1. HIRDLS Science Meeting 1 26 June 2008 A Comparison of HIRDLS and the Hadley Centre Model: Extratropical Variability University of Oxford Scott Osprey, Corwin Wright, John Barnett, Lesley Gray

2. 26 June 2008HIRDLS Science Meeting2 Overview HIRDLS Scientific Objectives HIRDLS Scientific Objectives Case-Study: NH Stratosphere, February 2006 Case-Study: NH Stratosphere, February 2006 Stratosphere resolving Met Office GCM, MetUM L60 Stratosphere resolving Met Office GCM, MetUM L60 Model Runs: Can we model these winters? Model Runs: Can we model these winters? Conclusion and Future work Conclusion and Future work

3. 26 June 2008HIRDLS Science Meeting3 HIRDLS: Scientific Objectives Understand chemical processes, transports and mixing in the upper-troposphere/lower stratosphere. Understand chemical processes, transports and mixing in the upper-troposphere/lower stratosphere. Understand stratosphere-troposphere exchange of a variety of gases/aerosols at a fine scales Understand stratosphere-troposphere exchange of a variety of gases/aerosols at a fine scales Better evaluate the budgets of; momentum, energy, heat and PV, which help mitigate this exchange Better evaluate the budgets of; momentum, energy, heat and PV, which help mitigate this exchange To provide data to help constrain and validate models. To provide data to help constrain and validate models.

4. 26 June 2008HIRDLS Science Meeting4 NH Winter Temperatures 2005 &2006

5. 26 June 2008HIRDLS Science Meeting5 NH Winter Zonal Wind 2005 &2006

6. 26 June 2008HIRDLS Science Meeting6 NH Winter Zonal Wind 2005 &2006 (HIRDLS)

7. 26 June 2008HIRDLS Science Meeting7 HIRDLS Gravity Waves Missing gravity waves?

8. 26 June 2008HIRDLS Science Meeting8 Are the circulation changes related to the change in gravity wave activity seen by HIRDLS?

9. 26 June 2008HIRDLS Science Meeting9 The New Dynamics Unified Model Solves a non-hydrostatic, semi-Lagrangian system using a semi-implicit time-stepping scheme Solves a non-hydrostatic, semi-Lagrangian system using a semi-implicit time-stepping scheme Thought better able to accommodate changes in spatial resolution. Thought better able to accommodate changes in spatial resolution. Arakawa C-grid with Charney-Philips staggering in the vertical (‘scalar’: θ, w, tracers; ‘vector’: P, ρ, u) Arakawa C-grid with Charney-Philips staggering in the vertical (‘scalar’: θ, w, tracers; ‘vector’: P, ρ, u) Will also be able to better resolve particular phenomena. Will also be able to better resolve particular phenomena.

10. 26 June 2008HIRDLS Science Meeting10 MetUM L60 Vertical Resolution ~35 Levels in stratosphere (MetUM L60) 1km vertical resolution in stratosphere (HIRDLS)

11. 26 June 2008HIRDLS Science Meeting11 Model Run Setup Horizontal resolution 2.5 x 3.75 Horizontal resolution 2.5 x 3.75 4 x 25 year runs (1975-2000) 4 x 25 year runs (1975-2000) Contemporaneous SSTs, CO 2, methane, CFCs Contemporaneous SSTs, CO 2, methane, CFCs Climatological ozone Climatological ozone Spectral & orographic gravity wave schemes (USSP) Spectral & orographic gravity wave schemes (USSP) Methane oxidation Methane oxidation

12. 26 June 2008HIRDLS Science Meeting12 MetUM L60 Temperature

13. 26 June 2008HIRDLS Science Meeting13 MetUM L60 Zonal Wind

14. 26 June 2008HIRDLS Science Meeting14 Residual Mean Meridional Wind

15. 26 June 2008HIRDLS Science Meeting15 Residual Mean Vertical Wind

16. 26 June 2008HIRDLS Science Meeting16 Eliassen-Palm Flux

17. 26 June 2008HIRDLS Science Meeting17 MetUM L60 GW Momentum Fluxes EastwardWestward Northward Southward

18. 26 June 2008HIRDLS Science Meeting18

19. 26 June 2008HIRDLS Science Meeting19 MetUM L60 Gravity Waves

20. 26 June 2008HIRDLS Science Meeting20 Summary NH winter 2006 characterised by unusually elevated stratopause over pole. NH winter 2006 characterised by unusually elevated stratopause over pole. Linked with this was an anomalously strong vortex in the upper stratosphere overlying anomalously weak zonal winds in the lower stratosphere. Linked with this was an anomalously strong vortex in the upper stratosphere overlying anomalously weak zonal winds in the lower stratosphere. HIRDLS has observed reduced GW activity entering the lower stratosphere during these times. HIRDLS has observed reduced GW activity entering the lower stratosphere during these times. GCM studies have linked similar reductions in GW activity during similar events. These link with circulations in the upper stratosphere/lower mesosphere which help maintain the winter polar stratospause. GCM studies have linked similar reductions in GW activity during similar events. These link with circulations in the upper stratosphere/lower mesosphere which help maintain the winter polar stratospause.