Investigating dominant characteristics of fires across the Amazon during 2005–2014 through satellite data synthesis of combustion signatures

Abstract

Estimates of fire emissions remain uncertain due to limited constraints on the variations in fire characteristics. Here we demonstrate the utility of space‐based observations of smoke constituents in addressing this limitation. We introduce a satellite‐derived smoke index (SI) as an indicator of the dominant phase of large‐scale fires. This index is calculated as the ratio of the geometric mean of observed fractional enhancements (due to fire) in carbon monoxide and aerosol optical depth to that of nitrogen dioxide. We assess the usefulness of this index on fires in the Amazon. We analyze the seasonal, regional, and interannual joint distribution of SI and fire radiative power (FRP) in relation to fire hotspots, land cover, Drought Severity Index, and deforestation rate estimates. We also compare this index with an analogous quantity derived from field data or emission inventories. Our results show that SI changes from low (more flaming) to high (more smoldering) during the course of a fire season, which is consistent with the changes in observed maximum FRPs from high to low. We also find that flaming combustion is more dominant in areas where deforestation fires dominate, while smoldering combustion has a larger influence during drought years when understory fires are more likely enhanced. Lastly, we find that the spatiotemporal variation in SI is inconsistent with current emission inventories. Although we recognize some limitations of this approach, our results point to the utility of SI as a proxy for overall combustion efficiency in the parameterization of fire emission models.

On the Role of the Flaming to Smoldering Transition in the Seasonal Cycle of African Fire Emissions

“…Since NO x is more efficiently produced at high MCE, the decrease of NO x emission factors could suggest a decrease in MCE during the late fire season, although we cannot rule out the influence from the declining nitrogen content in grasses as they senesce (Mebust & Cohen, ). Tang and Arellano () also observed an overall decrease in combustion efficiency across the fire season in the Amazon basin (with more forest fires than Africa) based on multiple satellite data sets. Despite the possible agreement, the magnitudes of MCE estimated in our study still remain uncertain.…”

Source Contributions to Carbon Monoxide Concentrations During KORUS‐AQ Based on CAM‐chem Model Applications

“…However, the two factors tend to cancel each other (Wiedinmyer et al, ). Tang and Arellano () suggested that treatment of emission factors in FINN (as well as other biomass burning emission inventories) introduces uncertainties into the emission estimates. Monks et al () showed that CO emissions in FINN are overestimated over Siberia and Myanmar.…”

Fire Regimes and Their Drivers in the Upper Guinean Region of West Africa

“…In Collection 6 of the MCD14ML product, FRP retrieval uses a radiance-based approach in which the 4-µm radiance of individual fire pixels and surrounding background pixels are compared [24,26]. FRP can be interpreted as a measure of biomass combustion rate, and is increasingly used by the atmospheric emissions modeling community to estimate vegetation burning emissions [27,28].…”