Document Type : Original Article
Authors
1 Assistant Professor,, Department of Engineering,, Bozorgmehr University of Qaenat,, Qaen,. Iran.
2 Assistant Professor, Department of Engineering, Bozorgmehr University of Qaenat, Qaen, Iran
3 Assistant Professor, Department of Civil Engineering, Zabol University, Zabol, Iran
Abstract
Meteorological drought, as the initial stage of the broader drought process, is a significant climatic hazard with far-reaching implications for environmental sustainability. This study aims to evaluate the trend of meteorological drought in Qaen City, located in South Khorasan Province, over a 37-year period (from the 1988 to 2024 water years). For this purpose, annual precipitation and temperature data, along with two indices—the Percent of Normal Index (PNPI) and the Standardized Precipitation Index (SPI)—were used to analyze drought conditions in the region. According to the results, the average annual precipitation of the region was 161.30 mm (with a coefficient of variation of 37%), indicating high fluctuations in yearly precipitation and the occurrence of years with unusually high or low precipitation. Analyzing the trend in annual precipitation using linear regression, the Mann–Kendall test, and Sen’s slope method revealed no significant trend in precipitation values. However, the annual average temperature showed a significant upward trend, increasing at a rate of 0.078(°C)⁄year. Based on the PNPI and SPI indices, approximately 41% and 16% of the years, respectively (especially after 1999), experienced drought conditions. Wet periods were more frequently observed during the years 1990–1999, as well as in 2019 and 2020. The comparison of two drought indices reveals general agreement during extreme conditions but differences in normal years, as SPI provides a more conservative description of conditions. The study’s overall findings indicate a rising temperature trend, unstable precipitation patterns, and frequent drought occurrences in the region, highlighting increasing climate variability.
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