Source-Impact Forecasting for Dynamic Air Quality Management: Application to Prescribed Burn Management

Abstract

The newly developed weather-based prescribed burn forecasting capability presents new opportunities for dynamic air quality management. Forecasting of burn emissions has been incorporated into the HiRes-2 Air Quality Forecasting System. Forecasts are being produced daily for air quality and the impacts of power plant, traffic and prescribed burn emissions. The ultimate goal is to integrate these air quality forecasts into the burn permitting operations.

Questioner: Paul Makar

Question: Are there any observations to suggest that the smoke plumes are affecting the PBL height downwind? If so, how might this affect your forecasts?

Answer: This is a very important issue as the interaction between the plume and the boundary layer is quite complex. Gases and particles in a smoke plume may significantly change the optical properties of the atmospheric layer occupied by the plume. Through radiation, this may affect the boundary layer height downwind as well as the mixing of the smoke plume. To my knowledge, there are no observations to verify these hypotheses. However, there is modeling evidence that cannot be ignored. For example, using a two-way coupled meteorology and air quality modeling system, WRF-CMAQ, Wong et al. (2012) have shown that when particulate matter concentrations reach significant levels due to wildfires, direct radiative effects, primarily scattering and absorption of incoming radiation, result in a reduction of short-wave radiation reaching the surface, causing a reduction in surface temperatures as well as a reduction in PBL heights downwind. Whether prescribed burns, which are of lower intensity compared to wildfires, can create such effects is yet to be demonstrated. In our present forecasting system, the meteorology is not coupled to air quality; only air quality is coupled to meteorology. In other words, the meteorological model does not know the presence of smoke plumes. Therefore, no changes in PBL height occur due to prescribed burns. Our plans for the future include upgrading to a two-way coupled modeling system such as WRF-CMAQ. Once we do that, we would be in a much better position to answer your question.