CIRRUS LAYER MICROPHYSICAL PROPERTIES DERIVED FROM SURFACE-BASED MILLIMETER RADAR AND INFRARED INTERFEROMETER DATA

Observational data regarding the properties of cirrus clouds are neede d to aid in the development of accurate, physically based parameteriza tions in climate models. The Atmospheric Radiation Measurement (ARM) p rogram, sponsored by the U.S. Department of Energy, is providing conti nuous observations of cirrus clouds with a suite of instrumentation at several locales. In this paper, we describe an algorithm to derive th e microphysical properties of optically thin cirrus clouds. This algor ithm uses radar reflectivity and infrared emission spectra from an int erferometer and is tailored for the specific instruments at the ARM si tes. We present in situ validation of the technique and examine a cirr us case study to illustrate the sensitivity of the algorithm. In the c ase study, solar fluxes calculated from the retrieved microphysical pa rameters are compared to observed fluxes to build confidence in the al gorithm results. Comparison of the retrieved quantities to microphysic al parameters retrieved from satellite data is also presented.