Details

Autor(en) / Beteiligte

• Wang, Li‐Chiao
• Lin, Yu‐Shen

Titel

A Potential Reason for a More CP El Nino‐Like SSTA Performance in CMIP6 Simulations

Ist Teil von

• Geophysical research letters, 2023-12, Vol.50 (23), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2023

Quelle

Wiley Online Library Journals Frontfile Complete

Beschreibungen/Notizen

• A systematic bias of the extremely westward zonal current (EWZC) was revealed over the equatorial Pacific in Coupled Model Intercomparison Project 6 (CMIP6) models. It tends to weaken the modeled interannual variability of equatorial zonal current anomaly (ZCA) with its maximum variability concentrated in the western Pacific. A mixed‐layer heat budget analysis demonstrates that the simulation of mean circulation effect is slightly affected by the zonal current bias. However, the zonal advective feedback is closely linked to the biased equatorial ZCA variability and is overestimated (underestimated) in the Niño‐4 (Niño‐3) region. The magnitude of zonal advective feedback is even greater than that of thermocline feedback and becomes the most dominant process contributing to the growth of mixed‐layer temperature anomaly tendency in the Niño‐4 region. Such a bias is essential for a more central‐Pacific El Niño‐like performance in CMIP6 models. Plain Language Summary El Niño is a significant climate variability characterized by a strong seasonal‐locking pattern in the tropical Pacific. It can be roughly classified into eastern‐Pacific and central‐Pacific El Niño, where the maximum warm sea surface anomaly (SSTA) takes place in the equatorial eastern and central Pacific, respectively. Previous studies have utilized a series of coupled models to investigate the dynamics of El Niño diversity. Here, we discovered a serious error in the state‐of‐the‐art CMIP6 models in reproducing equatorial Pacific zonal flows. Through a mixed‐layer heat budget analysis, the overestimated zonal advective feedback was revealed to be predominantly attributed to the zonal current bias, leading to an excessive warm El Niño SSTA toward the maritime continent. A higher proportion of central‐Pacific El Niño pattern was captured when contrasting the two types of El Niño in CMIP6 simulations. Key Points A systematic bias of extremely westward zonal current anomaly field was revealed over the equatorial Pacific in CMIP6 models The bias in the equatorial Pacific zonal current field deeply influences the simulation of zonal advective feedback Excessive zonal advective feedback is one of the key factors to result in a more central‐Pacific El Niño‐like pattern in CMIP6 models