Biomass burning nitrogen dioxide emissions derived from space with TROPOMI: methodology and validation

Abstract

Abstract. Smoke from wildfires is a significant source of air pollution, which can adversely impact air quality and ecosystems downwind. With the recently increasing intensity and severity of wildfires, the threat to air quality is expected to increase. Satellite-derived biomass burning emissions can fill in gaps in the absence of aircraft or ground-based measurement campaigns and can help improve the online calculation of biomass burning emissions as well as the biomass burning emissions inventories that feed air quality models. This study focuses on satellite-derived NOx emissions using the high-spatial-resolution TROPOspheric Monitoring Instrument (TROPOMI) NO2 dataset. Advancements and improvements to the satellite-based determination of forest fire NOx emissions are discussed, including information on plume height and effects of aerosol scattering and absorption on the satellite-retrieved vertical column densities. Two common top-down emission estimation methods, (1) an exponentially modified Gaussian (EMG) and (2) a flux method, are applied to synthetic data to determine the accuracy and the sensitivity to different parameters, including wind fields, satellite sampling, noise, lifetime, and plume spread. These tests show that emissions can be accurately estimated from single TROPOMI overpasses. The effect of smoke aerosols on TROPOMI NO2 columns (via air mass factors, AMFs) is estimated, and these satellite columns and emission estimates are compared to aircraft observations from four different aircraft campaigns measuring biomass burning plumes in 2018 and 2019 in North America. Our results indicate that applying an explicit aerosol correction to the TROPOMI NO2 columns improves the agreement with the aircraft observations (by about 10 %–25 %). The aircraft- and satellite-derived emissions are in good agreement within the uncertainties. Both top-down emissions methods work well; however, the EMG method seems to output more consistent results and has better agreement with the aircraft-derived emissions. Assuming a Gaussian plume shape for various biomass burning plumes, we estimate an average NOx e-folding time of 2 ±1 h from TROPOMI observations. Based on chemistry transport model simulations and aircraft observations, the net emissions of NOx are 1.3 to 1.5 times greater than the satellite-derived NO2 emissions. A correction factor of 1.3 to 1.5 should thus be used to infer net NOx emissions from the satellite retrievals of NO2.

Carbon Monoxide in Optically Thick Wildfire Smoke: Evaluating TROPOMI Using CU Airborne SOF Column Observations

“…Data from the ultraviolet–visible (UV–vis) detector on TROPOMI have been used to derive biomass burning trace gas emissions and lifetimes, , proxies for combustion efficiency, and to study direct emissions of CO (e.g., Borsdorff et al and Vellalassery et al). However, to the best of our knowledge, direct comparisons of TROPOMI CO columns with aircraft column measurements for biomass burning events have not yet been performed and hold the potential to improve the characterization of global wildfire emissions.…”

“…CO columns are vertical concentration integrals and are further integrated horizontally across the plumes; the data are then time-aligned with dispersion models − to correct for the downwind transport of CO. While in situ and column CO measurements have both been successfully used to normalize the relative abundances of trace gases and aerosols in wildfire smoke (e.g., Akagi et al; Andreae; Kille et al), satellite measurements of CO in context of other trace gases ,− require to consider radiative transfer, , in particular the wavelength dependence of aerosol scattering and absorption of solar photons in the smoke plume. Section describes active measures taken in this study to deal with the fundamental sampling challenge in time and space, and introduces case studies and radiative transfer simulation tools used to assess the (multispectral) effects of aerosols in thick wildfire smoke.…”

County-level ammonia emissions monitored worldwide

“…This relation is then calculated for all observations in respect to the location of each potential source to establish a linear Ax=b system, in which A is a matrix (with size N observations by M sources) of plume functions, x is a vector (M sources) with the source enhancements, and b vector (N observations) is the observed total column concentrations. Here we use the Exponentially Modified Gaussian (EMG) plume function to calculate the source-receptor relations 20,77,[80][81][82][83] . The EMG plume function describes the vertical column density downwind of a source (eq.…”

“…First, the plume spread and lifetime parameters. In earlier studies on single source plume fits 20,80,81,88 it is stated that the plume spread and lifetime parameters are not entirely independent in the fitting. In most cases the lifetime is underestimated for the EMG method, which in combination with Dammers et al (2019) 20 reporting on sources that were often far away from other sources, can explain the difference in the lifetime found 2022) 77 , we assume a plume spread of 15 km with a standard deviation 2 km to account for pure area sources and pure point sources.…”

Impact of Hurricane Ida on Nitrogen Oxide Emissions in Southwestern Louisiana Detected from Space

“…This study presents a quantitative analysis of top-down derived NO x emission changes in two urban areas in Louisiana, New Orleans and Baton Rouge, affected by Hurricane Ida. An exponentially modified Gaussian (EMG) function is utilized to estimate the NO x emission changes to illustrate its use for quick quantification of the complex emission dynamics caused by short-lived extreme weather events. − The results shown here are from the first analysis quantifying hurricane-driven emission changes of anthropogenically produced NO x using the EMG function.…”