SPATIAL VARIABILITY IN FOREST FUELS: SIMULATION MODELING AND EFFECTS ON FIRE BEHAVIOR

Forests in the western United States and elsewhere face a growing crisis arising from global warming, changes in fuel beds and an increasing human population. Fire management policy emphasizes fuel treatments, such as thinning and prescribed burning, to remedy this situation because fuels are the one component of the problem that we can directly affect through management action. At present, however, the tools we have for the evaluation of fuel treatments are inadequate because they do not describe the fuel bed, or effects of modifications to the fuel bed on fire behavior in sufficient detail. The work described here presents a system that has potential to address the shortcomings of current approaches. In the first chapter, to improve our ability to represent wildland fuels, a three dimensional spatially explicit fuel model, FUEL3D, is presented which represents fuels at a level of detail comparable to what we can actually measure: stands as collections of individual trees, with branches and foliage. In conjunction with new, physical fire models, detailed fire behavior simulations can be carried out using fuels represented with FUEL3D as inputs. This system thus comprises a simulation laboratory which will greatly enhance our capabilities to evaluate fuel treatments and strengthen our understanding of fire and fuel interactions. In the second chapter, this system is demonstrated in an exploratory simulation study which examines the impact of spatial variability within an individual tree crown on fire behavior. Results demonstrate that the distribution of fuel within a tree crown significantly affects the rate of fuel consumption, as well as the timing, duration and magnitude of heat produced. This suggests that modeling of both crown fire initiation and propagation would benefit from more detailed description of crown fuels. In third chapter a replicated series of stand scale fire simulations is carried out to examine variability in forward spread rate; accelerated spread rates endanger fire fighters. Substantial variability is observed to arise from fine scale fuel-atmosphere-fire interactions which are not easily predicted beforehand. A new strategy is proposed in which physical fire models are used to quantify the potential drivers of variability in fire behavior

Computing wildfire behaviour metrics from CFD simulation data

In this article, we demonstrate a new post-processing methodology which can be used to analyse CFD wildfire simulation outputs in a model-independent manner. CFD models produce a great deal of quantitative output but require additional post-processing to calculate commonly used wildfire behaviour metrics. Such post-processing has so far been model specific. Our method takes advantage of the 3D renderings that are a common output from such models and provides a means of calculating important fire metrics such as rate of spread and flame height using image processing techniques. This approach can be applied similarly to different models and to real world fire behaviour datasets, thus providing a new framework for model validation. Furthermore, obtained information is not limited to average values over the complete domain but spatially and temporally explicit metric distributions are provided. This feature supports posterior statistical analyses, ultimately contributing to more detailed and rigorous fire behaviour studies.Peer ReviewedPostprint (published version

Quantifying effects of using thermally thin fuel approximations on modelling fire propagation in woody fuels

In this paper, we quantify the effects of the thermally thin fuel approximations commonly made in numerical models that eliminate temperature gradients within a heated object. This assumption is known to affect the modeled ignition and burn behavior, but there is little research on its impact, particularly in larger fuels or in numerical models including moisture and chemical decomposition of fuels. We begin by comparing modeled to observed ignition times and burn rates. To constrain variability in the material properties of wood and focus on variability caused by fuels assumed to be thermally thin, we conduct experiments using thermogravimetric analysis (TGA) for samples of lodgepole pine. From these data, we derive material properties via optimization with genetic algorithms. We consider burnout experiments on large, woody fuels to confirm ignition time and mass loss rates for a range of fuel specimens and then recreate them with a numerical modeling platform to validate the model. Once validated, we use the model to explore the significance of thermally thin fuel assumptions by performing the same analyses on fuels assumed to be thermally thick and thermally thin. We quantify the ignition times and mass loss rates but also examine differences in thermal inertia of ignited fuels and how the compositions of fuels vary spatially and temporally. We find that fuels of around 1mm in thickness of both approximations show very similar ignition times, mass loss rates, and surface temperature histories. Fuels any larger will quickly show differences

A Methodology for Appropriate Testing When Data is Heterogeneous Using EXCEL

A Methodology for Appropriate Testing When Data is Heterogeneous was originally published and copy written in the mid-1990s in Turbo Pascal and a 16-bit operating system.  While working on an ergonomic dissertation (Yearout, 1987), the author determined that the perceptual lighting preference data was heterogeneous and not normal.  Drs. Milliken and Johnson, the authors of Analysis of Messy Data Volume I: Designed Experiments (1989), advised that Satterthwaite’s Approximation with Bonferroni’s Adjustment to correct for pairwise error be used to analyze the heterogeneous data. This technique of applying linear combinations with adjusted degrees of freedom allowed the use of t-Table criteria to make group comparisons without using standard nonparametric techniques.  Thus data with unequal variances and unequal sample sizes could be analyzed without losing valuable information.  Variances to the 4th power were so large that they could not be reentered into basic calculators.  The solution was to develop an original software package which was written in Turbo Pascal on a 7 ¼ inch disk 16-bit operating system.  Current operating systems of 32 and 64 bits and more efficient programming languages have made the software obsolete and unusable. Using the old system could result either in many returns being incorrect or the system terminating.  The purpose of this research was to develop a spreadsheet algorithm with multiple interactive EXCEL worksheets that will efficiently apply Satterthwaite’s Approximation with Bonferroni’s Adjustment to solve the messy data problem.  To ensure that the pedagogy is accurate, the resulting package was successfully tested in the classroom with academically diverse students.  A comparison between this technique and EXCEL’s Add-Ins Analysis ToolPak for a t-test Two-Sample Assuming Unequal Variances was conducted using several different data sets.  The results of this comparison were that the EXCEL Add-Ins returned incorrect significant differences.  Engineers, ergonomists, psychologists, and social scientists will find the developed program very useful. A major benefit is that spreadsheets will continue to be current regardless of evolving operating systems’ status

Reification and Truthmaking Patterns

Reification is a standard technique in conceptual modeling, which consists of including in the domain of discourse entities that may otherwise be hidden or implicit. However, deciding what should be rei- fied is not always easy. Recent work on formal ontology offers us a simple answer: put in the domain of discourse those entities that are responsible for the (alleged) truth of our propositions. These are called truthmakers. Re-visiting previous work, we propose in this paper a systematic analysis of truthmaking patterns for properties and relations based on the ontolog- ical nature of their truthmakers. Truthmaking patterns will be presented as generalization of reification patterns, accounting for the fact that, in some cases, we do not reify a property or a relationship directly, but we rather reify its truthmakers

Western Spruce Budworm and Wildfire: Is There a Connection?

In the interior Pacific Northwest, extensive defoliation of mixed conifer forests during outbreaks of western spruce budworm (WSB) may leave the visual impression of a tinderbox with trees primed to burst into flame. But is this the case? We addressed this question with funding from the USDA/U.S. Department of the Interior Joint Fire Science Program (project 09– 1–06–5). Here we summarize our three recent publications exploring the potential relationship between WSB outbreaks and fire. We used a multimethod approach to explore potential disturbance interactions that might cause one disturbance to change the occurrence or severity of the other. We used tree-ring records to see whether WSB and fire are related in time and computer modeling to see how defoliation could affect crown fire behavior

Towards an Ontological Modelling of Preference Relations

Preference relations are intensively studied in Economics, but they are also approached in AI, Knowledge Representation, and Conceptual Modelling, as they provide a key concept in a variety of domains of application. In this paper, we propose an ontological foundation of preference relations to formalise their essential aspects across domains. Firstly, we shall discuss what is the ontological status of the relata of a preference relation. Secondly, we investigate the place of preference relations within a rich taxonomy of relations (e.g. we ask whether they are internal or external, essential or contingent, descriptive or nondescriptive relations). Finally, we provide an ontological modelling of preference relation as a module of a foundational (or upper) ontology (viz. OntoUML). The aim of this paper is to provide a sharable foundational theory of preference relation that foster interoperability across the heterogeneous domains of application of preference relations

Duffer’s Shoal: A Strategic Dream of the Pacific Command Area of Responsibility

This strategic assessment seeks to go beyond a traditional comparative analysis of the military, technological, political, cultural, and economic factors governing the relationships and capabilities of the Asia Pacific environment. To make sense of the intrinsic complexities unique to this region, we endeavor to broaden our view and rely on a tool often overlooked in government studies: imagination. Moreover, we aim to offer a strategic document that is readable, instructive, and provocative. Pulling from a well-referenced piece of military teaching, this assessment borrows a learning concept first employed in 1904 by Major General Sir Ernest Dunlop Swinton in The Defence of Duffer’s Drift. This fictional story describes the plight of young Lieutenant Backsight Forethought as he commands a 50-man platoon tasked to hold a tactically critical piece of land called Duffer’s Drift. The story unfolds in a series of six dreams, where the blunders of the unwitting lieutenant lead to disaster. As the dreams progress, he harnesses the lessons of each of his failures, and by applying these lessons, his platoon ultimately defends Duffer’s Drift.https://press.armywarcollege.edu/monographs/1445/thumbnail.jp

Marine Noise Pollution - Increasing Recognition But Need for More Practical Action

Over the last two decades, marine noise pollution has become increasingly recognized as an issue of major significance. The issue has become a primary focus of marine mammal research, but is also of concern to the public and policy makers. The result has been efforts involving a variety of disciplines, and relevant legislation and associated guidance are now in place in many parts of the world. Most current mitigation efforts are directed at reducing the risk of injury from exposure to intense noise, although the effectiveness of such mitigation measures in terms of risk reduction has rarely been quantified. Longer-term chronic impacts of noise including disturbance or masking of sounds critical for feeding and reproduction have received substantially less attention in management. New technologies are being developed for a number of activities which can substantially reduce noise inputs into the marine environment. As with other forms of pollution, reducing input at source is likely to be the most effective way of reducing impacts. We recommend as a priority the implementation of noise quieting technologies and the spatial and temporal exclusion of noise to minimize contact with marine life