| Autor: |
Shao, Mingming1 (AUTHOR) umshao@gmail.com, Wu, Lichuan2 (AUTHOR) |
| Předmět: |
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| Zdroj: |
Journal of Geophysical Research. Atmospheres. Apr2024, Vol. 129 Issue 8, p1-19. 19p. |
| Abstrakt: |
Surface wind divergence is largely modulated by the sea surface temperature (SST) gradient through vertical momentum mixing and pressure adjustment. Here, the two mechanisms affecting the coupling strength between SST gradient and surface wind divergence are examined during an atmospheric front passage in the Southern Ocean. This event is also recorded by an uncrewed surface vehicle (USV). The reanalysis product (ERA5) revealed that downward momentum mixing is the dominant mechanism on the daily time scale. The coupling strength during the day when the atmospheric front passed over declined by 75%, compared to the adjacent days. This implies that the atmospheric front can partially attenuate the SST gradient effect on the surface wind divergence. Furthermore, a decade‐long statistic also showed a decreasing trend of SST‐wind coupling when the atmospheric fronts occur more. Additionally, after removing the mesoscale weather variation, the USV observations showed a remarkable SST imprint on the atmospheric boundary layer in the oceanic submesoscale regime, which denotes the scale below the deformation radius (∼16 km). The submesoscale air‐sea interaction processes also displayed decreased air‐sea coupling strength during atmospheric front passage. This is possible as the vertical velocity induced by the atmospheric front can compensate for the daily averaged uprising vertical velocity due to surface wind convergence. This analysis indicates that the atmospheric front can diminish the coupling between the SST gradient and surface wind divergence, which contrasts the existing statistical results showing that atmospheric fronts tend to enhance such coupling. Plain Language Summary: The atmospheric front is seldom directly observed in the Southern Ocean due to its short‐lived life cycle and the remoteness and harsh conditions. Consequently, the air‐sea interface variation is unknown during the atmospheric front passage. An unmanned surface vehicle coincidentally recorded the air‐sea interface parameter variations during the atmospheric front passage. Combined with the reanalysis data, this study indicates that the atmospheric front can weaken the air‐sea coupling strength and modify the processes of air‐sea energy transfer. A decade‐long statistic supports this result. This finding complements existing statistical results indicating that atmospheric fronts tend to enhance this coupling. Key Points: Atmospheric front can diminish the regional coupling strength between surface wind divergence and sea surface temperature (SST) gradientSaildrone observation supports the diminishes of SST‐wind coupling during atmospheric front passage at the submesoscale regimeDecade‐long statistics show a negative correlation between the SST‐wind coupling and regional atmospheric front ratio [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
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