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Long-Term Evolution and Coupling of the Boundary Layers in the STRATUS Deck Regions of the Eastern Pacific

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July 1, 2004 through June 30, 2005

Dr. Robert A. Weller
Woods Hole Oceanographic Institution

Program Manager: Dr. Michael Patterson NOAA/OGP

Related NOAA Strategic Plan Goal:
Goal 2. Understand climate variability and change to enhance society’s ability to plan and respond.

The stratus project has been successful in elucidating the physical processes that maintain the observed cool surface waters of the Peru-Chile stratus region. Colbo and Weller (2005a) synthesized the mooring data with historical hydrographic and satellite data to show that the upper ocean heat and salt budgets had a large component that was contributed by the divergence of the “eddy” flux. This large transport of cool, fresh water from the coastal upwelling region to the deep ocean through the eddy field has not been noted before. It also helps explain the deficiencies observed in many global models of the region, which are not eddy resolving, and hence cannot adequately capture this important oceanic transport.

In using the ocean reference station data for this project, as well as others, it was necessary to understand the accuracy of the basic surface meteorology and the derived flux products. To this end a series of meetings was organized for the scientific and engineering staff at WHOI with direct experience of the IMET package. (The IMET package is the standard meteorological sensor suite used on all the Ocean Reference Stations, as well as most US Volunteer Observing Ships and Research Vessels.) These meetings have been synthesized into a single document which has now been transformed into a journal article (Colbo and Weller 2005b). It lays out the
expected accuracy of all the individual meteorological sensors in detail, and shows how those errors propagate into the heat, freshwater and momentum fluxes. This is a crucial step in validating the observations and is necessary for any future climate studies involving the Ocean Reference Station data.

The first four years of surface meteorological and air-sea flux data is being used to describe and characterize the surface forcing and atmosphere-ocean coupling observed under the stratus cloud deck at a site close to the region of climatological maximum low cloud cover (Weller and Colbo 2005). This site is data sparse, and these buoy data provide the first accurate long time series that can be used to characterize the site. Both model and climatological values are found to differ significantly from the observations. Though the regime is basically a trade wind regime, with very stable wind direction, wind speed at times drops to low enough values to allow strong diurnal warming in sea surface temperature. Strong diurnal variability is also found in other variables, including the incoming longwave radiation. Links between local variability at diurnal and synoptic time scales to regional synoptic variability are being explored. At the same time significant interannual variability and work is underway to examine whether or not this is tied change in the South Pacific subtropical circulation in the atmosphere and to other causes.

Colbo, K. and R. A. Weller 2005a: The variability and heat budget of the upper ocean under the
Chile-Peru stratus. Journal of Marine Research, submitted.
Colbo, K. and R. A. Weller 2005b: The accuracy of the IMET sensor package. Journal of
Atmospheric ad Oceanic Technology, almost submitted.
Weller, R. A. and K. Colbo 2005: Surface Meteorology and Air-Sea Fluxes Under the Stratus
Clouds off Northern Chile. In preparation.

“What Maintains the Cold Ocean off of Peru”: VOCALS Science and Implementation Workshop, Corvallis, 2004 (talk)
“Climate Observations from the Peru-Chile Stratus Deck”: International CLIVAR Science Conference, Baltimore, 2004 (poster)
“How Accurate are Surface Meteorology Measurements from a Buoy?”: International CLIVAR Science Conference, Baltimore, 2004 (poster)
“Observations from the subtropical Pacific Ocean: What sets SST under the clouds?”: AGU Ocean Sciences, Portland, 2004 (poster)
“Moored Observations from Under the Stratus Deck”: EPIC-PACS meeting, Boulder, 2003 (poster)

“Upper Ocean variability in the Chile-Peru Stratus” University of New South Wales @ Australian Defense Force Academy --- March 2005
Woods Hole Oceanographic Institution --- April 2005
“What maintains the cool SST under the Chile-Peru Stratus Deck”
Oregon State University,
University of Washington,
University of British Columbia,
University of Victoria,
Institute of Ocean Sciences --- October 2004

Attend and present at the NOAA sponsored EPIC/PACS meeting, Boulder 2003
Attend and present at the NOAA sponsored VOCALS Planning Meeting, Corvallis, 2004
Discussions with NOAA scientists outside of NOAA sponsored meetings, including: Meghan
Cronin, Mike McPhaden, Gregory Johnson, and Chris Fairall.

Last updated: August 19, 2008

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