The water vapor transport associated with the 30-50 day oscillation over the Asian monsoon regions during 1979 summer

We apply the empirical orthogonal function (EOF) analysis to the potential and stream-function of the vertically integrated water vapor transport over a region (25°S-60°N, 40°E-130°W). It is found that the water vapor transports over the Indian and East Asian monsoon regions are related to each other through their interactions with the eastward propagating 30-50 day oscillation. Several occurences follow the 30-50 day oscillation of the Indian monsoon westerlies in a coherent manner. This study reveals that north-south movement is caused by the eastward propagation of the 30-50 day mode. We also apply the EOF analysis to the global potential of the water vapor transport between 45°S and 45°N over the entire FGGE year. It is inferred from the time lag between onsets of the Indian and East Asian monsoon that the two monsoons may be induced by the interaction between the annual cycle and the 30-50 day low-frequency mode. -from Authors