Experimental 15-day-lead statistical forecast of intraseasonal summer monsoon rainfall over Eastern China

This study utilizes daily Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE) gridded rainfall and the U.S. National Centers for Environmental Prediction-Department of Energy reanalysis II products to examine the intraseasonal oscillations (ISOs) of rainfall over Eastern China during each summer of 1996, 2002, and 2006. These three cases represent three typical spatial patterns of intraseasonal rainfall anomalies over Eastern China, with the strongest intraseasonal rainfall occurring over the middle and lower Yangtze Basin, southern Yangtze Basin, and Southeast China, respectively. The intraseasonal rainfall anomalies over Eastern China are dominated by both 30-60- and 10-20-day ISOs in each summer and are further modulated by the boreal summer ISOs (BSISOs) over the entire Asian summer monsoon region. The objective of this study is thus to apply the Bayesian wavelet-banding (WB) scheme to predicting intraseasonal rainfall over Eastern China. Several key factors associated with BSISOs are selected as predictors to experimentally develop a 15-day-lead statistical forecast. The forecast results show promise for the intraseasonal rainfall anomalies over Eastern China. Correlations generally greater than or equal to 0.6 are noted between the observed and predicted ISOs of rainfall over the major intraseasonal activity centers during each of the three summers. Such a high forecasting skill on intraseasonal timescales over various areas in Eastern China demonstrates the general usefulness of the WB scheme.