Summer Regional Pentad Extreme Precipitation in Eastern China and Their Possible Causes

Persistent extreme precipitation covering a large area usually causes severe flooding disasters in China, but how to depict it and what are the possible still open questions. With Climate Prediction Center global unified gauge-based analysis of daily NCEP/NCAR reanalysis dataset from 1979 2019, summer regional pentad (RPEP) is defined according threshold 95th percentile with more than 5% land grids coverage eastern China. While definition RPEP highlights climate features both persistence regionality precipitation, distinctly different previous definitions that mainly reflect synoptic aspects data have strictly temporal-spatial constraints. Four categories RPEPs objectively identified by K-means cluster analysis, i.e., South China (SC), Yangtze River (SYR), Jianghuai (JHR), North (NC). Along (SYR JHR), intensity positively correlated each other, increase intensity, its center gravity tends move eastward all four regions southward respectively, vice versa. The mostly persist for one can reach up two three pentads at most, along duration RPEP, enhanced accordingly. Furthermore, frequency increased significantly since late 1990s SYR, JHR, SC. Associated strong pentad-mean convergence ascending motion occur middle-lower troposphere, except SC dominated local low-pressure cyclone anomalies, other forced western Pacific subtropical high southeast weak trough north, low-level anticyclone anomaly transports abundant water vapors Besides, closely accordance obvious subseasonal oscillations, especially 10–30-day 30–60-day which be regarded as potential sources predictability