The influence of the stratosphere on the tropospheric zonal wind response to CO2 doubling 1Institute for Marine and Atmospheric research Utrecht, Utrecht University, The Netherlands
26 May 2011
2Department of Meteorology, University of Reading, UK
3Royal Netherlands Meteorological Institute – KNMI, De Bilt, The Netherlands
*current address: Meteo Consult bv, P.O. Box 617, 6700 AP Wageningen, The Netherlands
†deceased, June 2010
Received: 11 August 2010 – Published in Atmos. Chem. Phys. Discuss.: 12 October 2010 Abstract. The influence of a CO2 doubling on the stratospheric potential vorticity
(PV) is examined in two climate models. Subsequently, the influence of
changes in the stratosphere on the tropospheric zonal wind response is
investigated, by inverting the stratospheric PV.
Revised: 05 May 2011 – Accepted: 16 May 2011 – Published: 26 May 2011
Radiative effects seem to dominate the stratospheric response to CO2
doubling in the Southern Hemisphere. These lead to a stratospheric PV
increase at the edge of the polar vortex, resulting in an increased westerly
influence of the stratosphere on the troposphere, increasing the midlatitude
tropospheric westerlies in late winter.
In the Northern Hemisphere, dynamical effects are also important. Both models
show a reduced polar PV and an enhanced midlatitude PV in the Northern
Hemisphere winter stratosphere. These PV changes are likely related to an
enhanced wave forcing of the winter stratosphere, as measured by an increase
in the 100 hPa eddy heat flux, and result in a reduced westerly influence of
the stratosphere on the high latitude tropospheric winds. In one model, the
high latitude PV decreases are, however, restricted to higher altitudes, and
the tropospheric response due to the stratospheric changes is dominated by an
increased westerly influence in the midlatitudes, related to the increase in
midlatitude PV in the lower stratosphere.
The tropospheric response in zonal wind due to the stratospheric PV changes
is of the order of 0.5 to 1 m s−1. The total tropospheric response has
a somewhat different spatial structure, but is of similar magnitude. This
indicates that the stratospheric influence is of importance in modifying the
tropospheric zonal wind response to CO2 doubling.
Citation: Hinssen, Y. B. L., Bell, C. J., and Siegmund, P. C.: The influence of the stratosphere on the tropospheric zonal wind response to CO2 doubling, Atmos. Chem. Phys., 11, 4915-4927, doi:10.5194/acp-11-4915-2011, 2011.