Surface Bidirectional Reflectance Functions Derived from CERES Helicopter Data Over the Arm Southern Great Plains Site

Bidirectional reflectance distribution functions (BRDFs) are essential for deriving albedos from radiances measured by satellites to estimate the observed global energy balance and for predicting the radiance field for a given set of conditions. BRDFs were derived from data taken by the helicopter-based Clouds and the Earth's Radiant Energy System (CERES) Airborne Radiometer Scanner (ARS; Wheeler et al. 1997) system over a variety of surface types around the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site during August 1998. Data were taken at low altitudes for solar zenith angles ranging from 23° to 90°. The ARS contains the FieldSpec FR spectroradiometer with spectral sampling from 0.35 to 2.5 μm. The BRDFs were computed using clear-sky data in spectral intervals corresponding to channels on several new satellite imagers. The results are compared for variability with wavelength and surface type. The reflectances were corrected to the top of the atmosphere (TOA) for use with satellite data. These results should help improve the accuracy of satellite-derived cloud and surface radiative properties.


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