Document Type : Research Paper
Authors
1
Department of Natural Geography, Faculty of Geography, Kharazmi University of Tehran, Tehran, Iran
2
Moffateh St., Tehran, IRAN
3
professor of climatology, Department of Natural Geography, Faculty of Geography Sciences, Kharazmi University, Tehran, Iran
10.22034/gp.2025.65476.3355
Abstract
The main purpose of this research is to identify the days with heavy rains and to investigate the frequency of their in Iran occurrence . For this purpose, firstly, ERA5 hourly rainfall data with a spatial resolution of 0.25 x 0.25 degree was obtained for the years 1940 to 2023, and then the total daily rainfall and their seasonal breakdown were calculated, and then to separate the days A threshold of half a millimeter has been considered as rain or non-rain. And by using the 95th percentile index, the flood thresholds have been extracted. After extracting the seasonal thresholds for more detailed analysis, the thresholds were classified into seven classes, the first class has the lowest threshold and the seventh class has the highest threshold. The results show that the highest amount of threshold, i.e. rainfall above 30 mm, existed in all seasons of the year, but in terms of spatial coverage, it was more pronounced in the two seasons of autumn and winter, and in the summer season, it reached its minimum, which is less than one percent of the country's area. The lowest recorded threshold means rainfall less than 2 mm to 5 mm (first and second floor) existed only in the summer season and its spatial coverage has reached about 55% of the country's area. In terms of frequency, the main core of torrential rains is on the southern shores of the Caspian in the summer season, and in other seasons, in addition to the southern shores of the Caspian, it is located on the west, northwest, southwest and limited areas of the northeast.
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