An assessment of veering wind effects on scatterometry from the sea surface

Abstract

To characterize scatterometer returns from the sea surface near meteorological fronts, we investigated microwave scattering from seas in which long waves are at oblique angles to short waves. We simulate the effects of veering winds on C- and K_u-band scatterometers by using models in which the short waves align with the wind friction velocity u_∗ , but the long waves are at oblique angles to the u_∗ direction. The analysis reveals two main effects due to the rotation of the long wave slope probability density distribution. Azimuthally averaged normalized radar cross-section a _o decreases as the oblique angle increases. Additionally, two regimes exist. In the small angle regime, azimuthal scans of normalized radar cross-section σ^o exhibit features similar to the classic double-maxima pattern for non-veering wind conditions, but the axis of σ^o maxima is rotated toward the long-wave axis. In the large angle regime, more than two maxima are apparent in azimuthal scans. Therefore it may be inappropriate to use standard three term Fourier cosine models for some veering wind conditions.