Searching for super-cooled Southern Ocean clouds
29th October 2017
Atmospheric scientists will use ships, aircraft and satellites to study super-cooled Southern Ocean clouds this summer.
The project involving Australian and United States researchers will gather data on super-cooled cloud formations, which are clouds that remain as liquid water well below freezing.
Australian Antarctic Division atmospheric scientist, Dr Simon Alexander, said while these clouds occur frequently above the Southern Ocean and around coastal Antarctica, little is known about them.
“We are going to look at the composition of clouds, how much ice or water they contain, and determine how they affect the weather and climate of the region,” Dr Alexander said.
From October through to March Australia’s icebreaker Aurora Australis, the CSIRO’s RV Investigator and the US National Science Foundation’s Gulfstream V aircraft, managed by the National Center for Atmospheric Research, will gather information on the clouds on many trips south from Hobart.
The Aurora Australis has had more than seven tonnes of equipment attached to a specially strengthened deck, including 24 atmospheric instruments from the US Department of Energy’s Atmospheric Radiation Measurement (ARM) Mobile Facility.
ARM Mobile Facilities Operations Manager, Kim Nitschke, said the scientists on the ship will monitor the clouds and the aerosols which contribute to cloud formation.
“A cloud lidar will use laser pulses to measure the thickness, composition and height of the clouds, while a cloud radar and microwave radiometer will look at the liquid and ice content,” Mr Nitschke said.
“Weather balloons will also be launched every six hours to measure temperature, winds and humidity above the ocean.”
Similar instruments will be carried by the RV Investigator across ice-free areas of the Southern Ocean in early 2018.
In the air, a United States research aircraft will collect information on the thermodynamic and physical properties above, below and within clouds.
“It may be an interesting ride, as the plane will fly ramped ascents and descents through aerosols, storms, and some super-cooled water clouds,” Dr Alexander said.
“There will be about 16 flights between mid-January and late February and some of these flights will occur at the same time that the ships are traversing the ocean.”
The research will feed into climate models to improve global weather and climate forecasts in the high southern latitudes and across the globe.
This year the Australian Antarctic Program will support 92 projects in Antarctica, the Southern Ocean and on sub-Antarctic Macquarie Island.
More than 500 expeditioners will travel south over the summer season on the Airbus A319 and C-17A Globemaster III, and on Australia’s icebreaker Aurora Australis, which departs Hobart today.
Dr Simon Alexander: This is brand new research. We have so little understanding of clouds in the Southern Ocean. This is the first time we'll have this major experiment to look at these special type of clouds, which exist at temperatures below zero degrees Celsius, yet they remain as liquid. They're called supercooled liquid clouds. To do this research over summer, we'll have three main platforms. We'll have the Aurora Australis, our ice breaker. We'll have CSIRO's RV Investigator, and we'll have a United States research aircraft. From the surface, we will have LIDARs and radars on the ships, looking at clouds from the surface. We will also be launching radiosondes - weather balloons - over the ocean, so that we can get profiles of temperature and relative humidity all the way from the surface up to the top of the troposphere. We want to know about them so that we can produce a book called Climatology - how often they occur, where they occur, what altitudes they occur, how thick they are - so that we can then compare these data with output from forecast models and climate models.