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Journal of Atmospheric and Solar-Terrestrial Physics
Journal Prestige (SJR): 0.696
Citation Impact (citeScore): 2
Number of Followers: 170  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1364-6826
Published by Elsevier Homepage  [3185 journals]
  • Multi-instrument investigation of troposphere-ionosphere coupling and the
           role of gravity waves in the formation of equatorial plasma bubble
    • Abstract: Publication date: August 2019Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 189Author(s): M. Sivakandan, I. Paulino, T.K. Ramkumar, A. Taori, A.K. Patra, S. Sripathi, K. Niranjan, A.V. Bilibio Present study investigates the role of gravity waves in the generation of equatorial plasma bubbles (EPBs) during geomagnetic quiet conditions using co-located observations from Gadanki (13.5oN, 79.2° E) an all sky airglow imager, Gadanki Ionospheric Radar Interferometer (GIRI) and Ionosonde observations from Tirunelveli (8.7° N, 77.8° E). To avoid any changes occurring in the background ionosphere, four consecutive nights of observation during 03–06 February 2014 is used. Out of these four nights, three nights (i.e., 03, 05 and 06 February 2014) exhibit occurrence of EPBs in the OI 630 nm airglow emission and radar plumes and there is no bubble occurrence during one night, though the ionospheric peak altitude (h′F) value is more than 350 km in all these nights. During these four nights the structures observed in the E-region drifts and gravity waves noted in the mesospheric OH emissions are analyzed. It is found that there are common periodic oscillations in the OH peak emission altitude and E-region in three nights (03, 04 and 05 February 2014). The mesospheric gravity wave structures are ray traced to their potential sources in the lower atmosphere and also for the possibility of their propagation to the E-region. Our results suggest that apart from horizontal wavelength and amplitudes, the propagation angle of gravity wave may also be important for seeding of the Rayleigh-Taylor (R-T) instability. Thus, it gives an insight about the role of lower – middle and upper atmospheric coupling on the occurrence of the noted EPBs.
  • Optical properties of intracloud and cloud-to-ground discharges derived
           from JEM-GLIMS lightning observations
    • Abstract: Publication date: August 2019Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 189Author(s): K. Bandholnopparat, M. Sato, T. Adachi, T. Ushio, Y. Takahashi We developed a new method to distinguish the lightning discharge type using lightning data obtained by JEM-GLIMS spaced-based mission and ground-based lightning network that are JLDN, NLDN, WWLLN, and GEON. As a first step, we selected 1057 lightning events detected by the JEM-GLIMS cameras (LSI) and spectrophotometers (PH) in 2014. Then, we compared the JEM-GLIMS optical data to the ground-based lightning data in order to check the simultaneous detection of JEM-GLIMS lightning events by the ground-based lightning networks, and finally we identified the discharge type of the JEM-GLIMS lightning events. We succeed in identifying 941 simultaneous lightning events and found that 582, 93, and 266 lightning events were IC, +CG, and -CG discharges, respectively. As a next step, we calculated intensity ratios between blue and red PH channels, i.e., 337nm/762 nm, 316nm/762 nm, 392nm/762 nm, 337nm/(599–900 nm), 316nm/(599–900 nm), and 392nm/(599–900 nm) for the 941 lightning events in order to specify the optical characteristics of IC, +CG, and -CG discharges. It is found that the PH intensity ratio of +CG discharges is the highest and that the PH intensity ratio of IC and -CG discharges is smaller than that of +CG discharge. We also found that the characteristics of the LSI intensity ratio are almost comparable to those of the PH intensity ratio. As the differences of the 337nm/762 nm, 337nm/(599–900 nm), and 392nm/(599–900 nm) ratio of IC, +CG, and -CG discharges are relatively large, these three ratios are a useful proxy for classifying the discharge types for additional 7349 lightning events detected by JEM-GLIMS in order to estimate the global ratio between IC and CG discharges (Z ratio).
  • Global lightning activity and the hiatus in global warming
    • Abstract: Publication date: August 2019Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 189Author(s): Earle Williams, Anirban Guha, Robert Boldi, Hugh Christian, Dennis Buechler Multiple records of global temperature contain periods of decadal length with flat or declining temperature trend, often termed a ‘hiatus’. Towards assessing the physical reality of two such periods (1940–1972 and 1998–2014), lightning data are examined. Lightning activity is of particular interest because on many different time scales it has been shown to be non-linearly dependent on temperature. During the earlier hiatus, declining trends in regional thunder days have been documented. During the more recent hiatus, lightning observations from the Lightning Imaging Sensor in space show no trend in flash rate. Surface-based, radiosonde-based and satellite-based estimates of global temperature have all been examined to support the veracity of the hiatus in global warming over the time interval of the satellite-based lightning record. Future measurements are needed to capture the total global lightning activity on a continuous basis.
  • Linkage of meteorological parameters and anomalous radio propagation
           profile over Nigeria
    • Abstract: Publication date: Available online 1 June 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): I. Emmanuel The vertical distribution of refractivity gradient is important in determining anomalous propagation condition. Thirty five years of meteorological parameters, obtained from Era-Interim archive of European Centre for Medium-Range Weather Forecasts has been used to analyze and investigated surface meteorological data linked with refractivity gradient aloft altitude across Nigeria. Spatial distribution of surface temperature, relative humidity and refractivity gradient at 0.1 km, 0.5 km, 1.0 km and 1.5 km over Nigeria were plotted. Vertical distribution of temperature, relative humidity, refractivity and refractivity gradient were obtained for some locations across Nigeria. Similarly, spatial distribution of coefficient of determination between surface temperature, relative humidity and refractivity gradient at four different height were estimated. Linear regression were developed to investigate the relationship between surface data and refractivity gradient at different altitude. The result revealed existence of sub refractive, super refractive, and ducting across the country at 0.1 km and 0.5 km however occurrence of ducting and sub refractive disappeared at 1.0 km and 1.5 km. Likewise, the existence of temperature inversion was noticed between surface and 100 m across all the locations except in Lagos. Values of refractivity across the observed locations converged around 0.5 km. Through result of correlation coefficient and statistical parameters, significant linked have been established between surface data and refractivity gradient at different height.
  • Vertical wavenumber spectral characteristics of temperature in the
           stratosphere-mesosphere over tropical and subtropical regions
    • Abstract: Publication date: Available online 31 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Priyanka Ghosh, Som Sharma The vertical wavenumber spectra over tropical location, Gadanki (13.5° N, 79.2° E) and sub-tropical location, Mt. Abu (24.5° N, 72.7° E) is studied using the temperature measurements from ground based Rayleigh Lidar and space borne satellite observations. The slope values are lesser over Gadanki than at Mt. Abu for almost all the altitudes except for 40–50 km where it is nearly same and 60–70 km exhibiting opposite nature. Unusual spectral slope of −6.97 (Mt. Abu) and −0.09 (Gadanki) is seen at the altitude of 40–50 km in satellite temperature. Characteristics of wave oscillations perceived over both the stations are described.
  • Monitoring the global evolution of the storm ring current and storm
           indices from confined ground geomagnetic observatories
    • Abstract: Publication date: Available online 30 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): G. Zeng, C. Shen, Z.J. Rong, X. Li, T. Chen, Z.Q. Chen, Y.H. Ma For the first time, the global structure of the geomagnetic disturbance field around the Earth as well as the magnetic storm indices have been deduced from magnetic field measurements by ground observatories in a confined range of longitude. The spatial gradient of the H component of the geomagnetic disturbance field was obtained from ground geomagnetic observatories only in the Eastern Hemisphere, provided the geomagnetic disturbance field varies approximately linearly in space. Furthermore, the storm symmetric and asymmetric indices were derived and the spatial distribution and temporal evolution of the storm ring current was investigated. It was found that the storm indices derived from observatories in the Eastern Hemisphere are consistent with the officially published Kyoto standard indices which are derived from six globally distributed observatories. We also calculated the storm indices for 1941–1956 by using data from three observatories (HER, KAK and SJG). The correlation coefficient between the symmetric index deduced from three observatories and the one from the global six observatories is 0.98, and the correlation coefficient between the two kind of asymmetric indices is 0.79. Those results suggest that our approach is reasonable and significant when global ground observatories are not readily available.
  • White-light polar jets on rising phase of solar cycle 24
    • Abstract: Publication date: Available online 22 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): A.V. Kudriavtseva, D.V. Prosovetsky We studied coronal white-light jets in the polar regions of solar corona in 2009-2014. Jets were tracked on data producing by coronographs COR2/STEREO with the 2.5 - 16 solar radii field of view. We also considered their characteristics on solar cycle progress: jet occurrence rate of jets per year above the northern and southern poles, angular distributions and measured apparent velocities. The jet mean occurrence rate per year is 234 registered events. It is defined that both occurrence rate per year and the mean apparent velocities are increased to solar cycle maximum. This changes were shown to be different for the north and south polar regions and to depend on polar magnetic fields. The mean apparent velocities are increased by 1.7 times for north pole (from 134 ± 66 km/s to 229 ± 59 km/s) and by 2.4 times for south pole (from 101 ± 37 km/s to 243 ± 79 km/s). Most of the jets with velocities > 450 km/s was registered at the solar cycle maximum.
  • 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. Deo A 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 Gouveia GNSS (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
  • Simulations of the inner magnetospheric energetic electrons using the
           IMPTAM-VERB coupled model
    • Abstract: Publication date: Available online 29 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Angelica M. Castillo, Yuri Y. Shprits, Natalia Ganushkina, Alexander Drozdov, Nikita Aseev, Dedong Wang, Stepan Dubyagin In this study, we present initial results of the coupling between the Inner Magnetospheric Particle Transport and Acceleration Model (IMPTAM) and the Versatile Electron Radiation Belt (VERB-3D) code. IMPTAM traces electrons of 10−100 keV energies from the plasma sheet (L=9 Re) to inner L-shell regions. The flux evolution modeled by IMPTAM is used at the low energy and outer L∗ computational boundaries of the VERB code (assuming a dipole approximation) to perform radiation belt simulations of energetic electrons. The model was tested on the March 17th, 2013 storm, for a six-day period. Four different simulations were performed and their results compared to satellites observations from Van Allen probes and GOES. The coupled IMPTAM-VERB model reproduces evolution and storm-time features of electron fluxes throughout the studied storm in agreement with the satellite data (within ∼0.5 orders of magnitude). Including dynamics of the low energy population at L∗=6.6 increases fluxes closer to the heart of the belt and has a strong impact in the VERB simulations at all energies. However, inclusion of magnetopause losses leads to drastic flux decreases even below L∗=3. The dynamics of low energy electrons (max. 10s of keV) do not affect electron fluxes at energies ≥900 keV. Since the IMPTAM-VERB coupled model is only driven by solar wind parameters and the Dst and Kp indexes, it is suitable as a forecasting tool. In this study, we demonstrate that the estimation of electron dynamics with satellite-data-independent models is possible and very accurate.
  • Long-term temporal and spatial analysis of SO2 over Gauteng and Mpumalanga
           monitoring sites of South Africa
    • Abstract: Publication date: Available online 23 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): S.K. Sangeetha, V. Sivakumar This paper focused on the temporal and spatial variability of sulphur dioxide (SO2) from 2004 to 2013 over 36 ground-based (GB) stations located in Gauteng and Mpumalanga provinces of South Africa. The assessment was based on the in situ SO2 data, where the GB stations were sorted into different groups and in addition, kriging-based analysis and OMI SO2 data (2004–2013) were deployed to study their seasonal spatial variability. It was observed that Pretoria west, Witbank and Randwater had high SO2 levels and standard deviations. Although, winter played a major role in having peak SO2 values in most of the stations, it was surpassing that in spring the SO2 levels of Witbank and Pretoria west stations dropped and Randwater had the highest standard deviation of 11.2 ppbv in October. A prominent seasonal variation was seen in all the groups, excluding Mpumalanga power stations (MP) group. This was particularly evident in the Vaal Triangle group. Highveld group ranked topmost level with elevated SO2 values proceeded by the MP group in all the temporal time scales. The spatial based analysis further proved that the highest SO2 levels were centred around major industrial regions of Mpumalanga, regardless of all the seasons.Graphical abstractImage 1
  • Is the Madden-Julian Oscillation reliably detectable in Schumann
    • Abstract: Publication date: Available online 22 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Ciarán D. Beggan, Malgorzata A. Musur The Madden-Julian Oscillation (MJO) is a quasi-periodic (∼30-90 days) eastward-moving atmospheric mode which primarily modifies rainfall patterns in the equatorial regions from Africa to the Pacific Ocean. It has been proposed that its signature is detectable within the intensity variations of the Schumann Resonances (SR) due to changes in the location and magnitude of the major lightning centres. Using six years of induction coil data recorded at the Eskdalemuir Observatory in the UK, we investigate whether the MJO is detectable in the first three Schumann Resonances. We extract the frequency and intensity values from each resonance every 10 min, averaged to a daily value and compare them to the Realtime Multivariate MJO (RMM) index. We use Empirical Mode Decomposition (EMD) to determine if certain modes correlate between the SR and RMM curves. We find that the EMD 30 to 70 day modes of the SR and RMM index occasionally beat in-phase during the La Niña periods of the El Niño Southern Oscillation (ENSO) but not El Niño periods. However, the relationship is not wholly consistent, implying that robust and reliable detection of the MJO in SR data remains challenging.Graphical abstractGraphical abstract for this article
  • 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. Sridharan The 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.
  • Local temperature changes in the mesosphere due to a “horizontally
           propagating” turbulent patch
    • Abstract: Publication date: Available online 11 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Alexey N. Belyaev In this study, we model thermal changes in the background atmosphere due to a horizontally” moving” turbulent patch. We divide the process of mutual adjustment of the turbulent patch and the background atmosphere into the two stages: (i) Fast high-to-low transition of the atmospheric stability within the turbulent patch induced by strong adiabatic mixing within the “moving” turbulent patch. (ii) Slow adjustment of the ambient background atmosphere to a quasi-stabilized, near-adiabatic thermal stratification within the turbulent patch. Within the framework of the first stage, assuming the existence of a background downward heat flux, we developed a boundary value problem for a non-homogeneous heat equation that accounts for turbulent dissipative heating and mixing. This two-point boundary value problem was solved analytically by applying the Fourier method (separation of variables) to the thickness of the turbulent patch. The solution obtained tends towards equilibrium as the distance from the front border of the “moving” turbulent patch increases. Within the scope of the second stage, we solved the problem of thermal coupling of the two heat-transfer domains, one of which is characterized by a high coefficient of heat transfer. Solving this problem is the basis of our proposing that the thermal structure of a turbulent patch does not change under the influence of an ambient atmosphere, while the ambient atmosphere is cooled slowly above the turbulent patch and warmed slowly below it. Consequently, it is shown that the model temperature profiles demonstrate the same features as those observed in mesospheric inversion layers (MILs): temperature inversions and a near-adiabatic lapse rate between them.
  • Cloud fraction retrieval and its variability during daytime from
           ground-based sky imagery over a tropical station in India
    • Abstract: Publication date: Available online 9 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Akshaya Nikumbh, B. Padmakumari, Sneha Sunil Total Sky Imager (TSI) is operated at a high altitude station in the Western Ghats of the Indian sub-continent from June 2012 to June 2013. The TSI image content is classified as clear, thin and thick clouds using red-blue ratio (RBR) threshold technique and then cloud fraction (CF) is retrieved. An algorithm is proposed to improve the accuracy of CF retrieval, by adapting the methodologies used in earlier studies and new developments are suggested in sections of the validation of clear sky image and the aerosol correction factor. Time series of thin, thick and total CF are constructed for each day at 5 min interval. These measurements at high temporal resolution are first of their kind over a tropical station in India. Both thick and thin CFs showed high temporal variability. The transition from one season to another season also showed distinct CF variability. Monthly mean CF showed a mono model distribution in the winter months (December and January) and a bimodal distribution in the pre-monsoon months (March, April, May) including February. During the monsoon season (JJAS) about 90% CF is observed throughout the day. The post-monsoon months (October, November) show a bimodal distribution with one peak in the morning hours and another peak in the afternoon hours. Unlike thin CF, total and thick CFs showed almost similar variability. The comparison of CF retrieved from MODIS (Terra and Aqua) and TSI showed a good correlation for overcast sky conditions, while partial cloudy skies showed less correlation due to the effect of satellite viewing angles. Such continuous measurements of CF at high temporal resolution are essential for cloud radiative forcing studies.
  • On the prediction of geoeffectiveness of CMEs during the ascending phase
           of SC24 using a logistic regression method
    • Abstract: Publication date: Available online 9 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): D. Besliu-Ionescu, D.-C. Talpeanu, M. Mierla, G. Maris Muntean Coronal mass ejections (CMEs) are pieces of the puzzle that drive space weather. Numerous methods (theoretical, numerical and empirical) are being used to predict whether the CME will be geoeffective or not. We present here an attempt to predict the geoeffectiveness of a given CME using a modified version of logistic regression model proposed by Srivastava (2005), using only initial CME parameters. Our model attempts to forecast if the CME will be associated with geomagnetic storm defined by a minimum Dst value
  • Possible process of ball lightning training in nature
    • Abstract: Publication date: Available online 3 May 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Anatoly I. Nikitin An electrodynamic model of ball lightning is proposed, according to which it is considered as a collection of plasmoids, consisting of electrons and protons, which rotate in closed orbits. Protons are retained in the orbit due to Coulomb attraction to the electron ring, while electrons are drifting in the crossed electric and the magnetic field, generated by the protons’ motion. This system has a non-compensated positive electric charge. These plasmoids placed inside a water shell serve to isolate a vacuum cavity from the atmosphere and to create a force, preventing expansion of proton rings. A mechanism of ball lightning creating near a loop of linear lightning channel is discussed. Ultraviolet radiation of the lightning discharge ionizes air, and due to the action of radio-frequency radiation with a non-uniform spatial distribution of intensity, a vacuum cavity is formed. The action on the plasma exerted by the crossed magnetic and eddy electric fields leads to separation and acceleration of charges. Losing a part of electrons, the system acquires a positive charge. Due to motion of water drops in the non-uniform field of this charge a dielectric shell around the ensemble of plasmoids is formed. A scheme of setup for ball lightning creation in laboratory is proposed.
  • Analysis of the first positive polarity gigantic jet recorded near the
           Yellow Sea in mainland China
    • Abstract: Publication date: Available online 30 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Qijia He, Jing Yang, Gaopeng Lu, Zhixiong Chen, Yu Wang, Mitsuteru Sato, Xiushu Qie At 12:16:22 UTC on 12 August 2010, a gigantic jet (GJ) was recorded over a thunderstorm near the Yellow Sea in China. The extremely low-frequency (ELF) magnetic field recorded at the Onagawa Observatory indicates that this GJ transferred positive charge from the thundercloud to the ionosphere (namely a +GJ event), which is the first observation of a +GJ reported in mainland China. The top altitude of this GJ was estimated to be about 89 km. The parent thunderstorm formed in a very moist environment (precipitable water of 75.4 mm) with moderate convective available potential energy (1294 J/kg) and lifted index (−3.19), and strong 0–6 km wind speed shear (16.3 m/s). The meteorological parameters are not much different from typical summer thunderstorms. The area of cloud top brightness temperature colder than −60 °C (altitudes above 14 km) increased significantly after 10:00 UTC and reached the maximum at 12:00 UTC (16 min before the GJ), suggesting the occurrence of the GJ was related to the strong vertical development of the thunderstorm. Around the time of the GJ, the south cell of the storm featured overshooting top as indicated by radar data. Additionally, the storm was dominated by negative cloud-to-ground (-CG) flashes with an increase in -CG flash rate around the time of the GJ occurrence, indicating the storm appeared to be of normal polarity (the main positive charge region located above the main negative charge region). The + GJ was probably produced by a normally electrified thunderstorm, and a possible explanation for this unexpected behavior and different lightning activity of GJ-producing storms were discussed.
  • Assessment of heavy precipitation events associated with floods due to
           strong moisture transport during summer monsoon over India
    • Abstract: Publication date: Available online 26 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): D. Dhana Lakshmi, A.N.V. Satyanarayana, Arun Chakraborty Integrated water vapor transport (IVT) detection algorithm is implemented over the Arabian Sea basin for the identification of strong moisture transport events (SMTs) over Indian subcontinent during 1979–2013. Attempt has been made through the spatiotemporal characteristics whether SMTs are responsible for the occurrence of heavy precipitation events (HPEs) and floods. The results demonstrated that the persistent SMTs are related to HPEs towards flooding over parts of Indian subcontinent during summer monsoon. In the study a total of 364 SMTs have been identified. It is seen that the SMT axes is reaching from eastward direction crosses over land mass of west coast of India and moves in north-westerly direction through Assam, Bihar and Uttarakhand. The results reveal a better correlation of occurrence of HPEs with the presence of SMTs and a large portion of SMTs lead to HPEs, as well as large fraction of HPEs occurs after SMTs. The characteristics of specific flood and rainfall events associated with the occurrence of SMTs show that existence of strong relation between presence of SMTs and extreme precipitation events for the western region where SMTs make landfalls (over Mumbai in 2005), for the north western region where SMTs penetrate inland (over Uttarakhand in 2013), whereas the relations is weakened in the north eastern region (e.g., over Bihar in 2008). The results emphasize that the existence of large amount of atmospheric moisture over the study regions 2–3 days before extreme precipitation events is due to SMTs. Given the narrowness of SMTs, the location of SMTs over each region is related to the occurrence or lack of extreme precipitation events. In addition, rainfall intensity enhanced with the duration of persistent SMTs of the majority of identified events. A significant negative (positive) dependence was found between SMT totals and the Southern Oscillation Index (SOI) (Indian Ocean Dipole (IOD)), with a greater frequency of SMTs associated with lower SOI (higher IOD) values. This study is helpful in inspiring more detailed analysis of the relationship between SMTs and extreme precipitation events over India.
  • Problems in calculating long-term trends in the upper atmosphere
    • Abstract: Publication date: Available online 22 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): J. Laštovička, Š. Jelínek Anthropogenic polluting substances, mainly CO2, affect the lower atmosphere where they excite the well-known greenhouse warming. However, they also affect the upper atmosphere (mesosphere, thermosphere and embedded ionosphere), where they cause long-term trends stronger than those in the troposphere. Calculations of long-term trends in the upper atmosphere suffer from various problems, which may be divided into three groups: (1) natural variability, (2) data problems, and (3) methodology. These problems have often been underestimated in trend calculations, which lead to controversial trend results. Here we briefly treat various problems of long-term trend calculations in the upper atmosphere and some ways how to deal with these problems are suggested.
  • A global assessment of ray-traced and blind tropospheric models in the
           retrieval of tropospheric parameters from ground-based GPS observations
    • Abstract: Publication date: Available online 22 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Qiuying Guo, Xuxiang Wu The number of ground-based GNSS reference stations has increased significantly in recent years, which provides very favorable conditions for ZTD/ZWD retrieval. The methods of estimating ZTD/ZWD based on three a-priori troposphere values are discussed using GNSS reference stations without meteorological equipments. GPS observation data for two weeks in different seasons from 22 global IGS stations were processed using online GAPS software with static and kinematic PPP mode based on ECMWF grid product and GPT2.1w/UNB3m blind tropospheric models. Vienna Mapping Function 1 (VMF1) is used for all the a-priori models. The numerical results show that: compared with the IGS ZTD products, mm-level and about 2 cm-level ZTD products can be obtained based on the three a-priori troposphere values using static PPP and kinematic PPP respectively. About 1 cm-level and 2 cm-level ZWD products can be obtained based on ECMWF grid product/GPT2.1w model using static PPP and kinematic PPP respectively. The discrepancy between the ZTD estimates based on the three a-priori troposphere values is no more than 3 mm, and the differences of the averaged ZTD Mbias, RMSE and Std of the 22 IGS stations based on the three a-priori troposphere values are no more than 0.3 mm. While there is obvious differences in ZWD estimates based on the three a-priori troposphere values. The differences of the averaged ZWD Mbias/RMSE between ECMWF grid product and GPT2.1w model is about 0.2 cm, and the differences of the averaged ZWD Mbias/RMSE between ECMWF grid product and UNB3m model are about 0.5–1 cm. There is a systematic bias of about ±1 cm between the ZWD estimates based on GPT2.1w and UNB3m. This study shows that GNSS PPP technology based on ECMWF grid product and blind tropospheric model has great potential for ZTD/ZWD retrieval using ground-based GNSS reference stations.
  • Examining the influence of current waveform on the lightning
           electromagnetic field at the altitude of halo formation
    • Abstract: Publication date: Available online 20 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Huan Ren, Ye Tian, Gaopeng Lu, Yunfeng Zhang, Yanfeng Fan, Rubin Jiang, Mingyuan Liu, Dongshuai Li, Xiao Li, Xiushu Qie In this paper, we extend the analysis of Lu (2006)Lu (2006) to calculate the electric field (E-field) of lightning return stroke in the region of sprite initiation and halos using a transmission line (TL) model that uses various lightning stroke currents measured during the triggered lightning experiment as the driving source to examine the individual components (i.e., electrostatic, induction, and radiation) of E-field perturbation. As the altitude increases, the maximum strength of electrostatic and induction field gradually decreases, and the induction field decays slower than electrostatic field above 80 km. The electrostatic and induction field in the region of halo formation have a much larger contribution to the total E-field than the radiation field. Therefore, it is proposed that in addition to the electrostatic field, the induction field (with amplitude more than half of total E-field) is the main component of the total E-field within the first half millisecond directly above the stroke. Our analysis indicates that the induction field might play a significant role in the halo formation and probably also the sprite initiation. The M-component, the longer rising edge, the wavy long tail, and the relatively long time scale of stroke current can increase the amplitude of electrostatic and induction field at the height of halos, and drive the occurrence of halos and the subsequent development of streamers, therefore forming sprites. Our results enrich the understanding on the mechanism of halo production and the lightning electromagnetic field in the middle and high-altitude atmosphere, and also pave the way for future accurate modeling of halo formation.
  • The structure of equidistant-frequency groups in the oscillation spectra
           of the dayside magnetosphere
    • Abstract: Publication date: Available online 17 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): A.R. Polyakov The structure of natural signals (geomagnetic field disturbances in the ULF range registered at Mondy and Borok observatories) is studied for the first time by means of the APCF (amplitude and phase correlation function) method, unrelated to spectral analysis but based on analysing a specially constructed correlation function of the amplitude and phase fluctuations in the recorded signal. This method can detect the presence of a group of equidistant frequencies in the spectrum of the original signal as well as measuring the difference, Δf, of two adjacent frequencies in the group. The end product of the APCF method is a histogram of multiple Δf values. In the traditional spectral method of signal analysis, the presence in the spectrum of a peak at a certain frequency means that, in the original signal, the oscillation amplitude has a local maximum at this frequency. In the APCF “spectrum” (histogram), each peak corresponds, not to one, but to a whole group of equidistant frequencies in the original signal. The position of the peak on the horizontal axis defines, not a specific frequency, but the difference of two adjacent frequencies which is typical of the entire group.Comparison of one of the histograms for ULF disturbance records with the traditional spectrum shows that the chaotic spectrum, which is generally assumed to be noise, in reality possesses a strictly ordered structure. Most spectral peaks have been found to belong to one of many (more than 10) equidistant frequency groups. In the full spectrum, the peaks of these groups overlap forming a complex chaotic sequence.The analysis of the peaks in all the hist ograms makes it possible to conclude that the equidistant frequency groups corresponding to peaks in each histogram, are eigenfrequencies of a 2D Alfvén resonator. The existence of such a resonator in the magnetosphere, in the vicinity of the plasmapause outer edge, was earlier predicted in theoretical studies [Guglielmi, Polyakov, 1983; Leonovich, Mazur, 1987]. The APCF processing method allows this prediction to be confirmed experimentally.
  • On the role of F3 layers as well as solar flux in modulating the topside
           ionization over Indian region: An analysis
    • Abstract: Publication date: Available online 10 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): N. Mridula, Pant Tarun Kumar, G. Manju, K.V. Subrahmanyam, K. Kishore Kumar The behavior of ionization in the topside ionosphere above F region peak is quite different from the lower ionosphere owing to the diverse processes operational there. This paper presents a comprehensive study on the topside ionosphere and brings out the role of F3 layers as well as increase in solar flux in modulating the topside ionization. Data used comprises of the electron density obtained from COSMIC satellite for the period 2007 to 2012 as well as RaBIT tomograms for the period May to December 2011. This study clearly shows that the ionization in the height region of 300 km–400 km is affected by the presence of F3 layer while above 450 km ionization is not significantly altered by the formation of F3 layer during the solar minimum period. The important factor which affects topside ionization above this altitude is the solar flux. The present study has generated an empirical relationship between the topside electron density and F10.7 cm solar flux during the rising phase of solar cycle 24. This empirical relationship is compared using tomographic observations obtained from RaBIT (Radio Beacon for Ionospheric Tomography) data over Indian region.
  • Sensitivity to solar activity of the Northern Hemisphere warming for the
           years 1980–2500
    • Abstract: Publication date: Available online 9 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Blanca Mendoza, Víctor M. Mendoza, René Garduño, Marni Pazos We used a thermodynamic climate model to compute the Northern Hemisphere temperature anomaly for the period 1980–2500. We obtained temperature anomalies for the ocean, the combined ocean-land area and the land. Two IPCC et al. (2007) CO2 concentration scenarios were considered, the high RCP8.5 and the low RCP4.5, we also included two estimates of the Total Solar Irradiance (TSI). We found that in the RCP8.5 scenario the effect of the TSI is to prevent the temperature for having a runaway behavior after the year 2240, that otherwise it would have due to the high CO2 emission; it is the TSI that makes the temperature anomalies to have an inflection and start decreasing. For the RCP4.5 scenario, without the solar effect, the temperature anomaly after 2075 presents an inflection and becomes constant after the year 2120, but the temperature anomaly has a clear decreasing trend when including the TSI. The TSI presents three future secular minima in the studied period. They introduce only perturbations on the general decreasing trend. The land presents the largest temperature anomalies as well as the most prominent changes, followed by the land-ocean and the ocean. We concluded that the TSI has a fundamental role in the temperature behavior over the long-term.
  • A new theory for the expansion of lightning channels from a diameter of
           centimetres to metres via ionizing waves
    • Abstract: Publication date: Available online 8 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): R. Morrow A new theory is presented for the process whereby an initial 2 cm diameter lightning channel can expand to a channel with a diameter of 1–10 m. The expansion occurs via an ionizing wave over the circumference of the entire channel and along its length. Such a wave is shown in one case to expand the channel to a diameter of 3 m in 3 μs. This ionizing wave is a newly described phenomenon that is quite different from the previous model with multiple filamentary streamers. The old electrical corona theory, and the term ‘corona sheath’, are shown to be inappropriate. All that is required is: (a) a hot, high-density, narrow plasma channel with a net positive charge, and (b) for the lightning stroke current to reduce or pause for a few microseconds. The generation of an ionizing wave is described using continuity equations coupled with Poisson's equation to solve for positive ion, negative ion and electron densities. The light output from positive ion neutralization cannot account for the luminosity of the expanded channel, and another new theory is proposed involving the channel illumination caused by a secondary stroke passing through the body of the broader channel. The continuity of current for the lightning channel explains the general uniformity of the diameter of the broad lightning channel by creating the same initial plasma conditions along its length, triggering a similar ionizing wave. Such processes are suggested to occur in leader channels as they propagate. It is shown that theories which propose that the lightning channel current decreases with altitude are incorrect and violate Maxwell's Equations. Further, theories which propose that radial charge movement contributes to the axial current are also incorrect, as shown by the application of the Morrow Sato Equation.
  • Cosmic ray − global lightning causality
    • Abstract: Publication date: Available online 8 April 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): O. Okike, A.E. Umahi Many atmospheric processes such as atmospheric ionization, cloudiness, temperature and terrestrial lightning have been attributed to galactic cosmic rays (GCRs) hitting the Earth's atmosphere. While some of these theories linking cosmic rays with Earth's geophysical phenomena have been well addressed with empirical results, there are a lot of open fields in the GCR-lightning hypothesis. Some authors have, for instance, investigated the proposal using regional lightning data (Chronis, 2009). The present study uses global lightning data from the world-wide lightning location network (WWLLN) to test the claim that GCRs are responsible for Earth's atmospheric lightning. Regression and superposed epoch analyses are both employed in this investigation. We conclude that the results are consistent with a causal role of GCRs in lightning strikes.
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