In the upper troposphere , there is no intact asian active center . the troposphere structure of summertime ao is implicated with the horizontal heterogeneity of air temperature throughout the whole troposphere with its center over asian continent , which results in the zonal asymmetry and baroclinic structure of the summertime ao ( especially its asian center ) . on the contrary , the correlation between wintertime ao and sea - land thermal contrast confines in the lower troposphere , hence its zonal asymmetry and baroclinity in the lower level 夏季北极涛动的这种结构与对流层整层的温度水平分布不均匀性有密切联系，且这种温度分布差异主要体现在亚洲大陆，因而也就使北极涛动的中纬度亚洲中心呈现出比同纬度带其它区域更为明显的纬向非对称性和斜压性；而冬季北极涛动受下垫面海陆分布差异影响，其纬向非对称型和斜压性质主要出现在对流层中低层，在对流层高层表现出很强的环形模态和正压结构。
