Sources and pathways of dust during the Australian 'Millennium Drought' decade

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

Doctor of Philosophy

dissertationThis study provides a holistic view of dust storms and transport in the eastern Great Basin, and is the first to analyze the meteorological, source, and chemical characteristics of dust production in this region. First, the climatology of dust storm events affecting Salt Lake City, Utah (SLC) was assessed, and the controls on atmospheric dust generation and transport documented. Records indicate seasonal and diurnal patterns, with dust storms typically occurring in spring months during the afternoon. Since 1930, SLC had 379 dust event days (DEDs), averaging 4.7 per year, with elevated PM10 exceeding National Ambient Air Quality Standards (NAAQS) on 16 days since 1993, or 0.9 per year. Strengthening cyclonic systems are the primary producer of these dust storms. Next anthropogenically disturbed areas and barren playa surfaces were identified as the primary dust source types contributing to dust storms in the region. Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery during DEDs was analyzed to identify dust plumes, and assess the characteristics of dust source areas, which produce dust during the spring and fall and during drought. Most plumes originate from playas, classified as Barren land cover, with a silty clay soils; they often have anthropogenic disturbances, including military operations and water withdrawal. Disturbance is necessary to produce dust from vegetated landscapes in the region, evidenced by the new dust source active from 2008-2010 in the 2007 Milford Flat Fire scar, which underwent postfire land treatments. Finally, the elemental composition of dust in the region was characterized. Dust and surface soil samples were collected, resuspended, and analyzed with Sychrotron XRay Fluorescence (SXRF). Dust and soil from the eastern Great Basin are distinctly different, and identifiable. Within the dust and soil groups, however, large differences are not seen and individual samples cannot be identified by their elemental composition. Dust and soil from the eastern Great Basin tends to not be enriched in most major soil elements, excepting a large enrichment of Na in dust samples. Trace elements, however, show very large enrichment values for both dust and soil. The enrichment of dust samples has notable importance for ecosystem functioning and human health

Global assessment of sand and dust storms

The specific objectives of the assessment are to: 1) Synthesise and highlight the environmental and socio-economic causes and impacts of SDS, as well as available technical measures for their mitigation, at the local, regional and global levels; 2) Show how the mitigation of SDS can yield multiple sustainable development benefits; 3) Synthesize information on current policy responses for mitigating SDS and 4) Present options for an improved strategy for mitigating SDS at the local, regional and global levels, building on existing institutions and agreements

Determining ground-level composition and concentration of particulate matter across regional areas using the Himawari-8 satellite

Speciated ground-level aerosol concentrations are required to understand and mitigate health impacts from dust storms, wildfires and other aerosol emissions. Globally, surface monitoring is limited due to cost and infrastructure demands. While remote sensing can help estimate respirable (i.e. ground level) concentrations, current observations are restricted by inadequate spatiotemporal resolution, uncertainty in aerosol type, particle size, and vertical profile. One key issue with current remote sensing datasets is that they are derived from reflectances observed by polar orbiting imagers, which means that aerosol is only derived during the daytime, and only once or twice per day. Sub-hourly, infrared (IR), geostationary data, such as the ten-minute data from Himawari-8, are required to monitor these events to ensure that sporadic dust events can be continually observed and quantified. Newer quantification methods using geostationary data have focussed on detecting the presence, or absence, of a dust event. However, limited attention has been paid to the determination of composition, and particle size, using IR wavelengths exclusively. More appropriate IR methods are required to quantify and classify aerosol composition in order to improve the understanding of source impacts. The primary research objectives were investigated through a series of scientific papers centred on aspects deemed critical to successfully determining ground-level concentrations. A literature review of surface particulate monitoring of dust events using geostationary satellite remote sensing was undertaken to understand the theory and limitations in the current methodology. The review identified (amongst other findings) the reliance on visible wavelengths and the lack of temporal resolution in polar-orbiting satellite data. As a result of this, a duststorm was investigated to determine how rapidly the storm passed and what temporal data resolution is required to monitor these and other similar events. Various IR dust indices were investigated to determine which are optimum for determining spectral change. These indices were then used to qualify and quantitate dust events, and the methodology was validated against three severe air quality events of a dust storm; smoke from prescribed burns; and an ozone smog incident. The study identified that continuous geostationary temporal resolution is critical in the determination of concentration. The Himawari-8 spatial resolution of 2 km is slightly coarse and further spatial aggregation or cloud masking would be detrimental to determining concentrations. Five dual-band BTD combinations, using all IR wavelengths, maximises the identification of compositional differences, atmospheric stability, and cloud cover and this improves the estimated accuracy. Preliminary validation suggests that atmospheric stability, cloud height, relative humidity, PM2.5, PM10, NO, NO2, and O3 appear to produce plausible plumes but that aerosol speciation (soil, sea-spray, fires, vehicles, and secondary sulfates) and SO2 require further investigation. The research described in the thesis details the processes adopted for the development and implementation of an integrated approach to using geostationary remote sensing data to quantify population exposure (who), qualify the concentration and composition (what), assess the temporal (when) and spatial (where) concentration distributions, to determine the source (why) of aerosols contribution to resulting ground-level concentration

Sources and pathways of dust during the Australian "Millennium Drought" decade

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 environmentsThe authors gratefully acknowledge the Australian Research Council (DP0772180) for funding this research

Sources, drivers and sedimentology of Icelandic dust events

There is increasing evidence for high magnitude dust storms in high latitude environments. Yet, Aeolian processes in these areas have been largely understudied and therefore our knowledge of these systems is limited. Understanding dust emission processes from the high latitudes regions is of increasing importance because future climate scenarios indicate a reduction in terrestrial ice masses and an expansion in glacial outwash plains which are the main dust sources in high latitude environments. Of these regions, Iceland is the most researched high latitude dust source region, however our understanding of processes which lead to dust events are still poorly understood. This thesis examines the interlinking relationship between dust source and dust particle sedimentology and the physical and meteorological drivers which promote or inhibit dust emission in Iceland. This is achieved through active aeolian monitoring at source during two monitoring periods at Markarfljot, South Iceland. These measurements are complimented using secondary data sources (e.g. meteorological and satellite data), sedimentological mapping and particle analysis and laboratory abrasion experiments. This thesis is the first high resolution multi event record of dust emissions in the high latitudes and concludes by showing that potential dust concentrations and dust particle size are driven by the interlinking relationship between wind speed, sediment texture and surface moisture. Factors that affect the potential sediment availability for dust events are more important in the high latitudes than in the subtropics in driving spatial and temporal variability in dust emission. Measurements presented in this thesis are required to verify and tune regional and global modelling attempts to quantify the potential contribution of high latitude dust in the Earth system. However, further measurements are required to fully understand seasonal changes in dust emissions, across a variety of dust source units within all high latitude dust source regions

Climate, vegetation cover and dust storm events in arid and semi-arid regions of Australia - relationships, models and predictions

Wind erosion is a land degradation process in arid, semi-arid and agricultural regions of Australia. The loss of soil as a result of this process affects human health, environment and the economy. Climate variables such as rainfall and temperature play a major role in wind erosion activity. In particular, the quantity and distribution of rainfall influences the growth of vegetation cover which protects the soil surface from erosion (both wind and water erosion). Hence, climate variability is of great concern due to the pressure on agricultural land to produce more food for a growing population and the subsequent pressure to grow crops on drier more marginal lands that are more susceptible to wind erosion. This research investigates the historic relationship between climatic conditions and recorded dust storm events based on more than 16 decades of collated dust storm event data from a wide number of sources (e.g. personal experiences, diaries, book excerpts, newspaper clippings, journal articles, reports and others). The 587 dust storm event records have been collated into a Historical Dust Event Database (HDED). The HDED indicated an increased number of dust storm events occurred in the 1900s, 1940s, 1960s and 2000s. This is due to the close link of rainfall and temperature to the ENSO cycle which directly impacts on the vegetation cover, a key factor driving the frequency, intensity and spatial distribution of dust events. Broad scale estimation of spatial changes in vegetation cover would be useful in a wide range of applications and is of particular interest and value in areas of environmental, ecological and land-use modelling. Currently, broadly applicable modelling methods or indices are not available to realistically estimate vegetation cover levels for periods before the early 1990s when satellite remote sensing first became readily available. This includes any historical or future forecasting periods. As wind erosion/dust events are strongly dependent on vegetation cover, to analyse past or future dust events a means of estimating broad scale cover across Australia is required. The newly developed Climate Aridity Vegetation Index (CAVI) is a simple broad scale vegetation index across Australia, based on rainfall and temperature data. The CAVI is calculated using 12 months weighted rainfall and temperature data to produce vegetation cover maps without modelling individual vegetation type responses, seasonality and land-use. The CAVI produced particularly good estimation of vegetation cover during the Spring - Summer season but can over emphasise the relationship between rainfall, temperature and vegetation/green cover when increased rainfall occurs close to the month of interest. Nevertheless, the index produces good representative estimates and spatial maps of vegetation cover levels during the spring – summer seasons in Australia. Wind erosion modelling occurs at a variety of spatial and temporal scales to determine the extent and severity of wind erosion across Australia. With the development of CAVI, historical and future wind erosion rates can be modelled, dust source areas can be estimated and identified, and the severity of these early dust storm events can be compared to modern events before land management changes were adopted. This has previously never been possible since reliable satellite derived photosynthetically active fractional vegetation cover (fPV) data is not available prior to February 2000. To test the validity of such models, CAVI estimates of vegetation cover have been tested as a surrogate for remote sensed fPV in the Computational Environmental Management System (CEMSYS) for two large scale dust storm events in September 2009 and October 2002. The CEMSYS estimated daily dust loads based on CAVI and fPV were compared in regards to the spatial patterns of the eroded areas and the dust load intensity of the modelled wind erosion days. The use of CAVI as a surrogate for fPV in September 2009 and October 2002 CEMSYS modelling results were encouraging. Similar spatial erosion characteristics were observed in the simulations but the dust concentration based the CAVI was on occasions lower than based on fPV data. The CAVI was also applied to model the historical dust storm periods in November 1965. The modelling results from the study indicates that there is potential for CAVI to be used as a surrogate for fPV and gives us for the first time some estimates of the extent and severity of historical dust storm events

Automated dust storm detection using satellite images. Development of a computer system for the detection of dust storms from MODIS satellite images and the creation of a new dust storm database.

Dust storms are one of the natural hazards, which have increased in frequency in the recent years over Sahara desert, Australia, the Arabian Desert, Turkmenistan and northern China, which have worsened during the last decade. Dust storms increase air pollution, impact on urban areas and farms as well as affecting ground and air traffic. They cause damage to human health, reduce the temperature, cause damage to communication facilities, reduce visibility which delays both road and air traffic and impact on both urban and rural areas. Thus, it is important to know the causation, movement and radiation effects of dust storms. The monitoring and forecasting of dust storms is increasing in order to help governments reduce the negative impact of these storms. Satellite remote sensing is the most common method but its use over sandy ground is still limited as the two share similar characteristics. However, satellite remote sensing using true-colour images or estimates of aerosol optical thickness (AOT) and algorithms such as the deep blue algorithm have limitations for identifying dust storms. Many researchers have studied the detection of dust storms during daytime in a number of different regions of the world including China, Australia, America, and North Africa using a variety of satellite data but fewer studies have focused on detecting dust storms at night. The key elements of this present study are to use data from the Moderate Resolution Imaging Spectroradiometers on the Terra and Aqua satellites to develop more effective automated method for detecting dust storms during both day and night and generate a MODIS dust storm database.Libyan Centre for Remote Sensing and Space ScienceAppendix A was submitted with extra data files which are not available online

Production of semi-real time media-GIS contents of natural disasters using MODIS satellite data

In the event of a natural disaster, the information provided to the public can play an important role in its mitigation and management. Use of media-GIS content has been shown to provide information that is visual and accessible to the public. This report focuses on the information provided to the public through the media and develops rigorous production methods and quality practices to encourage increased strategic use of media-GIS content. The report utilizes three natural disaster case studies to evaluate the production method and presents recommendations and conclusions based on the information these provide. Previous studies identified five aspects that are important to media-GIS contents. These are accuracy, high aesthetic quality, speed, low cost and reusability. A review of MODIS imagery has shown it to sufficiently satisfy all five aspects. The report identifies an ideal source of MODIS data and a production method based on the information available to be obtained. By applying this methodology to the three case studies, it was found that the process could be more streamlined than previously identified methods. Further observations identified both positive and negative aspects of the method allowing improvements to be made were possible. Whilst limitations of MODIS were identified, the properties of MODIS data make it evident that it is the most effective source of satellite data for the production of media-GIS content where time and cost need to be minimised. Completion of the case studies led to the production of a guidebook, presented in Appendix F, which is intended to be issued to media outlets as an instruction manual for producing media-GIS contents. It is hoped that this will encourage an increase in the use of GIS within the media industry and provide thorough production method and quality practices information