Accuracy of 10 m Winds from Satellites and NWP Products Near Land-Sea Boundaries

摘要

Through a comprehensive analysis, reliability of 10 m wind speeds is presented near the land-sea boundaries over the global ocean. Winds from three numerical weather prediction (NWP) centers and two satellite-based products are analyzed. NWP products are 1.875 deg x 1.875 deg National Center Environmental Prediction reanalyses, 1.125 deg x 1.125 deg European Centre for Medium-Range Weather Forecasts 40-year Reanalysis (ERA-40), and 1.0 deg x 1.0 deg Navy Operational Global Atmospheric Prediction System (NOGAPS) operational product. These are compared to much finer resolution (0.25 deg x 0.25 deg) satellite winds, Quick Scatterometer (QSCAT) and Special Sensor Microwave/Imager. Large biases (e.g., >3 m s-1) may exist in NWP products near the land-sea boundaries, because wind speeds from the uniformly gridded global fields are generally at a spatial scale too coarse to appropriately define the contrast between water and land grid points. This so-called land contamination of ocean-only winds varies, and typically depends on the extent of the land-sea mask. A creeping sea-fill methodology is introduced to reduce errors in winds. It is based on the elimination of land-corrupted NWP grid points and replacement by adjacent, purely over-ocean values. In comparison to winds from many moored buoys, the methodology diminishes RMS errors from >4 m s-1 to.