ABSTRACT:

Using a weakly coupled data assimilation (WCDA) system to constrain the soil moisture and soil temperature in a coupled climate model with a global land data assimilation product, this study demonstrates significant improvements in simulating the interannual variations of EASM rainfall, capturing the notable shift to a "wetter-South-drier-North" rainfall pattern in China in the early 1990s.
Improvements in predicting the EASM rainfall are attributed to the strong land-atmosphere coupling in large areas over China, which allows improved predictions of soil moisture to influence precipitation through soil moisture-precipitation feedback, and the effects of land anomalies on the EASM circulation. This study highlights the significant contribution of land to the interannual predictability of EASM rainfall, with a great potential to advance skillful interannual predictions of benefit to the large populations influenced by the annual whiplash of the summer monsoon rain.