© Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data...
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Transcript of © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data...
![Page 1: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/1.jpg)
© Crown copyright Met Office
CloudierEvaluating a new GCM prognostic cloud scheme using CRM dataCyril Morcrette, Reading University, 19 February 2008
![Page 2: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/2.jpg)
© Crown copyright Met Office
The need for a cloud scheme
• Clouds exists well before grid-box reaches 100% relative humidity.
• But clouds exists on scales much smaller than GCM grid boxes.
• Can’t represent them explicitly.
• Need to parameterize them.
![Page 3: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/3.jpg)
© Crown copyright Met Office
Summary of moisture variables in our Cloud Scheme
Variable Current scheme PC2
qcl (Liquid Water Content) Diagnostic Prognostic
qcf (Ice Water Content) Prognostic Prognostic
qt (Total water content) Prognostic qt=qcl+qcf
Cl (Liquid cloud fraction) Diagnostic Prognostic
Cf (Ice cloud fraction) Diagnostic Prognostic
![Page 4: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/4.jpg)
© Crown copyright Met Office
Fields from LEM simulation of TOGA-COARE (Tropical convection)
Mean qcl in env Mean qcf in env
Liquid cloud fraction Ice cloud fraction
Hei
ght
(km
)
Time (hours)
Hei
ght
(km
)
Hei
ght
(km
)H
eigh
t (k
m)
20
144
0.1 g/kg
![Page 5: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/5.jpg)
© Crown copyright Met Office
Tendencies from the LEM fields
d (qcl) / dt d (qcf) / dt
d (Cl) / dt d (Cf) / dt
0.36 / hr
0.036 g/kg/hr
![Page 6: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/6.jpg)
© Crown copyright Met Office
Increments from Convection
Detrainment
dx/dt=D(xplume-xenv)
Detrainment
Also consider:
• vertical transport by compensating subsidence
• evaporation following warming due to compensating subsidence.
(These are small effects)
![Page 7: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/7.jpg)
© Crown copyright Met Office
Increments from Convectiond (qcl) / dt
d (Cl) / dt
d (qcf) / dt
d (Cf) / dt
![Page 8: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/8.jpg)
© Crown copyright Met Office
Microphysical effects on d(qcf)/dtDeposition Sublimation
Autoconversion of ice crystals to snow Fall of ice
0.036 g/kg/hr
![Page 9: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/9.jpg)
© Crown copyright Met Office
Effects on d(qcf)/dt
All microphysics
Advection by compensating
subsidence
![Page 10: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/10.jpg)
© Crown copyright Met Office
Effects on d(Cf)/dtFall of ice
Sublimation
Advection by compensating
subsidence
![Page 11: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/11.jpg)
© Crown copyright Met Office
Effects on d(qcl)/dt Adiabatic warming by compensating
subsidenceAdvection by compensating subsidence
Large-scale forcing Boundary-layer processes
![Page 12: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/12.jpg)
© Crown copyright Met Office
Effects on d(Cl)/dt Adiabatic warming by compensating
subsidence
Boundary-layer processesLarge-scale forcing
Advection by compensating subsidence
![Page 13: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/13.jpg)
© Crown copyright Met Office
Parameterized tendenciesd (qcl) / dt d (qcf) / dt
d (Cl) / dt d (Cf) / dt
![Page 14: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/14.jpg)
© Crown copyright Met Office
Comparing Tendencies
d (qcl) / dt
d (qcf) / dt
d (Cl) / dt
d (Cf) / dt
“Truth” from LEM Parametrization
![Page 15: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/15.jpg)
© Crown copyright Met Office
Conclusions (work in progress)
• General methodology seems promising.
• Source from convective detrainment appears to be too high. (This may be due to way detrainment is calculated from LEM data)
Future work• Consider using a diagnostic cloud fraction for shallow convection which doesn’t have large anvils.
![Page 16: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/16.jpg)
© Crown copyright Met Office
Questions and answers
![Page 17: © Crown copyright Met Office Cloudier Evaluating a new GCM prognostic cloud scheme using CRM data Cyril Morcrette, Reading University, 19 February 2008.](https://reader036.fdocuments.us/reader036/viewer/2022070306/5515fa64550346cf6f8b585f/html5/thumbnails/17.jpg)
© Crown copyright Met Office
Extra figures
Massflux