عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In order to investigate synoptic patterns of heavy precipitations in Sistan va Baluchestan province, 24 year (1987-2010) daily data of 6 synoptic stations was retrieved from meteorology organization. Moreover, data like sea level pressure, geo-potential elevation of 500 and 850 milibars were exploited from NCAR/NCEP database and then required maps were prepared in Grads software. Generally, two patters have resulted in the heavy precipitations in this province.
In the first pattern which resulted in precipitations of December12, 1995, a cyclone with contour plot of 1017.5 and 1020 milibars crossed the Arabian Sea, 24 hours before the precipitation and caused humidity spreading toward the area. In 850 milibars, a cyclone above the country results in cold weather flow and a low pressure system with a 1500 geopotenial meter contour plot passed the Bangla Gulf and the Arabian Sea and supply the necessary humidity conditions for rising in this equilibrium level.
In the second pattern which resulted in precipitations of June 5, 2010, a large low pressure system is formed 24 hours before the precipitation over southern part of Asia, which also influence south eastern and southern parts of Iran. 24 hours before the precipitation, a low altitude center covers the area under study and supply humidity and instability. On the day of precipitations, study area in 850 and 500 milibars are affected by a trough of 1475 and 5850 geopotenial meter contour plot and results in precipitation of this pattern.