Abstract

Eighteen climate indices were computed and utilized to demonstrate the spatial and temporal variations of climatic crisis, including amount, frequency, and intensity of various climatic events over the mountainous region in Iran. The variation of daily temperature and precipitation were investigated to identify significant changes during 1976-2007. Temperature extremes showed consistent warming patterns over most of the study region with which a large proportion of weather stations have presented statistically significant trends for all temperature indices. The comparison between hot and cold extremes showed that in most stations daily minimum temperature increases as daily maximum temperature increases. The variation of precipitation patterns also exhibited noticeable changes as altitude increases in the northwest of Iran during the study period. Although most of the weather stations, including Ardebil (ARD), Oroomiye (OR), Tabriz (TA), and Zanjan (ZA) showed that amount, frequency, and intensity of precipitation have consistently declined over time, such trends in Doshan (DO) and Mehrabad (ME) stations showed reverse, which is increasing. Since major water resources in this region are highly dominated by the amount of precipitation, further investigation on weather extreme is critical to manage water systems during uncertain hydrologic events, such as flood and drought. The results imply that water shortage in the northwest of Iran is likely to occur and chances of flood driven by weather extremes are even more likely, perhaps due to climate change.