Long-term trends in air quality in major cities in the UK and India: a view from space

Abstract. Air quality networks in cities can be costly and inconsistent typically monitor a few pollutants. Space-based instruments provide global coverage spanning more than decade to determine trends air quality, augmenting surface networks. Here we target the UK (London Birmingham) India (Delhi Kanpur) use observations of nitrogen dioxide (NO2) from Ozone Monitoring Instrument (OMI), ammonia (NH3) Infrared Atmospheric Sounding Interferometer (IASI), formaldehyde (HCHO) OMI as proxy for non-methane volatile organic compounds (NMVOCs), aerosol optical depth (AOD) Moderate Resolution Imaging Spectroradiometer (MODIS) PM2.5. We assess skill these products at reproducing monthly variability concentrations pollutants where available. find temporal consistency between column NO2 (R = 0.5–0.7) NH3 two three rural sites but not AOD PM2.5 < 0.4). MODIS is consistent with AERONET ? 0.8) reproduces significant decline London (2.7 % a?1) Birmingham (3.7 since 2009. derive long-term four 2005–2018 2008–2018 IASI. Trends all are positive Delhi, suggesting no improvements there, despite roll-out controls on industrial transport sectors. Kanpur, identified by WHO most polluted city world 2018, experiences substantial (3.1 increase The NO2, NH3, likely due large part emissions vehicles. only Reactive NMVOCs Birmingham, trend significant. There recent (2012–2018) steep (> 9 reactive London. cause this rapid uncertain may reflect increased contribution oxygenated (VOCs) household products, food beverage industry, domestic wood burning, implications formation ozone VOC-limited city.