Simulating Forest Fire Plume Dispersion, Chemistry, and Aerosol Formation Using SAM-ASP version 1.0

Abstract

Biomass burning is a major source of trace gases and aerosols that can ultimately impact health, air quality, and climate. Global and regional-scale three-dimensional Eulerian chemical transport models (CTMs) use estimates of the primary emissions from fires and can unphysically mix them across large-scale grid boxes, leading to incorrect estimates of the impact of biomass 10 burning events. On the other hand, plume-scale process models allow for explicit simulation and examination of the chemical and physical transformations of trace gases and aerosols within biomass burning smoke plumes, and they may be used to develop parameterizations of this aging process for coarser grid-scale models. Here we describe the coupled SAM-ASP plume-scale process model, which consists of coupling the large-eddy simulation model, the System for Atmospheric Modelling (SAM), with the detailed gas and aerosol chemistry model, the Aerosol Simulation Program (ASP). We find that the SAM-ASP version 1.0 model 15 is able to correctly simulate the dilution of CO in a California chaparral smoke plume, as well as the chemical loss of NOx, HONO, and NH3 within the plume, the formation of PAN and O3, the loss of OA, and the change in the size distribution of aerosols as compared to measurements and previous single-box model results. The newly coupled model is able to capture the cross-plume vertical and horizontal concentration gradients as the fire plume evolves downwind of the emission source. The integration and evaluation of SAM-ASP version 1.0 presented here will support the development of parameterizations of near-source biomass 20 burning chemistry that can be used to more accurately simulate biomass burning chemical and physical transformations of trace gases and aerosols within coarser grid-scale CTMs.

Emissions of Trace Organic Gases From Western U.S. Wildfires Based on WE‐CAN Aircraft Measurements

“…For this reason, many laboratory studies provide EFs adjusted to reflect the field average MCE (Selimovic et al., 2018). Interestingly, aging effects may change the airborne EFs to levels that are perhaps more appropriate for the spatial and temporal resolution of many regions to global models (Lonsdale et al., 2020), but it is not simple to rule out the loss of smoldering emissions in airborne sampled fires (Akagi et al., 2014; Bertschi et al., 2003). Overall, using data from real wildfires makes sense, but lab studies can help characterize species rarely or not measured in the field, especially if they are adjusted to match field MCE or other steps are taken to increase representativeness (Selimovic et al., 2018; Yokelson et al., 2013).…”

“…To maximize sample numbers and improve statistics, here we choose to include all emission transects available and focus on discussing the campaign average with the potential aging effect reflected in part by the deviation. Additionally, EFs that include slight aging may be more appropriate for the spatial and temporal resolution in many models (Lonsdale et al., 2020). A more detailed breakdown of EFs and ERs by fire/transect with corresponding estimated physical age and MCE can be found in the supplement (Tables and ).…”

Photochemical Evolution of the 2013 California Rim Fire: Synergistic Impacts of Reactive Hydrocarbons and Enhanced Oxidants

“…Thus, if we wish to compare with observations, it is not adequate to represent the Rim Fire as a single Lagrangian plume. Detailed fire plume models have improved in recent years (Lonsdale et al, 2019), but observational constraints are limited compared to the complexity of such a model. The goal of our simulation is to obtain a meaningful 160 comparison against observations without over-elaboration (Box, 1976).…”