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Bulk microphysics parametrization of ice fraction for application in climate models
Author(s) -
Boudala Faisal S.,
Isaac George A.
Publication year - 2006
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/qj.05.04
Subject(s) - parametrization (atmospheric modeling) , ice crystals , cloud physics , atmospheric sciences , environmental science , ice cloud , particle (ecology) , meteorology , cloud computing , geology , physics , radiative transfer , oceanography , quantum mechanics , computer science , operating system
Using in situ aircraft measurements of cloud microphysical properties collected in extratropical stratiform clouds during several field programs, a parametrization of the ice‐particle spectrum that includes small ice particles has been developed. This parametrization has been tested using a single prognostic equation developed by Tremblay et al. (1996) for application in a regional model. The addition of small ice‐particles significantly increases the vapour deposition‐rate when the natural atmosphere is assumed to be water saturated, and thus enhances the glaciation of simulated mixed‐phase cloud via the Bergeron–Findeisen process without significantly affecting the other cloud microphysical processes such as riming and particle‐sedimentation rates. After the water vapour pressure in mixed‐phase cloud was modified, based on the scheme of Lord et al. (1984), by weighting the saturation water vapour pressure with ice fraction, it was possible to simulate a more stable mixed‐phase cloud. It was also noted that the ice‐particle concentration (maximum dimension L > 100 µm ) in mixed‐phase cloud is lower on average by a factor of three, and, consequently, the parametrization should be corrected for this effect. After accounting for this effect, the parametrized ice‐fraction agreed well with observation. Copyright © 2006 Royal Meteorological Society