1. The HiGEM Weather Paper Len Shaffrey NCAS-Climate, Department of Meterology, University of Reading

2. The HiGEM Weather Paper The HiGEM overview paper has been accepted by Journal of Climate ▫Revised version of the paper can be found at www.cgam.nerc.ac.uk/len/ The weather and atmospheric variability paper is slowly coming together. What impact does increasing the horizontal resolution have on weather and atmospheric variability in a coupled climate model? The goal of the paper is to evaluate against observations and compare how well aspects weather and atmospheric variability are represented in the HiGEM1.2 and HadGEM1.2 control runs.

3. The HiGEM Weather Paper The focus is on the coupled models, but where they provide insight into how the differences come about then the results from atmosphere-only runs are used as well. A list of topics to be (superficially!) covered ▫Storm tracks ▫Blocking ▫North Atlantic Oscillation ▫Madden Julian Oscillation ▫Westerly wind bursts? ▫Small-scale ocean atmosphere coupling in the extra- tropics? ▫Others? Need to answer the “So what?” question. It’s not enough to just describe the differences.

4. Storm Tracks How well are the storm tracks are represented in HiGEM1.2 and HadGEM1.2? ▫Different measures of storm tracks strength, Eulerian covariance vs Feature track densities ▫The major NH storm tracks are reasonably well represented in both HadGEM1.2. and HiGEM1.2 ▫Either this section is brief description or it includes some of the work Jen has done on “extreme” storms?

5. Courtesy of Jen Catto HiGEM1.2 ERA-40 HadGEM1.2 DJF 250hPa 2-6 day high-pass transient eddy kinetic energy

6. Blocking The representation of blocking improves in HiGEM1.2 ▫The frequency of blocking increases in HiGEM1.2, particularly in wintertime. Lots of unanswered questions about how the blocking should evaluated in coupled climate models - but they’ll have to wait for another paper. Left) 250mb geopotential height and Right) theta on PV=2 from ECMWF analysis 21/09/98

7. Blocking The representation of blocking improves in HiGEM1.2 ▫The frequency of blocking increases in HiGEM1.2, particularly in wintertime. Lots of unanswered questions about how the blocking should evaluated in coupled climate models - but they’ll have to wait for another paper. Left) 250mb geopotential height and Right) theta on PV=2 from ECMWF analysis 21/09/98

8. Right: TM DJF blocking frequencies for ERA-40, HiGEM1.2 and HadGEM1.2 Below: No of days with blocking episodes (Blocks > 9 o longitude, >5 days) in each NH sector.

9. North Atlantic Oscillation A brief description of how well the NAO is represented in HiGEM1.2 and HadGEM1.2 There is a slight improvement of the NAO in HiGEM1.2 versus HadGEM1.2. HiGEM1.2ERA-40HadGEM1.2 Courtesy of Sarah Keeley

10. Madden-Julian Oscillation The MJO is improved at higher resolution ▫The propagation speed of the MJO in HiGEM1.2 is close to observed speed (too slow in HadGEM1.2) ▫The distribution of the 20-100 day bandpass variance of OLR (Outgoing Longwave Radiation) is closer to observations in HiGEM1.2 ▫Why the improvement? Better basic state? Better representation of convection over MC? A bit of both?

11. Courtesy of Pete Inness

12. Small Scale Coupling Annual mean windstress curl and SSTs from HiGEM1.2

13. The HiGEM Weather Paper This is the plan in order to get it finished and submitted within 5 months. Finish the first five sections (which will definitely be in the paper) ▫Introduction started ▫Finalise blocking section ▫Storm Track section - what exactly to include? ▫NAO and MJO sections - figures already decided on - text to write At this point assess length of paper and decide what else to include ▫Westerly wind bursts? ▫Small scale coupling ? Then write concluding section.

14. Blocking DJF Blocking Frequency evaluated at each latitude between 30N and 75N for HiGEM and ERA-40 (1979-2001)

15. Blocking DJF Blocking frequency based on 500mb Geopotential Height index but evaluated at each latitude between 30 o N and 70 o N for ERA-40 (1957-2001). Black line: latitude of maximum 250mb total eke.

16. Blocking 500mb geopotential height blocking index (variable latitude) from HadGEM1, HadGAM1, HadAM3 and ERA-40 from Ringer et al. (2006)