Analysis of the Characteristics and Causation of Severe Rainfall with Different Duration during the 2022"Dragon-boat Rain"in Guangdong

XIAO Liu-si; XU Huan; ZHANG Hua-long; TU Jing

doi:10.3969/j.issn.1007-6190.2023.06.004

Abstract：This work used the data of automatic weather stations on multiple time scales and ECMWF reanalysis to reveal the characteristics of the 2022"Dragon-boat Rain"in Guangdong and the causation of associated anomalous circulation.The results are shown as follows.The concentrated period of heavy rain was characterized by extended duration,high efficiency and extreme short-range rainrate.At the late stage of the process,the heavy rain intensified and covered wider areas,bringing short-range intense rainfall to the coast,the northern and central Pearl River Delta and the central part of northern Guangdong.The increased efficiency and duration of minute-wise rainfall amount resulted in the intensification of hourly rainrate.Fa-vorable background conditions were provided by the morphology of anomalous circulation patterns:At the up-per-and mid-latitudes,mid-level systems were more meridional than the climate mean to expose the northern part of south China to the effect of frequent westerly waves.In addition,a west Pacific subtropical high was more westward located and stronger than usual,relatively strong low-level southwesterly,southerly and east-erly airflow merged into the region of interest from the South China Sea and western North Pacific,making the transport of boundary-layer water vapor anomalously stronger.Water vapor was channeled directly into the northern part of Guangdong,causing persistent,intense rain to take place in the province(especially its northern part)by supplying steady converging/diverging and uplifting dynamics and water vapor.Besides,sustained injection of monsoonal flows kept forming unstable stratification to cause the heavy rain to appear repeatedly in contiguous raining areas.