Activity Characteristics And Numerical Simulation Of Polar Vortex And Its Effect On Climate In China

Aimed at the important impact of polar vortex on weather, climate and environment, we studied deeply polar vortex by virtue of dada analysis, dynamical statistic diagnoses and numerical simulation. We pointed out the characteristics of polar vortex, and its relation to the subtropical high, blocking, Asian monsoon, made clear the effect of polar vortex on air temperature and rainfall in china, and explored the influence of the Pacific SST and Arctic sea ice to polar vortex. The main results show as following:(1) There is obvious inter-annual and inter-decadal variation for polar vortex, including the variation of area, intensity and location. Before middle age of 1970s, area and intensity index of northern polar vortex trend to rise, with small fluctuating, and after that, with clear undulating, it trend to minish. The center of northern polar vortex is not at Arctic pole. The center of polar vortex mainly displace towards Asia, departure form Europe, but stronger trend to the Pacific.(2) During the stratospheric warming events, pinched by anticyclone from middle latitude, stratospheric polar vortex will displace, distort or breakdown. By contrast, the change of stratospheric polar vortex is greater in the course of downward-propagating type than downward-propagating warming event: Also, troposphere circulation and polar vortex evolve in different degree, and usually both of them go with blocking, but the above evolvement in the downward-propagating warming is more distinct.(3) Polar vortex cooperate with other circulation factors, such as subtropical high, blocking, and monsoon. There are basically negative correlation between majority of polar vortex factors and main subtropical high indexes. Polar vortex and blocking usually have a negative interaction, and the interaction are more distinct in summer than in winter. When polar vortex area is larger, the Summer East Asian monsoon is stronger. If polar vortex remarkably strengthen, Winter East Asian monsoon weaken.(4) Polar vortex significantly impact the contemporaneous and subsequent air temperature and rainfall in China. The area of polar vortex mainly have a negative correlation with air temperature, while the negative relationshipbetween intensity and air temperature is not so strong. The influence of polar vortex on rainfall is weaker than on air temperature, but the effect on in the drainage area of Yangtse River and Yellow River is notable.(5) The Pacific SST observably affect contemporaneous and subsequent polar vortex, while polar vortex feed back on subsequent SST in the Pacific in great degree. The response of polar vortex to the key region SST lag 2 to 8 months, and the key region usually locate in the area of Nino.(6) The CAM is able to used in simulating polar vortex. Through experiment it is known that Polar vortex is sensible to the East Pacific SST and the Arctic sea ice. If the negative (positive) forcing of East Pacific SST is input, both area and intensity of polar vortex augment (minish). If positive (negative) forcing of the Arctic sea ice concentration, area index of annual polar vortex decline (ascend), but index of intensity ascend (decline).