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GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
AM2 cloud sensitivity to details of convection and cloud paramerization – the GPCI case
Ming ZhaoGFDL / Princeton University
September 18-21, 2006Joint GCSS-GPCI / BLCL - RICO Workshop
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Outline
• AM2 cloud and convection parameterization
• Experiments
• Results
• Summary
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Tiedtke prognostic cloud scheme
radturbp
c
cond
l
t
T
t
T
c
gM
t
q
p
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t
q lclcl
conv
l
,
microerosevapcondconv
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q
t
q
t
q
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dt
dq llllll
AM2 cloud and convection parameterization
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Relaxed Arakawa-Schubert (RAS) convection scheme
Cloud model: Ensemble entraining plumes with each entrainment rate calculated
so that it reaches a model level with neutral buoyancy
Non-entraining plumes
Tokioka entrainment rate limiter
Applying Tokioka limiter only to deep plumes above 500 hPa
Local modification of critical cloud work function
Closure: Relax plume cloud work function to specified critical values with
specified time-scale.
025.0,0 LCLz
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
UW shallow cumulus scheme (Bretherton et. al 2004)
Cloud model: Bulk entrainment-detrainment plume Buoyancy-sorting determination of entrainment/detrainment rate Explicit vertical momentum equation Cumulus cloud-top penetrative mixing
Closure: Cloud-base mass flux is determined by boundary layer TKE and
convective inhibition (CIN).
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Experiments (GPCI 1998)• CNTRL : AM2 default with FV dynamic core
• NOSHA: Same as CNTRL except disallowing RAS plumes below 500hPa
• NONON: Same as CNTRL except applying Tokioka to all RAS plumes (eliminating non-entraining plume)
• UWSCU: Same as NONON except applying UW-ShCu before RAS, and disallowing RAS plumes below UW-ShCu calculated convective depth H
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Results
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Liquid water path
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
SW absorption at TOA
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud fraction
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud liquid (g/kg)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud liquid water tendencies from convection (g/kg/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud liquid water tendencies from large-scale condensation (g/kg/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Large-scale/stratiform precipitation
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Specific humidity tendencies from convection (g/kg/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Relative humidity
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Convective mass flux (kg/m2/s)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
radturbp
c
cond
l
t
T
t
T
c
gM
t
q
NOGMC case
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
CNTRL vs. NOGMC
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
CNTRL vs NOGMC
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
SummaryTropical low cloud fraction and condensate are susceptible
to the detailed treatment of shallow convection. Weaker shallow convection leads to large increase of low clouds.
Budget analysis show that the increase of low clouds is due to increased large-scale condensation instead of convective detrainment.
Sensitivity study show that wetter lower troposphere and reduced compensating subsidence resulting from weaker shallow convection are two primary causes.
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
End
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Total precipitation
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud fraction tendencies from convection (1/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud fraction tendencies from large-scale formation (1/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud fraction tendencies from turbulent erosion (1/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud liquid tendencies from large-scale evaporation (g/kg/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud liquid tendencies from turbulent erosion (g/kg/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Cloud liquid tendencies from microphysics (g/kg/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Vertical pressure velocity (hPa/day)
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
SummaryTropical low cloud fraction and condensate are susceptible
to the detailed treatment of shallow convection. Weaker shallow convection leads to large increase of low clouds.
Budget analysis show that the increase of low clouds is due to large-scale condensation instead of convective detrainment.
Budget analysis and sensitivity study show that wetter lower troposphere and reduced compensating subsidence resulting from weaker shallow convection are two primary causes.
GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
Sub-cloud layer TKE and cloud detrainment
Sub-cloud TKE 0''
TKE
wbt
TKEs
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Cloud detrainment luul
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fraction of environmental air
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entrained be tomixturesfor air
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ratet entrainmen : 0
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GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey
m500/sgm 2
gkg 8
s x105
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1
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Steady state solution for the dominant balance
depend on entrainment rate
cloud liquid
cloud fraction
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steady state solution
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depend on both entrainment rate and cloud-base mass flux / cloud work function
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