Project: Southern Ocean cloud-aerosol-radiation-precipitation interactions

Understanding cloud-aerosol-radiation-precipitation interactions over the Southern Ocean to improve climate models and future climate predictions.

The Southern Ocean (SO) is a region of great importance to global and Australian climate and weather. Climate models are challenged by uncertainties in the simulation of SO clouds, aerosols, and surface fluxes. These biases produce large errors on the surface radiation budget and affect the location of sub-tropical jets, the simulation of anthropogenic indirect aerosol effects on climate, and the simulated global cloud feedbacks and carbon‐cycle feedbacks on climate change.

These model challenges can be traced to poor physical understanding of these processes. This lack of physical understanding can in turn be attributed to the unavailability of state-of-the-art observations of clouds, aerosols, precipitation, radiation and the air‐sea interface, hindering our capability to conduct process studies.

That is why the Bureau and its Australian and international collaborators have designed a multi-pronged observational strategy to collect the required SO observations:

  • The CAPRICORN project (2015-2018): R/V Investigator over the Southern Ocean. Clouds, aerosols, precipitation, surface energy fluxes, atmospheric composition. Process studies and statistical properties. Lead A. Protat (BOM)
  • The AAD ACRE and US ARM MICRE projects (2016-2018): Two years of continuous ground-based observations at Macquarie Island (54S). High-quality measurements but at a single point. Focus is intraseasonal and interannual variability. Leads Roj Marchand (U. Washington), S. Alexander (AAD), A. Protat (BOM).
  • The ARM MARCUS project (2017-2018): AAD Aurora Australis resupply voyages with ARM Mobile Facility (2 containers). Add to ACRE and CAPRICORN statistics, extend statistics further South. Lead G. Mc Farquhar (Univ. Illinois) with Australian contributions from BOM and AAD.
  • The SOCRATES international experiment (Jan- Feb 2018): NCAR G-V aircraft (US NSF funded) coordinated with the 2018 CAPRICORN RV Investigator voyage (MNF granted). Aircraft in-situ and remote sensing measurements of cloud – aerosol interactions on transects. Leads G. Mc Farquhar (NCAR G-V), A. Protat (CAPRICORN).

Mean errors on absorbed surface shortwave radiation in CMIP5 climate models. This figure shows that models do not reflect enough sunlight back to space over the Southern Ocean.

Leader

Alain Protat

Australian collaborators

  • Melita Keywood, Ruhi Humphries (CSIRO)
  • Simon Alexander, Andrew Klekociuk (AAD)
  • Steve Siems, Yi Huang (Monash)
  • Todd Lane, Robyn Schofield (Melbourne Uni)
  • Zoran Ristovski, Luke Cravigan (QUT)

Deliverables

  • Understanding the complex aerosols, clouds, precipitation, and radiation interactions
  • Understanding the physical reasons for climate model biases
  • Improving the ACCESS climate model in this region (see also NESP Project 2.5)

For more information
please contact Alain Protat, alain.protat@bom.gov.au