Rapidly Changing Emissions Drove Substantial Surface and Tropospheric Ozone Increases Over Southeast Asia

We combined observations and simulations to assess tropospheric ozone trends over Southeast Asia from 2005 to 2016. Multi-platform observations showed that surface ozone had been increasing at rates of 0.7-1.2 ppb year(-1) over the Peninsular Southeast Asia (PSEA) and 0.2-0.4 ppb year(-1) over the Maritime Continents (MC); tropospheric ozone columns had been rising throughout Southeast Asia by 0.21-0.35 DU year(-1). These observed ozone trends were better reproduced by simulations driven with satellite-constrained NOx emissions, indicating that NOx emission growths may have been underestimated for the PSEA and overestimated for the MC in the Community Emissions Data System and the Global Fire Emissions Data set. The surface ozone increases over the PSEA were driven by rapidly growing local emissions, wherein fire emission growths may still be underestimated even with satellite constraints. We highlighted the need for better quantifying Southeast Asian emissions to benefit air quality management.