Summer precipitation determinant factors of Iran's South-East

Abstract

Indian Ocean is known as a source of moisture for southeast of Iran due to summer precipitation. In this study, in order to investigate the role of SST of Indian Ocean, and the convergence and divergence fields in the precipitation of southeast of Iran, precipitation data of five synoptic stations were used during 2000-2010, including Iranshahr, Khash, ChahBahar, Zabul, and Saravan. To investigate synoptic circumstances of precipitation, different atmospheric levels of data was obtained from National Oceanic and Atmospheric of United States (NOAA) website with the horizontal resolution of 5.2 degree. Afterward, maps of wind, heights, and moisture flux were prepared. The results show that these three important factors (including Indian Ocean surface temperature (SST), convergence and divergence fields, and monsoon returned east jet stream) have one important role in the summer rainfall event for the study region. In addition, summer precipitation is influenced by the wet and shallow summer monsoon, sea surface temperatures, and convergence and divergence in continental regions. East jet stream have also been effective in these regions. Summer rainfall patterns. have played roles in this region, including the convergence of the wind in southeast of Iran and the divergence of wind in the southeast of Arabian Peninsula in first pattern. The above circumstances as well as high temperatures of sea surface are considered in second pattern, and high sea surface temperature and the monsoon East jet stream in third pattern.