Community Talk: Sonya Fiddes (Australian Antarctic Program Partnership, IMAS, UTAS)
Evaluating ACCESS-AM2 against aerosol observations
Abstract
ACCESS-CM2 and AM2 include a double moment aerosol scheme that can prognostically simulate a range of aerosols. Natural marine aerosol and their interaction with clouds and radiation is one of the most significant sources of climate model uncertainty. The Southern Ocean provides a relatively unpolluted region to study natural processes and has some of the most significant cloud-radiation biases globally.
Here we present an evaluation of ACCESS-AM2 aerosol over the Southern Ocean. We evaluate against seven ship campaigns, two station campaigns, and the permanent instrumentation at Kennaook-Cape Grim (KCG). The observations span the years 2015-2019 and while biased towards summer, cover a range of seasons. We use observations of condensation nuclei (N10) and cloud condensation nuclei (CCN), measures of aerosol number concentrations at different sizes.
We find that N10 is heavily underestimated across all regions and seasons, with the bias worse at higher latitudes. Outside of northern latitudes, CCN is also significantly underestimated, while at KGC, the model performs within 1% of observed.
We then perform eight experiments to explore different aerosol configurations. Increasing the sea spray flux improves CCN for marine regions but has detrimental impacts on the radiation budget. This presents a concern whereby improving one aspect of the system makes other parts significantly worse. Updating to the most recent dimethyl sulfide climatology and turning on the primary marine organic aerosol flux marginally improves CCN and the Southern Ocean radiative bias with limited compensating errors. We recommend this configuration is considered for future releases of ACCESS.
Please use this thread for further discussion on this talk.