Anomalies of precipitation and drought in objectively derived climate regions of Iran

By regionalizing precipitation in 113 synoptic stations Iran, the characteristics of precipitations and occurrence droughts each region were investigated over a period 30 years, 1988–2017. Elevation, latitude distance from moisture source have caused strong East–West South–North gradients across territory Iran so that average annual increases 55 mm eastern central regions to 1,730 south-west coast Caspian Sea. Hierarchical cluster analysis identified six including arid, semi-arid, moderate, semi-humid, humid, high humid regions. An investigation standardized index (SPI) showed trend about 19 per cent was significantly decreasing. It non-significantly decreasing 65 cent, increasing less than 1 15 stations. While drought has increased most parts it decreased some only northern strip country. The line slope more 84 represent negative values SPI, which confirms an increase Iran.