Detection of Daytime Arctic Clouds using MISR and MODIS Data

Amongst the 36 spectral radiances available on the Moderate Resolution Imaging Spectroradiometer (MODIS) seven of them are used operationally for detection of clouds in daytime polar regions. While the information content of clouds inherent in spectral radiances is familiar, the information content of clouds contained in angular radiances (i.e., radiances emanating to space from the same object but in different directions) is not. The Multi-angle Imaging Spectroradiometer (MISR) measures angular radiances to space and its collocation on the NASA Terra satellite with MODIS allows for a comparative analysis of its cloud detection capabilities with those of MODIS. Expert labels from an extensive amount of data are used to compare arctic cloud detection efficiencies of several methods based on MISR radiances and radiance-based features, MODIS radiances and radiance-based features, and their combinations. The accuracy of cloud detections is evaluated relative to 2.685 million 1.1-km resolution expert labels applied to 3.946 million pixels with valid radiances from 32 scenes that contain both clear and cloudy pixels. Fisher’s quadratic discriminate analysis (QDA) with expert labels is applied to MISR radiances, MISR radiance-based features, MODIS radiances, and MODIS radiance-based features. The resulting classification accuracies are 87.51%, 88.45%, 96.43%, and 95.61%, respectively. The accuracies increase to 96.98% (96.71%) when QDA with expert labels is applied to combined radiances (features) from both MISR and MODIS. These results are indicative of the information content inherent in spectral and angular radiances, but these classifiers are impossible Department of Statistics, The Ohio State University, Columbus, OH 43210-1247. Email: [email protected] Department of Meteorology, Pennsylvania State University, University Park, PA 16802. Email: [email protected] Department of Statistics, University of California, Berkeley, CA 94720-3860. Email: [email protected] Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099. Email: [email protected] Department of Energy, Southern Great Plains Site, 309600 EW 28, Billings, OK 74630. Email: d [email protected]