Atmos. Chem. Phys. Discuss., 11, 1595-1639, 2011
www.atmos-chem-phys-discuss.net/11/1595/2011/
doi:10.5194/acpd-11-1595-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Simulated enhancement of ENSO-related rainfall variability due to Australian dust
L. D. Rotstayn1, M. A. Collier1, R. M. Mitchell2, Y. Qin2, and S. K. Campbell2
1Centre for Australian Weather and Climate Research, CSIRO Marine and Atmospheric Research, Aspendale, Vic, Australia
2Centre for Australian Weather and Climate Research, CSIRO Marine and Atmospheric Research, Canberra, ACT, Australia

Abstract. Average dust emissions from Australia are small compared to those from the major sources in the Northern Hemisphere. However, they are highly episodic, and this may increase the importance of Australian dust as a climate feedback agent. We compare two 160-year coupled atmosphere-ocean simulations of modern-day climate using the CSIRO Mark 3.6 global climate model (GCM). The first run (DUST) includes an interactive treatment of mineral dust and its direct radiative effects. The second run (NODUST) is otherwise identical, but has the Australian dust source set to zero. We focus on the austral spring season, when the correlation between rainfall and the El Niño Southern Oscillation (ENSO) is strongest over Australia. We find that the ENSO-rainfall relationship over eastern Australia is stronger in the DUST run: dry (El Niño) years tend to be drier, and wet (La Niña) years wetter. The ENSO-rainfall relationship is also weaker over north-western Australia in the DUST run. The amplification of ENSO-related rainfall variability over eastern Australia and the weaker ENSO-rainfall relationship over the north-west both represent an improvement relative to observations. The suggested mechanism over eastern Australia involves stabilisation of the surface layer due to enhanced atmospheric heating and surface cooling in El Niño years, and enhanced ascent and moisture convergence driven by atmospheric heating in La Niña years. The results suggest that (1) a realistic treatment of Australian dust may be necessary for accurate simulation of the ENSO-rainfall relationship over Australia, and (2) radiative feedbacks involving dust may be important for understanding natural rainfall variability over Australia.

Citation: Rotstayn, L. D., Collier, M. A., Mitchell, R. M., Qin, Y., and Campbell, S. K.: Simulated enhancement of ENSO-related rainfall variability due to Australian dust, Atmos. Chem. Phys. Discuss., 11, 1595-1639, doi:10.5194/acpd-11-1595-2011, 2011.
 
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