Aerosol Impacts on Post-Cold Frontal Cumulus Clouds and the Extratropical Cyclone Moisture Budget

The conceptual model of extratropical cyclones (ETCs) includes a cyclone and warm and cold fronts, with associated patterns of clouds and precipitation. In this study, the focus is on post-cold frontal (PCF) cumulus clouds and their moisture transport. PCF clouds transport moisture from the boundary layer into the free troposphere. Recent studies suggest that this moisture transport could limit available moisture to other regions of the ETC. Studies of PCF cumulus clouds are needed in order to quantify not only their moisture transport, but also their precipitation and radiative roles.

This study makes use of a cloud-resolving model with advanced cloud microphysics to examine PCF cumulus clouds observed during an ETC case study. Using the Regional Atmospheric Modeling System (RAMS), an ETC case is simulated at high resolution and with bin-emulating two-moment bulk microphysics, in order to examine PCF cumulus cloud microphysical and dynamical characteristics, frequency, and moisture transport. The role of environmental properties on their development is also examined by altering the concentration of available aerosol particles and other environmental parameters such as sea surface temperature. Assessment of the relative role of aerosol particles to other environmental parameters in PCF cumulus cloud development provides valuable knowledge of the controls on these clouds' contribution to the ETC radiative and moisture budget.

ETCs are global transporters of moisture. This study provides links between the cloud micro- and mesoscale structure to the overall ETC moisture budget. A case study of PCF cumulus clouds aids in quantifying a yet un-quantified portion of the ETC moisture and radiation budget. Assessing simulations with varying environmental factors including aerosol loading will allow for an investigation into aerosol-cloud interactions and the ETC larger scale cloud and precipitation patterns.