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On the new CCSM boundary layerphysics interactions & the subtropical South Atlantic
Brian [email protected] Center for Atmospheric Research, Boulder, CO, USA
CESM
NCAR is sponsored by the National Science Foundation
NCAR Earth System Laboratory,Climate & Global Dynamics Division,Atmospheric Modeling & Predictability
Saturday, April 9, 2011
Low cloud climatology
Saturday, April 9, 2011
!"#$% &&'!()!"##$% &&'!(*+)!"##&% &&'!,)!'()*"#+#% &-'!.)!,-.*"#+#%!"#$%&'()( *!+,-./012 *!+,34-./012 *!+5-./012- *!+4-./,62Boundary Layer Holtslag and Boville
(93)Holtslag and Boville Holtslag and Boville UW Diagnostic TKE
Park et al. (09)
Shallow Convection
Hack (94) Hack Hack UW TKE/CIN Park et al. (09)
Deep Convection
Zhang and McFarlane (95)
Zhang and McFarlaneNeale et al.(08), Richter and Rasch (08) mods.
Zhang and McFarlaneNeale et al., Richter and Rasch mods.
Zhang and McFarlaneNeale et al., Richter and Rasch mods.
Stratiform Cloud Rasch and Kristjansson (98)Single Moment
Rasch and K.Single Moment
Rasch and K.Single Moment
Morrison and Gettelman(08)Double Moment
Park MacrophysicsPark et al. (10)
Radiation CAMRT (01) CAMRT CAMRT RRTMG Iacono et al. (2008)
Aerosols Bulk Aerosol Model (BAM)
BAM BAM Modal Aerosol Model (MAM)Ghan et al. (2010)
Dynamics Spectral Finite Volume (96,04)
Finite VolumeHOMME
Finite VolumeHOMME
78(9: ;7;0-./562 ;7;03<-./162 ;7;030 ;7;030-= !"#
/9:> */+,- */+,34- */+5-= #$ */+5-
?(9-@8( *?@+5 *?@+5 *@*A *@*A
CAM Evolution
Slide stolen from Rich Neale
CCSM-CESM/CAM Evolution
Saturday, April 9, 2011
CAM4 v. CAM5 Physics
*Vertical Diffusion
1. Turbulent Mountain Stress
2. Eddy Diffusivity
A. compute_eddy_diff (CAM5, store TKE for shcu)
B. compute_hb_diff (CAM4)
3. Diffusion solver (compute_vdiff)
Dry Adjustment
Deep Convection
Shallow Convection
Stratiform
RadiationSurface Fluxes
Emissions/Tracers/
Chemistry
Vertical Diffusion*
Rayleigh Friction
Gravity Wave Drag
Aerosol Dry Deposition
Dynamics
Saturday, April 9, 2011
Moist turbulence & low clouds
TKE
Entrainment
Turbulent Mixing
Surface fluxes
Cloud-top Cooling
Turbulent Mixing
“Penetrative Entrainment” Updraft Mass
Flux
TKE
“Convective Layer”
Saturday, April 9, 2011
CAPT Forecasts
ForecastInitialization Finite Volume dynamics
Δx = 2.5°Δy = 1.9°Δt = 30 minutes
Saturday, April 9, 2011
What controls the cloud water come from?
!q!!t
= !V ·"q! + P (q!)
P (q!) = TPBL + CTrans + CDet +M
Mean cloud structure, SE Pacific
Falling down Breaking up
Saturday, April 9, 2011
Examples
LCL
PBL Top
alpha_q
CAM4 CAM5 g/kgg/kg
Saturday, April 9, 2011
Decoupling
Deep, well-mixed stratocumulus
Thin stratus -OR-decoupled layers
Saturday, April 9, 2011
SE Pacific sensitivity experiments
CAM4, RHMINL = 85, 80CAM4, RHMINL = 95 CAM5, RPEN = 2.5, 5
Saturday, April 9, 2011
Forecasts of the south Atlantic
October 2006 Prescribed SSTLow level windLow-level cloud
CAM5Finite Volume dynamicsΔx = 2.5°Δy = 1.9°Δt = 30 minutes
CAUTION:
Danger
ously P
reliminar
y
Saturday, April 9, 2011
Selecting south Atlantic Sc
Saturday, April 9, 2011
South Atlantic mean forecast
Center of cloud layer lower & drier than SEPac
Saturday, April 9, 2011
Cloud water budget termsSouth Atlantic South Pacific
Saturday, April 9, 2011
Decoupling in the Atlantic?
Deep, well-mixed stratocumulus
Thin stratus -OR-decoupled layers
Saturday, April 9, 2011
Concluding thoughts?
UW Moist Turbulence scheme improves cloud-topped boundary layers.
‣ Improved physics interactions.
Pros/Cons seen in Sc forecasts:
‣CAM5 able to maintain well mixed PBL, driven by cloud-top cooling.
‣Tight coupling of moist physics plays into daily breakup of cloud deck.
Understanding these interactions, e.g., decoupling, can shed light on climate errors.
Southeast Atlantic vs. Southeast Pacific
Dry Adjustment
Deep Convection
Shallow Convection
Stratiform
Radiation
Surface Fluxes
Emissions/Tracers/
Chemistry
Vertical Diffusion*
Rayleigh Friction
Gravity Wave Drag
Aerosol Dry Deposition
Dynamics
Saturday, April 9, 2011
