CYGNSS Gridded Global Wind Vectors: Variational Analysis with GFS Backgrounds

Ocean surface wind speed retrievals from the Cyclone Global Navigation Satellite System (CYGNSS; Ruf et al., 2016) are assimilated using variational analysis to produce global gridded wind vector analyses. Six-hourly analyses were produced throughout the 2017 Atlantic hurricane season and provide insight about the value/quality of the observations (observation minus analysis statistics) as well as error characteristics of the backgrounds used as the starting points for the analyses (observation minus background statistics). GFS operational analyses are used as the backgrounds. The analyses are computed using the Variational Analysis Method (VAM), developed by Hoffman (1982, 1984, 2003). For computational efficiency, the VAM produces these analyses in stages, using telescoping resolution from coarse to fine, to achieve a final, high-resolution analysis. The resulting gridded VAM analysis vector wind data sets are 0.2 x 0.2 degree latitude/longitude resolution grids between 40 south latitude and 40 north latitude. These data are compared to CYGNSS Level 3 wind data products which also aggregate Level 2 winds to a 0.2 x 0.2 degree resolution grid. The analyses are based on the latest available version of the CYGNSS Level 2 data which are currently undergoing calibration and validation.