Particle-size characteristics of the vertical dust profiles of two contrasting dust events in the Channel Country of western Queensland, Australia

Spatial and temporal variations in vegetation and soil surface conditions of rangelands add a level of complexity to wind erosion processes which is often difficult to model or measure. Butler and colleagues have developed a methodology which combines computer simulation and experimental measurement to analyse how spatial and temporal changes in dust source area emission rates and atmospheric conditions affect vertical dust concentration profiles during wind erosion events in the Queensland Channel Country. This methodology has not, however, taken into account how variations in dust source area particle-size can affect vertical dust concentration profiles. The present paper examines how the particle-size characteristics of dust source soils affect both vertical dust concentration profiles and the vertical distribution of particle-sizes in two contrasting wind erosion events in the Queensland Channel Country. Comparisons are made between computer simulations of these events and the results of field measurements (of vertical dust concentration profiles) and laboratory measurements (of dust particle-size). Computer simulations of the particle-size emissions from the different dust source areas during the two events produce vertical distributions of dust particle-sizes which are similar to the measured dust particle-sizes for these events. These results indicate that erodibility-induced spatial and temporal variations in particle-size emissions of dust source areas have important influences upon: dust fluxes, vertical dust concentration profiles and the vertical distribution of dust particle-sizes within these profile

Caring for our country: wind erosion extent and severity maps for Australia, final report

The Wind Erosion Extent and Severity Maps (WEESMAP) project for Australia has been completed. As a result of the project significant improvements were made to both the soil and vegetation input data. These improvements include: • A new dynamic erodibility mask was created for the model,based on Fractional Cover Index (FCI) of Guerschman et al. (2009). • Increasing the soil descriptions available from 12 to 29 soils. • Replacing LAI GIS layer with the MODIS LAI layer, which no longer uses empirical relationships developed for AVHRR NDVI product. • The model was extend to a 10km resolution for the whole of the continent. Statistical comparison of the CEMSYS model before (Version 5) and after the soil/vegetation improvements (Version 6) shows that the model over estimated daily dust concentrations at 26 of the DustWatch nodes in 2009 by approximately 3 fold for V5 and underestimated it by 0.6 for V6. The mean error between modelled and observed dust levels was reduced for V6 (0.0227 to 0.0084). Finally V6 explained twice the level of variability in the observed data compared to V5 (0.2292 to 0.3956). Given the result was comparing 26 stations over 365 days, V6 appears extremely robust over the yearly period. In addition, the time series of available data was extended significantly. At the end of the project data the following data is available: • Version 650 km data is available from March2000–June2012. • Version 510 km dat is available for NSW/Victoria from February2000–June2012. • Version 610 km data is available nationally for 2002,2008,and 2009. Finally several other coding improvements were made to the model to increase performance. Consequently, it is now possible to produce 50 km and 10 km maps within 10 days of the external MODIS and Atmospheric data becoming available. This means it is now possible to use the CEMSYS in monthly reporting products

Effects of cyanobacterial soil crusts on surface roughness and splash erosion

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Soil surface roughness (SSR) modifies interactions and feedback processes between terrestrial and atmospheric systems driven by both the abiotic and biotic components of soils. This paper compares SSR response to a low intensity multi‐day rainfall event for soils with and without early successional stage cyanobacteria‐dominated biological soil crusts (CBCs). A rainfall simulator was used to apply 2 mm, 5 mm and 2 mm of rain separated by a 24‐hour period over 3 days at an intensity of 60 mm hr‐1. Changes in SSR were quantified using geostatistically‐derived indicators calculated from semivariogram analysis of high resolution laser scans. The CBCs were stronger and splash erosion substantially less than from the physical soil crusts. Prior to rainfall treatment soils with CBCs had greater SSR than those without. The rainfall treatments caused the physical crusted soils to increase SSR and spatial patterning due to the translocation of particles, soil loss and the development of raindrop impact craters. Rainfall caused swelling of cyanobacterial filaments but only a slight increase in SSR, and raindrop impact cratering and splash loss were low on the soils with CBCs. There is no relationship between random roughness and splash erosion, but an increase in splash loss was associated with an increase in topographic roughness and small‐scale spatial patterning. A comparison of this study with other research indicates that for rainfall events up to 100 mm the effectiveness of CBCs in reducing soil loss is >80% regardless of the rainfall amount and intensity which highlights their importance for landscape stabilization

Modelling wind erosion at national and regional scale using the CEMSYS model: national monitoring and evaluation framework, prepared for the National Land & Water Resources Audit

This document examines the application of the CEMSYS wind erosion and dust transport model as a means of monitoring the impact of wind erosion at national and regional scale. In its current form CEMSYS takes into consideration the atmospheric conditions (wind speed, rainfall etc.) and land surface (soil type, vegetation cover etc.) and estimates wind erosion quantities such as sand flux and dust flux. Other wind erosion related quantities, such as deposition rates, net erosion (sand + dust flux – deposition) threshold friction velocity, and friction velocity are calculated. These quantities can be averaged on an hourly, daily, monthly, or yearly basis. This trial of the CEMSYS model looks at its application to the Australian mainland and area of NSW bounded by 139 to 146E and 31 to 37S. The following topics are covered: •description of CEMSYS •application of CEMSYS on an event, monthly and yearly basis •description of the modelling products that can be used by end user products for reporting proposes •limitations of the CEMSYS model •linkages of the CEMSYS output to other approaches outlined above

Towards a simple Gaussian model to describe multiple source areas during wind erosion events

[Abstract]: Wind erosion is a broad-scale process in inland Australia. When conditions are conducive to wind erosion, dust storms can entrain fine sediment over large areas of the continent, however closer examination indicates that the dust source areas are often spatially discrete. The fine sediment entrained from these sources, is transported as dust plumes, which may coalesce at some point downwind. While some progress has been made in estimating the dust load in these plumes [Knight et. al. 1995], the accuracy of these estimates is limited by the size and shape of the source region assumed. In addition, soil loss per unit area is a more appropriate measure of soil erosion than total plume load, but estimating loss per unit requires accurate estimation of source areas. The new model developed hopes to overcome these limitations by working from the source area downwind, rather than back-tracking to estimate the source area as done by Knight et al. [1995]. As a result of this, the new model is quite distinct from that of Knight et. al. [1995], in that it no longer assumes that entrainment is uniform across a single source area, and consequently that the concentration profile is uniform across the source area. The new model uses a Gaussian plume model [Zannetti 1990], with the dispersion parameters based on the Hann et. al. [1982] estimates for rural areas. As a first approximation, the model describes dust loads emanating from sources of different strength and spacing along a crosswind line. This configuration is indicative of spatially discrete sources, with different soil erodibility and cover protection, producing different source strengths. Initial results from the model indicate that the nature of the downwind dust concentration profile is dependent on the following factors: downwind distance from source; source strengths; and crosswind source separation. A detailed discussion of the relationship between the above factors is presented. As a result of this discussion a number of conjectures are made about the nature of the physical system

Sources and pathways of dust during the Australian “Millennium Drought” decade

This paper was accepted for publication in the journal Journal of Geophysical Research: Atmospheres and is also available at http://dx.doi.org/10.1002/2016JD025737.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

High resolution provenancing of long travelled dust deposited on the Southern Alps, New Zealand

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. (c) 2005 Elsevier B.V. All rights reserved