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Parameterization of ice fall speeds in midlatitude cirrus: Results from SPartICus
Author(s) -
Mishra Subhashree,
Mitchell David L.,
Turner David D.,
Lawson R. P.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd020602
Subject(s) - cirrus , ice crystals , ice cloud , middle latitudes , atmospheric sciences , particle (ecology) , ice nucleus , meteorology , environmental science , physics , geology , radiative transfer , optics , thermodynamics , nucleation , oceanography
The climate sensitivity predicted in general circulation models can be sensitive to the treatment of the ice particle fall velocity. In this study, the mass‐weighted ice fall speed ( V m ) and the number concentration ice fall speed ( V n ) in midlatitude cirrus clouds are computed from in situ measurements of ice particle area and number concentration made by the two‐dimensional stereo probe during the Small Particles In Cirrus field campaign. For single‐moment ice microphysical schemes, V m and the ice particle size distribution effective diameter D e were parameterized in terms of cloud temperature ( T ) and ice water content (IWC). For two‐moment schemes, V m and V n were related to D e and the mean maximum dimension¯ D , respectively. For single‐moment schemes, although the correlations of V m and D e with T were higher than the correlations of V m and D e with IWC, it is demonstrated that V m and D e are better predicted by using both T and IWC. The parameterization relating V m to T and IWC is compared with another scheme relating V m to T and IWC, with the latter based on millimeter cloud radar measurements. Regarding two‐moment ice microphysical schemes, a strong correlation was found between D e and V m and between¯ D and V n owing to their similar weightings by ice particle mass and number concentration, respectively. Estimating V m from D e makes V m a function of IWC and projected area, realistically coupling V m with both the cloud microphysics and radiative properties.