Spatially Heterogeneous Changes in the Frequency and Intensity of Precipitation in Iran
DOI:
https://doi.org/10.26485/AGL/2025/118/1Keywords:
precipitation frequency, precipitation intensity, long-term precipitation periods, short-term precipitation periods, global mean surface temperature, IranAbstract
The total precipitation trend has been investigated by many researchers in Iran. However, it is important to consider short-term and long-term precipitation separately. This study analyzed trends in 12 indices of precipitation, including 1-day precipitation frequency (1-DPF) to 6-day-and-more precipitation frequency (6-DMPF) and 1-day precipitation intensity (1-DPI) to 6-day-and-more precipitation intensity (6-DMPI) during 1968–2017 in Iran. Additionally, their relationships with the global mean surface temperature (GMST) trend were investigated. Trends were detected using the Mann–Kendall test and Sen's slope estimator. The ordinary least squares regression was used to calculate the percentage change in frequency and intensity of precipitation with increasing GMST. Several important findings emerged from this study: (1) the frequency of long-term precipitation has decreased in most regions of Iran, indicating a reduction in the length of precipitation periods; (2) the intensity of short-term and long-term precipitation has also decreased in most regions, suggesting that Iran's climate has become drier during this period; (3) changes in the frequency and intensity of precipitation are spatially heterogeneous, with a more significant decrease in the southern regions compared to the northern regions; (4) in higher latitudes of Iran, the contribution of long-term precipitation has decreased while the contribution of short-term precipitation (one-day and two-day) has increased. In contrast, all precipitation periods have decreased in lower latitudes; (5) 1-DPF and 2-day precipitation frequency (2-DPF) increase with global warming, with an average sensitivity of 2.6% K-1 and 2.7% K-1, respectively, while the other ten indices decrease with global warming. Therefore, most of the precipitation indices have decreased along with global warming in Iran.
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