Evaluation of COAMPS boundary layer refractivity forecast accuracy for 2–40 GHz electromagnetic wave propagation

In this paper, the performance of the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS¯) electromagnetic (EM) propagation forecast is assessed using numerous metrics such as forecast lengths, frequencies, ranges, and spatial resolutions. The modeled PL (Propagation Loss) for 2–40 GHz based on the COAMPS¯ predicted refractivity profiles is evaluated by 1 month of range-dependent measurements, which were collected during Coupled Air-Sea Processes and Electromagnetic ducting Research (CASPER) East Campaign. PL data were collected using a shore-to-ship radio link, near the coast of Duck, NC. Mesoscale atmospheric refractivity predictions for the CASPER East operational area are provided by COAMPS¯. Propagation loss predictions are computed from these refractivity profiles via a parabolic wave equation propagation code. The results show a good agreement between the COAMPS¯-predicted and the measured propagation loss for the northwest Atlantic region. The analyses show that the prediction error varies from 3 to 8 dB as the frequency increases from 2 to 40 GHz. In addition, COAMPS¯ successfully tracked the changes in the refractivity field even when the forecast length increased from 0 to 48 hr, with only a marginal degradation in EM prediction accuracy within the first 12 hr. Higher horizontal range resolution does not result in significant improvement in EM predictions as long as there are at least 2 M-profiles that allows the EM propagation code to capture the first order horizontal variation. Low-resolution, high order nested COAMPS¯ fields still produce good EM forecasts for this particular geometry.