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An analytical expression for predicting the critical radius in the autoconversion parameterization
Author(s) -
Liu Yangang,
Daum Peter H.,
McGraw Robert
Publication year - 2004
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 - 10.1029/2003gl019117
Subject(s) - radius , critical radius , constant (computer programming) , work (physics) , physics , environmental science , mechanics , thermodynamics , computer science , spheres , computer security , astronomy , programming language
An analytical expression for the critical radius associated with Kessler‐type parameterizations of the autoconversion process is derived. The expression can be used to predict the critical radius from the cloud liquid water content and the droplet number concentration, eliminating the need to prescribe the critical radius as an empirical constant in numerical models. Data from stratiform clouds are analyzed, indicating that on average continental clouds have larger critical radii than maritime clouds. This work further suggests that anthropogenic aerosols affect the autoconversion process by increasing the critical radius and decreasing the characteristic radius, which in turn inhibits the initiation of embryonic raindrops, and by decreasing the autoconversion rate after the initiation process. The potential impact of this work on the evaluation of the second indirect aerosol effect is discussed.