Stable isotopes in stratospheric carbon monoxide

The isotopes of an element provide a wealth of information for the chemistry and transport of trace gases in the atmosphere. In this work, the isotope composition of carbon and oxygen in carbon monoxide is used to gain new insights on transport and chemistry related to methane oxidation in the stratosphere. To date, sampling from the stratosphere is still difficult, which complicates the application of measurements. In the first part of this thesis, the development of a small lightweight sampling system called LISA is presented. A comparison for the concentration of trace gases, first with a different sampling technique, and then with simulations of two different general circulation models. Furthermore, this thesis shows that measured isotope composition of carbon monoxide can help to identify pollution in the stratosphere. A plume of smoke from a wildfire was sampled and analysed. The increased carbon monoxide concentration and its stable isotopes indicated the presence of the smoke in the stratosphere. In addition, it was shown that the degradation of carbon dioxide by light plays an important role for the carbon budget at high altitudes, with a substantially different isotope composition than the main carbon monoxide source in the stratosphere, methane. Furthermore, it was found that the oxygen isotope composition of carbon monoxide provides insight into the stratospheric methane degradation linked to ozone chemistry. Despite the fact that the budget for carbon monoxide and its stable isotope composition was understood, it also became clear that 3D simulations are needed to be able to simulate it properly