Original Research ARTICLE
Modelling wind direction distributions using a diagnostic model in the context of probabilistic fire spread prediction
- 1School of Mathematical Sciences, University of Adelaide, Australia
- 2ARC Centre of Excellence for Mathematical & Statistical Frontiers (ACEMS), Australia
- 3School of Physical, Environmental and Mathematical Sciences, University of New South Wales Canberra, Australia
- 4Bushfire and Natural Hazards CRC, Australia
- 5RMRS Missoula Fire Sciences Laboratory, United States Department of Agriculture, United States
- 6University of New South Wales Canberra, Australia
With emerging research into the dynamics of extreme fire behaviour, it is increasingly important for wind models used in operational fire prediction to accurately capture areas of complex flow across rugged terrain. Additionally, the emergence of ensemble and stochastic modelling frameworks has led to the discussion of uncertainty in fire prediction. To capture the uncertainty of modelled fire outputs, it is necessary to recast uncertain inputs in probabilistic terms.
WindNinja is the diagnostic wind model currently applied within a number of operational fire prediction frameworks across the world. For computational efficiency, allowing for real-time or faster than real-time prediction, the physical equations governing wind flow across complex terrain are often simplified. The model has a number of well documented limitations, for instance, it is known to perform least well on leeward slopes. This study first aims to understand these limitations in a probabilistic context by comparing individual deterministic predictions to observed distributions of wind direction. Secondly, a novel application of the deterministic WindNinja model is presented and shown to enable prediction of wind direction distributions that capture some of the variability of complex wind flow.
Recasting wind fields in terms of probability distributions enables better understanding of variability across the landscape, and provides the probabilistic information required to capture uncertainty through ensemble or stochastic fire modelling. The comparisons detailed in this study indicate the potential for WindNinja to predict multimodal wind direction distributions that represent complex wind behaviours, including recirculation regions on leeward slopes. However, the limitations of using deterministic models within probabilistic frameworks are also highlighted. To enhance fire prediction and better understand uncertainty, it is recommended that statistical approaches also be developed to complement existing physics-based deterministic wind models.
Keywords: WindNinja, Wind modelling, von Mises, uncertainty, Probability distributions, ensemble modelling, deterministic, complex terrain
Received: 23 Nov 2018;
Accepted: 04 Feb 2019.
Edited by:Guillermo Rein, Imperial College London, United Kingdom
Reviewed by:Xinyan Huang, Hong Kong Polytechnic University, Hong Kong
Wolfram Jahn, Pontificia Universidad Católica de Chile, Chile
Wei Tang, National Institute of Standards and Technology (NIST), United States
Copyright: © 2019 Quill, Sharples, Wagenbrenner, Sidhu and Forthofer. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Dr. Rachael Quill, University of Adelaide, School of Mathematical Sciences, Adelaide, Australia, email@example.com