The use of pyranometers for underwater total radiant energy flux measurements

Heat balance studies of the upper ocean layer require knowledge of the upwelling and downwelling irradiance through depths of interest: this requires an instrument with a flat spectral response. Measurements were made using commercially available pyranometers, but their glass domes produced large immersion errors (≈ 65% reductions) and careful calibrations were made to correct for this and also verify the cosine response of the pyranometers when underwater. Sample data obtained by towing uplooking and downlooking pyranometers on a sled at 5-m depth are given.