Study of influence of Arctic Oscillation (AO) Index on Siberian High Pressure and their probable impacts on precipitation in southern coastal region of Caspian Sea
Subject Areas : Marine Physics
T.
Azizian
1
(Dep. Of Meteorology, Faculty of Marine Science & Technology, Islamic Azad University, North Tehran Branch)
A.
Askari
2
(Dep. Of Science & Meteorology Research Center)
Keywords: Precipitation, Arctic Oscillation, Siberian High, teleconcections, southern coasts of Caspian Sea,
Abstract :
In this research, to investigate the relationship between AO (Arctic Oscillation) index and Siberian high pressure and the impact of it on the amount of rainfall in seven synoptic stations that have the ability to cover the southern coasts of Caspian Sea, we used 30- year period (1976 to 2005) precipitation data of those stations using correlation and regression analyses. We also used mean sea level pressure maps to analyze synoptically some special cases of extreme rainfalls. Our obtained results showed significant correlation at 95% level between extreme rainfalls and AO indices and also between rainfall and extreme AO indices in some stations of this region at monthly, seasonal and annual scales. In this context, using multiple regression analysis, rainfall was considered as the dependent variable and features of Siberian high pressure considered as independent variables. Results of this analysis showed that there is a strong relationship between precipitation and features of Siberian high pressure for eastern stations of the region under study in January and February. This relationship was quite evident for western stations in October. In most cases, coefficient of correlation of rainfall with central pressure of Siberian high was negative and, with latitude it was positive. Multiple regression analysis between AO indices and features of Siberian high pressure showed negative relationship between central pressures in Siberian high with AO indices and positive relationship between longitude of Siberian high pressure centers and AO indices in most months of autumn and winter.
