статья в журнале

En

REMOTE SENSING

ISSN:2072-4292

2019

Grodsky, S.A.¹

Chapron, B.²

10.3390/rs11070839

Multi-year field measurements of sea surface Ka-band dual-co-polarized (vertical transmit-receive polarization (VV) and horizontal transmit-receive polarization (HH)) radar Doppler characteristics from an oceanographic platform in the Black Sea are presented. The Doppler centroid (DC) estimated using the first moment of 5 min averaged spectrum, corrected for measured sea surface current, ranges between 0 and approximate to 1 m/s for incidence angles increasing from 0 to 70 degrees. Besides the known wind-to-radar azimuth dependence, the DC can also depend on wind-to-dominant wave direction. For co-aligned wind and waves, a negative crosswind DC residual is found, approximate to-0.1 m/s, at approximate to 20incidence angle, becoming negligible at approximate to 60, and raising to, approximate to+0.5 m/s, at >70 degrees<. For our observations, with a rather constant dominant wave length, the DC is almost wind independent. Yet, results confirm that, besides surface currents, the DC encodes an expected wave-induced contribution. To help the interpretation, a two-scale model (KaDOP) is proposed to fit the observed DC, based on the radar modulation transfer function (MTF) previously developed for the same data set. Assuming universal spectral shape of energy containing sea surface waves, the wave-induced DC contribution is then expressed as a function of MTF, significant wave height, and wave peak frequency. The resulting KaDOP agrees well with independent DC data, except for swell-dominated cases. The swell impact is estimated using the KaDOP with a modified empirical MTF.

RADAR, SCATTEROMETER, OCEAN, BACKSCATTER, DOPPLER SHIFT, DOPPLER CENTROID, SEA SURFACE CURRENT, WIND DRIFT, MODULATION, TRANSFER FUNCTION, EMPIRICAL MODEL

2019-12-12 15:49:00