干旱区生态环境知识资源中心

This study analyzed the spatial differences of the precipitation variations in the mid-latitude Asia and their possible physical mechanisms during 1960-2009. The annual precipitation showed an opposite variations between the westerlies-dominated arid Central Asia (ACA) and monsoon-dominated North China (NC) during the study period. Given the different contributions of seasonal precipitation to annual total precipitation in ACA and NC, the atmospheric circulation anomalies during the major precipitation seasons (winter in ACA/summer in NC) were analyzed. In winter, negative North Atlantic Oscillation may cause negative height anomalies over the north side and positive anomalies over the south side of the ACA. Together, the enhanced pressure gradient and anomalous westerly wind brings more water vapor to ACA, and leaves less precipitation in NC. In summer, the low-pressure anomalies in Northeast China, along with a weaker summer monsoon and negative height anomalies in Eastern Europe together contribute to reduced (excessive) summer precipitation in NC (ACA). The interactions between ENSO and NAO may result in the opposite precipitation variations between ACA and NC. A significant 2-3-year cycle is identified in ACA, which is linked to the variations of westerly circulation in the middle troposphere.