Abstract
The prediction skills of climate model simulations in the western tropical Pacific (WTP) and East Asian region are assessed using the retrospective forecasts of seven state-of-the-art coupled models and their multi-model ensemble (MME) for boreal summers (June–August) during the period 1983–2005, along with corresponding observed and reanalyzed data. The prediction of summer rainfall anomalies in East Asia is difficult, while the WTP has a strong correlation between model prediction and observation. We focus on developing a new approach to further enhance the seasonal prediction skill for summer rainfall in East Asia and investigate the influence of convective activity in the WTP on East Asian summer rainfall. By analyzing the characteristics of the WTP convection, two distinct patterns associated with El Niño-Southern Oscillation developing and decaying modes are identified. Based on the multiple linear regression method, the East Asia Rainfall Index (EARI) is developed by using the interannual variability of the normalized Maritime continent-WTP Indices (MPIs), as potentially useful predictors for rainfall prediction over East Asia, obtained from the above two main patterns. For East Asian summer rainfall, the EARI has superior performance to the East Asia summer monsoon index or each MPI. Therefore, the regressed rainfall from EARI also shows a strong relationship with the observed East Asian summer rainfall pattern. In addition, we evaluate the prediction skill of the East Asia reconstructed rainfall obtained by hybrid dynamical–statistical approach using the cross-validated EARI from the individual models and their MME. The results show that the rainfalls reconstructed from simulations capture the general features of observed precipitation in East Asia quite well. This study convincingly demonstrates that rainfall prediction skill is considerably improved by using a hybrid dynamical–statistical approach compared to the dynamical forecast alone.
Highlights
As one of the major monsoon climate regions in the world, East Asia suffers frequently from severe floods and/or droughts in summer
Many researchers have studied the characteristics of the East Asian summer monsoon (EASM), including the large-scale circulation related to the rainband (Huang and Sun 1992; Huang 2004; Gong et al 2011; Lee et al 2013a)
The present study investigates the limitations and possibilities for seasonal climate prediction, with a particular focus on summer rainfall anomalies in the western tropical Pacific (WTP) and East Asian region, using available hindcast datasets for the 23-year period of 1983–2005 obtained from the operational climate forecast models in the Asia Pacific Economic Cooperation (APEC) Climate Center (APCC)
Summary
As one of the major monsoon climate regions in the world, East Asia suffers frequently from severe floods and/or droughts in summer. The present study investigates the limitations and possibilities for seasonal climate prediction, with a particular focus on summer rainfall anomalies in the WTP and East Asian region, using available hindcast datasets for the 23-year period of 1983–2005 obtained from the operational climate forecast models in the Asia Pacific Economic Cooperation (APEC) Climate Center (APCC). Further issues that are addressed in this study include: (1) an assessment of the predictive quality of the climate model simulations for the East Asian summer rainfall and WTP convection, (2) investigation of the possible methods to improve the predictability of the East Asian monsoon rainfall using predictable information and (3) an evaluation of the prediction skill for the reconstructed summer rainfall over the East Asian region by applying the developed approach method.
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