Pub Date : 2024-12-01DOI: 10.1016/j.jastp.2024.106389
A. Kalyan Teja , M. Venkat Ratnam , S. Vijaya Bhaskara Rao
An attempt has been made to obtain mean winds covering the complete middle and upper atmosphere over a tropical region, Tirupati(13.5°N, 79.2°E) using a combined dataset of ERA5 reanalysis, SVU-meteor radar, and ICON/MIGHTI after comprehensive validation. Regardless of the season, thermospheric(200–300 km) and mesospheric(80–100 km) winds exhibit significant diurnal variability. Mean winds exhibit two distinct semi-annual oscillations at the stratopause and in the mesosphere. Tidal amplitudes are larger in meridional winds compared to that of zonal winds in the MLT region. This work has the potential in the field of numerical modeling of atmospheric circulation, especially to verify numerical simulations.
{"title":"Mean winds and tidal variability from troposphere to the thermosphere retrieved from combined ground based and space borne measurements","authors":"A. Kalyan Teja , M. Venkat Ratnam , S. Vijaya Bhaskara Rao","doi":"10.1016/j.jastp.2024.106389","DOIUrl":"10.1016/j.jastp.2024.106389","url":null,"abstract":"<div><div>An attempt has been made to obtain mean winds covering the complete middle and upper atmosphere over a tropical region, Tirupati(13.5°N, 79.2°E) using a combined dataset of ERA5 reanalysis, SVU-meteor radar, and ICON/MIGHTI after comprehensive validation. Regardless of the season, thermospheric(200–300 km) and mesospheric(80–100 km) winds exhibit significant diurnal variability. Mean winds exhibit two distinct semi-annual oscillations at the stratopause and in the mesosphere. Tidal amplitudes are larger in meridional winds compared to that of zonal winds in the MLT region. This work has the potential in the field of numerical modeling of atmospheric circulation, especially to verify numerical simulations.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106389"},"PeriodicalIF":1.8,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758867","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 : 2024-12-01DOI: 10.1016/j.jastp.2024.106391
A.V. Ivanovskiy
The mechanism of a stepped leader not related to processes in the cloud is considered. The average leader speed is determined by the formation of a channel due to heating of one of the space stems in the electric field of the streamer corona. If the drift speed of the electrons in the formed channel is higher than the leader propagation speed, a drift wave arises which catches up with the boundary of the streamer zone. The electric field growth leads to a formation of the stepped leader. The mechanism is realized in case of a negative leader. Realism of this scenario has been checked by numerical simulations. For the negative leader the formation of the step with parameters close to those for natural leaders has been obtained. The estimated maximum speed of the electron drift at the stage of channel formation, which exceeds the negative leader propagation speed observed in the experiments, counts in favor of the above ideas.
{"title":"Mechanism of a stepped leader in a negative lightning","authors":"A.V. Ivanovskiy","doi":"10.1016/j.jastp.2024.106391","DOIUrl":"10.1016/j.jastp.2024.106391","url":null,"abstract":"<div><div>The mechanism of a stepped leader not related to processes in the cloud is considered. The average leader speed is determined by the formation of a channel due to heating of one of the space stems in the electric field of the streamer corona. If the drift speed of the electrons in the formed channel is higher than the leader propagation speed, a drift wave arises which catches up with the boundary of the streamer zone. The electric field growth leads to a formation of the stepped leader. The mechanism is realized in case of a negative leader. Realism of this scenario has been checked by numerical simulations. For the negative leader the formation of the step with parameters close to those for natural leaders has been obtained. The estimated maximum speed of the electron drift at the stage of channel formation, which exceeds the negative leader propagation speed observed in the experiments, counts in favor of the above ideas.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106391"},"PeriodicalIF":1.8,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142744320","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}
Drought indices are a suitable tool for management measures and dealing with drought and are widely used worldwide. One of the most important stages of assessing the drought situation in each region is determining the drought indices to analyze the intensity and duration of drought in that region. The drought index is actually a function of various environmental factors that affect the drought phenomenon. In this study, the drought indices of the standardized precipitation index (SPI), China-Z index (CZI), Z Score Index (ZSI), and modified CZI (MCZI) in different month time scales (1, 3, 6, 9, 12, 18, 24 and 48) and the present of normal index (PNI) in different monthly, seasonally and yearly time scales in Kurdistan Province (stations Saqqez, Qorveh, Bijar, Sanandaj) were evaluated. Global land data assimilation system (GLDAS), Climatic Research Unit (CRU) dataset, and Tropical Rainfall Measuring Mission (TRMM) precipitation data (2000-2020) and TRMM precipitation (2000-2019) were received, and the drought indices were calculated. Root mean square error (RMSE), maximum error (ME), Pearson, and Spearman correlation coefficients were used for evaluation. The results of the SPI index showed that there is a significant relationship between TRMM, CRU, and GLDAS at the Saqqez, Qorveh, and Sanandaj stations (at the 5% level), and there was no significant relationship for TRMM at Bijar station for the 24-month time scale. The correlation coefficient results for the Saqqez and Sanandaj stations in time scales of 1 to 9 months for the SPI, CZI, ZSI, and MCZI indices were better than those of the Bijar and Qorveh stations. In assessing the SPI and CZI drought indices, the highest RMSE was for GLDAS at Bijar station and for the 48-month time scale. In general, the results showed that the drought indices of the SPI, CZI, ZSI, MCZI, and PNI obtained from the TRMM satellite, CRU dataset, and GLDAS model have a good correlation with the drought indices of synoptic stations.
{"title":"Evaluation of meteorological drought indices using remote sensing","authors":"Mojgan Ahmadi , Hadi Ramezani Etedali , Abbass Kaviani , Alireza Tavakoli","doi":"10.1016/j.jastp.2024.106387","DOIUrl":"10.1016/j.jastp.2024.106387","url":null,"abstract":"<div><div>Drought indices are a suitable tool for management measures and dealing with drought and are widely used worldwide. One of the most important stages of assessing the drought situation in each region is determining the drought indices to analyze the intensity and duration of drought in that region. The drought index is actually a function of various environmental factors that affect the drought phenomenon. In this study, the drought indices of the standardized precipitation index (SPI), China-Z index (CZI), Z Score Index (ZSI), and modified CZI (MCZI) in different month time scales (1, 3, 6, 9, 12, 18, 24 and 48) and the present of normal index (PNI) in different monthly, seasonally and yearly time scales in Kurdistan Province (stations Saqqez, Qorveh, Bijar, Sanandaj) were evaluated. Global land data assimilation system (GLDAS), Climatic Research Unit (CRU) dataset, and Tropical Rainfall Measuring Mission (TRMM) precipitation data (2000-2020) and TRMM precipitation (2000-2019) were received, and the drought indices were calculated. Root mean square error (RMSE), maximum error (ME), Pearson, and Spearman correlation coefficients were used for evaluation. The results of the SPI index showed that there is a significant relationship between TRMM, CRU, and GLDAS at the Saqqez, Qorveh, and Sanandaj stations (at the 5% level), and there was no significant relationship for TRMM at Bijar station for the 24-month time scale. The correlation coefficient results for the Saqqez and Sanandaj stations in time scales of 1 to 9 months for the SPI, CZI, ZSI, and MCZI indices were better than those of the Bijar and Qorveh stations. In assessing the SPI and CZI drought indices, the highest RMSE was for GLDAS at Bijar station and for the 48-month time scale. In general, the results showed that the drought indices of the SPI, CZI, ZSI, MCZI, and PNI obtained from the TRMM satellite, CRU dataset, and GLDAS model have a good correlation with the drought indices of synoptic stations.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106387"},"PeriodicalIF":1.8,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758866","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 : 2024-11-20DOI: 10.1016/j.jastp.2024.106384
Olusola Samuel Ojo, Promise Dunsin Adesemoye
The study examines the potential impact of climate change on photovoltaic energy (PV) in Nigeria. Solar radiation and temperature datasets from 13 regional climate models (CMIP6) for 2015–2099 were used to evaluate the photovoltaic energy under moderate (SSP245) and high (SSP585) emission scenarios for near-future (2023–2053), mid-future (2054–2084), and far-future (2084–2099) periods. The precision of the models for the simulation of PV energy was validated with MERRA-2 reference data using the compromise programming index (CPI). Models with the lowest CPI were selected for regional PV energy projections. The findings showed varying numbers of increase and decrease projected changes across the four regions under SSP245 and SSP585 scenarios for the near, mid and far future timescales. Specifically, in the SSP245 scenario, the model with lowest CPI was the CMCC-CESM2 model, it projected a decrease in PV energy in the Sahel (−2.30), an increase in the Guinea Savannah (+2.80), the Rainforest (+1.20) and the coastal region (+4.80) for the far future period (2085–2099). In the SSP585 scenario, the AWI-CM-1.1-MR model projected a decrease in the Sahel region (−4.60), while the MPI-ESM1-2-LR model projected an increase in the Guinea Savannah region (+1.80), and the ACCESS-CM2 model projected an increase in the Rainforest (+10.20) and Coastal regions (+13.20) for the far-future. All values in the parentheses are measured in watts-hour per square-meters. The projected changes in PV energy revealed the need for a regional-specific approach to the planning and implementation of energy transition mix in Nigeria.
{"title":"Simulation and projection of photovoltaic energy potential over a tropical region using CMIP6 models","authors":"Olusola Samuel Ojo, Promise Dunsin Adesemoye","doi":"10.1016/j.jastp.2024.106384","DOIUrl":"10.1016/j.jastp.2024.106384","url":null,"abstract":"<div><div>The study examines the potential impact of climate change on photovoltaic energy (PV) in Nigeria. Solar radiation and temperature datasets from 13 regional climate models (CMIP6) for 2015–2099 were used to evaluate the photovoltaic energy under moderate (SSP245) and high (SSP585) emission scenarios for near-future (2023–2053), mid-future (2054–2084), and far-future (2084–2099) periods. The precision of the models for the simulation of PV energy was validated with MERRA-2 reference data using the compromise programming index (CPI). Models with the lowest CPI were selected for regional PV energy projections. The findings showed varying numbers of increase and decrease projected changes across the four regions under SSP245 and SSP585 scenarios for the near, mid and far future timescales. Specifically, in the SSP245 scenario, the model with lowest CPI was the CMCC-CESM2 model, it projected a decrease in PV energy in the Sahel (−2.30), an increase in the Guinea Savannah (+2.80), the Rainforest (+1.20) and the coastal region (+4.80) for the far future period (2085–2099). In the SSP585 scenario, the AWI-CM-1.1-MR model projected a decrease in the Sahel region (−4.60), while the MPI-ESM1-2-LR model projected an increase in the Guinea Savannah region (+1.80), and the ACCESS-CM2 model projected an increase in the Rainforest (+10.20) and Coastal regions (+13.20) for the far-future. All values in the parentheses are measured in watts-hour per square-meters. The projected changes in PV energy revealed the need for a regional-specific approach to the planning and implementation of energy transition mix in Nigeria.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106384"},"PeriodicalIF":1.8,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698825","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 : 2024-11-15DOI: 10.1016/j.jastp.2024.106386
Sujatha Peethani , Mahesh Pathakoti , Mahalakshmi D. V , Ahmed MS. Kheir , Apoorva Singh , Ajit Govind
In Morocco, drought periods have become more frequent and severe due to climate change, which has had a substantial effect on freshwater supply and agricultural output. The El Niño-Southern Oscillation (ENSO) and the influence of climatic variability were the main subjects of the current study, which made use of daily precipitation, maximum and minimum temperature data collected at 50 locations around the nation from 1990 to 2022. The study analysed Palmer Drought Severity Index (PDSI) over Morocco to evaluate the impact of climate indices such as the Oceanic Niño Index (ONI) and the North Atlantic Oscillation (NAO) on drought severity. It also investigated the changes in precipitation, temperature, and extreme event-related indices. Rainfall is used as a proxy for El Nino and La Nina, supported by a negative and significant correlation between Oceanic Nino Index (ONI) and rainfall. Attempted to understand the impact of the NAO on Morocco's agricultural production, particularly during the winter months. During negative NAO phases, winter temperatures can lead to reduced wheat yields by 35–45% during the El Niño years and decreased by 4–7% during the La Niña years compared to the actual yield. Relying on the NAO plays a crucial role in modulating the precipitation patterns, which implies that crop requires adequate soil moisture with no extreme temperature during the growing season in order to produce higher yield. ENSO events can indeed lead to these extreme conditions in selected locations, potentially impacting crop yields.
{"title":"Variability of ENSO teleconnections indices, and its impacts on moroccan agriculture","authors":"Sujatha Peethani , Mahesh Pathakoti , Mahalakshmi D. V , Ahmed MS. Kheir , Apoorva Singh , Ajit Govind","doi":"10.1016/j.jastp.2024.106386","DOIUrl":"10.1016/j.jastp.2024.106386","url":null,"abstract":"<div><div>In Morocco, drought periods have become more frequent and severe due to climate change, which has had a substantial effect on freshwater supply and agricultural output. The El Niño-Southern Oscillation (ENSO) and the influence of climatic variability were the main subjects of the current study, which made use of daily precipitation, maximum and minimum temperature data collected at 50 locations around the nation from 1990 to 2022. The study analysed Palmer Drought Severity Index (PDSI) over Morocco to evaluate the impact of climate indices such as the Oceanic Niño Index (ONI) and the North Atlantic Oscillation (NAO) on drought severity. It also investigated the changes in precipitation, temperature, and extreme event-related indices. Rainfall is used as a proxy for El Nino and La Nina, supported by a negative and significant correlation between Oceanic Nino Index (ONI) and rainfall. Attempted to understand the impact of the NAO on Morocco's agricultural production, particularly during the winter months. During negative NAO phases, winter temperatures can lead to reduced wheat yields by 35–45% during the El Niño years and decreased by 4–7% during the La Niña years compared to the actual yield. Relying on the NAO plays a crucial role in modulating the precipitation patterns, which implies that crop requires adequate soil moisture with no extreme temperature during the growing season in order to produce higher yield. ENSO events can indeed lead to these extreme conditions in selected locations, potentially impacting crop yields.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106386"},"PeriodicalIF":1.8,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698826","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 : 2024-11-15DOI: 10.1016/j.jastp.2024.106385
Pratyush Agrawal , Adithi R. Upadhya , Srishti S , Mahesh Kalshetty , Padmavati Kulkarni , Meenakshi Kushwaha , V. Sreekanth
High-resolution air pollution maps can help researchers and governments better characterize and mitigate pollution levels in a given region. Land Use Regression (LUR) modeling is a statistical approach capable of predicting pollution levels at a high spatial resolution. In this study, we used pollution data (for the calendar year 2019) from a dense (compared to other Indian regions) regulatory monitoring network in Delhi, India, to develop simple linear and interpretable LUR models for various criteria pollutants. The observed annual mean PM2.5 and PM10 over Delhi were found to be ∼110 μg m−3 and 220 μg m−3, respectively. The PM concentration levels were 2.5–4 times higher than the prescribed national ambient standards, while the gaseous criteria pollutants were found to be within the standards (over most of the study area). The performance of the developed LUR models ranged from poor to moderate levels (adjusted-R2 values of the models were between 0.14 and 0.63). Land use and road-network related variables were found to be the most common predictors of the observed pollution levels. Moderately performing models (11 out of the developed 20) were then used to predict pollution levels at 50 m spatial intervals and to identify the most polluted districts. The advantages and limitations of using the existing regulatory network data for LUR development, and the other probable potential reasons responsible for the underperformance of the developed models are extensively discussed. To our knowledge, this is one of the few studies carried over Indian region to develop LUR models utilizing regulatory monitoring network data.
高分辨率空气污染地图可以帮助研究人员和政府更好地描述和减轻特定区域的污染水平。土地利用回归（LUR）建模是一种能够预测高空间分辨率污染水平的统计方法。在本研究中，我们利用印度德里密集（与印度其他地区相比）的监管监测网络提供的污染数据（2019 年），为各种标准污染物建立了简单的线性和可解释的 LUR 模型。在德里观测到的 PM2.5 和 PM10 年平均值分别为 110 μg m-3 和 220 μg m-3。可吸入颗粒物的浓度水平比国家规定的环境标准高出 2.5-4 倍，而气态标准污染物则在标准范围之内（在大部分研究区域）。所开发的 LUR 模型的性能从较差到中等水平不等（模型的调整 R2 值介于 0.14 和 0.63 之间）。研究发现，土地利用和道路网络相关变量是观测到的污染水平最常见的预测因素。然后，利用性能中等的模型（20 个已开发模型中的 11 个）来预测 50 米空间间隔的污染水平，并确定污染最严重的地区。我们广泛讨论了使用现有监管网络数据开发 LUR 的优势和局限性，以及导致所开发模型表现不佳的其他潜在原因。据我们所知，这是印度地区利用监管监测网络数据开发 LUR 模型的少数研究之一。
{"title":"Development of Land Use Regression (LUR) models and high-resolution spatial mapping of criteria air pollutants: Leveraging Delhi's continuous air monitoring network and remote sensing data","authors":"Pratyush Agrawal , Adithi R. Upadhya , Srishti S , Mahesh Kalshetty , Padmavati Kulkarni , Meenakshi Kushwaha , V. Sreekanth","doi":"10.1016/j.jastp.2024.106385","DOIUrl":"10.1016/j.jastp.2024.106385","url":null,"abstract":"<div><div>High-resolution air pollution maps can help researchers and governments better characterize and mitigate pollution levels in a given region. Land Use Regression (LUR) modeling is a statistical approach capable of predicting pollution levels at a high spatial resolution. In this study, we used pollution data (for the calendar year 2019) from a dense (compared to other Indian regions) regulatory monitoring network in Delhi, India, to develop simple linear and interpretable LUR models for various criteria pollutants. The observed annual mean PM<sub>2.5</sub> and PM<sub>10</sub> over Delhi were found to be ∼110 μg m<sup>−3</sup> and 220 μg m<sup>−3</sup>, respectively. The PM concentration levels were 2.5–4 times higher than the prescribed national ambient standards, while the gaseous criteria pollutants were found to be within the standards (over most of the study area). The performance of the developed LUR models ranged from poor to moderate levels (adjusted-R<sup>2</sup> values of the models were between 0.14 and 0.63). Land use and road-network related variables were found to be the most common predictors of the observed pollution levels. Moderately performing models (11 out of the developed 20) were then used to predict pollution levels at 50 m spatial intervals and to identify the most polluted districts. The advantages and limitations of using the existing regulatory network data for LUR development, and the other probable potential reasons responsible for the underperformance of the developed models are extensively discussed. To our knowledge, this is one of the few studies carried over Indian region to develop LUR models utilizing regulatory monitoring network data.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106385"},"PeriodicalIF":1.8,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142698824","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 : 2024-11-10DOI: 10.1016/j.jastp.2024.106383
Luís Tiago Medeiros Raunheitte , Emilia Correia , Jean Pierre Raulin , José Valentin Bageston
Here we present the characteristics of three distinct types of Gravity Wave (GW) events as detected in the low ionosphere using very low frequencies (VLF) radio measurements performed at the EACF, Brazilian Antarctic Station Comandante Ferraz (62° 5′ 6″ S, 58° 24′ 12″ W), on King George Island. GWs in the low ionosphere produce oscillations in the electron density, which can be detected as amplitude and phase fluctuations of the VLF signals. The properties of the GW events are obtained using Morlet's Wavelet analysis, which gives the period of the waves, and their occurrence time. The period and duration of the GW events obtained using the VLF technique presented good agreement with ones previously obtained from airglow observations from a co-located all-sky imager. The VLF detection of the mesospheric front showed the same morphology seen with the imager with four crests identified, and the wave activity presented similar period range (∼4–16 min) as observed by airglow (∼6 min) with a period peak of 14 min equal to the spectral analysis of the concurrent OH temperature data. The activity associated with the band event presented similar period of ∼10 min (imager observed 13 min), same duration of 4 h as well as peak intensity just before 05:00 UT. The ripple detection showed the same period of 8 min as the airglow observations and similar duration of around 25 min. By considering two distinct VLF paths it was also possible to analyze the direction and velocity of propagation for the mesospheric front event, which gives 96.0 (±4.8) ms−1 in the East direction in agreement with the velocity of ∼92 ms−1 in the Northeast direction obtained from the airglow observations.
{"title":"Characterization of gravity wave events detected in the low ionosphere at the Brazilian Antarctic Station","authors":"Luís Tiago Medeiros Raunheitte , Emilia Correia , Jean Pierre Raulin , José Valentin Bageston","doi":"10.1016/j.jastp.2024.106383","DOIUrl":"10.1016/j.jastp.2024.106383","url":null,"abstract":"<div><div>Here we present the characteristics of three distinct types of Gravity Wave (GW) events as detected in the low ionosphere using very low frequencies (VLF) radio measurements performed at the EACF, Brazilian Antarctic Station Comandante Ferraz (62° 5′ 6″ S, 58° 24′ 12″ W), on King George Island. GWs in the low ionosphere produce oscillations in the electron density, which can be detected as amplitude and phase fluctuations of the VLF signals. The properties of the GW events are obtained using Morlet's Wavelet analysis, which gives the period of the waves, and their occurrence time. The period and duration of the GW events obtained using the VLF technique presented good agreement with ones previously obtained from airglow observations from a co-located all-sky imager. The VLF detection of the mesospheric front showed the same morphology seen with the imager with four crests identified, and the wave activity presented similar period range (∼4–16 min) as observed by airglow (∼6 min) with a period peak of 14 min equal to the spectral analysis of the concurrent OH temperature data. The activity associated with the band event presented similar period of ∼10 min (imager observed 13 min), same duration of 4 h as well as peak intensity just before 05:00 UT. The ripple detection showed the same period of 8 min as the airglow observations and similar duration of around 25 min. By considering two distinct VLF paths it was also possible to analyze the direction and velocity of propagation for the mesospheric front event, which gives 96.0 (±4.8) ms<sup>−1</sup> in the East direction in agreement with the velocity of ∼92 ms<sup>−1</sup> in the Northeast direction obtained from the airglow observations.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106383"},"PeriodicalIF":1.8,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651724","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 : 2024-11-02DOI: 10.1016/j.jastp.2024.106381
Zulfaqar Sa’adi , Shamsuddin Shahid , Mohammed Sanusi Shiru , Kamal Ahmed , Mahiuddin Alamgir , Mohamad Rajab Houmsi , Lama Nasrallah Houmsi
In Sarawak, a region highly vulnerable to climate change, the translation of climate-induced changes in rainfall to river flow is non-linear, presenting a challenge for water resource managers. This research investigates the impact of climate change on hydrological processes in Sarawak, Malaysia, with a specific focus on assessing future spatiotemporal variations in streamflow. The families of Random Forest (RF) empirical models based on data mining techniques were compared and utilized to develop a continuous hydrologic model. Then, by incorporating rainfall and evapotranspiration future projection prepared based on RF past performance statistical downscaling, the top performing RF empirical hydrological model was used for future streamflow projection. The results showed that despite an expected increase in rainfall, the RFR (Random Forest by Randomization) empirical hydrological model demonstrated a potential decrease in river runoff due to heightened evapotranspiration demands associated with rising temperatures. The examination of climate-induced alterations in both rainfall and evapotranspiration patterns revealed a consistent decrease in river discharges during the early to middle period across Sarawak, followed by a shift towards an increasing trend by the end of the 21st century. The central region along the Rajang basin exhibited a prevailing decrease in river discharge, with contrasting patterns in the last part of the century. The northern region displayed diverse trends, with some basins experiencing decreases in river runoff despite augmented rainfall, emphasizing the heterogeneity in response. By employing empirical models, and projecting future scenarios, the study contributes to a better understanding of climate change impacts on hydrology in the region, essential for effective water resource management and environmental conservation.
{"title":"Comparative assessment of empirical random forest family's model in simulating future streamflow in different basin of Sarawak, Malaysia","authors":"Zulfaqar Sa’adi , Shamsuddin Shahid , Mohammed Sanusi Shiru , Kamal Ahmed , Mahiuddin Alamgir , Mohamad Rajab Houmsi , Lama Nasrallah Houmsi","doi":"10.1016/j.jastp.2024.106381","DOIUrl":"10.1016/j.jastp.2024.106381","url":null,"abstract":"<div><div>In Sarawak, a region highly vulnerable to climate change, the translation of climate-induced changes in rainfall to river flow is non-linear, presenting a challenge for water resource managers. This research investigates the impact of climate change on hydrological processes in Sarawak, Malaysia, with a specific focus on assessing future spatiotemporal variations in streamflow. The families of Random Forest (RF) empirical models based on data mining techniques were compared and utilized to develop a continuous hydrologic model. Then, by incorporating rainfall and evapotranspiration future projection prepared based on RF past performance statistical downscaling, the top performing RF empirical hydrological model was used for future streamflow projection. The results showed that despite an expected increase in rainfall, the RFR (Random Forest by Randomization) empirical hydrological model demonstrated a potential decrease in river runoff due to heightened evapotranspiration demands associated with rising temperatures. The examination of climate-induced alterations in both rainfall and evapotranspiration patterns revealed a consistent decrease in river discharges during the early to middle period across Sarawak, followed by a shift towards an increasing trend by the end of the 21st century. The central region along the Rajang basin exhibited a prevailing decrease in river discharge, with contrasting patterns in the last part of the century. The northern region displayed diverse trends, with some basins experiencing decreases in river runoff despite augmented rainfall, emphasizing the heterogeneity in response. By employing empirical models, and projecting future scenarios, the study contributes to a better understanding of climate change impacts on hydrology in the region, essential for effective water resource management and environmental conservation.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106381"},"PeriodicalIF":1.8,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587214","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 : 2024-11-01DOI: 10.1016/j.jastp.2024.106382
Gopi Krishna Podapati , Pushpalatha Tadivalasa , Sreenivas Pentakota , Dandi A. Ramu , Sagar V. Gade
The Bay of Bengal (BoB) is a potentially active region for the formation of the Tropical Cyclones (TCs) and accounts for about 6% of the global annual total number of tropical storms. These TCs occur during the pre-monsoon (March–May) and post-monsoon (October–November) seasons over the BoB. Among all the pre-monsoon cyclones that occurred from 1993 to 2019, we have identified that the “Viyaru” is a typical one originated in the southern BoB, propagated approximately through the middle of the bay, and made landfall over the northern BoB. The cyclonic storm Viyaru caused a basin-scale sea surface cooling of 0.35 °C by increasing the mixed layer depth by 3.5 m over the Bay of Bengal. An analysis of mixed layer heat budget terms infers that reduced short wave radiation and increased latent heat fluxes as the key factors responsible for basin-wide cooling associated with the Viyaru cyclone. We have also found that the enhanced entrainment processes even after the dissipation of the Viyaru cyclone had resulted in a post-cyclone basin-wide cooling tendency over the Bay of Bengal. The present study exemplifies the role of a pre-monsoon cyclone (Viyaru) in impacting the Bay of Bengal basin-scale variability of surface Physical Oceanographic variables and associated processes.
{"title":"Air-sea interactions and Bay of Bengal basin wide variability with respect to long tracked cyclone ‘Viyaru’","authors":"Gopi Krishna Podapati , Pushpalatha Tadivalasa , Sreenivas Pentakota , Dandi A. Ramu , Sagar V. Gade","doi":"10.1016/j.jastp.2024.106382","DOIUrl":"10.1016/j.jastp.2024.106382","url":null,"abstract":"<div><div>The Bay of Bengal (BoB) is a potentially active region for the formation of the Tropical Cyclones (TCs) and accounts for about 6% of the global annual total number of tropical storms. These TCs occur during the pre-monsoon (March–May) and post-monsoon (October–November) seasons over the BoB. Among all the pre-monsoon cyclones that occurred from 1993 to 2019, we have identified that the “Viyaru” is a typical one originated in the southern BoB, propagated approximately through the middle of the bay, and made landfall over the northern BoB. The cyclonic storm Viyaru caused a basin-scale sea surface cooling of 0.35 °C by increasing the mixed layer depth by 3.5 m over the Bay of Bengal. An analysis of mixed layer heat budget terms infers that reduced short wave radiation and increased latent heat fluxes as the key factors responsible for basin-wide cooling associated with the Viyaru cyclone. We have also found that the enhanced entrainment processes even after the dissipation of the Viyaru cyclone had resulted in a post-cyclone basin-wide cooling tendency over the Bay of Bengal. The present study exemplifies the role of a pre-monsoon cyclone (Viyaru) in impacting the Bay of Bengal basin-scale variability of surface Physical Oceanographic variables and associated processes.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106382"},"PeriodicalIF":1.8,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572801","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 : 2024-10-24DOI: 10.1016/j.jastp.2024.106377
Alicreance Hiyadutuje , Michael J. Kosch , John Bosco Habarulema , Xiangcai Chen , Judy A.E. Stephenson , Tshimangadzo Merline Matamba , Mpho Tshisaphungo
At Zhongshan (69° S, 76° E) Antarctica we investigate the sporadic ()-layer virtual height modulation, observed by an ionosonde, during the passage of the Medium-Scale Traveling Ionospheric Disturbances (MSTIDs), observed by a SuperDARN radar. Two events were identified, on 04 October 2011 at 07:00 - 12:00 UT and 29 February 2012 at 00:00 - 04:00 UT with periods of 15.0 and 12.0 min, respectively. The magnitude of average height modulation of the -layer was 3.7 to 17.1 and 0.5 to 7.3 km, respectively, with the same periods as the MSTIDs. Ray tracing during the events shows that the likely MSTID propagation was up to 300 km in the ionospheric -region. The computed ion vertical drift velocity using SuperDARN radar and magnetometer data, and -layer altitude modulation observed by the ionosonde have moderate to strong positive correlation of 0.71 ± 0.22 and 0.51 ± 0.16, respectively. We show that the MSTIDs polarization electric field, which is mapped down from the -region along the near-vertical magnetic field, moderately contributes to the modulation of the layer altitude via the drift mechanism.
{"title":"Observation of sporadic E layer altitude partially modulated by the Traveling Ionospheric Disturbances at high latitudes over Zhongshan station","authors":"Alicreance Hiyadutuje , Michael J. Kosch , John Bosco Habarulema , Xiangcai Chen , Judy A.E. Stephenson , Tshimangadzo Merline Matamba , Mpho Tshisaphungo","doi":"10.1016/j.jastp.2024.106377","DOIUrl":"10.1016/j.jastp.2024.106377","url":null,"abstract":"<div><div>At Zhongshan (69° S, 76° E) Antarctica we investigate the sporadic <span><math><mi>E</mi></math></span> (<span><math><mrow><mi>E</mi><mi>s</mi></mrow></math></span>)-layer virtual height modulation, observed by an ionosonde, during the passage of the Medium-Scale Traveling Ionospheric Disturbances (MSTIDs), observed by a SuperDARN radar. Two events were identified, on 04 October 2011 at 07:00 - 12:00 UT and 29 February 2012 at 00:00 - 04:00 UT with periods of <span><math><mo>∼</mo></math></span>15.0 and <span><math><mo>∼</mo></math></span>12.0 min, respectively. The magnitude of average height modulation of the <span><math><mrow><mi>E</mi><mi>s</mi></mrow></math></span>-layer was <span><math><mo>∼</mo></math></span>3.7 to <span><math><mo>∼</mo></math></span>17.1 and <span><math><mo>∼</mo></math></span>0.5 to <span><math><mo>∼</mo></math></span>7.3 km, respectively, with the same periods as the MSTIDs. Ray tracing during the events shows that the likely MSTID propagation was up to <span><math><mo>∼</mo></math></span>300 km in the ionospheric <span><math><mi>F</mi></math></span>-region. The computed ion vertical drift velocity using SuperDARN radar and magnetometer data, and <span><math><mrow><mi>E</mi><mi>s</mi></mrow></math></span>-layer altitude modulation observed by the ionosonde have moderate to strong positive correlation of 0.71 ± 0.22 and 0.51 ± 0.16, respectively. We show that the MSTIDs polarization electric field, which is mapped down from the <span><math><mi>F</mi></math></span>-region along the near-vertical magnetic field, moderately contributes to the modulation of the <span><math><mrow><mi>E</mi><mi>s</mi></mrow></math></span> layer altitude via the <span><math><mrow><mi>E</mi><mo>×</mo><mi>B</mi></mrow></math></span> drift mechanism.</div></div>","PeriodicalId":15096,"journal":{"name":"Journal of Atmospheric and Solar-Terrestrial Physics","volume":"265 ","pages":"Article 106377"},"PeriodicalIF":1.8,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553349","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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