تحليل احتمالاتي خصوصيات مكاني شدت خشكسالي در استان تهران

Probabilistic analysis of spatial-temporal characteristics of droughts severity in Tehran Province

The severity and spatial characteristics of drought are two important factors that are crucial to be considered while developing drought contingency plans. This paper aims to investigate important Tehran province drought events from this view point using severity-area-frequency (SAF) curves and 3 months Standardized Precipitation Index (SPI). For this purpose, monthly drought maps were prepared for the period of 197I to 2005 and their spatial variations were assessed. The results showed that the 1971, 1982 and 1989 droughts have return periods of 3 to 5 years. While the 1990, 1999 and 2000 are representatives of 10 to 20 year return periods. Finally, the 1997 drought, which is the severest drought within the recorded period, was identified as 100 years return period. These droughts can be considered as relevant patterns to show spatial behavior of the province droughts. However to interpret these pattern, it is necessary to assess the monthly drought maps as well as SAF curves.