Measurements of the Effect of Rain-Induced Sea Surface Roughness on the QuikSCAT Scatterometer Radar Cross Section

• Published in: IEEE transactions on geoscience and remote sensing Vol. 46; no. 10; pp. 2882 - 2894
• Main Authors: Weissman, D.E., Bourassa, M.A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.10.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied geophysics; Earth sciences; Earth, ocean, space; Exact sciences and technology; Internal geophysics; Marine; Normalized radar cross section (NRCS); Polarization; QuikSCAT/SeaWinds radar; Radar cross section; Radar cross sections; Radar data; Radar measurement; Radar measurements; Rain; rainrate over the oceans; Rough surfaces; Roughness; Scatterometers; Sea measurements; Sea surface; Sea surface roughness; Studies; Surface roughness; Tanks; Wind; North Atlantic; Gulf of Mexico; Atlantic Ocean; Northwest Atlantic; North American Atlantic; USA, Texas, Houston; ASW, Mexico Gulf; ASW, USA, Texas, Corpus Christi; wave scattering; rainfall; attenuation; atmospheric precipitation; Space remote sensing; platforms; rainrate over the oceans; ocean; roughness; QuikSCAT/SeaWinds radar; polarization; Normalized radar cross section (NRCS); radar methods; surface properties; high resolution
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2008.2001032

Radar measurements of the sea surface, with satellite scatterometers that operate at K u -band, are affected by the presence of rain through modification of the sea surface roughness by rain impacts. This is in addition to wind driven roughness, atmospheric scattering, and attenuation that affect the measured normalized radar cross section (NRCS). This paper presents a case study of the increase of the total radar cross section, averaged across surface illuminated areas (individual footprints) of the SeaWinds scatterometer (on QuikSCAT) caused by rain striking the sea surface. This effort combines satellite-based K u -band data with high-resolution 3-D volumetric rain measurements, from simultaneous collocated Next Generation Weather Radar data. The results to be presented were acquired during a significant rain event in the Gulf of Mexico, to the east of Corpus Christi, and just south of Houston, TX, in May 2005. The results of this paper show dependence on wind speed, rainrate, and polarization. They agree with numerous surface-based studies (single point measurements), using ocean platforms and wind-wave tanks, whose data were collected under similar conditions. For example, at rainrates less than 10 mm/hr, the relative change in surface roughness is seen to decrease as the wind magnitude increases from 5 to 7 m/s. Another consistent observation is that the vertical polarization NRCS shows less sensitivity to rainrate than does horizontal.