Using Geostationary-Derived Sub-Daily FRP Variability vs. Prescribed Diurnal Cycles: Impact of African Fires on Tropospheric Ozone

Abstract. Assessing the impact of biomass burning (BB) emissions on tropospheric ozone is critical for effective air pollution control. BB emission inventories like GFED and GFAS, typically based on sun-synchronous satellite observations, report emissions on daily, weekly or longer timescales with empirically derived factors generally used to overlay diurnal variations. To explore the sensitivity of tropospheric ozone to diurnal variability, we incorporated day-specific hourly biomass burning variations, inferred from geostationary satellite data, into the GEOS-Chem atmospheric chemistry transport model. We compare our results to those obtained with established emission inventories, and evaluate them against in situ and satellite observations of tropospheric ozone and nitrogen dioxide (NO₂). We find that our simulations with real hourly-resolved emissions slightly reduce surface ozone biases (−1.54 to +9.09 ppbv vs. −1.58 to +9.13 ppbv) and enhance correlations with TROPOMI NO₂ (r = 0.80–0.89) and OMI ozone (r = 0.80–0.94) compared to simulations that use BB emission inventories with fixed diurnal cycles. Data-driven diurnal BB variations across Africa lead to significant differences in surface ozone (−8.57 to +21.88 ppbv) and alter tropospheric ozone columns by -0.41 to 1.09 DU, particularly in regions with most intense fire activity like Angola and Zambia. These changes propagate globally via atmospheric circulation, shifting regional OH concentrations by −4.4 % to +51.7 %. These findings emphasize the critical role of accurately describing diurnal BB variations in atmospheric modelling to improve quantitative understanding of atmospheric composition impacts, providing insights for Earth system model development and use of geostationary-derived BB emissions datasets.