9:05 AM - 9:25 AM
[ACG29-02] Surface wind responses to mesoscale sea-surface temperature over western boundary currents assessed by spectral transfer functions
★Invited Papers
Satellite observations have revealed that mesoscale sea-surface temperature perturbations can exert significant influence on sea-surface winds. Recently, spectral transfer functions have shown to be useful to elucidate the wind responses (Scineider 2020). Transfer functions represent spatially lagged wind responses, their horizontal scale dependence, and background wind speed dependence at the same time. The present study explores regional differences and seasonality in the wind response over the major western boundary current regions by adopting the transfer function approach.
Structures of transfer fucntions estimated from satellite observations are largely consistent among the seasons and regions, suggesting that underlying dynamics are ubiquitous. Nevertheless, the wind response exhibits significant seasonality depending on background wind speed; when background wind speed is larger than 11 m/s, the wind response is larger in winter than in summer, and vice versa. The Agulhas Retroflection region exhibits significantly larger wind response typically by 30% than the Gulf Stream and Kuroshio Extension regions. ERA5 and regional model outputs are found to underestimate the wind speed response by typically 30 %.
The transfer function analysis can be adopted to many other atmospheric fields besides sea-surface wind, and thus it would provide a new insight into the climatic role of the mesoscale air-sea coupling.
Structures of transfer fucntions estimated from satellite observations are largely consistent among the seasons and regions, suggesting that underlying dynamics are ubiquitous. Nevertheless, the wind response exhibits significant seasonality depending on background wind speed; when background wind speed is larger than 11 m/s, the wind response is larger in winter than in summer, and vice versa. The Agulhas Retroflection region exhibits significantly larger wind response typically by 30% than the Gulf Stream and Kuroshio Extension regions. ERA5 and regional model outputs are found to underestimate the wind speed response by typically 30 %.
The transfer function analysis can be adopted to many other atmospheric fields besides sea-surface wind, and thus it would provide a new insight into the climatic role of the mesoscale air-sea coupling.