Geographical Research

Numerical weather forecasting models are used for forecasting and dynamic conditions analysis of atmosphere phenomena in recent years. This research investigates dynamic and thermodynamic conditions in heavier precipitation events in different synoptic patterns in the southern coasts of Caspian Sea using WRF model. Database precipitation events were formed. Super heavy and heavy precipitation groups were classified with regards of 25% and 50% probability. Sea surface pressures patterns were drawn for each super heavy and heavy precipitation group using cluster analysis and ward linkage. Total data for WRF model (pgb.f00 and grb2d) were derived from www.dss.ucar.edu. WRF model were run for 16 synoptic patterns in three processes ) WPS، WRFV3 and ARWpost). Atmospheric variables maps were drawn and compared and analyzed when the WRF model were forecasted precipitation amounts and precipitation patterns precisely. The results show that the wind velocity mean are less than 12 m/s and more than 15 m/s in synoptic patterns for high pressure systems and low pressure systems respectively over the Caspian Sea in super heavy precipitation group. The wind velocity mean are less than 10 m/s and more than 10 m/s in synoptic patterns for high pressure systems and low pressure systems respectively over the Caspian Sea in heavy precipitation group. When difference of 2m air temperature and SST is less than zero especially if the high pressures are located over the Sea، sensible heat is increased as its mean may be 200 w/m² and 350 to 400 w/m² in heavy and super heavy precipitation events respectively. It reaches 950 w/m² in extreme values of precipitation. The WRF model acted less precisely in forecast of amounts and precipitation synoptic patterns that have been generated by high pressure systems than low pressure system.