Biomass burning combustion efficiency during the California 2020 fire season

The California fire season of 2020 was one of the most intense and damaging in the nations history. In order to understand the factors that worsened and intensified the fires, the fuel consumption of the fires and, specifically, the biomass burning combustion efficiency of these fires must be considered more closely. Studying this characteristic of fires gives more information about air quality and the amount of carbon released into the atmosphere which is becoming increasingly important in the context of climate change and its intensifying impact on wildfires. In this study, we examine the combustion efficiency of temperate forest, savanna, and agriculture vegetation types during the 2020 fire season for two locations in northern and southern California, focusing on the August Lightning Complex fire in the north and the Sequoia Lightning Complex fire in the more southern region. By utilizing TROPOspheric Measuring Instrument (TROPOMI) XCO and XNO2 column measurements in parallel with Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly data and Global Fire Emissions Database (GFED4s) fire vegetation type data, we can calculate the Mole Density Ratio for fires of different vegetation types which then serves as a proxy for combustion efficiency of the fires. This method will then give insight for how the characteristics of the fires differ regionally as well as temporally in how they change throughout the fire season and as it reaches the end of its lifetime. The MDR values we found show that combustion efficiency in the savanna vegetation shifted from flaming to smoldering over the lifetime of the fires. This shift is important to take into account for precision in the estimation of Emission Factors and therefore fire inventories.