Study of spatial and temporal rain and drought patterns in the south of Iran using TRMM

Droughts are one of the most damaging climatic phenomena, and the most complex natural hazard  which affects the economy, agriculture, public health and environment in large areas. The aim of this study is to compare drought indicators derived from tropical rainfall measuring mission (TRMM) data in the south of Iran. Also the TRMM rainfall was considered, so as to investigate changes in the rainfall pattern over the area. In this study, five meteorological drought indices, including the standard precipitation index (SPI), deciles index (DI), z-Score, Standard Index of Annual Precipitation (SIAP) and Percent of Normal Precipitation Index (PNPI) derived from TRMM data at 0.25° × 0.25° spatial resolution are compared to monitor droughts in the South of Iran. The results showed that the SPI index was strongly correlated with other drought indices. The maximum relation of the SPI index with other drought indices was investigated, and the PNPI Index was found to have the most correlation, with a correlation coefficient of R = 0.995 and a coefficient of determination of R2 = 0.99. Also a strong inverse relationship was observed between rain and longitude while altitude and latitude were found to be poorly related.