Alison Curl
BA/BSc (Honours) 2001
Research Focus
My primary research interests include micrometeorology and boundary layer climatology and more specifically agro climatology. I am interested in the nature and drivers of regional climates and how they determine the distribution of agricultural Australia. In addition how the distribution of agriculture may alter with a global changing climate. I am also interested in microclimate variations and how they contribute variations in yield and quality of horticultural produce.
Current Research
I am currently undertaking fieldwork which will provide the empirical evidence for my PhD thesis. I am looking at the factors driving vineyard yield and quality variability at sites in three of Victoria's premium wine regions, the Yarra Valley, Mornington Peninsula and the Strathbogie Ranges.
The commercial release of yield monitoring equipment for winegrape harvesters in 1999 lead to growth of the cutting edge practice of Precision Viticulture (PV). The yield monitoring equipment combined with tools such as differential global positioning systems (dGPS) and geographical information systems (GIS) provides vineyard managers with geo-referenced information about vineyard performance. This allows them to monitor spatial variation in productivity-related variables (yield and quality) within their vineyards. Early results from variability monitoring indicate significant variation in yield, up to 10-fold in single 7ha blocks. The reasons for this variability and ultimately the environmental driving factors of grape quality and yield are not yet understood.
To date, the factors which have been proposed for driving variation relate mainly to variations in soil factors such as texture and nutrient levels. However, in some of the premium wine regions in Victoria the terrain is highly variable generating several different microclimates within a single vineyard. It is proposed as part of my project that these variations in microclimate are contributing to vineyard productivity variability. Through the use of a grape yield monitor, a network of micro loggers, the results from a comprehensive soil survey and a GIS, I hope to explain some of the vineyard variability and understand the factors driving it.
Past Research
As part of my honours year in 200/2001I completed an extensive census and sampling program in semiarid north-west New South Wales which provided quantitative information on willy willy characteristics and their environmental range. Willy willies (dust devils) are local convective circulations, marked by dust, that characteristically arise in arid and semiarid environments. Intense heating of the surface results in high local instability which leads to thermal updrafts. The intensity of the associated horizontal and vertical winds results in the entrainment and transport of surface debris, and the visual definition of the column. As willy willies constitute a visual example of vortex motion they provided a unique means of studying small scale atmospheric vortices.
The results from observations of 557 willy willies in a 20 day census period, during mid summer, indicated that willy willy frequency, size, shape and duration vary according to local meteorological conditions. An air temperature lapse rate, measured between 12 and 252 cm of the surface, of 0.9 °C m -1 was required for the initiation of the willy willies, with the frequency increasing with lapse rate. Willy willies were also found to be restricted to wind speeds between 1.5 and 7.5 m s -1 . Analysis of the spatial distribution of willy willy initiation sites with respect to vegetation cover in the 35 km 2 study area also showed that willy willy frequency increases with decreasing surface cover.
The particles being transported in the lower 160 cm of 20 willy willies were also sampled using a tape-based vertical profile sampler developed for this sampling program. The analysis of the samples using a visual based digital analysis method revealed that almost 18% of the particles counted were being transported within the first 10 cm of the vortices and over 80% overall were 63 mm of smaller in major axis diameter. The results from this analysis, considered with respect to the characteristics of the surface the willy willy traversed during sampling, show that the sediment load carried in the willy willies increases with decreasing vegetation cover.
Some of the broader conclusions of the study were that the increased frequency of willy willies with decreasing vegetation and the preferential entrainment of silt sized particles could, over time, make willy willies a potent mechanism for the local differentiation of surface textures and that Willy willies may be contributing to the maintenance of the patchy plant cover that characterises much of inland Australia.
Contact details
E-mail: alison@environmentaljobs.com.au
Phone: (03) 9905 2953
Mobile: 0417 358 151