Characteristics of the large-scale circulation during episodes with high and low concentrations of carbon dioxide and air pollutants at an arctic monitoring site in winter

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The impact of large-scale atmospheric flow systems on the time variation of atmospheric carbon dioxide and aerosols at an Arctic monitoring site has been studied for winter seasons. Episodes with high and low concentrations of atmospheric carbon dioxide and aerosols were identified. Synoptic 500 hPa geopotential height maps and sea-level pressure maps were used to study the large-scale circulation. We found that polluted air, that is elevated in aerosol concentrations and carbon dioxide, arrived from northwestern Russia, whereas nonpolluted air and air with low concentrations of carbon dioxide arrived from the Norwegian Sea during winter. Part of the study was devoted to an investigation of the impact of atmospheric blocking and planetary-scale waves on episodes with high and low concentrations of atmospheric carbon dioxide and aerosols at the monitoring site. Unlike other similar studies we found that atmospheric blockings do not have a large impact on these episodes, unless the blocking is located east of 40°E. Such blockings are not as frequent as those over eastern Atlantic and western Europe. However, they are prerequisites for episodes with high concentrations of atmospheric carbon dioxide and air pollutants. We also found that the planetary-scale waves do not contribute much to episodes with high concentrations of carbon dioxide and air pollutants. The result obtained in the first part of the study, viz. that polluted air and air with high concentrations of atmospheric carbon dioxide arrive from northwestern Russia, whereas nonpolluted air and air with low concentrations of carbon dioxide arrive from the Norwegian Sea, was tested by using different data (particulate sulfur in the air) and using a different method of identifying episodes with high and low concentrations. The test showed that the results were essentially the same. We conclude that the wind direction in the lower troposphere is the parameter that has the largest impact on concentrations of atmospheric carbon dioxide and air pollutants at Spitsbergen in winter.