Drought Monitoring in Tehran Province Using TRMM Satellite Data

Drought is a climatic phenomenon that affects different parts the environment during its continuation. Most drought assessment systems are mainly based on rainfall data. short statistical period of many data, insufficient density of stations and poor quality of ground rainfall data, reduces the ability show the spatial pattern of drought. the current paper aims at monitoring drought in Tehran province using rainfall network data. Thus, monthly precipitation data six synoptic stations in Tehran province and monthly precipitation data of TRMM satellite with spatial resolution of.25 × .25 degrees during the period (1998-2019) have been used. The results show that output of the 12-month SPI index for TRMM points is in good agreement with synoptic stations and the drought characteristics at different stations are consistent with different points of the TRMM network. In 36% of the study period, the rainfall in the province is in normal range and in 64% the rainfall is not normal. In all parts of the province, frequency dry and wet periods is equal and each of which with 31.8%. In terms of severity, most precipitation anomalies in Tehran province are mild and moderate, so that the frequency of mild drought is 18%, moderate drought is 9% and severe drought is about 4.5%. Extremely severe drought has not occurred in any part of the province in the last 22 years. Also, 2001, 2008, 2013 and 2014 are the most severe periods of widespread severe drought in the province, with most areas suffering from moderate to severe drought.