Dynamics of Interannual Variability in Summer Precipitation over East Asia

The summertime mei-yu-baiu rainband over East Asia displays considerable interannual variability. A singular value decomposition (SVD) analysis for interannual variability reveals that precipitation anomalies over the mei-yu-baiu region are accompanied by in situ anomalies of midtropospheric horizontal temperature advection. Anomalous warm (cool) advection causes increased (decreased) rnei-yu-baiu precipitation locally by inducing adiabatic ascent (descent). The anomalous precipitation acts to reinforce the vertical motion, forming a feedback system. By this mechanism, the remotely forced anomalous atmospheric circulation can induce changes in mei-yu-baiu precipitation. The quasi-stationary precipitation anomalies induced by this mechanism are partially offset by transient eddies. The SVD analysis also reveals the association of mei-yu-baiu precipitation anomalies with several teleconnection patterns, suggesting remote induction mechanisms. The Pacific-Japan (PJ) teleconnection pattern, which is associated with anomalous convection over the tropical western North Pacific, contributes to mei-yu-baiu precipitation variability throughout the boreal summer. The PJ pattern mediates influences of the El Nino-Southern Oscillation in preceding boreal winter on mei-yu-baiu precipitation. In early summer, the leading covariability pattern between precipitation and temperature advection also features the Silk Road pattern-a wave train along the summertime Asian jet-and another wave train pattern to the north along the polar-front jet that often leads to the development of the surface Okhotsk high.