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Wildland fires are a type of vegetation fire that burn in a rural or wild landscape and affect many countries worldwide. They are an important mechanism in ecosystem maintenance, although in certain cases wildland fires can adversely affect both people and the environment. A wildland fire can interact with the surrounding topography, vegetation and weather in a complex manner, which makes microscale prediction of wildland fire behaviour difficult in many situations. This thesis focused on the application of the Weather Research and Forecast (WRF) numerical weather prediction (NWP) and WRF-Fire coupled atmosphere-fire models to investigating aspects of atmospheric interactions with wildland fire. The research covered a wide range of atmospheric scales, from a seasonal mesoscale analysis of fire weather conditions across New Zealand to a microscale analysis of complex atmosphere-fire interactions over idealised terrain. The first study investigated the suitability of WRF modelling of fire weather conditions for the 2009/10 wildland fire season in New Zealand. The WRF model horizontal grid spacing was 8 km and the model output was directly compared with near-surface fire weather conditions meaured and derived at 23 weather stations located throughout New Zealand. The analysis considered the air temperature, relative humidity, wind conditions, rainfall and the New Zealand Fire Weather Index (FWI) and Continuous Haines Index (CHI) on observed high-end fire weather days. WRF typically underpredicted the air temperatures and relative humidities, whereas it typically overpredicted the wind speeds, CHI and the number of high-end fire weather days. WRF was assessed to be unsuitable for accurately modelling particular aspects of fire weather, such as the wind speed and direction, in mountainous terrain and near complex coastlines. Further research is needed to investigate how varying the horizontal resolution in WRF affects the assessed accuracy of modelled fire weather conditions. The second study investigated the behaviour of the Haines Index (HI), CHI and FWI, and their associated atmospheric properties for the 2009/10 wildland fire season in New Zealand. The analysis demonstrated that there was a large degree of spatial variability in fire weather conditions throughout New Zealand, particularly in or near mountainous terrain. The fire weather severity was highest in the eastern South Island and appeared to be closely associated with mesoscale atmospheric processes over mountainous terrain, although the relationship between these atmospheric processes and fire weather condi- tions requires further investigation. The HI and CHI were both limited in their utility at measuring aloft fire weather conditions in high altitude regions. Finally, the fire weather conditions associated with the 36 largest wildland fires of the fire season were evaluated, although no statistical relationships were found between the wildland fire size and either the CHI or FWI. The third study investigated the fire weather conditions across the South Island associated with an extreme foehn event on 6 February 2011. Mountain waves developed in the northwesterly synoptic flow over the Southern Alps and were found to directly influence the fire weather conditions near the surface and aloft in the lee of the mountains. A hydraulic jump along the foothills of the Canterbury Plains resulted in a downslope windstorm with wind speeds exceeding 80 km/h. Further south, large amplitude mountain lee waves directly influenced the near-surface wind speeds and atmospheric stability aloft. The foehn winds were associated with peak air temperatures over 35˚C in the eastern South Island, which are significantly higher than the climatological average. The FWI indicated widespread extreme near-surface fire weather conditions in the lee of the mountains. The subsequent passge of a cold front on 7 February brought a marked reduction in fire weather severity across the South Island. The fourth study investigated atypical wildland fire behaviour on steep leeward slopes through a series of idealised WRF-Fire simulations. The analysis considered both the leeward flow characteristics over a triangular ridge line and the fire spread from an ignition point at the base of the leeward slope. The fire spread was modelled for two different fuel types and with two-way atmosphere-fire coupling both enabled and disabled. The modelled fire spread in the heavy fuel type with coupling enabled closely resembled the fire channelling wildland fire behaviour phenomenon. The initial fire spread was initially dominated by upslope fire spread to the mountain ridge line at an average rate of around 2.0 km/h. This was followed by a phase of intermittent rapid lateral fire spread close to the ridge line at a maximum rate of around 3.6 km/h. The intermittent rapid lateral fire spread was driven by strongly circulating horizontal near-surface winds that were associated with updraft-downdraft interfaces. These updraft-downdraft interfaces formed due to an interaction between the strong pyro-convection and terrain-modified winds. The presented research collectively demonstrated the versatility and effectiveness of NWP and coupled atmosphere-fire modelling for studying various aspects of atmospheric interactions with wildland fire. The research further highlighted the effects of atmospheric processes over complex terrain on fire weather conditions and wildland fire behaviour. Although three of the studies in the thesis had a regional focus on New Zealand, the research outcomes should benefit end users in fire management worldwide.

In a field trial during 1995/96, epidemics of <I>Pyrenophora teres</I> and <I>Rhynchosporium secalis</I> were studied in winter barley with concurrent records of weather data to identify key environmental parameters that affect epidemics. Temperature was identified as a key influence in the onset of <I>P. teres</I> epidemics. Disease symptoms were observed to progress when daytime temperatures consistently reached 10°C and minimum nightime temperatures for the same period remained above 5°C. Short leaf wetness periods and longer photoperiods also correlated with increased disease levels during the <I>P. teres </I>epidemic. In <I>R. secalis,</I> relationships between disease onset and individual environmental parameters were not consistent, however, high rainfall events and prolonged leaf wetness periods were recorded prior to greatest disease increase. Hypotheses based on individual and combined weather criteria, based on the results of the 1995/96 field trials, were tested in controlled conditions. The effect of temperature on <I>P. teres</I> was confirmed, with small differences between ascospores and conidiospores. Latent period of both <I>P. teres</I> and <I>R. secalis</I> was influenced by cultivar resistance, inoculum concentration and plant growth stage. In a second field trial in 1996/97 reduced dose fungicide programmes, using hypotheses of epidemic development based on environmental criteria, were tested and compared favourably to a standard programme with greater fungicide doses. Environmental criteria were combined within a decision model for timed reduced-dose fungicide programmes for each pathogen, where risk scores were allotted for each set of criteria and fungicide treatment decision was based on the cumulative risk score. Both the <I>P. teres</I> and <I>R. secalis</I> decision models were tested in a final field trial in 1997/98. Lower disease levels and greater yield response, with lower fungicide input, was achieved from both models compared to a standard fungicide programme. The potential for using the <I>P. teres</I> and <I>R. secalis</I> decision models in a decision support system for cereals is discussed.

Changes in the physical properties of the atmosphere are caused by geographic influences and dynamic effects. The nature of the surface of the earth over which the air passes is usually the main factor in modifying the air in the lower levels of the troposphere. The ocean area of Hudson Bay in northeastern Canada presents an extensive surface for modification of air. Continental polar air crossing Hudson Bay and continuing into eastern Canada is modified not only by the underlying surface but also by the dynamic effects occurring in the atmosphere during its trajectory over these regions. The amount of modification is of major importance in the climate of the surrounding area, and in the meteorology of North American air masses. It was the purpose of this study: 1. To compute the changes in the physical properties that occur in continental polar air over Hudson Bay, Consequently, a project was undertaken to determine the amount of ice that forms on Hudson Bay in winter. The effect of the formation of ice in changing the modification of air was then studied. [...]

A study was conducted to quantify the relationships between growing season weather conditions and end-use quality of Canada Western Red Spring (CWRS) wheat (Triticum aestivum) grown in producer fields across western Canada (Alberta, Saskatchewan and Manitoba). Grain samples received an official grade at the Canadian Grain Commission and were milled into flour using a Buhler flour. Flour samples underwent an extensive analysis of flour, dough, and breadmaking quality. Daily precipitation amounts and maximum/minimum temperatures were accumulated for each field and then compared to quality data. In this study we also investigated the effectiveness of the Canadian grain grading system’s ability to segregate wheat samples into levels of increasing quality performance and uniformity. We found that for several flour and dough quality analysis, this was often achieved for either quality performance or uniformity, but there was not an improvement in both with an improvement in grade except in bread quality.

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No description available.

A study was conducted to quantify the relationships between growing season weather conditions and end-use quality of Canada Western Red Spring (CWRS) wheat (Triticum aestivum) grown in producer fields across western Canada (Alberta, Saskatchewan and Manitoba). Grain samples received an official grade at the Canadian Grain Commission and were milled into flour using a Buhler flour. Flour samples underwent an extensive analysis of flour, dough, and breadmaking quality. Daily precipitation amounts and maximum/minimum temperatures were accumulated for each field and then compared to quality data. In this study we also investigated the effectiveness of the Canadian grain grading system’s ability to segregate wheat samples into levels of increasing quality performance and uniformity. We found that for several flour and dough quality analysis, this was often achieved for either quality performance or uniformity, but there was not an improvement in both with an improvement in grade except in bread quality.