Impact of the Asian–Pacific Oscillation on early autumn precipitation over Southeast China: CMIP6 evaluation and projection

Abstract

This study evaluated the capability of 32 models of phase 6 of the Coupled Model Intercomparison Project in modeling the influence of the preceding August Asian–Pacific Oscillation (APO) on subsequent early autumn (September) precipitation over Southeast China and associated atmospheric anomalies, as well as its future projection during 2021–2040 (near-term), 2041–2060 (mid-term), and 2081–2100 (long-term) under different Shared Socioeconomic Pathways (SSPs: SSP2-4.5 and SSP5-8.5). Results indicated that two-thirds of the individual models yielded positive correlations between the APO and Southeast China precipitation that conformed to the observations. On the basis of the capability to reproduce the significantly positive relationship between the APO and Southeast China precipitation, three models were chosen as the “best” model ensemble (BMME). The BMME effectively simulated both the APO-associated precipitation and the atmospheric anomalies, and outperformed the ensemble of the remaining 29 models in terms of the positive correlation between the APO and Southeast China precipitation, and the negative correlations between the meridional displacement of the East Asian jet (EAJ) and the APO and Southeast China precipitation. In general, during three future time periods under both SSPs, the BMME projected persistent negative correlations between the APO and EAJ, and the APO–Southeast China precipitation and EAJ–Southeast China precipitation relationships were projected to weaken. However, considerable discrepancies were evident among the changes projected by the individual models; only the projected changes in the APO–EAJ relationship showed good model agreement.摘要本文对32个CMIP6模式对8月亚洲–太平洋涛动 (APO) 与我国东南初秋 (9月) 降水及大气环流联系的模拟能力进行了评估, 并就SSP2-4.5和SSP5-8.5情景下, 未来2021–2040年 (近期) , 2041–2060 (中期) 和2081–2100 (长期) 期间二者联系的变化进行了预估. 基于模式对APO与我国东南初秋降水之间显著正相关关系的再现能力, 选取3个模式作为“最优”模式集合 (BMME) . 研究表明, BMME较好地模拟了与APO相关的我国东南初秋降水和大气环流异常, 且在再现APO与我国东南部降水的正相关关系, 以及东亚高空急流 (EAJ) 经向位移与APO和我国东南部初秋降水之间的负相关关系方面均优于单个模式. 总体而言, 未来不同SSP情景下尽管APO与EAJ之间仍呈负相关关系, 但APO与我国东南初秋降水以及EAJ与我国东南降水的关系将呈减弱确实. 此外, 不同模式预估结果之间存在明显差异, 仅对未来APO-EAJ关系的预估表现出较好的一致性.