Abstract
Since 2004, we have carried out yearly measurements of physicochemical aerosol characteristics onboard research vessels at Southern Hemisphere high latitudes (34–72° S; 45° W–110° E). In this work, we statistically generalize the results from multiyear (2004–2021) measurements in this area of the aerosol optical depth (AOD) of the atmosphere, concentrations of aerosol and equivalent black carbon (EBC), as well as the ionic composition of aerosol. A common regularity was that the aerosol characteristics decreased with increasing latitude up to the Antarctic coast, where the aerosol content corresponded to the global background level. Between Africa and Antarctica, AOD decreased from 0.07 to 0.024, the particle volume decreased from 5.5 to 0.55 µm3/cm3, EBC decreased from 68.1 to 17.4 ng/m3, and the summed ion concentration decreased from 24.5 to 2.5 µg/m3. Against the background of the common tendency of the latitude decrease in aerosol characteristics, we discerned a secondary maximum (AOD and ion concentrations) or a plateau (aerosol and EBC concentrations). The obtained spatial distribution of aerosol characteristics qualitatively agreed with the model-based MERRA-2 reanalysis data, but showed quantitative differences: the model AOD values were overestimated (by 0.015, on average); while the EBC concentrations were underestimated (by 21.7 ng/m3). An interesting feature was found in the aerosol spatial distribution in the region of Antarctic islands: at a distance of 300 km from the islands, the concentrations of EBC decreased on average by 29%, while the aerosol content increased by a factor of 2.5.
Highlights
Atmospheric aerosol plays an important role in the processes of radiative transfers and mass exchange of different substances in the “continent–atmosphere–ocean” system.Because of the variety of aerosol physicochemical compositions, interaction processes, and strong variations, there is still uncertainty regarding aerosol’s quantitative characteristics in a number of regions
We note that the aerosol content in the atmosphere of the Antarctic bordering the Southern Ocean is considered as the global background level
The aerosol content in the atmosphere over the ocean is determined by two sources: (a) the generation of marine aerosol, which depends primarily on the wind velocity (e.g., [47,48]), and (b) the outflows of continental aerosol of different types
Summary
Atmospheric aerosol plays an important role in the processes of radiative transfers and mass exchange of different substances in the “continent–atmosphere–ocean” system. Because of the variety of aerosol physicochemical compositions, interaction processes, and strong variations, there is still uncertainty regarding aerosol’s quantitative characteristics in a number of regions These are the high-latitude regions of the ocean, where regular measurements are barely possible (except at scarce island stations). International Polar Year, associated with climate change, stimulated more active research into aerosol physicochemical characteristics in high-latitude regions, namely the disperse, ion, and elemental compositions of aerosol, the content of the absorbing substance (black carbon) in aerosol, the aerosol optical depth (AOD) of the atmosphere, etc. Taking into account the measurements from new expeditions (2018–2021), in this work we refine the specific features of the spatial distribution of atmospheric aerosol characteristics over the ocean in the latitude zone of 34–70◦ S. Atmosphere 2022, 13, 427 the procedure of identifying and sorting out bursts (contaminated measurements) in the of 21 initial observation time series was carried out through visual data control; i.e., it 3was partly subjective in character
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