Regions of Iran with Persistence of Precipitation

In the present research, for studying the continuity of Iran’s precipitation, the daily precipitation data of 1437 synoptic, climatic and rain gauge stations in the time period of 1961/3/20 up to 30.12.2004 (15992 days) have been used. These data were interpolated on the area of Iran by using Simple Kriging method in a regular network of 15 * 15 kilometers. Then, based on the conventional criteria of rainy day (≥0.5mm/day), precipitation persistence of Iran together with their share in providing precipitation and the rainy days at each point of Iran(7187 points) have been estimated. Then the different points of Iran, with respect to the share of precipitation persistence in providing rainy days and precipitation have been compared and zoned. Therefore, based on the rainy day (0.5mm and more in a day and night).The rainfall persistence in Iran was vary from 1 day up to 45 successive days. The percentage share of each persistence (45) in providing rainy days and precipitation in Iran (7187 points) were estimated and with R7187*90 array is the basis for Iran’s zoning. Performing cluster analysis on the Euclidian distances of this matrix by combination Ward method indicates that, based on the control of rainfall persistence in Iran’s regions, there are five relatively homogeneous regions. The geographical order of these regions illustrates dependence of Iran’s rainfall quantity on geographical unevenness, closeness to humidity sources and the effect of seas. Statistic tests such as homogeneity test confirm the correctness of this region division.