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| Titel |
Inversion of tropospheric profiles of aerosol extinction and HCHO and NO2 mixing ratios from MAX-DOAS observations in Milano during the summer of 2003 and comparison with independent data sets |
| VerfasserIn |
T. Wagner, S. Beirle, T. Brauers, T. Deutschmann, U. Frieß, C. Hak, J. D. Halla, K. P. Heue, W. Junkermann, X. Li, U. Platt, I. Pundt-Gruber |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 4, no. 12 ; Nr. 4, no. 12 (2011-12-12), S.2685-2715 |
| Datensatznummer |
250002147
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| Publikation (Nr.) |
 copernicus.org/amt-4-2685-2011.pdf |
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| Zusammenfassung |
We present aerosol and trace gas profiles derived from MAX-DOAS
observations. Our inversion scheme is based on simple profile
parameterisations used as input for an atmospheric radiative transfer model
(forward model). From a least squares fit of the forward model to the
MAX-DOAS measurements, two profile parameters are retrieved including
integrated quantities (aerosol optical depth or trace gas vertical column
density), and parameters describing the height and shape of the respective
profiles. From these results, the aerosol extinction and trace gas mixing
ratios can also be calculated.
We apply the profile inversion to MAX-DOAS observations during a measurement
campaign in Milano, Italy, September 2003, which allowed simultaneous
observations from three telescopes (directed to north, west, south). Profile
inversions for aerosols and trace gases were possible on 23 days. Especially
in the middle of the campaign (17–20 September 2003), enhanced values of
aerosol optical depth and NO2 and HCHO mixing ratios were found. The
retrieved layer heights were typically similar for HCHO and aerosols. For
NO2, lower layer heights were found, which increased during the day.
The MAX-DOAS inversion results are compared to independent measurements: (1)
aerosol optical depth measured at an AERONET station at Ispra; (2)
near-surface NO2 and HCHO (formaldehyde) mixing ratios measured by long
path DOAS and Hantzsch instruments at Bresso; (3) vertical profiles of HCHO
and aerosols measured by an ultra light aircraft. Depending on the viewing
direction, the aerosol optical depths from MAX-DOAS are either smaller or
larger than those from AERONET observations. Similar comparison results are
found for the MAX-DOAS NO2 mixing ratios versus long path DOAS
measurements. In contrast, the MAX-DOAS HCHO mixing ratios are generally
higher than those from long path DOAS or Hantzsch instruments. The
comparison of the HCHO and aerosol profiles from the aircraft showed
reasonable agreement with the respective MAX-DOAS layer heights. From the
comparison of the results for the different telescopes, it was possible to
investigate the internal consistency of the MAX-DOAS observations.
As part of our study, a cloud classification algorithm was developed (based
on the MAX-DOAS zenith viewing directions), and the effects of clouds on the
profile inversion were investigated. Different effects of clouds on aerosols
and trace gas retrievals were found: while the aerosol optical depth is
systematically underestimated and the HCHO mixing ratio is systematically
overestimated under cloudy conditions, the NO2 mixing ratios are only
slightly affected. These findings are in basic agreement with radiative
transfer simulations. |
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