Bremen 2017 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

UP: Fachverband Umweltphysik

UP 9: Atmosphäre - Spurengase

UP 9.5: Vortrag

Mittwoch, 15. März 2017, 18:00–18:15, GW2 B3009

Airborne remote sensing of NO₂ air pollution over the city of Zurich — •Gerrit Kuhlmann and Dominik Brunner — Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland

Nitrogen dioxide (NO₂) is an important air pollutant and plays a key role in the formation of photochemical smog. We used the airborne imaging spectrometer APEX to retrieved a high-resolution NO₂ map (50x50m²) over the city of Zurich during a flight campaign on 30th August 2013 (11:24-12:05 UTC).

The retrieval is based on a modified differential optical absorption spectroscopy (DOAS) algorithm, which retrieves NO₂ vertical column densities (VCD) from a wide spectral window (410-510 nm) making full use of APEX’s spectral range. To allow for a wide spectral window, we replaced the low-order polynomial traditionally used in DOAS with a cubic spline and applied wavelength-dependent air mass factors pre-calculated with the SCIATRAN radiative transfer model.

The new algorithm improves the quality of the fit and reduces the retrieval noise. NO₂ VCD errors are estimated to about 20% for polluted areas. The retrieved map shows enhanced NO₂ values in populated areas. Furthermore, we find increased NO₂ values near the exit of highway tunnels and along the trajectory of airplanes departing from Zurich airport.

In conclusions, airborne observations allow mapping of the NO₂ distribution in urban areas providing a different perspective on urban air quality which cannot be acquired by ground-based observations.