资源环境科技发展态势分析平台

The Pacific Meridional Mode (PMM) is the leading air–sea coupled mode over the subtropical northeastern Pacific and plays an important role in ENSO occurrence. This study examined the performances of CMIP5/CMIP6 models in simulating the PMM and its association with ENSO. CMIP6 offers improvements in capturing the spatial structure and seasonality of PMM compared to CMIP5, but still considerably underestimates the air–sea coupling strength and coupling persistence time associated with the PMM. Additionally, large intermodel spread exists in the springtime PMM–wintertime ENSO relationship across the CMIP models, which is attributable to bias in the simulation of ITCZ. Models with a stronger climatological ITCZ provide favorable backgrounds for PMM-related sea surface temperature anomalies (SSTAs) to induce stronger atmospheric heating over the subtropical North Pacific. The enhanced air–sea coupling favors PMM-related SSTAs and atmospheric anomalies propagating southwestwards to the tropical central Pacific where they impact the following-winter ENSO.