Wednesday, 17 October 2001
Daytime Cloud Overlap using MODIS Data
We will demonstrate a method to detect MODIS (Moderate Resolution Imaging Spectroradiometer) pixels that potentially contain thin cirrus overlying lower-level water clouds. The MODIS is a 36 band imager aboard the polar-orbiting NASA Terra platform. Our approach is suitable for daytime imagery and utilizes the 1.63 µ m band reflectance, and the 8.5 and 11 µ m band brightness temperatures. Central to our operational scheme is the use of the MODIS infrared cloud thermodynamic phase retrieval method to determine ice and water pixels and the MODIS cloud mask to determine clear sky pixels. We will present results from the application of radiative transfer theory that form the basis for our analysis approach. The methodology for the detection of cloud overlap will be highlighted with examples from daytime MODIS imagery. We will support the interpretation of our satellite-based analysis with surface-based radar and lidar data collected at the ARM Clouds and Radiation Testbed (CART) Southern Great Plains site in Oklahoma.
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