ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-3-1589-2003 The impact of monsoon outflow from India and Southeast Asia in the upper troposphere over the eastern Mediterranean Scheeren H. A. 1 2 Lelieveld J. 2 Roelofs G. J. 1 Williams J. 2 Fischer H. 2 de Reus M. 2 de Gouw J. A. 1 3 Warneke C. 1 3 Holzinger R. 2 Schlager H. 4 Klüpfel T. 2 Bolder M. 1 van der Veen C. 1 Lawrence M. 2 Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, The Netherlands Max Planck Institute for Chemistry, Mainz, Germany now at NOAA Aeronomy Laboratory, Boulder, Colorado, USA Institute for Atmospheric Physics, DLR, Oberpfaffenhofen, Germany 01 10 2003 3 5 1589 1608 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/3/1589/2003/acp-3-1589-2003.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/3/1589/2003/acp-3-1589-2003.pdf

A major objective of the Mediterranean INtensive Oxidant Study (MINOS) was to investigate long-range transport of pollutants (notably ozone precursor species). Here we present trace gas measurements from the DLR (German Aerospace Organization) Falcon aircraft in the eastern Mediterranean troposphere. Ten day backward trajectories and a coupled chemistry-climate model (ECHAM4) were used to study the nature and origin of pollution observed in the upper troposphere between 6 and 13 km altitude. We focus on a large pollution plume encountered over the eastern Mediterranean between 1 and 12 August originating in South Asia (India and Southeast Asia), referred to as the Asian plume, associated with the Asian Summer Monsoon. Vertical as well as longitudinal gradients of methane, carbon monoxide, hydrocarbons including acetone, methanol, and acetonitrile, halocarbons, ozone and total reactive nitrogen (NO<sub>y</sub>) are presented, showing the chemical impact of the Asian plume compared to westerly air masses containing pollution from North America. The Asian plume is characterized by enhanced concentrations of biomass burning tracers (acetylene, methyl chloride, acetonitrile), notably from biofuel use. Concentrations of the new automobile cooling agent HFC-134a were significantly lower in the Asian plume than in air masses from North America. Relatively high levels of ozone precursors (CO, hydrocarbons) were found in both air masses, whereas lower ozone concentrations in the Asian plume suggest NO<sub>x</sub>-limited conditions. Consistently, ECHAM model simulations indicate that the expected future increase of NO<sub>x</sub>-emissions in Asia enhances the photochemical ozone production in the Asian plume. The size and location of the Asian plume near the tropopause provides an important potential for pollution transport into the lowermost stratosphere. We present observations indicative of Asian pollution transport into the lower stratosphere.