Spatiotemporal features of nocturnal heavy rainfall over the central Yungui Plateau and its leading three-dimensional circulations patterns

Abstract

Based on hourly rain gauge data and ERA5 reanalysis, the spatiotemporal features of the nocturnal heavy rainfall over the Yungui Plateau (YGP) are characterized, and the associated three-dimensional circulation patterns are revealed. A local rainfall center is found on the windward slope of the central YGP, and the diurnal peak of heavy rainfall there is at midnight, which differs from heavy rainfall over most eastern China and is ~ 3 h earlier than that for the weak rainfall events. Composite analyses show that the atmospheric circulation pattern of the heavy rainfall days is characterized by an upper-level warm anomaly covering most of eastern China with a center at 300–400 hPa. Under hydrostatic and geostrophic equilibriums, the warm anomaly contributes to the generation of an anticyclonic (cyclonic) anomaly in the upper (lower) troposphere. As a result, the anomalous divergence in the upper level and the convergence of the cold northwesterly wind and warm wet southeasterly wind in the lower level induce heavy rainfall over the central YGP. A vertical temperature anomaly appears over the northwestern YGP in several days before the heavy regional rainfall event days and gradually moves southeastwards and strengthens. Blocked by the topography, the anomalies stop moving southward and gradually weaken after the heavy RREs end. The findings indicate how large-scale circulations and specific topography interact to influence the heavy RREs over the central YGP.