The remotely sensed winds and latent heat fluxes are mainly derived from the scatterometers onboard the European Remote Sensing Satellites (ERS-1 and ERS-2), NASA scatterometer (NSCAT) onboard ADEOS-1, Seawinds scatterometer onboard QuikSCAT, and from the radiometers onboard the Defense Meteorological Satellite Program (F10, F11, F13, F14, and F15). The periods of data availability are summarized in the following table:
December 1990 ? November 1997
December 1991 ? May 2000
May 1995 ? Present
May 1997 ? Present
December 1999 ? August 2006
August 1991 ? May 1996
March 1995 ? January 2001
September 1996 ? June 1997
July 1999 ? Present
The methods used to derive the satellite turbulent fluxes are described in Bentamy et al. (2003). They are based on the bulk aerodynamic formulae that parameterize the wind stress and latent heat flux :
where ? is the wind stress vector and ? τ ?x, ?y are its zonal and meridional components, respectively. is the latent heat flux; (), are the surface wind speed (zonal and meridional components) and air specific humidity at 10 m height and neutral stratification; and is the specific humidity at the sea surface equivalent to the saturation value at the sea surface temperature; l is the coefficient for latent heat of evaporation; ?is the air density; CDN and CEN are the bulk drag and the transfer coefficient for water vapor, respectively. The input variables, , and sea surface temperature (SST), from which is calculated, can be estimated from satellite observations ( e.g., Bentamy et al., 2002; Bentamy et al, 2003; Liu and Niiler, 1994; Schultz et al., 1993, 1997).
The quality of the derived surface winds and latent heat fluxes was investigated through comprehensive comparisons with buoy and ship estimates (Bentamy et al, 2002 and 2003). The remotely sensed flux observations are then used to estimate regular flux fields in space and time over the global ocean.
The present study employs the weekly- and monthly-averaged fluxes at 1° x 1° resolution available during the study period March 1992 ? March 2006. The accuracy of the resulting weekly fields is determined by comparisons with moored-buoy wind and latent heat flux estimates, which are deployed and maintained by four different institutions in the Atlantic and Pacific oceans. For instance, the agreement between satellite and in-situ data is good enough to suggest thatsources are achieving their accuracy goals. It was found that the satellite weekly ?x, ?y and exhibited the main known spatial and temporal characteristics at global as well as at local scales. The local variability ofthe three surface parameters is well revealed by the satellite time series in tropical and in North Atlantic areas (with respect to buoy and ship data). The mean and rms difference between buoy and remotely sensed flux estimates are quite low. For instance, at the Tropical area, the bias values for wind stress and latent heat flux are 0.5 10-2N/m2 and 7.0W/m2, respectively. The corresponding rms values are 1.5 10-2N/m2 and 29W/m2.