Water vapor transport in the lower mesosphere of the subtropics: a trajectory analysis T. Flury1, S. C. Müller1,*, K. Hocke1, and N. Kämpfer1 1Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland *now at: METEOTEST, Fabrikstrasse 14, 3012 Bern, Switzerland
Abstract. The Institute of Applied Physics operates an airborne microwave radiometer
AMSOS that measures the rotational transition line of water vapor at 183.3 GHz.
Water vapor profiles are retrieved for the altitude range from 15 to 75 km
along the flight track. We report on a water vapor enhancement in the lower
mesosphere above India and the Arabian Sea. The measurements took place on our
flight from Switzerland to Australia and back in November 2005 conducted during
EC- project SCOUT-O3. We find an enhancement of up to 25% in the lower
mesospheric H2O volume mixing ratio measured on the return flight one
week after the outward flight. The origin of the air is traced back by means
of a trajectory model in the lower mesosphere and wind fields from ECMWF.
During the outward flight the air came from the Atlantic Ocean around 25 N
and 40 W. On the return flight the air came from northern India and Nepal
around 25 N and 90 E. Mesospheric H2O measurements from Aura/MLS confirm
the transport processes of H2O derived by trajectory analysis of the AMSOS
data. Thus the large variability of H2O VMR during our flight is explained
by a change of the winds in the lower mesosphere. This study shows that trajectory
analysis can be applied in the mesosphere and is a powerful tool to understand the
large variability in mesospheric H2O.
Citation: Flury, T., Müller, S. C., Hocke, K., and Kämpfer, N.: Water vapor transport in the lower mesosphere of the subtropics: a trajectory analysis, Atmos. Chem. Phys., 8, 7273-7280, doi:10.5194/acp-8-7273-2008, 2008.