The characteristics of regional heavy precipitation events over eastern monsoon China during 1960-2013

摘要

Regional heavy precipitation events (RHPEs), with their high intensity, large impact area and long duration, have tremendous impacts on society and ecosystems. Using a daily precipitation dataset of 470 climate stations over the monsoon region in eastern China, we developed an automated technique to identify RHPEs. In total, 2608 RHPEs are identified over the period 1960–2013. All events are classified into three categories: Grade 1, 2 and 3 from least to most severe RHPEs, based on an integrated index. Spatially, these events, particularly the most severe ones (Grade 3), are mainly located in the middle and lower Yangtze River basin and southeastern China (SE). RHPEs that occur in the temperate monsoon zone of northeast (NE) are mainly Grade 2 and Grade 1 events. Trend analysis shows that frequency and integrated intensity of all RHPEs have increased during 1960–2013 for eastern China. This means RHPEs are becoming more severe and frequent. However, increase occurs mostly with the Grade 3 and Grade 2 events, while the Grade 1 events generally show a decreasing trend. Distinctive regional patterns also exist. Over the entire study period, RHPEs become more frequent and severe in the tropical and subtropical monsoon zones (SE), whereas the temperate monsoon zone (NE) experiences a decrease in their integrated intensity and frequency. However, this spatial pattern shifts to decrease in SE and increase in NE since 2000. Such shift is likely linked to the inter-decadal variations of East Asian Summer Monsoon, western Pacific subtropical high and Pacific decadal oscillation. In general, multiday events are becoming more severe, whereas little change has occurred with single-day events. The observed increase in severity of Grade 3 and multiday RHPEs could significantly increase the risk of flooding over eastern China.