A new approach for monthly updates of anthropogenic sulfur dioxide emissions from space: Application to China and implications for air quality forecasts

SO2emissions, the largest sourceof anthropogenic aerosols, can respond rapidly toeconomic and policy driven changes. However, bottom-up SO2 inventories have inherent limitations owing to 24–48months latency and lack of month-to-month variation in emissions (especially in developing countries). This study develops a new approach that integrates OzoneMonitoring Instrument (OMI) SO2 satellitemeasurements and GEOS-Chem adjoint model simulations to constrain monthly anthropogenic SO2 emissions. The approach's effectiveness is demonstrated for 14months in East Asia; resultant posterior emissions not only capture a 20% SO2 emission reduction in Beijing during the 2008 Olympic Games but also improve agreement between modeled and in situ surface measurements. Further analysis reveals that posterior emissions estimates, compared to the prior, lead to significant improvements in forecasting monthly surface and columnar SO2. With the pending availability of geostationary measurements of tropospheric composition, we show that it may soon be possible to rapidly constrain SO2 emissions and associated air quality predictions at fine spatiotemporal scales.