Development of a climatology for cirrus cloud ice water content and its application to climate model parameterizations

Clouds are one of the major components that regulate radiative forcing in the atmosphere. Cirrus clouds have been a major focus of research due to their near-global occurrence in a variety of atmospheric conditions and because they have the ability to both trap infrared terrestrial radiation and to reflect solar radiation. Although numerous studies of cirrus clouds have taken place, it is not currently well understood how to best parameterize their microphysical properties in climate models to accurately portray their radiative effects. More specifically, the ice water content (IWC) of cirrus clouds is of particular interest because it is commonly used to parameterize cloud properties in climate models as well as to describe the role of cirrus in water transport and chemistry.

This study focuses on building an IWC climatology spanning all latitudes for use in determining an accurate parameterization scheme for cirrus clouds in climate models for all regions in all weather conditions. The recent work performed by one of us has put in place the initial steps for building this climatology, but additional datasets have been incorporated here to develop a more comprehensive picture. This presentation will feature a discussion of the datasets and analysis techniques being used and an illustration of the results thus far detailing the relationship between IWC and temperature at various latitudes. There will also be a discussion of the next steps in this study, which include a reanalysis of the data in terms of the cloud formation mechanism to add yet another level of refinement and a comparison between current parameterization schemes of cirrus clouds in the literature to the in situ measurements of the climatology.