Warm core ring velocities inferred from NSCAT

The NASA scatterometer, NSCAT, was designed to estimate from space the wind velocity relative to the ocean surface velocity. Assuming that the spatial scale of the meteorological forcing giving rise to the wind is large compared with the diameter of a warm core ring, it should be possible to obtain information about the currents in the ring from the demeaned scatterometer winds. To test this hypothesis, 14 NSCAT passes obtained within three days of clear AVHRR-derived sea surface temperature images showing a warm core ring were analyzed for evidence of circulation in the rings. The residual wind vectors for the 14 scatterometer passes were binned and averaged by radial distance from ring center. The mean azimuthal component of the speed compares well with ADCP data collected in one of the rings: a maximum of approximate to0.89 m/s approximate to 50 km from ring center compared with 0.88 m/s and 1.0 m/s for the two ADCP transects, both also at 50 km from ring center.