Evaluating aerosol/cloud/radiation process parameterizations with single-column models and Second Aerosol Characterization Experiment (ACE-2) cloudy column observations

摘要: [1] The Second Aerosol Characterization Experiment (ACE-2) data set along with ECMWF reanalysis meteorological fields provided the basis for single column model (SCM) simulations, performed as part of PACE (Parameterization Indirect Climatic Effect) project. Six different SCMs were used to simulate ACE-2 case studies clean and polluted cloudy boundary layers, objective being identify limitations aerosol/cloud/radiation interaction schemes within range uncertainty in situ, satellite retrieved data. The exercise proceeds three steps. First, are configured same fine vertical resolution situ base evaluate numerical prediction aerosol activation, radiative transfer precipitation formation. Second, test is at coarser GCMs its impact on performance parameterizations. Finally, run a 24–48 hr period examine predictions layer clouds when initialized large-scale fields. Several tested cloud droplet number concentration (N). Physically based activation using velocity show noticeable discrepancies compared empirical due biases diagnosed velocity. Prognostic exhibit larger variability than diagnostic ones, coupling between drizzle scavenging calculation N. When locally observed profiles liquid water, predicted optical properties comparable observations. Predictions however degrade more sensitive mean water path spatial heterogeneity. Predicted fluxes severely underestimated improve accounting sub-grid variability. Results from runs suggest that most models have problems simulating morphology, since initialization do not accurately reproduce conditions. As result, significantly overestimate properties. Improved morphologies obtained subgrid inversions thickness schemes. This may be result representing scale effects though we rule out possibility better large-forcing also morphology predictions.