Seeding southern clouds

12 December 2018 This article is over 5 years old

Seeding Southern Clouds

Video transcript

Jared Lewis (Uni of Melbourne) — The AIRBOX is a great way of storing many instruments and all in one co-located area that we can move round wherever we need to make these measurements.

Dr Robyn Schofield (Uni of Melbourne) — We want to know how many there are, we want to know how large they are, we want to know how reflective they are.

Dr Robyn Schofield (Uni of Melbourne) — Over the Southern Ocean, a major source of aerosol, generally about 70% is sea salt. The tops of the waves get sheared off. That’s a major source of aerosol. Then they go on to form clouds. We wouldn’t have any clouds actually, without aerosols forming them.

Dr Robyn Schofield (Uni of Melbourne) — It’s a very clean and pristine environment over the Southern Ocean, and so the clouds that form, form really big droplets. And we get what’s called super saturation, so they’re both ice and water coexisting, so they are unusual.

Jared Lewis (Uni of Melbourne) — Helping us really narrow down the uncertainty in our climate model projections over the Southern Ocean. That’s a tremendously important thing.

[end transcript]

A mobile air chemistry lab called AIRBOX is hitching a ride on Australia’s icebreaker RSV Aurora Australis this summer, to peer into clouds as the ship plies the Southern Ocean.

By shading the earth’s surface and reflecting heat, clouds play a direct role in global warming. Clouds are seeded by tiny particles called aerosols, such as dust, soot or salt crystals.

The AIRBOX campaign, led by the University of Melbourne as part of the Australian Antarctic Program, is investigating the properties of these aerosols.

“We want to know how many aerosols there are, how large they are, how reflective they are, and how much water they can take up,” said project leader Dr Robyn Schofield.

This will provide vital details about the contribution of Southern Ocean clouds to regulating the Earth’s temperature, and remove some of the uncertainty in global climate models.

In the relatively unpolluted air above the Southern Ocean, the major source of aerosols is sea salt from wind shearing the tops off waves.

As a result, the concentrations of aerosols in the polar atmosphere above the Antarctic sea-ice differ from anywhere else.

There are also chemical processes in the ocean and in the sea ice that may influence aerosol concentrations.

The project aims to better understand where the aerosols are coming from that influence the clouds and how they are chemically made.

AIRBOX is a modified shipping container with nine instruments operating from the ship’s upper deck for six months. At least eight other instruments will be added over the summer.

Instruments include:

a mini-LIDAR that uses laser pulses to measure aerosol and cloud profiles up to 10 kilometres up;
an ozone monitor:
a trace gas analyser to measure greenhouse gases such as carbon dioxide, nitrous oxide and methane, and
a spectrometer to measure ultraviolet and visible light and chemicals including bromine monoxide, a naturally-occurring chemical that removes atmospheric mercury produced from industrial sources and power generation.

The use of these instruments is an innovative approach that has not been applied before in this part of the world and will help to improve the reliability of climate models for this region.

Also involved in the AIRBOX (Atmospheric Integrated Research facility for Boundaries and Oxidative Experiments) campaign are the Australian Antarctic Division, University of Tasmania, University of Melbourne, Queensland University of Technology, Macquarie University, University of Wollongong, CSIRO, Monash University and the Australian Nuclear Science and Technology Organisation (ANSTO).

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Group of team members outside AIRBOX on ship

This content was last updated 5 years ago on 12 December 2018.