Biomass fires can significantly degrade regional air quality through the emission of primary aerosols and the photochemical production of ozone and secondary aerosols. The injection height of smoke from biomass burning into the atmosphere (‘plume rise height’) is one of the critical factors in determining the impact of fire emissions on air quality. Plume rise models are used to simulate plume rise height and prescribe the vertical distribution of fire emissions for input to smoke dispersion and air quality models. While several plume rise models exist, their uncertainties, biases, and application limits when applied to biomass fires are not well characterized. The poor state of model evaluation is due in large part to a lack of appropriate observational datasets. We have initiated a research project to address this critical observation gap. In August of 2013 we performed a multi-agency field experiment designed to obtain the data necessary to improve the air quality models used by agricultural smoke managers in the northwestern United States. In the experiment, the ground-based mobile lidar, developed at the US Forest Service Missoula Fire Science Laboratory, was used to monitor plume rise heights for nine agricultural fires in the northwestern United States. The lidar measurements were compared with plume rise heights calculated with the Briggs equations, which are used in several smoke management tools. Here we present the preliminary evaluation results and provide recommendations regarding the application of the models to agricultural burning based on lidar measurements made in the vicinity of Walla Walla, Washington, on August 24, 2013.
Biomass fires emit large amounts of trace gases and aerosols and these emissions are believed to significantly influence
the chemical composition of the atmosphere and the earth's climate system. At the Missoula Fire Sciences Laboratory
(FiSL), a MODIS direct broadcast (DB) receiving station is in place to demonstrate the potential for monitoring biomass
burning in near-real-time and predicting the impact of fire emissions on air quality. A burn scar algorithm that combines
active fire locations and burn scar detections for near 'real-time' measurement of fire burned areas has been developed
at the Missoula FiSL. Daily wildfire burned areas in western US provide crucial input for a prototype fire emissions -
smoke dispersion forecasting system.
Tunable lead-salt diode laser absorption spectroscopy (TDLAS) provides a sensitive and versatile probe for the study of the kinetics and mechanisms of atmospheric reactions. In our laboratory, the combination of laser flash photolysis with TDLAS detection of reactant and/or product species has proven useful in several studies of the gas phase oxidation of the atmospheric sulfur compound dimethylsulfide, a process which may play an important role in global climate modification/regulation. Typically a radical species is produced by UV laser photolysis of a stable precursor in a slowly flowing mixture of reactant and buffer gases. The concentration of this radical or a selected reaction product is then followed by TDLAS on a time scale of microseconds to milliseconds. This method allows direct determination of reaction rates and product branching ratios over a range of temperature, pressure and reactant concentrations in complete isolation from reactor surfaces.