Document Type : Research Paper
Authors
1 Assistant Professor, Soil Conservation and Watershed Management Research Institute (SCWMRI), Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
2 Associate Professor,Soil Conservation and Watershed Management Research Institute,Tehran,Iran.
3 Climatology PhD graduate from University of Tehran
Abstract
The purpose of this research is to investigate the spatial-temporal variations of extreme temperature events in Iran. The data used in this study includes the daily average maximum and minimum temperatures from 123 synoptic stations during the observational period from 1988 to 2017. Additionally, it incorporates data from the CNRM-CM6-1 model for 2020 to 2060 under two scenarios: optimistic (SSP126) and pessimistic (SSP585). Calculating extreme warm temperature indices from 1988 to 1977 showed that, in general, for most stations, the frequency and trend of warm indices such as warm nights, warm days, the number of summer days, and the number of tropical nights has been increasing. The analysis of temporal changes in cold index events revealed that, overall, the trend for cold indices such as cold days, cold nights, and the number of frost days has been decreasing for most stations. An analysis of the frequency of the SU25 index event as one of the most common extreme warm indices showed that the highest occurrence of this index was 363 days for the Konarak (airport) station, while the lowest occurrence was 21 days for the Ardabil station. The maximum number of frost days (FD) is 179 days for the Sarab station, while the minimum occurrence is no frost days for some of the southwestern stations in the country. Based on the outputs of the CNRM-CM6-1 model for the ssp126 and ssp585 scenarios during the period 2060-2020, it has been determined that the trend of warm extremes in regions with higher elevations and latitudes does not differ significantly compared to regions with lower elevations and latitudes. Based on the findings from this study and similar research, it can be stated that Iran’s warm temperature extremes have increased over past and future periods, while extreme cold events in Iran are decreasing.
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