Studying clouds over the Southern Ocean
10 January 2018
It’s one of the mysteries of the vast Southern Ocean—what’s happening down there when it comes to clouds, rain, radiation from the sun and particles in the atmosphere? So we’ve joined forces with key Australian and US organisations to collect measurements. But why is this important—and how will our work help solve the mystery?
A place apart: why study clouds over the Southern Ocean?
The Southern Ocean—the waters surrounding Antarctica—is a truly unique environment. With virtually no land mass, no industries and no inhabitants, the air in this area is pristine. Cloud formation here relies on tiny particles (also called ‘aerosols’) and gases produced by bacteria and plankton in the ocean rather than being strongly affected by forests, dust and human pollution, as is the case in inhabited areas. Also, this latitude band experiences very high near-surface winds (usually exceeding 74 km/h) and high rainfall with distinctive characteristics.
The limited knowledge we have about the Southern Ocean's atmospheric conditions is a major concern in current global climate models. By collecting and understanding new data, we can produce a better global picture to improve future climate predictions.
International collaboration: who is involved?
The Bureau of Meteorology, Australian Antarctic Division, CSIRO and Australian universities are collaborating with the US Department of Energy Atmospheric System Research program and US universities to fill the gap that currently exists about atmospheric conditions over the Southern Ocean.
The US component of the study is called SOCRATES (Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study), which will see data collected via the National Centre for Atmospheric Research's aircraft. The Australian component is called CAPRICORN (Clouds, Aerosols, Precipitation, Radiation and Atmospheric Composition over the Southern Ocean) with Australian and US scientists collecting data on board the Australian Marine National Facility research vessel Investigator.
The Australian team is led by Principal Investigator—and Bureau of Meteorology scientist—Alain Protat. Alain has been coordinating the Australian community research work on the Southern Ocean since 2011, including the initial sea trial in 2015 and a one-month field experiment in 2016. Now he is gearing up to coordinate the scientists for their second field experiment, a seven-week voyage leaving Hobart, Tasmania on 10 January. On this voyage, the Australian team aims to collect very detailed observations of clouds, rainfall, particles, impact from the sun's rays, and winds. From there, their focus will turn to understanding the observations to determine what in the formation of clouds, and the associated rainfall, is so different from elsewhere around the globe. This information will assist in understanding how accurate cloud, aerosol and rainfall characteristics as observed from satellites are for the Southern Ocean, as well as improve our forecasting and climate predictions for this area.
Air, sea and space: how will the study work?
The study will use a unique combination of aircraft, ship-based and satellite observations. Each type of observation has pros and cons; for example, Australian ship-based observations allow a comprehensive suite of instruments to be used when compared to those on the aircraft used by the US team. But the ship-based observations can't 'see' inside the clouds directly, whereas the aircraft can measure the clouds and atmospheric particles from the appropriate position. Where the ship-based and aircraft observations are both limited, validated satellite observations can fill in. By joining forces, we can create a clearer picture.
Image: On deck in the Southern Ocean during first RV Investigator field experiment in 2016. Credit: Gloria Salgado Gispert
What’s next: when will we see the results?
The field experiment runs from 10 January until 26 February, but the science is expected to be used for the next four years. The teams will continue to work together to share the information through published articles, as well as international conferences including two dedicated SOCRATES workshops—the first to be held in the US and the second to be organised by the Bureau of Meteorology and held in Melbourne.
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