Contribution of Changes in Synoptic‐Scale Circulation Patterns to the Past Summer Precipitation Regime Shift in Eastern China

Abstract

AbstractDuring the past few decades, eastern China has experienced a summer precipitation regime shift characterized by a “southern flood‐northern drought” pattern. Among numerous studies explaining this phenomenon, few have quantified dynamic‐thermodynamic contributions at daily‐synoptic scales. Using a self‐organizing map approach, summertime daily atmospheric flows during 1961–2015 are clustered into 20 circulation patterns (CPs), each of which is assigned to an attribute among wet, dry, and neutral according to their synchronous precipitation anomalies. We find that decreases in wet CPs for the north and increases (decreases) in wet (dry) CPs for the south are robustly significant and can well explain the contrasting precipitation trends. Dynamic and thermodynamic processes jointly produce more precipitation in the south but less precipitation in the northern half of the north region, with thermodynamic contributions being 30–40% larger. Dynamic influence and its interaction with thermodynamic factors dictate the latitudinal boundary between the drying and wetting regions.