Infrared CO₂ cooling of the middle and upper atmosphere is increasing. We developed a new routine for very fast and accurate calculations of this cooling in general circulation models. The new algorithm accounts for non-local thermodynamic equilibrium and is about 1000 times faster than the standard matrix algorithms. It is based on advanced techniques for non-equilibrium emission calculations in stellar atmospheres, which so far have not been used in Earth’s and planetary atmospheres.

The Earth's nighttime radiation in the range from the near-UV to the near-IR mainly originates between 75 and 105 km and consists of lines of different species, which are important indicators of the chemistry and dynamics at these altitudes. Based on astronomical spectra, we have characterised the structure and variability of a pseudo-continuum of a high number of faint lines and discovered a new emission process in the near-IR. By means of simulations, we identified HO₂ as the likely emitter.

Line emission from hydroxyl (OH) molecules at altitudes of about 90 km strongly contributes to the Earth's night-sky brightness and is therefore used as an important indicator of atmospheric chemistry and dynamics. However, interpreting the measurements can be ambiguous since necessary molecular parameters and the internal state of OH are not well known. Based on high-quality spectral data, we investigated these issues and found solutions for a better understanding of the OH line intensities.

Gravity waves can link together atmospheric conditions over large distances. MATS is a new Swedish satellite that will study gravity waves at altitudes around 80–110 km. MATS will take images of emissions from excited molecules, so-called airglow, and of the highest clouds in our atmosphere, so-called noctilucent clouds. These measurements will be analysed to provide three-dimensional wave structures and a comprehensive picture of wave interactions in the atmosphere.

Sounding rockets are the only means of measuring small-scale structures (i.e., spatial scales of kilometers to centimeters) in the Earth's middle atmosphere (50–120 km). We present and analyze brand-new high-resolution measurements of atomic oxygen (O) concentration together with high-resolution measurements of ionospheric plasma and neutral air parameters. We found a new behavior of the O inside turbulent layers, which might be essential to adequately model weather and climate.