资源环境科技发展态势分析平台

Although the middle-upper tropospheric land-sea thermal contrasts play very important roles in modifying global monsoon, the inter-decadal influences of the middle-upper tropospheric land-sea thermal contrasts in the Northern Hemisphere on the global monsoon have not investigated specifically. In this study, it is found that the summer middle-upper tropospheric zonal land-sea thermal contrast in the Eurasia-Pacific region changed from weak during the late 1980s and earlier and middle 1990s to strong after the late 1990s. This feature indicates a strengthened zonal land-sea thermal contrast during summer, which drives a stronger than normal Northern Hemisphere summer monsoon, with a hypothermal and wet climate over most of the subtropical East Asian and tropical African monsoon regions. In addition, the extensive anticyclonic circulation anomalies together with the less precipitation results in a warm and dry climate over the arid and semiarid regions to the west and north of the monsoon region, such as central Asia, Mongolia, and Northeast Asia. The inter-decadal change of the middle-upper tropospheric zonal thermal contrast is also closely associated with the warming trends of the extratropical North Pacific and North Atlantic during summer. However, this link possibly reflects a response of the warming oceans to the local atmospheric variability.