Improved near real time surface wind resolution over the Mediterranean Sea

摘要

Several scientific programs, including the Mediterranean Forecasting System TowardEnvironmental Predictions (MFSTEP project), request high space and time resolutions ofsurface wind speed and direction. The purpose of this paper is to focus on surface windimprovements over the global Mediterranean Sea, based on the blending near real timeremotely sensed wind observations and ECMWF wind analysis. Ocean surface windobservations are retrieved from QuikSCAT scatterometer and from SSM/I radiometersavailable at near real time at Météo-France. Using synchronous satellite data, the number ofremotely sensed data available for each analysis epoch (00:00 h; 06:00 h; 12:00 h; 18:00 h) isnot uniformly distributed as a function of space and time. On average two satellite windobservations are available for each analysis time period. The analysis is performed byoptimum interpolation (OI) based on the kriging approach. The needed covariance matrixesare estimated from the satellite wind speed, zonal and meridional component observations.The quality of the 6-hourly resulting blended wind fields on 0.25° grid are investigated troughcomparisons with the remotely sensed observations as well as with moored buoy windaveraged wind estimates. The blended wind data and remotely wind observations, occurringwithin 3 h and 0.25° from the analysis estimates, compare well over the global basin aswell as over the sub-basins. The correlation coefficients exceed 0.95 while the rms differencevalues are less than 0.30 m/s. Using measurements from moored buoys, the high-resolutionwind fields are found to have similar accuracy as satellite wind retrievals. Blended windestimates exhibit better comparisons with buoy moored in open sea than near shore.