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2B-CWC-RVOD 008 issue
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Multi-phase cloud columns
03/24/09 1:18 pm
The 2B-CWC-RVOD algorithm has separate retrievals for liquid and ice clouds; the current algorithm does not attempt to retrieve both solid and liquid microphysical properties simultaneously in the same cloud column. Instead, separate retrievals are performed assuming that the entire cloud column is liquid-only and ice-only, and the two sets of results are combined into a composite profile according to a simple temperature relation (since we do not have an independent source of phase information). Ice-phase results are used for cold temperatures, liquid-phase results for warm temperatures, and a linear combination of the two are used in an intermediate temperature range, yielding an approximate mixed-phase solution.
Note that one consequence of this retrieval approach is that, for the case of ice cloud overlying lower liquid cloud, the liquid-phase retrieval most likely overestimates the amount of attenuation of the radar beam in the column above the liquid layers. Future versions of the algorithm will likely take more sophisticated approaches to handling cloud columns with multiple phases, and will address the attenuation issue.
The composite profile variable names all begin with "RVOD_"; the separate liquid-only and ice-only retrieval variable names begin with "LO_RVOD_" and "IO_RVOD_", respectively.
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