The impact of monsoon outflow from South-East Asia in the upper
troposphere over the eastern Mediterranean
Bert Scheeren1,2, Horst Fischer2, Marian de Reus2,
Joost de Gouw3, Carsten Warneke3, Rupert Holzinger2,
Jonathan Williams2, Hans Schlager4, Thomas Klüpfel2,
Michel Bolder1, Carina van der Veen1, Geert-Jan Roelofs1,
Marc Lawrence2 and Jos Lelieveld2
1Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht
University, the Netherlands (h.a.Scheeren@phys.uu.nl)
2Max Planck Institute for Chemistry, Mainz, Germany
3NOAA Aeronomy Laboratory, Boulder, Colorado, USA
4Institute for Atmospheric Physics, DLR, Oberpfaffenhofen, Germany
During August 2001 a total of 14 measurement flights were conducted with the Falcon
jet aircraft from the DLR (German Aerospace Organization) over the eastern and middle
Mediterranean as part of the MINOS (Mediterranean INtensive Oxidant Study) campaign.
The flights extended from the boundary layer up to about 13 km in the upper troposphere.
A major objective of MINOS was to investigate the role of long-range transport of
pollutants (notably ozone precursor species) into the region. In this study we focus
on a large scale upper tropospheric plume, which was encountered by the aircraft at an
altitude of 10 km and up over the eastern Mediterranean between August 1 and 8 (flight
1 to 3). We show profiles of methane, carbon monoxide, hydrocarbons, halocarbons, ozone
and NOy. The measurements point to a moderately aged plume with a tropical signature and
exclude a role for recent local deep convection. Relatively low ozone concentrations
suggest NOx-limited conditions in the plume. Ten-day back-trajectories lead to South-East
Asia (notably India) as the source region. Enhanced biomass burning tracers (methyl chloride,
acetonitrile) point to a strong biomass burning component, most likely related to the
extensive use of biofuels in Asia. Moreover, these results are consistent with measurements
performed over the Indian ocean during the INDOEX (INDian Ocean Experiment) 1999 campaign.
The occurrence of an Asian plume over the eastern Mediterranean appears to be the result of
deep convection over the polluted Bay of Bengal region during the Indian Summer monsoon.
Then, a strong easterly flow driven by the upper tropospheric anti-cyclone over the Tibetan
Plateau during Summer, transports these air masses towards northern Africa and the Mediterranean. We show that the Asian plume is well simulated by different chemistry-transport models (ECHAM-4 and MATCH).