Satellite-Based CO and NOx Emission Estimates from South-Central Chilean Plantation Fires

Manuel Perez-Carrasco , Qindan Zhu, Cecilia Garraffo, Xiong Liu, Jia Chen

We present top-down CO and NOx emission estimates for a south-central Chilean fire from Sentinel-5P/TROPOMI observations. Applying the Cross-Sectional Flux method to CO and the Exponentially Modified Gaussian method to NO2, with uncertainty propagated through 500-member Monte Carlo ensembles, we retrieve a median CO flux of 1,273 kg s⁻¹ (95% CI: 676–1,843 kg s⁻¹) and a median NOx flux of 7,505 g s⁻¹ (95% CI: 3,620–9,655 g s⁻¹) on the peak fire day. Against the hourly Copernicus Atmosphere Monitoring Service Global Fire Assimilation System (GFAS) inventory, the top-down median CO flux is 21 times GFAS for the overpass hour and 4.1 times its local-day mean. The top-down NOx flux is 2.4 times GFAS at the overpass hour but 52% below its local-day mean, and the retrieved CO:NOx ratio is 8.5–8.7 times the GFAS ratio in both cases. GFAS sets its ratio with generic extratropical-forest and savanna emission factors; its forest NOx emission factor is 2.5 times a TROPOMI-derived temperate-forest value. To map the region affected by the smoke, we drove a Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) forward dispersion simulation with the retrieved CO flux: the plume traveled more than 2,000 km north-northwestward within 96 hours, along the Chilean coast and over the subtropical southeast Pacific, where TROPOMI observed enhanced CO.