Model-Observation comparison of Southern Ocean aerosols in ACCESS-CM2 — Australian Meteorological and Oceanographic Society
  1. Schedule
  2. Afternoon Tea + Poster Session 2
  3. Model-Observation comparison of Southern Ocean aerosols in ACCESS-CM2

Model-Observation comparison of Southern Ocean aerosols in ACCESS-CM2 (#2004)

Imogen Wadlow 1 2 , Robyn Schofield 2 , Matt Woodhouse 3 , Todd Lane 1 2
  1. ARC Centre of Excellence for Climate Extremes, Sydney , NSW, Australia
  2. School of Earth Sciences, University of Melbourne, Melbourne, VIC, Australia
  3. Climate Science Centre, Commonwealth Scientific and Industrial Research Organisation , Aspendale, VIC, Australia

Aerosols play a significant role in the Earth’s climate through interaction with radiation and cloud processes, by scattering and absorbing radiation and altering cloud albedo. The Southern Ocean (SO) is an understudied region of climatic significance dominated by natural aerosols; these aerosols contribute to the largest uncertainties in radiative forcing estimates. Hence, increasing understanding of how effectively these are represented in Global Climate Models (GCMs) is important.

Lacking observational data and complex atmospheric processes has resulted in significant biases in simulated radiation budgets. Aerosol-cloud interactions have been identified as playing a key role in this bias (Li,et.al.2013).

In this study, we investigate the representation of aerosols in the Australian Community Climate and Earth System Simulator (ACCESS)-CM2, which incorporates the detailed microphysical aerosol scheme GLObal Model of Aerosol Processes- mode (GLOMAP-mode). Limited literature in SO model aerosol-evaluation exists, particularly for this new generation of ACCESS-CM2 which will contribute to CMIP6.

An atmosphere-only version of ACCESS-CM2 was run in three simulation designs from years 2016-2018 with meteorology nudged to ERA-Interim at 6-hourly intervals and a resolution of 1.25° latitude by 1.85° longitude. The designs consist of a base model run, and additional runs including Primary Marine Organic emissions (which influence aerosol characteristics and cloud formation (Fossum,et.al.2018)), and Online Oxidants (which provides a more comprehensive atmospheric chemistry). Hourly model output has been compared against a suite of below-cloud time-series data collected at observation stations and on voyages in the SO. Aerosol simulation in the model has been evaluated using parameters including Aerosol Optical Depth and Cloud Condensation Nuclei to provide the representation of aerosol size and type. This study examined the ability of each model simulation to represent temporal aerosol variations, identified model bias and evaluated whether the addition of a more chemically-comprehensive atmosphere provided a more accurate and worthwhile representation of aerosols.

  1. Li, J, L, F. Waliser, D, E. Stephens, G. Lee, Seungwon. L’Ecuyer, T. Kato, S. Loeb, N & Ma, H. 2013. Characterizing and understanding radiation budget biases in CMIP3/CMIP5 GCMs, contemporary GCM, and reanalysis. Journal of Geophysical Research: Atmospheres. 118. 8166-8184.
  2. Fossum, K. Ovadnevaite, J. Ceburnis, D. Dall’Osto, M. Marullo, S. Bellacicco, M. Simó, R. Liu, D. Flynn, M. Zuend, A. O’Dowd, C. 2018. Summertime Primary and Secondary Contributions to Southern Ocean Cloud Condensation Nuclei. Nature Scientific Reports. 8: 13844.
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