التفاصيل البيبلوغرافية
| العنوان: |
Inter‐Basin Versus Intra‐Basin Sea Surface Temperature Forcing of the Western North Pacific Subtropical High's Westward Extensions. |
| المؤلفون: |
Jones, Jhordanne J., Chavas, Daniel R., Johnson, Zachary F. |
| المصدر: |
Journal of Geophysical Research. Atmospheres; 8/16/2024, Vol. 129 Issue 15, p1-15, 15p |
| مصطلحات موضوعية: |
CLIMATE change models, OCEAN temperature, RAINFALL, LA Nina, LANDFALL, TROPICAL cyclones |
| مستخلص: |
Zonal extensions of the Western Pacific subtropical high (WPSH) strongly modulate extreme rainfall activity and tropical cyclone (TC) landfall over the Western North Pacific (WNP) region. These zonal extensions are primarily forced on seasonal timescales by inter‐basin zonal sea surface temperature (SST) gradients. However, despite the presence of large‐scale zonal SST gradients, the WPSH response to SSTs varies from year to year. In this study, we force the atmosphere‐only NCAR Community Earth System Model version 2 simulations with two real‐world SST patterns, both featuring the large‐scale zonal SST gradient characteristic of decaying El Niño‐developing La Niña summers. For each of these patterns, we performed four experimental sets that tested the relative contributions of the tropical Indian Ocean, Pacific, and Atlantic basin SSTs to simulated westward extensions over the WNP during June–August. Our results indicate that the subtle differences between the two SST anomaly patterns belie two different mechanisms forcing the WPSH's westward extensions. In one SST anomaly pattern, extratropical North Pacific SST forcing suppresses the tropical Pacific zonal SST gradient forcing, resulting in tropical Atlantic and Indian Ocean SSTs being the dominant driver. The second SST anomaly pattern drives a similar westward extension as the first pattern, but the underlying SST gradient driving the WPSH points to intra‐basin forcing mechanisms originating in the Pacific. The results of this study have implications for understanding and predicting the impact of the WPSH's zonal variability on tropical cyclones and extreme rainfall over the WNP. Plain Language Summary: Westward extensions of the Western North Pacific subtropical high (WPSH) drive rainfall extremes over the Western North Pacific basin, and is important for the prediction of summer rainfall, including monsoonal rainfall and tropical cyclone activity. Studies have previously highlighted the importance of tropical large‐scale zonal sea surface temperature (SST) gradient—warm tropical Indian Ocean in conjunction with cold equatorial eastern Pacific Ocean—in developing and maintaining the summer WPSH and westward extensions. Here, we further show that even with very similar SST patterns, the large‐scale zonal SST pattern may belie forcing from inter‐basin SSTs versus intra‐basin SSTs. We find that the net influence from the Pacific basin determines whether inter‐basin remote SST gradients versus intra‐basin Pacific SST gradients are the predominant driver of westward extensions. Key Points: Two similar SST patterns belie two different mechanisms forcing the subtropical high's westward extensionsTropical Pacific SST gradient forcing of westward extensions can be suppressed by its extratropical SST forcingRemote Atlantic SST forcing drives westward extensions when the local net Pacific forcing is weak [ABSTRACT FROM AUTHOR] |
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