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Sensitivity of a continental night‐time stratocumulus‐topped boundary layer to varying environmental conditions
Author(s) -
Leung W.Y. H.,
Savre J.,
Bender F. A.M.,
Komppula M.,
Portin H.,
Romakkaniemi S.,
Sedlar J.,
Noone K.,
Ekman A. M. L.
Publication year - 2016
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 - 10.1002/qj.2877
Subject(s) - liquid water path , drizzle , marine stratocumulus , atmospheric sciences , environmental science , liquid water content , boundary layer , troposphere , moisture , geology , meteorology , cloud computing , precipitation , aerosol , physics , thermodynamics , computer science , operating system
Large‐eddy simulation of a nocturnal stratocumulus‐topped boundary layer in a continental midlatitude environment has been performed to examine the sensitivity of the cloud to a number of different environmental parameters. The simulations showed that the stratocumulus cloud was strongly affected by the presence of an overlying free tropospheric cirrus cloud (FTC), in agreement with previous studies of marine nighttime stratocumulus. When introducing an FTC with an optical thickness of 2, stratocumulus liquid water path decreased by 30%. Enhancing the optical thickness of the FTC to 8 further decreased the liquid water path by almost 10%. The presence of an FTC decreased the cloud‐top radiative cooling which decreased the turbulent mixing in the boundary layer, so that the liquid water content and cloud depth were reduced. The sensitivity of the stratocumulus cloud to an overlying FTC was found to be affected by the moisture content in the free troposphere. When a clear positive or negative moisture gradient above the inversion was imposed, and an overlying FTC with an optical thickness of 8 was introduced, the stratocumulus cloud LWP decreased by more than 40%. Furthermore, the effect of changes in free tropospheric moisture content and an overlying FTC on the stratocumulus cloud properties was found to be nonlinear; the combined response was in general weaker than the two responses added together. The modeled response to changes in cloud condensation nuclei (CCN) concentrations was found to be non‐significant, unless the CCN concentrations were so low that drizzle was induced (∼50 cm −3 ).