Application of CO as a tracer for dynamics in the polar winter middle atmosphere: A study based on ground-based microwave observations in Kiruna

Abstract

The central point of this thesis is the application of middle atmosphere CO as tracer for polar dynamics and its variability. A time series of vertical CO profiles covering the two winters 2008/2009 and 2009/2010 is retrieved from ground-based microwave observations obtained in Kiruna, northern Sweden. The dataset provides information between 40 and 80km altitude. All major features of the polar winter dynamics are identified in the obtained time series. A comparison of time-averaged CO profiles of the KIMRA dataset with all recent satellite datasets (MLS, ACE-FTS, and MIPAS) is presented. The representation of the polar middle atmosphere dynamics in the comprehensive atmospheric model SD-WACCM4 is validated. This model version has recently been developed, so that the comparison with observations presented here is among the first. Model studies are carried out to clarify the meaning of the descent rates of mesospheric air, which have been derived from CO time series. It is proposed that the descent rates might be interpreted as the effective velocity of mesospheric air.