Mika Peace - Academia.edu (original) (raw)

Papers by Mika Peace

International journal of wildland fire, Jun 19, 2024

Imprensa da Universidade de Coimbra eBooks, 2022

Pyrocumulonimbus (pyroCb) clouds are difficult to predict and can produce extreme and unexpected ... more Pyrocumulonimbus (pyroCb) clouds are difficult to predict and can produce extreme and unexpected wildfire behavior that can be hazardous to fire crews. Many forecasters modify conventional thunderstorm diagnostics to predict pyroCb potential, by adding temperature and moisture increments to represent smoke plume thermodynamics near the expected plume condensation level. An alternative approach is to anticipate the minimum firepower required to generate pyroCb for a given atmospheric environment.This concept, termed the pyroCb firepower threshold (PFT), requires only atmospheric information, removing the need for subjective estimates of the fire contribution. A simple approach to calculating PFT was presented by Tory and Kepert (2021) that incorporates only basic plume-rise physics, and yields an analytic solution for the minimum heat flux required to enter the base of the plume for pyroCb to form. This version takes into consideration the magnitude of any inversion or stable layer the smoke plume must penetrate, the height the smoke plume must rise before sufficiently buoyant cumulus clouds form in the smoke plume, and it incorporates the impact of wind on plume rise via the Briggs plume-rise model. This PFT also offers important insight into plume behavior and pyroCb formation. Many assumptions are made to close the equations and to maximise simplicity. Two of these assumptions are questioned in this paper following the investigation of two deep, moist pyro-convection cases that occurred during 'Black Summer' (southern Australia, September 2019-March 2020). The first assumption, consistent with many thunderstorm diagnostics, is that the moist (cloudy) plume is non-entraining, and the second assumption is that the plume is positively buoyant when it saturates and remains buoyant until it rises beyond the-20 ℃ level of the atmosphere. The first assumption underpredicts the fire-power required and the second assumption can overpredict the necessary firepower, since a vigorous plume may have sufficient kinetic energy to penetrate stable layers or capping inversions. Procedures are introduced to address these limitations.

Springer eBooks, 2022

Achieving consistency in the prediction of the atmosphere and related environmental hazards requi... more Achieving consistency in the prediction of the atmosphere and related environmental hazards requires careful design of forecasting systems. In this chapter, we identify the benefits of seamless approaches to hazard prediction and the challenges of achieving them in a multi-institution situation. We see that different modelling structures are adopted in different disciplines and that these often relate to the user requirements for those hazards. We then explore the abilities of weather prediction to meet the requirements of these different disciplines. We find that differences in requirement and language can be major challenges to seamless data processing and look at some ways in which these can be resolved. We conclude with examples of partnerships in flood forecasting in the UK and wildfire forecasting in Australia.

Atmosphere, Dec 21, 2020

† This discussion paper has been prepared for the BNHCRC 'Coupled fire-atmosphere modelling' proj... more † This discussion paper has been prepared for the BNHCRC 'Coupled fire-atmosphere modelling' project. It is intended for a primary audience of colleagues in the Bureau of Meteorology who have interest in fire related science and services, as well as stakeholders in land management and fire agencies.

Atmosphere

Coupled fire-atmosphere models are simulators that integrate a fire component and an atmospheric ... more Coupled fire-atmosphere models are simulators that integrate a fire component and an atmospheric component, with the objective of capturing interactions between the fire and atmosphere. As a fire releases energy in the combustion process, the surrounding atmosphere adjusts in response to the energy fluxes; coupled fire-atmosphere (CFA) models aim to resolve the processes through which these adjustments occur. Several CFA models have been developed internationally, mostly by meteorological institutions and primarily for use as a research tool. Research studies have provided valuable insights into some of the atmospheric processes surrounding a fire. The potential to run CFA models in real time is currently limited due to the intensive computational requirements. In addition, there is a need for systematic verification to establish their accuracy and the appropriate circumstances for their use. The Bureau of Meteorology (the Bureau) is responsible for providing relevant and accurate m...

Chan, F., Marinova, D. and Anderssen, R.S. (eds) MODSIM2011, 19th International Congress on Modelling and Simulation., 2011

In December 2007, Kangaroo Island was set ablaze by numerous dry lightning strikes. Our research ... more In December 2007, Kangaroo Island was set ablaze by numerous dry lightning strikes. Our research into the event has been conducted in two parts; a case study investigating the interactions between the local meteorology and observed fire behaviour, followed by simulations using the coupled atmosphericfire behaviour model WRF-fire. The findings from the case study highlight the importance of including information on atmospheric instability and spatial variation in meteorological parameters in fire weather forecasts. Our preliminary simulations using WRF-fire have explored the ability of the model to capture phenomena observed in the case study. The case study identified two occurrences of unusual fire behaviour which have been simulated: the first, when a fire located in a local sea breeze front convergence zone produced a spectacular convection column which developed by release of potential atmospheric instability triggered by local lifting; the second, when unprecedented fire behaviour was observed in relatively benign conditions, hypothesised to be due to convective plume entrainment of dry air aloft, enhanced by topographically driven processes and very dry, open structured fuels. The circumstances leading to the unusual fire behaviour(s) illustrate known limitations in the current Australian approach to fire weather forecasting, which neglects temporal and spatial variations, three dimensional atmospheric evolution and any interaction of the fire with the atmosphere. We used the coupled atmosphere-fire model WRF-fire to simulate the fires, with the initial aim of running WRF-fire on an Australian event and subsequently to assess the ability of WRF-fire to simulate the vertical dynamics and fire-atmosphere coupling observed in the case studies.

Predicting where and how a fire will burn is critical information for mitigating the impacts of b... more Predicting where and how a fire will burn is critical information for mitigating the impacts of bushfires and minimising risk at fuel reduction burns. Firefighter entrapments and fatalities occur mostly at fires that display rapid changes or fluctuations in fire activity. In this thesis, I explore several of the factors that lead to rapid changes in fire behaviour. Understanding these factors is necessary in order to produce accurate fire predictions, which are critical for fire-fighter safety and effective operations. Weather is a primary driver of fire activity; consequently, meteorological information is a key input for anticipating fire behaviour. At present, weather forecasts focus on near-surface conditions; but fires and the atmosphere are three dimensional, and dynamical interactions occur that can have a dramatic influence on fire behaviour. However, these fire-atmosphere interactions are poorly understood due to their complex nature and the difficulty of collecting observa...

Fire

The destructive Sir Ivan Dougherty fire burned 55,000 hectares around 250 km northwest of Sydney ... more The destructive Sir Ivan Dougherty fire burned 55,000 hectares around 250 km northwest of Sydney in New South Wales on 12 February 2017. Record hot temperatures were recorded in the area during the lead-in days and the fire conditions at the time were described as the ‘worst ever seen in NSW’. The observed weather conditions were hot, dry and very windy ahead of a synoptic frontal wind change during the afternoon. ‘Extreme’ to ‘catastrophic’ fire weather was predicted, and the potential for extreme fire behaviour was identified several days in advance. The Australian coupled fire–atmosphere model ACCESS-Fire has been run to explore the characteristics of the Sir Ivan fire. Several features resulting from fire–atmosphere interaction are produced in the simulations. Simulated heat flux along the fire perimeter shows increased intensity on the northern fire flank in response to gradual backing winds ahead of the main frontal wind change. Temporal and spatial variability in fire activit...

Journal of Southern Hemisphere Earth Systems Science

The Waroona fire burned 69 000 ha south of Perth in January 2016. There were two fatalities and 1... more The Waroona fire burned 69 000 ha south of Perth in January 2016. There were two fatalities and 170 homes were lost. Two evening ember storms were reported and pyrocumulonimbus (pyroCb) cloud developed on consecutive days. The extreme fire behaviour did not reconcile with the near- surface conditions customarily used to assess fire danger. A case study of the fire (Peace et al. 2017) presented the hypothesis that the evening ember storms resulted from interactions between the above-surface wind fields, local topography and the fire plume. The coupled fire–atmosphere model ACCESS-Fire has been run in order to explore this hypothesis and other aspects of the fire activity, including the pyroCb development. ACCESS-Fire incorporates the numerical weather prediction model ACCESS (Australian Community Climate and Earth System Simulator, described by Puri et al. 2013) and a fire spread component. In these simulations, the Dry Eucalypt Forest Fire (Vesta) fire spread model is used. In this ...

CSIRO and the Bureau of Meteorology advise that the information contained in this publication com... more CSIRO and the Bureau of Meteorology advise that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO and the Bureau of Meteorology (including each of its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it.

1 Simulations of the Waroona Fire with the ACCESS-Fire coupled fire atmosphere model 1 EXTENDED A... more 1 Simulations of the Waroona Fire with the ACCESS-Fire coupled fire atmosphere model 1 EXTENDED ABSTRACT 2 Introduction 2 Coupled fire-atmosphere modelling 2 ACCESS-Fire 3

Australian Meteorological and Oceanographic Journal, 2015

The Layman fire commenced as a routine fuel reduction burn in southwest Western Australia in Octo... more The Layman fire commenced as a routine fuel reduction burn in southwest Western Australia in October 2010. Late morning on the day following ignition, the fire was more active than fire management officers had expected under the prevailing conditions of wind, temperature and relative humidity in the local eucalypt forest fuels. A convective smoke plume developed over the fire, extending to a height of approximately 4000 m. Traditional measures for assessing fire behaviour gave no indication of the extent of the crown fire that occurred. This paper describes simulations of the fire using the coupled fire-atmosphere model WRF and SFIRE. The simulations show that fire-atmosphere feedback produces a northeast to northwest wind shift and surface convergence occur over the fire just after the fire's buoyant plume grows through the overnight nocturnal layer into the residual mixed layer of the planetary boundary layer (PBL) from the previous day. The simulation results show that the timing of the wind shift and vertical growth of the fire plume closely matched the observed development of the convective smoke plume above the fire.

Australian Meteorological and Oceanographic Journal, 2013

Journal of Applied Meteorology and Climatology, 2016

The coupled atmosphere–fire spread model “WRF-SFIRE” has been used to simulate a fire where extre... more The coupled atmosphere–fire spread model “WRF-SFIRE” has been used to simulate a fire where extreme fire behavior was observed. Tall flames and a dense convective smoke column were features of the fire as it burned rapidly up the Rocky River gully on Kangaroo Island, South Australia. WRF-SFIRE simulations of the event show a number of interesting dynamical processes resulting from fire–atmosphere feedback, including the following: fire spread was sensitive to small changes in mean wind direction; fire perimeter was affected by wind convergence resulting from interactions between the fire, atmosphere, and local topography; and the fire plume mixed high-momentum air from above a strong subsidence inversion. At 1-min intervals, output from the simulations showed fire spread exhibiting fast and slow pulses. These pulses occurred coincident with the passage of mesoscale convective (Rayleigh–Bénard) cells in the planetary boundary layer. Simulations show that feedback between the fire and...

From time to time, bushfires exhibit fire behaviour that was never anticipated in the prevailing ... more From time to time, bushfires exhibit fire behaviour that was never anticipated in the prevailing environmental conditions. The Layman burn, in scenic southwest Western Australia, and D'Estrees Bay fire, on pristine Kangaroo Island, were two such fires. Both developed intense crown fires, high flames and convection columns with a deep vertical circulation that extended through the lower part of the atmosphere. In both cases, the intense fire activity was driven by a combination of me-teorological processes not routinely assessed in fire environments. Low level sea breeze convergence and vertical circulation on the sea breeze front, combined with potentially unstable vertical temperature and moisture profiles conducive to convective parcel motion as measured by FireCAPE, as well as entrainment of dry air from aloft desiccating already climatologically dry fuels, were all present. It is believed that these co-located elements produced the intense conflagrations. Improved understand...

Journal of Applied Meteorology and Climatology, 2015

The coupled fire–atmosphere model consisting of the Weather and Forecasting (WRF) Model coupled w... more The coupled fire–atmosphere model consisting of the Weather and Forecasting (WRF) Model coupled with the fire-spread model (SFIRE) module has been used to simulate a bushfire at D’Estrees Bay on Kangaroo Island, South Australia, in December 2007. Initial conditions for the simulations were provided by two global analyses: the GFS operational analysis and ERA-Interim. For each NWP initialization, the simulations were run with and without feedback from the fire to the atmospheric model. The focus of this study was examining how the energy fluxes from the simulated fire modified the local meteorological environment. With feedback enabled, the propagation speed of the sea-breeze frontal line was faster and vertical motion in the frontal zone was enhanced. For one of the initial conditions with feedback on, a vortex developed adjacent to the head fire and remained present for over 5 h of simulation time. The vortex was not present without fire–atmosphere feedback. The results show that t...

Advances in forest fire research, 2014

A navegação consulta e descarregamento dos títulos inseridos nas Bibliotecas Digitais UC Digitali... more A navegação consulta e descarregamento dos títulos inseridos nas Bibliotecas Digitais UC Digitalis, UC Pombalina e UC Impactum, pressupõem a aceitação plena e sem reservas dos Termos e Condições de Uso destas Bibliotecas Digitais, disponíveis em https://digitalis.uc.pt/pt-pt/termos. Conforme exposto nos referidos Termos e Condições de Uso, o descarregamento de títulos de acesso restrito requer uma licença válida de autorização devendo o utilizador aceder ao(s) documento(s) a partir de um endereço de IP da instituição detentora da supramencionada licença. Ao utilizador é apenas permitido o descarregamento para uso pessoal, pelo que o emprego do(s) título(s) descarregado(s) para outro fim, designadamente comercial, carece de autorização do respetivo autor ou editor da obra. Na medida em que todas as obras da UC Digitalis se encontram protegidas pelo Código do Direito de Autor e Direitos Conexos e demais legislação aplicável, toda a cópia, parcial ou total, deste documento, nos casos em que é legalmente admitida, deverá conter ou fazer-se acompanhar por este aviso. Reconstructing the spread of landscape-scale fires in semi-arid southwestern Australia

Journal of Southern Hemisphere Earth System Science, 2017

During the first two days of the fire, there were two pyrocumulonimbus (pyroCb) events and two de... more During the first two days of the fire, there were two pyrocumulonimbus (pyroCb) events and two destructive evening fire runs. Over 160 homes were destroyed and there were two fatalities. This case study examines in detail the links between the meteorological observations and the fire behaviour reconstruction.