Radar measurements at 16.5 GHz in the oceanic evaporation duct

A series of radar measurements is presented that demonstrates that a 16.5-GHz radar, located at typical shipboard antenna heights, can effectively utilize the existence of the oceanic evaporation duct to achieve surface ship detection ranges of more than twice the standard horizon range. Observations of surface targets of opportunity made at two sites on the US Pacific coast from July 1984 through January 1986 agree with predictions from a simple propagation model. This model combines a single-mode waveguide approximation with a model of the surface target's radar cross-section distribution to determine the maximum radar detection range for various evaporation duct heights. A frequency distribution of predicted detection range is given, based on the evaporation duct climatology for two locations. Although the radar measurements and the predictions are for a specific frequency, it is thought to be highly probable that the model can be extended to predict the performance of surface-search radars operating at other frequencies and in other areas of the ocean