Preprint Article Version 1 This version is not peer-reviewed

Low-Frequency Sea Surface Radar Doppler Echo

Version 1 : Received: 20 April 2018 / Approved: 23 April 2018 / Online: 23 April 2018 (11:46:21 CEST)

A peer-reviewed article of this Preprint also exists.

Yurovsky, Y.Y.; Kudryavtsev, V.N.; Grodsky, S.A.; Chapron, B. Low-Frequency Sea Surface Radar Doppler Echo. Remote Sens. 2018, 10, 870. Yurovsky, Y.Y.; Kudryavtsev, V.N.; Grodsky, S.A.; Chapron, B. Low-Frequency Sea Surface Radar Doppler Echo. Remote Sens. 2018, 10, 870.

Journal reference: Remote Sens. 2018, 10, 870
DOI: 10.3390/rs10060870

Abstract

Observed sea surface Ka-band normalized radar backscatter cross section (NRCS) and Doppler velocity (DV) exhibit energy at low frequencies (LF) below the surface wave range. It is shown that non-linearity in NRCS-wave slope Modulation Transfer Function (MTF) and inherent NRCS averaging within the footprint account for the NRCS and DV LF variance with the exception of VV NRCS for which almost half of the LF variance is attributable to wind fluctuations. Although the distribution of radar DV is quasi-Gaussian suggesting virtually little impact of non-linearity, the LF DV variations arise due to footprint averaging of correlated local DV and non-linear NRCS. Numerical simulations demonstrate that MTF non-linearity weakly affects traditional linear MTF estimate (less than 10% for |MTF|< 20). Thus the linear MTF is a good approximation to evaluate the DV averaged over large footprints typical of satellite observations.

Subject Areas

Radar; ocean; backscatter; Doppler shift; wave groups; non-linearity; modulation

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