Putrasahan, D. A., A. J. Miller and H. Seo, 2012:
Isolating mesoscale coupled ocean-atmosphere interactions in the Kuroshio Extension region.
Geophysical Research Letters, sub judice.
Abstract.
The Kuroshio Extension region is characterized by energetic oceanic mesoscale and frontal variability
that alters air-sea fluxes that can influence large-scale climate variability in the North Pacific. We
investigate this mesoscale air-sea coupling using a regional eddy-resolving coupled ocean-atmosphere
(OA) model that downscales observed large-scale climate variability. The model simulates many
aspects of the observed seasonal cycle of OA coupling strength for both momentum and surface heat
fluxes. We introduce a new modeling approach to study the scale-dependence of two well-known
mechanisms for surface wind response to mesoscale sea surface temperatures (SST), namely, .vertical
mixing mechanism. (VMM) and .pressure adjustment mechanism. (PAM). We compare the fully
coupled model to the same model with an online, 2-D spatial smoother applied to remove mesoscale
SST field felt by the atmosphere. Both VMM and PAM are found to be active during the strong
wintertime peak in coupling strength seen in model and in observations. For VMM, large-scale SST
gradients surprisingly generate coupling between downwind SST gradient and wind stress divergence
that is often stronger than coupling on the mesoscale, indicating their joint importance in OA
interaction in this region. In contrast, coupling between crosswind SST gradient and wind stress curl
occurs only on the mesoscale, and not over large-scale SST gradients, indicating the essential role of
ocean mesoscale. For PAM, model results indicate that coupling between the Laplacian of sea level
pressure and surface wind convergence occurs for both mesoscale and large-scale processes, but
inclusion of the mesoscale roughly doubles the coupling strength.
Preprint (pdf)