Multiscale analysis of a record-breaking heavy rainfall event in Guangdong, China

Abstract

Abstract An extremely heavy rainfall event hit eastern Guangdong province, China on 30 August 2018, during which Gaotan station observed a record-breaking 1056.7 mm of precipitation in a 24-h period. Using analysis data, observations from soundings, automatic weather stations and radar, as well as a Lagrangian model, the multiscale characteristics of this record-breaking rainfall event are investigated, including large-scale forcing, moisture transport, mesoscale circulations, and microphysical features. The monsoon depression near the Indo-China Peninsula and the Beibu Gulf played an important role in sustaining the moisture supply from main source regions of the Arabian Sea, the Bay of Bengal and the South China Sea. The low-level winds turned from southwesterly to southerly-southeasterly, favoring back-building processes mainly due to orographic lifting by the southwest-northeast oriented Mt. Lianhua. The repeated formation and maintenance of rainbands along Mt. Lianhua, which were attributable to the back-building processes, local convergence near Gaotan, and the high terrain to the northeast of Gaotan, accounted for the extremely heavy rainfall over Gaotan. Graupel dominated above the freezing level over Gaotan during the period of intense precipitation, suggesting that riming and melting processes were vital contributors to the surface heavy rainfall.