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 :

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 < 0^o, and below this line T > 0^o.	m	Downward	Downward	Optional
Tdepth	Depth to soil thaw	Depth from surface to the zero degree isotherm. Above this isotherm T > 0^o, and below this line T < 0^o.	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