The impact of aerosol on cloud water
a heuristic perspective
Fabian Hoffmann (Ludwig Maximilians University)
Franziska Glassmeier (TU Delft - Atmospheric Remote Sensing)
Graham Feingold (National Oceanic and Atmospheric Administration)
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Abstract
Aerosol–cloud interactions modulate the role of clouds in Earth's climate. We derive, evaluate, and apply a simple model to understand aerosol-mediated cloud water adjustments in stratocumulus based on only two prognostic equations for the integrated cloud water L and droplet number concentration N. The model is solved numerically and analytically and agrees well with documented large-eddy-simulation data and satellite retrievals. A tight relationship between adjustments at low and high N is found, revealing the influence of non-precipitation processes (primarily entrainment) on adjustments in precipitating clouds. Furthermore, it is shown that adjustments in non-precipitating clouds tend to be positively biased by external L or N perturbations, while adjustments in precipitating clouds are barely susceptible. By deliberately reducing the complexity of the underlying system, this study constitutes a way forward to facilitate process-level understanding of cloud water adjustments.