青藏高原春季积雪对北半球夏季季节内振荡的影响

Influence of the Qinghai-Xizang Plateau Spring Snow Cover Variation on the Boreal Summer Intraseasonal Oscillation

利用中国科学院西北生态环境资源研究院提供的1981-2016年雪深资料,分析了青藏高原春季雪深异常对北半球夏季季节内振荡(Boreal Summer Intraseasonal Oscillation,BSISO)的影响。BSISO包括周期为30~60天的BSISO1模态和周期为10~30天的BSISO2模态。结果表明,当青藏高原积雪偏多(偏少)时,与BSISO1相关的对流在印度、孟加拉湾以及“海洋性大陆”(Maritime Continent,MC)区域偏多(偏少),而在南海和西北太平洋区域偏少(偏多);与BSISO2相关的对流在北印度洋、MC以及东海南海区域偏多(偏少),而在西北太平洋区域偏少(偏多)。高原积雪可以通过改变背景风场以及湿度场来影响BSISO1的对流活动。当高原春季积雪异常增多(减少)时,垂直东北风切变在北印度洋区域增强(减弱),北印度洋与孟加拉湾间的湿度梯度增加(减小),有(不)利于与BSISO1相关的对流活动传播到孟加拉湾及MC区域;MC区域水汽减少(增多),不(有)利于与BSISO1相关的对流活动继续传播到南海和西北太平洋区域。

Snow cover over the Qinghai-Xizang Plateau(QXP)is an important physical factor that affects the Asian monsoon system through atmospheric circulation.The boreal summer intraseasonal oscillation(BSISO,including a 30~60-day BSISO mode named BSISO1 and a 10~30-day BSISO mode called BSISO2)is an essential part of the monsoon system,its convection and circulation anomalies can affect the local precipitation by changing the background conditions of the weather system.In this study,the snow depth data from 1981 to 2016provided by the Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences was used to analyze the influence of the Qinghai-Xizang Plateau snow depth anomaly on BSISO.The results show that the convective activities related to BSISO1 is enhanced(reduced)in the Bay of Bengal and the Maritime Continent and reduced(enhanced)in the South China Sea and the Western North Pacific region when the Qinghai-Xizang Plateau with more(less)snow cover.The convective activity related to BSISO2 is enhanced(reduced)in the northern Indian Ocean,Maritime Continent,the East China Sea,and the South China Sea region,and reduced(enhanced)in the Northwest Pacific.The snow cover over the plateau can affect the convective activity of BSISO1 by influencing the background field of Asian summer monsoon and humidity.When the plateau has more(less)snow in spring,the vertical northeast wind shear between 200 hPa and 850 hPa is enhanced(reduced)in the North Indian Ocean region,and the humidity gradient between the northern Indian Ocean and the Bay of Bengal increases(decreases),which is(not)in favor of the propagation of convective activities related with BSISO1 to the Bay of Bengal and Maritime Continent region.At the same time,the decrease of water vapor in the Maritime Continent region is not in favor of the propagation of convective activities related with BSISO1to the South China Sea and the Western North Pacific.