高原季风的分布特征及其指数对比分析

Distribution Characteristics of Plateau Monsoon and a Contrastive Analysis of Plateau Monsoon Index

利用NCEP/NCAR再分析资料,在P、Z和σ三种坐标系中对青藏高原地区冬、夏季各环流场要素进行了分析,得到了高原季风的主要分布区域,并得出对流层高原季风的主要特征体现在由散度场表征的风场辐散、辐合上。同时,利用高原主体中心的散度区域平均值定义了一个新的高原季风指数Div-PMI。对比分析新、旧几种高原季风指数的计算方法、物理意义、年变化及年际变化,表明DivPMI指数计算方法简单,且能较好地解释高原季风的产生机理,在反映高原季风的季节演变特征上也具有一定的优势。通过各种高原季风指数与1、4、7、10月中国降水的相关性分析表明,Div-PMI指数与高原地区降水呈一致负相关,且相关最为显著。

Based on NCEP/NCAR monthly reanalysis data,the elements of the circulation field over the Qinghai-Xizang Plateau in winter and summer in P,Z and σ coordinate systems were analyzed,got the main distribution field of plateau monsoon,and drew a conclusion that the divergence field can most effectively reflect plateau monsoon's characteristics in the troposphere.Based on regional average of divergence field in the center of plateau main body,a new plateau monsoon index Div-PMI was defined.By contrasting the Div-PMI versus 4kinds of plateau monsoon index on computing method,physical significance,seasonal and interannual variation,it was found that Div-PMI has a simple calculation method,can also reflect plateau monsoon's production mechanism preferably.Besides,it has a preponderance on reflecting the characteristics of the plateau monsoon' s seasonal variation.A correlation analysis was made between monsoon index and the monthly precipitation of January,April,July and October in China,it was discovered that Div-PMI has a negative correlation with plateau area precipitation and the correlation is most remarkable in all indexes.