Journal cover Journal topic
Annales Geophysicae An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 1.585 IF 1.585
  • IF 5-year value: 1.698 IF 5-year
    1.698
  • CiteScore value: 1.62 CiteScore
    1.62
  • SNIP value: 0.820 SNIP 0.820
  • IPP value: 1.52 IPP 1.52
  • SJR value: 0.781 SJR 0.781
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 83 Scimago H
    index 83
  • h5-index value: 24 h5-index 24
Volume 22, issue 8
Ann. Geophys., 22, 2693–2713, 2004
https://doi.org/10.5194/angeo-22-2693-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 2693–2713, 2004
https://doi.org/10.5194/angeo-22-2693-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  07 Sep 2004

07 Sep 2004

Sensitivity of the Freie Universität Berlin Climate Middle Atmosphere Model (FUB-CMAM) to different gravity-wave drag parameterisations

P. Mieth2,1, J. L. Grenfell2, U. Langematz2, and M. Kunze2 P. Mieth et al.
  • 1Deutsches Zentrum für Luft- und Raumfahrt, Institut für Verkehrsforschung, Rutherfordstr. 2, 12489 Berlin, Germany
  • 2Institut für Meteorologie, Freie Universität Berlin, Carl-Heinrich-Becker-Weg 6–10, 12165 Berlin, Germany

Abstract. We report the sensitivity of the Berlin Climate Middle Atmosphere Model (CMAM) to different gravity-wave (GW) parameterisations. We perform five perpetual January experiments: 1) Rayleigh friction (RF) (control), 2) non-orographic GWs, 3) orographic GWs, 4) orographic and non-orographic GWs with no background stress, and 5) as for 4) but with background stress. We also repeat experiment 4) but for July conditions. Our main aim is to improve the model climatology by introducing orographic and non-orographic parameterisations and to investigate the individual effect of these schemes in the Berlin CMAM. We compare with an RF control to determine the improvement upon a previously-published model version employing RF. Results are broadly similar to previously-published works. The runs having both orographic and non-orographic GWs produce a statistically-significant warming of 4-8K in the wintertime polar lower stratosphere. These runs also feature a cooling of the warm summer pole in the mesosphere by 10-15K, more in line with observations. This is associated with the non-orographic GW scheme. This scheme is also associated with a heating feature in the winter polar upper stratosphere directly below the peak GW-breaking region. The runs with both orographic and non-orographic GWs feature a statistically-significant deceleration in the polar night jet (PNJ) of 10-20ms-1 in the lower stratosphere. Both orographic and non-orographic GWs individually produce some latitudinal tilting of the polar jet with height, although the main effect comes from the non-orographic waves. The resulting degree of tilt, although improved, is nevertheless still weaker than that observed. Accordingly, wintertime variability in the zonal mean wind, which peaks at the edge of the vortex, tends to maximise too far polewards in the model compared with observations. Gravity-planetary wave interaction leads to a decrease in the amplitudes of stationary planetary waves 1 and 2 by up to 50% in the upper stratosphere and mesosphere, more in line with observations. Comparing modelled and observed Eliassen-Palm fluxes suggests that planetary wave (PW) breaking occurs too far polewards in the model. The wind and temperature changes are consistent with changes in the Brewer-Dobson (BD) circulation. Results suggest that the effect of enforcing a minimum background wave stress in the McFarlane scheme could be potentially important. In the Southern Hemisphere (SH) in July, the GW schemes had only a small impact on the high-latitude lower stratosphere but there featured strong warming near 0.1hPa.

Publications Copernicus
Download
Citation