Combustion Efficiency Observed in California with CO and NO2 FIREX-AQ and TROPOMI Data

The 2020 California fire season yielded the largest fires in California history. TROPOMI nitrogen dioxide (NO2) and carbon monoxide (CO) ratios (i.e. mole density ratios; MDR) have been previously used to distinguish fire combustion among different vegetation types around the world. Here, we analyze the MDR from TROPOMI overpasses to identify fire characteristics over two regions of California where two wildfires were reported. We show that MDR calculated with TROPOMI NO2 and CO columns can be used to assess fire characteristics at the scale of counties through identifying the smoldering fires of the northern region and flaming fire of the southern region with a shift in the combustion at the end of September resulting from a change in fuel types. MDR calculation were also performed using FIREX-AQ aircraft measurements for identifying similar fire characteristics over the two regions. Improvement in the land cover maps and use of hourly data could help to better attribute MDR to specific fuel source categories.