Investigating The Synoptic Patterns Effective in Drought and Wet Years in Central Iran

The main objective of this study is to understand atmospheric circulation patterns, responsible for the development of drought and wet periods. For this purpose, droughts and wet periods during the 30-year period were identified in the six synoptic stations in central Iran. The base component analysis using varimax method of data correlation matrix and during the five hPa geopotential height and sea level pressure was to identify the basic elements of the atmospheric circulation. Then, using cluster analysis method on these components are bonded into circulation patterns were identified drought and wet. The main component of the study showed that more than 42% of the variance drought geopotential height at 500 hPa data by expanding the width of the lower polar low is that high elevation areas such as southern Siberia high elevation and high elevation or pressure tab on the research area is the cold air, air filter and associated cloudiness and creates stability, low rainfall and the occurrence of drought. The principal component analysis showed that the wet period of the first component Maximum percent rise a major role in the circulation patterns that indicate negative step-polar and Siberian high pressure that has two separate bovine eye model and the remaining components are due to negative steps and positive cells indicative of atmospheric instability coming from the Mediterranean and the Black Sea and the Red Sea to penetrate into the area, causing the event to be wet.