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| Titel |
An improved tropospheric NO2 column retrieval algorithm for the Ozone Monitoring Instrument |
| VerfasserIn |
K. F. Boersma, H. J. Eskes, R. J. Dirksen, R. J. der A., J. P. Veefkind, P. Stammes, V. Huijnen, Q. L. Kleipool, M. Sneep, J. Claas, J. Leitão, A. Richter, Y. Zhou, D. Brunner |
| 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. 9 ; Nr. 4, no. 9 (2011-09-16), S.1905-1928 |
| Datensatznummer |
250002097
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| Publikation (Nr.) |
 copernicus.org/amt-4-1905-2011.pdf |
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| Zusammenfassung |
| We present an improved tropospheric nitrogen dioxide column retrieval
algorithm (DOMINO v2.0) for OMI based on better air mass factors (AMFs) and a
correction for across-track stripes resulting from calibration errors in the
OMI backscattered reflectances. Since October 2004, NO2 retrievals from
the Ozone Monitoring Instrument (OMI), a UV/Vis nadir spectrometer onboard
NASA's EOS-Aura satellite, have been used with success in several scientific
studies focusing on air quality monitoring, detection of trends, and NOx
emission estimates. Dedicated evaluations of previous DOMINO tropospheric
NO2 retrievals indicated their good quality, but also suggested that the
tropospheric columns were susceptible to high biases (by 0–40%), probably
because of errors in the air mass factor calculations. Here we update the
DOMINO air mass factor approach. We calculate a new look-up table (LUT) for
altitude-dependent AMFs based on more realistic atmospheric profile
parameters, and include more surface albedo and surface pressure reference
points than before. We improve the sampling of the TM4 model, resulting in a
priori NO2 profiles that are better mixed throughout the boundary layer.
We evaluate the NO2 profiles simulated with the improved TM4 sampling as
used in the AMF calculations and show that they are highly consistent with in
situ NO2 measurements from aircraft during the INTEX-A and INTEX-B
campaigns in 2004 and 2006. Our air mass factor calculations are further
updated by the implementation of a high-resolution terrain height and a
high-resolution surface albedo climatology based on OMI measurements.
Together with a correction for across-track stripes, the overall impact of
the improved terrain height and albedo descriptions is modest (<5%) on
average over large polluted areas, but still causes significant changes
locally. The main changes in the DOMINO v2.0 algorithm follow from the new
LUT and the improved TM4 sampling that results in more NO2 simulated
aloft, where sensitivity to NO2 is higher, and amount to reductions in
tropospheric NO2 columns of up to 20% in winter, and 10% in summer over
extended polluted areas. We investigate the impact of aerosols on the NO2
retrieval, and based on a comparison of concurrent retrievals of clouds from
OMI and aerosols from MODIS Aqua, we find empirical evidence that OMI cloud
retrievals are sensitive to the presence of scattering aerosols. It follows
that an implicit correction for the effects of aerosols occurs through the
aerosol-induced cloud parameters in DOMINO, and we show that such an
empirical correction amounts to a 20 %AMF reduction in summer and ±10%
changes in winter over the eastern United States. |
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