Principal Scientist Atmospheric and Environmental Research (AER) Lexington, Massachusetts
Biomass burning in Central America can significantly impact air quality in the United States. Specifically, the agricultural fire season in Mexico’s Yucatán Peninsula (Yucatán), extending from April to May, has been linked to multiple air pollution events in and around the US Gulf Coast states. Yet, characterizing regions impacted by biomass burning remains an ongoing challenge. In this study we explored different methods for determining the presence and amount of brown carbon aerosol (BrC) to identify biomass burning smoke intrusions into the Houston-Galveston-Brazoria (HGB) area from the Yucatán. We derive Absorption Ångstrom Exponent (AAE) and Extinction Ångstrom Exponent (EAE) using NASA’s Ozone Monitoring Instrument (OMI) measurements of aerosol optical depth at 1°×1°. We use the AAE/EAE ratio in the 354nm-388nm wavelength window to establish pixels likely characterized by high BrC and, therefore, biomass burning smoke. We analyzed data for 99 days between 2005 and 2020 with approximately half the days corresponding to a known or suspected smoke intrusion into the region. Using a k-means clustering algorithm, we find that pixels corresponding to AAE values of 4.5 (SD=0.4) and EAE values of 1.4 (SD=0.1) are likely impacted by BrC aerosol. Our analysis is supported by airmass trajectories modeled by NOAA’s HYSPLIT model and a suite of smoke and fire maps. Our analysis provides a method for stakeholders to identify smoke-impacted pixels and provide likely attribution to smoke source. Future development will include finer resolution measurements from the NASA TEMPO mission, scheduled for launch in 2022.
