Title
Full-azimuthal imaging-DOAS observations of NO2 and O4 during CINDI-2
Author
Peters, E.
Ostendorf, M.
Bösch, T.
Seyler, A.
Schönhardt, A.
Schreier, S.F.
Henzing, J.S.
Wittrock, F.
Richter, A.
Vrekoussis, M.
Burrows, J.P.
Publication year
2019
Abstract
A novel imaging-DOAS (differential optical absorption spectroscopy) instrument IMPACT (Imaging MaPper for AtmospheriC observaTions) is presented combining full-azimuthal pointing (360◦) with a large vertical coverage (∼41◦). Complete panoramic scans are acquired at a temporal resolution of ∼15min, enabling the retrieval of NO2 vertical profiles over the entire panorama around the measurement site. IMPACT showed excellent agreement (correlation > 99%) with coincident multiaxis DOAS (MAX-DOAS) measurements during the Second Cabauw Intercomparison of Nitrogen Dioxide measuring Instruments (CINDI-2)campaign. The temporal variability of NO2 slant columns within a typical MAX-DOAS vertical scanning sequence could be resolved and was as large as 20% in a case study under good viewing conditions. The variation of corresponding profiles and surface concentrations was even larger (40%). This variability is missed when retrieving trace gas profiles based on standard MAX-DOAS measurements. The azimuthal distribution of NO2 around the measurement site showed inhomogeneities (relative differences) up to 120% (on average 35%) on short timescales (individual panoramic scans). This is more than expected for the semirural location. We explain this behavior by the transport of pollution. Exploiting the instrument’s advantages, the plume’s trajectory during a prominent transport event could be reconstructed. Finally, the potential for retrieving information about the aerosol phase function from O4 slant columns along multiple almucantar scans of IMPACT is demonstrated, with promising results for future studies.
Subject
Environment & Sustainability
Urbanisation
Aerosol composition
Air sampling
Atmospheric plume
Atomic absorption spectroscopy
Azimuth
Imaging method
Nitrogen dioxide
Optical depth
Ozone
Trace gas
To reference this document use:
http://resolver.tudelft.nl/uuid:3d523df2-7c3a-438b-8afd-78db51264d04
DOI
https://doi.org/10.5194/amt-12-4171-2019
TNO identifier
869840
Publisher
Copernicus
ISSN
1867-1381
Source
Atmospheric Measurement Techniques, 12 (8), 4171-4190
Document type
article