What is the role of finescale processes in connecting the surface of the ocean and its interior?
The California Xover has been adopted by the mission Calibration and Validation (Cal/Val) team. The main purpose of the campaign was to provide the ground truth of the sea surface height at small scales (< ~ 100km) for the Cal/Val of the mission science requirement specified in wavenumber space. The ground truth should be free, as much as possible, of the noise and errors in satellite measurements. The steric-height approach had been adopted in the methodology, which involves observing temperature and salinity in the ocean interior to derive the steric height.
The campaign included 11 CTD moorings placed along a Sentinel-3A ground track, which is near the centre of a SWOT swath. 4 of the 11 moorings were deep-reaching to capture the deep high-frequency internal gravity wave signals. 7 moorings focused on the upper 500m to capture the small-scale surface intensified eddies. By combining the 11 moorings, researchers have been to reconstruct the synoptic SSH field covering 20 – 100 km wavelengths for validating SWOT SSH at these scales. At least two gliders sampled in the cross-swath direction and provided additional cross-swath information, as well as a means for risk reduction of any potential mooring malfunction. A barometer was placed in the centre mooring to measure atmospheric pressure.
The data gathered during the Cal/Val campaign are important to close the SSH budget and will shed light on the connections between the surface of the ocean and its interior.
In addition, the instrumentation enabled studies of small-scale ocean dynamics, such as the interaction between eddies and internal gravity waves and how to disentangle them from the SWOT measurements, and the vertical heat flux associated with small-scale eddies and eddy-wave interactions.
Surface currents (left panel) and relative vorticity ( ζ=vx−uy) normalized by Coriolis frequency (f) (right panel) for the California CalVal study site with SWOT grid overlaid (black lines). Images were generated using output from a high-resolution MITgcm simulation and are instantaneous snapshots from 1 July 2012.
Principal investigators: Uwe Send, Drew Lucas, Matthias Lankhorst, Amy Waterhouse (SIO/UCSD); Scott Stalin (PMEL/NOAA); Oscar Schofield (Rutgers Univ.); Tom Farrar, Magdalena Andres (WHOI); Lee-Lueng Fu, Bruce Haines (JPL/Caltech), Jinbo Wang (JPL/NASA).
Contact point for the study site: Jinbo Wang (jinbo.wang@jpl.nasa.gov)
