Community Climate System Model 4

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Community Climate System Model 4 (CCSM4) Model
Configuration and CMIP5 plans
Gerald Meehl NCAR
2
Two Tracks for the Community Atmospheric Model
(CAM)
Track 1

• Essentially CAM3.5
• Modifications to convection (better El Nino)
• Substantial code revisions
• Remaining parameterizations as in CAM3, but
• FV dynamical core becomes default
• Polar filters GW Froude number
• All aerosols can be interactive (for CAM3, only
  Sulfur and Soot were calculated)
• prescribed aerosol datasets
• Revised aerosol optics

• Coupled to other new surface components
• Defined as CAM4 within CCSM4

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Two Tracks for CAM
Track 5

• CAM3.5
• New cloud microphysics
• Revised ice clouds
• PDF based warm cloud fraction
• New Radiative Transfer
• New PBL and Shallow convection
• New macrophysics
• New aerosol formulation
• Tweaks to GWD and Mountain form drag
• Volcanic Aerosols
• Radiatively active consistent convective clouds

• The bleeding edge model
• Explicit connections between boundary layer
  processes, shallow clouds, and cloud fraction
• Much more flexibility, power, accuracy in
  radiative transfer calculation
• two moment (mass number) treatments for
  clouds and aerosols
• Modal aerosols, internal mixtures
• Explicit connections between aerosols, clouds,
  drop and crystal activation, allowing treatment
  of Aerosol Indirect Effect (Total AIE
  1.2-1.5W/m2)
• Much more consistent treatment of condensed
  species for radiation, microphysics,
  sedimentation, scavenging, etc
• Much more consistent treatment of condensation
  cloud fraction evolution
• Stronger connections between clouds, the PBL, and
  the surface

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Ocean Component
Changes relative to CCSM3

• POP2 base code, including many infrastructure
  changes
• Increased vertical resolution (60-levels) and
  changes in bottom topography
• Modified anisotropic horizontal viscosity scheme
• Near-surface eddy flux parameterization (CPT)
• Vertically-varying isopycnal and thickness
  diffusivities (CPT)
• Sub-Mesoscale parameterization (CPT)
• Overflow parameterization (CPT)
• Tidally driven mixing scheme

• Horizontally-varying internal wave breaking
• Zenith angle dependent diurnal cycle of solar
  forcing
• Flux limited advection scheme (Lax-Wendroff)
• Passive tracer infrastructure and ecosystem codes
  are operational

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Sea Ice Component
Changes relative to CCSM3

• Community Ice Code (CICE) 4.0 Base Code
• Delta-Eddington Radiative Transfer in sea ice and
  snow
• Melt Pond Parameterization
• Arbitrary Number of Tracers (for example age,
  melt ponds, aerosols)
• Aerosol cycling and deposition on sea ice / snow

6
Land Component
Changes relative to CCSM3

• Carbon/nitrogen cycle model
• Based on BIOME BGC prognostic phenology
• Transient land use/land cover change
• Address the biogeophysical and biogeophysical
  impact of LULC change
• Urban model
• Heat island direct impact of climate change on
  human health, e.g. heat waves
• Revised soil hydrology
• Improved soil moisture storage/annual cycle,
  partitioning of ET into its components, soil
  moisture variability
• Revised snow model
• New snow cover fraction aerosol deposition onto
  snow (new climate feedback) vertically resolved
  heating new snow age parameterization snow
  burial of short vegetation
• Permafrost
• Insulating effect of organic soil, deep soil
  column
• Revised Dynamic Global Vegetation Model
• Integrated with carbon/nitrogen model added
  shrub PFT

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Ocean Ecosystem Component

• Improved sedimentary iron source and scavenging
  parameterizations
• Reduces mismatch with observations (Moore and
  Braucher, 2008)
• Improved phytoplankton dynamic Si/C and Fe/C
  ratios
• Improves surface silicate and dissolved iron
  distributions
• Modifications to phytoplankton loss terms
• Better bloom dynamics and seasonal nutrient
  drawdown at high latitudes
• Incorporation of atmospheric N, P, and Si (in
  addition to Fe)
• N has modest impacts, and deposition is changing
  rapidly since preindustrial
• P and Si from the atmosphere have very small
  impact on C cycle
• Diazotroph utilization of fixed N sources
  (nitrate, ammonium) (Moore, submitted)
• Diazotrophs can fix N2, but now also take up
  fixed N when available
• Modified O2/Denitrification effect on
  remineralization lengths
• Length scales grow longer at low O2

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CCSM Contributions to CMIP5

• Long-term simulations
• Track 1 at 1 horizontal resolution
• Both with and without coupled carbon cycle
• All core experiments some Tier 1 and Tier 2
• Track 5
• Some core, but none with coupled carbon cycle
• Some Tier 1
• Likely smaller ensembles than Track 1
• WACCM (next slide)

• Decadal simulations
• Ocean initialization via data assimilation
• Majority with Track 1
• 1 and likely 1/2 horizontal resolution
• Some with Track 5
• Some with WACCM?

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CCSM Contributions to CMIP5

• Time slice simulations
• Track 1 at 35 km horizontal resolution

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WACCM and CMIP5

• Based on Track 1 1.9 x 2.5 CCSM4.0
  configuration
• Atmospheric component
• Fully-interactive chemistry with 57 species
• Includes heterogeneous chemistry necessary for
  ozone hole development recovery
• Extensively validated in SPARC/CCMVal 2
• CLM3 / POP2 / CICE4 as in Track 1
• Planned minimum of 3 runs from 1960 to 2050
• 45 years of retrospective 20th Century
• 45 years using the RCP 4.5 scenario