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| Titel |
Retrieval of tropospheric NO2 using the MAX-DOAS method combined with relative intensity measurements for aerosol correction |
| VerfasserIn |
T. Vlemmix, A. J. M. Piters, P. Stammes, P. Wang, P. F. Levelt |
| 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 ; 3, no. 5 ; Nr. 3, no. 5 (2010-10-04), S.1287-1305 |
| Datensatznummer |
250001292
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| Publikation (Nr.) |
 copernicus.org/amt-3-1287-2010.pdf |
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| Zusammenfassung |
Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a
technique to measure trace gas amounts in the lower troposphere from
ground-based scattered sunlight observations. MAX-DOAS observations are
especially suitable for validation of tropospheric trace gas observations
from satellite, since they have a representative range of several kilometers,
both in the horizontal and in the vertical dimension.
A two-step retrieval scheme is presented here, to derive aerosol corrected
tropospheric NO2 columns from MAX-DOAS observations. In a first step,
boundary layer aerosols, characterized in terms of aerosol optical thickness
(AOT), are estimated from relative intensity observations, which are defined
as the ratio of the sky radiance at elevation α and the sky
radiance in the zenith. Relative intensity measurements have the advantage of
a strong dependence on boundary layer AOT and almost no dependence on
boundary layer height. In a second step, tropospheric NO2 columns are
derived from differential slant columns, based on AOT-dependent air mass
factors.
This two-step retrieval scheme was applied to cloud free periods in a twelve
month data set of observations in De Bilt, The Netherlands. In a comparison
with AERONET (Cabauw site) a mean difference in AOT (AERONET minus MAX-DOAS)
of −0.01±0.08 was found, and a correlation of 0.85.
Tropospheric-NO2 columns were compared with OMI-satellite tropospheric
NO2. For ground-based observations restricted to uncertainties below 10%,
no significant difference was found, and a correlation of 0.88. |
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