Anomaly-based synoptic analysis and model product application for 2020 summer southern China rainfall events.

Nine rainfall events affecting southern China in the 2020 summer were studied by a novel anomaly-based synoptic analysis approach, and the results were compared to those of standard synoptic analysis. These rainfall events occurred in the Dragon-boat rainy season and Meiyu rainy season from the Pearl River to the Yangtze and Huaihe rivers and did not entirely follow the climatic seasonal march of the summer monsoon. The first rainfall event occurred within the Dragon-boat rainy season and was associated with a broad rainfall area with scattered precipitation centers related to a broad convergence area of anomalous flows with scattered moist vorticity anomaly (MVA) centers located between two anomalous anticyclonic systems at 925 hPa. The other eight rainfall events appeared in the Meiyu rainy season and were generally associated with only a narrow convergence belt of anomalous flows and a positive MVA belt, sometimes with an anomalous cyclone moving eastward in the lower troposphere. The ECMWF model successfully predicted these anomalous convergence areas and MVA belts with lead times of 2–7 days. The advantages of this anomaly-based analysis approach include its ability to visually identify the location of a rainfall event, pinpoint possible meteorological causes and extend the model forecast length by the earlier detection of predictors. • Southern China summer rainfall events occurring in 2020 were studied based on the anomaly-based synoptic analysis approach. • Rain bands were associated with anomalous convergence bands and moist vorticity anomalies (MVA) in the lower troposphere. • The ECMWF model products can predict the anomalous convergence and MVA areas (or bands) with lead times of 5–7 days. [ABSTRACT FROM AUTHOR]