An Assessment of Spatial and Temporal Changes in Precipitation and Drought in Iranian Synoptic Stations of Iran

The temporal and spatial variability of rainfall within and between years is a characteristic of Iran's climate. The aim of this study was to investigate the PCI, SPI, RDI and MFI indices and map their spatial variations. These data were obtained from the Meteorological Organization of Iran. The results idicated that the PCI index had an upward trend in 50% of the stations and a downward trend in the remaining stations. The lowest value of the PCI index was observes for the northern regions in 1992 at the Rasht Station (9.22), and the highest value for southeastern regions in 2008 at the Bandar Abbas Station (76.36). The MFI index had a downward trend of 28 stations with the lowest value of the MFI index in 2010 at the Yazd Station (4.42) and the highest value in 2001 at the Yasuj Station (451.65). According to the PCI index, the rainfall pattern at most of Iran's synoptic stations is seasonal and completely seasonal. The results of drought indices indicated that the SPI and RDI indices were higher in the western regions than the other regions. The severest drought based on both indices was observed at the Bushehr Synoptic Station in 2010. The values of these indices were (-3.4) and (-3.3), respectively. The results also indicated that the RDI index revealed a more severe drought conditions. As the RDI index includes air temperature as a direct factor affecting drought, it is recommended to replace the SPI index with this one. The Fornieh Rain Erosion Map maybe of great help to watershed managers and natural resource experts in planning soil conservation, erosion control, and land use schemes.