The New Features Of The Polar Vortex And Its Impact On Winter Temperature Of China

The NCEP/NCAR reanalysis data and the Hadley center dat are used to investigate the winter variation of the area, intensity and location of the whole and four regions of Northern Hemisphere polar vortex at500hPa、300hPa、200hPa and100hPa and the sea surface temperature in the North Pacific(20°～60°N,120°E～120°W) in April between1959～2009. Finally the synchronous and later correlation between the area and intensity of each level polar vortex, their relation with winter average and extreme temperature, the temporal and spatial connections and influence between SST and the polar vortex area and the relationship of the solarspot with the polar vortex are analyzed, The results are as followings, in recently50years:(1) The area size and intensity of Northern hemisphere polar vortex in winter at four levels increased at the beginning, which is followed by a decreasing trend, and the area mutated occurred in the middle1980s as the beginning of the global warming and intensity mutated occurred in the middle of1990s. Compared with the area, inter-decadal change of the intensity is weak. And the area and intensity of polar vortex at different layers have significant inter-decadal correlation. The polar vortex area of four layers all deviate from region Ⅳ(the Atlantic and Europe continental), and500hPa polar vortex deviate into region Ⅱ and Ⅲ (the Pacific Ocean and the continent of North America area), polar vortex at300hd、200hPa and1OOhPa deviate into region Ⅰ and Ⅱ (the Asian mainland and the Pacific Ocean), the center of500hPa polar vortex almost located in region Ⅱ or Ⅲ.(2) The area of polar vortex at100hPa is the biggest, and the intensity is strong at the same level, both of which have the largest seasonal amplitude, especially in region Ⅰ and Ⅳ. As to the annual variation, the maximum polar vortex area appears later while the minimum area appears earlier than other layers. And winter polar vortex area index at100hPa has a certain influence on the ones at500hPa、300hPa and200hPa in the next winter. In recent50years, under the background of global warming, the average temperature in winter and the occurrence of warm day (night) have a significant increasing trend, cold day (night) reduced significantly and the mutation occurred in the middle of1980s.(3)The winter average temperature and extreme temperature index have a significant correlation with the500hPa polar vortex area. The correlation between the temperature and area of the region I at500hPa is the most significant, the region I of300hPa、200hPa and region Ⅳ of 100hPa take the second place, which shows that the impact of polar vortex area on the winter temperatures is from the region IV of100hPa (Europe continent)in bottom of stratosphere to the region Ⅰ of500hPa(Asia continent) in the troposphere. The expansion of polar vortex area of region Ⅰ at500hPa lead to increases (decreases) the occurrence of cold day/night(warm day/night) in most of China, while the expansion of the polar vortex area of region Ⅳ Ⅳ at100hPa and region Ⅳ at500hPa lead to increases (decreases) the occurrence of cold day/night(warm day/night) in northern China. And the correlation between polar vortex area and occurrence of cold (warm) night is better than cold (warm) day, while the correlation between polar vortex area and cold day (night) is better than warm day (night).(4)We examine the first two EOFs (EOF1and EOF2) of North Pacific SSTAs, the spatial manifestation of EOF1is quite similar to the structure of the PDO and the EOF2is like the structure of dipole and then mutated occurred in the middle1980s. The spatial manifestation of the correlation between PVA and North Pacific SSTA is similar to the EOF2. The the central North Pacific SST is high (low) in the year before in April and north and south the SST is low (high), then the next year February region Ⅳ of100hPa polar vortex area of the larger (smaller). There is a relationship between the area of region Ⅳ of100hPa polar vortex and time series of EOF2, the year before last April and the related coefficient is bigger. All the correlation coefficient between adjacent two months SST index are all through the significance test, indicating that the North Pacific SST from the year before last spring to the same year winter is continuous.(5)There has a similar space response between the north Pacific SST anomaly in April before and the polar vortex area structure. And the north Pacific SST anomaly caused by troposphere atmospheric temperature anomaly, there is a obvious poleward spread trend in each levels. The year before last April north Pacific SST central SST anomaly slants cold, peripheral slant warm, corresponding to the same year February polar vortex area is reduced, At the same time with the Mongolian high abate, Aleutian low abate, east Asia tank weakened and AO is phase distribution. The configuration will lead to weaken winter the winter wind, as while the temperature will be reduce in China winter.