FIGURE 4.8: The top panel shows a true color image from the MODIS instrument taken over the Atlantic Ocean on January 27, 2003. Bright linear features are apparent in the low clouds in much of the scene. MODIS can independently measure the optical depth (lower left panel), which is enhanced in the bright regions, and the effective particle radius (lower right panel). The smaller particle radius in the ship tracks is what would be expected from the introduction of many more cloud condensation nuclei from the ship exhaust. Smaller particles are more effective in reflecting solar radiation. This strongly suggests that the cloud enhancements are caused by human-produced aerosols.

SOURCE: Images courtesy of Jacques Descloitres, MODIS Land Rapid Response Team, and Mark Gray, MODIS Atmosphere Science Team, both at NASA Goddard Space Flight Center, http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=11271.