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| Titel |
Accounting for surface reflectance in the derivation of vertical column densities of NO2 from airborne imaging DOAS |
| VerfasserIn |
Andreas Carlos Meier, Anja Schönhardt, Andreas Richter, Tim Bösch, André Seyler, Daniel Eduard Constantin, Reza Shaiganfar, Alexis Merlaud, Thomas Ruhtz, Thomas Wagner, Michel Van Roozendael, John P. Burrows |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250134660
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| Publikation (Nr.) |
 EGU/EGU2016-15404.pdf |
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| Zusammenfassung |
| Nitrogen oxides, NOx (NOx = NO + NO2) play a key role in tropospheric chemistry. In
addition to their directly harmful effects on the respiratory system of living organisms, they
influence the levels of tropospheric ozone and contribute to acid rain and eutrophication of
ecosystems. As they are produced in combustion processes, they can serve as an indicator for
anthropogenic air pollution.
In the late summers of 2014 and 2015, two extensive measurement campaigns were
conducted in Romania by several European research institutes, with financial support from
ESA. The AROMAT / AROMAT-2 campaigns (Airborne ROmanian Measurements of
Aerosols and Trace gases) were dedicated to measurements of air quality parameters utilizing
newly developed instrumentation at state-of-the-art. The experiences gained will help to
calibrate and validate the measurements taken by the upcoming Sentinel-S5p mission
scheduled for launch in 2016.
The IUP Bremen contributed to these campaigns with its airborne imaging DOAS
(Differential Optical Absorption Spectroscopy) instrument AirMAP (Airborne imaging
DOAS instrument for Measurements of Atmospheric Pollution). AirMAP allows retrieving
spatial distributions of trace gas columns densities in a stripe below the aircraft. The
measurements have a high spatial resolution of approximately 30 x 80 m2 (along x across
track) at a typical flight altitude of 3000 m. Supported by the instrumental setup and the large
swath, gapless maps of trace gas distributions above a large city, like Bucharest or Berlin, can
be acquired within a time window of approximately two hours. These properties
make AirMAP a valuable tool for the validation of trace gas measurements from
space.
DOAS retrievals yield the density of absorbers integrated along the light path of the
measurement. The light path is altered with a changing surface reflectance, leading to
enhanced / reduced slant column densities of NO2 depending on surface properties. This
effect must be considered in the derivation of air mass factors used to convert the
measurements into vertical columns. Due to the high-resolution measurements, no data
product of surface reflectance with sufficient spatial resolution is available. Thus the surface
reflectance is estimated from AirMAP’s own spectra.
In this work the results of the research flights will be presented. The study focuses on the
validation of AirMAP’s measurements by comparison to other ground-based platforms like
(mobile) MAX-DOAS measurements. Conclusions will be drawn on the quality of the
measurements, their applicability for satellite data validation and possible improvements for
future measurements. |
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