Development of speciated non-methane volatile organic compounds emissions and size-resolved primary light-absorbing aerosols emissions from wildfires

Description

Wildfires (i.e., open biomass burning of savanna, grasslands, and forests) are important sources of primary and secondary trace gases and aerosols which have significant impacts on air quality and the radiative balance of the atmosphere. Therefore, accurate wildfire emissions are critical to the performance of chemical transport models (CTMs) in understanding the role of wildfires in the atmosphere. Although a number of global wildfire datasets have been developed in the past two decades, there is still missing information for aerosol-related emissions such as complete speciated non-methane volatile organic compounds (NMVOC) and size-resolved primary light-absorbing aerosols. In this work, we develop methodology and global model-ready emission datasets of complete speciated NMVOCs and size-resolved primary light-absorbing aerosols for wildfires. We first develop the global gridded total NMVOC and primary aerosol emissions by wildfire type based on the high-resolution dry mass burned datasets of the Quick Fire Emission Dataset (QFED) v2.5. For the NMVOC part of the work, composite NMVOC profiles of individual wildfire types are first developed by carefully aggregating a wide range of measurements reported in literature. Particularly, the fractions of oxygenated volatile organic compounds (OVOC) are corrected in the composing process to minimize the impact of improper sampling and analysis of different studies. Using the developed NMVOC profiles and mechanism-dependent mapping tables, emissions of individual NMVOC species are then translated to lumped species of different chemical mechanisms used in CTMs. For the aerosol part of the work, aerosol size-distributions and light-absorbing composition fractions by wildfire type are first parameterized by unimodal or multimodal lognormal functions based on the literature searches. Combined with QFED aerosol emissions, size-resolved light-absorbing aerosol emissions are developed and are further distributed to size bins of different aerosol modules used in CTMs. This work improves the representation of speciated NMVOC emissions and size-resolved aerosol emissions from wildfires in CTMs. The potential improvements to the model performance will be examined in the future.