1. RF02 SCM Intercomparison Coordinators: Matt Wyant and Chris Bretherton, UW Results submitted to date by: Andreas Chlond, MPI-Hamburg Hitoru Kitagawa, JMA Cara-Lyn Lappen, CSU Vince Larson, UW-Milwaukee Adrian Lock, UKMO Stephan de Roode, KNMI

2. Participating SCMs NameSCMTurbulenceCld. Frac. Microphys. AustinCCCMa4? ChlondECHAM4-5 moist TKE + w e pdfSundquist KitagawaJMA 1 st -order KRH-pdfSundquist LappenCAM3 [CAM3+UW] Nonlocal, sfc-based. K-profile, explicit-w e RH/stab RH Autoconv./coll., N = 65 cm -3 Larson2GPDF-HOC From pdfKhair.-Kogan w. joint pdf LockUKMO Nonlocal, explicit-w e RH-pdfAutoconv./coll., N = 100 cm -3 MenonGISS SCM Dry adjustmentRH/stabAutoconv./coll. (del Genio) Roode RACMO [EC CY23R4] K-profile, explicit-w e Tiedtke Sundquist, P  LWC

3. Case description Identical to LES case except suggested sensitivity studies: Vertical resolution : –LR: ‘Operational’  z,  t. –HR:  z =10 m,  t = 5 s Precipitation (P) vs. no precipitation (NP) Cu convection allowed (C) vs. no Cu (NC) Most SCMs don’t allow aerosol, CCN, or droplet number to be specified. Interest in relation of drizzle to LWP as well as their evolution. Results are preliminary and have known omissions, glitches.

4. LR-P-C (Default) Initialization Mainly fine. JMA loses cloud fast. UKMO drizzles a lot. CAM doesn’t have u g. RACMO dry above PBL.

5. LR-P-C Evolution LWPs  100-150 g m -2 except for JMA, RACMO. All models but JMA hold onto cloud. High-LWP models range from 0-1 mm d -1 drizzle.

6. Surface drizzle vs. LWP Diverse sensitivities. Microphysical parameterizations or droplet size assumptions?

7. Cloud-base drizzle vs. LWP Max(drizzle flux profile) Isolates production (vs. evap.)

8. High-resolution (HR-P-C) results Results broadly similar to LR. JMA holds onto cloud better. CAM and CAM-UW have higher LHF/LWP/drizzle.

9. HR surface drizzle vs. LWP Same diversity as LR.

10. Precip vs. no-precip sensitivity studies In drizzly models (except JMA), LWP increased substantially by drizzle suppression.

11. Summary SCMs display a wide variety of drizzle-LWP sensitivities, scattering on both sides of observations. In some SCMs, drizzle is substantially reducing LWP. Most SCMs could not specify 65 cm -3 cloud droplet concentration. Overall, the case specifications seem effective. Specified surface fluxes and interactive radiative cooling profiles would have been easier for SCMs.