ALMA Standard Model Output


A summary of standard output variable definitions for land surface scheme intercomparisons is given below. It is expected that this list will grow over time as the requirement of the various GLASS projects becomes known.

As indicated in the table, one of two sign conventions may be adopted at the discretion of the participant. All output variables must conform to one of these two conventions. The choice must be included in the netCDF header information of the output file.

The time sampling of each of the variables will be specified by each inter-comparison project. This is an issue which depends on the data available for validation and the scientific objectives of the project. As a general rule fluxes are averaged over the time-step. Other variables on the contrary should be instantaneous samples in order to capture well the diurnal cycleor total change. This obviously only applies if the time sampling is high enough for the instantaneous variables to be representative of the time interval. For this table, variables which must be returned as averages are in red.

The variables have been grouped into seven general categories which go from very general to highly specialized :

O.1) General energy balance components
This table should provide the main energy fluxes at the surface so that a verification of the long term energy balance can be made.
O.2) General water balance components
In this table all grid-averaged components of the water balance are requested. These components should enable an analysis of the water balance of the model.
O.3) Surface state variables
This table provides the basic state variables at the surface which are simulated by the schemes.It documents in a general way the simulated evolution of the surface.
O.4) Sub-surface state variables
In this table the state of the subsurface is described. Its thermodynamics as well as its hydrological conditions are described without going into the details of the various processes.
O.5) Evaporation components
This table details the evaporation fluxes and thus describes all the components which make up the water flux from the surface to the atmosphere.
O.6) Streamflow
This specialized table documents the lateral flow of water in the land-surface scheme if it is simulated.
O.7) Cold season processes
This specialized table will document in as much details as possible the simulated cold season processes.

O.1) General energy balance components:

(Expected range)

Variable
Description
Definition
Units
Positive Dir. (Traditional)
Positive Dir. (Mathematical)
Priority
SWnet
Net shortwave radiation
Incoming solar radiation less the simulated outgoing shortwave radiation, averaged over a grid cell
W/m2
Downward
Downward
Mandatory
LWnet
Net longwave radiation
Incident longwave radiation less the simulated outgoing longwave radiation, averaged over a grid cell
W/m2
Downward
Downward
Mandatory
Qle
Latent heat flux
Energy of evaporation, averaged over a grid cell
W/m2
Upward
Downward
Mandatory
Qh
Sensible heat flux
Sensible energy, averaged over a grid cell
W/m2
Upward
Downward
Mandatory
Qg
Ground heat flux
Heat flux into the ground, averaged over a grid cell
W/m2
Downward
Upward
Mandatory
Qf
Energy of fusion
Energy consumed or released during liquid/solid phase changes.
W/m2
Solid to Liquid
Liquid to Solid
Recommended
Qv
Energy of sublimation
Energy consumed or released during vapor/solid phase changes.
W/m2
Solid to Vapor
Vapor to Solid
Optional
Qtau
Momentum flux
module of the momentum lost by the atmosphere to the surface.
N/m2
Downward
Downward
Recommended
Qa
Advective energy
Heat transferred to a snow cover by rain..
W/m2
Downward
Downward
Optional
DelSurfHeat
Change in surface heat storage
Change in heat storage over the soil layer and the vegetation for which the energy balance is calculated, accumulated over the sampling time interval.
J/m2
Increase
Increase
Recommended
DelColdCont
Change in snow cold content
Change in cold content over the snow layer for which the energy balance is calculated, accumulated over the sampling time interval.
J/m2
Increase
Increase
Recommended

O.2) General water balance components:

(Expected range)

Variable
Description
Definition
Units
Positive Dir. (Traditional)
Positive Dir. (Mathematical)
Priority
Snowf
Snowfall rate
Average of the total snowfall over a time step and grid cell.
kg/m2s
Downward
Downward
Mandatory
Rainf
Rainfall rate
Average of the total rainfall over a time step and grid cell.
kg/m2s
Downward
Downward
Mandatory
Evap
Total Evapotranspiration
Sum of all evaporation sources, averaged over a grid cell
kg/m2s
Upward
Downward
Mandatory
Qs
Surface runoff
Runoff from the landsurface and/or subsurface stormflow
kg/m2s
Out of gridcell
Into gridcell
Mandatory
Qrec
Recharge
Recharge from river to the flood plain
kg/m2s
Into gridcell
Out of gridcell
Optional
Qsb
Subsurface runoff
Gravity drainage and/or slow response lateral flow. Ground water recharge will have the opposite sign.
kg/m2s
Out of gridcell
Into gridcell
Mandatory
Qsm
Snowmelt
Average liquid water generated from solid to liquid phase change in the snow.
kg/m2s
Solid to liquid
Solid to liquid
Mandatory
Qfz
Re-freezing of water in the snow
Average liquid water re-frozen in the snow pack.
kg/m2s
Liquid to solid
Liquid to solid
Mandatory
Qst
Snow throughfall
Liquid water flowing out of the snow pack.
kg/m2s
-
-
Recommended
DelSoilMoist
Change in soil moisture
Change in the simulated vertically integrated soil water volume, averaged over a grid cell, accumulated over the sampling time interval.
kg/m2
Increase
Increase
Mandatory
DelSWE
Change in snow water equivalent
Change in the total liquid water content of the snowpack, averaged over a grid, accumulated over the sampling time interval.
kg/m2
Increase
Increase
Mandatory
DelSurfStor
Change in Surface Water Storage
Change in vertically integrated liquid water storage, other than soil, snow or interception (lake, depression and river channel etc.), accumulated over the sampling time interval.
kg/m2
Increase
Increase
Recommended
DelIntercept
Change in interception storage
Change in the total liquid water storage in the canopy, accumulated over the sampling time interval.
kg/m2
Increase
Increase
Recommended

O.3)Surface state variables:

(Expected range)

Variable
Description
Definition
Units
Positive Dir. (Traditional)
Positive Dir. (Mathematical)
Priority
SnowT
Snow Surface Temperature
Temperature of the snow surface as it interacts with the atmosphere, averaged over a grid cell.
K
-
-
Mandatory
VegT
Vegetation Canopy Temperature
Vegetation temperature, averaged over all vegetation types
K
-
-
Mandatory
BaresoilT
Temperature of bare soil
Surface bare soil temperature
K
-
-
Mandatory
AvgSurfT
Average surface temperature
Average of all vegetation, bare soil and snow skin temperatures
K
-
-
Mandatory
RadT
Surface Radiative Temperature
Effective radiative surface temperature, averaged over the grid cell
K
-
-
Mandatory
Albedo
Surface Albedo
Grid cell average albedo for all wavelengths.
-
-
-
Mandatory
SWE
Snow Water Equivalent
Total water mass of the snowpack (liquid or frozen), averaged over a grid cell. 3D variable for multi-layer snow schemes.
kg/m2
-
-
Mandatory
SurfStor
Surface Water Storage
Total liquid water storage, other than soil, snow or interception storage (i.e. lakes, river channel or depression storage).
kg/m2
-
-
Mandatory

O.4)Subsurface State Variables

(Expected range)

Variable
Description
Definition
Units
Positive Dir. (Traditional)
Positive Dir. (Mathematical)
Priority
SoilMoist
Average layer soil moisture
Soil water content in each user-defined soil layer (3D variable). Includes the liquid, vapor and solid phases of water in the soil.
kg/m2
-
-
Mandatory
SoilTemp
Average layer soil temperature
Average soil temperature in each user-defined soil layer (3D variable)
K
-
-
Recommended
SMLiqFrac
Average layer fraction of liquid moisture
Fraction of soil moisture mass in the liquid phase in each user-defined soil layer (3D variable)
-
-
-
Optional
SMFrozFrac
Average layer fraction of frozen moisture
Fraction of soil moisture mass in the solid phase in each user-defined soil layer (3D variable)
-
-
-
Optional
SoilWet
Total Soil Wetness
Vertically integrated soil moisture divided by maximum allowable soil moisture above wilting point.
-
-
-
Mandatory

O.5)Evaporation components:

(Expected range)

Variable
Description
Definition
Units
Positive Dir. (Traditional)
Positive Dir. (Mathematical)
Priority
PotEvap
Potential Evapotranspiration
The flux as computed for evapotranspiration but will all resistances set to zero, except the aerodynamic resistance.
kg/m2s
Upward
Downward
Recommended
ECanop
Interception evaporation
Evaporation from canopy interception, averaged over all vegetation types within a grid cell.
kg/m2s
Upward
Downward
Recommended
TVeg
Vegetation transpiration
Transpiration from canopy, averaged over all vegetation types within a grid cell.
kg/m2s
Upward
Downward
Mandatory
ESoil
Bare soil evaporation
Evaporation from bare soil.
kg/m2s
Upward
Downward
Mandatory
EWater
Open water evaporation
Evaporation from surface water storage.
kg/m2s
Upward
Downward
Recommended
RootMoist
Root zone soil moisture
Total simulated soil moisture available for evapotranspiration.
kg/m2
-
-
Mandatory
CanopInt
Total canopy water storage
Total canopy interception, averaged over all vegetation types within a grid cell.
kg/m2
-
-
Recommended
EvapSnow
Snow Evaporation
Evaporation of liquid water in the snow pack.
kg/m2s
-
-
Recommended
SubSnow
Snow sublimation
Total sublimation from the ground snow pack.
kg/m2s
-
-
Recommended
SubSurf
Sublimation of the snow free area
Sublimation of the frozen water on the vegetation or in the soil.
kg/m2s
-
-
Recommended
ACond
Aerodynamic conductance
Aerodynamic conductance to vapor transport, averaged over all vegetation types within the grid cell.
m/s
-
-
Mandatory

O.6)Other Hydrologic Variables:

(Expected range)

Variable
Description
Definition
Units
Positive Dir. (Traditional)
Positive Dir. (Mathematical)
Priority
Dis
Simulated River Discharge
Simulated river discharge at specified point locations within the grid.
m3/s
-
-
Optional
WaterTableD
Water table depth
Depth of the water table if it is considered by the land-surface scheme.
m
-
-
Optional

O.7)Cold Season Processes:

(Expected range)

Variable
Description
Definition
Units
Positive Dir. (Traditional)
Positive Dir. (Mathematical)
Priority
SnowFrac
Snow covered fraction
Grid cell snow covered fraction
-
-
-
Optional
RainfSnowFrac
Fraction of rainfall on snow.
The fraction of the grid averaged rainfall which falls on the snow pack
-
-
-
Optional
SnowfSnowFrac
Fraction of snowfall on snow.
The fraction of the snowfall which falls on the snow pack
-
-
-
Optional
IceFrac
Ice-covered fraction
The fraction of the grid cell covered by sea-ice
-
-
-
Optional
IceT
Sea-ice thickness
The thickness of the ice layer on simulated water areas.
m
-
-
Optional
Fdepth
Frozen soil depth
Depth from surface to the first zero degree isotherm. Above this isotherm T < 0o, and below this line T > 0o.
m
Downward
Downward
Optional
Tdepth
Depth to soil thaw
Depth from surface to the zero degree isotherm. Above this isotherm T > 0o, and below this line T < 0o.
m
Downward
Downward
Optional
SAlbedo
Snow albedo
Albedo of the snow-covered surface, averaged over the grid cell.
-
-
-
Recommended
SnowTProf
Temperature profile in the snow
Temperature in the snow pack present in the grid-cell. 3D variable for multi-layer snow schemes.
K
-
-
Recommended
SnowDepth
Depth of snow layer
Depth of each layer of snow is a 3D variable for multi-layer snow schemes and the total snow depth for simpler models.
m
-
-
Recommended
SliqFrac
Snow liquid fraction
Fraction of Snow Equivalent Water which is in the liquid phase. 3D variable for multi-layer snow schemes.
-
-
-
Recommended

O.8)Variables to be compared with remote sensed data :

(Expected range)

Variable
Description
Definition
Units
Positive Dir. (Traditional)
Positive Dir. (Mathematical)
Priority
LWup
Upward long-wave broadband radiation
This upward longwave flux is to be compared to an ISCCP derived product.
W/m2
Upward
Upward
Recommended
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