Stratospheric ozone in boreal fire plumes – the 2013 smoke season over central Europe

摘要

In July 2013 very strong boreal fire plumes were observed at the northern rimof the Alps by lidar and ceilometer measurements of aerosol, ozone and watervapour for about 3 weeks. In addition, some of the lower-troposphericcomponents of these layers were analysed at the Global Atmosphere Watchlaboratory at the Schneefernerhaus high-altitude research station(2650 m a.s.l., located a few hundred metres south-west of the Zugspitzesummit). The high amount of particles confirms our hypothesis that fires inthe Arctic regions of North America lead to much stronger signatures in thecentral European atmosphere than the multitude of fires in the USA.This has been ascribed to the prevailing anticyclonic advection patternduring favourable periods and subsidence, in contrast to warm-conveyor-beltexport, rainout and dilution frequently found for lower latitudes. A highnumber of the pronounced aerosol structures were positively correlated withelevated ozone. Chemical ozone formation in boreal fire plumes is known to berather limited. Indeed, these air masses could be attributed to stratosphericair intrusions descending from remote high-latitude regions, obviouslypicking up the aerosol on their way across Canada. In one case, subsidencefrom the stratosphere over Siberia over as many as 15–20 days withoutincrease in humidity was observed although a significant amount of Canadiansmoke was trapped. These coherent air streams lead to rather straight andrapid transport of the particles to Europe.