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A Continuous Initial Estimate of Cloud Microphysical Structure Using Surface-Based Remote Sensors and Parameterized Microphysics

Miller, M.A. and Johnson, K.L., Brookhaven National Laboratory
Twelfth Atmospheric Radiation Measurement (ARM) Science Team Meeting

Realistic heating rate profiles require an accurate and continuous accounting of cloud microphysical structure. To date, several highly constrained microphysical retrieval algorithms have been designed that operate on specific cloud systems. These algorithms are sufficiently specialized that they are generally applicable in a relatively narrow range of conditions. When these conditions are satisfied, heating profiles can be computed. While it may be possible to link several of these specialized algorithms to produce a semi-continuous description of cloud microphysical structure, there are no existing microphysical retrieval algorithms for many of the cloud types and conditions encountered. Another problem with the use of multiple specialized algorithms is that the modeling community must understand the caveats of each procedure in order to understand how the data are to be used to evaluate models. A possible alternative to the linking of several independent schemes is to produce a continuous "initial-estimate" scheme that uses information about the cloud boundaries and radar reflectivity along with parameterized microphysics. This "initial-estimate" scheme can be used to fill gaps between applications of condition-dependent algorithms or as a stand-alone retrieval package. In this poster, we present results from an attempt to produce this "initial-estimate" microphysical retrieval scheme. In addition to the cloud boundary and radar reflectivity information, the scheme uses sounding data to identify the freezing level. Warm, liquid clouds are handled with a modified version of Chin et al., 1999, which accounts for sub-adiabatic liquid water content. Ice clouds are handled by converting radar refectivity to ice-water content (Liao and Sassen, 1994) and using parameterized microphysics (Ivanova et al., 2002). Mixed-phase clouds are parameterized by assuming that the radar echo is primarily the result of ice. Liquid is added on the basis of a subjective analysis of the temporal variability of radar reflectivity.

Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).