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Minimalist model of ice microphysics in mixed‐phase stratiform clouds
Author(s) -
Yang Fan,
Ovchinnikov Mikhail,
Shaw Raymond A.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50700
Subject(s) - ice nucleus , ice crystals , power law , sea ice growth processes , supercooling , clear ice , nucleation , ice cloud , atmospheric sciences , liquid water content , meteorology , environmental science , cloud computing , geology , sea ice , physics , thermodynamics , arctic ice pack , sea ice thickness , law , antarctic sea ice , mathematics , statistics , political science
The question of whether persistent ice crystal precipitation from supercooled layer clouds can be explained by time‐dependent, stochastic ice nucleation is explored using an approximate, analytical model and a large‐eddy simulation (LES) cloud model. The updraft velocity in the cloud defines an accumulation zone, where small ice particles cannot fall out until they are large enough, which will increase the residence time of ice particles in the cloud. Ice particles reach a quasi‐steady state between growth by vapor deposition and fall speed at cloud base. The analytical model predicts that ice water content ( w i ) has a 2.5 power‐law relationship with ice number concentration ( n i ). w i and n i from a LES cloud model with stochastic ice nucleation confirm the 2.5 power‐law relationship, and initial indications of the scaling law are observed in data from the Indirect and Semi‐Direct Aerosol Campaign. The prefactor of the power law is proportional to the ice nucleation rate and therefore provides a quantitative link to observations of ice microphysical properties.