Atmosphere Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Dr Peter Manins, Environmental Consulting and Research Unit, CSIRO Atmospheric Research, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06746 9
Climate Variability and Change (continued)
Average aerosol loading [A Indicator 1.19]
Aerosol (especially sulfate aerosol generated by human activities) increases the effective albedo or reflectivity of the planet. In this way, aerosol can partly offset the global warming likely to result from the increase in greenhouse gases due to human activity. Global climate models also simulate reduced warming under enhanced greenhouse conditions if they incorporate aerosols (IPCC 1996). Because of Australia's low population and relative isolation in the Southern Hemisphere, the aerosol loading as a result of industry is relatively small and concentrated near major industrial towns. However, there is significant aerosol generated by annual burning in tropical Australia and by wind-blown dust in the arid zone during summer. Sea-salt is also a significant source of aerosol in Australia (Ayers et al. 1999).
A time series of atmospheric aerosol measurements obtained from CSIRO field sites in Northern Territory and South Australia during 1999 and 2000 exhibits peaks in late spring, coinciding with maximum burning in the north, and with surface and wind conditions conducive to dust transport in the arid zone (Figure 34). The reduction in solar radiance that reaches the surface as a result of the amount of aerosol (i.e. the plotted aerosol optical depth) follows an exponential relationship (e.g. an optical depth of 1 reduces the radiance reaching the surface to 37% of its value at the top of the atmosphere).
Figure 34: Aerosol optical depth-time series obtained from a tropical site and an arid site.
The tropical site is Lake Argyle in the Kimberley region of Western Australia and the arid site is at Tinga Tingana in the Strzelecki Desert, South Australia.
Source: CSIRO Atmospheric Research
Continental-scale high-quality aerosol measurements are required to validate climate model simulations. Although older satellite systems such as the Advanced Very High Resolution Radiometer are able to measure only aerosol over the oceans, newer satellite sensors are capable of obtaining aerosol data over land. Surface stations operated by the BoM and CSIRO will contribute to validation of satellite aerosol retrievals and generation of aerosol climatologies over land.