A case of thin, warm marine-boundary-layer (MBL) clouds is simulated by acloud-system resolving model (CSRM) and is compared to the same case ofclouds simulated by a general circulation model (GCM). In this study, thesimulation by the CSRM adopts higher resolutions which are generally used inlarge-eddy simulations (LES) and more advanced microphysics as compared tothose by the GCM, enabling the CSRM-simulation to act as a benchmark toassess the simulation by the GCM. Explicitly simulated interactions amongthe surface latent heat (LH) fluxes, buoyancy fluxes, and cloud-topentrainment lead to the deepening-warming decoupling and thereby thetransition from stratiform clouds to cumulus clouds in the CSRM. However, inthe simulation by the GCM, these interactions are not resolved and thus thetransition to cumulus clouds is not simulated. This leads to substantialdifferences in liquid water content (LWC) and radiation between simulationsby the CSRM and the GCM. When stratocumulus clouds are dominant prior to thetransition to cumulus clouds, interactions between supersaturation and clouddroplet number concentration (CDNC) (controlling condensation) and thosebetween rain evaporation and cloud-base instability (controlling clouddynamics and thereby condensation) determine LWC and thus the radiationbudget in the simulation by the CSRM. These interactions result in smallercondensation and thus smaller LWC and reflected solar radiation by clouds inthe simulation by the CSRM than in the simulation by the GCM where theseinteractions are not resolved. The resolved interactions (associated withcondensation and the transition to cumulus clouds) lead to better agreementbetween the CSRM-simulation and observation than that between theGCM-simulation and observation.
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