Assessment of Spatial and Temporal Variability of Extreme Temperature by ETCCDI Indices (North and West of Iran)

Extreme climatic events are associated with climate changes. Understanding the diversifications in these events is important in planning to reduce their effects. In this research, using daily temperature data of 8 synoptic stations in the north and west of the country, 18 extreme temperature indices as defined by the Expert Team on Climate Change Detection Indices (ETCCDI) were evaluated. The results showed that the temperature intensity indices at night had a higher trend than the temperature intensity indices during the day. The frequency of the hot night index and hot day index in most of the studied stations had a significant increasing trend. Moreover, the cool night frequency index had a negative and significant trend in the north and west of the country and showed a higher trend in the north of the country than in the west. The cool day frequency index was negative for both study areas. Cold extreme indices including the number of cold days, number of frost days, and cold spell duration index were obtained in both regions of the country with a negative trend. While warm indices showed the number of hot days, warm nights, and warm spell duration index with a positive and significant trend.