Influence of the Pacific–Japan Pattern on Indian Summer Monsoon Rainfall

AbstractThis study discusses the impact of the Pacific-Japan (PJ) pattern on Indian summer monsoon (ISM) rainfall and its possible physical linkages through coupled and uncoupled pathways. Empirical orthogonal function analysis of 850 hPa relative vorticity over the western North Pacific (WNP) is used to extract the PJ pattern as the leading mode of circulation variability. The partial correlation analysis of the leading principal component reveals that the positive PJ pattern, which features anticyclonic and cyclonic low-level circulation anomalies over the tropical WNP and around Japan respectively, enhances the rainfall over the southern and northern parts of India. The northwestward propagating Rossby waves, in response to intensified convection over the Maritime Continent and reinforced by low level convergence in the southern flank of westward extended tropical WNP anticyclone, increase rainfall over the southern peninsular India. Meanwhile, the anomalous moisture transport from the warm Bay of Beng...