Low marine cloud responses to systematic aerosol perturbations across a range of ambient conditions

Abstract:

Low marine clouds are some of the most susceptible to brightening with the addition of cloud condensation nuclei (i.e. via the Twomey effect), as demonstrated by the prominence of ship tracks. However, even for these clouds, the cloud-scene albedo response to aerosol perturbations can cover a large range, including a net decrease in scene albedo. This is because the full response is not only in terms of cloud droplet number concentrations but also cloud liquid water path, cloud lifetime, and precipitation, and all of these responses differ depending on ambient meteorological and aerosol conditions. This presentation will discuss large eddy simulations that systematically explore the full responses of low marine clouds to the addition of aerosol, where runs are initialized for case studies covering a spectrum of observed ambient conditions. In these runs, the model includes a representation of aerosol sinks and sources associated with cloud and precipitation processes, interstitial scavenging, sea spray, and ship emissions. This permits more realistic simulations of ship tracks and for exploring responses to the intentional injection of aerosol for climate intervention through marine cloud brightening. The ultimate goal is to test modeled responses against observations and gaining new insight to the processes controlling the net cloud-scene albedo response under different conditions.