Inter-decadal transition of the leading mode of inter-annual variability of summer rainfall in East China and its associated atmospheric water vapor transport

This study investigated the inter-decadal variations of the leading empirical orthogonal function mode of the inter-annual variability of summer precipitation in East China from 1951 to 2012. From the 1950s to the 1980s, the main rain belt in the positive-phase years was centered along the middle and lower Yangtze River Valleys, with negative rainfall anomalies in South China and North China. Since the 1990s, the main rain belt of the positive-phase years has been shifted northward. During the period 2001–2012, the center of the main rain belt in the positive-phase years has shifted to the regions between the Yangtze and Yellow Rivers. This shift could be attributed to the inter-decadal variations of the anomalous atmospheric water vapor transport (AWVT) associated with the leading mode, which changed from a previously “anticyclone–cyclone” dipole structure to an anticyclonic monopole structure. The underlying physical mechanisms concerning the exertions from sea surface temperatures (SSTs) have also been preliminarily explored. The results indicate that the significant inter-decadal transition in the leading mode of summer precipitation in East China and the causative anomalous AWVT from 2001 to 2012 may be related to an inter-decadal change of inter-annual variability of the tropical SSTs in both the Indian and Pacific Oceans, which has been below normal from 2001 to 2012. Therefore, the influence of the tropical SSTs on the inter-annual variability of the East Asian climate may be diminished from 2001 to 2012, whereby a strongly coupled “anticyclone–cyclone” dipole-structured anomalous AWVT cannot be induced.