Deep convective injection of boundary layer air into the lowermost
stratosphere at mid-latitudes
Horst Fischer1, Marian de Reus1, Joost de Gouw2,
Carsten Warneke2,Hans Schlager3, and Andreas Minikin3
1Max Planck Institute for Chemistry, Mainz, Germany (hofi@mpch-mainz.mpg.de)
2NOAA Aeronomy Laboratory, Boulder, Colorado, USA
3Institute for Atmospheric Physics, DLR, Oberpfaffenhofen, Germany
On August 22, 2001 a MINOS measurement flight was performed during the transfer of
the German research aircraft FALCON from Sardinia to Crete. Cruising at 8.2 km, the
plane was forced to climb to 11.2 km over the southern tip of Italy to stay clear of
the anvil of a large cumulonimbus tower. During ascend into the lowermost stratosphere
in-situ measurements onboard the FALCON indicated several sharp increases of the
concentrations of tropospheric trace gases, e.g CO, acetone, methanol and acetonitrile,
above the anvil. During one particular event deep in the stratosphere, at O3
concentrations exceeding 200 ppbv, CO increased from 58 ppbv to 79 ppbv, while the
concentration of acetone and methanol doubled (722 pptv to 1384 pptv for acetone;
382 pptv to 984 pptv for methanol). Scatter plots of CO, acetone or methanol versus
O3 indicate that polluted boundary layer air was, most probably, mixed deep into the
lowermost stratosphere. Close to the tropopause the convective injection of boundary
layer air was associated with new particle formation due to gas-to-particle conversion.
Well above the tropopause convectively driven particle formation was not observed,
indicating an efficient washout or freeze-out of gaseous precursors, in particular
water vapour.
To our best knowledge, this is the first in-situ observation of troposphere-stratosphere
exchange associated with deep convection at mid-latitudes that reached deep into the
lowermost stratosphere, well above the local tropopause.