Energetic regulation of radiative and microphysical aerosol effects on regional precipitation

Abstract:

Aerosol effects on precipitation via aerosol-cloud interactions have traditionally been assessed bottom-up, modelling or observing the chain of microphysical processes from aerosols acting as cloud condensation via cloud microphysics to precipitation formation of individual clouds and cloud fields. However, this relies on a complete understanding of a very complex and uncertain process chain and has been shown to be subject to large uncertainties.

In previous work we have shown that the response of regional precipitation to idealised and realistic aerosol radiative perturbations can be well explained in an energetic framework (because associated changes in the net diabatic heating needs to be balanced by latent heat release, surface or top-of-atmosphere fluxes or compensated for by energy divergence/convergence). We previously demonstrated for the case of absorbing aerosol that, while tropical near-equator precipitation is susceptible to regional precipitation perturbations, the Coriolis effect limits higher latitude precipitation changes via the availability to diverge energy / converge water vapour.

In this presentation we will contrast the precipitation response to aerosol radiative perturbations with the response to microphysical perturbations. Using the ICON global climate model in idealised aqua-planet configurations we prescribe idealised microphysical precipitation changes with varying spatial patterns and locations to generalise the energetic framework for precipitation and to show that regional precipitation is ultimately regulated by budgetary constraints.