This session aims to present research activities and instrument developments in the field of atmospheric remote sensing, particularly emphasising Multi-AXis (MAX-) DOAS and (hyper-) spectral imaging techniques which use scattered sunlight as a light source. Contributions from other passive and active DOAS applications are also welcome.
Differential Optical Absorption Spectroscopy (DOAS) was originally developed to retrieve column densities of atmospheric trace gases. Nowadays, DOAS systems exist in a large setup variety with different operating modes being capable of retrieving the vertical and the horizontal distribution of atmospheric trace gas concentrations and aerosol extinction with high accuracy. While MAX-DOAS instruments utilise scattered sunlight, there are also active DOAS applications hosting their own light source, further improving the accuracy at the cost of setup simplicity.
Spectral imaging techniques can vastly enhance the spatio-temporal information content of atmospheric trace gas measurements, often by a trade-off between spectral and spatio-temporal resolution. They are particularly useful to observe stronger spatial gradients of trace gas column densities in the atmosphere, which can, for instance, largely improve the retrieval of mass fluxes at point sources, such as power plants, volcanoes, or vehicles. The increased spatio-temporal resolution of imaging techniques also adds information on the context of the atmospheric measurements (e.g., cloudiness, horizon line, wind conditions).
MAX-DOAS and spectral trace gas imaging techniques provide an essential link between in-situ measurements of trace gas concentrations or reported point source emissions and column-integrated measurements from satellites. They play a key role in satellite validation and are found to be a valuable addition to global measurement networks.
To assure consistency between different DOAS and imaging instruments, intercomparison measurements were carried out during the CINDI3 campaign (Cabauw, Netherlands) in spring 2024. Contributions from this recent campaign are particularly welcome.