Highly improved predictive skill in the forecasting of the East Asian summer monsoon

The East Asian summer monsoon greatly influences the lives and property of about a quarter of the people in the world. However, the predictive skill of the monsoon is very low in comparison with that of the Indian summer monsoon because of the complexity of the system which involves both tropical and subtropical climates. Previous monsoon prediction models emphasized ocean factors as the primary monsoon forcing. Here we show that preseason land surface cover is at least as important as ocean indices. New statistical forecast models of the East Asian summer monsoon using land cover conditions in addition to ocean heat sources double and triple, respectively, the predictive skill of the northern and southern East Asian summer monsoon forecasting models relative to models using ocean factors alone. This work highlights the, as yet, undocumented importance of seasonal land cover in monsoon prediction and the role of the biosphere in the climate system as a whole. We also detail the physical mechanisms involved in these land surface forcings.