Application of Observations from the COVE Sea Platform, CLAMS Aircraft Campaign, and CERES on Terra to Determine an Accurate Shortwave Budget for the Atmosphere in Cloud-free Conditions

We compute the Surface and Atmospheric Radiation Budget (SARB - or vertical profile of fluxes) for shortwave (SW) under clear skies using photometer-based observations of aerosol optical thickness (AOT) and validate with observed fluxes at both the top and bottom of the column. Because of the inherently large noise in converting instantaneous satellite-observed radiances (Wm-2sr-1) to flux (Wm-2), closure at TOA requires a time series of significant length. And validating such a result at the column bottom would be problematic over land, where surface inhomogeneity sorely limits the spatial representativeness of any ground-based, point measurement of the upwelling and net SW. Hence at the surface we focus on the CERES Ocean Validation Experiment (COVE) sea platform (25km due east of Virginia Beach), which has continuous measurements of upwelling and downwelling fluxes, AOT, meteorology, and ocean waves. The Chesapeake Lighthouse and Aircraft Measurement for Satellites (CLAMS - 10 July to 3 August 2001) field campaign specifically targeted the COVE sea platform to establish minor adjustments that must be made to account for local obstructions. Surface spectral albedos were generated by the Jin-Stamnes coupled air-sea radiative transfer model, which accounts for scattering and absorption in both media explicitly; inputs include AOT, surface wind and precipitable water (measured at COVE), and chlorophyll concentration (estimated using both in situ data from the Chesapeake Bay and SeaWiFS). Simulated broadband albedos were compared with COVE observations for the afternoon clear sky conditions obtained during an entire year (3/1, 2000 to 3/1, 2001); mean differences are within 0.01; but observations are higher, suggesting that additional sediments or bubbles should be included in the code. We report further calculations using the Jin-Stamnes albedo and the Fu-Liou radiation code for the CLAMS period, comparing with fluxes observed at the surface by COVE, at altitude by aircraft, and at TOA by a CERES scanner specially programmed to target COVE; and close on the elusive aerosol forcing to atmospheric absorption.