Ocean Dynamics

, Volume 63, Issue 5, pp 463–488 | Cite as

Regional coupled ocean–atmosphere downscaling in the Southeast Pacific: impacts on upwelling, mesoscale air–sea fluxes, and ocean eddies

  • Dian A. Putrasahan
  • Arthur J. Miller
  • Hyodae Seo


Ocean–atmosphere coupling in the Humboldt Current System (HCS) of the Southeast Pacific is studied using the Scripps Coupled Ocean–atmosphere Regional (SCOAR) model, which is used to downscale the National Center for Environmental Prediction (NCEP) Reanalysis-2 (RA2) product for the period 2000–2007 at 20-km resolution. An interactive 2-D spatial smoother within the sea-surface temperature (SST)–flux coupler is invoked in a separate run to isolate the impact of the mesoscale (∼50–200 km, in the oceanic sense) SST field felt by the atmosphere in the fully coupled run. For the HCS, SCOAR produces seasonal wind stress and wind stress curl patterns that agree better with QuikSCAT winds than those from RA2. The SCOAR downscaled wind stress distribution has substantially different impacts on the magnitude and structure of wind-driven upwelling processes along the coast compared to RA2. Along coastal locations such as Arica and Taltal, SCOAR and RA2 produce seasonally opposite signs in the total wind-driven upwelling transport. At San Juan, SCOAR shows that upwelling is mainly due to coastal Ekman upwelling transport, while in RA2 upwelling is mostly attributed to Ekman pumping. Fully coupled SCOAR shows significant SST–wind stress coupling during fall and winter, while smoothed SCOAR shows insignificant coupling throughout, indicating the important role of ocean mesoscale eddies on air–sea coupling in HCS. Coupling between SST, wind speed, and latent heat flux is incoherent in large-scale coupling and full coupling mode. In contrast, coupling between these three variables is clearly identified for oceanic mesoscales, which suggests that mesoscale SST affects latent heat directly through the bulk formulation, as well as indirectly through stability changes on the overlying atmosphere, which affects surface wind speeds. The SST–wind stress and SST–heat-flux couplings, however, fail to produce a strong change in the ocean eddy statistics. No rectified effects of ocean–atmosphere coupling were identified for either the atmospheric or oceanic mean conditions, suggesting that mesoscale coupling is too weak in this region to strongly alter the basic climate state.


Eastern boundary current Humboldt Current Peru current VOCALS Coupled ocean–atmosphere feedbacks Mesoscale eddies Surface fluxes 



This study forms a portion of the Ph.D. dissertation of DAP. Funding was provided by NSF (OCE-0744245, OCE-0960770, OCE-1026607, and AGS-1048995), Department of Energy (DE-SC0002000), and NOAA (ECPC: NA17RJ1231). The views expressed herein are those of the authors and do not necessarily reflect the views of NOAA or any of its subagencies. We thank Joel Norris, Sarah Gille, Guang Zhang, Shyh Chen, Francois Colas, Xavier Capet, Vincent Combes, and Kei Yoshimura for helpful discussions and suggestions. The comments of the two anonymous referees significantly improved the presentation of results.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Dian A. Putrasahan
    • 1
    • 2
  • Arthur J. Miller
    • 1
  • Hyodae Seo
    • 3
  1. 1.Scripps Institution of OceanographyUniversity of California, San DiegoLa JollaUSA
  2. 2.Rosenstiel School of Marine and Atmospheric SciencesUniversity of MiamiMiamiUSA
  3. 3.Woods Hole Oceanographic InstitutionWoods HoleUSA

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