Reevaluating Passive Ocean Vector Winds

Measurements from polarimetric space-based microwave radiometers can be used to retrieve global ocean surface vector winds. This capability was first demonstrated with WindSat and is also planned for the Microwave Imager/Sounder (MIS) which will be aboard the NPOESS satellites commencing with NPOESS C-2. To date nearly all detailed evaluations of WindSat ocean vector winds have used early versions of WindSat ground data processing software and retrieval algorithms. These evaluations have included comparisons to ocean surface vector winds from QuikSCAT, buoys and numerical weather predictions models. WindSat winds have also been evaluated for their impact on numerical weather prediction models when assimilated into the models and are now operationally assimilated into the U.S. Navy NOGAPS model, and the global models at the U.K. Met Office and NOAA NCEP.

Numerous improvements have been made to WindSat ground data processing software and retrieval algorithms since these evaluations were completed. These improvements include higher resolution retrievals, improved wind vector ambiguity selection, better brightness temperature calibration and resampling and improved high wind speed retrievals. We briefly describe some of these improvements and provide statistical comparisons of the current WindSat ocean vector wind products to the older versions of the WindSat products. We also present comparisons for individual wind fields including examples of gap wind events and cyclonic storms. These comparisons suggest the need to evaluate the latest WindSat products to fully understand the potential operational impact of passive ocean vector winds..