Cloud droplet activation schemes

Motivation Met Office: UM new microphysics (4a scheme), linked to aerosols via parameterisations. Also WRF uses similar schemes. Flights over Irish Sea (notable fluxes of sea spray through cloud base) Ice processes, especially the HM process, are sensitive to the drop concentration: warm rain-> graupel-> ice multiplication. Two main parameterisations: –ARG widely used in models –FN less widely used (slightly more expensive) –FN with quadrature (developed by us, slightly more expensive again) –Compare to ACPIM parcel model

Good agreement here

Reasonable agreement here For example what happens when add some salt (large diameter)

For example what happens when add more salt (large diameter) Basically schemes underestimate activated number

For example what happens when add salt with small diameter Log scale: ARG underestimates significantly Remove the salt mode: ARG predicts that less activate when you add sea spray

F-N doesnt always work: but if quadrature is used it is better

Questions Can we constrain data from measurements and use to run large models? Aspects that werent well simulated? Snowing at the airport? Should we be use Fountoukis and Nenes with quadrature within models?