Protocol 2008


This round (2008) of intercomparisons will be done without major human impacts (e.g. dams, irrigation). The plan is to include the human impacts in the next rounds. The focus of the model intercomparison project in 2008 is the differences in model physics.

 

Spatial resolution and land mask

The spatial resolution for this model intercomparison is 0.5 degrees latitude by longitude, and the land areas of the globe (excluding Antarctica) should be covered. The grid cell midpoints should be located at .25 and .75 latitude/longitude. A standardized land mask should be used by all models. The land mask is provided by Work Block 1 of the Watch project and can be obtained from the Watch ftp site.

 

Model periods

1980 – 1999:     - first 5 years (1980-1984) should be used as spin-up

- the last 15 years (1985-1999) should be reported

 

Atmospheric forcings

The forcing data can be found at the Watch ftp site. Time period: 1980-1999. The forcing data are provided at 6 hr and daily temporal resolutions, including the following variables at each resolution:

·          Temporal resolution: 6 hours.

o    Variables included: Precipitation (snowfall and rainfall), air temperature, shortwave and longwave radiation (downward component), air specific humidity, wind speed, and surface pressure.

·          Temporal resolution: 1 day

o    Variables included: Precipitation (snowfall, rainfall and total), air temperature, wind, net longwave radiation (calculated from downward radiation, based on air temperature), downward shortwave radiation, relative humidity, and vapour pressure.

The forcing data of the 2008 runs are NCC data (Ngo-Duc et al., 2005) regridded (not interpolated) from 1 degree to 0.5 degree spatial resolution.

Ngo-Duc, T., Polcher, J. and Laval, K, 2005, A 53-year forcing data set for land surface models, J. Geophys. Res. 110, D06116, doi:10.1029/2004JD005434.

 

 

Elevation, land use/cover, soil information

Each model will use their “own” elevation, land use/cover and soil information. Land use/cover information, especially LAI data, should be reported when submitting the data.


 

Routing network

The provided DDM30 routing network, which is mapped to the land mask, should be used by all modelling groups. The network includes flow direction, slope, and basin numbers, and is available on the Watch ftp site. The routing network includes large lakes not included in the provided land mask. These cells should not be included when results are submitted, though, and there should be no runoff added to the river network from these cells. I.e. these cells are included only for transportation purposes (streamflow).

 

 

Data format and data convention

NetCDF is the chosen data format both for the input data and the output data. A good source of documentation on the netCDF format can be found at http://www.unidata.ucar.edu/software/netcdf/. The online user manual is filled with example code blocks. Also, Jan Polcher has written and assembled some general software for reading and writing netCDF format (see http://www.lmd.jussieu.fr/~polcher/ALMA/alma_bazar.html). The ALMA data exchange convention (http://www.lmd.jussieu.fr/~polcher/ALMA/), which has been used in e.g. PILPS and GSWP projects, will be used.

 

Output data

All the requested output variables (see Table 1) should be submitted as fields (gridded values) of monthly means for each simulation run (15 years of 12 monthly values, in total 180 values for each grid cell and output variable) for land points and ocean points from -56 to 84 degrees latitude, and from -180 to 180 degrees longitude, i.e. 280 rows and 720 cols, or 201600 grid cells totally. Ocean points should be included because it makes visualizing the netCDF files easier. The variable names and units are to follow the ALMA protocol (http://www.lmd.jussieu.fr/~polcher/ALMA).

In addition, gridded fields of daily values should be submitted for water balance variables for the period 1987-1988, see also Table 1.

Gridded fields of water state variables (SWE, SoilMoist, GroundMoist, SurfStor) at the beginning and end of the reporting period should also be submitted, so that long-term water balance can be calculated as follows:

Precip = Qs + Qsb + Evap + Δ(SWE, SoilMoist, GroundMoist, SurfStor)

 

See submenu “Data submission” for specific information on the format of the submitted files, and file naming convention.

 

Table 1: Requested model output variables (see http://www.lmd.jussieu.fr/~polcher/ALMA for a more detailed description of the variables):

 Variable  Description  Mandatory  Monthly (1985-1999)  Daily (1987-1988) 
 Precip1  Precipitation rate

 X

 X

  
 Snowf  Snowfall

 X

 X

 X

 Evap  Total evapotranspiration

 X

 X

 X

 Qs  Surface runoff

 X

 X

 X

 Qsb  Subsurface runoff

 X

 X

 X

 SoilMoist2  Soil moisture

 X

 X

 X

 RootMoist  Root zone soil moisture

 X

 X

  
 RootSoilStress3  Root zone soil stress

 X

 X

  
 SWE  Snow water equivalent

 X

 X

 X

 SnowFrac  Snow covered fraction

 X

 X

  
 Dis  Simulated river discharge  

 X

 X

 ECanop  Interception evaporation  

 X

 X

 TVeg  Vegetation transpiration  

 X

 X

 ESoil  Bare soil evaporation  

 X

 X

 EWater  Open water evaporation  

 X

 X

 ESSNow4  Snow evaporation and sublimation  

 X

 X

 SurfStor  Surface water storage  

 X

 X

 GroundMoist5  Groundwater  

 X

 X

 PotEvap  Potential evapotranspiration

 X
 Qrec  Recharge to the flood plain

 X
 Qst  Snow throughfall

 X
 Albedo  Surface albedo

 X
 SAlbedo  Snow albedo

 X
 WaterTableD  Water table depth

 X
 SWnet  Net shortwave radiation

 X
 LWnet  Net longwave radiation

 X
 Qle  Latent heat

 X
 Qh  Sensible heat

 X
 Qg  Ground heat

 X
 SurfHeat  Surface heat storage   

 X

 

1: We suggest adding the standard ALMA Snowf and Rainf, i.e. Precip = Snowf + Rainf

2: We ask for total soil moisture, and not one for each soil layer.

3: RootSoilStress is not included in the ALMA convention. We define it as: (Simulated root zone soil moisture – Wilting point) / (Critical soil moisture – Wilting point)

4: We suggest adding the standard ALMA EvapSnow and SubSnow, i.e. ESSnow = EvapSnow + SubSnow

5: GroundMoist is not included in the ALMA convention. We define it as total ground water content (units: kg m-2)