Recent increase in aerosol loading over the Australian arid zone

Mitchell, Rosalind; Campbell, S. K.; Qin, Yi

doi:10.5194/acp-10-1689-2010

Cited by 52 publications

(64 citation statements)

References 35 publications

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“…As a consequence, it is the major source of dust from the Australian continent. Mitchell et al (2010) noted an increase in aerosol loading over Australia's arid interior during the decade 1997-2007, presumably a result of the recent prolonged drought. Greene et al (2009) developed a conceptual model that describes the various dust sources and sinks, and the modes of transport of dust materials both into and out of source areas in SE Australia.…”

Section: Introductionmentioning

confidence: 99%

Optical, physical and chemical characteristics of Australian continental aerosols: results from a field experiment

Radhi

Box

et al. 2010

Atmos. Chem. Phys.

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Abstract. Mineral dust is one of the major components of the world's aerosol mix, having a number of impacts within the Earth system. However, the climate forcing impact of mineral dust is currently poorly constrained, with even its sign uncertain. As Australian deserts are more reddish than those in the Northern Hemisphere, it is important to better understand the physical, chemical and optical properties of this important aerosol. We have investigated the properties of Australian desert dust at a site in SW Queensland, which is strongly influenced by both dust and biomass burning aerosol.Three years of ground-based monitoring of spectral optical thickness has provided a statistical picture of gross aerosol properties. The aerosol optical depth data showed a clear though moderate seasonal cycle with an annual mean of 0.06 ± 0.03. The Angstrom coefficient showed a stronger cycle, indicating the influence of the winter-spring burning season in Australia's north. AERONET size distributions showed a generally bimodal character, with the coarse mode assumed to be mineral dust, and the fine mode a mixture of fine dust, biomass burning and marine biogenic material.In November 2006 we undertook a field campaign which collected 4 sets of size-resolved aerosol samples for laboratory analysis -ion beam analysis and ion chromatography. Ion beam analysis was used to determine the elemental composition of all filter samples, although elemental ratios were considered the most reliable output. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and Co reasonably well correlated with Si, with the Fe/Al ratio somewhat higher than values reported from Northern Hemisphere sites (as expected). Scatter plots for Ca, Mn and K against Si showed Correspondence to: M. A. Box (m.box@unsw.edu.au) clear evidence of a second population, which in some cases could be identified with a particular sample day or size fraction. These data may be used to attempt to build a signature of soil in this region of the Australian interior.Ion chromatography was used to quantify water soluble ions for 2 of our sample sets, complementing the picture provided by ion beam analysis. The strong similarities between the MSA and SO 2− 4 size distributions argue strongly for a marine origin of much of the SO 2− 4 . The similarity of the Na + , Cl − and Mg 2+ size distributions also argue for a marine contribution. Further, we believe that both NO are the result of surface reactions with appropriate gases.

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Section: Introductionmentioning

confidence: 99%

Optical, physical and chemical characteristics of Australian continental aerosols: results from a field experiment

Radhi

Box

et al. 2010

Atmos. Chem. Phys.

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“…Leys et al, 2008;Bullard et al, 2008) but less so via sun photometry, where the measurand -column aerosol optical depth -is the required input for climate and remote sensing studies. However, Mitchell et al (2010) analysed sun photometer and nephelometer measurements from Tinga Tingana in the Australian arid zone during the Millennium Drought (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010) and found an approximate doubling in both column and near-surface aerosol during the austral summer over the duration of the drought. Feedbacks related to dust aerosol were modelled by Rotstayn et al (2011), who found that inclusion of interactive dust in the model amplifies the impact of the El Niño-Southern Oscillation cycle on Australian climate.…”

Section: Introductionmentioning

confidence: 99%

The Climatology of Australian Aerosol

2017

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Abstract. Airborne particles or aerosols have long been recognised for their major contribution to uncertainty in climate change. In addition, aerosol amounts must be known for accurate atmospheric correction of remotely sensed images, and are required to accurately gauge the available solar resource. However, despite great advances in surface networks and satellite retrievals over recent years, longterm continental-scale aerosol data sets are lacking. Here we present an aerosol assessment over Australia based on combined sun photometer measurements from the Bureau of Meteorology Radiation Network and CSIRO/AeroSpan. The measurements are continental in coverage, comprising 22 stations, and generally decadal in timescale, totalling 207 station-years. Monthly climatologies are given at all stations. Spectral decomposition shows that the time series can be represented as a weighted sum of sinusoids with periods of 12, 6 and 4 months, corresponding to the annual cycle and its second and third harmonics. Their relative amplitudes and phase relationships lead to sawtooth-like waveforms sharply rising to an austral spring peak, with a slower decline often including a secondary peak during the summer. The amplitude and phase of these periodic components show significant regional change across the continent. Fits based on this harmonic analysis are used to separate the periodic and episodic components of the aerosol time series. An exploratory classification of the aerosol types is undertaken based on (a) the relative periodic amplitudes of the Ångström exponent and aerosol optical depth, (b) the relative amplitudes of the 6-and 4-month harmonic components of the aerosol optical depth, and (c) the ratio of episodic to periodic variation in aerosol optical depth. It is shown that Australian aerosol can be broadly grouped into three classes: tropical, arid and temperate. Statistically significant decadal trends are found at 4 of the 22 stations. Despite the apparently small associated declining trends in mid-visible aerosol optical depth of between 0.001 and 0.002 per year, these trends are much larger than those projected to occur due to declining emissions of anthropogenic aerosols from the Northern Hemisphere. There is remarkable long-range coherence in the aerosol cycle across the continent, suggesting broadly similar source characteristics, including a possible role for intercontinental transport of biomass burning aerosol.

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“…A 10-year aerosol climatology at this site (Mitchell et al, 2010) showed dual peaks in AOD in September and January, the former including a significant fine-particle mode characteristic of smoke from long-range transport, while the January peak was dominated by coarse particles characteristic of wind-blown dust. Figure 3 compares the observed and modelled annual cycles of AOD.…”

Section: Dust Simulationmentioning

confidence: 99%

“…Satellite retrievals identify the large (1 140 000 km 2 ) Lake Eyre Basin of central-eastern Australia as the largest dust source in the Southern Hemisphere (Prospero et al, 2002); see also Washington et al (2003), McTainsh et al (2007), Bullard et al (2008) and Mitchell et al (2010). Compared to the major Northern Hemisphere dust source regions, Australian average dust emissions are relatively low.…”

Section: Introductionmentioning

confidence: 99%

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Simulated enhancement of ENSO-related rainfall variability due to Australian dust

et al. 2011

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Abstract. Australian dust emissions 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. The ENSOrainfall 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 amplification of ENSO-related rainfall variability over eastern Australia represents an improvement relative to observations. The effect is driven by ENSO-related anomalies in radiative forcing by Australian dust over the south-west Pacific Ocean; these anomalies increase (decrease) surface evaporation in La Niña (El Niño) years. Some of this moisture is advected towards eastern Australia, where increased (decreased) moisture convergence in La Niña (El Niño) years increases the amplitude of ENSOrelated rainfall variability. The modulation of surface evaporation by dust over the south-west Pacific occurs via surface radiative forcing and dust-induced stabilisation of the boundary layer. 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.

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Recent increase in aerosol loading over the Australian arid zone

Abstract: Abstract. Collocated sun photometer and nephelometer measurements at Tinga Tingana in the Australian Outback over the decade

Cited by 52 publications

References 35 publications

Optical, physical and chemical characteristics of Australian continental aerosols: results from a field experiment

Optical, physical and chemical characteristics of Australian continental aerosols: results from a field experiment

The Climatology of Australian Aerosol

Simulated enhancement of ENSO-related rainfall variability due to Australian dust

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