Dessler, AE, Yang, P (2003). The distribution of tropical thin cirrus clouds inferred from terra MODIS data. JOURNAL OF CLIMATE, 16(8), 1241-1247.
Thin cirrus clouds (with optical depths tau much less than 1) play a potentially important role in the earth's atmosphere. However, their tenuous nature makes them difficult to detect, and as a result there are few quantitative, global analyses of them. The Moderate Resolution Imaging Spectrometer ( MODIS) on board the Terra satellite has a channel at 1.375 mum that is specifically designed to detect these clouds, and can measure optical depths as low as 0.02 with an uncertainty factor of 2. During two 3-day periods from December 2000 and June 2001, about one-third of the pixels flagged as cloud free by the MODIS cloud mask are shown to contain detectible thin cirrus. These thin cirrus generally have optical depths below -0.05 and appear with greater frequency and optical depth near deep convection.