An introductory review of the measurement of ocean surface wind vectors with a satellite radar scatterometer

Abstract

A brief introduction is given to the field of remote measurement of the surface wind vector field over the ocean usingradar scatterometry from satellites.A summary of the physical processes involved in the measurement is given, together with a reviewof recent studiesto employ thesedata in numericalweather prediction modelling, and suggestions are advanced for some future simulation studies.The emphasis here is on the data obtained by SEASAT. The intent is that such data may be used to develop and refine integrated analysis programmes that can take increased advantage of the scatterometer data streams that are planned to be available from ERS-I and N-ROSS commencing in 1989.

Katabatic wind propagation over the western Ross Sea observed using ERS-1 scatterometer data

“…Nominal instrument accuracies for the ERS-112 scatterometer are 2 ms-' (in the range of 4-24 ms-l) and 20" for wind speed and direction, respectively (Offiler 1994). Areview of the theory behind scatterometer measurements of winds over the ocean is given by Thomas & Minnett (1986), while the various difficulties that exist in extracting accurate wind vectors from scatterometer dataparticularly the directional component, which can suffer from a 180" ambiguityare summarised by Marshall & Turner (in press). The data used in this study have been processed using the offline IFREMER (Institut Francais de Recherche pour 1'Exploitation de la Mer) algorithm, and have been made available to the British Antarctic Survey in the form of a CD-ROM archive (Quilfen 1995), which may be interrogated easily, both temporally and/or spatially, thus enabling the efficient extraction of data specific to the case study.…”

Surface wind fields of Antarctic mesocyclones derived from ERS 1 scatterometer data

“…The energy transmitted back to the radar from the ocean is assumed to be solely dependent on the small-scale Bragg-resonant ripples, termed capillary waves, which are the product of the frictional interaction of wind on the sea surface [Thomas and Minnett, 1986]. A model is used to relate this sea surface roughness, through the radar backscatter coefficient, to wind speed and, because this roughness is anisotropic (as crests and troughs are generally orthogonal to the wind direction), wind direction as well.…”

Temporal and spatial variation of the surface winds in the Gulf of California

“…The concept of remote sensing of ocean surface winds is based on a model which relates the roughness of the sea surface to the wind speed. As expected from crests and thoughs tending to be perpendicular to wind direction, the roughness is anisotropic and this is the key to determine wind direction and speed [ Thomas and Minnett , 1986]. What makes the scatterometer unique is its ability to measure both wind speed and direction.…”