Improving Wave‐Based Air‐Sea Momentum Flux Parameterization in Mixed Seas. Issue 3 (13th March 2023)

• Record Type: Journal Article
• Authors: Sauvage, César; Seo, Hyodae; Clayson, Carol Anne; Edson, James B.
• Is Part Of: Journal of geophysical research. Volume 128:Issue 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-13
• Subjects: waves -- momentum flux -- coupled modeling; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2022JC019277
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: In winter, the Northwest Tropical Atlantic Ocean can be characterized by various wave age‐based interactions among ocean current, surface wind and surface waves, which are critical for accurately describing surface wind stress. In this work, coupled wave‐ocean‐atmosphere model simulations are conducted using two different wave roughness parameterizations within COARE3.5, including one that relies solely on wind speed and another that uses wave age and wave slope as inputs. Comparisons with the directly measured momentum fluxes during the ATOMIC/EUREC 4 A experiments in winter 2020 show that, for sea states dominated by short wind waves under moderate to strong winds, the wave‐based formulation (WBF) increases the surface roughness length in average by 25% compared to the wind‐speed‐based approach. For sea states dominated by remotely generated swells under moderate to strong wind intensity, the WBF predicts significantly lower roughness length and surface stress (≈15%), resulting in increased near‐surface wind speed above the constant flux layer (≈5%). Further investigation of the mixed sea states in the model and data indicates that the impact of swell on wind stress is over‐emphasized in the COARE3.5 WBF, especially under moderate wind regimes. Various approaches are explored to alleviate this deficiency by either introducing directional alignment between wind and waves or using the mean wave period instead of the wave period corresponding to the spectral peak to compute the wave age. The findings of this study are likely to be site‐dependent, and mostly concern specific regimes of wind and waves where the original parameterization was deficient. Plain Language Summary: Accurately understanding and describing air‐sea interactions is critical for weather forecast and regional climate. In this work, we use numerical experiments with and without taking into account the ocean waves to describe air‐sea interactions. Most of the momentum exchange between the ocean and the atmosphere is done through locally wind‐generated waves, however remotely generated waves, such as swells, can also interfere in these air‐sea interactions. Comparisons with observations made during the ATOMIC/EUREC 4 A field campaigns in winter 2020 show in particular that our numerical experiment overestimated the impact of the swell on the atmosphere. Various approaches are explored here to alleviate this deficiency, one of those being the introduction of the effect of the alignment between wind and waves. Key Points: Surface stress at moderate to high winds is dominated by short wind waves COARE3.5 wave based formulation can underestimates surface stress by more than 10% in mixed sea conditions under moderate to high wind Using the mean wave period or including the directional alignment between wind and wave in COARE3.5 alleviates this issue