تحليل سينوپتيكي عوامل ايجاد بارشهاي سيل زا در استان گلستان

Synoptic Analysis of Heavy Rain Fall in Golestan Province

For studying the heavy rain fall in southeast of the Caspian Sea, the Meteorology Organization s daily synoptic maps on four surfaces (the earth, 850, 700 and 500 HPA) from 1992 to 2002 were used. The results showed that five kinds of air mass and pressure systems influence heavy rain fall in southeast of the Caspian Sea; European migrant high-pressure, Siberian high-pressure, Subtropical high-pressure, Moonson low-pressure and Sudan low-pressure. Therefore, necessary synoptic conditions for heavy rain fall in warm season in Golestan province consisted of cold air advection on the surface of the Caspian Sea by European migrant high-pressure and warm and wet convection from the east and southeast by Moonson low-pressure on the earth level. Descending cold air in divergence zones of north Russian trough in upper layers of atmosphere on the surface of the Caspian Sea. Penetration of European migrant high-pressure from northwest and descending of subpolar cold air and penetration of Sudan low-pressure tongues from south and southwest of the earth and penetration of subtropical high-pressure to central part of the Caspian Sea in middle atmosphere layers and to settle the Caspian sea in divergence zones of north Russian trough.