Ocean Reflectance Observed During CLAMS

The Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) field campaign focused on validating Terra EOS data products. CLAMS was sponsored by CERES, MISR, MODIS-Atmospheres and the NASA/GEWEX Global Aerosol Climatology Project (GACP). The centerpiece of CLAMS is the Chesapeake lighthouse sea platform 20 km east of Virginia Beach, at which NASA and NOAA make continuous, long-term measurements of radiation, meteorology, and ocean waves. CLAMS is a shortwave closure experiment and one of its objectives is to characterize the ocean optics in the vicinity of the lighthouse. The Schulz multi-wavelength spectral-photometer SP1A was deployed at the Chesapeake lighthouse to measure the upwelling radiances. SP1A scanned about 150 degrees of azimuth around sunglint area at 11 elevation angles: 2, 4, 7, 12, 22, 32, 42, 52, 62, 72 and 90 degrees. The Cloud Absorption Radiometer (CAR) is a multi-wavelength scanning radiometer mounted on University of Washington's aircraft Convair-580 to measure the bi-directional reflectance of ocean surface under different sun angles and wind conditions. CAR measured upwelling radiances at Chesapeake lighthouse as well as at nearby buoys. Radiances measured by both SP1A and CAR were converted to spectral reflectances. The observed spectral reflectance distributions of SP1A (mounted on the lighthouse platform) and CAR (airborne) were compared with the "6S" (Second Simulation of Satellite Signal in the Solar Spectrum) model simulated reflectance distributions. 6S is a radiative transfer model based on the successive orders of scattering and uses the Cox-Munk distribution of wave slopes to parameterize the effect of wind on reflection by the sea. Reflectances produced by CAR at two remote NOAA ocean buoys were compared to the 6S simulated reflectances.