Local comparisons of tropospheric ozone: Vertical soundings at two neighbouring stations in Southern Bavaria

Abstract. In this study ozone profiles of the differential-absorption lidar at Garmisch-Partenkirchen are compared with those of ozone sondes of the Forschungszentrum Jülich and of the Meteorological Observatory Hohenpeißenberg (German Weather Service). The lidar measurements are quality assured by the highly accurate in-situ measurements at nearby the Wank (1780 m a.s.l.) and Zugspitze (2962 m a.s.l.) summits and at the Global Atmosphere Watch station Schneefernerhaus (2670 m a.s.l.). The lidar results agree almost perfectly with those of the monitoring stations. Side-by-side sounding of the lidar and electrochemical (ECC) sonde measurements by a team of the Forschungszentrum Jülich shows just small positive offsets (≤ 3.4 ppb), almost constant within the troposphere. We conclude that the recently published uncertainties of the lidar in the final configuration since 2012 are realistic and rather small for low to moderate ozone. Comparisons with the Hohenpeißenberg routine Brewer-Mast sonde measurements are more demanding because of the distance of 38 km between both sites. These comparisons cover the three years September 2000 to August 2001, 2009 and 2018. A slight negative average offset (-3.64 ppb ± 7.5 ppb (full error)) of the sondes with respect to the lidar is found. Most sonde measurements could be improved in the troposphere by recalibration with the station data. This would not only remove the average offset, but also greatly reduce the variability of the individual offsets. The comparison for 2009 suggests a careful partial re-evaluation of the lidar measurements between 2007 and 2011 for altitudes above 6 km where an occasional negative bias occurred.