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Investigating the drought situation in Razavi Khorasan province using SPEI and VCI indices
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Mahsan Koroozhdeh1   , Karim Amininia *2 , Mehdi Saghebian3 |
1- Doctoral student of Climatology, Department of Geography, Ahar Branch, Islamic Azad University - Ahar-Iran.
2- Department of Geography, Ahar Branch, Islamic Azad University - Ahar-Iran.
3- Department of Civil Engineerin, Ahar Branch, Islamic Azad University - Ahar - Iran |
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Abstract: (13 Views) |
Introduction
Drought is a natural hazard that can have severe and long-term effects on natural and human systems. An increase in greenhouse gases is expected to change the characteristics of drought. Therefore, it is necessary to have a detailed understanding of drought and its changes at the regional scale. Droughts regularly led to major socio-economic and environmental impacts. Drought is one of the most severe natural hazards, and climate change causes droughts to occur in many regions of the world in the 21st century with a longer period. It is very important to monitor the drought in Razavi Khorasan province and understand its characteristics in the long term. The research results will have many applications in different sectors such as agriculture, water resources, environment, and agriculture.
Methods
To investigate the drought of the Khorasan Razavi province during a period of 40 years, the data of synoptic meteorological stations with a period of 40 years (1981-2020) have been used. The Spatio-temporal changes of drought the in Khorasan-Razavi province have been done based on the Standardized Precipitation Evapotranspiration Index (SPEI). The Penman-Monteith method has been used to calculate the potential evapotranspiration to calculate the drought. Finally, the frequency and intensity of the drought for the last four decades have been analyzed separately. Also, the VCI drought index, which is a remote-sensing drought index, has been used. This index is calculated using NDVI data from the MODIS sensor.
Discussion of Results
The results showed that the drought in Khorasan Razavi province has occurred with high intensity and frequency in the last 40 years. The highest frequency and intensity of drought was obtained in the third decade (2001-2010) with the maximum intensity of drought of -1.69 and frequency of 34.24%. A decades-long study of drought severity and frequency showed that the main climate feature of the province after the 2000s was moving towards a drier climate. In general, the potential evapotranspiration in Razavi Khorasan province has an increasing slope from north to south and west to east. The frequency of drought also shows a behavior similar to potential evapotranspiration in Razavi Khorasan province. The highest frequency of drought is seen in the southern and southeastern regions of the province with 26.51%. In other words, more than a quarter of the months of the year in these areas of the province are affected by drought. The simultaneous comparison of SPEI and VCI indices showed that precipitation-induced drought events (SPEI index) do not lead to vegetation-based drought in the province. Also, vegetation drought events (VCI index) do not occur as a result of a lack of precipitation.
Conclusions
Changes in the characteristics of drought based on the data of the last 40 years, including the frequency, intensity, and areas affected by drought, showed that the droughts of Razavi Khorasan province during the last 40 years show clear decadal changes. Based on the regional changes of drought, several regional differences of drought have been identified. The maximum frequency of drought in the first decade (1981-1990) compared to the fourth decade (2011-2020) has experienced an increase of 11.69%. Analysis of the satellite drought index showed that the drought patterns shown by SPEI and VCI agree to a large extent. the increase in drought in recent years shows that if the concentration of greenhouse gases continues along its current path, the risk of increasing drought-related tensions for natural and human systems in Razavi Khorasan province will increase greatly. Therefore, it is necessary to include programs such as water resources management and cultivation and irrigation calendar in the province-related programs.
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Article number: 7 |
| Keywords: Drought, SPEI index, VCI index, MODIS sensor, Razavi Khorasan. |
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Full-Text [PDF 1094 kb]
(9 Downloads)
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Type of Study: Research |
Subject:
Special
Received: 2023/12/15 | Accepted: 2025/09/18 | Published: 2026/01/13
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