北极涛动异常对西北地区东部沙尘暴频次的影响

 利用西北地区东部沙尘暴日数资料、北极涛动指数资料、东亚高低空大气环流形势场资料，分析了沙尘暴日数与北极涛动的关系，进而研究了北极涛动异常年东亚大气环流分布特征，探讨了北极涛动影响西北地区东部沙尘暴的可能途径。结果表明：西北地区东部沙尘暴频次呈波动减少之势，20世纪80年代中期发生气候突变；北极涛动指数与西北地区东部沙尘暴频次显著负相关，二者年际、年代际变化都有较好的应关系，北极涛动正位相年，西北地区东部沙尘暴偏少，反之亦然。究其原因：北极涛动异常对东亚冬季风强度、东亚高低空气压场、风场分布形势有重要影响：北极涛动正位相年，东亚冬季风、蒙古高压均偏弱；500 hPa高度场上，春季西风带纬向环流占优势，极涡面积偏小，强度偏弱，贝加尔湖阻塞高压异常强盛，蒙古国及我国华北和西北地区位于贝加尔湖阻塞高压底部的暖区里，地面至高空西北风偏弱；在这种形势下，整个中高纬度冷空气势力较弱，活动次数偏少，不利于大风、寒潮天气的发生，因此沙尘暴频次也偏少。而北极涛动负位相年基本相反。

Effect of Arctic Oscillation on Sandstorm in the Eastern Part of Northwest China

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.