Analysis of Dynamic, Thermodynamic, and Synoptic conditions of heavy rainfall Events in the South-East of Iran

Iran is a country with arid and semiarid climates, so its average annual rainfall is about one third of the average annual rainfall in the world. Besides, the eastern and south-eastern regions of Iran are one part of this climate whose main features is the high intensity precipitation. In the present study the daily precipitation data of 54 climatic stations in the eastern and south-eastern regions of Iran with more than 10 statistics years are provided. The data were provided in standardized Matlab software 2 matrix with the arrangement of 20824٭54 (row*column) in which the rows represent the number of days while the columns represent the statistics of rainfall stations. Using recent matrix data, a cluster analysis was done by Ward linkage method and Euclidean distance. At the end, 14 one-day rainfall events with magnitude greater than 70 mm were­ detected as a representative of heavy and pervasive rainfall events. The six-hour data includes geopotential height, sea level pressure, temperature, specific humidity, u wind and v wind, between 0 to 80 degree of northern latitudes and 0 to 120 degree of eastern longitude were used to recognize the dynamic, thermodynamic and synoptic factors affecting the occurrence of rainfalls. Then, the maps of spatial patterns have been drawn with the resolution in cell size of 2. 5٭2. 5 degree. The findings showed that torrential rainfall events over eastern and south-eastern parts of Iran are made of one or several different circulation patterns, while the most of the torrential rainfall events mostly provide confrontation of polar low-pressure with Sudan-Saudi low pressure which make the conditions of extreme pressure in northwest-southeast direction.