资源环境科技发展态势分析平台

This study advances the use of the Self-organizing Map (SOM) to identify the summer monsoon rainfall patterns over Southeast China (SEC), using 272 gauge records from May to August. Three distinct rain belts over the Huai River basin (HRB), the Lower Yangtze River basin (LYRB) and the South Coast region (SCR) are found. Their subseasonal variability strongly agrees with the northward progression of the East Asian Summer Monsoon (EASM) front in a stepwise fashion. We find that precipitation in the SCR and HRB rain belts exhibit significant changes in the mid-1990s, while the 1990s is the most active decade for the LYRB rain belt. Promising predictability of average daily rainfall over these three regions is obtained, with about 39% to 50% of the total variance explained by the circulation informed regression models. Both leave-one-year-out cross-validation and blind prediction verify the regression performance. The western North Pacific Subtropical High phases, mid-latitude blocking high anomaly over northeast China and upper-level divergence in SEC are found to best explain the variability of the rain belts. The newly proposed Russia-China wave patterns (western/central Russia -> north of Tibetan Plateau -> SEC) and teleconnection between the El Nino-Southern Oscillation and the rain belts also offer additional predictability. Findings from this work may advance the understanding of the EASM rain belts, and offer insights to the source of bias for numerical simulations of daily summer monsoon rainfall in the region.