Synoptic Analysis of Thickness Patterns at the Time of Heavy and Extensive Precipitations of South Zagros Area

In order to recognize synoptic patterns associated with occurrence of 100 extensive and extreme precipitation events in southern Zagros moderate rainfall region, graded precipitation data extracted from Asfazare data base for the period of 1961/03/21 to 2004/01/31. Spatial resolution of precipitation data is 14*14 km in a daily base. Geo potential height in two different levels (1000 and 500 hpa) from NCEP/NCAR data base with a spatial resolution of 2.5*2.5 have been used. The synoptic framework set from 0to 12 and 0 to 80. In this study, an environmental to circulation approach has been used. Applying a cluster analysis on Euclidean distances of 1000-500 thickness using Ward method showed that 4 different thickness patterns are responsible for extreme and extensive precipitation events of southern Zagros moderate rainfall region. In all cases Mediterranean trough and eastern Iran's regions are responsible for baroclinicity in the western part of the country.