Retrievals of daytime and nighttime cloud macro- and micro-physical properties using infrared satellite observations

Proper characterization of cloud macro- and micro-physical properties such as cloud top height, optical depth, effective particle size, and ice/liquid water path is imperative for an understanding of cloud processes and for an accurate characterization of the role of clouds in the Earth's radiation budget. Scientists at NASA Langley Research Center retrieve daytime and nighttime cloud properties from passive satellite observations using a legacy algorithm that was developed for the CERES (Clouds and the Earth's Radiant Energy System) program. This algorithm has been applied to data from a variety of geostationary and low earth orbiting satellites, including GOES, AVHRR, MODIS, MTSAT and MSG. Cloud optical properties may be retrieved from passive infrared satellite observations using the Shortwave-infrared Infrared Split-window Technique (SIST), which is particularly useful when the solar zenith angle is high. Additionally, this technique may be applied during the daytime, for retrievals of high, optically thin clouds such as contrails. The SIST technique may also be useful for documenting the life cycle of contrails, which, depending on the atmospheric conditions in the upper troposphere, can evolve from narrow linear features into broader areas of more uniform cirrus. These clouds can have a significant effect on the Earth's radiation budget, and their frequency is projected to increase along with increasing global air traffic. This paper documents the ongoing work underway at NASA Langley to use the SIST technique for a variety of climate applications, including contrail cloud property retrievals and cloud property retrievals at night.