资源环境科技发展态势分析平台

Biomass burning emits an estimated 25 % of global annual nitrogen oxides (NO_x), an important constituent that participates in the oxidative chemistry of the atmosphere. Estimates of NO_x emission factors, representing the amount of NO_x per mass burned, are primarily based on field or laboratory case studies, but the sporadic and transient nature of wildfires makes it challenging to verify whether these case studies represent the behavior of the global fires that occur on earth. Satellite remote sensing provides a unique view of the earth, allowing for the study of emissions and downwind evolution of NO_x from a large number of fires. We describe direct estimates of NO_x emissions and lifetimes for fires using an exponentially modified Gaussian analysis of daily TROPOspheric Monitoring Instrument (TROPOMI) retrievals of NO₂ tropospheric columns. We update the a priori profile of NO₂ with a fine-resolution (0.25^∘) global model simulation from NASA's GEOS Composition Forecasting System (GEOS-CF), which largely enhances NO₂ columns over fire plumes. We derive representative NO_x emission factors for six fuel types globally by linking TROPOMI-derived NO_x emissions with observations of fire radiative power from Moderate Resolution Imaging Spectroradiometer (MODIS). Satellite-derived NO_x emission factors are largely consistent with those derived from in situ measurements. We observe decreasing NO_x lifetime with fire emissions, which we infer is due to the increase in both NO_x abundance and hydroxyl radical production. Our findings suggest promise for applying space-based observations to track the emissions and chemical evolution of reactive nitrogen from wildfires.