RF02 SCM Intercomparison

Coordinators:Matt Wyant and Chris Bretherton, UW

Results submitted to date by:Andreas Chlond, MPI-Hamburg

Hitoru Kitagawa, JMACara-Lyn Lappen, CSU

Vince Larson, UW-MilwaukeeAdrian Lock, UKMO

Stephan de Roode, KNMI

Participating SCMs

Name SCM Turbulence Cld. Frac.

Microphys.

Austin CCCMa4?

Chlond ECHAM4-5 moist TKE + we pdf Sundquist

Kitagawa JMA 1st-order K RH-pdf Sundquist

Lappen CAM3

[CAM3+UW]

Nonlocal, sfc-based.

K-profile, explicit-we

RH/stab

RH

Autoconv./coll., N = 65 cm-3

Larson 2GPDF-HOC From pdf Khair.-Kogan w. joint pdf

Lock UKMO Nonlocal, explicit-we RH-pdf Autoconv./coll., N = 100 cm-3

Menon GISS SCM Dry adjustment RH/stab Autoconv./coll. (del Genio)

Roode RACMO

[EC CY23R4]

K-profile, explicit-we Tiedtke Sundquist, PLWC

2 3' , ' , ' '( )w w w X t

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.

LR-P-C (Default) Initialization

• Mainly fine.• JMA loses

cloud fast.• UKMO drizzles

a lot.• CAM doesn’t

have ug.

• RACMO dry above PBL.

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.

Surface drizzle vs. LWP

• Diverse sensitivities.

• Microphysical parameterizations or droplet size assumptions?

Cloud-base drizzle vs. LWP

• Max(drizzle flux profile)

• Isolates production (vs. evap.)

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.

HR surface drizzle vs. LWP

• Same diversity as LR.

Precip vs. no-precip sensitivity studies

In drizzly models (except JMA), LWP increased substantially by drizzle suppression.

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.