Extraction of ocean wave height and dominant wavelength from Geos 3 altimeter data

Abstract

The Geos 3 satellite radar altimeter has the capability to provide accurate, low‐noise measurements of the significant wave height of ocean waves through their effect on the shape of the return pulse. When the amplitude and timing biases are removed from the Geos 3 sample and hold (SH) gates, the mean return wave forms can be excellently fitted with a theoretical template which represents the convolution of the radar point target response, the range noise (jitter) in the altimeter tracking loop, the sea surface height distribution, and the antenna pattern as a function of the range to mean sea level. In computing the wave height, tracking loop jitter may be removed by realigning the SH gates to their actual positions with respect to mean sea level before averaging, by using the observed standard deviation on the altitude measurement to remove the integrated effect of the tracking loop jitter, or by using a lookup table to correct for the expected value of range noise. Analysis of skewness in the Geos return wave form demonstrates the potential of a satellite radar altimeter to determine the dominant wavelength of ocean waves. When the jitter in the Geos range tracker is large, a significant reduction in range noise can be achieved through reprocessing the data. However, when the tracker noise is small, only marginal improvement is possible.