Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 7, 463-478, 2014
© Author(s) 2014. This work is distributed
under the Creative Commons Attribution 3.0 License.
Model description paper
04 Mar 2014
On the analytic approximation of bulk collision rates of non-spherical hydrometeors
A. Seifert1, U. Blahak2, and R. Buhr3,4 1Hans-Ertel Centre for Weather Research, Deutscher Wetterdienst, Hamburg, Germany
2Deutscher Wetterdienst, Offenbach, Germany
3Universität Hamburg, Hamburg, Germany
4Max Planck Institute for Meteorology, Hamburg, Germany
Abstract. Analytic approximations of the binary collision rates of hydrometeors are derived for use in bulk microphysical parameterizations. Special attention is given to non-spherical hydrometeors like raindrops and snowflakes. The terminal fall velocity of these particles cannot be sufficiently well approximated by power-law relations which are used in most microphysical parameterizations, and therefore an improved formulation is needed. The analytic approximations of the bulk collision rates given in this paper are an alternative to look-up tables and can replace the Wisner approximation, which is used in many atmospheric models.

Citation: Seifert, A., Blahak, U., and Buhr, R.: On the analytic approximation of bulk collision rates of non-spherical hydrometeors, Geosci. Model Dev., 7, 463-478, doi:10.5194/gmd-7-463-2014, 2014.
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