Analysis of synoptic systems, causing floods in Golestan Province (Case Study: Flood in 11 August 2001)

In this study, flood in 11 August 2001 in the Golestan province of Iran based on daily rainfall data and atmospheric data in a series of NCEP/NCAR and ECMWF data were examined. For this purpose, potential vorticity maps at isotherm levels of 330 and 320 k, circulation patterns at 1000, 850 and 500 levels, convergence of moisture flux at 850 level, instability indices and cloud cover were mapped and analyzed. The results showed that in this day with spell of the cold air from the stratosphere to the troposphere caused intensify of potential vorticity in the region, as well as along with penetration of high elevation of the north Caspian Sea and transferring the moisture from the sea level to northern parts and entry of low height of Ganges and Persian Gulf from the southern parts and inject moisture to the region with the retreat of the high elevation subtropical caused the instabilities and therefore extreme precipitation in this day has been provided.