Gravitational separation in the stratosphere – a new indicator of atmospheric circulation 1National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8569, Japan
03 Sep 2013
2Miyagi University of Education, Sendai 980-0845, Japan
3National Institute of Polar Research, Tokyo 190-8518, Japan
4Center for Atmospheric and Oceanic Studies, Tohoku University, Sendai 980-8578, Japan
5Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara 252-5210, Japan
Received: 30 December 2012 – Published in Atmos. Chem. Phys. Discuss.: 20 February 2013 Abstract. As a basic understanding of the dynamics of the atmospheric circulation, it
has been believed that gravitational separation of atmospheric components is
observable only in the atmosphere above the turbopause. However, we found,
from our high-precision measurements of not only the isotopic ratios of
N2, O2 and Ar but also the mole fraction of Ar, that gravitational
separation occurs even in the stratosphere below the turbopause; their
observed vertical profiles are in good agreement with those expected
theoretically from molecular mass differences. The O2/N2 ratio
observed in the middle stratosphere, corrected for gravitational separation,
showed the same mean air age as estimated from the CO2 mole fraction.
Simulations with a 2-dimensional model of the middle atmosphere indicated
that a relationship between gravitational separation and the age of air in
the stratosphere would be significantly affected if the Brewer–Dobson
circulation was enhanced due to global warming. Therefore, gravitational
separation is usable as a new indicator of changes in the atmospheric
circulation in the stratosphere.
Revised: 23 July 2013 – Accepted: 23 July 2013 – Published: 03 September 2013
Citation: Ishidoya, S., Sugawara, S., Morimoto, S., Aoki, S., Nakazawa, T., Honda, H., and Murayama, S.: Gravitational separation in the stratosphere – a new indicator of atmospheric circulation, Atmos. Chem. Phys., 13, 8787-8796, doi:10.5194/acp-13-8787-2013, 2013.