CYGNSS Level 3 Merged Wind Speed Data Product for Storm Force and Surrounding Environmental Winds

A new wind speed product has been developed using bistatic radar data from NASA's Cyclone Global Navigation Satellite System (CYGNSS) mission. The product addresses short-comings in two existing CYGNSS gridded wind speed products, the L3 Gridded Fully Developed Seas (FDS) Wind Speeds and the L3 Storm-Centric Gridded products, which individually are optimized for global, non-storm conditions and localized, high wind speed tropical cyclone conditions, respectively. In order to create a unified gridded wind speed product that captures both the storm force winds and the far-field environmental wind speeds, wind fields from the two products are merged onto a common grid. The algorithm produces global (+/- 40o latitude) windspeeds, averaged over a +/-6 hour window, and reported on a 0.1x0.1o grid. Gridded wind speeds are reported every 6 hours for each tropical cyclone when there are overpasses available during that time interval. The files are output on a storm-by-storm basis. Quadrant-dependent tropical cyclone 34-knot wind radii are estimated from the merged wind fields and included in the dataset. The performance of the merged wind speed product is validated against HWRF model output and SMAP tropical cyclone wind products, and the temporal and spatial sampling of the dataset is characterized. The dataset is found to exceed current temporal coverage capabilities compared to other existing tropical cyclone wind speed remote sensing instruments, although limitations on high wind speed retrievals and variable spatial coverage are notable and can be attributed to weaknesses of the underlying GNSS-R modality.