An objective approach to predict the spatial property of anomalous rain-belt of Meiyu

Abstract

The Meiyu 2020 with record-breaking amount of precipitation, widespread area coverage and anomalous northern location brought about great social and economic impacts in China. However, the spatial property of anomalous rain-belt for such a catastrophic Meiyu is not well predicted. In this study, high-resolution in-situ observation and reanalysis data are used to explore key signals and possible prediction method. Results show that anomalous rain-belt of Meiyu 2020 is mainly influenced by the westward extended western North Pacific subtropical high (WNPSH) in the low-latitude and enhanced meridional circulation in mid-high latitudes. However, the distribution of composite anomalous circulation, especially in the mid-high latitude, cannot be revealed for 2020 if only considering the influence from the tropical Indo-Pacific thermal conditions. Through additional consideration of North Atlantic Oscillation (NAO), which has great contribution to circulation in the Northern Hemisphere mid-high latitudes, the anomalous key circulation features in 2020 can be appropriately captured. Also, the spatial property of anomalous rain-belt like 2020 could be accurately simulated by the established prediction model including combined effects of tropical Indo-Pacific thermal conditions and NAO. Specifically, quantified analyses prove that the warmed Indian Ocean plays a dominant role and anomalous NAO also has great importance for record-breaking area coverage and anomalous northern location of Meiyu 2020. Thus, for a more accurate prediction for anomalous rain-belt such as Meiyu 2020, the combined effects of both low- and mid-high-latitudes should be comprehensively considered.

Keywords

• Meiyu
• Rain-belt
• Spatial property
• Prediction