References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-6-4477-2006

Analysis of the frequency-dependent response to wave forcing in the extratropics

Haklander

A. J.

¹ ² Siegmund

P. C.

² Kelder

H. M.

¹ ²

Eindhoven University of Technology (TUE), Department of Applied Physics, P.O. Box 513, 5600 MB Eindhoven, The Netherlands

Royal Netherlands Meteorological Institute (KNMI), Climate Research and Seismology Department, Atmospheric Composition Division, P.O. Box 201, 3730 AE De Bilt, The Netherlands

05 10 2006

6 12 4477 4481

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A quasigeostrophic model for the frequency-dependent response of the zonal-mean flow to planetary-wave forcing at Northern Hemisphere (NH) midlatitudes is applied to 4-D-Var ECMWF analysis data for six extended winter seasons. The theoretical response is a non-linear function of the frequency of the forcing, the thermal damping time α<sup>−1</sup>, and a scaling parameter µ which includes the aspect ratio of the meridional to the vertical length scale of the response. Regression of the calculated response from the analyses onto the theoretical response yields height-dependent estimates for both α<sup>−1</sup> and µ. The thermal damping time estimated from this dynamical model is about 2 days in the troposphere, 7–10 days in the stratosphere, and 2–4 days in the lower mesosphere. For the stratosphere and lower mesosphere, the estimates lie within the range of existing radiative damping time estimates, but for the troposphere they are significantly smaller.

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