Investigating differences in DOAS retrieval codes using MAD-CAT campaign data

The differential optical absorption spectroscopy (DOAS) method is a well-known remote sensing technique that is nowadays widely used for measurements of atmospheric trace gases, creating the need for harmonization and characterization efforts. In this study, an intercomparison exercise of DOAS retrieval codes from 17 international groups is presented, focusing on NO2 slant columns. The study is based on data collected by one instrument during the MultiAxis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) in Mainz, Germany, in summer 2013. As data from the same instrument are used by all groups, the results are free of biases due to instrumental differences, which is in contrast to previous intercomparison exercises. While in general an excellent correlation of NO2 slant columns between groups of > 99.98% (noon reference fits) and > 99.2% (sequential reference fits) for all elevation angles is found, differences between individual retrievals are as large as 8% for NO2 slant columns and 100% for rms residuals in small elevation angles above the horizon. Comprehensive sensitivity studies revealed that absolute slant column differences result predominantly from the choice of the reference spectrum while relative differences originate from the numerical approach for solving the DOAS equation as well as the treatment of the slit function. Furthermore, differences in the implementation of the intensity offset correction were found to produce disagreements for measurements close to sunrise (8-10% for NO2, 80% for rms residual). The largest effect of approximate to 8% difference in NO2 was found to arise from the reference treatment; in particular for fits using a sequential reference. In terms of rms fit residual, the reference treatment has only a minor impact. In contrast, the wavelength calibration as well as the intensity offset correction were found to have the largest impact (up to 80 %) on rms residual while having only a minor impact on retrieved NO2 slant columns.

To Access Resource:

Questions? Email Resource Support Contact:

  • opensky@ucar.edu
    UCAR/NCAR - Library

Resource Type publication
Temporal Range Begin N/A
Temporal Range End N/A
Temporal Resolution N/A
Bounding Box North Lat N/A
Bounding Box South Lat N/A
Bounding Box West Long N/A
Bounding Box East Long N/A
Spatial Representation N/A
Spatial Resolution N/A
Related Links N/A
Additional Information N/A
Resource Format PDF
Standardized Resource Format PDF
Asset Size N/A
Legal Constraints

Copyright Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 License.
Access Constraints None
Software Implementation Language N/A

Resource Support Name N/A
Resource Support Email opensky@ucar.edu
Resource Support Organization UCAR/NCAR - Library
Distributor N/A
Metadata Contact Name N/A
Metadata Contact Email opensky@ucar.edu
Metadata Contact Organization UCAR/NCAR - Library

Author Peters, E.
Pinardi, G.
Seyler, A.
Richter, A.
Wittrock, F.
Bösch, T.
Van Roozendael, M.
Hendrick, F.
Drosoglou, T.
Bais, A. F.
Kanaya, Y.
Zhao, X.
Strong, K.
Lampel, J.
Volkamer, R.
Koenig, T.
Ortega, Ivan
Puentedura, O.
Navarro-Comas, M.
Gómez, L.
Yela González, M.
Piters, A.
Remmers, J.
Wang, Y.
Wagner, T.
Wang, S.
Saiz-Lopez, A.
García-Nieto, D.
Cuevas, C. A.
Benavent, N.
Querel, R.
Johnston, P.
Postylyakov, O.
Borovski, A.
Elokhov, A.
Bruchkouski, I.
Liu, H.
Liu, C.
Hong, Q.
Rivera, C.
Grutter, M.
Stremme, W.
Khokhar, M. F.
Khayyam, J.
Burrows, J. P.
Publisher UCAR/NCAR - Library
Publication Date 2017-03-10T00:00:00
Digital Object Identifier (DOI) Not Assigned
Alternate Identifier N/A
Resource Version N/A
Topic Category geoscientificInformation
Progress N/A
Metadata Date 2025-07-11T19:50:42.750313
Metadata Record Identifier edu.ucar.opensky::articles:19642
Metadata Language eng; USA
Suggested Citation Peters, E., Pinardi, G., Seyler, A., Richter, A., Wittrock, F., Bösch, T., Van Roozendael, M., Hendrick, F., Drosoglou, T., Bais, A. F., Kanaya, Y., Zhao, X., Strong, K., Lampel, J., Volkamer, R., Koenig, T., Ortega, Ivan, Puentedura, O., Navarro-Comas, M., Gómez, L., Yela González, M., Piters, A., Remmers, J., Wang, Y., Wagner, T., Wang, S., Saiz-Lopez, A., García-Nieto, D., Cuevas, C. A., Benavent, N., Querel, R., Johnston, P., Postylyakov, O., Borovski, A., Elokhov, A., Bruchkouski, I., Liu, H., Liu, C., Hong, Q., Rivera, C., Grutter, M., Stremme, W., Khokhar, M. F., Khayyam, J., Burrows, J. P.. (2017). Investigating differences in DOAS retrieval codes using MAD-CAT campaign data. UCAR/NCAR - Library. https://n2t.org/ark:/85065/d70p11tk. Accessed 01 August 2025.

Harvest Source