Session 3.1 Comparison of angular dependence of observed and simulated distributions of radiances over stratocumulus clouds

Monday, 10 July 2006: 1:30 PM
Hall of Ideas G-J (Monona Terrace Community and Convention Center)
Mikhail Ovchinnikov, PNNL, Richland, WA; and R. T. Marchand

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In a case study of continental stratocumulus, a three-dimensional radiative transfer model is applied to synthetic cloud properties generated by a high-resolution cloud model in order to simulate top of the atmosphere radiances. These radiances are compared to observations from the airborne version of the Multi-angle Imaging Spectroradiometer (AirMISR) flown on NASA?s ER-2 aircraft. Radiance distributions for the blue channel are simulated and analyzed for all nine MISR cameras, thus, subjecting the modeled cloud structure to a much more stringent test than in previous studies. Simulations match well the blue channel radiance distributions at oblique view angles but overestimate the minimum in reflectance at the near nadir viewing angles. The model reproduces correctly the angular changes in the width of radiance distribution, as measured by the standard deviation, but the skewnesses of these distributions are captured only qualitatively. The model biases are suggestive of the simulated cloud boundaries being too sharp, the distribution of the vertical liquid water path being too narrow, and the modeled cloud top being too smooth, even in the highest 25-m resolution simulations.
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