Air quality is the combination of the presence of short-lived trace gases like O3 and NO2, and aerosols that affect human health, e.g. cause respiratory problems. Air quality is determined by the tropospheric chemical composition, and is mainly a local and regional phenomenon. From satellite measurements of tropospheric NO2 the sources and strengths of NO2 emissions can be determined.

Satellite observations
In our division we monitor globally the concentration of key components of tropospheric chemical composition, mainly tropospheric NO2 and ozone, from OMI, GOME-2 and SCIAMACHY. Data are available via TEMIS.

Groundbased observations
To validate the satellite measurements of tropospheric NO2, an NO2 sonde has been developed recently (Sluis et al., AMT, 2010). This sonde is a balloon borne NO2 sensor, which measures the vertical distribution of NO2. It is launched regularly from De Bilt or Cabauw. We also perform MAX-DOAS measurements to measure the tropospheric NO2 column from the surface (Vlemmix et al., AMT, 2010).