پيش بيني سيلابها بر اساس موقعيتهاي سامانه هاي همديدي در شمال شرق ايران

Floods Prediction Based on Synoptic System in North- East IRAN

North- East Iran has been proved as a major agricultural pole and ranching center. It enjoys relatively optimum climatic conditions, and roughly falls into semi- humid to semi-dry climatic regions. However, despite its prime environmental and climatic characteristics, it is the scene of very devastating seasonal floods which take many lives and cause considerable damage to property and the environment every year. Thus, identification and evaluation of appropriate patterns resulting in storms and floods require considerable attention in this region. This will defmetly, in turn, facilitate resource management. Methodologically speaking, the study is based on long term precipitation data and relevant station discharges during a period of 30 years (1970-1999). Along with this, daily weather maps of upper as well as surface layers were analyzed. Results show the four following patterns pertaining to flood: 1 .European migrant low pressures, originating from Scandinavia. 2.Mediterranean Iow pressures. 3 .Sudani & Red sea low pressures. 4.Siberian migrant low pressures which originate from Arctic regions near to northern Siberia. The peak of precipitation is when low pressures prevail in the region. In other words when the region is under the influence of cold fronts. The continuation of rainfalls is associated with prevalence of the Red sea low pressure system along with either the Mediterranean low pressure or European Arctic low pressure simultaneously. This coincidence results in a mixed front per se.