Development of measurements of chemically active traces in the lower troposphere at the stations of the A.M. Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences

In the city of Kislovodsk and at the Zvenigorod Scientific Station (ZSS) of the A.M. Obukhov IAP RAS, measurements of the spectra of scattered solar radiation are carried out during the daytime using the MAX-DOAS (Multi-AXis Differential Optical Absorption Spectroscopy) method in the visible spectral range (410 – 490 nm). The spectra are recorded at several different elevation angles: 1°, 2°, 3°, 5°, 10°, 20°, 30°, 40° and 90° (zenith direction). Such observation geometry makes it possible to retrieve the vertical profile of atmospheric traces in the lower troposphere.

At the A.M. Obukhov IAP, an algorithm for retrieval of the NO2 profile based on MAX-DOAS measurement data using Bayesian estimation was implemented at the Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences. Another approach to retrieval, free from the known shortcomings of the Bayesian approach, was also developed. The new approach consists in narrowing the class of possible profiles based on the assumption about the number of possible extremes in the reconstructed NO2 profile. 

Both algorithms use the radiative transfer model to calculate air mass coefficients, which significantly depend on the optical characteristics of aerosol, the presence of clouds, and the albedo of the underlying surface. The lack of information on these parameters makes a large contribution to the uncertainty of the VR reconstruction results. To test the new algorithms on measurement data in Kislovodsk and at the Zvenigorod Scientific Station, days with favorable meteorological conditions were selected. The report presents the results of NO2 profile retrieval for the selected days.

The work was carried out at the expense of state assignment of the A.M. Obukhov Institute of Physics of the Russian Academy of Sciences, topic registration number 125020501413-6.