关键词: 北极涛动, 东亚冬季风, 大气环流异常, 西北地区东部, 沙尘暴频次

Abstract:

The data of sandstorm days in the eastern part of Northwest China, Arctic Oscillation (AO) Index and high/low atmospheric circulation fields in East Asia were used to analyze the relationship between sandstorm and AO, to study the distribution characteristics of atmospheric circulation in abnormal phase of AOI, and to discuss the possible way of AO influencing the sandstorm frequency in the eastern part of northwest of China was discussed. The result indicated that the days of sandstorm in the study area was decreasing and has occurred a jump phenomenon in the mid-1980s. There was remarkable negative correlation between AOI and the days of sandstorm. In high index phase of AO, the days of sandstorm were less, and vice versa. It was found that AO played an important role in the changes of the East Asian winter monsoon, the pressure and wind fields in East Asia. In high index phase of AO, the East Asian winter monsoon and Mongolia high were weaker; at height of 500 hPa, zonal circulation was dominant in the Westerlies in spring; polar vortex area was smaller and it's intensity was weaker; the blocking high of Lake Baikal was powerful exceptionally; Mongolia and North China as well as northwest area in China were located in the warmer sector of blocking high of Lake Baikal, resulting in weaker northwest wind. Under these conditions the intensity of cold air was weaker and the frequency of the cold air was less, which were not favorable for the occurrence of gale and cold wave. So the days of sandstorm were less. Whereas the case was generally opposite in the low index phase of AO.

Key words: Arctic Oscillation, East Asian winter monsoon, abnormity of atmospheric circulation, the eastern part of northwest China, sandstorm frequency