Integrated airborne investigation of the air composition over the Russian sector of the Arctic

Abstract

Abstract. The change of the global climate is most pronounced in the Arctic, where the air temperature increases 2 to 3 times faster than the global average. This process is associated with an increase in the concentration of greenhouse gases in the atmosphere. There are publications predicting the sharp increase in methane emissions into the atmosphere due to permafrost thawing. Therefore, it is important to study how the air composition in the Arctic changes in the changing climate. In the Russian sector of the Arctic, the air composition was measured only in the surface atmospheric layer at the coastal stations or earlier at the drifting stations. Vertical distributions of gas constituents of the atmosphere and aerosol were determined only in a few small regions. That is why the integrated experiment was carried out to measure the composition of the troposphere in the entire Russian sector of the Arctic from on board the Optik Tu-134 aircraft laboratory in the period of ​​​​​​​4 to 17 September of 2020. The aircraft laboratory was equipped with contact and remote measurement facilities. The contact facilities were capable of measuring the concentrations of CO2, CH4, O3, CO, NOx​​​​​​​, and SO2, as well as the disperse composition of particles in the size range from 3 nm to 32 µm, black carbon, and organic and inorganic components of atmospheric aerosol. The remote facilities were operated to measure the water transparency in the upper layer of the ocean, the chlorophyll content in water, and spectral characteristics of the underlying surface. The measured data have shown that the ocean continues absorbing CO2. This process is most intense over the Barents and Kara seas. The recorded methane concentration was increased over all the Arctic seas, reaching 2090 ppb in the near-water layer over the Kara Sea. The contents of other gas components and black carbon were close to the background level. In bioaerosol, bacteria predominated among the identified microorganisms. In most samples, they were represented by coccal forms, less often spore-forming and non-spore-bearing rod-shaped bacteria. No dependence of the representation of various bacterial genera on the height and the sampling site was revealed. The most turbid during the experiment was the upper layer of the Chukchi and Bering seas. The Barents Sea turned out to be the most transparent. The differences in extinction varied by more than a factor of 1.5. In all measurements, except for the Barents Sea, the tendency of an increase in chlorophyll fluorescence in more transparent waters was observed.

Calculation of the remote sensing reflectance based on the total upwelling radiance measured from the Optik Tu-134 aircraft laboratory

“…The field data were obtained during an under-aircraft experiment performed during the 1st stage of the 89th cruise of the R/V 'Akademik Mstislav Keldysh' (AMK) on September 10, 2022 in the southwestern part of the Kara Sea. The total upwelling radiance spectra Lt(λ) were obtained using a PSR-1100f spectroradiometer with a spectral range of 320-1100 nm and a spectral resolution of <3 nm, installed on board the Tu-134 "Optik" laboratory aircraft 3 . The spectra were recorded when the receiver was set to nadir, the angle of the field of view of the receiver lens was 4°, the recording was carried out once every 15 seconds, which, at an aircraft speed of about 120 m/s, corresponds to a spatial data resolution of 1.8 km.…”

Characterization of suspended particulate matter in the South Kara Sea (Arctic Ocean) in September 2022 as part of the climate experiment

“…1a. Methodology of airborne investigations by lidar is given in Belan et al 21 The flying laboratory made direct passes over the vessel at an altitude of ~90-200 m above the sea surface on September 9 and 10, 2022. The duration of these sections is 10-15 minutes, and the length is 70-100 km at aircraft speed of ~120 m/s.…”

Separate retrieval of microphysical parameters in aerosol fraction from the lidar data

“…Vertical profiles of aerosol parameters can be measured by various instruments from the aircraft laboratory [15][16][17][18], which is probably the most effective source of contact measurements. Their alternative is remote sensing systems.…”