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Research Article
Longitudinal Response of the Low-latitude Ionosphere to 2017 Sudden Stratospheric Warming Event
Issue:
Volume 9, Issue 1, June 2025
Pages:
1-8
Received:
6 January 2025
Accepted:
20 January 2025
Published:
10 February 2025
Abstract: The Earth's ionosphere, a crucial region for communication and navigation systems, is susceptible to disturbances driven by both external (solar and geomagnetic activity) and internal (atmospheric waves) forces. These internal forces are known to be amplified during SSW events, creating significant ionospheric perturbations. This study investigates the longitudinal response of the low-latitude ionosphere, specifically focusing on the EIA, to the 2017 SSW event. Addressing a gap in current understanding, this research analyzes the longitudinal variations in TEC within the African and Asian sectors during the February 2017 SSW, aiming to provide a more comprehensive global perspective on SSW-ionosphere coupling. Previous findings have suggested longitudinal variations in EIA behavior, and this study seeks to provide concrete evidence of the SSW's longitudinal impact on the ionosphere through TEC data analysis. Using TEC data obtained from GPS observations, this study reveals a strong ionospheric response to the 2017 SSW event, characterized by irregular perturbations with large amplitudes, particularly in the African sector. During the peak phase of the SSW, ionospheric TEC perturbations begin just a day after the peak in stratospheric temperature and manifest as a suppression of the EIA for approximately 72 hours (3 days), indicative of a downward vertical drift. This suppression suggests a modulation of the fountain effect, which is further supported by the observed response of the mean zonal wind. The observed longitudinal differences in TEC perturbations, with stronger effects over the African sector compared to the Indian sector, highlight the influence of local effects on the ionospheric response to SSWs. These local effects could encompass variations in the geomagnetic field configuration, differences in the background ionospheric density and composition, and regional differences in atmospheric wave propagation and dissipation. Regional variations in tropospheric weather patterns and land-sea distribution can further affect the generation and propagation of atmospheric waves that couple the lower and upper atmosphere. The day to day TEC variations are discussed in the context of upward/downward E×B drift. Therefore, the observed longitudinal discrepancies underscore the importance of considering these local factors when assessing the impact of SSWs on the ionosphere and related technological systems. This study contributes to a more complete understanding of the complex interactions between the stratosphere and the ionosphere during SSW events and their implications for global communication and navigation infrastructure.
Abstract: The Earth's ionosphere, a crucial region for communication and navigation systems, is susceptible to disturbances driven by both external (solar and geomagnetic activity) and internal (atmospheric waves) forces. These internal forces are known to be amplified during SSW events, creating significant ionospheric perturbations. This study investigates...
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Research Article
Droughts in the High Continental Climate of Central Asia
Issue:
Volume 9, Issue 1, June 2025
Pages:
9-18
Received:
12 January 2025
Accepted:
26 January 2025
Published:
11 February 2025
Abstract: Drought, one of the manifestations of emergencies, is a serious problem for Central Asia. Experts estimate that more than 70 per cent of the region's territory is considered vulnerable to natural disasters. Droughts are less frequent than floods, but affect more people. Over the past decade, 60 per cent of the population exposed to extreme weather events has been affected by drought. The most tangible impact of drought is on agriculture and food security in the region. Droughts are expected to become more frequent in Tajikistan, Turkmenistan and Uzbekistan due to projected temperature increases and longer periods of extreme heat and evaporation in areas with lower precipitation. In establishing drought monitoring and early warning systems in Central Asia and adapting drought prediction models, the monitoring of climate indicators and the availability of a rich and deep database of years is an important link. The purpose of this work is to monitor the probability of drought occurrence depending on the meteorological conditions of the Kafirnigan River basin in Tajikistan. The formation and dispersion zones of the Kafirnigan River differ significantly in their meteorological characteristics. The monitoring of droughts in the area of the river's formation and dispersion and their comparison with meteorological conditions allows establishing the existence of certain regularity between them. The results of such dependencies can form the basis for the development of drought early warning systems. A characteristic feature of the drought indices (SPI and SPEI) in the southern Tajik lowlands is their decreasing nature and the significant difference in the trends of change. Differences between SPEI-6 and SPI-6 are due to potential evapotranspiration (PET), which is determined by the difference between precipitation and evaporation. The similarity between SPEI and SPI in winter is reasonable because this is the period when PET tends to have the lowest ratio to precipitation, resulting in a functional approximation of SPEI to SPI. According to the same principles, the largest difference is observed in November, which covers the period from June to November, when PET is highest in relation to precipitation. It is found that for the period 1950-2023, monthly mean precipitation values are significantly lower and temperatures are higher than the climatic norm of the southern Tajik lowlands, leading to negative values of mean annual SPEI and SPI and favoring the occurrence of drought.
Abstract: Drought, one of the manifestations of emergencies, is a serious problem for Central Asia. Experts estimate that more than 70 per cent of the region's territory is considered vulnerable to natural disasters. Droughts are less frequent than floods, but affect more people. Over the past decade, 60 per cent of the population exposed to extreme weather ...
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Research Article
The Frequency of Droughts in the Rasht Valley (Tajikistan) Under Climate Change
Issue:
Volume 9, Issue 1, June 2025
Pages:
19-27
Received:
20 February 2025
Accepted:
28 February 2025
Published:
13 March 2025
DOI:
10.11648/j.ijaos.20250901.13
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Views:
Abstract: The geographical location of Central Asia, including the Republic of Tajikistan, makes the region highly vulnerable to various climate-related natural disasters, such as floods, droughts and mudslides, which significantly affect sustainable development and people's living conditions, including their access to adequate food and drinking water. Droughts, especially in their extreme forms, accelerate the development of desertification, the main cause of which is excessive anthropogenic pressure, which increases under conditions of prolonged and intense drought. In this context, the issue of developing and improving modern systems for monitoring and forecasting droughts, as well as preparing for and mitigating their consequences, becomes extremely important. The problems of droughts occurrence in two districts of Tajikistan (Rasht, Lakhsh) with developed agricultural industry depending on meteorological conditions with wide application of standardized drought indices are considered. It was found that the occurrence of drought in a specific area does not have certain regularity, but is determined by a combination of meteorological parameters. The dynamics of the Standardised precipitation index and the Standardised precipitation and evapotranspiration index in Rasht district for the period 1950-2023 is characterised by a constant trend. The results of studies of meteorological conditions of Lakhsh district for the period 1961- 2021 to identify the possibility of drought occurrence are presented. The trend of the drought indices shows an increase in humidity over the period 1961-2021. Despite the positive trend in humidity over the period considered, extreme and severe droughts of varying duration have been observed.
Abstract: The geographical location of Central Asia, including the Republic of Tajikistan, makes the region highly vulnerable to various climate-related natural disasters, such as floods, droughts and mudslides, which significantly affect sustainable development and people's living conditions, including their access to adequate food and drinking water. Droug...
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Research Article
Connectivity and Rotation of Entropicly Defined Clusters as a Measure of Hurricane and Tornado State
Issue:
Volume 9, Issue 1, June 2025
Pages:
28-43
Received:
24 December 2024
Accepted:
26 January 2025
Published:
21 March 2025
Abstract: A statistical physical model of the two basic properties of clusters within a hurricane their convectivity and rotation - reveals a relationship for the time evolution of a hurricane. Non-doppler data from NEXRAD surface radar imagery, of Hurricane Irma transiting over Florida, is decomposed into unique clusters based on an annealing process using entropy and energy differences between pixels. Application of the concept of entropic forces between a cluster’s pixels provides an estimate of the radial velocity of each cluster by application of Stokes’ theorem. The ratio of the characteristic rotation and convectivity, associated with radial flow, integrated over the extent of the hurricane, closely tracks the hurricane’s state, providing more time resolution than aircraft sorties alone allow. It is concluded that monitoring the rotational and convective state, in conjunction with the size of a cluster, is capable of quickly providing forecasters and others with changes in a hurricane’s state. It is also shown that entropic tornado state can be similarly described in terms of convectivity and rotation rate.
Abstract: A statistical physical model of the two basic properties of clusters within a hurricane their convectivity and rotation - reveals a relationship for the time evolution of a hurricane. Non-doppler data from NEXRAD surface radar imagery, of Hurricane Irma transiting over Florida, is decomposed into unique clusters based on an annealing process using ...
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,
Joshua Benjamin Wisdom
