The western North Pacific subtropical high (WNPSH) is one of the deterministic predictors of the East Asian summer climate, and a better prediction of the WNPSH favors more reasonable forecast of the East Asian summer climate. This study focuses on seasonal prediction of the WNPSH during neutral summers without strong El Niño-Southern Oscillation (ENSO) forcing, and explores the associated predictable sources, using the one-month lead time retrospective forecasts from the Ensembles-Based Predictions of Climate Changes and Their Impacts (ENSEMBLES) project during 1960–2005. The results indicate that the ENSEMBLES atmosphere-ocean-land coupled models exhibit considerable prediction skill for the WNPSH during neutral summers, with successful reproduction of the WNPSH in the majority of neutral summers. The anomalous WNPSH in neutral summers, which corresponds to cyclonic/anticyclonic anomalies in the lower troposphere, is highly correlated with an east-west dipole local sea surface temperature (SST) distribution over the tropical WNP, suggesting an intimate local air-sea coupling. Further diagnosis of the local SST-rainfall relationship and surface heat flux indicates that the anomalous local SST plays an active role in modulating the variation of the WNPSH during neutral summers, rather than passively responding to the atmospheric change. The local SST anomalies and relevant air-sea coupling over the tropical WNP are reasonably well reproduced in the model predictions, and could act as primary predictable sources of the WNPSH in neutral summers. This could aid in forecasting of the East Asian rainband and associated disaster mitigation planning.

西北太平洋副热带高压（WNPSH）是东亚夏季气候的确定性预测因子之一，对WNPSH的更好预测有助于对东亚夏季气候进行更合理的预测。这项研究的重点是在没有强厄尔尼诺-南方涛动（ENSO）强迫的中性夏季WNPSH的季节预测，并使用基于整体的气候变化预测和气候变化预测的一个月提前期回顾性预测来探索相关的可预测来源。他们的影响（ENSEMBLES）项目在1960-2005年期间进行。结果表明，ENSEMBLES气-海-陆耦合模型在中性夏季对WNPSH表现出相当高的预测能力，并且在大多数中性夏季成功再现了WNPSH。在中性夏季，WNPSH异常，对应于低层对流层的气旋/反气旋异常，与热带WNP上的东西向偶极子局部海面温度（SST）分布高度相关，表明局部气海耦合密切。对局部SST-降雨关系和表面热通量的进一步诊断表明，异常的局部SST在中性夏季期间在调节WNPSH的变化中起着积极作用，而不是被动地响应大气变化。在模型预测中可以很好地再现热带WNP上的局部SST异常和相关的海海耦合，并且可以作为中性夏季WNPSH的主要可预测源。这可以帮助预测东亚雨带和相关的减灾计划。