Forest Fire Aerosol – Weather Feedbacks over Western North America Using a High-Resolution, Fully Coupled, Air-Quality Model

Abstract

Abstract. The influence of both anthropogenic and forest fire emissions, and their and subsequent chemical and physical processing, on the accuracy of weather and air-quality forecasts, was studied using a high resolution, fully coupled air-quality model. Simulations were carried out for the period 4 July through 5 August 2019, at 2.5-km horizontal grid cell size, over a 2250 x 3425 km2 domain covering western Canada and USA, prior to the use of the forecast system as part of the FIREX-AQ ensemble forecast. Several large forest fires took place in the Canadian portion of the domain during the study period. A feature of the implementation was the incorporation of a new on-line version of the Canadian Forest Fire Emissions Prediction System (CFFEPSv4.0). This inclusion of thermodynamic forest fire plume-rise calculations directly into the on-line air-quality model allowed us to simulate the interactions between forest fire plume development and weather. Incorporating feedbacks resulted in improvements in most metrics of both air-quality and meteorological model forecast performance, through comparison of no-feedback and feedback simulations with surface, radiosonde, and satellite observations. For the meteorological simulations, these improvements occurred at greater than the 90 % confidence level. Relative to the climatological cloud condensation nuclei and aerosol optical properties used in the no-feedback simulations, the fully coupled model’s aerosol indirect and direct effects were shown to result in feedback loops characterized by increased surface temperatures, decreased lower troposphere temperatures, and increased lower troposphere cloud droplet and raindrop number densities. The aerosol direct and indirect effect reduced oceanic cloud droplet number densities and increased oceanic rain drop number densities, relative to the no-feedback climatological simulation. The aerosol direct and indirect effects were responsible for changes to the aerosol concentrations at greater than the 90 % confidence level throughout the model domain, and to NO2 and O3 concentrations within forest fire plumes. The simulations show that incorporating aerosol direct and indirect effect feedbacks can significantly improve the accuracy of weather and air quality forecasts, and that forest fire plume rise calculations within a fully coupled model changes the predicted fire plume dispersion and emissions, the latter through changing the meteorology driving fire behaviour and growth.

The Global Forest Fire Emissions Prediction System version 1.0

“…This would allow for the transcontinental transport of smoke emissions into the air-quality forecasts for Canada. Efforts are underway to link CFFEPS with a predictive fire-growth model (Anderson et al, 2009) and coupling the impact of smoke plumes generated by CFFEPS on ground temperatures as presented in public forecasts (Makar et al, 2020). Finally, initial steps have begun to link GFFEPS to the Canadian Earth System Model (CanESM5; Swart et al, 2019) and the Canadian fourth generation atmospheric 695 global climate model (CanAM4;von Salzen et al, 2019) for integrated study of climate driven impacts on regional wildfire risks, and air quality analysis.…”

“…the Horse River Fire, 2016) affected New York (Wu et al, 2018) and reached as far as the United Kingdom (Vaughan et al, 2018); similarly, the 2023 wildfires in Quebec were observed to transport across the Atlantic impacting air quality of many European communities. A recent study (Makar et al, 2020) showed the impact of forest fire smoke emissions from Eurasia on North American meteorology and air quality forecasting, 105 highlighting that un-nested continental-only scale air quality models show reduced skill during transoceanic smoke transport events. The impacts of intercontinental pollutant transport have also been demonstrated elsewhere in the literature (e.g., Huang et al, 2017).…”

“…wildfire emissions and regional weather to be simulated(Makar et al, 2020).https://doi.org/10.5194/gmd-2024-31 Preprint. Discussion started: 6 March 2024 c Author(s) 2024.…”

Profiles of Operational and Research Forecasting of Smoke and Air Quality Around the World

“…Active research is underway towards coupling CFFEPS with GEM-MACH for closer linkages between fire behavior and meteorology, and accounting for the direct and indirect feedbacks between air quality and meteorology (Makar et al, 2020;Ye et al, 2021). These research studies are part of the planned improvements to FireWork operational implementation which also include the introduction of dynamical interaction of plume aerosols with meteorology, hotspot aggregation methods, a data assimilation cycle for atmospheric constituents, and finer resolution domains.…”

Modeling Aerosol Effects on Liquid Clouds in the Summertime Arctic

“…In order to gauge the level of significance of the differences between the FB and FB-DMS runs, we computed the 90% confidence interval scores for each of the fields examined. The approach follows Makar et al (2021). Figures 3 and 4 compare the July 2014 mean column-integrated CDNC and LWC, respectively, and Figure 5 shows the column-averaged MMD.…”