Mesospheric CO Intrusion in the Arctic Stratosphere

Unusually high amounts of CO (up to 450ppb) have been measured in the Arctic winter stratosphere during balloon flights of the JPL MkIV interferometer. High altitude CO is mainly produced from the photolysis of carbon dioxide in the lower thermosphere. It then follows the meridional circulation towards the winter hemisphere polar night region, where it accumulates and descends into the middle atmosphere. The photochemical lifetime of CO makes it an important indicator of vertical transport in the mesosphere. These measurements give further evidence of significant amounts of mesospheric air descending down to as low as 25-30km in the Arctic Polar vortex, which is not a well-observed phenomenon. Mesospheric air is also enhanced in reactive nitrogen compounds which can affect ozone. The ability of the MkIV instrument to simultaneously measure more than 30 different gases allows us to better quantify the impact of this phenomenon on the chemical composition of the polar stratosphere.