北极涛动对我国沙尘活动影响的年代际转折及机理

Dust storm is a disaster weather frequently occurring over China. Dust aerosols produced by dust storm not only disrupt human health, but also influence East Asian climate by modifying reflection, scattering, and absorption of solar and interacting with clouds. Arctic Oscillation (AO) exerts large impact on the outbreak of dust storm and the transport of dust aerosols over China through East Asian atmospheric circulation. Recently, some evidence indicate a decadal shift of the linkage between the AO and atmospheric circulation over East Asia at the beginning of 1980s. This decadal shift may imply a decadal shift of the relationship between the AO and the dust storm frequency over China. In this project, on the basis of dust observations and dust simulation results during 1961-2007, we will recognize the decadal shift of the correlation between the AO and the dust storm frequency over China, and then show the influence of AO on dust emission, transport, and deposition over China before and after this shift. Finally a mechanism of the decadal shift of the relationship between the AO and the dust activity over China will be concluded, by comparing the AO-related changes in surface parameters, mean atmospheric circulation, and synoptic scale disturbances before and after this shift, and analyzing the modulation of external forcings on the relationship between the AO and the dust storm frequency over China. The results will strengthen our knowledge of the reason for the interannual and interdecadal changes in dust storm frequency over China.

沙尘暴是我国常见的灾害天气。沙尘暴产生的沙尘气溶胶不仅对人类健康有严重危害，而且通过改变太阳辐射、云的物理和微物理特征进而影响东亚气候变化。北极涛动（AO）通过影响东亚大气环流系统进而影响我国的沙尘暴发生以及沙尘气溶胶的传输。近期研究发现，1980年代初期AO与东亚大气环流系统的相关关系存在年代际转折，这为AO对我国沙尘暴频次的影响产生年代际转折提供了背景。本项目基于1961－2007年沙尘观测资料和沙尘天气模拟结果，辨识年际尺度上AO指数与我国沙尘暴频次相关关系的年代际转折点，得出年代际转折点前后AO对沙尘起沙、传输和沉降等过程的影响，通过分析年代际转折点前后AO异常伴随的地表要素、平均环流场和环流场天气尺度扰动的变化，以及分析外源强迫因子对AO与沙尘暴频次相关关系的调控，得出AO对我国沙尘活动影响产生年代际转折的机理。研究结果将有助于理解东亚沙尘暴频次的年际、年代际变化的原因。

北极涛动（Arctic Oscillation，AO）是北半球中高纬度最为重要的大尺度环流因子，年际尺度上AO与中东、中亚和我国天气、气候变化存在紧密联系。本研究利用地面观测资料，检查了AO与东亚沙尘暴频次的相关关系的年代际变化。结果得出，年际尺度上冬季AO与4-7月塔里木盆地沙尘暴频次在1961-1982年为负相关关系（相关系数为-0.62，通过99%信度检验），在1983-2007年二者相关关系消失（相关系数仅为0.14）。AO与沙尘暴频次相关关系的年代际转折，反映了1980s初期冬季AO与春季东亚大气环流系统的关联发生了年代际转折。研究结果增强了AO对东亚沙尘暴频次变化以及东亚大气环流变化影响的认识。项目实施四年内，项目负责人发表相关SCI文章4篇，完成项目拟定任务。