Estimating Sea Surface Vorticity from the RapidScat Scatterometer Ku-Band NRCS by Using Coincident Sub-Footprint Scale Winds and Dual Polariztion Analysis

This study combines very high resolution wind vectors in the Gulf of Mexico coincident with normalized radar cross section (NRCS) measurements of the sea surface. The NRCS is provided by the RapidScat Ku-band scatterometer mission on the International Space Station (ISS). The sub-footprint winds are from a new high-resolution wind vector analysis (hourly, 2.5 km grid spacing): the Real Time Mesoscale Analysis (RTMA), from NOAA-NCEP. A second coincident wind field (with a coarser spatial resolution) is available from the standard level 2B PO.DAAC product derived from the same scatterometer data, The time frame for the measurements and analysis shown below is that of a single orbit of the ISS. One topic of interest is observing how calculations of the vorticity, using two data products with different spatial scales are related to each other, and to the radar backscatter for each of the two radar polarizations. Vorticity is a key ocean forcing parameter. Calculations using the scatterometer L2B winds show roughly similar vorticity between the two wind products over a range of weather conditions. The NRCS spatial variations for both H-pol and V correlate well with the notable vorticity features derived from the wind products.