Microwave and infrared propagation over the sea during the rough evaporation duct (RED) experiment

The RED experiment was conducted offshore of the Hawaiian island of Oahu in late summer, mid-August to mid-September, of 2001. The research platform floating instrument platform (R/P FLIP), moored about 10 km off of the NE coast of Oahu, hosted the primary meteorological sensor suites and served as the terminus for the propagation link. Two meteorological buoys provided additional support. One buoy was located approximately 5 km west of R/P FLIP and the other was located approximately 15 km south, nearly mid-path on the microwave propagation link. Wind speed never exceeded 12 ms^-1. Significant wave height and wave age rarely exceeded 2.5 m and 1 respectively. The microwave data were analyzed by comparing the observed signal levels to modeled results using observed meteorological data. Very good agreement is found with standard deviations of the differences ranging from 2 dB to 4 dB. Examination of the infrared data set reveals an unexpectedly weak transmission signal. The data analysis effort includes the influence of geometrical considerations (including the large 54-degree pointing excursions of the source on R/P FLIP); extinction (absorption and scattering by aerosols and molecules); and refractive effects induced by the long near-surface propagation path. However, with the low winds and wave heights observed during RED, the effects of surface waves are not readily isolated.