Two tests of real-time ocean wave-height mapping with HF skywave radar

An estimate of the coverage efficiency of a high-frequency (HF) skywave (ionospheric) radar for mapping ocean wave height and surface wind direction at ranges between 1000 and 3000 km was made for two different but common operational ocean-monitoring applications. In the first test, three days in duration, wind direction and wave height were mapped over the entire coverage area. In the second test, four days in duration, wind direction was mapped over the entire coverage area and wave height was mapped at preselected small regions within the coverage area. On-line quality assessment and real-time ionospheric diagnostics helped select space-time-frequency windows with low ionospheric distortion. Wind direction over the 4 000 000-km²coverage area was mapped every day with the Wide Aperture Research Facility (WARF) skywave radar in about 1 h. For large-area wave-height mapping, 6 h was allowed, and for the coverage of a smaller grid, 3 h was allowed. Within these time windows, high-confidence wave-height measurements were obtained at 59 percent of the locations attempted, using on-line processing for both tests. When postexperiment processing was included, the coverage efficiency increased to 74 percent. Greater efficiencies would be possible operationally with more experience and more sophisticated radars. Eliminating the First day's results from the statistics shows the effects of increased operating experience. Then the overall on-line efficiency increases to 69 percent, and the off-line increases to 82 percent for the six days of the two tests.