Hamburg 2009 – scientific programme

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UP: Fachverband Umweltphysik

UP 2: Atmosphäre II

UP 2.4: Talk

Tuesday, March 3, 2009, 14:54–15:06, VMP 9 HS

First measurements of stratomesospheric CO at mid-latitudes derived from ground-based FTIR measurements at Zugspitze and Garmisch — •Tobias Borsdorff, Markus Rettinger, and Ralf Sussmann — IMK-IFU, Research Center Karlsruhe

Measurements of stratomesospheric CO at mid-latitudes are essential to understand transport processes in the middle atmosphere. Due to the strong latitudinal gradient of stratomesospheric CO, large scale planetary wave activity during winter and spring can displace CO enriched polar air meridionally over large distances. Model calculations suggest that even mid-latitude regions exhibit enhanced abundances of CO in winter/spring. However previous mid-latitude FTIR measurements did not find any significant seasonal cycle. Therefore an optimized retrieval for mid-latitudes is presented, and the stratomesospheric CO partial column from 24 - 100 km is derived from FTIR measurements at Zugspitze for the time period 1999 to 2008. The derived time series show a pronounced annual cycle which is comparable to findings from the WACCM model on the monthly mean basis. In addition, on the daily scale, our measurements reveal many events of enhanced CO between November and March with levels comparable to inner-vortex conditions. Finally, by analysis of Garmisch FTIR data (744 m a.s.l.) we confirm that our new successful retrieval of mid-latitude mesospheric CO is not restricted to high mountain stations and thus applicable to all mid-latitude stations.