Polar lows (PLs) are intense mesoscale maritime cyclones. They produce hazardous winds in the Arctic, but their mesoscale structure is difficult to represent in atmospheric reanalyses. We evaluate the second-generation Copernicus Arctic Regional Reanalysis (CARRA2) for ten well-documented polar lows from 2002–2024 in the Nordic Seas, Barents Sea, Denmark Strait and Pacific Arctic. Reference events were compiled from published case studies and satellite imagery. PLs were tracked using 850-hPa vorticity in three-hourly 2.5-km analyses, and equivalent neutral 10-m winds were compared with QuikSCAT and ASCAT scatterometer observations at common valid locations. Retained tracks matched nine of the ten events, with mean position errors of 15.8–104.6 km (unweighted mean 55.1 km). The unmatched event of 7 March 2005 showed enhanced native-grid vorticity that spatial smoothing and persistence criteria removed. Across 59 scatterometer overpasses from nine events, median wind speeds were highly correlated (correlation 0.960) but 1.25 m s^-1 lower in CARRA2 on average. The difference rose to 2.18 m s^-1 for the 95th percentile and exceeded 8 m s^-1 in individual intense states. Scatterometer area fractions above 15 and 20 m s^-1 exceeded CARRA2 by 10.14 and 6.08 percentage points, respectively. CARRA2 therefore represents most selected polar lows and their typical wind variability, but its strong winds and their extent are lower than scatterometer estimates.

This paper presents the results of a comparison of the seasonal dynamics of carbon dioxide content in the atmosphere and the phenological phases of various water bodies located in the boreal and subarctic zones for 2012–2020. Six large freshwater areas were selected as research objects: Lake Baikal, Lake Ladoga, Gulf of Ob, Lake Huron, Great Bear Lake and Great Slave Lake. In addition, four areas of wetlands in Western Siberia were studied. The CO2 concentration in the air column over water bodies was obtained from CAMS global greenhouse gas reanalysis data. These data represent three-dimensional fields of aerosols and chemical components in the atmosphere, with complete coverage of the globe. The phenological phases of the water bodies were determined using data from the MIRAS microwave radiometer of the SMOS satellite. The comparison and analysis performed showed that the concentration of CO2 in the atmosphere over the studied water bodies has a seasonal cyclical nature. The minimum concentration corresponds to the summer period due to strong photosynthesis of phytoplankton and swamp vegetation, which results in the absorption of carbon dioxide. The maximum CO2 concentration over the water bodies corresponds to the end of the winter – the beginning of the spring period, when photosynthesis processes are minimal. During this period, CO2 is being accumulated in water bodies and subsequently emitted. In freezing lakes located in the boreal zone, in addition to a stable spring maximum of CO2, a strong short-term release of carbon dioxide is sometimes observed, also corresponding to the stage of destruction of the ice cover. It is associated with the release of CO2 accumulated over the winter period, which was “sealed” in the ice and in the water column under the ice. The absence of such a release in the waters of the subarctic zone is explained by the lower biological productivity of these reservoirs compared to the waters of the boreal zone.