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 shortcomings in two existing CYGNSS gridded wind speed products, the L3 gridded fully developed seas wind speeds and the L3 storm-centric gridded products, which individually are optimized for global, nonstorm conditions and localized, high wind speed tropical cyclone (TC) 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 (±40
^o
latitude) windspeeds, averaged over a ±6 h window, and reported on a 0.1 × 0.1
^o
grid. Gridded wind speeds are reported every 6 h for each TC when there are overpasses available during that time interval. The files are output on a storm-by-storm basis. Quadrant-dependent TC 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 Hurricane Weather Research and Forecast model output and soil moisture active passive TC 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 TC 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 global navigation satellite system-reflectometry modality.