Clear skies on April 11, 2004 (top panels) contrast strongly with the dust storm that swept across Iraq and Saudi Arabia on May 13 (bottom panels). These data products from the Multi-angle Imaging SpectroRadiometer (MISR) depict both the abundance of airborne dust, and its height above the surface.
The natural-color views at left were captured by MISR’s 70° forward-pointing camera. In the May 13 image, the dust appears as yellowish ripples that obscure a large part of southern Iraq. The dust is easy to discern over the dark waters of the teardrop-shaped Lake Tharthar, and completely obscures the smaller Lake Razzaza. Automated processing of data from multiple MISR cameras was utilized to generate the cloud and dust height fields (center) and aerosol optical depth retrievals (right).
On May 13, in the areas where the dust exhibited sufficient spatial contrast between several view angles to be retrieved by MISR’s stereoscopic feature matching algorithm, analysis of the wind-corrected stereo height field indicates that the tops of the dust attained heights above the surface of almost 2 kilometers. Terrain elevation data are displayed when the stereo matcher determines that a location is not covered by a feature above the surface. For example, the purple areas in the center right-hand portions of the height fields, correspond with the low, flat, valley between the Tigris and the Euphrates Rivers. The retrieved heights shown here are uncorrected for wind effects. The aerosol optical depth retrievals utilize the change in surface brightness and contrast at different view angles to obtain a quantitative measurement of aerosol amount. Here, an optically thick atmosphere is indicated by the green or yellow pixels, and clearer skies are indicated by blue pixels. The standard MISR aerosol retrieval algorithm did not obtain results in places where the dust was too thick to see surface contrast, and these pixels are shown in dark gray.
The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82° north and 82° south latitude.These data products were generated from a portion of the imagery acquired during Terra orbits 22950 and 23416. The MISR Browse Image Viewer provides access to low-resolution true-color versions of these images. The panels cover an area of about 380 kilometers x 704 kilometers, and utilize data from blocks 63 to 67 within World Reference System-2 path 169.
Image courtesy NASA/GSFC/LaRC/JPL, MISR Team. Text by Clare Averill (Raytheon ITSS/JPL).
