München 2004 – scientific programme

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UP: Umweltphysik

UP 17: Poster: Atmosph
äre und Messtechnik

UP 17.5: Poster

Tuesday, March 23, 2004, 14:00–16:00, Schellingstr. 3

Formaldehyde and other trace gases retrieved by MAX-DOAS — •Tiberiu Tarsu, Andreas Heckel, Andreas Richter, Folkard Wittrock, and John Burrows — Otto-Hahn-Allee 1, Universitaet Bremen, D-28359 Bremen

The FORMAT (Formaldehyde as a tracer of oxidation in the troposphere) project represented an opportunity for the newly-developed concept of Multi Axis DOAS (MAX-DOAS) to determine volume mixing ratios in the lower troposphere. Tropospheric levels of several trace gases (HCHO, NO2 and O4) were investigated in the near-UV spectral region, employing zenith observations and four off-axis elevation angles close to the horizon. Atmospheric measurements were performed during two campaigns (summer 2002 and fall 2003) in the Po Valley (Northern Italy), a highly polluted, densely populated region, typical for midlatitudes urban areas. The results show that significant levels of HCHO and NO2 were present during the campaigns despite unusual weather conditions: holiday time (in 2002) and showers which prevented the accumulation of high atmospheric concentrations during both periods. For the days with clear sky conditions, slant columns of good quality can be retrieved. In order to calculate vertical columns realistic air mass factors have to be computed. Their quality is verified by comparing O4 columns for different elevation angles. Results indicate the presence of HCHO in the whole area, providing a picture of the horizontal and temporal distribution.