The Study Of The Circulation Mechanism About The Arctic Sea Ice Anomalies Influence The Extreme Low Temperature Over The Tibetan Plateau

In this paper, the observed monthly sea ice concentration fields are obtained from the Hadley Centre Sea Ice data set (1979—2012). Air temperature, geopotential heights, and wind (monthly fields) are obtained from the latest reanalysis of the European Centre for Medium Range Weather Forecasts (ERA-Interim,1979—2012). The daily maximum temperature and minimum temperature (1979—2012) including 125 stations in the Tibetan Plateau (TP here after) are selected. According to the relevant statistical analysis, synthesis analysis, and numerical model simulation, the variation characteristics of Arctic sea ice and its influence on the temperature is explored. Menawhile, the relationships between the number of cold days (TX10P) and cold nights (TN10P) in the TP region and the key area sea ice in the Arctic are systematically analyzed. The main results are as follows:1) In the last few decades (1979—2012), sea ice coverage in both autumn and winter is relatively stable. The arctic sea ice in summer—autumn has the obvious interdecadal variation, and it decreases in the early 21th century. The reduction of the arctic sea ice in summer—autumn causes the weakened Aleutian and Iceland low pressure in autumn—winter and the strengthened Siberia high pressure. Middle and high level near the Novaya Zemlya and Greenland have significant abnormal high— pressure, leadingthe frequentl cold winter in Eurasia.2) The extreme cold days of TP in autumn—winter become more frequent in the low sea ice value years of the key region in summer—autumn. It can be seen that the 500 hPa height field shows the positive correlation between the Arctic and the Siberia, and the negative correlation between the Arctic and the TP. From the polar to the TP, there is a clear flux fluctuation from north to south, and the high pressure and anticyclone system in Siberia area become stronger. The TP is mainly controlled by the flow from north to south. In the low sea ice years, Rossby wave presents a fluctuation trend from north to south over the TP, and the cold air is liable to attack TP, leading more extreme cold weather in the region.3) NCAR—CAM5.1 model simulation results show that, as both sea ice and sea surface temperature forcing of the key area on the Arctic in summer—autumn are enhanced, in the polar and TP region,500 hPa geopotential height field decreases and the geopotential height on Eurasia is increased. There is significant northerly winds on the TP, and high pressure anticyclone system is significantly increased in the high latitudes of Eurasia. In north of TP, the both temperature negative anomaly and the meridional activities are significantly enhanced, and it becomes the stronger cold source. The Arctic 1000—500 hPa thickness increases reduce the meridional thickness gradients from the Arctic to midlatitudes, resulting in a weaker westerly flow in high latitude areas. Polar vortex became stronger over the Arctic, and brough more cold air in the TP.