The detection and characterization of cirrus cloud properties from simulated and observed high-spectral-resolution infrared radiances

Cirrus clouds are an important component of the climate system, although the precise role of how they interact with solar and terrestrial radiation, and with the thermodynamic and dynamic aspects of the atmosphere is still uncertain. Much of the uncertainty lies in the fact that until recently, there has been a lack of global observations of cirrus from satellite platforms. In this dissertation, the sensitivity of space-borne high-resolution IR radiances to cirrus cloud properties is addressed.; The Atmospheric Infrared Sounder (AIRS) data was analyzed for the purpose of studying cirrus clouds. In parallel, an effort was made to simulate cirrus for high-resolution near-nadir IR measurements. Simulated cirrus are fit to observations of cirrus in the AIRS data set for some case studies. The simulated radiances were further used to understand how sensitive AIRS-like radiances are to particular physical quantities, such as IWP, particle size, particle size distribution and particle shape characteristics, T(z) and RH(z) profiles, and cloud thickness and height, among others. Principal component analysis (PCA) was used to diagnose the variability in the IR spectra due to individual physical quantities, and then for particular combinations of physical quantities. Some physical quantities can be discerned apart from others in particular instances, but for other quantities and other instances this was not the case. This emphasizes the need for other space-borne data sources to constrain the solution space when retrieving cirrus properties.; Before cirrus properties can be retrieved however, cirrus must be identified in a measurement. With the existence of the combined Advanced Microwave Sounding Unit (AMSU) and Atmospheric Infrared Sounder (AIRS) measurements, we used the total column water vapor measurements to constrain the effect of the water vapor continuum on AIRS radiances in the presence of clouds. Simulations showed that the sensitivity of this detection technique to the presence of cirrus occurs for an optical depth of 0.1 or less, with much room for improvement.; This work has provided new insight on measurement capabilities using high-resolution IR radiance measurements, and has provided the foundation for retrievals of cirrus properties over very large sets of AIRS data.