Sulfate Aerosols over the Southern Ocean
Improving the Representation of Sulfate Aerosols Over the Southern Ocean in the NZESM
Atmospheric aerosols affect Earth’s radiative balance, yet constitute one of the largest sources of uncertainty in model simulations of the Earth’s energy budget and climate.
Uncertainties in aerosols cascade to uncertainties in cloud formation, absorption of shortwave radiation by the ocean, and atmospheric circulation. Incorrect representation of aerosols over the Southern Ocean in the New Zealand Earth System Model (NZESM) reduces confidence in projections of climate change for New Zealand. In the current version of the NZESM, sulfate aerosol formation processes are either simplified, or driven by outdated information.
This project aimed to improve the representation of sulfate aerosols over the Southern Ocean in the NZESM by better understanding the largest source of natural sulfate aerosols in the troposphere, i.e. dimethyl sulfide (DMS). We improved the representation of DMS oxidation in the NZESM, implementing an up-to-date global DMS climatology as forcing data, and explored the role that sea ice plays in blocking oceanic emission of DMS.
Improving the representation of sulfate aerosol production in the NZESM ultimately provided more reliable simulations of New Zealand’s climate.
Revell, L. E., Kremser, S., Hartery, S., Harvey, M., Mulcahy, J. P., Williams, J., Morgenstern, O., McDonald, A. J., Varma, V., Bird, L., and Schuddeboom, A.: The sensitivity of Southern Ocean aerosols and cloud microphysics to sea spray and sulfate aerosol production in the HadGEM3-GA7.1 chemistry–climate model, Atmos. Chem. Phys., 19, 15447–15466, https://doi.org/10.5194/acp-19-15447-2019, 2019.