Bremen 2017 – scientific programme
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UP: Fachverband Umweltphysik
UP 9: Atmosphäre - Spurengase
UP 9.5: Talk
Wednesday, March 15, 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.