Data Format

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 files are to be submitted in compressed formats. Please use the Linux/UNIX compress or gzip (GNU zip) to compress the output files. For those using Windows, WinZip is also acceptable.

File array structure and variable naming convention 
One file should include only one variable when submitting the data. Use only lowercase letters in the file names, since some netCDF viewers only accept lowercase letters in their filenames. Data are to be submitted for the area -56 to 84 degrees latitude, and from -180 to 180 degrees longitude, i.e. 280 rows and 720 cols, or 201600 grid cells totally. Write the outputs row-wise starting at -55.75 and -179.75, and ending at 83.75 and 179.75.

Naming convention in netCDF:

  • x-dimension name: lon
  • x-dimension units: degrees_east
  • y-dimension name: lat
  • y-dimension units: degrees_north
  • t-dimension name: time
  • t-dimension units: months or days since yyyy-mm-dd (see protocol pages for exact information).
  • missing_value: 1.e+20f

Example of naming of variables:

  • Long field name: Total evapotranspiration (Use the ALMA variable description)
  • Short field name: Evap (Use the ALMA variable names)
  • Field units: kg/m2s (Use the ALMA variable units)

Data convention
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. The additional variables requested for the simulations with human impacts are listed and described in Table 2 below. 

Table 1: Convention for model output data. ALMA convention. Be aware that this list may include more variables than should be submitted. See "WaterMIP Protocol", "WB4 Extremes" or "WB6 Water Resources" for the list of variables that should be submitted for your modelling purpose. 

Variable Description  Definition 

Units 

 Positive dir.
Precip Precipitation rate

Average of the total precipitation (rainfall and snowfall) over a time step and grid cell, i.e. the standard ALMA Snowf and Rainf are added. 

 kg/m2s

Downward

Snowf Snowfall

Average of the total snowfall over a time step and grid cell

kg/m2s

Downward

Evap

Total evapotranspiration

Sum of all evaporation sources, averaged over a grid cell  

kg/m2s

Upward

Qs

Surface runoff

Runoff from the landsurface and/or subsurface stormflow. This variable should include the fast component of runoff response. This includes any surface runoff generated as infiltration excess runoff or saturation excess runoff (or the parameterized equivalent). In addition it should include any subsurface lateral quick-flow, which based on modelers experience is best routed as a fast storm-flow component, rather than a drainage or base-flow component.

kg/m2s

Out of gridcell

Qsb

Subsurface runoff

This variable should include the slow drainage component of runoff response. This includes gravity drainage and slow response lateral flow. Ground water recharge will have the opposite sign.

kg/m2s

Out of gridcell

Qrec Recharge to the flood plain Recharge from river to the flood plain. This variable represents streamflow which leaves the channel network and returns to the grid cell interface. The sign will always be opposite to that of surface runoff and the recharge quantity should not be subtracted from the surface runoff variable when recharge is specified.  kg/m2s Into gridcell

SoilMoist

Soil moisture

Soil water content in total soil layer (not one for each soil layer). Includes the liquid, vapor and solid phases of water in the soil.

kg/m2

- 

RootMoist

Root zone soil moisture

Total simulated soil moisture available for evapotranspiration. "Available water" means that frozen water should not be included, and water below wilting point should also be excluded.

kg/m2

- 

RootSoilStress

Root zone soil stress

RootMoist / (Critical soil moisture – Wilting point). Remember that RootMoist does not include frozen water or water below wilting point. Upper/lower limits should be set at 1/0.

-

- 

SWE

Snow water equivalent

Total water mass of the snowpack (liquid or frozen), averaged over a grid cell.

kg/m2

- 

SnowFrac

Snow covered fraction

Grid cell snow covered fraction  

- 

- 

Dis

Simulated river discharge

Simulated river discharge

m3/s

- 

ECanop

Interception evaporation

Evaporation from canopy interception, averaged over all vegetation types within a grid cell. 

kg/m2s 

Upward

TVeg

Vegetation transpiration

Transpiration from canopy, averaged over all vegetation types within a grid cell

kg/m2s 

Upward

ESoil

Bare soil evaporation

Evaporation from bare soil

kg/m2s 

Upward 

EWater

Open water evaporation

Evaporation from surface water storage

kg/m2s 

Upward 

ESSNow

Snow evaporation and sublimation

Total sublimation and evaporation from the snow pack, i.e. we ask for the sum of the standard ALMA EvapSnow and SubSnow, (ESSNow = EvapSnow + SubSnow). 

kg/m2s 

Upward 

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 

- 

GroundMoist

Groundwater

Total ground water content. This variable is not included in the ALMA convention. 

kg/m2 

- 

PotEvap

Potential evapotranspiration

The flux as computed for evapotranspiration but with all resistances set to zero, except the aerodynamic resistance. 

kg/m2s  

Upward 

Qst

Snow throughfall

Liquid water flowing out of the snow pack, meaning water (melted snow and/or rain) percolating through the snowpack.

kg/m2s  

- 

Albedo

Surface albedo

Grid cell average albedo for all wavelengths 

- 

- 

SAlbedo

Snow albedo

Albedo of the snow-covered surface, averaged over the grid cell 

-

- 

WaterTableD

Water table depth

Depth of the water table  

m 

- 

SWnet

Net shortwave radiation

Incoming solar radiation less the simulated outgoing shortwave radiation, averaged over a grid cell  

 W/m2

 

Downward

LWnet

Net longwave radiation

Incident longwave radiation less the simulated outgoing longwave radiation, averaged over a grid cell  

 W/m2

Downward 

Qle

Latent heat

Energy of evaporation, averaged over a grid cell  

 W/m2

Upward 

Qh

Sensible heat

Sensible energy, averaged over a grid cell  

 W/m2

Upward  

Qg

Ground heat

Heat flux into the ground, averaged over a grid cell  

 W/m2

Downward 

 

  

 

 

Table 2: Convention for model output data, water use terms. Be aware that this list may include more variables than should be submitted. See "WaterMIP Protocol" or "WB6 Water Resources" for the list of variables that should be submitted for your modelling purpose.

Variable Description 

Definition

     Units    
PIrrUse Potential irrigation water use 

Potential irrigation water use (water consumed), averaged over a gridcell 

kg/m2s

PIrrWW

Potential irrigation water withdrawals

Potential irrigation water withdrawn, averaged over a grid cell

kg/m2s

PEConv Potential irrigation conveyance losses Potential irrigation conveyance losses, averaged over a grid cell

kg/m2s

PReturnFlow Potential irrigation return flow Potential irrigation return flow, averaged over a gridcell

kg/m2s

AIrrUse

Actual irrigation water use

Actual irrigation water use (water consumed), averaged over a grid cell

kg/m2s

AIrrWW

Actual irrigation water withdrawals

 Actual irrigation water withdrawn, averaged over a grid cell

kg/m2s

AEConv Actual irrigation conveyance losses Actual irrigation conveyance losees, averaged over a grid cell   kg/m2s
AReturnFlow Actual irrigation return flow Actual irrigation return flow, averaged over a grid cell

kg/m2s

ADomWW

Actual domestic water withdrawals

Actual domestic water withdrawn, averaged over a grid cell

kg/m2s

ADomUse Actual domestic water use

Actual domestic water consumed, averaged over a grid cell 

kg/m2s

AManWW

Actual manufacturing water withdrawals

Actual water withdrawn for manufacturing, averaged over a grid cell 

kg/m2s

AManUse

Actual manufacturing water use

Actual water consumed, manufacturing, averaged over a grid cell

kg/m2s

AElecWW

Actual electricity water withdrawals

Actual water withdrawn for electricity production, averaged over a grid cell 

kg/m2s

AElecUse Actual electricity water use

Actual water consumed, electricity production, averaged over a grid cell 

kg/m2s

ALiveWW

Actual livestock water withdrawals

Actual water withdrawn for livestock farming, averaged over a grid cell 

kg/m2s

ALiveUse

Actual livestock water use

Actual water consumed, livestock farming, averaged over a grid cell

kg/m2s

ResStor Reservoir storage

 

m3

ResRel Reservoir release

m3/s

   

 

  

Table 3: Convention for model output data, blue/green water terms. This list is for those submitting results for the blue/green water initiative. If you do not know what the blue/green water initiative is, you can ignore this Table,  or, if you are interested, contact Jens Heinke and/or Holger Hoff (see Contacts information).

Variable Description 

Definition

     Units    
IrrigCropUseGreen

Green water use (water consumed) on irrigated cropland

Sum of evaporative fluxes (TVeg + ECanop + ESoil) from rain water over irrigated cropland, averaged over a grid cell. Fallow period should also be included.

kg/m2s

RainfCropUseGreen

Green water use (water consumed) on rainfed cropland

Sum of evaporative fluxes (TVeg + ECanop + ESoil) from rain water over rainfed (non-irrigated) cropland , averaged over a grid cell. Fallow period should also be included.

kg/m2s

PastureUseGreen

Green water use (water consumed) on pasture

Sum of evaporative fluxes (TVeg + ECanop + ESoil) from rain water over pasture, averaged over a grid cell.

kg/m2s