Surface winds (equivalent neutral wind velocities at 10 m) from scatterometer missions since 1992 have been used to build up a 20-year climate series. Optimal interpolation and kriging methods have been applied to continuously provide surface wind speed and direction estimates over the global ocean on a regular grid in space and time. The use of other data sources such as radiometer data (SSM/I) and atmospheric wind reanalyses (ERA-Interim) has allowed building a blended product available at 1/4° spatial resolution and every 6 hours from 1992 to 2012. Sampling issues throughout the different missions (ERS-1, ERS-2, QuikSCAT, and ASCAT) and their possible impact on the homogeneity of the gridded product are discussed. In addition, we assess carefully the quality of the blended product in the absence of scatterometer data (1992 to 1999). Data selection experiments show that the description of the surface wind is significantly improved by including the scatterometer winds. The blended winds compare well with buoy winds (1992-2012) and they resolve finer spatial scales than atmospheric reanalyses, which make them suitable for studying air-sea interactions at mesoscale. The seasonal cycle and interannual variability of the product compare well with other long-term wind analyses. The product is used to calculate 20-year trends in wind speed, as well as in zonal and meridional wind components. These trends show an important asymmetry between the southern and northern hemispheres, which may be an important issue for climate studies.
Highlights► 20-year blended of high-resolution (0.25deg, 6h) wind product from scaterrometry ► Blended product suitable for studying air-sea interactions at mesoscale. ► The product is used to calculate 20-year trends in wind speed, as well as in zonal and meridional wind components.A long record of ocean surface wind observations is essential for climate research and for addressing a variety of operational and scientific issues. Surface wind vectors are indeed the key drivers of oceanic and atmospheric processes that regulate the global and regional climate [e.g., Ricciardulli and Wentz, 2013]. Ocean winds are routinely used as the primary forcing function of numerical hydrodynamic models of the ocean circulation [e.g., Grima et al., 1999; Carton and Giese, 2009;Wunsch et al. 2009;Desbiolles et al., 2016] and of surface gravity waves [e.g., et al., 1988;Tolman 2002] at global and regional scales. Ocean winds are considered as the most important variable for investigating storm surges and wave forecasts at various space and time scales [Debernard et al., 2002]. They drive the variability of ocean processes such as coastal upwelling, primary productivity, cross-shelf transport, deep-water formation, ice transport, and they are of fundamental importance for the reliable estimation of air-sea momentum fluxes (wind stress vector), turbulent heat fluxes (latent and sensible), and gas exchanges (e.g. CO 2 and H 2 O). Longterm change in global winds is an important forcing and an indicator of cli...
