Assistant professor Department of Physical Geographical ,University of Isfahan
M.A student climateology,University of Isfahan
Heavy rainfalls are one of the crisis couses.The crisis of heavy rainfall in arid area are strong .in this study Zayandehrood basin as a arid area have storng floods in recent years.Statistical analysis in this period(1972-2010) indicate March flood that is ocured with 646 m3/s discharge and standard indicis SFI=10.47, is the biggest flood .In this study thermodinamic and synoptic conditions are anylyzed by Raklif and Bradbari indices.The SKW-T chart and upper air data in 500 mb are used. Bradbury and Rackliff Index show values of -1.58 and 33.6 that indicated a high instability in basin region. In addition, pressure synoptic analysis showed that 500 mb synoptic conditions are favorable for the occurrence of flooding is in accordance with expanding Atlantic – Europe down words polar shift. The dominant meridional pattern over the Mediterranean region and Middle East is formed over the Mediterranean and the West, with an intense fall over Iran. Bradbary and Radcliffe the indexes are fit for forecasting heavy rainfall that may lead to flooding.