ESTIMATING THE WAVELENGTH-DEPENDENT OCEAN ALBEDO UNDER CLEAR-SKY CONDITIONS USING NASA ER-2 SPECTRORADIOMETER MEASUREMENTS

The wavelength-dependent albedo along the flight track of a NASA ER 2 high-altitude research aircraft has been estimated under clear-sky con ditions in the 300-775 nm spectral range. We have developed an inversi on technique to estimate ocean albedo which used nadir radiance measur ements obtained during recent ER 2 campaigns. These are used in conjun ction with a multiple-scattering radiative transfer model. This method is general and robust in that any type of surface can be handled as l ong as a functional form for the angular distribution of surface radia nce can be specified. Comparisons have been made against a forward, it erative method and differences do not exceed 1% in the visible and wer e 1-2% in the near UV. Results are presented for clear-sky portions of flights from two ER 2 campaigns. Specular reflection of the sunlight off the ocean surface has been treated using the Cox and Munk statisti cal approach. Following this, the wavelength-dependent albedo has been estimated at selected points along various ER 2 flights. Furthermore. photolysis coefficients (or J values) for NO2 and NO3 have been calcu lated at these points so that the effects of accounting for both specu lar reflection and wavelength dependence on photo chemistry can be ass essed. The use of a wavelength-dependent albedo was found to impact J values by as much as 10%. It was also determined that, in most cases, accounting for specular reflection was found to have a minor impact on J values (1-3%), but under certain conditions, differences of up to 7 % are possible.