Air pollution from Europe clearly visible in ICOS measurements across Sweden
It was reported (SVT) on Sunday and Monday about very bad air quality in Stockholm. On Sunday, the air pollution at some spots was worse than in Beijing, a city well known for its polluted air.

The increase was first thought to be due to winter tires, dirty roads and breaks, but measurements showed that there was a body of polluted air from Europe that was the main reason. This is clearly visible at the ICOS measurement sites as well, not only around Stockholm but from south to north. The peaks on carbon monoxide (CO) at the ICOS Sweden three stations Hyltemossa (SE-Htm, northern Scania), Norunda (SE-Nor, Uppland) and Svartberget (SE-Svb, Västerbotten County) are clearly connected to wind direction and origin of the air masses as the analysis of backward trajectories shows. Longer period with air masses from the south at Hyltemossa led to a longer period with high concentration of CO (28-29 January) in the south compared to more northerly regions. There, only short periods of southerly winds led to sharp peaks.

CO concentrations 21-31 January 2017 Carbon monoxide (CO) concentration measured at ICOS Sweden stations from 21 to 31 January 2017, at 100 m height. Click to enlarge.