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56 CHAPTER 2. ATMOSPHERE AND REMOTE SENSING
inverted to obtain concentration distributions by tomographic techniques.
In contrast, the Airborne Multi AXis (AMAX) DOAS instrument measures passively the sunlight
which is scattered in the earths atmosphere and/or reflected on the ground (right figure). Several small
telescopes are used which are directed in various directions and which capture the light simultaneously.
Each measurement provides results from several different paths throughout the atmosphere. As the
aircraft moves on from measurement to measurement, data of many intersecting light paths is recorded.
First tomographic line-integrating indoor measurements of 2D trace gas distributions were realized
in the 1990s by using open-path Fourier infrared absorption spectroscopy. There have been improvements
in speed and spatial resolution since, but all experiments have been restricted to the laboratory
environment so far.
Main methods
During the last five years, for the first time DOAS two-dimensional tomographic experiments using a
larger number (10-90) of intersecting light paths have been carried out (e.g., Pundt [2005b]). At the
ground, long path active instruments were used to measure 2D emission plumes from road traffic or
horizontal distributions of trace gases (e.g. Pundt et al. [2005c], Lösch [2001], Kunz [2001], Bäuerle
[2004], Rippel [2005], Poehler et al. [2005]). Instruments which are more suitable for tomographic
applications were developed (Pundt & Mettendorf [2005], Mettendorf [2005]) and the reconstruction
methods were validated during an indoor campaign (Mettendorf et al. [2005]). From aircraft, passive
instruments were used to measure 2D distributions of a power plant emission plume (Pundt et al.
[2005a], Heue et al. [2005]). The quality of the localization and quantification of atmospheric emission
plumes has been estimated by means of numerical studies (Knab [2004], Laepple et al. [2004], Hartl
et al. [2005a]). In addition, the group participated in two measurement campaigns in the Po-Valley
region in the framework of the EU FORMAT project (e.g., Hak et al. [2005]).
Subprojects
Groundbased DOAS tomography
Airborne DOAS tomography
Theoretical studies
FORMAT: Formaldehyde as a Tracer of Photo oxidation in the Troposphere (EU project)
Funding
BMBF (TomDOAS)
EU (FORMAT)
Cooperation
University of Bremen
FZK Karlsruhe (IMK Karlsruhe)
IFU Garmisch-Partenkirchen (IMK Karlsruhe)
NILU (Norway)
IASB (Belgium)
PSI (Switzerland)
Anhui Institute (Hefei, China)
Publications
Peer reviewed Publications
1. Bruns et al. [2004]
2. Fix et al. [2005]
3. Hak et al. [2005]
4. Heckel et al. [2005]
5. Heue et al. [2005]
6. Laepple et al. [2004]
7. Pundt & Mettendorf [2005]