Influence of springtime biomass burning in South Asia on regional ozone (O3): A model based case study

Abstract

In this study, for the first time, the influence of springtime (MAM) biomass burning in South Asia on regional ozone (O3) distribution has been evaluated using a regional chemical transport model (WRF-Chem) and the Fire Inventory from NCAR (FINNv1). Model results are compared with satellite retrievals of tropospheric column amounts of carbon monoxide (CO) from MOPITT and nitrogen dioxide (NO2) from OMI. With daily varying emissions, the model captures reasonably well the satellite-derived temporal variations in CO and NO2 (index of agreement (R) for CO is 0.83 and for NO2 is 0.76), indicating the effectiveness of the model in estimating the overall fire impact on a regional scale. Simulated tropospheric NO2 concentration shows better agreement with the magnitude of observed NO2 when FINNv1 NOx emissions are reduced by a factor of 2.2 over the model domain. A clear increase in CO and NO2 levels over Burma (35–60%), Central India (15–30%), the Indo-Gangetic (15–25%) region and the Bay of Bengal (15–40%) are simulated with fire emissions. The model results are also used to quantify the net O3 production from fires. Calculated O3 productions are up to 4 ppb h−1 over inland and up to 0.1 ppb h−1 over marine regions respectively. Our model-based analysis yields average enhancement ratios ΔO3/ΔCO of 0.12 ppbv/ppbv and a total O3 production of about 3.5 Tg from South Asia during the spring season. The findings demonstrate that the springtime fire emissions in South Asia have a noticeable impact on the O3 in this region.