"Inverse" estimates (i.e., aerosol forcings inferred from the observed global warming) are hampered by the uncertainty about climate sensitivity. Biases in modeled cloud fields, limited process representation, missing aerosol-cloud interaction processes, and uncertainties in the unperturbed aerosol distribution are the main sources of uncertainties for simulated aerosol forcings ("forward" estimates). Key cloud aspects necessary for a realistic representation of aerosol-cloud interactions in large-scale models are the distribution of cloud albedo, boundary layer moisture budget, subgrid-scale variability of moisture and vertical updraft velocity, as well as ice crystal nucleation and mixed-phase cloud microphysical processes. In general, the quantification of perturbations of cloud properties by anthropogenic aerosols in large-scale models is highly dependent on the formulation of the cloud process representations.

0 0

Post a comment