Synoptic analysis of Caspian torrential rains, Case Study: Winter floods in 2012 Noushahr

Torrential rains in the southern Caspian Sea, has been of interest for researchers and different solutions have been offered. The analysis shows that thesuggested mechanisms are all derived from a single model. These theories are different only in appearance. This single model is the basic mechanism of the Caspian Sea rainfall in autumn and winter. Torrential precipitation more occurs in autumn and less in winter. In this paper, winter floods in Noushahr city in 2012 have been studied. By posing different theories governing the precipitation of the Caspian Sea, next to one another, the pattern was introduced for the torrential rains. Results indicated that the floods were caused by the passage of low pressure systems from the North Caspian Sea. Low pressure cold front has passed over Noushahr on 11 November 2012. The cold front on 12 November 2012, located near the center of Iran, at 35 latitude. With the influx of cold air behind the cold front caused floods in Noushahr city. Cold advection over the sea caused too much moisture absorption by the air. The results also showed that the ridge of high pressure that immigrated from the north Mediterranean had important role in the passage of the cold front is Noushahr city. The ridge is moving cold front to lower latitude finally passes through the north of Iran. The cause of ridge formation was cold air advection on the Caspian Sea.