases at trend value of 0.009 °C/yr, 0.0244 °C/yr and 0.0188 °C/yr, respectively, over the LTRB during 1979–2014. The annual rainfall increases at the trend value of 2.185 mm/yr, 4.181 mm/yr and 5.495 mm/yr for the period of 1928-2013, 1955-2013 and 1970-2013 respectively. The magnitude of upward (positive) trend of annual rainfall is greater for the period of 1955-2013 and 1970-2013 in comparison to the period of 1928-2013. The spatial distribution of temporal trend of these hydro-meteorological parameters have been represented in Arc-GIS 10.3.The results of Spatio-Temporal trend distribution over the study area shown that the annual mean and annual minimum temperature indicates the upward (positive) trend over whole LTRB, while annual maximum temperature indicates the upward (positive) trend over the basin except west coastal region of LTRB. The annual rainfall exhibits upward (positive) trend in all three time periods over entire LTRB.The trend (positive/negative) detected for mean temperature and annual rainfall is found to be consistent with the trend noticed by Indian Meteorological Department for the state of Gujarat. The spatial distribution of trend further needs to be analysed to correlate it with changing pattern of land use – land cover over a period of time. The present case study for the assessment of climate change would be useful to the water resources engineers for planning and management and policy decisions for climate change adaptation in the study area.
  • Lightning Severity Classification Technique using Very Low Frequency
           Signal Feature Extraction
    • Abstract: Publication date: Available online 24 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): N.S. Arshad, M. Abdullah, S.A. Samad, N.M. HattaAbstractHigh intensity lightning strike can lead to Very Low Frequency (VLF) signal reception. The lack of VLF signal feature characterisation creates the need for commercial lightning dataset subscription, so as to determine the causative lightning strike. This paper presents a signal feature analysis of VLF signal for high intensity lightning severity classification purpose. As such, the analysis was comprised of dual stages, namely feature extraction and feature classification, for two-class recognition. In the feature extraction stage, Discrete Wavelet Transform was implemented to decompose the VLF signal into four frequency bands. In each frequency band, five-signal parameter analysis was executed to yield twenty signal features. Next, the classification stage was executed to determine the best signal feature combination and the most dominant signal feature that generated the highest classification accuracy within the five classifiers. The simulation revealed that the most optimum signal feature combination was achieved via Boosted Trees classifier with classification accuracies of 70% and 50% for training and test datasets, respectively. Class prediction in the skewed test dataset appeared consistent with the test data classification accuracy. The Zero Crossing Rate between 30 and 60 kHz emerged as the most dominant signal feature due to its impact on all classifiers’ best signal feature arrangement. The proposed recognition model enables the detection of high intensity lightning classes through the use of VLF signal features.
  • Application of a high-temporal resolution model for the identification of
           columnar aerosol components.
    • Abstract: Publication date: Available online 24 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Francesco Esposito, Mariarosaria Calvello, Giulia PaveseAbstractA high-temporal resolution model for the identification of columnar aerosol composition was applied to two sets of radiometric measurements obtained one in a semi-rural site of South Italy and the other in an urban/traffic site of the Po Valley, northern Italy. Inputs of the model are the spectral Aerosol Optical Depths (AODs) from direct solar radiation data to derive the contribution to the total extinction of nine aerosol species, i.e Water Soluble (WS), Black Carbon (BC), Sea Salt accumulation (SSacc), Sea Salt coarse (SScoa), Biogenic (Bio), Mineral Coarse (Mcoa), Mineral Accumulation (Macc), Small Organic Matter (SOM), and Large Organic Matter (LOM). In order to better parameterize the absorptive properties of dust and organic particles, a wavelength dependent imaginary part of the refractive index was used for dust and organics. Despite the differences between the two sites, a prevalence of fine aerosols (organics, WS and BC) was found in both cases suggesting the relevance of anthropogenic sources such as traffic. The retrieved AOD BC component was compared to Equivalent BC (EBC) concentrations measured in situ by an aethalometer at both sites. For mean daily values good correlations were found (R2 = 0.7), whereas high-temporal resolution (hourly basis) columnar composition was verified to be more reliable in cases of surface-column coupling. The possibility to apply this simple model to direct irradiance data from portable radiometers in areas where no routine measurements are available, and obtaining results with an increased temporal resolution, can help to gather information on aerosol columnar composition to be used in radiative, climate and transport models.
  • Lightning Response during Forbush Decrease in the Tropics and Subtropics
    • Abstract: Publication date: Available online 24 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Qiong Wu, Hui Li, Chi WangAbstractGalactic cosmic rays (GCRs), modulated by the heliospheric magnetic field (HMF), are speculated to provide a possible link between solar activities and the earth’s lightning variation. To test this hypothesis, we investigate the correlation between the sudden decrease of GCR in a few hours to one day, known as Forbush Decrease (FD), and the lightning incidence in the tropics and subtropics. During the operating period of the TRMM Satellite, 28 FD events are identified with their decrease amplitudes (DAs) greater than 4%. For a typical FD event occurred on January 10 2002, the daily cosmic ray (CR) intensity presents an intense decline from 5830.33 counts/min to 5675.96 counts/min in one day. Correspondingly, the daily lightning count decreases right after the FD’s onset without any obvious time delay, specifically from 3474 day-1 to 672 day-1 in one day, and reaches its minimum of 355 day-1 another day later. Based on the superposed epoch analysis (SEA), similar statistical correlation is further confirmed. On average, the adjusted daily lightning anomaly decreases from 0.33 to -0.31 in three days after the FD’s onset. The result of the Monte Carlo test indicates that such positive relevance between the CR intensity and the lightning incidence during a FD event is statistically significant.
  • Variation of Global Diurnal Temperature Range Associated with the
           Madden-Julian Oscillation
    • Abstract: Publication date: Available online 23 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Jialin Lin, Taotao QianAbstractThis study examines the impact of the intraseasonal Madden-Julian Oscillation (MJO) on global land surface diurnal temperature range (DTR) using two daily surface air temperature datasets. The results show that the MJO significantly affects DTR over all the continents. The two datasets are highly consistent with each other, suggesting that the results are robust. Significant correlations exist in all seasons over the tropical continents, including Africa, India, southeast Asia, Australia, central America and Amazon. In the extratropics, the correlations change with season. The highest correlations occur in winter for Europe, in winter and spring for China, in autumn for United States, and in summer and winter for Canada. The surface DTR anomalies coincide well with the outgoing longwave radiation (OLR) anomalies at the top of the atmosphere, suggesting that variations of DTR are associated with variations of clouds, which is consistent with the results of previous studies on DTR trend and variability at seasonal to multi-decadal time-scales. The DTR variations are also associated with changes of deep convection, soil moisture and snow cover.
  • Verification of ionospheric perturbation induced L-band frequency
           scintillation using HF/VHF bands over the African equatorial and low
           latitude region, Ethiopia
    • Abstract: Publication date: Available online 23 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Samson Tilahun, Yekoye AsmareAbstractThis study verifies the ionospheric perturbation induced scintillation in L- band range of frequency using HF/VHF bands over the African equatorial and low latitude regions with a focus over Ethiopia. The study was conducted using the SCINDA, ionosonde and beacon receivers installed at different regions in Ethiopia. In the F-layer height (hmF2), a reverse decrease of foF2 in combination with significant background TEC reaching up to 10 TECU prior to the depletion was observed during the evening hours. This creates conducive environment for the generation of ionospheric irregularities that can be manifested by Rate of TEC Index (ROTI) and scintillation index (S4) enhancement. Vertical Perturbation Index (PI) was computed using vertically integrated ion density profiles to verify the irregularities from independent source and found that HF inferred PI can potentially identify the existence of ion density irregularity and further verify L-band frequency scintillation. On the other hand, simultaneous observation of S4 in VHF and UHF bands showed excellent agreement despite VHF scintillates more than UHF due the difference of transmitting frequency bands. Besides, Power spectrum density (PSD) was computed using the FFT algorithm for S4 data measured while receiving L-band and VHF signals for selected PRNs observed by the receivers. The calculated slope (m) and the strength of irregularity (beta) using the power spectral law has enabled us to produce a model which better fits the observed spectrum. It shows beta higher for VHF and lower for UHF; while, PSD modeling better matches for UHF than VHF spectral observation.
  • Polarization analysis of ELF/VLF waves generated by beating of two HF
           waves in the polar ionosphere
    • Abstract: Publication date: Available online 23 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Tong Xu, Michael Rietveld, Jian Wu, Guanglin Ma, Yanli Hu, Jun Wu, Qingliang LiAbstractModulated high frequency heating of the polar ionosphere in the presence of a polar electrojet current (PEJ) can generate extremely/very low frequency (ELF/VLF, 3 Hz–30 kHz). In order to overcome the dependence of the radiation intensity on the variable PEJ, researchers have focused on electrojet-independent approaches. One potential method is so-called “beat-wave” (BW) ELF/VLF generation invoking nonlinearity of the F-region ionospheric plasma, but this F-region source mechanism remains controversial. We perform polarization analysis of BW generated ELF/VLF waves using EISCAT heating facility near Tromsø. The results show that ELF/VLF waves can be decomposed into right- (R) and -left (L) handed circularly polarized waves with comparable strengths, and the polarization ellipse tends to be parallel to the well-known dominant background electric field, which is fully consistent with the recognized features of ELF/VLF waves generated by PEJ modulation. Hence, the results demonstrate that the BW generated current is located in the D/E region, and not the F region.
  • Diurnal and seasonal variations of Radon (222Rn) and their dependence on
           soil moisture and vertical stability of the lower atmosphere at Pune,
    • Abstract: Publication date: Available online 18 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Jeni Victor N, Devendraa Siingh, R.P. Singh, R. Singh, A.K. KamraAbstractContinuous measurements of the concentration of Radon (222Rn) and its progenies were made with a Radon detector, RTM 2200, at a tropical site, Pune (18° 31’ N, 73° 55’ E, 560 m), India from January to December, 2012. Simultaneous measurements of small ions of < 1.6 nm diameter were made with a Neutral Air Ion Spectrometer (NAIS). Annually - averaged diurnal variation curves of 222Rn concentration showed a peak (∼ 9.9 Bq m-3) at 0800 Local Time (LT) and a minimum (∼ 5.4 Bq m-3) at 1800 LT. Diurnal variations of 222Rn concentration during winter, post-monsoon, and pre-monsoon seasons were almost similar in shape but with decreasing amplitudes in these seasons. However, during monsoon season, 222Rn concentration was the lowest and remained almost constant throughout the day. Monthly mean value of 222Rn concentration was the highest in December and the lowest in June. Polonium (218Po) concentration did not show any systematic diurnal variation. Results are explained in terms of surface meteorology, soil moisture, soil temperature, vertical wind velocity, local topography and development of atmospheric boundary layer. 222Rn concentration increased with soil moisture content of < 16 %, rapidly dropped down to dry soil values and then remained almost constant with increasing soil moisture. On the other hand, 222Rn concentration decreased with the increase of upward vertical wind velocity in the atmospheric boundary layer. The diurnal variations of ionization rate, directly estimated from 222Rn measurements, and calculated from ion concentration measurements showed some similarities but differed in their amplitudes. Annual effective dose of 222Rn (∼ 0.075 mSv) as estimated from our measurements at Pune was found below the value prescribed by World Health Organization.
  • The Origin of Ball and Bead Lightning from an Expanded Lightning Channel
    • Abstract: Publication date: Available online 16 September 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): R. MorrowAbstract.It is shown how ball and bead lightning can originate from a narrow lightning channel which has been expanded by an ionizing wave. The resulting plasma structure development is followed for 10 s, and it is shown that the electric field developed can act as an electrostatic trap for negative burning particles. Previously it has been shown that a secondary lightning stroke current travelling down the expanded channel is necessary to explain the strength of the channel luminosity. This same secondary current can constrict the channel irregularly, via the magnetic pinch effect, to produce elongated segments of the channel; these become ball and bead lightning. All the plasma balls/beads will be “phantom plasma” structures unless some negatively-charged burning particles (fuel such as soil, copper wire or smoke) are trapped in the electric field distribution providing illumination.
  • Variation of chemical characteristics of precipitation with respect to
           altitude gradient on the northern slope of Mt. Taibai, China
    • Abstract: Publication date: Available online 26 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Y. Zhao, Q. Feng, A.g. Lu, R. DeoAbstractA systematic investigation and greater understanding of the precipitation chemistry with respect to the altitude gradient in mountainous areas is necessary to promulgate the detrimental consequences of pollution on various ecosystems. Studies on the chemical compositions of wet precipitation were performed on the northern slopes of Mt. Taibai, Qinling Mountains, one of the highest mountains in East China, from different lateral monitoring stations (i.e., with elevations between 610 and 3511 m) over the period from 2011 to 2014. All samples were analyzed for major ions (SO42–, NO3−, Cl−, F−, NH4+, Ca2+, Mg2+, Na+, and K+). The results revealed that the total ion concentration and average measured ions concentrations in precipitation decreased with the increase of altitude in the Mt. Taibai. The concentrations of precipitation ions are always higher during non–monsoon period compared to the monsoon period, except for the altitude above 3000 m a.s.l.. A negative gradient of approximately −6.58 and −34.04 μeq·L−1/100 m of the total ion concentrations was obtained during the monsoon and the non–monsoon period, respectively. NH4+ was the most promising species for completely neutralize the acidity at the altitude of 500–1000 and 3000–3500 m a.s.l., while Ca2+ was the potential species for completely neutralize the acidity at the altitude of 1000–3000 m a.s.l.. The crustal–derived species (Ca2+, Mg2+, Na+, K+ and Cl−) exhibit statistically significant correlations with each other at the altitude from 500 to 2500 m a.s.l. (r = 0.44–0.99). The contributions of sea salt source and terrestrial source to SO42– and NO3− are small, which is mainly contributed by human activities. For Na+, Mg2+, and K+, there was both the contribution of the terrestrial and human activities. The inorganic pollutants (major ions such as the SO42–, NO3−, Cl−, F−, NH4+, Ca2+, Mg2+, Na+, and K+) in the Mt. Taibai appear to be derived from the regional crustal dusts, anthropogenic emissions, and the long–range transported from the sea.
  • Correlation between ionospheric scintillation effects and GPS positiong
           over Brazil during the last solar maximum (2012–2014)
    • Abstract: Publication date: Available online 29 March 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Daniele Barroca Marra Alves, Eniuce Menezes de Souza, Tayná Aparecida Ferreira GouveiaAbstractGNSS (Global Navigation Satellite System) can provide high accuracy positioning with low costs. But, depending on error sources, as atmospheric effects, it can be degraded. Ionosphere is one of the most important error sources in GNSS positioning. Among several effects caused by ionosphere, the irregularities like ionospheric scintillations are very relevant. It can cause cycle slips, degrade the positioning accuracy and, when severe enough, can even lead to a complete loss of signal lock. Brazil, in particular, is located in one of the regions most affected by ionospheric scintillations and these effects were intensified during the last solar maximum. In this paper the main goal is to evaluate the impact of scintillation effects on positioning degradation during the last solar maximum. So far, it was used data of 2012–2014 from three reference stations located in different regions of Brazil. Statistically significant correlations were identified from Spearman's correlation coefficient. From Odds Ratio, an effect-size statistics, it was possible to see that the chance of large discrepancies in 3D positioning coordinates could be three times larger under strong scintillation effects (S4 ≥ 1) than under moderate ones (0.5
  • Seasonal, interannual and SSW related variations of middle atmospheric N2O
           and NOx over low latitudes
    • Abstract: Publication date: Available online 15 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Oindrila Nath, S. SridharanAbstractThe volume mixing ratios (VMRs) of Nitrous Oxide (N2O) and NOx [Nitric Oxide (NO) + Nitrogen-di-Oxide (NO2)] derived from the radiance measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) Fourier infrared spectrometer, for the period 2007–2011 have been used to study their seasonal, interannual as well as Sudden Stratospheric Warming (SSW) related variations in the equatorial (5°N-5°S) stratosphere. Both N2O and NOx VMR show a clear seasonal variation around 45 km. The N2O VMR exhibits minimum (around 200 ppbv) during July–August and remains at 250–300 ppbv during the rest of the months. The NOx VMR is found to be minimum (around 10 ppbv) during May–July, whereas it shows higher values (∼15–17 ppbv) in the other months. Higher values are found in N2O and NOx VMRs in the years 2008 and 2010 in the northern tropics (10–30°N) when the QBO is in westward phase favouring high residual meridional circulation. During the SSW of 2009, NOx VMR is found to increase by 3 ppbv. Using a primitive chemistry-transport model, the increase in NOx during the SSW is demonstrated to be due to the enhanced vertical upwelling as well as meridional circulation prior to the onset of the SSW in response to the larger planetary wave activity.
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