Grant McTainsh
Atmospheric Environment Research Centre (AERC),Griffith School of Environment,
Griffith University, Brisbane, Queensland,
Australia
Wind erosion, dust and their environmental impacts: an Australian perspective
AIMS OF THIS PAPER
I Brief overview - wind erosion and dust
III Examine the DustWatch Australia approach to monitoring and understanding wind erosion/dust processes
IV Comment on future monitoring and research challenges
II Describe the Australian wind erosion/dust setting
I Overview - wind erosion and dust
Wind erosion removes soil particles/aggregates, reducing soil fertility and soil moisture storage capacity
Eroded dust is “lost” and on-ground evidence is subtle
Sand deposits provide very tangible evidence of erosion
Sand deposit in cattle yards following erosion on the Hay Plain, NSW
Dust blowing from cultivated soil
Continental dust emissions (red bars), transport (arrows) and deposition rates (blue arrows)
Source: Shao, Y, Chappell, A, Huang, J, Lin Z, McTai nsh, G, Mikami, M, Tanaka, T, Wang, X, Wyrwoll, K-H, Yoon S. (2011). “Dust Cycle: An Emerging Core Concept in Earth System Science”. AEOLIAN RESEARCH, 2, 4, 181-204.
Global environmental significance of dust is better understood from modelling
Australia is not a major
dust continent
II The Australian wind erosion/dust setting
(Photo: Mark Coombe 2004 www.outbackpics.com)
Australia: dry in the centre and wet around the margins…. (except the west)
General spatial relationship (inverse) between rainfall and wind erosion
Why is there less wind erosion* in the west ? - more later…..
* Dust Storm Index (DSI) – more on this later
Rainfall Wind Erosion
Wind erosion rates* are very sensitive to rainfall
Dust transporting weather and wind systems
Dust storms are associated with cold fronts* passing west to east across the continent
Each cold front has 3 dust wind systems:
1. Prefrontal Northerlies
2. Frontal Westerlies
3. Post-frontal Southerlies
* Strong C, Parsons K, McTainsh G, & Sheehan A. (2010) “Dust transporting wind systems in lower Lake Eyre Basin Australia”. AEOLIAN RESEARCH doi:10.1016/j.aeolia.2010.11.001
Frontal westerlies produce Haboob dust storms
Haboob at Wagga Wagga, NSW
Haboob at Nappa Merrie station, SW Qld
Downdraft thunderstorms can alsoproduce Haboobs – but rare
Dust Transport Paths
Dust paths exit the continent to the East and NW
Australian dust in NZ snow
Dust storms transport large dust loads
February 1983 dust storm,
Melbourne = ~ 2 Mt *
December 1987 dust storm,
Brisbane = 5.5 - 6.3Mt *
* Raupach, M, McTainsh, G and Leys, J. (1994)“Estimates of dust mass in some recent major
Australian dust storms”. AUSTRALIAN JOURNAL OF SOIL AND WATER CONSERVATION, 7(3), 20-24.
* Knight, A.W., McTainsh, G.H. and Simpson, R.W. (1995). “Sediment loads in an Australian dust storm: Implications for present and past dust processes”. CATENA 24, 195-213.
Dust loads (Cont.)
October 2002 dust storm = 4.85Mt * September, 2009 “Red Dawn” dust storm = 12.1 to 17.5 Mt * and 2.54 Mt transported offshore **
.
* McTainsh G, Chan.Y, McGowan H, Leys,J. and Tews E. (2005) “The 23rd October, 2002 dust storm in eastern Australia: characteristics and meteorological conditions”. Atmospheric Environment 39, 1227-1236 * Strong, C – pers. comm. (2011) ** Leys, J – pers. comm. (2011)
A general spatial relationship between the dust paths and distributions of kaolinite in marine sediments
Marine impacts of Australian dust
Dust deposition offshore has made major contributions to marine sediments
Gabric et al (2002) correlated dust activity (DSI) in southern Australia with SeaWiFS aerosol optical depth (AOD) – a dust proxy, and chlorophyll (CHL) – a phytoplankton proxy in sub-polar SO waters.
Monthly Averaged SeaWifs Data
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CHLMonthly Dust Storm Index in southern Australia
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Comment: While there is a correlation causality was not established.
Gabric, A.J., Cropp, R., Ayers, G.P., McTainsh, G.H. and Braddock, R.D. (2002) “Coupling between cycles of phytoplankton biomass and aerosol optical depth as derived from SeaWiFstime series in the sub antarctic Southern Ocean”. GEOPHYSICAL RESEARCH LETTERS, 29, 10.1029/2001GLO13545
Marine ecosystem impacts of Australian dust
Boyd et al (2004) tracked 6 dust plumes into the SO using HYSPLIT to compare with SeaWiFS CHL patterns. No clear relationships emerged.
Comment: Study was based upon the simplistic hypothesis that any dust plume over the SO could cause a phytoplankton bloom. More information is needed on spatial and temporal changes in dust characteristics…..
Boyd, P.W., McTainsh, G.H., Sherlock, V., Richardson, K., Nichol, S, Ellwood, M and Frew, R.. (2004) “Episodic enhancement of phytoplankton stocks in New Zealand subantarctic waters: contribution of atmospheric and oceanic iron supply”. GLOBAL BIOGEOCHEMICAL CYCLES 18, GB1029, doi:10.1029/2002GB002020,2004
A work in progress…………
III DustWatch Australia: monitoring and research methodologies
DustWatch Australia is a suite of wind erosion and dust methodologies andnetworks, comprising:
1. Dust event database (DEDB)2. DustWatch Observer Network3. DustWatch Nodes4. CEMSYS – a continental wind erosion model
DustWatch Australia is a resource for:
- Environmental audits- Research- Community awareness raising
As our understanding of the on-site and off-site effects of wind erosion (iedust) increases the need for long term monitoring becomes greater
BoM dust-related weather codes:
06 = dust haze (dust in suspension) 07 = local dust (raised dust or sand) 08 = local dust event (Willy willy or dust devil) 09 = dust storm - distant or in past hour30 = moderate dust storm - decreased in past hour31 = moderate dust storm - no change in past hour32 = moderate dust storm - increase in past hour33 = severe dust storm - decreased in past hour34 = severe dust storm - no change in past hour35 = severe dust storm - increased in past hour98 = thunderstorm with dust storm
Bureau of Meteorology (BoM) records of “weather phenomena”provide data on wind erosion events across Australia.
These records cover long time periods: since 1960 (127 stations), since 1942 (33 stations) and archival records extend into the C19.
Data are held in a Dust Event Database (DEDB) at Griffith University.
1. Dust event database (DEDB)
Dust Storm Index (DSI)
DSI is a composite measure of wind erosion event frequency and intensity.
Event intensity is measured using a composite measure of the contributions of: local dust events, moderate dust storms and severe dust storms using weightings for each event type, based upon visibility reduction for each event type.
McTainsh, G.H. (1998). “Dust Storm Index”. In: SUSTA INABLE AGRICULTURE: ASSESSING AUSTRALIA’S RECENT PERFORMANCE. A report of the National Collaborative Project on Indicators for Sustainable Agriculture. SCARM Technical Report 70, 65-72.
( ) ( )[ ] i
n
1i
LDE0.05DSSDS5DSI ∑=
×++×=
Where:DSI = Dust Storm Index at n stations where i is the ith value of n stations for i=1 to n. n = The total number of stations recording a dust event in the time period.SDS = Severe dust storm (daily maximum weather codes: 33, 34, 35)DS = Dust storm (daily maximum weather codes: 09, 30, 31, 32 and 98)LDE = Local dust event (daily maximum weather codes: 07 and 08)
1. Few stations in arid/semi-arid regions produce spatial data interpolation problems
2. Variations in BoM observation frequency must be considered when interpreting patterns
DSI maps provide information on continent-wide wind erosion over 50 years (1960-2010) but:
DEDB: a resource for environmental audits
Long time series (1960 - 2010) are valuable for environmental audits
Inter-annual variability is drought-driven
= drought = very wet years
Extremely high wind erosion rates (DSI) in the 1940s
A wind erosion audit of the 1940s (“Dust Bowl” years) and the 2000s *
* McTainsh G, Leys J, O’Loingsigh T & Strong C. [2011] Australia; State of the Environment – wind erosion (in press)
Tree roots exposed by wind erosion in the 1940s
Land management has improved significantly - but has climate also changed ?
7.831.218%2.011.4Mean Decadel DSI
6.720.831%1.54.9III WA Rangelands(Kalgoorlie, Port Hedland,WA)
11.427.540%4.09.9II Central Australia (Alice Springs, NT & Ceduna, SA)
5.545.39%1.719.5I Eastern Australia(Charleville, Qld & Wagga Wagga, NSW)
2000s MaxDSI
1940s MaxDSI
% of 40s
2000s Mean DSI
1940s Mean DSI
Name
II
IIII
Wind erosion during the 1940s was much higher (almost) everywhere than in the 2000s
NOTE: very active dust transport through E. Aust coastal stations
Small number of BoM stations in 1940s precludes spatial interpolation of DSI
Dust Transport Sectors provide useful indicators of dust source regions
Clear inverse relationship between rainfall and DSI - but a large data scatter < 500mm
All stations 1960-2008
R2 = 0.65
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SI
DEDB: a research resource (an example)
To what extent does this relationship reflect environmental (climate and
sediment supply) or land management factors (grazing and mining)?
Western Plateau (WP)Western Plateau(WP) Murray-Darling Basin (MDB)
Lake Eyre Basin (LEB)
Environmental and land management factors vary between 3 major regions
Erosion drivers:• Climate - similar (Pacific Ocean climate system)• Sediment supply - similar (internally-draining rivers)• Land management – similar (cattle grazing)
Erosion comparison:• Relative Erosion Rate (RER) of the LEB is ~1.6 times higher than MDB• Erosion Response Curves (ERC) of the MDB and LEB are similar
LEB - MDB Region Overlay
MDB
R2 = 0.56
LEB
R2 = 0.36
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Rivers feed silts and clays to:
- Floodplains
- Clay pans (playas)
- Lakes
Sediment supply by internally-draining rivers to dust source areas
Erosion comparison:• Erosion Response Curve of WP - much flatter• Relative Erosion Rate of WP - 50% of LEB
LEB - MDB - WP Region Overlay
MDB
R2 = 0.56
LEB
R2 = 0.36
WP
R2 = 0.04
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Erosion drivers:• Climate – different (Indian Ocean climate system)• Sediment supply - low (no internally-draining rivers) • Land management – variable (no cattle grazing - but mining produces localised
v. high erosion rates, reflected in v. low R2)
LEB
MDB
WP
Fig. 6.1 Main Australian river systems
Sediment supply in Western Plateau (WP) low because no organised river systems
WPLEB
MDB
Land management in WP – almost no grazing, because no surface water
With less vegetation reduction from grazing, wind erosion rates in the WP may be close to “natural” ? – a rare occurrence
Pattern of pastoral properties from a DustWatch survey
No pastoral properties over large areas Mainly indigenous protected areas
2. DustWatch Observer network
The DustWatch Observer Network is intended to address:- low density of BoM stations- the increasing numbers of BoM stations are becoming automated
Network set up (2002) in NSW, then nationally (2004)
More successful in NSW:
- institution-based(Office of Env. & Heritage)
- partly linked to instrumentation (DustWatchNodes)
Are DustWatch webcams the future ?
National network difficult to maintain because:
- infrequency of events makes it difficult to maintain DustWatcher interest
- ongoing funding for “monitoring” is a problem
DustWatch Observer network
Stormchasing.com.au
3. DustWatch Nodes (instrumented DustWatch sites)
A dust monitoring network was started in E. Australia in the 1980s
Network operation was intermittent due to funding constraints for “monitoring”
High volume air samplers
Dust deposition traps
DustWatch Nodes were established in NSW by John Leys (2005) –with state funding * and are being expanding nationally – with federal government funding **
* NSW Office of Env & Heritage** Department of Agriculture, Fisheries and Forestry (DAFF) - Caring for Our CountryProgram
DustTraks®:
PM10 dust concentration
Differentiate dust fromsmoke and fog
Data at 1 minute intervals (when > 25ug/m3 dust)
15 minute intervals (when < 25ug/m3 dust)
The Buronga DustWatch Node (High Volume Air sampler) has the longest rural dust concentration record in Australia (1990 – present)
* Acknowledgements to Michael Case (NSW Office of Env. & Heritage) for filter collections and instrument support
*
Buronga, NSW
DSI - dust concentration relationship *
DSI from Mildura BoM site & dust concentration from nearby Buronga DustWatch Node
1990/91 to 2003/04 - dust storm years
R2 = 0.93
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Total Dust Concentration (µgm-3
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1990/91 to 2009/10 - dust storm years
R2 = 0.60
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Relationship is very good up to2003/4, but then deteriorates …why ?
* More on this in John Leys talk – this conference
Relationship between visibility and dust concentration allows DEDB records to be converted into dust concentrations (rather than DSI) – more physically meaningful measure *
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Visibility-dust concentration relationship – Mildura (BoM) and Buronga (HVS)
* Wind erosion histories (50 years) of 121 stations are based upon this relationship
www.dustwatch.edu.au
4. CEMSYS
The Computational Environmental Modelling System (CEMSYS) of Shao and Leslie (1997)* is the Australian standard** for modelling wind erosion.
* Shao Y and Leslie LM, 1997: Wind erosion Prediction over the Australian Continent. J. Geophys. Res 102, 30,091-30,105
CEMSYS is an important component of DustWatch Australia – run by Harry Butler (University of Sth Queensland)
CEMSYS and DSI wind erosion maps 2007-08
CEMSYS maps correlate reasonably well with DSI maps in central and eastern Australia
CEMSYS appears to over-predict wind erosion in western Australia - but low density of BoM stations limits the accuracy of the DSI maps
Most global dust models over-estimate dust emissions from Western Australia – e.g Tanaka and Chiba (2006)
Tanaka, T. Y. and Chiba, M.: A numerical study of the contributions of dust source regions to the global dust budget, Glob. Planet. Change, 52, 88–104, doi:10.1016/j.gloplacha.2006.02.002, 2006.
CEMSYS event-based dust load estimates * correlate well withDEDB derived estimates **
** McTainsh, G.H., Chan. Y.C., McGowan, H.A., Leys, J.F. and Tews, E.K.(2005) The 23rd October, 2002 dust storm in eastern Australia: characteristics and meteorological conditions. Atmospheric Environment 39, 1227-1236.
* Shao, Y., J. F. Leys, G. H. McTainsh, and K Tews (2007) Numerical simulation of the October 2002 dust event in Australia,JOURNAL OF GEOPHYSICAL RESEARCH, 112, D08207, doi:10.1029/2006JD007767.
Modelled dust load of 23 October, 2002 dust storm is 5Mt, compared with 4.85Mt from DEDB data
IV Comments on future monitoring and research challenges
#1 Long term environmental monitoring programmes are vital to the sustainable management of our planet
A “motherhood statement”…… but governments are slow to learn *
An Australian example ……
Central Australia has ideal locations, BUT efficiency of solar cells is reduced by dust deposition (on to panels) - BUT few data are available.
IF the dust deposition monitoring network set up in 1980s had received ongoing funding the data would be available now !
Global warming is increasing the need for solar power
* The funding of DustWatch Australia by the Department ofAgriculture, Fisheries and Forestry - Caring for Our Country
Programme is a notable exception
#2 We need to remove the institutional divide between “monitoring” and “research”
Government environmental agencies traditionally “do monitoring” and research establishments “do research”. This divide needs to be removed…………..
DustWatch Australia is the result of Leys and McTainsh overcoming this divide over 25 years and the recent support from the Aust. Government “Caring for Our Country
Programme” (C4oC). *
This divide is starting to be removed elsewhere in Australia:
- Centre for Aust. Weather & Climate Research (CAWCR) brings together CSIRO and the BoM
* Much of the credit for C4oC funding goes to Dr Michele Barson for having the foresight to recognise the value of long term monitoring of wind erosion
#3 We should consider linking regional dust monitoring networks globally
For example: it would be possible to extend the DEDB methodology globally through the World Meteorological Organisation (WMO) network – but it would be challenging !
Aeronet (NASA) is an example of this happening
#4 We need to better integrate the products of regional and global dust monitoring networks – and link with the modellers
For example…….
Mackie et al., (2008) * show that the SEAREX **dust monitoring network in the Sth Pacific region occurred at a time of low dust activity in Australia
* Mackie, D.S. Boyd, P.W., McTainsh, G.H., Tindale, N.W., Westberry, T.K., and Hunter, K.A. (2008) “Biogeochemistry of Australian dust – from eolian uplift to marine uptake“.GEOCHEMISTRY, GEOPHYSICS, GEOSYSTEMS (G3) 9, (3).
The need to link with modellers was recently emphasised by: Okin G, Bullard J, Reynolds R, Ballantine J, Schepanski K, Todd M, Belnap J, Baddock M, Gill T, and Miller M.(2011) “Dust: Small-Scale Processes With Global Consequences”. EOS, Vol. 92, No. 29, 19 July 2011
** Prospero, J. M., M. Uematsu, and D. Savoie (1989), Mineral aerosol transport to the Pacific Ocean, in Chemical Oceanography, Ed J. P. Riley et al., pp. 187–218, Academic, New York.
#5 Finally … we need more International Research Workshops to launch focused international research projects to address data and
methodological issues *
For example……….
The paper by Bullard et al., (2011)* is an outcome of the QUEST Dust Workshop at Villefranche, France 2008, organised by Sandy Harrison and Barbara Maher.
* Bullard J, Harrison S, Baddock M, Drake N, Gill T, Mc Tainsh G and Sun Y. (2011) “Preferential dust sources: a geomorphological classification designed for use in global dust-cycle models”. JGR – in press.
* An outcome of this conference could be anInternational Research Workshop ??
DustWatch Australia is an outcome of the close collaboration of the following colleagues……..*
Acknowledgements………
Craig Strong
Harry ButlerYaping ShaoUniversity of Cologne,Germany
Tadhg O’Loingsigh
John Leys
Kenn TewsAlan LynchStephan Heidenreich
NSW Office of Env. & Heritage
NSW Office of Env. & Heritage
Griffith University
Griffith University
Griffith University
ex-Griffith University
University of Southern Queensland
….. AND funding from the Department of Agriculture, Fisheries and Forestry, Caring for Our Country Program - with thanks to Michele Barson.
Thankyou for your attention and here’s to a successful conference !
Road trains loading cattle at Helen Springs Station, Northern Territory -17 trucks and 1,504 tyres – imagine the dust when they start moving !
