A spatial analysis of the relationship between atmospheric components with dry and wet periods in northern coasts of Iran

Identifying the relationships between atmospheric components and the amount of rainfall can be one of the appropriate methods to predict rainfall periods. This study aimed to identify risk factors of dry and wet periods in the coasts of the Caspian Sea. Therefore, synoptic pattern was studied to spatial analysis of the relationships between atmospheric components in dry and wet periods in northern coasts of Iran. Monthly precipitation data was processed from 1361 to 1385 in a 25-year period (1981-2005) by examining seven stations in the southern coasts of Caspian Sea from East to West. By studying the temporal distribution of rainfall, 5 dry months and 5 wet months were chosen. APHRODITE rainfall data by 0.25×0.25 degree segregate and reanalyzed atmosphere data of National Center Environmental Prospect NCEP/NCAR by 2.5×2.5 degree horizontal segregate were used in order to analyze the atmosphere structure and recognize its dominant mechanism. In this study , in order to spatial analysis of the relationships between atmospheric components in dry and wet periods periods in northern coasts of Iran, several variables are used to better understanding this issue . The examined components in this study include the pressure of sea level, geopotential height, specific damp, orientation and meridional wind component, omega and rainfall that their maps of correlation and rainfall were prepared. The study of area synoptic situation shows a significant correlation between rainfall and deployment stack on the Black Sea. In addition, the existence of special damp and air ascendant and northern winds can be considered as a chain that these variables together lead to the onset of the wet area. The creation of high pressure on the Oman Sea and the Persian Gulf and strengthen South winds can be promising for dry periods in northern coasts of Iran.