A stratospheric intrusion at the subtropical jet over the Mediterranean Sea: air-borne remote sensing observations and model results 1Institute of Energy and Climate Research (IEK-7), Forschungszentrum Jülich, 52425 Jülich, Germany
20 Sep 2012
2Department of Meteorology, Stockholm University, 10691 Stockholm, Sweden
3Department of Physics, University of Wuppertal, 42907 Wuppertal, Germany
*now at: Institute of Environmental Physics (IUP), University of Bremen, 28359 Bremen, Germany
**now at: Juelich Supercomputing Centre (JSC), Forschungszentrum Jülich, 52425 Jülich, Germany
Received: 02 February 2012 – Published in Atmos. Chem. Phys. Discuss.: 20 March 2012 Abstract. Remote sensing measurements from the Cryogenic Infrared Spectrometers and
Telescope for the Atmosphere – New Frontiers (CRISTA-NF) during a flight on
29 July 2006 are presented. This flight is part of the AMMA-SCOUT-O3
measurement campaign, where CRISTA-NF was deployed on the high-flying
research aircraft M55-Geophysica. The flight path was located over Italy and
the Mediterranean Sea and crossed over the subtropical jet twice.
Measurements of temperature, and the volume mixing ratios of water vapor
(H2O), ozone (O3), nitric acid (HNO3) and
peroxyacetyl nitrate (PAN) are available with a vertical resolution of
up to 500 m between about 6 to 21 km altitude. CRISTA-NF observes these
trace gases simultaneously and provides a quasi-2-D view of the transition
region between the troposphere and the stratosphere. The observation of these
different trace gases allows to determine tropospheric and stratospheric air masses.
As expected, higher abundances are found where
the main source of the trace gases is located: in the stratosphere for
O3 and in the troposphere for H2O and PAN. Tracer-tracer
correlations between O3 and PAN are used to identify the mixed
tropospheric and lowermost stratospheric air at the subtropical jet and
around the thermal tropopause north of the jet. An intrusion of stratospheric
air into the troposphere associated with the subtropical jet is found in the
CRISTA-NF observations. The observations indicate that the intrusion is
connected to a tropopause fold which is not resolved in the ECMWF analysis
data. The intrusion was reproduced in a simulation with the Chemical
Lagrangian Model of the Stratosphere (CLaMS). The CLaMS simulation shows,
that the lowermost stratospheric air masses in the intrusion where transported along the the subtropical jet.
The tropospheric air masses around the intrusion originate from the vicinity of the Asian monsoon anticyclone.
This work discusses the nature
of the observed processes at the subtropical jet based on the CRISTA-NF
observations and the CLaMS simulation.
Revised: 24 August 2012 – Accepted: 30 August 2012 – Published: 20 September 2012
Citation: Weigel, K., Hoffmann, L., Günther, G., Khosrawi, F., Olschewski, F., Preusse, P., Spang, R., Stroh, F., and Riese, M.: A stratospheric intrusion at the subtropical jet over the Mediterranean Sea: air-borne remote sensing observations and model results, Atmos. Chem. Phys., 12, 8423-8438, doi:10.5194/acp-12-8423-2012, 2012.