The inclusion of water with the injected aerosol reduces the simulated effectiveness of marine cloud brightening

Abstract

Sea-salt aerosols proposed for injection in marine cloud brightening geoengineering would likely result from evaporation of sea-water droplets. Previous simulations have omitted this mechanism. Using the WRF/Chem model (Weather Research and Forecasting model coupled with Chemistry) in large-eddy simulation mode, we find that droplet evaporation creates cold pools, suppressing initial aerosol plume heights by up to 30% (40m). This lessens cloud albedo increases from 94.1 to 88.5% in our weakly-precipitating case and from 4.3 to 1.4% for daytime injection into our nonprecipitating case (cloud albedo differences of 0.012 and 0.009, respectively). Inclusion of this effect in future modelling would allow increasingly realistic effectiveness estimates. © 2013 Royal Meteorological Society.