Recent Changes in Heavy Precipitation Events in Northern Central China and Associated Atmospheric Circulation

摘要

Northern Central China (NC China) is a seriously arid region. Precipitation variations are vital for environmental protection and socio-economical development. This study investigates the recent changes in summer heavy precipitation (HP) events over NC China and associated atmospheric circulation anomalies. Compared with the period of 1986-2002, the HP amount and frequency both significantly increase during 2003-2016, contributing to the shift to increase in total summer precipitation amount. After the early 2000s, the Northwest Pacific subtropical high becomes intensified and shifts westward and northward, leading to significant moisture convergence anomalies over NC China and divergence anomalies over Northwest Pacific. Therefore, the net moisture budget dramatically increases since the early 2000s. Further results show that the strengthened net moisture influx across the southern boundary contributes dominantly to the increased net moisture budget, especially at the lower level. Despite a relatively small magnitude, the intensified westerly current across western boundary makes a dominant contribution at middle and upper layers. Additionally, the strengthened westerly and easterly anomalies occupy northern and southern China, respectively, along with the eastward expansion of westerly jet stream region. Thus, the lower-level convergence and upper-level divergence both intensify, and further trigger enhanced ascending movement. These conditions jointly contribute to the inter-decadal change in HP events over NC China after the early 2000s.