Comparisons and Evaluations between the Oceansat-2 (OSCAT) and ASCAT Scatterometers over Tropical Cyclones

Characteristics of the latest satellite-based global scatterometer, Oceansat-2 (OSCAT), are presented in comparison with the European Advanced Scatterometers A&B (ASCAT) for their use in near real-time tropical cyclone analyses. Ocean surface vector wind retrievals obtained from both the OSCAT and ASCAT developed at NOAA/NESDIS, along with higher resolution products from the BYU Microwave Earth Remote Sensing (MERS) laboratory are evaluated in the hope of determining the accuracy of the ocean surface wind coverage that was once provided by the QuikSCAT scatterometer. Comparisons between the various products require a robust method of identifying the basic features that were once possible in the QuikSCAT imager. These products include depicting tropical cyclone positions, determining outer wind structure and providing a minimum (at least) value of maximum intensity. As was the case with the QuikSCAT data, determining these feature are still a challenge and require a learning process. Use of not only the wind vectors, but also the ambiguities, the normalized radar cross-sections (NRCS) and the many possible overlays of both traditional IR/Vis imagery and the various microwave images are still required in order for the analyst to understand the effects of rain contamination, data resolution and the tuning of the retrieval algorithm. Results of this study show that although the QuikSCAT is greatly missed, the scatterometer is still a valuable tool to aid the world's tropical cyclone forecasting centers in maintaining improved forecasts and warnings.