Validation of smoke plume rise models using ground-based Lidar

Abstract

Biomass fires can significantly degrade regional air quality. Plume rise height is one of the critical factors determining the impact of fire emissions on air quality. Plume rise models are used to prescribe the vertical distribution of fire emissions which are critical input for smoke dispersion and air quality models. 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. A ground-based, mobile elastic scanning lidar (light detection and ranging) instrument and data-processing methodology have been developed at the Missoula Fire Science Laboratory to study the three-dimensional plume dynamics and the optical properties of smoke particles over large prescribed fires and wildfires. The lidar measurements are being used to validate several plume rise models, including the Briggs equations which are used in VSMOKE and other smoke management tools. We present the validation results and provide recommendations regarding application of the models to wildland fire. IntroductionTightening standards governing air quality have increased the pressure on land management agencies to address the air quality impact of wildland fire use and prescribed burning. Land management agencies need rigorously tested, accurate models to quantify the contribution of fire emissions to air pollution and visibility impairment.Accurately describing and predicting smoke plumes and subsequent smoke transport is a major uncertainty in determining the impact of fire emissions on air quality. While many smoke plume models exist, few smoke plume observational datasets are available to properly validate these models and quantitatively assess their uncertainties, biases, and application limits.We have initiated a research project to acquire the data needed for evaluation of plume rise and smoke dispersion models. The project deploys a ground based, mobile lidar and an airborne instrument package to investigate smoke plume dynamics, smoke aerosol distribution and chemical composition in and around active wildfires and large prescribed fires. Multiple wildland fires have been investigated over a two year period to measure plume rise and smoke transport over a wide range of meteorological, fire activity, fuel, and terrain conditions.We have developed a new lidar data processing technique based on the concept of the Atmospheric Heterogeneity Height Indicator (AHHI) that enables the automatic determination of plume heights and the processing of large volumes of data (Kovalev et al. 2010).