Open AccessSimulations of Arctic mixed‐phase clouds in forecasts with CAM3 and AM2 for M‐PACE
Author(s) -
Xie Shaocheng,
Boyle James,
Klein Stephen A.,
Liu Xiaohong,
Ghan Steven
Publication year - 2008
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007jd009225
Subject(s) - cloud fraction , meteorology , longwave , environmental science , boundary layer , cloud physics , cloud computing , radiative transfer , liquid water content , atmospheric model , cloud top , atmosphere (unit) , planetary boundary layer , atmospheric sciences , cloud cover , physics , computer science , mechanics , optics , operating system
Simulations of mixed‐phase clouds in forecasts with the NCAR Atmosphere Model version 3 (CAM3) and the GFDL Atmospheric Model version 2 (AM2) for the Mixed‐Phase Arctic Cloud Experiment (M‐PACE) are performed using analysis data from numerical weather prediction centers. CAM3 significantly underestimates the observed boundary layer mixed‐phase cloud fraction and cannot realistically simulate the variations of liquid water fraction with temperature and cloud height due to its oversimplified cloud microphysical scheme. In contrast, AM2 reasonably reproduces the observed boundary layer cloud fraction while its clouds contain much less cloud condensate than CAM3 and the observations. The simulation of the boundary layer mixed‐phase clouds and their microphysical properties is considerably improved in CAM3 when a new physically based cloud microphysical scheme is used (CAM3LIU). The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes. Sensitivity tests show that these results are not sensitive to the analysis data used for model initialization. Increasing model horizontal resolution helps capture the subgrid‐scale features in Arctic frontal clouds but does not help improve the simulation of the single‐layer boundary layer clouds. AM2 simulated cloud fraction and LWP are sensitive to the change in cloud ice number concentrations used in the Wegener‐Bergeron‐Findeisen process while CAM3LIU only shows moderate sensitivity in its cloud fields to this change. This paper shows that the Wegener‐Bergeron‐Findeisen process is important for these models to correctly simulate the observed features of mixed‐phase clouds.