Uncertainty in Radar Performance Due to Evaporation Ducting

Spatial and temporal variations in evaporation ducting conditions can have significant impacts on electromagnetic (EM) propagation, and the performance (e.g. detection range) of a shipborne radar may depend strongly on the ducting environment. In order to provide context to previous studies of ducting climatology, it is essential to relate the variability in ducting conditions to radar performance.

In this study, we used the Climate Forecast System Reanalysis (CFSR) climatological database to extract the Evaporation Duct Height (EDH) and other relevant weather variables in the South China Sea, and calculated the resulting radar performance expected from these environmental conditions. We first analyze the diurnal and seasonal variations in EDH, and observe larger variability and higher EDHs in littoral regions than in the open water. However, we find that the relatively small variations in EDH that are typical in the open water of the South China Sea can still strongly impact the detection range of a 10 GHz (X-band) shipborne radar. In addition, we demonstrate how radar performance prediction may be impacted by measurement error in the sea surface parameters, used to model evaporation ducts.