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Journal of Atmospheric and Solar-Terrestrial Physics
Journal Prestige (SJR): 0.696
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1364-6826
Published by Elsevier Homepage  [3183 journals]
  • On the latitudinal variation of the semiannual oscillation in received
           solar radiation and temperature
    • Abstract: Publication date: Available online 8 August 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): J.M. Picone, J. Lean, M. Jones, R.R. Meier This paper characterizes the semiannual oscillation (SAO) in the received solar radiation (RSR) as a function of latitude for Earth, as a paradigm of a planet with an inclined rotational axis, and studies atmospheric implications. The latitude variations of the RSR SAO amplitude and phase are complex yet systematic. To investigate atmospheric response to the SAO in received solar radiation, we focus on Earth, examining monthly average surface temperature data over a wide latitude range. The latitude variation of surface temperature SAO amplitude and phase show marked similarity to those of the RSR - possible evidence of a residual RSR footprint in the atmospheric temperature and conflicting with current empirical representations of zonal temperature SAO phase and amplitude. For RSR and surface temperature as functions of latitude: (1) properties of SAO are independent of orbital eccentricity, which contributes only a constant global component to local annual oscillation (AO); (2) SAO peaks near equinox at lower latitudes and near solstices at higher latitudes, transitioning in phase over 40° − 60° latitude; and (3) SAO strengths (amplitude relative to local AO amplitude) of RSR and surface temperature are largest near the poles and equator. Also discussed is the presence of SAO in the global average surface temperature while SAO is negligible in the global average RSR. The approximate altitude independence of latitude variations in RSR SAO and the similarity of local surface temperature SAO suggest investigation of a simplified working hypothesis of similar behavior of observed local temperature SAO at higher altitude.
       
  • Validation of water vapor measured by SABER on the TIMED satellite
    • Abstract: Publication date: Available online 31 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Pingping Rong, James M. Russell, Benjamin T. Marshall, Larry L. Gordley, Martin G. Mlynczak, Kaley A. Walker The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) measured water vapor (H2O) had errors of unknown origin that were recently identified and corrected. The cause of the errors was determined to be unaccounted for spectral out-of-band (OOB) radiance in the H2O channel centered at 6.8 μm arising from ozone emission in the 9.6 μm band. The corrected SABER radiance profiles have been used to produce a long-term H2O data base labeled as version 2.07 (v2.07). Water vapor volume mixing ratio (VMR) vertical profiles are available in the SABER data archive covering the stratosphere and mesosphere extending from near the tropopause at ∼100 hPa (∼16 km) to the mesopause region at ∼ 0.006 hPa (∼83 km), and over the time period from 25 January 25, 2002 to the present day. The random error of the v2.07 product is smaller than 4% at 60 km and below, while above this altitude it rapidly increases to 30% (at 80 km), mainly due to low signal-to-noise. The estimated systematic error of SABER v2.07 H2O is about 10–20%. Coincidence analysis between SABER v2.07, MLS v4.2, ACE v3.5-3.6, MIPAS ESA reprocessed v6, and SOFIE v1.3 shows overall excellent agreement in the mean profile with the mean difference being within ±10% in most cases. In the stratopause region SABER H2O tends to be biased high relative to each of the other data sets used for comparisons especially in the SH polar winter where the mean difference reaches 20% or greater. In polar summer above 80 km, SABER H2O is biased low by ∼20% compared to the other measurements. SABER H2O therefore reflects the polar winter and spring descent very well but in the summer PMC region the enhancement is weaker than expected. SABER H2O long-term series in the latitude range 50°S-50°N shows close agreement with MLS on a series of pressure levels throughout the stratosphere and mesosphere on inter-annual to decadal time scales. On these time scales also, throughout the years 2002–2005, SABER and MIPAS long-term time series agree well in the equatorial region which serves as an unprecedented validation for this time period. SABER H2O also captures the “tape recorder” phenomenon in the tropical tropopause region very well.
       
  • Scattering of ELF radio waves by a localized non-uniformity in the lower
           ionosphere
    • Abstract: Publication date: Available online 31 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Yuri P. Galuk, Irina G. Kudintseva, Alexander P. Nickolaenko, Masashi Hayakawa We numerically model the ELF radio wave scattering by a localized non-uniformity in the mesosphere conductivity characterized by a 25–30 km reduction of conventional profile from 70 to 80 km altitude. The disturbance is axially symmetric; it depends on the radius according to the Gaussian law of 1 Mm scale. The complex characteristic electric and magnetic heights are found by solving the Riccati equation. These heights are used in the 2D (two dimensional) telegraph equations (2DTE) when computing the ELF fields in the Earth–ionosphere cavity. The field source is located at the point (10° S; 0° E), the non-uniformity is positioned above the North Pole, and the observer moves across the entire surface of the Earth. Spatial distributions were computed of the vertical electric field amplitude in both regular and non-uniform cavity. Comparison of these data allowed us to single out the reflections from the localized non-uniformity. It is shown that interference takes place at an arbitrary observation point between direct wave and the wave reflected from the non-uniformity. Computational data might be interpreted by secondary currents induced in the non-uniformity by the incident radio wave. There are two types of secondary sources. The first one is a “monopole” radiating symmetrically in all directions. Spatial distribution of the field from this source coincides with the distribution of corresponding Schumann resonance mode at a particular frequency. The other secondary source is of “dipole” type, which has a cosine radiation pattern with the maximum oriented along the source – non-uniformity line. Its spatial distribution coincides with the derivative of the corresponding Schumann resonance mode eigen-function on the distance. Model data obtained will facilitate interpretation of experimentally observed seismogenic Schumann resonance signals.
       
  • Multiple Airglow Chemistry approach for atomic oxygen retrievals on the
           basis of in  situ nightglow emissions
    • Abstract: Publication date: Available online 30 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Olexandr Lednyts’kyy, Christian von Savigny, Miriam Sinnhuber, Naomoto Iwagami, Martin Mlynczak Electronically excited states of molecular and atomic oxygen (O2 and O) are coupled with each other as well as with the ground states of O2 and O in the Multiple Airglow Chemistry (MAC) model representing the oxygen airglow and the oxygen photochemistry in the upper Mesosphere and Lower Thermosphere region. The MAC model couples seven O2 and three O states and was developed on the basis of in situ measurements from the ETON (Energy Transfer in the Oxygen Nightglow) campaign employed to tune rate values of unknown or poorly constrained processes. The same rate values are applied in the MAC model verified and validated on the basis of the in situ measurements obtained during the WADIS-2 (WAve propagation and DISsipation in the middle atmosphere), the WAVE2000 (WAVes in airglow structures Experiment, 2000) and WAVE2004 campaigns. Data sets measured using devices aboard the WADIS-2 rocket are considered to be self-consistent because the MAC retrievals of a concentration profile of O in the ground state ([O(3P)]) can be based on these data sets only. The measuring sites of the in situ data sets from the WAVE2000 and WAVE2004 campaigns are collocated with those of remotely obtained data sets, and these data sets are combined for the MAC retrievals. O2 precursors responsible for the oxygen green line emission, emissions in the Atmospheric band and the Infrared Atmospheric band are identified and confirmed by calculations with the validated MAC model.
       
  • New hiss and chorus waves diffusion coefficient parameterizations from the
           Van Allen Probes and their effect on long-term relativistic electron
           radiation-belt VERB simulations
    • Abstract: Publication date: Available online 24 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Hui Zhu, Yuri Y. Shprits, M. Spasojevic, Alexander Y. Drozdov New wave frequency and amplitude models for the nightside and dayside chorus waves are built based on measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument onboard the Van Allen Probes. The corresponding 3D diffusion coefficients are systematically obtained. Compared with previous commonly-used (typical) parameterizations, the new parameterizations result in differences in diffusion rates that depend on the energy and pitch angle. Furthermore, one-year 3D diffusive simulations are performed using the Versatile Electron Radiation Belt (VERB) code. Both typical and new wave parameterizations simulation results are in a good agreement with observations at 0.9 MeV. However, the new parameterizations for nightside chorus better reproduce the observed electron fluxes. These parameterizations will be incorporated into future modeling efforts.
       
  • Morphologies of the topside ionosphere observed by COSMIC at
           high-latitudes during the 17 March 2013 magnetic storm
    • Abstract: Publication date: Available online 19 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Pei Chen Lai, William J. Burke The present study considers effects on the topside ionosphere at high-latitude ( MLat  ≥ 60°) during the magnetic storm on 17 March 2013. We divide the day into two segments, with magnetic conditions quiet during the first 6 h and disturbed thereafter, thus allowing comparisons of differences between these two states. The COSMIC data source consisted of 272 electron density profiles (EDPs) measured by COSMIC satellites using Abel inversions that assume the absence of horizontal plasma density gradients. We compared resultant EDPs with predictions of the International; Reference Ionosphere (IRI) model for the same altitudes along individual tangent-point lines. As conditions allowed, we also compared EDPs with densities measured by nearby DMSP satellites. During the pre-storm quiet period, 65 of the sampled 68 EDPs were highly correlated with IRI predictions. The remaining 3 EDPs showed significant irregularities along parts of the 800–200 km altitude range. We divided stormtime 204 COSMIC EDPs into three morphological categories. In the first group, 130 EDPs exhibit shapes similar to IRI-predictions. Of these, 72 (9) had larger (smaller) than predicted magnitudes. The second group consisted of 37 EDPs that showed little variation in magnitude over the designated altitude range. The remaining group had another 37 EDPs marked by significant irregularities. We found that the deepest EDP irregularity resulted from GPS signals passing through a deep plasma density trough observed by DMSP. The trough extended along the equatorward boundary of the evening-side, auroral oval. We suggest that EDP irregularities reflect density gradients along or near EDP tangent point lines.
       
  • A rapid identification and warning method for severe weather via Doppler
           radar based on an improved TITAN algorithm
    • Abstract: Publication date: Available online 19 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Lei Wang, Hao Wang, Zhiwei Heng An adaptive fast-recognition warning algorithm for severe weather using ground-based Doppler radar and Tropical Rainfall Measuring Mission (TRMM) sensor data is proposed for different seasons, regions and topography conditions in the East and South China Seas. An improved regional segmentation method and the Thunderstorm Identification, Tracking, Analysis and Nowcasting (TITAN) algorithm were applied to identify three-dimensional strong storm cells and their physical features. Multiple logistic linear regression was used to establish a probabilistic warning model for strong convective weather, such as hail and lightning. Doppler radar identification and warning experiments were carried out for a strong squall line near the East China Sea and a supercell storm near the South China Sea. The experimental results showed that the proposed method has higher identification accuracy based on the azimuth and distance than the traditional algorithm. Moreover, the false negative and false report rates of the proposed method are low, which helps to quickly identify and warn against severe weather and protect lives and property.
       
  • Solar activity imprints in tree ring-data from northwestern Russia
    • Abstract: Publication date: Available online 15 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Elena A. Kasatkina, Oleg I. Shumilov, Mauri Timonen The Sun's role in climate variability is now a subject of debates, especially in the context of understanding contribution of solar forcing to modern global warming. Besides, there are some evidences of the approaching new Grand Solar Minimum with Little Ice Age climatic conditions. This expectation is based on the occurrence of the extended solar minimum of 2006–2009. To investigate the possible Sun-climate connection the regional tree-ring chronology covering the period from 1445 to 2005 was analyzed. A total of 36 timber cores of pine Pinus sylvestris L. were sampled near the northern tree-line at Loparskaya station (68.6 N, 33.3 E), including the oldest living pine with more than 560 years of age. The data were processed using modern methods adopted in dendrochronology (cross-dating and standardization) with the help of COFECHA and ARSTAN programs. The analysis revealed significant cooling events, coinciding with the Spoerer (1400–1540), Maunder (1645–1715), Dalton (1790–1830), and Gleissberg (1880–1910) Grand Solar Minima. The application of MTM-spectrum and wavelet decomposition analysis identified the existence of the main cycles of solar activity (5.4, 11.7 and 22 years) in tree-ring width variations. As possible extraterrestrial forcings of climate change we consider here variations in solar irradiance and cosmic ray intensity modulated by the interplanetary magnetic field. As solar and cosmic ray activity indicators we used the annual sunspot number, geomagnetic aa index and Beˆ10 cosmogenic isotope records. To examine the relationship in time-frequency scale between tree-ring growth and solar activity, the cross wavelet transform and wavelet coherence analysis were applied to the time series. The wavelet coherence analysis identified that the 11 yr and 22 yr periodicities were clearly manifested in the all solar-tree rings connections during and around the Grand Minima of solar activity including the Maunder minimum, when, as is known, sunspots were practically absent. These results confirm the existence of solar activity effect on climate and tree growth above the Arctic Circle and are important for understanding the modern climatic processes.
       
  • Numerical study of performance of two lightning prediction methods based
           on: Lightning Potential Index (LPI) and electric POTential difference
           (POT) over Tehran area
    • Abstract: Publication date: Available online 2 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Maryam Gharaylou, Majid M. Farahani, Morteza Hosseini, Alireza Mahmoudian The electric POTential difference (POT) and the Lightning Potential Index (LPI) performance in predicting the lightning activity is investigated and the probable relationship between them is examined. These two indices have a similar dependency on microphysical variables such as ice, graupel mixing ratios, and also updraft characteristics within the cloud. Regardless of this similarity, the LPI directly calculated from WRF model is a more favorable parameter for predicting the lightning events in comparison with the POT, which requires an extra package (ELEC) model. Ten years' available data over the Tehran area were reviewed and four thundercloud cases with distinct characteristics (CAPE, time-frequency, intensity) were selected. In order to acquire the associated physical properties, four simulations have been done using the WRF-ELEC model, which is initialized with ERA-Interim data.The assessment conducted within both quantitative and qualitative themes to verify the potential probability of predicting lightning events. In qualitative evaluation framework, the horizontal distribution of LPI and POT were compared to the locations of lightning occurrence detected by WWLLN (The World Wide Lightning Location Network) data as well as the total lightning data obtained from LIS (Lightning Imaging Sensor) in the innermost simulation domain. This evaluation shows that the horizontal patterns of LPI and POT are well consistent with the locations of lightning occurrence. Moreover, in accordance with acquired values of correlation coefficients, it could be inferred that LPI has a better performance in the Number Of Lightning flashes (NOL) prediction than POT. Statistical review of our simulated data (LPI and POT) is performed to study the variation of LPI and POT which resulted in a good correlation between them and therefore, any information about lightning event using LPI values with less computational cost is preferable in the considered domain. Another comparison was carried out based on the calculated correlation coefficient between the simulated NOL and the NOL recorded by WWLLN that does not show any significant correlation between them for none of the cases. Since WWLLN has no observatory in the studied area, inconsistency of the simulated NOL with real atmosphere is justifiable.
       
  • Middle atmospheric planetary waves in contrasting QBO phases over the
           Indian low latitude region
    • Abstract: Publication date: Available online 2 July 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Kondapalli Niranjan Kumar, Som Kumar Sharma, Vaidehi Joshi, T.K. Ramkumar The present study primarily focused on the characteristics of the planetary scale waves in the middle atmosphere during different phases of Quasi-Biennial Oscillation (QBO), a dominant oscillation in the low-latitude stratospheric region. The temperature profiles retrieved from the Rayleigh lidar measurements have been utilized for the 11 winter periods between 1998 and 2009 over a low-latitude station, Gadanki (13.5oN 79.2oE). The spectral analysis of temperature anomalies indicates two dominant planetary-scale modes, namely, quasi 12-day and quasi 16-day waves. The existence of these waves in the middle atmosphere is strongly controlled by the westerly and easterly phases of QBO. For instance, the 12-day wave is mainly observed in the QBO westerly phase, while the 16-day wave peaks at two heights; 30–40 km and above 60 km with large spread in the mesosphere due to Doppler shifting in presence of westerly winds. The QBO easterly phase indicates low wave activity with 16-day wave indicating appreciable amplitudes in the upper stratosphere and mesosphere and is absent in the lower altitudes. This indicates that the 16-day wave might be generated through some in-situ mechanism due to gravity breaking or instability in the mesospheric region. Moreover, the refractive index of the two dominant planetary waves are strongly negative in the easterly phase relative to the westerly phase of QBO in the lower troposphere and stratosphere. This indicates the high probability of the planetary wave vertical propagation in the westerly phase of QBO. Therefore, the presented report re-emphasizes the importance of QBO controlling the middle atmospheric dynamics through vertical propagation of planetary scale waves in low-latitudes.
       
  • Relationships between the solar wind magnetic field and ground-level
           longwave irradiance at high northern latitudes
    • Abstract: Publication date: Available online 26 June 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): John E. Frederick, Brian A. Tinsley, Limin Zhou Longwave irradiances measured from two sites at different geomagnetic latitudes show different responses to changes in the east-west component of the interplanetary magnetic field (IMF By). At Barrow, Alaska, geomagnetic latitude 69-70oN, neither downward longwave irradiance from the atmosphere nor upward longwave irradiance from the ground show a significant correlation with By. However, at Alert, Canada, geomagnetic latitude near 87oN, a negative correlation that is marginally significant at the 95% level of confidence exists between By and downward longwave irradiance measured 3 days later. On average, a +3.5 nT increase in By is followed by a daily-mean downward longwave irradiance that is smaller by −0.60 ± 0.60% than would exist for a constant By. Similarly, daily-mean upward irradiance at a lag of 4 days is −0.51 ± 0.30% smaller than would exist otherwise, where error bars denote the 95% confidence range. The difference in upward irradiance corresponds to a surface cooling at Alert of approximately 0.33 ± 0.19 K. These results are qualitatively consistent with a previously proposed mechanism in which the interplanetary magnetic field perturbs the ionosphere-to-ground potential difference and the downward atmospheric current density over limited regions near the geomagnetic poles, altering local cloud properties. We find that the atmospheric longwave emission is altered on a time scale of 3 days, with a change in surface temperature appearing one day later, attributable to the thermal inertia of the surface. When one moves from the geomagnetic latitude of Alert (3° from the north geomagnetic pole) to the latitude of Barrow (∼20° from that pole), any connection between By and longwave irradiance becomes too small to isolate from the natural background variability.
       
  • A special issue for the space science of JASTP
    • Abstract: Publication date: Available online 22 June 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Wayan Suparta, Mardina Abdullah, Mahamod Ismail
       
  • Development of a hybrid classification technique based on deep learning
           applied to MSG / SEVIRI multispectral data
    • Abstract: Publication date: Available online 21 June 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Salim Oukali, Mourad Lazri, Karim Labadi, Jean Michel Brucker, Soltane Ameur The approach developed in this paper for the classification of precipitation intensities is based on deep learning of neural network. Multispectral data from the MSG satellite (Meteosat Second Generation) providing information about the cloud's physical and optical characteristics are exploited and used as inputs to a deep neural network model. The model is a combination of CNN (Convolutional Neural Network) and DMLP (Deep Multi-Layer Peceptron) which is learned and validated by comparison with the corresponding Radar data during the rainy seasons 2006/2007 and 2010/2011 respectively. The CNN extracts spatial characteristics from MSG multi-spectral images. Then, the set of spatial and multi-spectral information are used as inputs for the DMLP. The results show an improvement compared to the three other classifiers (Random Forest, Support Vector Machine and Artificial Neural Network). The CNN-DMLP method was also compared to the technique combining the three classifiers (SAR). The results indicate a percentage correct (PC) of 97% and a probability of detection (POD) of 90% for CNN-DMLP method compared to 94% and 87% for of the SAR technique, respectively. In terms of bias, the CNN-DMLP method gives 1.08 compared 1.10 for SAR technique.
       
  • Predicting SuperDARN cross polar cap potential by applying regression
           analysis and machine learning
    • Abstract: Publication date: Available online 19 June 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Erxiao Liu, Hongqiao Hu, Jianjun Liu, Xuyang Teng, Lei Qiao The cross polar cap potential (CPCP) is one of the primary parameters characterizing the electrodynamic feature of the high latitude ionosphere convection. In this study, we perform a comprehensive investigation of the Super Dual Auroral Radar Network (SuperDARN) CPCP, based on a large database of measurements from 1999 to 2009, and its relationship with various parameters of the solar wind, interplanetary magnetic field (IMF) and geomagnetic indices. Specifically, the IMF clock angle, the IMF Bz, the solar wind velocity, the plasma proton density, AE index, SymH index and Dst index are under consideration. According to the results of the correlation, the input parameters are selected and two models of the CPCP based on the multivariate regression analysis and Back Propagation Artificial Neural Network (BP ANN) algorithm are proposed respectively. The regression and BP ANN models are validated and the accuracy as well as the stability of the models is tested by using independent datasets. The result shows that the root mean square error (RMSE) between the measured and the model values ranges from 3.7 to 6.7 kV and the linear correlation coefficients are close to, or above 0.7. The ANN model is shown to have a better performance than the regression model.
       
  • Investigating extracted total precipitable water vapor from Weather
           Research and Forecasting (WRF) model and MODIS measurements
    • Abstract: Publication date: Available online 18 June 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Hossein Hassanli, Majid Rahimzadegan Total Precipitable Water (TPW) vapor value in the earth's atmosphere and its variations are of great importance in atmospheric and climatic studies. Among the most important methods introduced for estimation of TPW are satellite products such as Moderate Resolution Imaging Spectroradiometer (MODIS) and numerical methods such as Weather Research and Forecasting (WRF). The performance of TPW estimation methods are different in various locations and require evaluations. Then, the goal of this study is investigating the performance of estimated TPW from MODIS product (MOD05) and WRF model. In this regard, two infrared (IR) and near infrared (NIR) algorithms of MOD05 were evaluated. Moreover, three nested resolutions of 27, 9, and 3 km of the WRF in 0000 and 1200 UTC were investigated. Mehrabad radiosonde station in the south of Tehran, Iran was considered as the study area. Evaluation of the two selected models was performed using radiosonde measurements of 240 days in 2013 and 2014. Among the nested domains for WRF model, the 3 km model at 0000 UTC provided the best results with determination coefficient (R2) of 0.81 and Root Mean Square Difference (RMSD) of 2.98 mm. Among the MODIS products, MODIS IR showed a better performance with R2 of 0.72 and RMSD of 3.46 mm. In general, the estimated TPW from MODIS-IR and WRF3 showed that WRF has a better performance. Then, the results proved that WRF model can be used in various meteorological conditions for estimation TPW with an acceptable accuracy.
       
  • Surface solar radiation and its association with aerosol characteristics
           at an urban station in the Indo-Gangetic Basin: Implication to radiative
           effect
    • Abstract: Publication date: Available online 18 June 2019Source: Journal of Atmospheric and Solar-Terrestrial PhysicsAuthor(s): Sunil Kumar, A.K. Srivastava, V. Pathak, D.S. Bisht, S. Tiwari Short-wave incoming solar radiation and aerosol optical characteristics were examined at New Delhi, in the western Indo-Gangetic Basin (IGB) for the period from March 2010 to June 2012 to understand their possible association in different sky conditions along with their radiative implications. During the study period, solar radiation varied between 65 and 624 W m−2, with a seasonal mean of 419 ± 34, 328 ± 32, 308 ± 54 and 306 ± 56 W m−2, respectively in the summer, monsoon, post-monsoon and winter periods. Inter-annually, the magnitude of solar radiation was ∼19% and 23% higher during 2012 as compared to 2011 and 2010. Aerosol optical Depth (AOD) varied between 0.11 and 2.4 (mean: 0.69 ± 0.38) whereas Ångström Exponent (AE) was between 0.46 and 1.81 (mean: 0.8 ± 0.28) during the entire study period. The solar radiation was found to be significantly correlated with the AOD (R = −0.22) and AE (R = −0.45). The mean characteristics of solar radiation and aerosol optical parameters were found to differ significantly in different sky conditions, which were used to examine their possible implications to direct radiative effect (DRE). The DRE at the surface was as high as about −19 W m−2 during clear sky day, which was ∼16 and 48 W m−2 higher than that of haze/foggy and dusty days, respectively.
       
  • 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
       
  • 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.
       
  • 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
       
 
 
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