| CESM Research Tools: CLM4 in CESM1.0.4 User's Guide Documentation | ||
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From CLM3.5 to CLM4.0.00 there were advances in both the science and the software infrastructure. There were also new configure and namelist options as well as new history fields. In this section we will describe each of these changes in turn.
The following aspects are changes to the science in CLM4.0.00 since CLM3.5.
Changes to CLM4.0.00 beyond CLM3.5 (Oleson et al., 2008a; Stockli et al., 2008) include updates throughout the model. The hydrology scheme has been modified with a revised numerical solution of the Richards equation (Zeng and Decker, 2009; Decker and Zeng, 2009); a revised soil evaporation parameterization that removes the soil resistance term introduced in CLM3.5 and replaces it with a so-called &Bgr; formulation, as well as accounts for the role of litter and within- canopy stability (Sakaguchi and Zeng, 2009). CLM4 also includes a representation of the thermal and hydraulic properties of organic soil that operates in conjunction with the mineral soil properties (Lawrence and Slater, 2008). The ground column has been extended to ~50-m depth by adding five additional hydrologically inactive ground layers (making a total of 15 ground layers, 10 soil layers and 5 bedrock layers; Lawrence et al., 2008). An urban landunit and associated urban canyon model (CLMU) has been added which permits the study of urban climate and urban heat island effects (Oleson et al., 2008b).
The snow model is significantly modified via incorporation of SNICAR (SNow and Ice Aerosol Radiation) which represents the effect of aerosol deposition (e.g. black and organic carbon and dust) on albedo, introduces a grain-size dependent snow aging parameterization, and permits vertically resolved snowpack heating (Flanner and Zender, 2005; Flanner and Zender, 2006; Flanner et al., 2007). The new snow model also includes a new density-dependent snow cover fraction parameterization (Niu and Yang, 2007), a revised snow burial fraction over short vegetation (Wang and Zeng, 2009) and corrections to snow compaction (Lawrence and Slater, 2009).
The PFT distribution is as in Lawrence and Chase (2007) except that a new cropping dataset is used (Ramankutty et al., 2008) and a grass PFT restriction has been put in place to reduce a high grass PFT bias in forested regions by replacing the herbaceous fraction with low trees rather than grass. Grass and crop PFT optical properties have been adjusted according to values presented in Asner et al. (1998), resulting in significantly reduced albedo biases. Soil colors have been re-derived according to the new PFT distribution.
The model is extended with a carbon-nitrogen biogeochemical model (Thornton et al., 2007; Thornton et al., 2009; Randerson et al., 2009) which is referred to as CLMCN. CN is based on the terrestrial biogeochemistry Biome-BGC model with prognostic carbon and nitrogen cycle (Thornton et al., 2002; Thornton and Rosenbloom, 2005). CLMCN is prognostic with respect to carbon and nitrogen state variables in the vegetation, litter, and soil organic matter. Vegetation phenology and canopy heights are also prognostic. A detailed description of the biogeochemical component can be found in Thornton et al. (2007). Note that CLM4.0.00 can be run with either prescribed satellite phenology (CLMSP) or with prognostic phenology provided by the carbon- nitrogen cycle model (CLMCN). Additionally, a transient land cover and land use change, including wood harvest, capability has been introduced that enables the evaluation of the impact of historic and future land cover and land use change on energy, water, and momentum fluxes as well as carbon and nitrogen fluxes. The dynamic global vegetation model in CLM3.0 has been revised such that the carbon dynamics (e.g. productivity, decomposition, phenology, allocation, etc.) are controlled by CN and only the dynamic vegetation biogeography (competition) aspect of the CLM3.0 DGVM is retained. The biogenic volatile organic compounds model (BVOC) that was available in CLM3.0 has been replaced with the MEGAN BVOC model (Heald et al. 2008).
Several other minor changes have been incorporated including a change to the atmospheric reference height so that it is the height above zo+d for all surface types. The convergence of canopy roughness length zo and displacement height d to bare soil values as the above-ground biomass, or the sum of leaf and stem area indices, goes to zero is ensured (Zeng and Wang, 2007). Several corrections have been made to the way the offline forcing data is interpreted. The main change is a vastly improved and smooth diurnal cycle of incoming solar radiation that conserves the total incoming solar radiation from the forcing dataset. Additionally, in offline mode rather than partitioning incoming solar radiation into a constant 70%/30% direct vs diffuse split, it is partitioned according to empirical equations that are a function of total solar radiation. Finally, to improve global energy conservation in fully coupled simulations, runoff is split into separate liquid and ice water streams that are passed separately to the ocean. Input to the ice water comes from excess snowfall in snow-capped regions.
Taken together, these augmentations to CLM3.5 in CLM4.0.00 result in improved soil moisture dynamics that lead to higher soil moisture variability and drier soils. Excessively wet and unvarying soil moisture was recognized as a deficiency in CLM3.5 (Oleson et al. 2008a, Decker and Zeng, 2009). The revised model also simulates, on average, higher snow cover, cooler soil temperatures in organic-rich soils, greater global river discharge, lower albedos over forests and grasslands, and higher transition-season albedos in snow covered regions, all of which are improvements compared to CLM3.5.
The following aspects are changes to the software infrastructure in CLM4.0.00 since CLM3.5.
| Update to cpl7 and scripts. |
| Remove offline and cpl6 modes. |
| Remove support for CASA model. |
| Update to datm8 atmospheric data model. |
| Add gx3v7 land mask for T31 and fv-4x5 horizontal resolutions. |
| Add gx1v6 land mask for f05, f09, and f19 horizontal resolutions. |
| Add tx1v1 land mask and 1.9x2.5_tx1v1 horizontal resolution. |
| Add in 2.5x3.33 horizontal resolution. |
| Add in T62 horizontal resolution so can run at same resolution as input DATM data. |
| Allow first history tape to be 1D. |
Add ability to use own version of input datasets with CLM_USRDAT_NAME
variable. |
| Add a script to extract out regional datasets. |
| New build-namelist system with XML file describing all namelist items. |
| Add glacier_mec use-case and stub glacier model. |
| Make default of maxpatch_pft=numpft+1 instead of 4. |
| Only output static 3D fields on first h0 history file to save space. |
| Add new fields for VOC (Volatile Organic Compounds) on surface datasets, needed for the new MEGAN VOC model. |
| Add irrigation area to mksurfdata tool (NOT used in CLM yet). |
| Add multiple elevation class option for glaciers in mksurfdata tool (NOT used in CLM yet). |
| Add ascale field to land model in support of model running on it's own grid. |
Describe any changes made to build system:
| Change directory structure to match CCSM. |
| Add BGP target. |
| Add choice between ESMF and MCT frameworks. |
| Start removing #ifdef and directives that supported Cray-X1 Phoenix as now decommissioned. |
| Make default of maxpatch_pft=numpft+1 instead of 4 for all configurations. |
| By default turn on CLAMP when either CN or CASA is enabled |
| New SNICAR_FRC, CARBON_AERO, and C13 CPP ifdef tokens. |
New options added to configure: More information on options to CLM configure are given in the Section called More information on the CLM configure script in Chapter 1.
Option: -comp_intf <name>
Description: Component interface to use (ESMF or MCT) (default MCT)
Option: -nofire
Description: Turn off wildfires for bgc setting of CN (default includes fire for CN)
Option: -pio <name>
Description: Switch enables building with Parallel I/O library. [on | off] (default is on)
Option: -snicar_frc <name>
Description: Turn on SNICAR radiative forcing calculation. [on | off] (default is off)
More information on options to CLM configure are given in the Section called More information on the CLM configure script in Chapter 1.build-namelist now checks the validity of your namelist you generate by looking at data in the namelist_definition.xml file. In order to add new namelist items you need to change the code and also edit this file (e.g. a namelist option required for your research project that is not currently an option in CLM4.0.00). To view information on the namelist view the file: models/lnd/clm/bld/namelist_files/namelist_definition.xml in a browser and you'll see the names, type, description and valid_values for all namelist variables.
Changes to build-namelist:
| Allow simulation year entered to include ranges of years (i.e. 1850-2000) |
| Remove cam_hist_case option. |
| Make sure options ONLY used for stand-alone testing have a "drv_" or "datm_" prefix in them and list these options all together and last when asking for help from build-namelist. |
New option to build-namelist:
-clm_usr_name "name" Dataset resolution/descriptor for personal datasets.
Default: not used
Example: 1x1pt_boulderCO_c090722 to describe location,
number of pts, and date files created
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New list options to build-namelist
cd models/lnd/clm/bld
./build-namelist -res list # List valid resolutions
./build-namelist -mask list # List valid land-masks
./build-namelist -sim_year list # List valid simulation years and simulation year ranges
./build-namelist -clm_demand list # List namelist variables including those you could
# demand to be set.
./build-namelist -use_case list # List valid use-cases
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New use-cases for build-namelist:
1850_control = Conditions to simulate 1850 land-use
2000_control = Conditions to simulate 2000 land-use
20thC_transient = Simulate transient land-use, aerosol and Nitrogen deposition
from 1850 to 2005
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New namelist items:
urban_hac = OFF, ON or ON_WASTEHEAT (default OFF) Flag for urban Heating
and Air-Conditioning
OFF = Building internal temperature is un-regulated.
ON = Building internal temperature is bounded to reasonable range.
ON_WASTEHEAT = Building internal temperature is bounded and resultant waste
heat is given off.
urban_traffic = .true. or .false. Flag to include additional multiplicative
factor of urban traffic to sensible heat flux.
(default .false.)
fsnowoptics = filename file for snow/aerosol optical properties (required)
fsnowaging = filename file for snow aging parameters (required)
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CLM_BLDNML_OPTS.
More information on the build-namelist options are given in in the Section called Definition of Namelist items and their default values in Chapter 1.
New history variables: (note watt vs. W in units, 26 vs. 76)
Name: BCDEP
Long-name: total BC deposition (dry+wet) from atmosphere
Units: kg/m^2/s
Name: BIOGENCO
Long-name: biogenic CO flux
Units: uGC/M2/H
Name: C13_PRODUCT_CLOSS
Long-name: C13 total carbon loss from wood product pools
Units: gC13/m^2/s
Name: DSTDEP
Long-name: total dust deposition (dry+wet) from atmosphere
Units: kg/m^2/s
Name: EFLX_DYNBAL
Long-name: dynamic land cover change conversion energy flux
Units: W/m^2
Name: FGR12
Long-name: heat flux between soil layers 1 and 2
Units: watt/m^2
Name: FSAT
Long-name: fractional area with water table at surface
Units: unitless
Name: FSH_NODYNLNDUSE
Long-name: sensible heat flux not including correction for land use change
Units: watt/m^2
Name: GC_HEAT1
Long-name: initial gridcell total heat content
Units: J/m^2
Name: GC_HEAT2
Long-name: post land cover change total heat content
Units: J/m^2
Active/Inactive: inactive
Name: GC_ICE1
Long-name: initial gridcell total ice content
Units: mm/s
Name: GC_ICE2
Long-name: post land cover change total ice content
Units: mm/s
Active/Inactive: inactive
Name: GC_LIQ1
Long-name: initial gridcell total liq content
Units: mm
Name: GC_LIQ2
Long-name: initial gridcell total liq content
Units: mm
Active/Inactive: inactive
Name: H2OSNO_TOP
Long-name: mass of snow in top snow layer
Units: kg
Name: HEAT_FROM_AC
Long-name: sensible heat flux put into canyon due to heat removed from air conditioning
Units: watt/m^2
Name: HK
Long-name: hydraulic conductivity
Units: mm/s
Active/Inactive: inactive
Name: ISOPRENE
Long-name: isoprene flux
Units: uGC/M2/H
Name: LAND_USE_FLUX
Long-name: total C emitted from land cover conversion and wood product pools
Units: gC/m^2/s
Name: LAND_UPTAKE
Long-name: NEE minus LAND_USE_FLUX, negative for update
Units: gC/m^2/s
Name: LWup
Long-name: upwelling longwave radiation
Units: watt/m^2
Active/Inactive: inactive
Name: MONOTERP
Long-name: monoterpene flux
Units: uGC/M2/H
Name: NBP
Long-name: net biome production, includes fire, landuse, and harvest flux, positive for sink
Units: gC/m^2/s
Name: OCDEP
Long-name: total OC deposition (dry+wet) from atmosphere
Units: kg/m^2/s
Name: OVOC
Long-name: other VOC flux
Units: uGC/M2/H
Name: ORVOC
Long-name: other reactive VOC flux
Units: uGC/M2/H
Name: PBOT
Long-name: atmospheric pressure
Units: Pa
Name: PCO2
Long-name: atmospheric partial pressure of CO2
Units: Pa
Name: PRODUCT_CLOSS
Long-name: total carbon loss from wood product pools
Units: gC/m^2/s
Name: PRODUCT_NLOSS
Long-name: total N loss from wood product pools
Units: gN/m^2/s
Name: Qair
Long-name: atmospheric specific humidity
Units: kg/kg
Active/Inactive: inactive
Name: Qanth
Long-name: anthropogenic heat flux
Units: watt/m^2
Active/Inactive: inactive
Name: Qtau
Long-name: momentum flux
Units: kg/m/s^2
Name: QFLX_LIQ_DYNBAL
Long-name: liq dynamic land cover change conversion runoff flux
Units: mm/s
Name: QFLX_ICE_DYNBAL
Long-name: ice dynamic land cover change conversion runoff flux
Units: mm/s
Name: QRUNOFF_NODYNLNDUSE
Long-name: total liquid runoff not including correction for land use change (does not include QSNWCPICE)
Units: mm/s
Name: QSNWCPICE
Long-name: excess snowfall due to snow capping
Units: mm/s
Name: QSNWCPICE_NODYNLNDUSE
Long-name: excess snowfall due to snow capping not including correction for land use change
Units: mm/s
Name: QSNWCPLIQ
Long-name: excess rainfall due to snow capping
Units: mm/s
Active/Inactive: inactive
Name: SMP
Long-name: soil matric potential
Units: mm
Active/Inactive: inactive
Name: SNOAERFRC2L
Long-name: surface forcing of all aerosols in snow, averaged only when snow is present (land)
Units: watt/m^2
Name: SNOAERFRCL
Long-name: surface forcing of all aerosols in snow (land)
Units: watt/m^2
Name: SNOBCFRCL
Long-name: surface forcing of BC in snow (land)
Units: watt/m^2
Name: SNOBCMCL
Long-name: mass of BC in snow column
Units: kg/m2
Name: SNOBCMSL
Long-name: mass of BC in top snow layer
Units: kg/m2
Name: SNOdTdzL
Long-name: top snow layer temperature gradient (land)
Units: K/m
Name: SNODSTFRC2L
Long-name: surface forcing of dust in snow, averaged only when snow is present (land)
Units: watt/m^2
Name: SNODSTFRCL
Long-name: surface forcing of dust in snow (land)
Units: watt/m^2
Name: SNODSTMCL
Long-name: mass of dust in snow column
Units: kg/m2
Name: SNODSTMSL
Long-name: mass of dust in top snow layer
Units: kg/m2
Name: SNOFSRND
Long-name: direct nir reflected solar radiation from snow
Units: watt/m^2
Active/Inactive: inactive
Name: SNOFSRNI
Long-name: diffuse nir reflected solar radiation from snow
Units: watt/m^2
Active/Inactive: inactive
Name: SNOFSRVD
Long-name: direct vis reflected solar radiation from snow
Units: watt/m^2
Active/Inactive: inactive
Name: SNOFSRVI
Long-name: diffuse vis reflected solar radiation from snow
Units: watt/m^2
Active/Inactive: inactive
Name: SNOFSDSND
Long-name: direct nir incident solar radiation on snow
Units: watt/m^2
Active/Inactive: inactive
Name: SNOFSDSNI
Long-name: diffuse nir incident solar radiation on snow
Units: watt/m^2
Active/Inactive: inactive
Name: SNOFSDSVD
Long-name: direct vis incident solar radiation on snow
Units: watt/m^2
Active/Inactive: inactive
Name: SNOFSDSVI
Long-name: diffuse vis incident solar radiation on snow
Units: watt/m^2
Active/Inactive: inactive
Name: SNOLIQFL
Long-name: top snow layer liquid water fraction (land)
Units: fraction
Active/Inactive: inactive
Name: SNOOCMCL
Long-name: mass of OC in snow column
Units: kg/m2
Name: SNOOCMSL
Long-name: mass of OC in top snow layer
Units: Kg/m2
Name: SNOOCFRC2L
Long-name: surface forcing of OC in snow, averaged only when snow is present (land)
Units: watt/m^2
Name: SNOOCFRCL
Long-name: surface forcing of OC in snow (land)
Units: watt/m^2
Name: SNORDSL
Long-name: top snow layer effective grain radius
Units: m^-6
Active/Inactive: inactive
Name: SNOTTOPL
Long-name: snow temperature (top layer)
Units: K/m
Active/Inactive: inactive
Name: SWup
Long-name: upwelling shortwave radiation
Units: watt/m^2
Active/Inactive: inactive
Name: TSOI_10CM
Long-name: soil temperature in top 10cm of soil
Units: K
Name: URBAN_AC
Long-name: urban air conditioning flux
Units: watt/m^2
Name: URBAN_HEAT
Long-name: urban heating flux
Units: watt/m^2
Name: VOCFLXT
Long-name: total VOC flux into atmosphere
Units: uGC/M2/H
Name: Wind
Long-name: atmospheric wind velocity magnitude
Units: m/s
Active/Inactive: inactive
Name: WOOD_HARVESTC
Long-name: wood harvest (to product pools)
Units: gC/m^2/s
Name: WOOD_HARVEST
Long-name: wood harvest (to product pools)
Units: gN/m^2/s
History field name changes:
Old: ANNSUM_PLANT_NDEMAND
New: = ANNSUM_POTENTIAL_GPP
Old: ANNSUM_RETRANSN
New: = ANNMAX_RETRANSN
Old: C13_DWT_PROD10C_LOSS
New: = C13_PROD10C_LOSS
Old: C13_DWT_PROD100C_LOSS
New: = C13_PROD100C_LOSS
Old: C13_DWT_PROD10N_LOSS
New: = C13_PROD10N_LOSS
Old: C13_DWT_PROD100C_LOSS
New: = C13_PROD100C_LOSS
Old: DWT_PROD100N_LOSS
New: = PROD10N_LOSS
Old: DWT_PROD100N_LOSS
New: = PROD100N_LOSS
Old: DWT_PROD100C_LOSS
New: = PROD10C_LOSS
Old: DWT_PROD100C_LOSS
New: = PROD100C_LOSS
Old: HCSOISNO
New: = HC
Old: TEMPSUM_PLANT_NDEMAND
New: = TEMPSUM_POTENTIAL_GPP
Old: TEMPSUM_RETRANSN
New: = TEMPMAX_RETRANSN
History field names deleted include: SNOWAGE, TSNOW, FMICR, FCO2, DMI, QFLX_SNOWCAP
Add new urban oriented _U, and _R (Urban and Rural) for the following history variables: EFLX_LH_TOT, FGR, FIRA, FSH, FSM, Q2M, QRUNOFF, RH2M, SoilAlpha, TG, TREFMNAV, TREFMXAV, and TSA (missing _R for SoilAlpha as the regular SoilAlpha is only defined for rural areas anyway)
Note: We are missing the Rural soil-alpha variable: SoilAlpha_R on purpose. SoilAlpha_U is only defined over pervious road, and missing everywhere else. SoilAlpha is defined only for rural areas.