Characteristics of Two General Circulation Patterns During Floods over the Changjiang-Huaihe River Valley

Characteristics of the atmospheric general circulation during the catastrophic floods over the Changjiang-Huaihe River Valley (CHRV) are investigated. There are two precipitation patterns over China in the CHRV flood years: the CHRV flood-whole country-wet (P1) pattern and the CHRV flood-south (north) side-dry (P2) pattern . The circulation analysis results show that there are obvious differences between the NH 500-hPa geopotential height fields of P1 and P2 precipitation patterns. The establishment of East Asia-Atlantic (EAA) correlation chain (the South China Sea (SCS) high-the Meiyu trough-the Okhotsk Sea high over East Asia) is a critical condition for excessive summer precipitation over the CHRV, while the European blocking high plays an important role in determining the precipitation pattern over China in the CHRV flood years. Besides, the relation between the EAA correlation chain and the sea surface temperature anomaly(SSTA) in the North Pacific is also studied.