Interdecadal Variability of Summer Extreme Rainfall Events over the Huaihe River Basin and Associated Atmospheric Circulation

The Huaihe River basin (HRB) is an important economically developed and grain production region in China, which is severely affected by rainfall anomalies, especially extreme rainfall events (EREs). It is crucial to the features of interdecadal change in EREs and the contribution of EREs to summer-mean total rainfall amount (TRA) over the HRB. Using the observational 24-h ac-cumulated rainfall and the reanalysis products from the European Center for Medium-Range Weather Forecast (ECMWF), as well as the methods of composite analysis and Mann-Kendal and running t tests, we revealed that the EREs experienced a significant interdecadal increase from the period 1990-1999 to the period 2000-2009. The EREs, particularly long persistent extreme rainfall events (LPEREs), occurred more frequently over the HRB during the latter period and dominated the interdecadal increase in the summer mean TRA. An anomalous high-pressure ridge and associated anomalous anticyclone appeared around Lake Baikal during the latter period, which led to anomalous northeasterlies along the eastern flank of the anomalous anticyclone, inducing the southward intrusion of cold air flow from higher latitudes and associated anomalous ascent and more active convection over the HRB. As such, more EREs and LPEREs occurred during the latter period. The higher pseudo-equivalent temperatures also support more active convective ascent and relevant more EREs. The results may shed light on further understanding the effect of large-scale atmospheric circulation on the interdecadal variability of EREs over the HRB, helping mitigate the disastrous impacts of EREs on local ecosystems, agriculture, soil erosion, and societies.

Automated summary

The Huaihe River basin in China is a economically developed region that is heavily impacted by rainfall anomalies, especially extreme rainfall events (EREs). This study examines the interdecadal changes in EREs and their contribution to the total summer rainfall in the region. The results show that the frequency of EREs, particularly long persistent extreme rainfall events (LPEREs), has significantly increased in recent decades, leading to a higher total summer rainfall. The study also identifies the atmospheric circulation patterns that contribute to the increase in EREs. Understanding these patterns can help mitigate the negative impacts of EREs on local ecosystems, agriculture, soil erosion, and societies.