How air pollution may look like from space?

Air pollution may have various looks and shapes depending on our eyes and used space-borne sensors to visualise it.

An example of India on 2019.01.18 which allows to observe a dark smoke, shielding the surface, heavy abundance of tiny particles aerosols retrieved from MODIS Terra, and high concentration of nitrogen dioxide – NO2 toxic gas from the Copernicus Sentinel-5 Precursor (S5P) TROPOMI sensor.

MODIS Terra RGB False colour composite, India 2019.01.18. Source NASA EODIS WorldView https://worldview.earthdata.nasa.gov/?p=geographic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,AIRS_CO_Total_Column_Day(hidden),OMI_Nitrogen_Dioxide_Tropo_Column(hidden),MODIS_Fires_Terra,MODIS_Terra_Aerosol_Optical_Depth_3km(hidden),Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2016-01-16&z=3&v=-144.91024116847828,-98.2219769021739,179.4795346467391,100.9030230978261

MODIS Terra Aerosol Optical Depth (AOD) (550 nm). Source: NASA EODIS WorldView https://worldview.earthdata.nasa.gov/?p=geographic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,AIRS_CO_Total_Column_Day(hidden),OMI_Nitrogen_Dioxide_Tropo_Column(hidden),MODIS_Fires_Terra,MODIS_Terra_Aerosol_Optical_Depth_3km(hidden),Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2016-01-16&z=3&v=-144.91024116847828,-98.2219769021739,179.4795346467391,100.9030230978261

Tropospheric NO2 vertical column density from Sentinel-5 Precursor TROPOMI, India 2019.01.18. Source: Copernicus SentinelHub https://sentinel-hub.com

But a lot of times air pollution is not directly “visible” with our eyes. A special zoom of 2019.01.15 with TROPOMI on two cities that I know well in South West France, Bordeaux and Toulouse. Very clear NO2 pollution can be detected thanks to the fine pixels. Such isolated spots clearly suggest local emissions (mostly cars). Note also the hot-spots in the North of Spain (e.g. Bilbao, SanSebastian , Barcelona)