A Synoptic Analysis of Cyclonic Activity During 1961-2003

Abstract

Mid-latitude cyclones play an important role in precipitation over Iran. A survey on 6-hourly geopotential height of 1000 hPa level showed that the number of cyclones in the studied area reveals a positive trend. In this study a cyclone is considered as a low center with a regional geopotential gradient equal or greater than 100 gpm per 1000 km. Applying the procedure on NCEP/NCAR data a cyclonic center of action appeared to be exist over Iraq. Appearnce of such center of action seems to have remarkable concequences for climate of Iran.

Keywords

• extratropical cyclon
• cyclonic center
• geopotential height
• iran