Direct Estimation of Carbon Emissions from High Latitude Fires: The Adapted FREM Approach

Landscape fires are a widespread natural phenomenon that directly influences carbon cycling through the combustion of organic material. Space-based remote sensing, including Active Fire (AF), remains the only way to estimate wildfire activity accurately on the regional-to-global scale. Fire emission inventories generally fall into two categories. “Bottom-up” methodologies rely on observations of AF counts, Fire Radiative Power (FRP), or burned area to estimate the amount of biomass burned, or “Top-down” methodologies, which directly relate observations of FRP to landscape fire emission estimates. Bottom-up methods tend to have a reliance on uncertain parameters, such as pre-fire fuel load and combustion completeness, or a conversion factor between FRP and fuel consumption rate. The Fire Radiative Energy Emission (or FREM) approach is one such top-down methodology that has removed such a reliance, by directly relating FRP to observed rates of emissions, such as CO or aerosols, but has so far been used with geostationary FRP data only. Whilst very effective at lower latitudes, due to the poor spatial resolution and extreme viewing geometry of geostationary data at higher latitudes, the approach is not applicable for fires in this region in its current format. However, by using polar orbiting FRP data and making use of the high latitude orbital convergence, this study looks to adapt the FREM approach to deliver direct estimation of carbon emissions for high latitude (>60°N) landscape fires. We use direct observations of FRP, from Suomi-NPP, NOAA-20 and MODIS, along with observations of Total Column Carbon Monoxide from TROPOMI onboard Sentinel-5P. A series of cloud-free plumes and associated FRP data were identified in Deciduous and Evergreen Needleleaf biomes in North America and Russia in the summers of 2019 – 2023. The resulting emission coefficients and emission totals were compared to pre-existing top-down and bottom-up emission coefficients and totals from the FEER, GFAS, and GFED inventories for high latitude fires between 2018-2023. This adapted FREM approach is shown to provide direct emission estimates without recourse to significant assumptions and can do so in real time – opening up a new avenue for real-time fire emission estimation at high latitudes.