Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 3 2 2003 10.5194/acpd-3-2101-2003 http://www.atmos-chem-phys-discuss.net/3/2101/2003/ http://www.atmos-chem-phys-discuss.net/3/2101/2003/acpd-3-2101-2003.html http://www.atmos-chem-phys-discuss.net/3/2101/2003/acpd-3-2101-2003.pdf 2101 2141 2003-04-16 Rapid intercontinental air pollution transport associated with a meteorological bomb A. Stohl H. Huntrieser A. Richter S. Beirle O. Cooper S. Eckhardt C. Forster P. James N. James M. Wenig T. Wagner J. Burrows U. Platt Department of Ecology, Technical University of Munich, Germany Institute for Atmospheric Physics, DLR, Oberpfaffenhofen, Germany Institute of Environmental Physics, University of Bremen, Germany Institute of Environmental Physics, Heidelberg University, Germany Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado/NOAA Aeronomy Laboratory, Boulder, USA NASA Goddard Space Flight Center, Code 916, Greenbelt, MD, USA Intercontinental transport (ICT) of trace substances normally occurs on timescales ranging from a few days to several weeks. In this paper an extraordinary episode in November 2001 is presented, where pollution transport across the North Atlantic took only about one day. The transport mechanism, termed here an intercontinental pollution express highway, was exceptional, as it involved an explosively generated cyclone, a so-called meteorological "bomb". To the authors' knowledge, this is the first study describing pollution transport in a bomb. The discovery of this event was based on transport model calculations and satellite measurements of NO₂, a species with a relatively short lifetime in the atmosphere, which could be transported that far only because of the high wind speeds produced by the bomb. A 15-year transport climatology shows that intercontinental express highways are about four times more frequent in winter than in summer, in agreement with bomb climatologies. The climatology furthermore reveals that intercontinental express highways may be important for the budget of short-lived substances in the remote troposphere. For instance, for a substance with a lifetime of 1 day, express highways may be responsible for about two thirds of the total ICT. A rough calculation suggests that express highways connecting North America with Europe enhance the average NO_x mixing ratios over Europe, due to North American emissions, by about 2–3 pptv in winter.