Photo Above : Polar stratospheric clouds near Sweden
High thin clouds are difficult to detect from space. The first comprehensive climatology of thin clouds has been developed with the HIRDLS limb viewing infrared radiometer.
The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) was launched in 2006 and also sees thin clouds.
Tropical thin cirrus that are found in the upper troposphere and lower stratosphere play an important role in climate change and help control the amount of water vapor in the stratosphere.
Polar Stratospheric Clouds (PSCs), key players in spring polar ozone depletion, occur in both hemispheres. The figure on the right below shows the 2006 northern hemisphere winter cloud extinction from HIRDLS. PSCs are seen in the stratosphere at high northern latitudes.
HIRDLS and CALIPSO see the same pattern for the occurrence of clouds. This cloud pattern corresponds with the pattern of relative humidity (RHI) derived from MLS.