|
چکیده
|
Changes in precipitation characteristics in Iran and their relationship with global mean surface temperature (GMST) have not been comprehensively investigated. Therefore, this study analyzed changes in precipitation of different intensities over Iran for the 1987–2017 period. The results show that the total annual precipitation (PRCPTOT) and the number of wet days (RR) have signifi cantly decreased over Iran. Also, the mean precipitation intensity (SDII) has increased somewhat. There is a non-uniform change for three intensity categories of precipitation. The amounts (frequency) of light, moderate and heavy precipitation have signifi cantly decreased at, respectively, 47% (57.9%), 18.7% (15.8%) and 3.94% (7.9%) of stations. Therefore, the decrease in the amount and frequency of light and moderate precipitation is more severe than that of heavy precipitation, and the proportion of heavy precipitation to the total annual precipitation has increased somewhat during 1987–2017. Overall, the result shows that the intensity of decreasing trends in the amount and frequency of precipitation has increased from the south (east) to the north (west) of Iran. Also, SDII has increased from the south (east) to the north (west) of Iran. The sensitivity value was obtained by calculating the ratio of linear trends of precipitation indices and GMST. The regional median sensitivity and percentage change in PRCPTOT, RR, and SDII per 1-kelvin increase in GMST are –6.1%, –11.2% and 12.9% respectively. Considering that Iran is located in the arid subtropical region, a signifi cant decrease in the amount and frequency of precipitation may have destructive effects on water resources.
|