Pub Date : 2025-12-07DOI: 10.1016/j.jastp.2025.106702
Yueyang Wang, Yun Li, Shi Qiu, Shuangjiang Du, Zheng Sun, Lihua Shi
To address the underutilization of pulse signals in existing time-of-arrival (TOA) algorithms for lightning radiation source localization, this study proposes a three-dimensional (3-D) lightning TOA localization algorithm based on efficient VHF pulse matching. In the signal segment matching stage, a rotating reference station mechanism is introduced to overcome the bottleneck of single-reference station matching, ensuring full utilization of pulse signals from each detection substation. In the precise time delay alignment stage, the maximum possible time delay of 10 μs caused by the fast development of lightning is determined through Monte Carlo simulation. Overlapping time windows are set via the sliding window method to avoid omissions in pulse matching. During the pulse matching stage, the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) temporal clustering method is employed to traverse and match pulse signals within the same time window, and time-amplitude consistency verification is used to filter pulse matching results. Finally, the effectiveness of the novel optimized algorithm is verified through intracloud and cloud-to-ground flash cases. Compared with the existing algorithm, the novel optimized algorithm identifies 2.9 times more radiation sources. Meanwhile, it significantly improves the continuity and length of lightning channels, enabling more detailed reconstruction of complex lightning structures, and provides new technical tools for in-depth research on lightning processes and physical mechanisms.
{"title":"Three-dimensional lightning channel structure reconstruction: An efficient matching TOA algorithm for VHF pulses","authors":"Yueyang Wang, Yun Li, Shi Qiu, Shuangjiang Du, Zheng Sun, Lihua Shi","doi":"10.1016/j.jastp.2025.106702","DOIUrl":"10.1016/j.jastp.2025.106702","url":null,"abstract":"<div><div>To address the underutilization of pulse signals in existing time-of-arrival (TOA) algorithms for lightning radiation source localization, this study proposes a three-dimensional (3-D) lightning TOA localization algorithm based on efficient VHF pulse matching. In the signal segment matching stage, a rotating reference station mechanism is introduced to overcome the bottleneck of single-reference station matching, ensuring full utilization of pulse signals from each detection substation. In the precise time delay alignment stage, the maximum possible time delay of 10 μs caused by the fast development of lightning is determined through Monte Carlo simulation. Overlapping time windows are set via the sliding window method to avoid omissions in pulse matching. During the pulse matching stage, the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) temporal clustering method is employed to traverse and match pulse signals within the same time window, and time-amplitude consistency verification is used to filter pulse matching results. Finally, the effectiveness of the novel optimized algorithm is verified through intracloud and cloud-to-ground flash cases. Compared with the existing algorithm, the novel optimized algorithm identifies 2.9 times more radiation sources. Meanwhile, it significantly improves the continuity and length of lightning channels, enabling more detailed reconstruction of complex lightning structures, and provides new technical tools for in-depth research on lightning processes and physical mechanisms.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106702"},"PeriodicalIF":1.9,"publicationDate":"2025-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-05DOI: 10.1016/j.jastp.2025.106700
Anup Mahato, A.N.V. Satyanarayana
This study investigates the climatological variations of convective parameters over West Bengal, India, during the pre-monsoon season (March–May) from 1980 to 2020 using high (0.25° × 0.25°) horizontal resolution of ECMWF reanalysis (ERA-5) and hourly time interval data. Based on the analysis of spatial patterns of inter-annual variability and spatial patterns of trends employing the Mann-Kendall test of Convective Available Potential Energy (CAPE), Convective Inhibition (CIN), CAPE/CIN ratio, and K-index, an attempt has been made to identify potential convective zones for the occurrence of disastrous thunderstorms. The climatological analysis reveals the existence of three distinct zones with unique convective potential over West Bengal. The Coastal zone-1 (21.5°N-23°N, 87°E−89°E) exhibits a consistently favourable environment for convection with high values of positive energy and instability, low convective inhibition, and low spatial variability. The Central zone-2 (23°N-26°N, 86°E−89°E) shows an inconsistent convective environment with moderate spatial patterns of inter-annual variability of CAPE and CIN. The northern zone-3 (26°N-27°N, 88°E−90°E), presents less favourable but occasional convective conditions with generally lower magnitude of CAPE and CIN with highly varying spatial patterns of inter-annual variability. The K-index is sufficient to produce a convective environment in zone-1 than in the other two zones. Accordingly, the observed disastrous thunderstorm events are in alignment with the identified zones. The overall trend shows a clear reduction in storm activity moving from zone-1 to zone-3. The analysis reveals that the number of the observed disastrous thunderstorm events has shown a sudden increase from the year 2000 onwards.
In the present study, the proposed threshold value of the CAPE/CIN ratio is a useful indicator to identify potential convective zones. The temporal trend analysis of convective parameters over West Bengal during the last four decades reveals a spatial variability of convective potential of the atmosphere. The K-index demonstrated a gradual rise, particularly in the last decade, further supporting increased atmospheric instability. This study provides an important insight into changes in the conducive nature of the convective conditions over West Bengal, susceptible to the occurrences of disastrous thunderstorm activities in the context of global warming and climate change.
{"title":"Climatological analysis in identification of hotspot regions of pre-monsoon convective conditions for the occurrence of disastrous thunderstorms over West Bengal","authors":"Anup Mahato, A.N.V. Satyanarayana","doi":"10.1016/j.jastp.2025.106700","DOIUrl":"10.1016/j.jastp.2025.106700","url":null,"abstract":"<div><div>This study investigates the climatological variations of convective parameters over West Bengal, India, during the pre-monsoon season (March–May) from 1980 to 2020 using high (0.25° × 0.25°) horizontal resolution of ECMWF reanalysis (ERA-5) and hourly time interval data. Based on the analysis of spatial patterns of inter-annual variability and spatial patterns of trends employing the Mann-Kendall test of Convective Available Potential Energy (CAPE), Convective Inhibition (CIN), CAPE/CIN ratio, and K-index, an attempt has been made to identify potential convective zones for the occurrence of disastrous thunderstorms. The climatological analysis reveals the existence of three distinct zones with unique convective potential over West Bengal. The Coastal zone-1 (21.5°N-23°N, 87°E−89°E) exhibits a consistently favourable environment for convection with high values of positive energy and instability, low convective inhibition, and low spatial variability. The Central zone-2 (23°N-26°N, 86°E−89°E) shows an inconsistent convective environment with moderate spatial patterns of inter-annual variability of CAPE and CIN. The northern zone-3 (26°N-27°N, 88°E−90°E), presents less favourable but occasional convective conditions with generally lower magnitude of CAPE and CIN with highly varying spatial patterns of inter-annual variability. The K-index is sufficient to produce a convective environment in zone-1 than in the other two zones. Accordingly, the observed disastrous thunderstorm events are in alignment with the identified zones. The overall trend shows a clear reduction in storm activity moving from zone-1 to zone-3. The analysis reveals that the number of the observed disastrous thunderstorm events has shown a sudden increase from the year 2000 onwards.</div><div>In the present study, the proposed threshold value of the CAPE/CIN ratio is a useful indicator to identify potential convective zones. The temporal trend analysis of convective parameters over West Bengal during the last four decades reveals a spatial variability of convective potential of the atmosphere. The K-index demonstrated a gradual rise, particularly in the last decade, further supporting increased atmospheric instability. This study provides an important insight into changes in the conducive nature of the convective conditions over West Bengal, susceptible to the occurrences of disastrous thunderstorm activities in the context of global warming and climate change.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106700"},"PeriodicalIF":1.9,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145747524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Surface Ozone (O3) is a secondary air pollutant of major concern owing to its impacts on human health, vegetation, materials, and regional climate. This study presents a year-long (March 2021–February 2022) investigation of O3 variability and its driving factors in Kadapa, a semi-arid region of southern India. Continuous ground-based measurements using a UV photometric analyzer, complemented by Particulate-Matter (PM2.5) data, ERA5 meteorological reanalysis, and satellite inputs, were analyzed through a combination of Generalized Additive Model (GAM) and air-mass trajectory approaches (WPSCF and WCWT). Pronounced diurnal and seasonal O3 patterns revealed a pronounced afternoon peak driven by photochemical activity, with maximum concentrations observed in summer and minimum levels during the monsoon. GAM analysis highlighted strong seasonal dependencies, with relative humidity and temperature emerging as dominant nonlinear drivers of O3, while trajectory models revealed seasonal shifts in source regions—from the Bay of Bengal and Arabian Sea to continental and northeastern inflows. The observed nonlinear O3–PM2.5 interactions indicated photochemical enhancement under moderate aerosol loading and suppression under high aerosol concentrations due to reduced photolysis. These results provide the first integrated assessment of O3 behaviour in this semi-arid environment, improving understanding of O3–aerosol–meteorology couplings and supporting mitigation strategies for tropical India.
{"title":"Source attribution and temporal patterns of surface ozone in a semi-arid region of southern India via GAM and trajectory models","authors":"Ramanjula Reddy Annareddy, Fasiha Begum Shaik, Bhavana Thatapi, Chandrasekhar Reddy Chukkaluri, Nazeer Ahammed Yadiki","doi":"10.1016/j.jastp.2025.106699","DOIUrl":"10.1016/j.jastp.2025.106699","url":null,"abstract":"<div><div>Surface Ozone (O<sub>3</sub>) is a secondary air pollutant of major concern owing to its impacts on human health, vegetation, materials, and regional climate. This study presents a year-long (March 2021–February 2022) investigation of O<sub>3</sub> variability and its driving factors in Kadapa, a semi-arid region of southern India. Continuous ground-based measurements using a UV photometric analyzer, complemented by Particulate-Matter (PM<sub>2</sub>.<sub>5</sub>) data, ERA5 meteorological reanalysis, and satellite inputs, were analyzed through a combination of Generalized Additive Model (GAM) and air-mass trajectory approaches (WPSCF and WCWT). Pronounced diurnal and seasonal O<sub>3</sub> patterns revealed a pronounced afternoon peak driven by photochemical activity, with maximum concentrations observed in summer and minimum levels during the monsoon. GAM analysis highlighted strong seasonal dependencies, with relative humidity and temperature emerging as dominant nonlinear drivers of O<sub>3</sub>, while trajectory models revealed seasonal shifts in source regions—from the Bay of Bengal and Arabian Sea to continental and northeastern inflows. The observed nonlinear O<sub>3</sub>–PM<sub>2</sub>.<sub>5</sub> interactions indicated photochemical enhancement under moderate aerosol loading and suppression under high aerosol concentrations due to reduced photolysis. These results provide the first integrated assessment of O<sub>3</sub> behaviour in this semi-arid environment, improving understanding of O<sub>3</sub>–aerosol–meteorology couplings and supporting mitigation strategies for tropical India.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106699"},"PeriodicalIF":1.9,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-03DOI: 10.1016/j.jastp.2025.106701
R.K. Sumesh , E.A. Resmi , M.G. Manoj , T.S. Sreekanth , Nita Sukumar , Charan Teja Tejavath , C.K. Unnikrishnan , Dharmadas Jash , K. Mohankumar
This study aims to characterize the diurnal variability of raindrop size distribution (DSD) and associated cloud layers during the transition from pre-monsoon to monsoon onset over southern peninsular India. In-situ observations from the Advanced Centre for Atmospheric Radar Research (ACARR) at Cochin (40 m above msl) and the High-Altitude Cloud Physics Observatory (HACPO) (1820m above msl) at Munnar in Kerala, during 2017–2019, were used to analyse the microphysical process and cloud layers governing rainfall formation. DSDs and their gamma parameters were derived from disdrometer measurements, while cloud base heights were obtained from ceilometer data, and thermodynamical parameters from re-analysis datasets. At ACARR, the onset phase (±5 days from the monsoon onset day) is characterised by frequent, short-duration, intense rain events with broader DSDs. While HACPO exhibits enhanced concentrations of small to medium drops (0.31–2.12 mm) across rain categories. Diurnal analysis reveals convective DSD dominance in the pre-onset phase (−10 days before the onset phase) at ACARR, whereas transition-type DSDs appear earlier at HACPO, indicating orographic influence. Analysis of Gamma DSD parameters and Nw–Dm relationships reveals strong convective signatures at ACARR compared to HACPO during the onset phase and evolving toward stratiform-dominant rainfall with the progression of the monsoon. Rainfall is mainly driven by low-level clouds at ACARR, whereas sustained stratiform rain over HACPO is linked to multilayered cloud systems. These results underscore the contrasting microphysical and thermodynamic controls on rainfall development across terrains, enhancing understanding of regional variability during monsoon onset and aiding improved rainfall prediction in models.
{"title":"Characterizing microphysical transitions in southwest monsoon onset precipitation: An observational insight from southern peninsular India","authors":"R.K. Sumesh , E.A. Resmi , M.G. Manoj , T.S. Sreekanth , Nita Sukumar , Charan Teja Tejavath , C.K. Unnikrishnan , Dharmadas Jash , K. Mohankumar","doi":"10.1016/j.jastp.2025.106701","DOIUrl":"10.1016/j.jastp.2025.106701","url":null,"abstract":"<div><div>This study aims to characterize the diurnal variability of raindrop size distribution (DSD) and associated cloud layers during the transition from pre-monsoon to monsoon onset over southern peninsular India. In-situ observations from the Advanced Centre for Atmospheric Radar Research (ACARR) at Cochin (40 m above msl) and the High-Altitude Cloud Physics Observatory (HACPO) (1820m above msl) at Munnar in Kerala, during 2017–2019, were used to analyse the microphysical process and cloud layers governing rainfall formation. DSDs and their gamma parameters were derived from disdrometer measurements, while cloud base heights were obtained from ceilometer data, and thermodynamical parameters from re-analysis datasets. At ACARR, the onset phase (±5 days from the monsoon onset day) is characterised by frequent, short-duration, intense rain events with broader DSDs. While HACPO exhibits enhanced concentrations of small to medium drops (0.31–2.12 mm) across rain categories. Diurnal analysis reveals convective DSD dominance in the pre-onset phase (−10 days before the onset phase) at ACARR, whereas transition-type DSDs appear earlier at HACPO, indicating orographic influence. Analysis of Gamma DSD parameters and N<sub>w</sub>–D<sub>m</sub> relationships reveals strong convective signatures at ACARR compared to HACPO during the onset phase and evolving toward stratiform-dominant rainfall with the progression of the monsoon. Rainfall is mainly driven by low-level clouds at ACARR, whereas sustained stratiform rain over HACPO is linked to multilayered cloud systems. These results underscore the contrasting microphysical and thermodynamic controls on rainfall development across terrains, enhancing understanding of regional variability during monsoon onset and aiding improved rainfall prediction in models.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106701"},"PeriodicalIF":1.9,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-02DOI: 10.1016/j.jastp.2025.106698
J.F. Nicolás, J. Crespo, E. Yubero, M. Alfosea-Simón, A. Clemente, N. Gómez-Sanchez, N. Galindo
In the present work, the contribution of PM2.5 sources to light absorption (σap,520) and scattering (σsp,525), as well as their impact on SSA values, was analysed. For this, measurements of aerosol optical properties and PM2.5 chemical composition were conducted at a rural site in southeastern Spain. The sources that significantly contributed to light extinction were: road traffic (TR), biomass burning (BB), mineral dust (MD), and a secondary aerosol source (SA). BB accounted for nearly 50 % of the absorption coefficient (λ = 520 nm), while the SA source exhibited the largest contribution to the scattering process (∼47 % at 525 nm). MD showed the smallest contribution to σap,520 and σsp,525, although its contribution significantly increased during Saharan dust events (SDEs). SSA daily values showed a clear dependence on the contribution of individual sources to PM2.5 concentrations. SSA values (λ = 525 nm) exceeding 0.90 were observed when contributions from secondary aerosols were greater than 50 %, while the SSA decreased with the increase in the contribution from road traffic. The contribution from BB was fairly constant for almost all SSA values, although high SSA values (>0.90) were observed when the contribution from this source was very low. The SSA showed a clear spectral dependence that varied according to the aerosol type. So, for BB aerosols the SSA decreased with wavelength, while for mineral dust the opposite trend was observed.
{"title":"The impact of PM2.5 sources on the single scattering albedo at a rural site in the south-western Mediterranean region","authors":"J.F. Nicolás, J. Crespo, E. Yubero, M. Alfosea-Simón, A. Clemente, N. Gómez-Sanchez, N. Galindo","doi":"10.1016/j.jastp.2025.106698","DOIUrl":"10.1016/j.jastp.2025.106698","url":null,"abstract":"<div><div>In the present work, the contribution of PM<sub>2.5</sub> sources to light absorption (σ<sub>ap,520</sub>) and scattering (σ<sub>sp,525</sub>), as well as their impact on SSA values, was analysed. For this, measurements of aerosol optical properties and PM<sub>2.5</sub> chemical composition were conducted at a rural site in southeastern Spain. The sources that significantly contributed to light extinction were: road traffic (TR), biomass burning (BB), mineral dust (MD), and a secondary aerosol source (SA). BB accounted for nearly 50 % of the absorption coefficient (λ = 520 nm), while the SA source exhibited the largest contribution to the scattering process (∼47 % at 525 nm). MD showed the smallest contribution to σ<sub>ap,520</sub> and σ<sub>sp,525</sub>, although its contribution significantly increased during Saharan dust events (SDEs). SSA daily values showed a clear dependence on the contribution of individual sources to PM<sub>2.5</sub> concentrations. SSA values (λ = 525 nm) exceeding 0.90 were observed when contributions from secondary aerosols were greater than 50 %, while the SSA decreased with the increase in the contribution from road traffic. The contribution from BB was fairly constant for almost all SSA values, although high SSA values (>0.90) were observed when the contribution from this source was very low. The SSA showed a clear spectral dependence that varied according to the aerosol type. So, for BB aerosols the SSA decreased with wavelength, while for mineral dust the opposite trend was observed.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106698"},"PeriodicalIF":1.9,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01DOI: 10.1016/j.jastp.2025.106695
Hamza Gerçekcioğlu , Yahya Baykal
Utilizing the Rytov method in weakly turbulent oceanic medium, minimum scintillation index of sinusoidal Gaussian (SG) laser beams, named as the optimum beam (OB), is investigated for the underwater wireless optical communication (UWOC). Horizontal link between any underwater vehicles is considered. The formulation of the on-axis scintillation index of these beams is derived analytically, and the minimum scintillation index is determined with suitable adjustment of the complex displacement parameters. The complex displacement parameters are identified and tabulated for the selected propagation distance and source size. Obtained scintillation index results are drawn against the propagation length and source size. When compared with the plane, spherical, collimated, focused Gaussian, cos-Gaussian and cosh-Gaussian beams, OB is found to possess essential advantage. Additionally, with the obtained scintillation index values, probabilities of fade of these beams are calculated and their behaviors are also presented. OB also has a significant advantage when considering the fade probability.
{"title":"Mitigation of laser beam fluctuation and performance of probability of fade in weak ocean turbulence","authors":"Hamza Gerçekcioğlu , Yahya Baykal","doi":"10.1016/j.jastp.2025.106695","DOIUrl":"10.1016/j.jastp.2025.106695","url":null,"abstract":"<div><div>Utilizing the Rytov method in weakly turbulent oceanic medium, minimum scintillation index of sinusoidal Gaussian (SG) laser beams, named as the optimum beam (OB), is investigated for the underwater wireless optical communication (UWOC). Horizontal link between any underwater vehicles is considered. The formulation of the on-axis scintillation index of these beams is derived analytically, and the minimum scintillation index is determined with suitable adjustment of the complex displacement parameters. The complex displacement parameters are identified and tabulated for the selected propagation distance and source size. Obtained scintillation index results are drawn against the propagation length and source size. When compared with the plane, spherical, collimated, focused Gaussian, cos-Gaussian and cosh-Gaussian beams, OB is found to possess essential advantage. Additionally, with the obtained scintillation index values, probabilities of fade of these beams are calculated and their behaviors are also presented. OB also has a significant advantage when considering the fade probability.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106695"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The influence of warming on mountain precipitation is a pressing concern, yet the link between rising surface temperatures and changes in precipitation phases i.e., liquid (rainfall) and solid (snowfall) precipitation in the North-western Himalayas (NWH) remains poorly understood. The present study aims to make a maiden attempt of exploring the temperature-sensitive variations in precipitation phases over the two distinct glacierized basins of NWH (Ravi and Bhaga basins) by utilizing data from ERA5 product. For this purpose, we first examined the monthly, inter-annual, and inter-decadal variations in near-surface temperature (T), total precipitation (TP) and precipitation phase separately, as snow fraction (SF) and rain fraction (RF) intensity for the period 1940–2022. Second, we examined the long-term (1940–2022) and bifurcated (based on significance level) temporal variations in T, TP, SF, and RF. Lastly, to provide insights on how rise in T has induced changes in TP, SF, and RF, the percent of changes in respective precipitation patterns were normalized by degree of warming and presented in percent change per Kelvin (%/K) for each basin. During summer months, Bhaga basin showed higher variability in RF and SF than in Ravi basin. Interestingly, in comparison to the inter-annual, inter-decadal oscillations provided better picture of temporal variations in precipitation patterns over these basins. The long-term variations in TP revealed non-significant trend, while opposite significant trends were observed during bifurcated time periods. With respect to the long-term trends in precipitation phases i.e., in RF and SF, significant increasing trend in RF (+0.04 %/year) and an opposite significant decreasing trend in SF (−0.04 %/year) were observed in both basins. Despite the long-term significant trends in precipitation phases, significant opposing trends within each precipitation phase were observed during bifurcated periods. The percent change per Kelvin in TP over Ravi basin was −6.48 %/K, while for Bhaga basin it was +3.28 %/K. Furthermore, the changes in TP over Ravi was mainly contributed by the changes observed in SF (−6.36 %/K), while for Bhaga it was mainly contributed by RF (+8.02 %/K). The findings suggest that warming has shifted the precipitation phase from solid to liquid, indicating an escalation of rain-on-snow events over the glacierized basins in NWH.
{"title":"Temperature-sensitive changes in precipitation phases over two distinct glacierized basins of the North-Western Himalayas","authors":"Shanta Kumar , Ashish Dogra , Chander Prakash , Anurag Linda","doi":"10.1016/j.jastp.2025.106691","DOIUrl":"10.1016/j.jastp.2025.106691","url":null,"abstract":"<div><div>The influence of warming on mountain precipitation is a pressing concern, yet the link between rising surface temperatures and changes in precipitation phases i.e., liquid (rainfall) and solid (snowfall) precipitation in the North-western Himalayas (NWH) remains poorly understood. The present study aims to make a maiden attempt of exploring the temperature-sensitive variations in precipitation phases over the two distinct glacierized basins of NWH (Ravi and Bhaga basins) by utilizing data from ERA5 product. For this purpose, we first examined the monthly, inter-annual, and inter-decadal variations in near-surface temperature (T), total precipitation (TP) and precipitation phase separately, as snow fraction (SF) and rain fraction (RF) intensity for the period 1940–2022. Second, we examined the long-term (1940–2022) and bifurcated (based on significance level) temporal variations in T, TP, SF, and RF. Lastly, to provide insights on how rise in T has induced changes in TP, SF, and RF, the percent of changes in respective precipitation patterns were normalized by degree of warming and presented in percent change per Kelvin (%/K) for each basin. During summer months, Bhaga basin showed higher variability in RF and SF than in Ravi basin. Interestingly, in comparison to the inter-annual, inter-decadal oscillations provided better picture of temporal variations in precipitation patterns over these basins. The long-term variations in TP revealed non-significant trend, while opposite significant trends were observed during bifurcated time periods. With respect to the long-term trends in precipitation phases i.e., in RF and SF, significant increasing trend in RF (+0.04 %/year) and an opposite significant decreasing trend in SF (−0.04 %/year) were observed in both basins. Despite the long-term significant trends in precipitation phases, significant opposing trends within each precipitation phase were observed during bifurcated periods. The percent change per Kelvin in TP over Ravi basin was −6.48 %/K, while for Bhaga basin it was +3.28 %/K. Furthermore, the changes in TP over Ravi was mainly contributed by the changes observed in SF (−6.36 %/K), while for Bhaga it was mainly contributed by RF (+8.02 %/K). The findings suggest that warming has shifted the precipitation phase from solid to liquid, indicating an escalation of rain-on-snow events over the glacierized basins in NWH.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106691"},"PeriodicalIF":1.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1016/j.jastp.2025.106693
Lian Lian
Accurate ultra-short-term wind speed prediction is of decisive significance for improving the grid connection efficiency of wind power generation, reducing the operation and maintenance costs of wind farms and maintaining the stable operation of wind power systems. This paper presents a prediction model based on improved sparrow search algorithm optimized extreme learning machine. Based on the standard sparrow search algorithm, three improved strategies including population initialization based on Piecewise chaotic map, improved position update of the discover and optimal value search are introduced to make the initial population evenly distributed and improve the global search performance and anti local minimum ability of the algorithm. The comparison of eight CEC2017 benchmark functions shows that the proposed improved sparrow search algorithm achieved the best optimization performance (mean and standard deviation) in six of them. The improved sparrow search algorithm is used to optimize the input weights and biases of hidden nodes in extreme learning machine model, which greatly improves the prediction accuracy of model. The performance of the model is evaluated by using the actual ultra-short-term wind speed dataset. In the experiment, autoregressive integrated moving average model in the statistical model, least squares support vector machine and extreme learning machine in the machine learning model, and Transformer, temporal convolutional network, graph neural network, bidirectional long short-term memory and convolutional neural network-long short-term memory in the deep learning model are selected as comparison models. The effectiveness of the proposed prediction model is verified by prediction error, performance indicators comparison, box plot, statistical index and Taylor chart. Compared with these ten comparison models, root mean square error decreased by 26.82 %–60.32 %, mean absolute error decreased by 27.21 %–60.12 %, mean absolute percentage error decreased by 24.60 %–59.84 %, relative root mean square error decreased by 29.00 %–147.16 %, square sum error decreased by 46.45 %–84.25 %, Theil Inequality coefficient decreased by 26.40 %–59.41 %, R square increased by 10.49 %–141.28 %, the index of agreement increased by 0.43 %–2.67 % and Pearson correlation coefficient increased by 3.14 %–20.49 %. At the same time, the training time of the proposed model is 372.0942 s, which can meet the requirements of the most common 15 min scheduling cycle in the actual wind farm management system, and provides an effective solution strategy for ultra-short-term wind speed prediction.
{"title":"Improved sparrow search algorithm optimized extreme learning machine for ultra-short-term wind speed prediction","authors":"Lian Lian","doi":"10.1016/j.jastp.2025.106693","DOIUrl":"10.1016/j.jastp.2025.106693","url":null,"abstract":"<div><div>Accurate ultra-short-term wind speed prediction is of decisive significance for improving the grid connection efficiency of wind power generation, reducing the operation and maintenance costs of wind farms and maintaining the stable operation of wind power systems. This paper presents a prediction model based on improved sparrow search algorithm optimized extreme learning machine. Based on the standard sparrow search algorithm, three improved strategies including population initialization based on Piecewise chaotic map, improved position update of the discover and optimal value search are introduced to make the initial population evenly distributed and improve the global search performance and anti local minimum ability of the algorithm. The comparison of eight CEC2017 benchmark functions shows that the proposed improved sparrow search algorithm achieved the best optimization performance (mean and standard deviation) in six of them. The improved sparrow search algorithm is used to optimize the input weights and biases of hidden nodes in extreme learning machine model, which greatly improves the prediction accuracy of model. The performance of the model is evaluated by using the actual ultra-short-term wind speed dataset. In the experiment, autoregressive integrated moving average model in the statistical model, least squares support vector machine and extreme learning machine in the machine learning model, and Transformer, temporal convolutional network, graph neural network, bidirectional long short-term memory and convolutional neural network-long short-term memory in the deep learning model are selected as comparison models. The effectiveness of the proposed prediction model is verified by prediction error, performance indicators comparison, box plot, statistical index and Taylor chart. Compared with these ten comparison models, root mean square error decreased by 26.82 %–60.32 %, mean absolute error decreased by 27.21 %–60.12 %, mean absolute percentage error decreased by 24.60 %–59.84 %, relative root mean square error decreased by 29.00 %–147.16 %, square sum error decreased by 46.45 %–84.25 %, Theil Inequality coefficient decreased by 26.40 %–59.41 %, R square increased by 10.49 %–141.28 %, the index of agreement increased by 0.43 %–2.67 % and Pearson correlation coefficient increased by 3.14 %–20.49 %. At the same time, the training time of the proposed model is 372.0942 s, which can meet the requirements of the most common 15 min scheduling cycle in the actual wind farm management system, and provides an effective solution strategy for ultra-short-term wind speed prediction.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106693"},"PeriodicalIF":1.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145621938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1016/j.jastp.2025.106692
Akshay S. Patil , Aditi D. Yadav , Bhushan Vibhute , Dada P. Nade , T. Dharmaraj , Sambhaji M. Pawar , Sunil D. Pawar
Severe convective systems such as tropical cyclones and thunderstorms play a vital role in vertically coupling the Earth's atmosphere, often driving perturbations from the lower troposphere to the upper ionosphere. During the passage of Extremely Severe Cyclonic Storm (ESCS) Tauktae over the Arabian Sea in May 2021, this study examines the interactions between the atmosphere and ionosphere. We employ a multi-instrumental strategy that combines GNSS-based Total Electron Content (TEC) observations from the Indian Institute of Science (IISc) Bangalore, mesospheric temperature profiles from the SABER instrument onboard the TIMED satellite, and lightning data from the Indian Lightning Location Network (ILLN). Strong thermal disturbances and gravity wave signatures were observed in the mesosphere-lower thermosphere area on May 15–16, coinciding with a noticeable increase in lightning activity. Concurrently, short-period TEC fluctuations with peak power in the 1–2 mHz band were observed, indicating travelling ionospheric disturbances (TIDs). The temporal alignment of lightning peaks, gravity wave signatures, and TEC anomalies suggests efficient coupling between the troposphere and ionosphere during the cyclone. These findings support the concept of gravity wave-mediated coupling between the troposphere and ionosphere during extreme weather events.
{"title":"Ionospheric response to lightning activity during cyclone Tauktae over the Arabian Sea","authors":"Akshay S. Patil , Aditi D. Yadav , Bhushan Vibhute , Dada P. Nade , T. Dharmaraj , Sambhaji M. Pawar , Sunil D. Pawar","doi":"10.1016/j.jastp.2025.106692","DOIUrl":"10.1016/j.jastp.2025.106692","url":null,"abstract":"<div><div>Severe convective systems such as tropical cyclones and thunderstorms play a vital role in vertically coupling the Earth's atmosphere, often driving perturbations from the lower troposphere to the upper ionosphere. During the passage of Extremely Severe Cyclonic Storm (ESCS) Tauktae over the Arabian Sea in May 2021, this study examines the interactions between the atmosphere and ionosphere. We employ a multi-instrumental strategy that combines GNSS-based Total Electron Content (TEC) observations from the Indian Institute of Science (IISc) Bangalore, mesospheric temperature profiles from the SABER instrument onboard the TIMED satellite, and lightning data from the Indian Lightning Location Network (ILLN). Strong thermal disturbances and gravity wave signatures were observed in the mesosphere-lower thermosphere area on May 15–16, coinciding with a noticeable increase in lightning activity. Concurrently, short-period TEC fluctuations with peak power in the 1–2 mHz band were observed, indicating travelling ionospheric disturbances (TIDs). The temporal alignment of lightning peaks, gravity wave signatures, and TEC anomalies suggests efficient coupling between the troposphere and ionosphere during the cyclone. These findings support the concept of gravity wave-mediated coupling between the troposphere and ionosphere during extreme weather events.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106692"},"PeriodicalIF":1.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145621937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-26DOI: 10.1016/j.jastp.2025.106694
Renato Gomes da Silva , José Henrique Fernandez , Giuliani Paulineli Garbi
The geostationary satellite IntelSat-33e experienced a catastrophic failure on October 19, 2024, resulting in the generation of approximately 500 debris fragments. This study examines the satellite anomaly in light of intense space weather conditions observed in the preceding days. A multi-parameter analysis was performed using geomagnetic indices (Dst, Kp and Ap), solar wind data from the OMNI database (IMF Bz, solar wind speed, and dynamic pressure), and high-energy electron fluxes (> 2 MeV) from GOES-16. The results indicate that spatial conditions began to change significantly after the arrival of solar wind shock fronts, evolving into a geomagnetic storm that began on October 6. A new, even more intense storm occurred on October 10. These events were driven by compound solar wind disturbances composed of coronal mass ejections followed by high-speed solar wind stream. Such combined drivers are known to enhance magnetospheric convection, substorm activity, and chorus/ULF wave generation, which in turn accelerateelectrons to relativistic energies within the outer radiation belt. This sustained high-radiation environment likely caused internal charging processes in the satellite, culminating in its fatal failure. These findings emphasize the need for real-time space weather monitoring, improved coronal mass ejections impact prediction, and resilient satellite designs for geosynchronous orbit missions.
{"title":"On the geospace conditions in relation to the IntelSat-33e satellite fatal failure in October 2024","authors":"Renato Gomes da Silva , José Henrique Fernandez , Giuliani Paulineli Garbi","doi":"10.1016/j.jastp.2025.106694","DOIUrl":"10.1016/j.jastp.2025.106694","url":null,"abstract":"<div><div>The geostationary satellite <em>IntelSat-33e</em> experienced a catastrophic failure on October 19, 2024, resulting in the generation of approximately 500 debris fragments. This study examines the satellite anomaly in light of intense space weather conditions observed in the preceding days. A multi-parameter analysis was performed using geomagnetic indices (Dst, Kp and Ap), solar wind data from the OMNI database (IMF Bz, solar wind speed, and dynamic pressure), and high-energy electron fluxes (<em>></em> 2 MeV) from GOES-16. The results indicate that spatial conditions began to change significantly after the arrival of solar wind shock fronts, evolving into a geomagnetic storm that began on October 6. A new, even more intense storm occurred on October 10. These events were driven by compound solar wind disturbances composed of coronal mass ejections followed by high-speed solar wind stream. Such combined drivers are known to enhance magnetospheric convection, substorm activity, and chorus/ULF wave generation, which in turn accelerateelectrons to relativistic energies within the outer radiation belt. This sustained high-radiation environment likely caused internal charging processes in the satellite, culminating in its fatal failure. These findings emphasize the need for real-time space weather monitoring, improved coronal mass ejections impact prediction, and resilient satellite designs for geosynchronous orbit missions.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"278 ","pages":"Article 106694"},"PeriodicalIF":1.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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