SEASAT measurements of wind and waves on selected passes over JASIN

Abstract

SEASAT's ability to measure surface wind and wave fields over the area of the Joint Air-Sea Interaction experiment (JASIN) by means of its radar altimeter, microwave radiometer, scatterometer and synthetic aperture radar (SAR) has been analysed over some eight passes selected to provide a variety of surface conditions from light winds (4m/s) to moderately strong winds (16-20m/s). Comparisons were made not only with observations from research vessels and buoys but also between one SEASAT sensor and another. It is concluded that a description as accurate as surface observations but with considerably better resolution was achieved.

The most difficult performance to assess was that of SAR. Although regular swell patterns were revealed on five of the passes examined it is still not clear from the evidence available if certain wavelengths are selectively imaged while others are suppressed; nor are the limiting conditions of waves and winds to produce imaged wave trains known with certainty. SAR imagery also revealed streaks lying along the wind direction over large areas of the sea surface where the wind strength was in the region of 16-20m/s. From one of the images examined it would appear that the streakiness replaces well-developed swell in the image