Atmos. Chem. Phys. Discuss., 6, 9259-9271, 2006
www.atmos-chem-phys-discuss.net/6/9259/2006/
doi:10.5194/acpd-6-9259-2006
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Differences between the QBO in the first and in the second half of the ERA-40 reanalysis
H. J. Punge1,2 and M. A. Giorgetta1
1Max Planck Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, Germany
2IMPRS on Earth System Modelling, Bundesstr. 53, 20146 Hamburg, Germany

Abstract. The representation of the quasi-biennial oscillation (QBO) is investigated in the ERA-40 reanalysis. In the lower stratosphere, where there is a good number of observations, the representation of the QBO is equally well throughout the record. However, strong differences between the first and the second half of the zonal wind data set are found in the upper stratosphere, with a typical offset of −10 m/s in the equatorial zonal wind in the earlier part versus the later part of the ERA-40 data set. The strength of the QBO is also affected. Possible explanations are discussed. The identified change of the assimilated wind profiles over time in ERA-40 requires a careful use of equatorial upper stratospheric winds from the reanalysis for validation purposes.

Citation: Punge, H. J. and Giorgetta, M. A.: Differences between the QBO in the first and in the second half of the ERA-40 reanalysis, Atmos. Chem. Phys. Discuss., 6, 9259-9271, doi:10.5194/acpd-6-9259-2006, 2006.
 
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