Investigation and identification of synoptic patterns of pervasive and destructive floods in Iran

Iran has different rainfall conditions due to special geographical conditions and location, so that despite having a rainfall equal to one third of the global average rainfall, there is a sharp fluctuation in the rainfall regime. The purpose of this study is to investigate and identify the synoptic patterns of flood and destructive precipitation moles in the period 24 to 27 March 2019. For this purpose, daily precipitation data for 100 synoptic stations in the country that had significant rainfall during this period were obtained and analyzed from the Meteorological Organization. A level of 850 hPa was obtained from the site of the US National Center for Atmospheric and its maps were prepared and analyzed using Grads software. The results of the analysis of synoptic maps showed that in the study period, except for the northwestern region of Iran, the rest of the country was affected by a low pressure system of Mediterranean origin. The stretching of the Siberian high-pressure tongue on the Caspian Sea and the north of the country has created a pressure pattern on the border between the two air masses and has prevented it from spreading to the northwest. Also, the passage of this system over the Red Sea, the Persian Gulf and the Sea of Oman and the proper moisture supply by them, has greatly increased its instabilities. The intensity of rainfall in some stations has been such that the total rainfall of this period has been half the average annual rainfall of that station.