Thursday 25 August 2005

PB5

PTH0142
Aircraft observations of sea surface salinity and Columbia River Plume response to along-shelf winds
Burrage, Derek¹, Wesson, Joel¹, Baptista, Antonio²
1 Ocean Sciences Branch, Naval Research Laboratory, USA
2 School of Science and Engineering, Oregon Health & Science University, USA
Author email: burrage@nrlssc.navy.mil
The NRL Salinity Temperature and Roughness Remote Scanner (STARRS) was flown over the Columbia River plume and adjacent shelf waters during Spring, 2004 to study plume evolution under prevailing wind and tidal conditions. STARRS is an advanced radiometer system consisting of microwave L and C-band, and infrared radiometers for measuring salinity, roughness and sea surface temperature, respectively. Using STARRS, nine sea surface salinity remote sensing surveys were conducted off the Oregon coast at intervals of 1-2 days during 17-28th May, 2005. Coincident hydrographic and meteorological data were obtained, as part of the experiment, from ships and from CORIE environmental observation and forecasting system oceanographic moorings (http://www.ccalmr.ogi.edu/CORIE/). NOAA data buoys provided additional wind and temperature data, while an HF coastal radar system established separately by Kosro et al. (OSU), yielded daily surface current maps. During the 12-day survey period, the CORIE numerical hydrodynamic model provided near real-time forecasts of plume location, to aid flight planning, and STARRS data were analyzed and returned after each flight to CORIE headquarters, for comparison with recent model predictions. The combined data set represents a unique time series of spatial maps that combine remotely sensed, in situ, and modelled sea surface salinity fields. The maps were used to track the plume response to fluctuating along-shelf winds, as they switched through a complete cycle of upwelling and downwelling favorable conditions. The data are used to classify the observed Columbia River plume as surface-advected and its predominantly bulging appearance suggests super-critical and (weakly) diffusive dynamics (Avicola & Huq, 2002; Chao, 1988). The results show the plume responded rapidly to daily changes in wind forcing, occasionally shedding eddies as it switched between up and down-coast orientations, in partial agreement with model predictions. Avicola and Huq (2002), JPO, 32, 3233-48. Chao (1988), JPO, 18, 72-88.

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