1. © Crown copyright Met Office Met Office SCM and CRM results Adrian Lock, Met Office, UK

2. © Crown copyright Met Office Met Office LEM/CRM set-up Use 2D “LES” with Dx=50m, Dz=20m in 6.4km domain (top at 8km) Started with Dx=100m, Dz=50m in 12.8km domain and higher resolution very similar Otherwise LEM set-up as for GCSS-RICO Run for 30 days (takes ~1 day to run) Run Control and +2K for points 6, 11, 12

3. © Crown copyright Met Office Met Office SCM set-up Run parallel simulations in the Met Office SCM based on runs by Charmaine Franklin at CSIRO Run for 100 days Confession: I’ve used the development version of the climate model, HadGEM3, instead of the proposed AR5 model HadGEM2 Test sensitivity to resolution L38 (~300m at 1km, as used in HadGEM2) L63 (~160m at 1km, as used in HadGEM3)

4. © Crown copyright Met Office S6 profiles after 30 days 5 day mean in SCM (3 hour mean in CRM) SCM gives significantly deeper cumulus than CRM (4km cf 2km) but reasonable cloud cover profile and massflux SCM gives drier (warmer) BL Cloud fractionMassfluxHumidity (g/kg) Ctl +2K

5. © Crown copyright Met Office S6 time series Unsmoothed

6. © Crown copyright Met Office S6 time series 2 day means SCM cloud cover matches CRM, especially at L63 Too much precipitation in SCM (cumulus too deep) No sign of any cloud feedback in SCM or CRM

7. © Crown copyright Met Office S11 profiles after 30 days 5 day mean in SCM (3 hour mean in CRM) Cloud fractionMassfluxHumidity (g/kg) Ctl +2K SCM again gives deeper BL than CRM SCM gives greater cloud cover underneath the inversion

8. © Crown copyright Met Office S11 time series Unsmoothed

9. © Crown copyright Met Office S11 time series 2 day means Cloud cover much higher in SCM than CRM; L38 very noisy Too much precipitation again in SCM SCM has positive feedback, ~independent of resolution No feedback in CRM

10. © Crown copyright Met Office S12 profiles after 30 days 5 day mean in SCM (3 hour mean in CRM) Cloud fraction Ctl +2K CRM boundary layer very shallow and cloud free SCM similar to s11 Humidity (g/kg)

11. © Crown copyright Met Office S12 time series 2 day means CRM: no cloud, so no feedback SCM has positive feedback at L63, negative at L38

12. © Crown copyright Met Office Cloud feedback mechanisms for S11 See Mark Webb’s talk Lower-tropospheric stability (LTS) Theta difference between 3km and surface Control LTS = 22.75K +2K LTS= 23.8K So S11 shows increase in LTS, similar to GCMs Does LTS implies increase in cloud = negative feedback? CTEI parameter, based on inversion jumps: Control = (11.0 -15.0) / (-15.0) = - 4.0 /-15.0 = 0.27 +2K = (11.25-16.6) / (-16.5) = -5.25/-16.5 = 0.32 So S11 shows increase in, similar to GCMs LES (Lock, 2009) suggest increase implies reduction in cloud cover, at least for Sc over Cu, = positive feedback

13. © Crown copyright Met Office Lock (2009): factors influencing cloud area at the inversion for shallow cumulus

14. © Crown copyright Met Office Summary Lack of stratocumulus in CRM at s11, s12 is a concern I’ll try 3D on our new supercomputer when I get back SCM has a tendency to give deeper boundary layers than the CRM SCM reasonably resolution independent, except for s12 Climate change impact on LTS and kappa appears consistent with that seen in GCMs

15. © Crown copyright Met Office Summary SW feedback (Wm -2) S6S11S12 CRM00No cloud SCM L38010-70 SCM L6301070

16. © Crown copyright Met Office Questions?