Interdecadal Variation of the Relationship between East Asian Water Vapor Transport and Tropical Pacific Sea Surface Temperatures during January and Associated Mechanisms

This study examined the interdecadal variations in the relationship between the East Asian water vapor transport (WVT) and the central and eastern tropical Pacific (CETP) sea surface temperatures (SSTs) in January during 1951-2018, focusing on the meridional WVT over East Asia, which is critical for the East Asian winter precipitation. The results indicate that before the 1980s, an increased southerly WVT over East Asia was generally associated with warm SST anomalies in the CETP during January, whereas, after the mid-1980s, an increased southerly WVT over East Asia was mostly associated with cold SST anomalies in the central tropical Pacific during January. The underlying mechanisms are discussed based on a comparison on the climate anomalies associated with the East Asian meridional WVT between the periods of 1951-79 and 1986-2018. During 1951-79, the meridional WVT over East Asia was mainly modulated by the Pacific-East Asian (PEA) teleconnection, which would induce an anomalous southerly WVT over East Asia corresponding to warm SST anomalies in the CETP. Whereas, during 1986-2018, the connection between the PEA teleconnection and the East Asian meridional WVT was weakened. The connection among the CETP SSTs, the anomalous zonal circulation over the North Pacific, and the East Asian meridional WVT was enhanced. Additionally, the connection among the CETP SSTs, the circumglobal teleconnection in the Northern Hemisphere, and the East Asian meridional WVT was enhanced. The above two enhanced connections opposed the effect of the PEA teleconnection and would induce an anomalous southerly WVT over East Asia corresponding to cold SST anomalies in the central tropical Pacific.