SEMINAR: MPO Special Seminar: Dr. Dian Putrasahan, TODAY, at 1:30 p.m., MSC 343

[Sandrine Apelbaum <sapelbaum@rsmas.miami.edu>]

MPO Special Seminar

Dr. Dian Putrasahan

"Mesoscale Coupled Ocean-Atmosphere Feedback in Boundary Current Systems"

 

Room: MSC 343

Date: Monday, October 29, at 1:30 p.m.

Abstract:

A study of ocean-atmosphere (OA) interactions is conducted over the Humboldt Current System (HCS) and Kuroshio Extension (KE) region using the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model. This model comprises of the Regional Ocean Modeling System (ROMS) as the oceanic part, and the Regional Spectral Model (RSM) as the atmospheric component. Within SCOAR, a new technique is introduced by implementing an interactive 2-D spatial smoother within the SST-flux coupler to remove the mesoscale SST field felt by the atmosphere. This procedure allows large-scale SST coupling to be preserved while extinguishing the mesoscale eddy impacts on the atmospheric boundary layer (ABL). This novel approach provides us insights to the spatial-scale dependence of OA coupling, and the impact of mesoscale features on both the ABL and the surface ocean.

In the HCS study, we find significant SST-wind stress coupling during fall and winter for Control SCOAR and insignificant coupling throughout for Smoothed SCOAR. This suggests the vital role of ocean mesoscale eddies on air-sea coupling in HCS. In addition, coupling between SST, wind speed and latent heat flux is found to be significant on the mesoscale and insignificant on large-scale coupling and full coupling mode. This suggest the influence of mesoscale SST on latent heat flux is through both direct flux anomalies, and indirectly through changes in the stability of the overlying atmosphere, which in turn affects the wind speeds and thus latent heat flux.

In the KE region, we study the spatial scale dependence of surface wind response to mesoscale SST via two well-known mechanisms, the vertical mixing mechanism (VMM) and the pressure adjustment mechanism (PAM). Wintertime peaks in coupling strengths are seen in both VMM and PAM. For VMM, coupling between downwind SST gradients and wind stress divergence are found to be significant on both the large scale and mesoscale, with the large scale often exhibiting stronger coupling than on mesoscale. This reflects the joint importance of large-scale and mesoscale coupling in this region. For PAM, coupling strength is significant in both mesoscale and large scale, with mesoscale coupling being almost double that of coupling at large scale. Ocean mesoscale imprints are also seen on precipitation anomalies, whereby their differences coincide with differences in surface wind convergence and SST gradients instead of SST anomalies. 

Sandrine Apelbaum

Meteorology and Physical Oceanography 
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami, FL 33149-1098
Tel     (305) 421-4057
Fax     (305) 421-4696

sapelbaum@rsmas.miami.edu