Search

Large‐scale geomorphic drivers that operate at continental scale are often climate driven. Changes in land use can accelerate wind erosion. The range of land management practises within one land use can have dramatic effect on ground cover and wind erosion. This study uses meteorological observations, land use, land management and dust concentration measurements of 129 dust events recorded between 1990 and 2007 to describe a dust chronology of Mildura, in south‐eastern Australia. Frontal and frontal trough weather systems account for 74% of dust events. Furthermore, 88% of dust events come from rangelands in the northwest and the cropping lands to the southwest. The cropping areas to the southwest are the most common source of dust, accounting for 66% of events There is no relationship between rainfall and dust activity in this study, suggesting that land‐management practices, especially on cropping lands, over‐ride the controlling effect of rainfall. When cropping lands received above average rainfall in spring and summer during the 1990s, cultivation for weed control lead to rapid decline in ground cover that predisposed the land to wind erosion in following summer and autumn. In drought years, dust blows into Mildura from all directions suggesting that dust is climate driven rather than controlled by land use.

Dust entrainment, transport over vast distances and subsequent deposition is a fundamental part of the Earth system. Yet the role and importance of dust has been underappreciated, due largely to challenges associated with recognising dust in the landscape and interpreting its depositional history. Despite these challenges, interest in dust is growing. Technical advances in remote sensing and modelling have improved understanding of dust sources and production, while advances in sedimentology, mineralogy and geochemistry (in particular) have allowed dust to be more easily distinguished within sedimentary deposits. This has facilitated the reconstruction of records of dust emissions through time. A key advance in our understanding of dust has occurred following the development of methods to geochemically provenance (fingerprint) dust to its source region. This ability has provided new information on dust transport pathways, as well as the reach and impact of dust. It has also expanded our understanding of the processes driving dust emissions over decadal to millennial timescales through linking dust deposits directly to source area conditions. Dust provenance studies have shown that dust emission, transport and deposition are highly sensitive to variability in climate. They also imply that dust emissions are not simply a function of the degree of aridity in source areas, but respond to a more complex array of conditions, including sediment availability. As well as recording natural variability, dust records are also shown to sensitively track the impact of human activity. This is reflected by both changing dust emission rates and changing dust chemistry. Specific examples of how dust responds to, and records change, are provided with our work on dust emissions from Australia, the most arid inhabited continent and the largest dust source in the Southern Hemisphere. These case studies show that Australian dust emissions reflect hydro-climate variability, with reorganisation of Australian dust source areas occurring during the mid to late Holocene. Dust emissions are shown to sensitively map the structure of the Last Glacial Maximum in Australia, demonstrating that this period was associated with enhanced, but also variable dust emissions, driven by changing sources area conditions. Finally we show how dust emissions have responded to the arrival of Europeans and the associated onset of broad-scale agriculture across the Australian continent.

From the late 1990s to mid-2010, Australia was affected by a prolonged period of drought, the “Millennium Drought,” during which numerous severe dust storms crossed the continent. We inspect this period to produce the first continental-scale climatology of air-parcel trajectories that is specific to dust and use it to gain new insights into dust transport dynamics over the eastern half of Australia. The analysis is based upon dust arrival times from airport meteorological observations made at nine mostly coastal cities for 2000–2009. The Hybrid Single-Particle Lagrangian Integrated Trajectory model was used to calculate 1.26 million backward trajectories from receptor cities, with only those trajectories associated with a dust storm observation considered in the analysis of dust transport. To tie dust trajectories from receptors to likely emission sources, trajectories were linked to six known major dust source regions in and around the Lake Eyre Basin. The Lake Eyre North ephemeral lake system, alluvial-dominated Channel Country, and agricultural Mallee-Riverina regions emerge as important sources for the period, providing variable contributions to different parts of the seaboard as controlled by different front-related wind systems. Our study also provides new detail regarding dust pathways from continental Australia. For the Millennium Drought we identify that the broadly established Southeast Dust Path may be more accurately subdivided into three active pathways, driven by prefrontal northerly winds and a variation in the influence of frontal westerlies. The detail of these pathways has implications for dust delivery from specific Australian sources to different marine environments.

Wind erosion processes affect soil surfaces across all land uses worldwide. Understanding the spatial and temporal scales of wind erosion is a challenging undertaking because these processes are diverse and highly variable. Wind tunnels provide a useful tool as they can be used to simulate erosion at small spatial scales. Portable wind tunnels are particularly valued because erosion can be simulated on undisturbed soil surfaces in the field. There has been a long history of use of large portable wind tunnels, with consensus that these wind erosion simulation tools can meet real world aerodynamic criteria. However, one consequence of striving to meet aerodynamic reality is that the size of the tunnels has increased, making them logistically difficult to work with in the field and resulting in a tendency to homogenise naturally complex soil surfaces. This homogenisation is at odds with an increasing awareness of the importance that small scale processes have in wind erosion. To address these logistical and surface homogenisation issues we present here the development and testing of a micro wind tunnel (MWT) designed to simulate wind erosion processes at high spatial resolution. The MWT is a duct-type design—0.05 m tall 0.1 m wide and with a 1.0 m working section. The tunnel uses a centrifugal motor to suck air through a flow‐conditioning section, over the working section and then through a sediment collection trap. Simulated wind velocities range from 5 to 18 m s−1, with high reproducibility. Wind speeds are laterally uniform and values of u* at the tunnel bed (calculated by measuring the pressure gradients within the MWT) are comparable with those of larger tunnels in which logarithmic profiles can be developed. Saltation sediment can be added. The tunnel can be deployed by a single person and operated on slopes ranging from 0 to 10°. Evidence is presented here that the MWT provides new and useful understanding of the erodibility of rangelands, claypans and ore stockpiles.

Since the pioneering work of Bagnold in the 1940s, aeolian research has grown to become an integral part of earth-system science. Many individuals have contributed to this development, and Dr. Michael R. Raupach (1950–2015) has played a pivotal role. Raupach worked intensively on wind erosion problems for about a decade (1985–1995), during which time he applied his deep knowledge of turbulence to aeolian research problems and made profound contributions with far-reaching impact. The beauty of Raupach’s work lies in his clear conceptual thinking and his ability to reduce complex problems to their bare essentials. The results of his work are fundamentally important and have many practical applications. In this review we reflect on Raupach’s contribution to a number of important aspects of aeolian research, summarise developments since his inspirational work and place Raupach’s efforts in the context of aeolian science. We also demonstrate how Raupach’s work provided a foundation for new developments in aeolian research. In this tribute, we concentrate on five areas of research: (1) drag partition theory; (2) saltation roughness length; (3) saltation bombardment; (4) threshold friction velocity and (5) the carbon cycle.

Subjective visual interpretation of MODIS Quick-Look imagery has proven useful in characterising dust source geomorphology and dust event frequency over diverse areas, but is limited by the small temporal sampling window of polar orbiting platforms, and obscuration by cloud. In this paper we seek to quantify the inevitable under-reporting of dust events in Quick-Look imagery, via a three-year case study over the Lake Eyre Basin (LEB), the largest dust source in Australia and the southern hemisphere. Dust event identification from MODIS imagery is compared with the level of dust mobilization inferred from measurements of near-surface aerosol made by a continuously-operating integrating nephelometer, located at the AeroSpan/AERONET station at Tinga Tingana in the Strzelecki Desert, adjacent to major dust sources in the LEB. The analysis indicates a major upward revision in the overall dust event frequency by ~ 72%, including a doubling of the incidence of major dust outbreaks. The intensity of missed events increases toward late afternoon and evening, although without a net day-night bias. These factors suggest the potential of new geostationary sensors and the analysis of night-time polar orbiting imagery in improving the reporting of dust mobilization over active dust-source regions. For the LEB, the corrections are crucial in understanding not only the seasonal distribution of dust mobilization, but its interannual variability and climatology.

The roles of pre-frontal, frontal and post-frontal winds as the primary wind systems for dust entrainment and transport in Australia are well established. While the relevance of each system has been observed across different wind erosion events in central Australia, the entrainment of dust by all three winds during the passage of an individual front has not been demonstrated until now. Synoptic information, satellite aerosol and imagery, meteorological and dust concentration data are presented for a single case study erosion event in the lower Lake Eyre Basin. This event demonstrates variable dust transport in three different directions from one of the southern Hemisphere's most significant source regions, and the changing nature of the active dust pathways during the passage of a frontal system. While only a single dust event is considered, the findings show the complexity of mineral aerosol emission and transport patterns even within an individual dust outbreak. For the lower Lake Eyre Basin, this appreciation of pathway behaviour is significant for better understanding the role of aeolian inputs from the dominant Australian source to surrounding marine systems. In a wider context, the findings exhibit the detailed insights into major dust source dynamics that can be obtained from high resolution spatial and particularly temporal data, as used in combination. This work highlights the importance of adequately resolved data for the accurate determination of dust entrainment and transport patterns of major dust sources.

The pattern of 137Cs-derived net (1950s–1990) soil redistribution over Australia, together with back-trajectory modeling of major dust storms, shows extensive areas of contemporary aeolian deposition. While the Cobar Peneplain and Gawler bioregions are the largest, the Wet Tropics is also a locus of deposition, consistent with the theory that dust is a source of nutrients for tropical rainforests growing on ancient weathered soils. Here we describe a new dust transport pathway over northeastern Australia and substantiate the link between fluvial and aeolian processes, and biogeochemical cycling between Australia’s arid interior and its coastal forests

An estimated 110 Mt of dust is eroded by wind from the Australian land surface each year, most of which originates from the arid and semi-arid rangelands. Livestock production is thought to increase the susceptibility of the rangelands to wind erosion by reducing vegetation cover and modifying surface soil stability. However, research is yet to quantify the impacts of grazing land management on the erodibility of the Australian rangelands, or determine how these impacts vary among land types and over time. We present a simulation analysis that links a pasture growth and animal production model (GRASP) to the Australian Land Erodibility Model (AUSLEM) to evaluate the impacts of stocking rate, stocking strategy and land condition on the erodibility of four land types in western Queensland, Australia. Our results show that declining land condition, over stocking, and using inflexible stocking strategies have potential to increase land erodibility and amplify accelerated soil erosion. However, land erodibility responses to grazing are complex and influenced by land type sensitivities to different grazing strategies and local climate characteristics. Our simulations show that land types which are more resilient to livestock grazing tend to be least susceptible to accelerated wind erosion. Increases in land erodibility are found to occur most often during climatic transitions when vegetation cover is most sensitive to grazing pressure. However, grazing effects are limited during extreme wet and dry periods when the influence of climate on vegetation cover is strongest. Our research provides the opportunity to estimate the effects of different land management practices across a range of land types, and provides a better understanding of the mechanisms of accelerated erosion resulting from pastoral activities. The approach could help further assessment of land erodibility at a broader scale notably if combined with wind erosion models.

Australian meteorological observers started using the World Meteorological Organization (WMO) weather coding system in the 1950s. This system is still in use around the world today. However, observing and recording the weather in an organized and systematic manner had been ongoing for over 100 years prior to the adoption of this coding system, and much like Australia, most countries will have historical meteorological records. In this paper we compare the wind erosion of two of the greatest droughts in Australian recorded history; the World War II (WWII) Drought (1937–1945) and the Millennium Drought (2001–2009). To do this we analysed previously unavailable meteorological observer records from the Australian Bureau of Meteorology (ABM). Wind erosion records, mostly in long-hand written form, were translated to the modern WMO coding system for the WWII Drought and compared with the wind erosion of Australia's recently-ended Millennium Drought, one of the longest and harshest on record. We quantify wind erosion using Dust Event Days (DED) and a modified version of a published Dust Storm Index (DSI) to show that wind erosion during the WWII Drought was up to 4.6 times higher than during the Millennium Drought. This study has international significance because it demonstrates a methodology for tracking changes in wind erosion over the past 75 years based on observer records available in every country with a history of organized weather observation. Copyright © 2014 John Wiley & Sons, Ltd.

This study reports findings on observed visibility reductions and associated concentrations of mineral dust from a detailed Australian case study. An understanding of the relationship between visibility and dust concentration is of considerable utility for wind erosion and aeolian dust research because it allows visibility data, which are available from thousands of weather observation stations worldwide, to be converted into dust concentrations. Until now, this application of visibility data for wind erosion/dust studies has been constrained by the scarcity of direct measurements of co-incident dust concentration and visibility measurements. While dust concentrations are available from high volume air samplers, these time-averaged data cannot be directly correlated with instantaneous visibility records from meteorological observations. This study presents a new method for deriving instantaneous values of total suspended dust from time averaged (filter-based) samples, through reference to high resolution PM10 data. The development and testing of the model is presented here as well as a discussion of the derived expression in relation to other visibility-dust concentration predictive curves. The current study is significant because the visibility-dust concentration relationship produced is based on visibility observations made 10–100 km from the dust sources. This distance from source makes the derived relationship appropriate for a greater number of visibility recording stations than widely-used previous relationships based on observations made directly at eroding sources. Testing of the new formula performance against observed total suspended dust concentrations demonstrates that the model predicts dust concentration relatively well (r2 = 0.6) from visibility. When considered alongside previous studies, the new relationship fits into the continuum of visibility-dust concentration outcomes existing for increasing distance-from-source. This highlights the important influence that distance to source has on the visibility-dust concentration relationship.

Wind erosion of soils is a natural process that has shaped the semi-arid and arid landscapes for millennia. This paper describes the Dust Storm Index (DSI); a methodology for monitoring wind erosion using Australian Bureau of Meteorology (ABM) meteorological observational data since the mid-1960s (long-term), at continental scale. While the 46 year length of the DSI record is its greatest strength from a wind erosion monitoring perspective, there are a number of technical challenges to its use because when the World Meteorological Organisation (WMO) recording protocols were established the use of the data for wind erosion monitoring was never intended. Data recording and storage protocols are examined, including the effects of changes to the definition of how observers should interpret and record dust events. A method is described for selecting the 180 long-term ABM stations used in this study and the limitations of variable observation frequencies between stations are in part resolved. The rationale behind the DSI equation is explained and the examples of temporal and spatial data visualisation products presented include; a long term national wind erosion record (1965–2011), continental DSI maps, and maps of the erosion event types that are factored into the DSI equation. The DSI is tested against dust concentration data and found to provide an accurate representation of wind erosion activity. As the ABM observational records used here were collected according to WMO protocols, the DSI methodology could be used in all countries with WMO-compatible meteorological observation and recording systems.

Atmospheric aerosol samples were collected at a remote site in New Zealand's Southern Alps. Collected samples were found to be a mixture of New Zealand and Australian sourced sediment, using their trace element signatures. Aerosol concentrations and the relative contribution of different sources was found to be a function of specific air-mass trajectories influencing the study site, dust entrainment rates in source areas and rainfall. Results show that Australian dust is a major source of particulate matter in New Zealand, particularly in remote alpine locations; however, locally derived dust is also important. Metal pollutants, including Pb, Cu and Sn, were enriched in the samples by approximately 15 times and up to >100 times expected natural concentrations, confirming that metal pollution is a ubiquitous component of the atmosphere, even in relatively remote locations. Moreover, pollutants were highly enriched in otherwise clean air, i.e. during and following rainfall. Additionally, high concentrations of elements naturally enriched in sea water, e.g. Sr, Ba and Rb, were deposited alongside mineral dust, reflecting the oceanic origin of air influencing the site and the role of sea spray in contributing aerosol to the atmosphere. These elements experienced the greatest enrichment during rainfall, implying sea spray and pollution become relatively important during otherwise clean air conditions.

Cyanobacterial soil crusts play an important role in arid ecosystems and in stabilising dryland soils. Such arid regions are prone to extreme environmental conditions such as prolonged drought and short-lived intense rainfall and flood events, yet the impact of such events on cyanobacterial growth, and hence their role in landscape stability, is poorly-understood. This paper presents a series of laboratory experiments which determine cyanobacterial soil crust response to moisture and nutrient availability. Photosynthetic yield measurements indicate a rapid response in cyanobacterial response following hydration and suggest moisture content > 14% (c. 1.5 mm rainfall equivalent) is necessary to sustain such activity. The addition of nutrients did not trigger any significant increase in crust metabolic activity or photosynthetic response compared with deionised water over a 7-day period. However, over longer periods (> 4 weeks) nutrient-enriched rainfall promoted an increase in cyanobacterial metabolic growth measures (chlorophyll a and ‘greenness’) compared with deionised water. From the results we can infer that the magnitude and frequency of hydration from rainfall and flood events in arid regions play an important role in the maintenance of cyanobacterial soil crusts. Predicted changes in dryland hydrological regimes, for example changing frequency and intensity of rainfall in the Australian arid zone as a consequence of climate shifts, may therefore have an impact on the ability of cyanobacterial crusts to promote landscape stability.

[1] Iron-rich nanoparticles in aeolian mineral dust are of considerable importance to biogeochemical cycles. A major determinant of the chemical characteristics of nanoparticles is the parent sediment they are sourced from. The abrasion of dune sand has previously been shown to produce coarse dust (>1 � m) during the occurrence of aeolian saltation. In this study, Australian red dune sands were laboratory abraded and emission of particles 18–414 nm was observed throughout the experiment duration (� 1 h). The mean size of particles was 130 nm at the start of the test, but this gradually decreased to 110 nm at the end. The number concentration of particles approximately trebled over the course of the experiment with results suggesting that collisions between mobile sand grains led to the production of new nanosized particles over time. Chemical analysis revealed that these nanoparticles were highly abundant in iron, with some aluminium present. This chemical composition suggests that nanoparticles are produced from the clay coatings surrounding the parent sand grains. The study shows that abrasion from saltation occurring in Australian dune sands can release iron-rich nanoparticles, making them available for downwind transport during blowing dust events.

Soil erosion redistributes soil organic carbon (SOC) within terrestrial ecosystems, to the atmosphere and oceans. Dust export is an essential component of the carbon (C) and carbon dioxide (CO(2)) budget because wind erosion contributes to the C cycle by removing selectively SOC from vast areas and transporting C dust quickly offshore; augmenting the net loss of C from terrestrial systems. However, the contribution of wind erosion to rates of C release and sequestration is poorly understood. Here, we describe how SOC dust emission is omitted from national C accounting, is an underestimated source of CO(2) and may accelerate SOC decomposition. Similarly, long dust residence times in the unshielded atmospheric environment may considerably increase CO(2) emission. We developed a first approximation to SOC enrichment for a well-established dust emission model and quantified SOC dust emission for Australia (5.83 Tg CO(2)-e yr(-1)) and Australian agricultural soils (0.4 Tg CO(2)-e yr(-1)). These amount to underestimates for CO(2) emissions of ≈10% from combined C pools in Australia (year = 2000), ≈5% from Australian Rangelands and ≈3% of Australian Agricultural Soils by Kyoto Accounting. Northern hemisphere countries with greater dust emission than Australia are also likely to have much larger SOC dust emission. Therefore, omission of SOC dust emission likely represents a considerable underestimate from those nations' C accounts. We suggest that the omission of SOC dust emission from C cycling and C accounting is a significant global source of uncertainty. Tracing the fate of wind-eroded SOC in the dust cycle is therefore essential to quantify the release of CO(2) from SOC dust to the atmosphere and the contribution of SOC deposition to downwind C sinks.

The effects of blowing dust on transport operations are often mentioned as one of the significant impacts of aeolian processes on human welfare. However, few studies have been presented to demonstrate this impact. This research examined official air traffic incident reports in Australia for inclusively 1969-2010 to characterise the hazard of blowing dust to aviation in the country, the first such study of its kind. For the 42 year record, 61 incidents were identified (mean 1.4 per annum), with the large majority occurring in the first half of the 1970s. Only 20% of incidents occurred from 1984 onwards. Australian dust activity has not decreased over time, and the reduction in incidents is partly explained by improvements in aviation technology. The centralisation of Air Traffic Control operations to major coastal cities may however have reduced pilot reporting of dust-induced aviation incidents. By type of dust activity, dust storms were associated with nearly half of the reported incidents and dust hazes produced around a quarter. Only 5% of incidents resulted in any physical damage to aircraft and only one case involving personal injury was reported. The majority of the adverse effects on aviation due to dust (nearly 60% of reported incidents) were related to difficulties for navigation and completion of scheduled journey. Since aircraft damage and bodily harm were rare, the impact of dust in Australia is mostly that of inconvenience and associated raised economic costs. From 1990, the temporal pattern of incidents does not show any significant increase despite several intensely dusty years associated with recent droughts. This suggests that Australian aviation safety may be relatively resistant to the adverse effects of atmospheric dust as a hazard.

Soil erosion is an important component of the global carbon cycle. However, little attention has been given to the role of aeolian processes in influencing soil organic carbon (SOC) flux and the release of greenhouse gasses, such as carbon dioxide (CO2), to the atmosphere. Understanding the magnitude and mechanisms of SOC enrichment in dust emissions is necessary to evaluate the impact of wind erosion on the carbon cycle. This research examines the SOC content and enrichment of dust emissions measured using Big Spring Number Eight (BSNE) wind‐vane samplers across five land types in the rangelands of western Queensland, Australia. Our results show that sandy soils and finer particulate quartz‐rich soils are more efficient at SOC emission and have larger SOC dust enrichment than clay‐rich aggregated soils. The SOC enrichment ratios of dusts originating from sites with sand‐rich soil ranged from 2·1–41·9, while the mean enrichment ratio for dusts originating from the clay soil was 2·1. We hypothesize that stronger inter‐particle bonds and the low grain density of the aggregated clay soil explain its reduced capacity to release SOC during saltation, relative to the particulate sandy soils. We also show that size‐selective sorting of SOC during transport may lead to further enrichment of SOC dust emissions. Two dust samples from regional transport events were found to contain 15–20% SOC. These preliminary results provide impetus for additional research into dust SOC enrichment processes to elucidate the impact of wind erosion on SOC flux and reduce uncertainty about the role of soil erosion in the global carbon cycle

Soil carbon stores amount to 54% of the terrestrial carbon pool and twice the atmospheric carbon pool, but soil organic carbon (SOC) can be transient. There is an ongoing debate about whether soils are a net source or sink of carbon, and understanding the role of aeolian processes in SOC erosion, transport and deposition is rudimentary. The impacts of SOC erosion by wind on the global carbon budget, and its importance for carbon accounting remain largely unknown. Current understanding of SOC losses to wind erosion is based on the assumption that the SOC content of eroded material is the same as that of the parent soils. However, measured enrichment factors for the SOC content of Australian dusts relative to parent soils show that the SOC content of dusts can be up to seven times (by weight) larger than that of source-area soils, with enrichment factors ranging from 1.67 to 7.09. Assuming dust emissions from the continent of ~110 Mt yr 1 , SOC dust emissions would be 0.13–4.65 Mt SOC yr 1 without enrichment but 0.94–7.77 Mt SOC yr 1 with enrichment; which represents an uncertainty of around 60%. Representing SOC enrichment within dust emission models will reduce uncertainty in estimates of the impact of wind erosion on SOC flux and provide an approach for the inclusion of wind erosion processes in carbon accounting systems.

This study simulates how spatial variations in particle-size emissions from a playa affect bulk and size-resolved dust concentration profiles during two contrasting wind erosion events (a small local and a large regional event) in the Channel Country, Lake Eyre Basin, Australia. The regional event had higher dust concentration as a result of stronger frontal winds and higher erodibility across the playa. For each event, two emission scenarios are simulated to determine if measured size-resolved dust concentration profiles can be explained by spatial variability in source area emissions. The first scenario assumes that particle-size emissions from source areas occur at a uniform rate, while the second scenario assumes that particle-size emissions vary between and within source areas. The uniform emission scenario, reproduced measured bulk dust concentration profiles (R2 = 093 regional and R2 = 081 local), however simulated size-resolved dust concentration profiles had poor statistical fits to measured size-resolved profiles for each size class (the highest were R2 = 05 regional and R2 = 03 local). For the differential particle-size emission scenario, the fit to the measured bulk dust concentration profiles is improved (R2 = 097 regional and R2 = 083 local). However, the fit to the size-resolved profiles improved dramatically, with the lowest being R2 = 089 (regional) and R2 = 080 (local). Particle-size emission models should therefore be tested against both bulk and size-resolved dust concentration profiles, since if only bulk dust concentration profiles are used model performance may be over-stated. As the source areas in the first 90 m upwind of the tower were similar for both events, the percentage contributions of each particle-size class to total emissions can be compared. The contribution of each particle-size class was similar even though the wind speed, turbulence and dust concentrations were significantly different; suggesting that the contribution of each particle-size to the total emitted dusts is not related to wind speed and turbulence.

The dust storm on 22 and 23 September 2009, called “Red Dawn”, was the largest to pass over Sydney in term of reduced visibility (400 m) since reliable records began in 1940. The maximum hourly PM 10 concentration measured near Sydney was 15,366 μg/m 3 at Bringelly and is the highest ever recorded for Sydney and possibly any Australian capital city. The Australian air quality standard of 50 μg/m 3 per 24 h was massively exceeded at Randwick (1734 μg/m 3 ) and Newcastle (2426 μg/m 3 ). Red Dawn was caused by drought and the extreme wind conditions caused by a low pressure trough and cold front associated with a deep cut-off low pressure system. The source of the dust was the red sandplains of western New South Wales, the sandplains, riverine channels and lakes of the lower Lake Eyre Basin and Channel Country of Queensland. Between 22 September 2009 at 1400 and 23 September 2009, 0.3 Mt of PM 10 dust was transported off the coast between Albion Park and Newcastle (182 km length) near Sydney. The maximum hourly rate of PM 10 dust lost off the coast near Sydney was 71,015 t/h on 22 September at 2100. Calculating the total suspended particulate sediment lost off the Australian coast for the 3000 km long Red Dawn dust storm gives an estimate of 2.54 Mt for a plume height of 2500 m. This is the first and largest off-continent loss of soil ever reported using measured, as apposed to modelled, dust concentrations for Australia.

Episodes of high levels of particulate matter (PM) in Reykjavik occur several times a year. The main sources of daily variation in PM are traffic or highly localized (e.g. construction) sources, however several episodes have been identified where these are not the cause. Examining PM 10 (diameter 50–100 μg m −3 ; 30-min average), demonstrates that dust storms are the source of these increased levels of PM 10 . Since satellite coverage is sparse, visual confirmation of many such peaks in PM 10 cannot be achieved. The level of pollution measured in Reykjavik during dust storms indicates that at least 200 kg s −1 of PM 10 sized material is being eroded and transported away from sand plains ∼110 km away – this equates to an emission rate of 35 g m 2 h −1 . The source regions for dust storms in Iceland are the sandur areas on the southern coast of Iceland, and regions close to the glaciers. With climate warming, and fast retreating glaciers, the potential source regions in Iceland are rapidly increasing.

The dust cycle is an integral part of the Earth system. Each year, an estimated 2000 Mt dust is emitted into the atmosphere, 75% of which is deposited to the land and 25% to the ocean. The emitted and deposited dust participates in a range physical, chemical and bio-geological processes that interact with the cycles of energy, carbon and water. Dust profoundly affects the energy balance of the Earth system, carries organic material, contributes directly to the carbon cycle and carries iron which is vital to ocean productivity and the ocean-atmosphere CO2 exchange. A deciphering of dust sources, transport and deposition, requires an understanding of the geological controls and climate states – past, present and future. While our knowledge of the dust cycle, its impacts and interactions with the other global-scale bio-geochemical cycles has greatly advanced in the last 30 years, large uncertainties and knowledge gaps still exist. In this review paper, we attempt to provide a benchmark of our present understanding, identify the needs and emphasise the importance of placing the dust issue in the Earth system framework. Our review focuses on (i) the concept of the dust cycle in the context of global biogeochemical cycles; (ii) dust as a climate indicator; (iii) dust modelling; (iv) dust monitoring; and (v) dust parameters. The adoption of a quantitative and global perspective of the dust cycle, underpinned by a deeper understanding of its physical controls, will lead to the reduction of the large uncertainties which presently exist in Earth system models.

Australia does not have named dust transporting winds, like most other global dust source regions. Previous studies indicate that Australian dust is transported offshore via two dust paths to the southeast and northwest and that these dust paths are fed by three wind systems associated with the west–east passage of frontal weather systems across the southern half of the continent. This preliminary study uses 2 years of meteorological observations and mean sea level synoptic analyses to quantify the main weather systems and resultant wind systems responsible for dust entrainment and transport in the lower Lake Eyre. Of the 160 dust event days recorded in 2005 and 2006, 51% were associated with fronts and pre-frontal troughs; which generate pre-frontal northerlies, frontal westerlies and post-frontal southerlies that feed dust into the two dust paths. Heat troughs accounted for 24% of dust event days; with pre-trough northerlies and post-trough southerlies and westerlies from thunderstorms feeding the two dust paths. High pressure systems accounted for 22% of dust event days; with southeasterlies entraining most of the dust and low pressure systems account for only 3% of dust event days associated with variable winds. There is a distinct seasonality of dust entrainment; during late (austral) spring to mid summer in the north and extending to summer further south, driven by heating of the southern hemisphere in summer resulting in a poleward shift of fronts, troughs and pressure systems as spring and summer progress.

Sediments often occur as non-normal size distributions composed of discrete, partially aggregated particle populations. These populations reflect provenance, dispersal pathways and their depositional environments. Recent experimental laboratory studies describing mud flocculation in turbulent marine systems prompted this investigation of the potential of aggregates to record size-sensitive transport dynamics in a terrestrial fluvial system. Here, sediment-size distributions in their natural condition of particle–aggregate mixtures are analysed by parametric statistics. A practical and freely available decompositional approach is outlined and field tested, which allows sediment to be viewed in both its conventional particulate form and as its naturally occurring mixture of transport-stable aggregates and elementary particles. From a sequence of upward-fining slack water couplets in the Flinders Ranges, South Australia, it is demonstrated that the characteristics, provenance and depositional history of fine-grained sediments consisting of particle-aggregate mixtures can best be understood fully by quantifying aggregation.

The stability of many sand dunes and their interdunes is dependent on vegetation and surface crust cover. When this cover is removed, the sand can be activated and fine sediments deflated making the dunefields into sources of dust. This paper reports the impact of devegetation by wildfire on an interdune in the Simpson Desert, Australia. The fire occurred in 2001 and six years after the event pronounced differences between a pair of burnt and unburnt sites was clearly discernible. The variables examined included vegetation assemblage, cyanobacteria abundance and sediment aggregation, particle-size distribution and colour; but whether they apply to all such situations is uncertain. Rate of recovery has been slow and the differences are likely to have been sustained by a combination of negative feedback processes and climate.

Terrace remnants of late Pleistocene fine-grained valley-fill deposits (Silts) deeply entrenched by ephemeral traction load streams in arid areas remain a puzzle. They have been attributed to a variety of origins ranging from lacustrine to alluvial floodplains. We here report a centimetre-scale multi-proxy study of a 7 m section of Silts in the semi-arid Flinders Ranges of South Australia, which span the lead-up to and peak of the Last Glacial Maximum (LGM). The results of detailed lithostratigraphic mapping, high-resolution parametric particle-size analysis, Automated Mineralogy, induced magnetic susceptibility, carbon stable isotope geochemistry, and a chronostratigraphy based on 27 AMS radiocarbon and 6 luminescence ages are discussed in terms of sediment provenance, depositional environment and weathering history with the aim of reconstructing the regional palaeo-environment. The data are consistent with a fluctuating aeolian-fluvial interplay dominating the extended LGM environment with a greater impact on the landscape than all combined geomorphic processes since then. Accordingly, weathered slope mantles and loess accessions were eroded and entrained by numerous small and at least a dozen large-scale flood events, and trapped in an intra-montane floodplain extending into Brachina Gorge. Upstream of this narrow constriction, recurrent backflooding is discussed resulting in a thick sequence of layered to laminated slackwater couplets. Aggradation and degradation of valley-fills appear to be largely controlled by fine-sediment supply from the valley slopes, replenished by wind-blown dust from upwind playa lakes and source-bordering dunefields. In conclusion, this study demonstrates how dust storms and flooding rains can account for ‘pluvial’ features previously explained by the opposing effects of reduced precipitation and evaporation in the colder more arid glacial landscape of southern Australia.

Weather stations around the world record surface meteorological observations using the SYNOP coding system defined by the World Meteorological Organization (WMO). These codes are used for a variety of meteorological studies, along with remote sensing and modelling studies of wind erosion and dust transport. Despite the widespread use of SYNOP codes in wind erosion research and monitoring in Australia and internationally, few studies, if any, have examined in detail the manner in which the codes are recorded and archived, and how this might affect the quality of the data and the outcomes of the research. In this study we investigate how different methods of recording and archiving SYNOP codes relating to wind erosion and dust transport can under-estimate the frequency and inaccurately record the timing of wind erosion events. We examine 8 years of wind erosion data in the Lake Eyre Basin of central Australia (2000–2008) using more complete data from weather stations and compare them with the official archived dataset. On average, the number of dust days in the Lake Eyre Basin was under-estimated by 7% per year and the number of dust storm days (visibility

The entrainment, transport and deposition of aeolian dust are important processes affecting soil development at the margins of deserts. To assess accurately the impact of deposited aeolian dust on soil development, it is important not only to measure total dust deposition rates, but to distinguish additions of remotely and regionally sourced dust from locally derived material as well (which should not be viewed as new soil material as it is derived from aeolian re-mobilization of an existing soil). Because of the well-established relationship between dust particle-size and distance travelled from source, the particle-size distribution of deposited dusts can be used to identify the distance to probable source regions, in addition to identifying matching topsoil particle populations. Three dust traps were located along a transect of semi-arid south-eastern Australia, to measure aeolian dust deposition rates between late 2000 and late 2001. The particle-size distributions of selected dust deposits were measured and, with the aid of meteorological data, probable dust source regions determined. Particle-size distributions of the topsoils at each dust trap location were also measured to determine if any dust and soil particle populations matched. Although the sampling period was relatively short, and there was relatively little dust storm activity in this part of Australia during this time, a clear pattern of diminishing total dust deposition was measured downwind along the south-east dust path. Dust deposition rates were also moderate to low by global standards. Source regions of deposited dust were interpreted as being: (i) a combination of south-western and local sources; (ii) a combination of north-western and local sources; and (iii) a mixed source where dust was rained-out. The relative importance of these sources was correlated strongly with seasonal weather conditions, although the proportion of local dust in each deposit was greater at the arid (western) end of the transect. The effects of deposited dust on soil profile development are greatest at the western and central transect locations. At the western location, a fine-grained particle population distinctive of the south-western and north-western regional dusts and a coarse silt-sized particle population characteristic of local dusts, are also present in the topsoil, altering the texture of this Arenosol derived from dune sand. At the central location, where a Calcisol has formed in lacustrine lunette sediment, local dust of the same size as the dominant silt population of the topsoil continues to be deposited, while minor topsoil populations of very fine-grained silt match regional and long-distance dusts deposited at the site. Deposited dust appears to have been a less important soil development factor at the more humid eastern site because of the much smaller rates of dust deposition there. Nevertheless, a minor population of very fine silt particles in the Vertisol topsoil matches long-distance dusts deposited at the site, suggesting a small input of dust to this alluvial soil. The particle-size methodology used here has applications in other studies of dust contributions to peri-desert soils. In particular, particle-size distribution ‘smoothness’ may provide an indication of whether soils have simple or complex origins.

A review is presented of the aerosol-climate interaction with specific focus on the Australian region. The uncertainties associated with this interaction are much larger than those associated with greenhouse gases or other forcing agents, and are currently a major obstacle in climate-change research. However, new research suggests that aerosol effects are of comparable importance to greenhouse gases as a driver of recent climate trends in the Southern Hemisphere, including Australia. A significant new result from climate modelling is that anthropogenic aerosol over Asia affects meridional temperature gradients and atmospheric circulation, and may have caused an increase in rainfall over north-western Australia. Global ocean circulation provides another mechanism whereby aerosol changes in the Northern Hemisphere can affect climate in the Southern Hemisphere, suggesting an urgent need for further targeted studies using coupled ocean-atmosphere global climate models. To better model climate variability and climate change in the Australian region, more research is needed into the sources of aerosol and their precursors, their atmospheric distributions and transformations, and how to incorporate these processes robustly in global climate models (GCMs). The following priorities are suggested for further research in Australia linking aerosol observations and modelling: natural aerosol over the Southern Ocean, tropical biomass-burning aerosol in Indonesia and Australia, secondary organic aerosol (SOA) from volatile organic compounds (VOCs), wind-blown dust and modulation of rainfall by anthropogenic aerosol.

This paper describes the development and validation of the Australian Land Erodibility Model (AUSLEM), designed to predict land susceptibility to wind erosion in western Queensland, Australia. The model operates at a 5x5km spatial resolution on a daily time-step with inputs of grass and tree cover, soil moisture, soil texture and surficial stone cover. The system was implemented to predict land erodibility, i.e. susceptibility to wind erosion, for the period 1980-1990. Model performance was evaluated using cross-correlation analyses to compare trajectories of mean annual land erodibility at selected locations with trends in wind speed and observational records of dust events and a Dust Storm Index (DSI). The validation was conducted at four spatial length scales from 25 to 150km using windows to represent potential dust source areas centered on and positioned around eight meteorological stations within the study area. The predicted land erodibility had strong correlations with dust-event frequencies at half of the stations. Poor correlations at the other stations were linked to the inability of the model to account for temporal changes in soil erodibility, and comparing trends in the land erodibility of regions with dust events whose source areas lie outside the regions of interest. The model agreement with dust-event frequency trends was found to vary across spatial scales and was highly dependent on land type characteristics around the stations and on the types of dust events used for validation.

Environmental reporting and understanding of aeolian processes at different spatial and temporal scales require both extensive temporal and spatial data sources. The Bureau of Meteorology (BoM) SYNOP data have been used for environmental reporting in Australia by McTainsh and colleagues since 1998; however, with the current trend to replace meteorological observers with automated surface observation systems such as weather stations, these data sources are not sustainable. DustWatch was established to fill some of the gaps in the BoM network by strategically adding a community network of observers and instruments. Satellite imagery is also utilized when it is available. This paper outlines the nature of the DustWatch network, describes some of the educational and awareness outputs, outlines the types of data gathered and gives examples of how the data are being used both for environmental reporting and research into aeolian processes and activity. Copyright © 2008 John Wiley & Sons, Ltd.

The method for deriving a stage-discharge relationship has a significant impact on the shape of the river's rating curve. We compare rating curves for a single gauging station on a mutiple-channelled river in Australia compiled using three different methods – the Urban Runoff and Basin Systems (URBS) rainfall-runoff model, an empirically-based velocity-area method, and the predictive Hydrologic Engineering Centre-River Analysis System (HEC-RAS) computer model. The rainfall-runoff model was found to predict lower discharges for stage heights over 3.5 m than both the empirically-based velocity-area method and the HEC-RAS model. The empirically-based velocity-area model predicts similar discharges to the rainfall-runoff model for stage heights less than 3 m but much higher discharges for larger flood events. The HEC-RAS model predicts higher discharges than both other rating curves at all stage heights probably due to under-estimation of the impact of surface roughness on flow velocity. The three models are discussed with particular reference to their use on multiple-channelled rivers.

The recent upsurge in research attention to aeolian dust has shown that dust transport systems operate on very large spatial and temporal scales, and involve much larger quantities of sediment than was previously realized. An inevitable consequence of this is that researchers from a range of neighbouring disciplines, including ecology, are beginning to realize that this new knowledge has important implications for their study areas. In the present paper, we examine the ecological implications (real and potential) of this expanding knowledge of dust transport systems, with a particular emphasis upon the Australian dust transport system. We track these ecological effects from source to sink. At source, wind erosion–soil–vegetation relationships are often dominated by temporal changes in rainfall. Nine years of measurements in the Channel Country of the Lake Eyre Basin, Australia show that vegetation and soils in dune fields can recover from drought, whereas on inter-fluve grasslands uni-directional and negative successional vegetation changes can result from wind erosion during drought. On floodplains, both wind erosion and vegetation responses are complicated by flood frequency. Up to 1999 flooding of saline claypans did not increase vegetation but did increase wind erosion through the supply of alluvial fines. However, after three floods within as many months vegetation became established and wind erosion rates were dramatically reduced. Wind erosion research attention is now gradually turning from the physical to the organic content of eroded dusts. In Australia organic matter content can reach 65% by mass, but this cannot be explained by removal of soil organic matter alone. Biological soil crusts not only stabilize soils against wind erosion but contribute to some of the organic dusts. The role of dust as a vector for pathogens is an area which deserves greater research attention in the future. Downwind from source, we show that dust contributions to soils are more widespread and more variable (in time and space) than earlier work on dust-derived loess soils has suggested. Recent studies also show positive dust impacts upon nutrient budgets within distant forest ecosystems, and significant contributions to river nutrient loads, especially in the arid sectors of internally draining river basins. The number of studies of dust impacts upon marine ecosystems is increasing dramatically. Studies of dust within Antarctic ice cores combined with dust modelling provide compelling evidence that increased soluble iron-rich dust inputs to the Southern Ocean have stimulated phytoplankton populations. Modern process studies are, however, yet to clearly demonstrate these relationships. Finally we examine the potential for major dust impacts upon global climates, using its positive and negative effects upon solar radiation and precipitation as examples of the complexity and importance of this new research area.

This paper evaluates the influence of natural sand particle characteristics on the amount and particle-size distributions of dust produced by aeolian abrasion. It contrasts with previous studies of aeolian abrasion by conducting experiments using: (i) whole sand samples, as opposed to selected size fractions; (ii) natural, mature dune sands, rather than artificial or freshly crushed material; and (iii) weathered sands that have acquired a superficial clay coating, instead of grains with clean surfaces. Whilst previous research has found clear, positive relationships between particle size, sorting, roundness and the amount of dust produced by aeolian abrasion, the relationships determined in this study show some variation according to the geomorphological context from which the original samples were obtained. The most important factor affecting the amount and particle-size characteristics of the dust produced was the presence of a clay coating on the grain surface that is removed by the abrasion process. The dust produced by this mechanism had a modal size of 2–5 µm and material

Two sites on a playa (claypan) in south western Queensland, Australia were chosen to represent the variability in soil surface conditions known to control wind erosion and dust production in the region. The material was very fine and comprised of large amounts and different types of salts, high electrical conductivity, a propensity for slaking and the presence of cyanobacteria. The surfaces of 4 plots at each site were modified using in situ rainfall simulation and wind tunnel abrasion. The changes in the surface conditions were recorded using digital images and multi-angular spectral measurements of reflectance and inverted against a soil bi-directional spectral reflectance model. Optimised values of the model parameters produced the single scattering albedo (SSA) and a description of the scattering behaviour of the soil surfaces that included an estimate of microscopic roughness. The model parameters removed the effect of the measurement conditions (illumination and viewing geometry) on the spectral reflectance. Abrasion of the untreated surfaces demonstrated that the variability in the antecedent surface conditions played an important role in their response. Rainfall, drying and subsequent abrasion appeared to reset the soil surface conditions and controlled the spatial and temporal variation in the soil surface conditions. Redundancy analyses, conducted separately for SSA of selected wavebands, model parameter values and treatments elucidated the subtle and interactive effects of the treatments and surface responses. The results showed that high intensity rainfall and abrasion was associated with wavebands in the visible region and reduced roughness. Low intensity rainfall was associated with wavebands in the near-infrared and short-wave infrared regions and increased roughness. The analysis was interpreted as the result of eluviation due to rainsplash impact which caused size segregation and the preferential translocation of iron oxides to the surface and the creation of a thick surface seal and caused a thin crust which enabled the movement of salts and/or mineral clays to the surface because of the strong evaporation gradient. A poor relationship between aerodynamic resistance and microscopic roughness suggested that features of soil surface erodibility created by natural environmental processes such as rainsplash and wind erosion required a correction for macroscopic roughness. The values of the model parameters appeared to be insensitive to the directional nature of the abrasion process. The findings are significant for the development of this work towards an airborne or satellite-based assessment of soil surface erodibility and erosion.

We present AUSLEM (AUStralian Land Erodibility Model), a land erodibility modelling system that utilizes a rule-set of surficial and climatic thresholds applied through a Geographic Information System (GIs) modelling framework to predict landscape susceptibility to wind erosion. AUSLEM is distinctive in that it quantitatively assesses landscape susceptibility to wind erosion at a 5 x 5 km. spatial resolution on a monthly time-step across Australia. The system was implemented for representative wet (1984), dry (1994), and average rainfall (1997) years with corresponding low, high and moderate dust storm day frequencies. Results demonstrate that AUSLEM can identify landscape erodibility, and provide an interpretation of the physical nature and distribution of erodible landscapes in Australia. Further, results offer an assessment of the dynamic tendencies of erodibility in space and time in response to the El Nino Southern Oscillation (ENSO) and seasonal synoptic scale climate variability. A comparative analysis of AUSLEM output with independent national and international wind erosion, atmospheric aerosol and dust event records indicates a high level of model competency. (c) 2006 Elsevier B.V. All rights reserved.

On 7 February 2000 an atypical orange discolouration of snowfields in the central Southern Alps, New Zealand occurred following the passage of a cold front. Analysis of snow samples identified fine orangey-brown dust mixed with much coarser grey dust. Air parcel forward trajectories from dust sources in southern and central Australia, where dust storms were reported on 4 February 2000, were computed to identify the deposits source. Geochemical analyses of the dust deposit using 26 trace elements, unaffected by regional air pollution and gravitational sorting, indicate that 20% of the dust was sourced from western New South Wales, with 45% from the eastern Eyre Peninsula of South Australia and the remaining 35% was local New Zealand dust. This provenancing approach provides a spatial resolution of long travelled dust sourcing not previously achieved.

Widespread drought and record maximum temperatures in eastern Australia produced a large dust storm on 23 October, 2002 which traversed a large proportion of eastern Australia and engulfed communities along a 2000 km stretch of coastline from south of Sydney (NSW) to north of Mackay (Queensland). This event provided an opportunity for a study of the impacts of rural dust upon the air quality of four Australian cities.

The dust storm of 23 October 2002 covered most of eastern Australia and carried one of the largest recorded dust loads in Australia. In the 6 months leading up to the event, severe drought conditions in eastern Australia, plus above average maximum temperatures resulted in high potential evapo-transpiration rates, producing severe soil moisture deficits and reduced vegetation cover. Although increased wind speeds associated with a fast moving cold front were the meteorological driving force, these winds speeds were lower than those for the previously documented large dust storms. The dust storm was 2400 km long, up to 400 km across and 1.5-2.5 km in height. The plume area was estimated at 840,860 km 2 and the dust load at 0900 h was 3.35-4.85 million tones (Mt). These dust load estimates are highly sensitive to assumptions, regarding visibility-dust concentration relationships, vertical dust concentration profiles and dust ceilings. The event is examined using meteorological records, remote sensing and air quality monitoring. (C) 2004 Elsevier Ltd. All rights reserved.

This paper describes a series of tests designed to evaluate the capacity of a personal computer (PC) based statistical curve-fitting program called MIX to quantify composite populations within multi-modal particle-size distributions. Three natural soil samples were analysed by a Coulter Multisizer, and their particle-size distributions analysed using MIX software to identify the modes, standard deviations and proportions of their composite populations. The particle-size distributions of the three natural soil samples were then numerically combined in equal proportions using a spreadsheet program to create synthetic particle-size distributions of known populations. MIX was then tested on the synthetic particle-size distributions to see if the modes and proportions it identified were similar to those modes and proportions known to characterize the synthetic particle-size distributions. The main outcome is that MIX can very accurately describe the modal particle size and proportions of the major composite populations within a particle-size distribution. However MIX has difficulty in identifying small populations (those contributing

Mean-sea-level-pressure patterns of the main atmospheric circulation for Australia were created using principal component analysis and non-hierarchical cluster analysis. The patterns are related to dust storm occurrence from 95 meteorological stations across Australia during the period 1960–99. Dust storm stations were separated into two groups with distinct dust storm seasons: the spring–summer (September–February) dust storm group and the summer–autumn (December–May) dust storm group. Spring–summer dust storms are most likely controlled by the timing of non-precipitation cold fronts over southern and central Australia and limited by summer precipitation. The summer–autumn dust storms are most likely controlled by the length of the driest period of the year. The stations of the first group are located mainly in the interior of the continent, and those of the second group are located mainly near the coastal regions of southern and western Australia. The location of the subtropical Indian Ocean high is shown here to influence dust storm occurrence during both seasons. A more westward displacement of this pressure centre in the Great Australian Bight allows cold fronts to enter the continent and increase the potential for dust storm activity. Copyright © 2004 Royal Meteorological Society

A series of experiments was conducted to determine the potential for aeolian abrasion of natural dune sands to produce fine particles (< 125 µm) by (1) the release of resident fines; (2) spalling, chipping and breakage of particles; and (3) the removal of grain surface coatings. Parent samples were obtained from the surfaces of four active continental dunes and abraded using a glass 'test tube' chamber for up to 120h. The fine particles produced by this abrasion process were trapped at varying time intervals and subject to detailed particle-size analyses using a Coulter Multisizer. The abrasion of untreated parent samples produced fine particles in one of two main size classes, 50 µm, but when the parent sample was sieved to exclude particles 63 µm) was dominant during the first 16 h of abrasion, then became less significant and is thought to be associated with the release of resident fines into suspension. The finest mode (

Over the past 10 to 15 years there has been a rising interest in interactions between aeolian and fluvial processes from geomorphologists and sedimentologists. This reflects recognition of the limitations of a reductionist perspective examining single process systems in understanding landform and landscape development. This paper focuses on the rise of aeolian-fluvial interaction research in dryland environments. We first explore the background to the contemporary situation then review existing research on aeolian-fluvial interactions at global/regional and local scales. From this review it is suggested that landscape sensitivity, or the effectiveness of links between the process systems, spatial environmental transitions and temporal environmental change are the three main driving forces determining the geomorpho-logical significance of aeolian-fluvial interactions. The importance of the first two of these driving forces is explored in more detail using Australia as a case study. We conclude by highlighting some future possible research directions in this field.

Dust raising and transport are common and important processes in Australia today. The aridity of the Australian continent and high climatic variability result in widespread dust raising in the arid and semi-arid areas and transport to the humid margins and surrounding oceans. The supply of erodible particles appears to be the greatest limitation on total flux of transported dust. Dust raising is greatest in the Lake Eyre Basin, including the Simpson Desert, and Murray-Darling Basin where internal drainage renews supplies of fine particles to the arid zone. In the west and northwest dust entrainment is low, despite considerable aridity. The marine record of dust flux shows at least a threefold increase in dust flux, compared with the Holocene, in the last glacial maximum in both tropical and temperate Australia, driven by weakened Australian monsoon rains and drier westerly circulation, respectively. Despite the widespread confirmation of aeolian dust deposits in southeastern and southwestern Australia, dated or quantified records are extremely rare. The dominant model of Australian dust deposits, the clay-rich ‘parna’, is shown to be poorly substantiated while modern and ancient dust deposits examined in detail are shown to bear a strong similarity to conventional definitions of loess.

The sampling frequency in space and time is often inadequate to estimate the accuracy and precision of aeolian sediment transport. The problem stems from a lack of knowledge about the spatial and temporal scale of variation in aeolian transport and is compounded by a shortage of resources (aeolian sediment traps and labour). This study developed a geostatistical methodology for estimating sediment transport at unsampled locations and tested the extent to which it was dependent on sampling networks (nested, grid and random) and frameworks (mobile or static sampling framework between wind erosion events). Aeolian transport data were collected in an area of Australia influenced by wind erosion (Diamantina Lakes National Park, southwestern Queensland) to evaluate the combination of events used for mapping transport. Insufficient wind erosion events occurred to test sediment sampling strategies and hence simulated sampling was conducted using maps of sediment transport produced with existing models of aeolian sediment transport in the same study area. Independent validation data were used to test the estimation performance. The results suggested that sampling networks that did not include information on the spatial scale of variation (i.e. grid and random sampling) did not represent adequately the sediment transport population. In contrast, a bespoke nested sampling network performed consistently better than the other networks. Overall the static framework with a nested network was recommended for estimation and mapping of sediment transport with few resources and was likely to be especially important for use over large areas. This approach has the advantage of requiring only a single pooled within-event variogram for sediment transport to be used to derive the model parameters for kriging or stochastic simulation for each event. Copyright © 2003 John Wiley & Sons, Ltd.

Little is known about the spatial and temporal scales of variation in aeolian processes. Studies that aim to investigate surface erodibility often sample aeolian sediment transport at the nodes of a regular grid of arbitrary size. Few aeolian transport investigations have the resources to obtain sufficient samples to produce reliable models for mapping the spatial variation of transport. This study reports the use of an innovative nested strategy for sampling multiple spatial scales simultaneously using 40 sediment samplers. Reliable models of the spatial variation in aeolian sediment transport were produced and used for ordinary punctual kriging and stochastic simulated annealing to produce maps for several wind erosion events over a 25 km 2 playa in western Queensland, Australia. The results support the existence of a highly dynamic wind erosion system that was responding to possibly cyclic variation in the availability of material and fluctuations in wind energy. The spatial scale of transport was considerably larger than the small scale expected of the factors controlling surface erodibility. Thus, it appears that transport cannot be used as a surrogate of erodibility at the scale of this investigation. Simulation maps of transport provided considerably more information than those from kriging about the variability in aeolian sediment transport and its possible controlling factors. The proposed optimal sampling strategy involves a nested approach using ca 50 samplers. Copyright  2003 John Wiley & Sons, Ltd.

Thirty-seven days of PM 10 aerosol samples (particles with aerodynamic diameter

AEolian processes have been regarded as having little relevance to pedogenesis in the subhumid regions of eastern Australia, due perhaps to a perceived paucity of clear evidence of dust deposition and to difficulties of measuring an aeolian dust component within soils. Contrary to earlier opinions, an aeolian soil component may occur in eastern Australia, as appreciable amounts of dust are deposited annually. We report dust deposition rates and some dust characteristics at Gunnedah, and measured granulometric, mineralogical and geochemical attributes of four soil profiles found in different physiographic areas of the Namoi Valley. Estimates of dust deposition rates indicate that a deposit at least 20 cm thick could have formed over the last 13,000 years. The soil profile which most clearly indicates the presence of dust overlies basalt at Bald Hill. Here, the topsoil contains a conspicuous population of particles with a modal diameter of 40–50 μm and has been enriched in Si by the addition of quartz, which cannot have originated from the basalt or from colluvial or alluvial processes. A clayey floodplain soil profile (Boonawa) also contained a large dust-particle population and also illite and moderate concentrations of K of possible aeolian origin. Two sandy profiles at Round Swamp displayed the same conspicuous dust-particle populations, and one exhibited an interstratified illite–smectite component, suggesting dust additions. Local aeolian processes were also indicated by the well-sorted, coarse sand-sized particles of the Round Swamp East profile, located on a low lunette adjacent to the swamp. These fine-grained, quartz-rich, aeolian dust deposits differ considerably from the benchmark Australian aeolian dust mantles, which form the clay-aggregated, calcareous parna soils of southern New South Wales.

Dust storms are a major contributor to soil erosion in inland Australia, and the Simpson Desert-Channel Country region is one of the most active wind erosion regions. While information is available on wind erosion rates at the land-type level, little is known about the influence spatial variations in the erodibility within a land-type has on the resulting dust concentration profile. A Gaussian plume model, DSIS, is presented along with tower-based dust data, to describe the influence of different spatial combinations of dust sources areas, during three dust events on the Diamantina River flood-plain in Western Queensland, Australia.