02.06.2014 : FB1-Seminar

11:00 h, Hörsaal, Düsternbrooker Weg 20

Abstract:

Blanca Ayarzagüena¹, Yvan J. Orsolini², Ulrike Langematz¹, Janna Abalichin¹ and Anne Kubin<sup>1

1</sup> Institut für Meteorologie, Freie Universität Berlin, Germany
² Norwegian Institute for Air Research, Kjeller, Norway

Blocking highs (BHs) have been previously shown to influence the wintertime polar stratospheric variability through the modulation of the climatological planetary waves (PWs) depending on the BH location. In particular, BHs over the Euro-Atlantic sector tend to enhance the upward propagation of PWs, and those over the western Pacific to reduce it. We examine future changes in the response of the wave activity to the BH location and their effects on the wintertime stratospheric variability in transient simulations of ECHAM/MESSy Atmospheric Chemistry (EMAC). After having verified that EMAC can reproduce qualitatively well the geographical dependence in the BH influence on PW injection, we show that this dependence does not change in the future. However, an eastward shift of the pattern of the BH influence on PW propagation and an intensification of the wavenumber-1 (WN1) component of the interaction between climatological and anomalous waves are detected. Changes in the upper tropospheric jet and an intensification of the WN1 climatological wave due to a strengthening of the Aleutian low explain these variations. The distribution of future BHs preceding extreme polar vortex events is also affected according to the changes detected in the wave activity pattern. Future BHs preceding strong polar vortex events tend to be more concentrated over the Pacific, where BHs interfere negatively with WN1 climatological waves. Future BHs prior to major stratospheric warmings are not located in the preferred regions for the enhancement of PWs as clearly as in the past, but they are predominantly located over an extended Euro-Atlantic sector.

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