For more information on distinguishing clouds from snow on the ground, click the link at the bottom of this page. This link will open "Remote Sensing of the Land, Oceans, and Atmosphere with MODIS," a Webcast that details the capabilities of the MODIS instrument on the Aqua and Terra satellites. The Webcast will open to the section entitled "Cloud Mask," which describes techniques used to separate clouds from other phenomena using the MODIS channels. Please click the "Cloud Mask" title from the menu bar on the left. Make sure to view the looped images (they are bigger than the examples on the page), and go through the cloud mask algorithm to see how different channels respond to both clouds and ground features.