PNNL

Most global climate models cannot resolve important aerosol processes related to clouds that occur at cloud scale (1 kilometer). This makes it difficult to predict aerosol changes and aerosol effects on climate, as up to now MMF has treated aerosol processes only on a coarse GCM grid. A promising tool to address this challenge is a new MMF that embeds a cloud resolving model (CRM) into each GCM grid column to resolve cloud processes.  

In this study, researchers developed the first global model explicitly representing aerosol processes at cloud scale (in each CRM grid cell) within the MMF. For remote regions, the explicit aerosol treatments produced a significant increase — up to 40 percent — in the amount of black carbon (BC), primary organic aerosol, and sulfate and a nearly equal decrease of the sea-salt aerosol burdens. These results were due to differences in aerosol convective transport and wet removal between the two models. The new model also showed reduced bias of BC surface concentration in North America and BC vertical profiles in the high latitudes. However, the tendency toward high BC concentrations in the upper troposphere over the remote Pacific regions remained, indicating further improvements are needed on other physical process representations.