The characteristics and evolution process of presummer intense regional rainfall over the Pearl River Delta metropolitan region

Abstract

The presummer intense regional rainfall events (RREs) over the Pearl River Delta (PRD) metropolitan region have been defined using rainy stations, maximum instantaneous regional rainfall coefficient (RRCt) and maximum rainfall intensity based on the rain gauge data from 2008 to 2017. Most of intense RREs with the maximum rainfall intensity about 20–60 mm·h−1 and the lifetime shorter than 24 h have the primary rainfall peak from noon to afternoon. Based on the rainfall pattern at 3 h prior to the events start, the intense RREs can be classified into two groups that one is southeastward propagation mode originating from the northwestern mountains of PRD and another is coastal mode from South China Sea (SCS). During the premonsoon‐onset period, the first type of RREs is the main mode causing the heavy rain in the cities of the inland region owing to the anomalous cold air from north confronting the wet and warm air from south with the increased southwesterly winds resulting in the strengthening frontal zone and moisture convergence. After the summer monsoon onset, the main rainfall pattern changes to the coastal mode having the significant impact on the coastal cities. The obvious anomalous cyclonic circulation related with the increased moisture convergence in the coastal regions providing the favourable conditions of the convection initiation and development. The study of the characteristics and evolution process of preceding intense RREs can improve the forecasting skills and reduce the risk of urban inundation.

The Principal Modes of Morning Extreme Precipitation over Inland Guangdong, China during Pre-Summer Rainy Season

“…The locally grown rainfall belt is located in the northern inland of GD. However, the southeastward-propagating rainfall system from the northwest weakens, which is consistent with previous studies [4,9] (Figure 4e). At 06 LST, the locally grown rainfall belt is further strengthened in terms of intensity and range over the eastern inland of GD with the enhanced southwesterly winds (Figure 4f).…”

“…This dataset was developed using the optimum interpolation technique, which combines the hourly rain gauge network data from the China Meteorological Administration (CMA) with satellite precipitation data obtained through the Climate Prediction Center Morphing Technique (CMORPH) from the U.S. National Oceanic and Atmospheric Administration (NOAA) [28,29]. This dataset has been widely used to investigate the characteristics of precipitation in South China [4,30,31]. The latest hourly fifth generation of the reanalysis data (ERA5) with a resolution of 0.25 • is also utilized to examine the corresponding atmospheric conditions from the European Centre for Medium-Range Weather Forecasts (ECMWF) [32].…”

“…However, in this study, a statistical method similar to S-EOF is used to explore the principal modes of MEP with a time-varying pattern during the pre-and post-monsoon onset periods. This method has been demonstrated to perform the main modes of intense regional rainfall well over the Pearl River Delta [4]. The best track data for tropical cyclones from CMA are used to exclude typhoon precipitation [36].…”

“…Guangdong (GD) province, located in South China with the north of the South China Sea (SCS) and the south of the Nanling mountains, is known as one of the main rainfall centers, particularly in the pre-summer rainy season (April-June) when extreme precipitation occurs frequently [1][2][3][4]. The extreme precipitation in GD is associated with complex terrains, the SCS summer monsoon, and synoptic disturbances.…”