Climate models to benefit from subantarctic cloud watch

The atmospheric instruments deployed on Macquarie Island include a ceilometer, microwave radiometer and various broadband radiometers provided by the US Department of Energy’s Atmospheric Radiation Measurement program, along with the Bureau of Meteorology’s cloud radar (partially visible at the lower right).
The atmospheric instruments deployed on Macquarie Island include a ceilometer, microwave radiometer and various broadband radiometers provided by the US Department of Energy’s Atmospheric Radiation Measurement program, along with the Bureau of Meteorology’s cloud radar (partially visible at the lower right). (Photo: Jeff Aquilina)
This graphic shows clouds recorded over Macquarie Island by the Australian Antarctic Division lidar on 10 April 2016. The cloud base descends from 6 km altitude to 2.5 km altitude throughout the day. Black vertical stripes indicate missing data due to lower-level clouds.

An array of atmospheric instruments was deployed on Macquarie Island in April to help scientists better understand Southern Ocean clouds and how they can be used to improve weather forecasting and climate models.

Australian Antarctic Division atmospheric scientist and Chief Investigator of the project, Dr Simon Alexander, said a lack of data on Southern Ocean clouds prevents Southern Hemisphere climate models from accurately representing atmospheric energy balance (heat coming into the atmosphere versus heat going out). This in turn affects the accuracy of how models represent and forecast temperatures, the movement of weather systems, sea ice formation and ocean currents.

“Most research on high latitude clouds has focussed on the Arctic, but the clouds above the Southern Ocean are thought to be unique and include ‘super-cooled water clouds’ which remain as liquid water at temperatures well below freezing,” Dr Alexander said.

“As Macquarie Island sits in the path of weather systems which circulate around the Antarctic continent, it’s an ideal place to conduct cloud-related research.”

Dr Alexander and colleagues from the Australian Antarctic Division, Bureau of Meteorology and the US Department of Energy, installed the instruments to measure the seasonal cycle of cloud, aerosol and radiation properties over the Southern Ocean.

The instruments, which are now collecting data, include a cloud LIDAR, cloud radar and microwave radiometer that will measure clouds from near the surface up to 10 km altitude (Australian Antarctic Magazine 28: 6-7, 2015). They will help scientists determine whether the clouds are composed of ice, water or a mixture of both.

"We will be able to determine the altitude at which the various cloud phases occur, how frequently they occur, and how they are related to weather systems,” Dr Alexander said.

Current knowledge of Southern Ocean clouds and the atmosphere rely heavily on satellites, yet these have difficulty measuring low-level clouds and the data has proven difficult to validate. The data from the ground-based observations at Macquarie Island will allow the team to validate the satellite data over the Southern Ocean.

The instruments will remain on the island for up to two years, with some to be transported to Antarctica to record similar cloud properties above Davis station later this decade.

The project is supported by the Australian Antarctic Division, the United States Department of Energy’s Atmospheric Radiation Measurement (ARM) program, the Bureau of Meteorology, CSIRO and the University of Canterbury in New Zealand.

Corporate Communications
Australian Antarctic Division