@article {bnh-7785, title = {Lessons learned from coupled fire-atmosphere research and implications for operational fire prediction and meteorological products provided by the Bureau of Meteorology to Australian fire agencies}, journal = {Atmosphere}, volume = {11}, year = {2020}, month = {12/2020}, chapter = {1380}, abstract = {

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 meteorological information to Australian fire agencies to inform decisions for the protection of life and property and to support hazard management activities. The inclusion of temporally and spatially detailed meteorological fields that adjust in response to the energy released by a fire is seen as a component in developing fire prediction systems that capture some of the most impactful fire and weather behavior. The Bureau{\textquoteright}s ten-year research and development plan includes a commitment to developing CFA models, with the objective of providing enhanced services to Australian fire agencies. This paper discusses the operational use of fire predictions and simulators, learnings from CFA models and potential future directions for the Bureau in using CFA models to support fire prediction activities.

}, keywords = {coupled fire-atmosphere, Fire, meteorology, modeling}, doi = {https://doi.org/10.3390/atmos11121380}, url = {https://www.mdpi.com/2073-4433/11/12/1380}, author = {Mika Peace and Joseph Charney and John Bally} } @article {bnh-7773, title = {Pyrocumulonimbus Firepower Threshold: Assessing the atmospheric potential for pyroCb}, journal = {Weather and Forecasting}, year = {2020}, month = {12/2020}, abstract = {

Pyrocumulonimbus (pyroCb) clouds are difficult to predict and can produce extreme and unexpected wildfire behaviour that can be very hazardous to fire crews. Many forecasters modify conventional thunderstorm diagnostics to predict pyroCb potential, by adding temperature (Δθ) and moisture increments (Δq) to represent smoke plume thermodynamics near the expected plume condensation level. However, estimating these Δθ\ and Δq\ increments is a highly subjective process that requires expert knowledge of all factors that might influence future fire size and intensity. In this paper, instead of trying to anticipate these Δθ\ and Δq\ increments for a particular fire, the minimum firepower required to generate pyroCb for a given atmospheric environment is considered. 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 is presented that incorporates only basic plume-rise physics, yielding an analytic solution that offers important insight into plume behaviour and pyroCb formation. Minimum increments of Δθ\ and Δq\ required for deep, moist convection, plus a minimum cloud-base height (Zfc), are diagnosed on a thermodynamic diagram. Briggs plume rise equations are used to convert Δθ,\ Zfc, and a mean horizontal windspeed (U) to a measure of the PFT: the minimum heat flux entering the base of the plume. This PFT is proportional to the product of\ U, Δθ, and the square of\ Zfc. Plume behaviour insights provided by the Briggs equations are discussed, and a selection of PFT examples presented.

}, keywords = {atmosphere, fire power, Fire weather, meteorology, pyrocumulonimbus}, doi = {https://doi.org/10.1175/WAF-D-20-0027.1}, url = {https://journals.ametsoc.org/view/journals/wefo/aop/WAF-D-20-0027.1/WAF-D-20-0027.1.xml}, author = {KJ Tory and Jeffrey Kepert} }