TROPOMI Level 2 Nitrogen Dioxide (NO2), Total And Tropospheric Columns Products in NRT - Sentinel-5P

Abstract:
The TROPOMI NO2 retrieval consists of a three-step procedure, performed on each measured Level-1b spectrum: 1. the retrieval of a total NO2 slant column density (Ns) from the Level-1b radiance and irradiance spectra measured by TROPOMI using a DOAS (Differential Optical Absorption Spectroscopy) method, 2. the separation of the Ns into a stratospheric (N strat s) and a tropospheric (N trop s) part on the basis of information coming from a data assimilation system, and 3. the conversion of the tropospheric slant column density (N trop s) into a tropospheric vertical column density (N trop v) and the computation of the averaging kernel (A), by applying an appropriate AMF based on a look-up table of altitude-dependent AMFs and actual, daily information on the vertical distribution of NO2 from the TM5-MP model on a 1×1 grid. The altitude-dependent AMF depends on the satellite geometry, terrain eight, cloud fraction and height and surface albedo.