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 Zhao GFDL / Princeton University September 18-21, 2006 Joint 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 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.

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 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 Summary  Tropical 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 Summary  Tropical 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 Cloud detrainment 01 fraction of environmental air virtual potential temperature

GFDL Geophysical Fluid Dynamics GFDL Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey Steady state solution for the dominant balance depend on entrainment rate cloud liquid cloud fraction steady state solution depend on both entrainment rate and cloud-base mass flux / cloud work function