Two distinct evolutions of extreme precipitation over central eastern China during June and July

Previous studies have documented the occurrence of extreme precipitation in fixed regions and the associated atmospheric circulation patterns. Present study reveals that extreme precipitation over central eastern China can be stationary, move northward and southward during June and July and investigates atmospheric circulation patterns leading to distinct southward and northward movement of extreme precipitation. It is found that the distinct movement of extreme precipitation follows closely the movement of lower-level convergent winds and mid-level ascending motion. Further analysis shows that the two types of evolutions of extreme precipitation are results of a combined effect of the mid-latitude East Asian trough/ridge, the western North Pacific subtropical high and the South Asian high. When the mid-latitude atmospheric circulation displays a large zonal variation with a deep trough over East Asia, the lower-level wind convergence moves southward, leading to southward move of extreme precipitation region over central eastern China. When the mid-latitude atmospheric circulation is dominantly zonal over East Asia and the western North Pacific subtropical high extends westward and the South Asian high extends eastward, the lower-level wind convergence moves northward, followed by northward moving extreme precipitation region. The present result has implication for forecasting the movement of extreme precipitation over central eastern China.