MAX-DOAS measurements of tropospheric NO2 and HCHO in Munich and the
comparison to OMI and TROPOMI satellite observations
Chan, K. L., Wiegner, M., van Geffen, J.,
De Smedt, I., Alberti, C., Cheng, Z., Ye, S. and Wenig, M.: 2020,
Atmos. Meas. Tech. 13, 4499-4520.
Abstract
We present two-dimensional scanning Multi-AXis Differential Optical
Absorption Spectroscopy (MAX-DOAS) observations of nitrogen dioxide (NO2)
and formaldehyde (HCHO) in Munich. Vertical columns and vertical
distribution profiles of aerosol extinction coefficient, NO2 and HCHO are
retrieved from the 2D MAX-DOAS observations. The measured surface aerosol
extinction coefficients and NO2 mixing ratios derived from the retrieved
profiles are compared to in situ monitoring data, and the surface NO2 mixing
ratios show a good agreement with in situ monitoring data with a Pearson
correlation coefficient (R) of 0.91. The aerosol optical depths
(AODs) show good agreement as well (R=0.80) when compared to sun
photometer measurements. Tropospheric vertical column densities (VCDs) of
NO2 and HCHO derived from the MAX-DOAS measurements are also used to
validate Ozone Monitoring Instrument (OMI) and TROPOspheric Monitoring
Instrument (TROPOMI) satellite observations. Monthly averaged data show a
good correlation; however, satellite observations are on average 30% lower
than the MAX-DOAS measurements. Furthermore, the MAX-DOAS observations are
used to investigate the spatiotemporal characteristic of NO2 and HCHO in
Munich. Analysis of the relations between aerosol, NO2 and HCHO shows higher
aerosol-to-HCHO ratios in winter, which reflects a longer atmospheric
lifetime of secondary aerosol and HCHO during winter. The analysis also
suggests that secondary aerosol formation is the major source of these
aerosols in Munich.
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created: 19 August 2020
last modified: 23 September 2020