Journal of Atmospheric and Solar-Terrestrial Physics

Fair-weather potential gradient and its coupling with ionospheric potential from three Antarctic stations: Case studies

Thu, 02/14/2019 - 19:10

Publication date: March 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 184

Author(s): N.Jeni Victor, Devendraa Siingh, C. Panneerselvam, P. Elango, V.S. Samy

Abstract

Simultaneous measurements of potential gradient (PG) from Antarctica stations, Vostok (78° 27′ S, 106° 52′ E), Dome C (75° 06′ S, 123° 20′ E) and Maitri (70° 45′ S, 11°44′ E) during magnetically disturbed days under fair-weather conditions are discussed. An attempt has been made to study the influence of solar wind-magnetosphere interaction on PG. During magnetic daytime (0600–1800 UT), linear relation between ΔPG and associated ionospheric potential from Dome C and Vostok are observed. The liner response is poor during the magnetic night time (1800-0600 UT). This trend has been addressed by the sun-aligned two-cell plasma convection flow and its differential motion over the stations. It is found that linear relation decreased when negative convection pattern moves towards, overhead and away from the stations under dawnward motion of plasma (IMF By < 0). In addition, the ionospheric potential at dusk sector modulated the PG if the plasma flow remained stable for more than 1 h. The results further showed that the scale size factor between ionospheric potential and PG may influence up to some extent in coupling efficiency. Month-wise Fair-weather PG pattern effectively accounts the ambient PG variation.

Observations of conjugated ring current auroras at subauroral latitudes

Thu, 02/14/2019 - 19:10

Publication date: March 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 184

Author(s): Yongliang Zhang, Larry J. Paxton

Abstract

We report three ring current aurora events that are conjugated in the two hemispheres observed by satellite and ground imagers on May 16, 2005, August 26, 2018 and September 5, 2005. The ring current auroras appeared as auroral spots or arcs in the day, dusk or night side. These events confirm that the particle sources are in the equatorial ring current ions and pitch angle diffusion of the ions lead to the ion precipitation in the both hemisphere on the same field lines, thus the auroras are conjugated.

A global atmospheric electricity monitoring network for climate and geophysical research

Thu, 02/14/2019 - 19:10

Publication date: March 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 184

Author(s): K.A. Nicoll, R.G. Harrison, V. Barta, J. Bor, R. Brugge, A. Chillingarian, J. Chum, A.K. Georgoulias, A. Guha, K. Kourtidis, M. Kubicki, E. Mareev, J. Matthews, H. Mkrtchyan, A. Odzimek, J.-P. Raulin, D. Robert, H.G. Silva, J. Tacza, Y. Yair

Abstract

The Global atmospheric Electric Circuit (GEC) is a fundamental coupling network of the climate system connecting electrically disturbed weather regions with fair weather regions across the planet. The GEC sustains the fair weather electric field (or potential gradient, PG) which is present globally and can be measured routinely at the surface using durable instrumentation such as modern electric field mills, which are now widely deployed internationally. In contrast to lightning or magnetic fields, fair weather PG cannot be measured remotely. Despite the existence of many PG datasets (both contemporary and historical), few attempts have been made to coordinate and integrate these fragmented surface measurements within a global framework. Such a synthesis is important in order to fully study major influences on the GEC such as climate variations and space weather effects, as well as more local atmospheric electrical processes such as cloud electrification, lightning initiation, and dust and aerosol charging.

The GloCAEM (Global Coordination of Atmospheric Electricity Measurements) project has brought together experts in atmospheric electricity to make the first steps towards an effective global network for atmospheric electricity monitoring, which will provide data in near real time. Data from all sites are available in identically-formatted files, at both 1 s and 1 min temporal resolution, along with meteorological data (wherever available) for ease of interpretation of electrical measurements. This work describes the details of the GloCAEM database and presents what is likely to be the largest single analysis of PG data performed from multiple datasets at geographically distinct locations. Analysis of the diurnal variation in PG from all 17 GloCAEM sites demonstrates that the majority of sites show two daily maxima, characteristic of local influences on the PG, such as the sunrise effect. Data analysis methods to minimise such effects are presented and recommendations provided on the most suitable GloCAEM sites for the study of various scientific phenomena. The use of the dataset for further understanding of the GEC is also demonstrated, in particular for more detailed characterization of day-to-day global circuit variability. Such coordinated effort enables deeper insight into PG phenomenology which goes beyond single-location PG measurements, providing a simple measurement of global thunderstorm variability on a day-to-day timescale. The creation of the GloCAEM database is likely to enable much more effective study of atmospheric electricity variables than has ever been possible before, which will improve our understanding of the role of atmospheric electricity in the complex processes underlying weather and climate.

Editorial Board

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s):

Climatological analysis of the optical properties of aerosols and their direct radiative forcing in the Middle East

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): Maryam Gharibzadeh, Khan Alam, Yousefali Abedini, Abbasali Aliakbari Bidokhti, Amir Masoumi, Humera Bibi, Bahadar Zeb

Abstract

In addition to climate perturbations, various problems such as air pollution, reduction in the visibility and human health hazards were caused by atmospheric aerosols in the Middle East specifically in the last two decades. With the help of the Aerosol Robotic NETwork (AERONET), the measurement of the aerosol optical and radiative properties were carried out over seven sites in the Middle East during 2013. The analysis of the optical properties of aerosols like Single Scattering Albedo (SSA), Angstrom Exponent (AE), Aerosol Optical Depth (AOD), and Asymmetry parameter (ASY) were carried out during the study period. During spring and summer, high values of AOD and low values of AE were found in all sites except CUT-TEPAK (Limassol, Cyprus), which specified the existence of coarse mode particles and dust storms in these seasons. The AE maximum values were found in the summer and fall over CUT-TEPAK and IMS-METU-ERDEMLI(Erdemli, Turkey), whereas in other sites IASBS (Zanjan, Iran), KAUST Campus (Thuwal, Saudi Arabia), Masdar Institute (Masdar, United Arab Emirates), Mezaira (Mezaira, United Arab Emirates) and Solar Village (Riyadh, Saudi Arabia) the peak values of AE occurred in the fall and winter. The maximum values of SSA and ASY were observed in the spring and summer over all sites except over CUT-TEPAK and IMS-METU-ERDEMLI. The Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model has been used for the calculations of the Aerosol Radiative Forcing (ARF) over the selected sites. We obtained negative value of ARF at the surface, which suggesting its cooling effects because of the loss of radiation back to space due to aerosols. The averaged ARF values at the SuRFace (SRF) of the earth were −43.8 Wm-2, -31 Wm-2, -56.8 Wm-2, -61.7 Wm-2, -52.5 Wm-2, -54.9 Wm-2, and -72.2 Wm-2, over CUT-TEPAK, IASABS, IMS-METU-ERDEMLI, KAUST Campus, Masdar Institute, Mezaira and Solar Village, respectively. While the positive value of atmospheric ARF showed heating of the atmosphere.

Thunderstorm generators operating as voltage sources in global electric circuit models

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): Nikolay N. Slyunyaev, Alexey V. Kalinin, Evgeny A. Mareev

Abstract

The description of global electric circuit (GEC) generators in continuous numerical models is analysed and discussed. It is shown that voltage-source generators, sometimes employed in simple lumped-element GEC models, have a consistent generalisation in continuous GEC models: just as current-source generators generalise to source current density distributions, voltage-source generators generalise to distributions of the relative potential on cloud boundaries. The difference between non-ideal and ideal current or voltage sources is investigated for both lumped-element and continuous GEC models. As in modern three-dimensional GEC models the formal generalisation of voltage-source thunderstorms turns out to be difficult to implement, two alternative approaches involving the replacement of voltage-source generators with equivalent current-source generators are developed. One approach is based upon a rough estimation of the source current producing the same contribution to the GEC as the original voltage source; the other approach uses the fact that each voltage-source generator can be shown to be a limiting case of a certain current-source generator with increased conductivity. For the first time voltage-source generators are implemented in a numerical GEC model (using both the direct generalisation and the suggested alternative approaches).

A comparative study on the lightning sferics associated with terrestrial gamma-ray flashes observed in Americas and Asia

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): Gaopeng Lu, Hongbo Zhang, Steven A. Cummer, Yongping Wang, Fanchao Lyu, Michael Briggs, Shaolin Xiong, Alfred Chen

Abstract

We examine the broadband (<1 Hz to 400 kHz) electromagnetic lightning signals associated with Terrestrial Gamma-ray Flashes (TGFs) detected by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope during 2010/2011. The TGF-associated lightning sferics are mainly recorded at two stations located near National Cheng-Kung University in Taiwan and near Duke University in the United States, respectively. The general features exhibited by the TGF-associated lightning sferics are consistent with previous findings that gamma-rays in TGFs are typically produced during a slow process that creates a considerable (but not necessarily) charge moment change within several milliseconds. In some cases, this slow process can be attributed to the upward negative leader during the initial stage of normal intra-cloud (IC) lightning, and it is usually punctuated by one or several fast discharges, the major one of which (i.e. TGF-related discharge) is closely involved in the gamma-ray production. The equivalent peak current of TGF-related discharges could be as high as >+500 kA, and the associated charge transfer is also considerable (typically >+20 C km). The observed complexity of TGF-associated lightning emissions can also be interpreted in the context of the initial development of normal IC lightning flashes, where the upward negative leader drives the millisecond-scale current and may also provide the seed electrons for avalanche multiplication in the upper part of active thunderstorms. Our analyses show that the thunderstorms in the land area of South China produce TGFs that can be readily observed by Fermi/GBM, and the future ground-based coordinated observations in this area would be rather promising to gain more insights into the physical mechanism of TGFs.

Investigations of vertical wind variations at a mountain top in the Himalaya using Doppler Lidar observations and model simulations

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): K.K. Shukla, D.V. Phanikumar, Rob K. Newsom, N. Ojha, K. NiranjanKumar, Narendra Singh, Som Sharma, V.R. Kotamarthi, K.K. Kumar

Abstract

Hight-resolved observations of vertical winds remain nearly non-existing over the Himalayas, despite of anticipated crucial role of vertical motions in transporting pollution across the Himalayan hills. The present study analyze the vertical wind observations from surface to 1 km above ground level over Manora Peak (29.4° N; 79.5° E; 1958 m amsl) in the Himalaya performed using a Doppler Lidar during the Ganges Valley Aerosol Experiment (GVAX). Vertical wind exhibited a pronounced diurnal variability at Manora Peak comprising of upward motions during the daytime (05–10 UT) and downward motions during nighttime typical of a mountain-valley system. Mean vertical wind speeds are observed to be varying from −0.8 to +0.8 ms−1 during the study period with a variance of 0.1–1.5 m2s-2, which is attributed to the thermally driven turbulence. Mean vertical winds are observed to be stronger in the Doppler Lidar profiles above Manora Peak (−0.8 to 0.8 ms−1) as compared to near surface measurements at this station using an ultrasonic anemometer (−0.4 to 0.4 ms−1), and low altitude stations in India. Daytime vertical wind speeds are observed to be higher during pre-monsoon (0.81 ms−1), as compared to post-monsoon (0.24 ms−1) and winter (0.33 ms−1). Average Black Carbon (BC) concentrations are significantly higher during strong upward vertical winds, which indicates efficient transport of polluted air mass from low-altitude regions to the Himalaya. Weather Research and Forecasting (WRF) model reproduces the observed diurnal pattern in the vertical wind at the observation site however the model underestimates the variability.

Numerical simulation of the mean meridional circulation in the middle atmosphere at different phases of stratospheric warmings and mountain wave scenarios

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): Andrey V. Koval, Nikolai M. Gavrilov, Alexander I. Pogoreltsev, Ekaterina A. Drobashevskaya

Abstract

In this study, numerical simulations have been performed to estimate the transformation of the mean meridional circulation in altitude range 0–100 km at different phases of simulated stratospheric warming (SW) events in January–February including and excluding impact of mesoscale orographic gravity waves (OGWs). To obtain an ensemble of 12 pairs of model runs with and without a parameterization of OGW effects, the numerical middle and upper atmosphere model (MUAM) has been used. Obtained results demonstrate weakening of the zonal mean meridional circulation at altitudes up to 100 km during and after simulated SWs compared to the time interval before SWs. At altitudes below 50 km, southward mean meridional winds decrease (up to 15%) before and after simulated SWs. OGW effects may increase the mean northward wind at altitudes above 60 km up to 10–15%. The most significant changes of the meridional circulation in the middle atmosphere are detected at the middle and high latitudes of the Northern Hemisphere: the southward meridional circulation increases at altitudes above 40 km and decreases below 40 km. Thus, the global-scale mean meridional circulation in the middle atmosphere may significantly depend on different phases of SW events during the northern winter season. It is also quite sensitive to the dynamical and thermal OGW impacts.

Evaluating MODIS and MISR aerosol optical depth retrievals over environmentally distinct sites in Pakistan

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): Gohar Ali, Yansong Bao, Richard Boiyo, Weiyao Tang, Qifeng Lu, Jinzhong Min

Abstract

The Moderate resolution Imaging SpectroRadiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR) sensors provide aerosol observations suitable for a wide range of applications. The recently released MODIS Collection 6.1 (C061) includes several improvements compared to the previous products which are expected to minimize uncertainties in aerosol retrievals. Such collection needs to be validated and compared with previous collections form the same or other sensors before being applied for further scientific research on a regional scale. This study evaluates the performance of MODIS Collections 6 (C006) and 6.1 (C061) based on two algorithms: Dark Target (DT) and Deep Blue (DB) and the merged product (DTB) onboard the Terra (MOD04) and Aqua (MYD04) satellites, and the MISR AOD retrievals against ground-based Aerosol Robotic Network (AERONET) over two sites (Lahore and Karachi) in Pakistan during 2007–2014. Results elucidated that C061 MODIS AOD exhibited significant improvement as compared to C006, with the 10 km DT (DB) products generally overestimating (underestimating) AOD relative to AERONET AOD. The MOD04 and MYD04-DT and DB (3 and 10 km) showed comparable performance over the two sites, whereas The DTB was dominated by DT (DB) pixels over Lahore (Karachi). The MISR showed better performance over Karachi with high reflecting surface than over Lahore with dense vegetation cover. The annual cycle of AOD retrieved by the two sensors were consistent with AERONET AOD, with maximum AOD observed during summer months attributed to prevailing climatic conditions. On seasonal basis, the MODIS algorithms exhibited improved performance over Lahore except during summer where DT and DTB showed relatively low performance, attributed to modulations induced by local meteorology to the prevailing surface conditions. However, the sensors exhibited distinct performance over Karachi, where MODIS-DT (10 km) showed close correspondence with AERONET during autumn and winter, whereas MODIS-DT (3 km) exhibited the converse. The MISR performed relatively well during spring over the two stations. The study gives greater insights on the performance of MODIS and MISR and forms the basis for further research on the validation of satellite derived aerosol products over Pakistan.

Rapid intensification of tropical cyclones in the context of the solar wind-magnetosphere-ionosphere-atmosphere coupling

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): Paul Prikryl, Lidia Nikitina, Vojto Rušin

Abstract

Rapid intensification of tropical storms is examined in the context of solar wind coupling to the magnetosphere-ionosphere-atmosphere system. Tropical cyclone “best tracks” in the southern and northern hemispheres are used in the superposed epoch analysis of time series of solar wind parameters. The results indicate that rapid intensification of tropical storms tends to follow arrivals of high-speed streams from coronal holes or interplanetary coronal mass ejections, which can trigger geomagnetic storms. The ensuing auroral and polar cap activity including ionospheric currents and ionospheric convection generates atmospheric gravity waves that propagate from the high-latitude lower thermosphere both upward and downward. If ducted in the lower atmosphere, they can reach tropical troposphere. Despite significantly reduced wave amplitudes, but subject to amplification upon reflection in the upper troposphere, these gravity waves can trigger/release moist instabilities to initiate convective bursts, with the latent heat release leading to intensification of storms. Convective bursts have been linked to rapid intensification of tropical cyclones. Cases of tropical cyclone intensification closely correlated with the solar wind structure are found to be preceded by atmospheric gravity waves generated by the solar wind magnetosphere-ionosphere-atmosphere coupling process. The gravity waves are observed in the ionosphere as traveling ionospheric disturbances. Their propagation in the lower atmosphere is examined by ray tracing in a model atmosphere to show that they can reach tropical cyclones. It is suggested that the interaction of aurorally-generated gravity waves with the tropical cyclone vortex and the inner primary eyewall could play a role in the intensification process. Assuming that quasi-periodic convective bursts lead to vortex waves, a two-dimensional barotropic approximation is used to obtain asymptotic solutions representing propagation of vortex waves and their absorption by the mean flow in the critical layer.

High-speed video observations of branching behaviors in downward stepped leaders and upward connecting leaders in negative natural lightning

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): X. Wang, X. Zhao, Y. Hao, H. Cai, G. Liu, M. Liao, L. Qu

Abstract

Branched downward stepped leader (DSL) associated with branched upward connecting leader (UCL) were observed together in one negative natural lightning. Branching behaviors and development scenarios of DSL and UCL have been investigated and compared with high-speed video frame sequence. The optical evidence provides that most of negative leaders exhibit branching tips, with four main branching points produced during propagation. The adjacent faint segments, which are likely the newly created channel sections after two adjacent space leaders have make connection with the leader tip, are simultaneously appeared ahead of negative leader tips; most of them could contribute to the tortuosity of leader channel and only few of them lead to the concurrent branches of channel, with the common root of significantly great luminosity. However, positive leaders normally do not have branched tips, but generating one branching point at early stage of UCL initiation even though the leader channel is rather faint. The two-dimensional (2D) average speeds of five negative branches and the main branch of UCL propagating are quite similar, ranging from 3.56 × 105 m/s to 3.89 × 105 m/s.

Novel W<em>k</em>NN-based technique to improve instantaneous rainfall estimation over the north of Algeria using the multispectral MSG SEVIRI imagery

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): Noureddine Bensafi, Mourad Lazri, Soltane Ameur

Abstract

For the estimation of rainfall in northern Algeria, a new method is proposed in this study. It based on the k nearest weighted neighbours (WkNN) classification algorithm using the dataset from the radiometer-imager SEVIRI (Spinning Enhanced Visible and Infra-Red Imager) boarded on the satellite MSG (Meteosat Second Generation) to determine the pixel rainfall rate among the 16 predefined intensity levels observed in the Sétif meteorological radar.

The implementation of the classification consists in using the spectral characteristics of a new sample (pixel) as input variables of the WkNN classifier to predict his class of membership based on the weighted distances separating him from the samples of the set of learning. The results thus obtained are validated with respect to the rainfall intensity classes observed and co-located by ground radar. The results showed a significant improvement for instantaneous estimate of precipitation during the day, with a correlation coefficient r=0.87 and statistical parameters RMSE=2.29mm/h,Bias=0.45mm/h,MAE=0.35mm/h, and we have obtained the results similar overnight.

Geodetic contribution to predict the seismological activity of the Italian metropolis by the ionospheric variant of GPS_TEC

Wed, 02/06/2019 - 19:10

Publication date: February 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 183

Author(s): Abdennasser Tachema, Abdelmansour Nadji

Abstract

In this paper, we present a predictive approach treating the seismic hazard to detect, through to the geodetic data and the ionospheric total electron content (TEC) Anomalies, the time-origin of the seismic precursors of notable earthquakes (Mw ≥ 5). The main aim of this paper is to show the geo-spatial investigation interest to establish the ionospheric ‘TEC-Mapping’ allowing the monitoring and prediction of spontaneous vibrations of the lithospheric layer. For this purpose, we studied the seismic events that rocked the Italian peninsula (Central Italy, Mw > 6.1, late October 2016), where several IGS geodetic stations surrounding the hypocenter, were exploited to acquire raw data allowing to reconstitute in real time the GPS_TEC signal. As results, the elaborated ‘TEC’ diagram has allowed us to observe significant disturbances in the ionospheric TEC's amplitudes appear near the epicenter, a few days, before the Central Italy earthquake; which are related to the fluctuations of the electron density of the surrounding ionosphere. These anomalies represent the early percussion of seismic vibrations on earth, which truly respond the ternary coupling: Lithosphere-Atmosphere-Ionosphere. We also studied the causes that can disturb the ionosphere in order to distinguish from the pre-earthquake precursors. Finally, we confirmed the efficacy of this geodetic approach, applied in the natural hazards area, which can contribute effectively to the prediction of a significant seismic event in a given region.

ULF electromagnetic noise from regional lightning activity: Model and observations

Sun, 01/13/2019 - 19:10

Publication date: January 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 182

Author(s): Nadezda V. Yagova, Ashwini K. Sinha, Vyacheslav A. Pilipenko, Evgeny N. Fedorov, Robert Holzworth, Geeta Vichare

Abstract

Contribution of lightning to geomagnetic field variations in ULF (f<1 Hz) frequency range is estimated within the framework of a simple model of ULF response to lightning strokes. ULF lightning index is introduced to quantify a contribution of lightning to ULF power at observational site. The computed pulse series are compared with the pulse-like interference recorded at the low latitude observatory (KNY). Lightning stroke is modeled as a vertical dipole with the perfectly conducting model ionosphere. A program of automatic detection of pulse-like interference in recorded signal is developed. The analysis of the time series of hourly ULF lightning index at KNY during several weeks in summer of 2012 has shown that the contribution of thunderstorms to ULF power may be significant, especially at frequencies f>80 mHz. This effect should be taken into account in any application utilizing estimates of local ULF power including seismo-electromagnetics.

Analysis of a dense haze event over North-eastern Pakistan using WRF-Chem model and remote sensing

Sun, 01/13/2019 - 19:10

Publication date: January 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 182

Author(s): Muhammad Zeeshaan Shahid, Imran Shahid, Farrukh Chishtie, Muhammad Imran Shahzad, Gufran Bulbul

Abstract

Urban areas in Pakistan are experiencing escalation in haze episodes. Due to increase in economy, emissions of gaseous and aerosol components from automobiles, road constructions and industry is growing in Pakistan which has resulted in worsening air quality during winter and post-monsoon season. North Eastern (NE) Pakistan (71–74.5°E, 28–34°N) is experiencing haze and fog episodes because of the increase in aerosol pollution levels. In addition to anthropogenic emissions, winter pollution over NE Pakistan is associated with unfavourable meteorological conditions. Lahore, a metropolitan city in NE Pakistan experienced a dense haze event during the first week of November 2016. In this article, we examine the pollution levels before, during and after this heavily polluted episode in NE Pakistan based on model simulations and remote sensing data. In particular, the Weather Research Forecasting model coupled with chemistry (WRF-Chem) and pertinent satellite data from MODIS are utilized towards validation. Another goal of this study is to characterize sources and causes of this haze event especially over Lahore. Particulate matter concentrations, AOD, and concentration of gaseous components increased many folds than the usual levels. Additionally, Vertical Feature Mask (VFM) results are presented from measurements by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite revealing vertical layers of aerosol of thickness ranging from 2 to 5 km in the study region and period.

Solar variability manifestations in weather and climate characteristics

Sun, 01/13/2019 - 19:10

Publication date: January 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 182

Author(s): G.A. Zherebtsov, V.A. Kovalenko, S.I. Molodykh, K.E. Kirichenko

Abstract

We discuss the issues of primary importance to understand the nature of climate changes in the 20th century and main physical processes responsible for these changes and present a physical model for the solar activity (SA) effect on climate characteristics. A key concept of this model is the heliogeophysical disturbance effect on the Earth climate system parameters driving the long-wave radiation flux moving away from the Earth out into space in high-latitude regions. We address the solar activity effect on the changes in the temperature of the atmosphere and of the World Ocean. The aa–index of the geomagnetic activity (GA) was used as an SA proxy index. We discuss the results of analyzing the regularities and peculiarities of the tropospheric and sea surface temperature (SST) responses to both separate heliogeophysical disturbances and long-term changes in solar and geomagnetic activity. The structure of the tropospheric and SST temperature responses was shown to feature a spatial time irregularity. We revealed the regions, where long-term SST changes are determined mainly by SA variations.

<em>PC</em> index as a proxy of the solar wind energy that entered into the magnetosphere: 4. Relationship between the solar wind dynamic pressure (P<sub>SW</sub>) impulses and <em>PC, AL</em> indices

Sun, 01/13/2019 - 19:10

Publication date: January 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 182

Author(s): O.A. Troshichev, D.A. Sormakov

Abstract

The solar wind dynamic pressure (PSW) impulses impacting on the magnetosphere were separated on the basis of solar wind parameters measured in the point of libration L1 in 1998–2017. Comparison of the “estimated” PSW impulses reduced to the Earth's magnetopause with the appropriate sudden impulses (SI), revealed in the ground-based 1-min SymH index, showed that features of the really observed sudden impulses (moment of beginning, time evolution, intensity) can be significantly different from characteristics of the estimated PSW impulses. Because of this the preference was given to the real SI events over the estimated PSW impulses. Only the events with sudden impulses starting against the background of steady quiet pressure levels were taken for the analysis (N = 143). Relationship between the positive (leaps) and negative (drops) SI events, on the one hand, and PC and AL indices, on the other hand, were examined under the various solar wind conditions, such as: growing and steady solar wind speed at negative and positive values of the IMF BZ component, fluctuating BZ and solar wind speed, steady solar wind speed and BZ = 0. Analysis of SI events showed that the solar wind dynamic pressure impulses themselves are not promote (or insignificantly promote) the solar wind energy input into the magnetosphere, which is controlled by the interplanetary electric field EKL = Vsw*(BY2+BZ2)1/2 and is displayed by the polar cap magnetic activity PC index. When the PSW impulses (leaps or drops) are accompanied by the corresponding changes in EKL field, the PC index correlates (increases or decreases) with the PSW changes. Inconsistency between the PSW and PC behavior becomes evident as soon as the EKL and PSW courses start to diverge. Development of magnetic disturbances (AL index) is governed only by the EKL field and PC index increase irrespective of the PSW impulses magnitude and time evolution.

Generalized Schumann and variation moment methods used for the determination of the equatorward boundary of the ultra-energetic relativistic electron precipitations into the auroral middle atmosphere

Sun, 01/13/2019 - 19:10

Publication date: January 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 182

Author(s): George F. Remenets, Aleksandr M. Astafiev

Abstract

In this paper, we present (i) the comparison of a solution accuracy of an inverse VLF problem for very low frequency (VLF) wave propagation (10–16 kHz) in the “Earth – sporadic Ds layer of atmosphere ionization” as estimated by three different methods of eiganvalue calculation and (ii) an estimation of latitude uncertainty for the equatorward (southern) boundary of Ultra-energetic Relativistic Electron (URE) precipitations into the middle polar atmosphere. The uncertainty for 1982–1987 years was caused by the different years, seasons, months, hours of daytime and electric conductivities of ground surface.

Sporadic Ds layer was caused by the URE precipitations with the electron energies about 100 MeV into the polar region of atmosphere with a geographical latitude range 63–67 N degrees. The results of application of new accurate generalized Schumann (GS) method and of the approximate variation moment (VM) method used for an eigenvalue problem were compared with the results of another accurate method in which the Ricatti nonlinear equation (RNLE) was used. Comparison has been performed for the values of one (main) eigenvalue of a transversal operator for the corresponding model waveguide and for the determined positions of the URE precipitation equatorward boundary, the eigenvalue was being a function of the disturbance time. This comparison provides an estimation which method is preferable during simultaneous observations and analysis of a geophysical disturbance.

In the second part of the study, the influence of the electrical conductivity in the waveguide model on the accuracy of equatorward boundary determination for the 16 kHz radio path “England – Kola peninsula” was analyzed, based on the data from the fixed location of two sources (in North Norway and in England) and a receiver (on Kola Peninsula) of the radio signal. It was shown that the uncertainty introduced by different values of the ground conductivity was 2–3 times less than the differences in the boundary position between different events under study.

Proton-electron model of ball lightning structure

Sun, 01/13/2019 - 19:10

Publication date: January 2019

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 182

Author(s): Alexander G. Oreshko, Anna A. Oreshko, Timur B. Mavlyudov

Abstract

Experiments were performed in which the decay of the ion nuclei as a result of the nuclear photoeffect has been detected during generating of a ball lightning. The decay of the ion nuclei was accompanied by a neutrons burst, with the magnitude exceeding the level of the natural neutrons background in absence of the ball lightning. The measured value of the potential of the ball lightning after its formation was within 15–20 MV. High values of potential lead to the conclusion that nuclear photoeffect is the single possible cause of neutron emission in the stage of ball lightning generation. Due to presence of the charge, the protons remain in the external spherical shell of the ball lightning under the influence of its electric and magnetic fields. Neutrons leave the region of the ball lightning generation due to diffusion. Proton-electron model of ball lightning is created. Ball lightning is an electrical domain of spherical shape, which external spherical shell mainly consists of high-energy protons whereas the kernel consists of electrons.

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