Mapping Mesoscale and Submesoscale Wind Fields Using Synthetic Aperture Radar and AASERT Supplement.

摘要

Synthetic Aperture Radar (SAR) imagery has shown great promise for depicting the vast array of phenomena that govern the behavior of the ocean mixed layer and marine atmospheric boundary layer (MABL). (Alpers, et al., 1981; Beal, et al., 1981; Vesecky and Stewart, 1982). The variation of the backscattered intensity field depicted in SAR imagery is directly related to the horizontal distribution of those sea-surface roughness elements having scales generally comparable to the wavelength of the radiation transmitted by the SAR. The local amplitude of the (centimeter-scale for most SAR systems) surface waves that produce this roughness depends on a broad range of oceanic and atmospheric processes and their interactions (e.g., Elachi, 1987). Because these waves are driven by the surface stress and locally modulated by wave-current interactions and surfactant slicks, SAR images frequently reveal features related to oceanographic processes such as current boundaries, internal waves, or tidal flow over bathymetry, as well as variations in the surface stress due to atmospheric processes. Our long-term goal in this research effort is to utilize the multiscale information in the atmospheric signatures on SAR images to diagnose a quantitative description of the MABL, including the depth, stability, wind speed, wind direction, sea-surface stress, and buoyancy flux on the mesoscale and submesoscale. Because of its potential for yielding both boundary layer depth and the surface wind field at high horizontal resolution, this application of SAR data represents a significant and innovative advance over most scatterometer algorithms that yield only coarse-resolution wind fields. Moreover, because conventional scatterometry cannot resolve the turbulence structures in the MABL, it cannot be used to diagnose the surface layer stability and so cannot yield wind speed estimates corrected for this important effect.