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Volume 15, issue 22
Atmos. Chem. Phys., 15, 13145-13159, 2015
https://doi.org/10.5194/acp-15-13145-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 15, 13145-13159, 2015
https://doi.org/10.5194/acp-15-13145-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 27 Nov 2015

Research article | 27 Nov 2015

A potential vorticity-based determination of the transport barrier in the Asian summer monsoon anticyclone

F. Ploeger, C. Gottschling, S. Griessbach, J.-U. Grooß, G. Guenther, P. Konopka, R. Müller, M. Riese, F. Stroh, M. Tao, J. Ungermann, B. Vogel, and M. von Hobe F. Ploeger et al.
  • Institute for Energy and Climate research: Stratosphere (IEK–7), Forschungszentrum Jülich, Jülich, Germany

Abstract. The Asian summer monsoon provides an important pathway of tropospheric source gases and pollution into the lower stratosphere. This transport is characterized by deep convection and steady upwelling, combined with confinement inside a large-scale anticyclonic circulation in the upper troposphere and lower stratosphere (UTLS). In this paper, we show that a barrier to horizontal transport along the 380 K isentrope in the monsoon anticyclone can be determined from a local maximum in the gradient of potential vorticity (PV), following methods developed for the polar vortex (e.g., Nash et al., 1996). The monsoon anticyclone is dynamically highly variable and the maximum in the PV gradient is weak, such that additional constraints are needed (e.g., time averaging). Nevertheless, PV contours in the monsoon anticyclone agree well with contours of trace gas mixing ratios (CO, O3) and mean age from model simulations with a Lagrangian chemistry transport model (CLaMS) and satellite observations from the Microwave Limb Sounder (MLS) instrument. Hence, the PV-based transport barrier reflects the separation between air inside the core of the anticyclone and the background atmosphere well. For the summer season 2011 we find an average PV value of 3.6 PVU for the transport barrier in the anticyclone on the 380 K isentrope.

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The Asian summer monsoon provides an important pathway of tropospheric source gases and pollution into the lower stratosphere. This transport is characterized by deep convection and steady upwelling, combined with confinement inside a large-scale anticyclonic circulation in the upper troposphere and lower stratosphere. In this paper, we show that a barrier to horizontal transport in the monsoon can be determined from a local maximum in the gradient of potential vorticity.
The Asian summer monsoon provides an important pathway of tropospheric source gases and...
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