Photochemistry and transport of carbon monoxide in the middle atmosphere: constraints from satellite observations

We present an analysis of the photochemisty and transport of carbon monoxide (CO) in the stratosphere and mesosphere using observations from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS). For the first time, simultaneous measurements of most of the reactive species involved in regulating the photochemical production and loss of CO are available from these two experiments, including OH, H2O, CH4, and O3. Interactions between photochemistry and transport in the stratopause region will be discussed as they relate to the observed distribution of CO, and to the thermal structure and evolution of the stratopause. A particular focus will be on diagnosing the downward transport from the mesosphere into the stratospheric polar vortex during the early stages of vortex development, including interannual and interhemispheric variability. Photochemistry, transport and radiation interactions during stratospheric sudden warmings will also be explored.