Few infos on SURFEX-Crocus simulations

The steps of a SURFEX-Crocus simulation are :
  1. PGD
  2. PREP

The PGD step is the definition of the physiography for the ground.
It uses specific files (eg ecoclimapI_covers_param.bin) which gives an ecosystem classification with a coherent set of land surface parameters. You can have more info about ecoclimap:

The PREP step is the definition of initial values for all model state variables (for soil, snow, etc.). You can either:
- use a file already produced by a previous simulation
- use a init_TG file providing initial ground temperatures). In that case, your simulation starts without snow on the ground.
- build an init_TG file from the air temperature climatology (computed from the meteorological forcing files)

The OFFLINE step is the simulation of the snow cover between the two dates of the simulation. It must have a meteorological file for that : the FORCING file.

Summary :
1) PGD = build physiography files (grid system, soil and vegetation properties, and all main parameters which are constant over time
2) PREP = build initial conditions for all model variables (e.g. all soil and snow state variables)
3) OFFLINE = compute evolution of the state variables (soil, snow, etc.) in offline mode (= forced by meteorological conditions).

What is needed to launch a SURFEX-Crocus simulation ?
- files to define the PGD (some of them are included in SURFEX package, some of them have to be downloaded from the SURFEX website: depending on your application)
- FORCING file for the near-surface meteorological conditions during the simulation.
- PREP file (or possibly create an init_TG file from the FORCING if you don’t have a PREP)
- two dates : begin of the simulation, end of the simulation
- namelist : a fortran ascii file which describes the physical options you want to apply for your simulation

How to launch a SURFEX-Crocus simulation ?
Snowtools is a library made for launching simulations, pre or post processing simulations, visualise simulations. The launching command is « s2m ». Info are in other pages of the wiki (eg Run a SURFEX-Crocus experiment without vortex)

How to manage initialization files in simulations :

NB : if you run a simulation in an already existing output directory (via the -o option), the simulation will use the PREP file available in output/prep folder. This is necessary to extend simulations in time, or to perform sensitivity analyses using identical initial conditions.

The initialisation of SURFEX state variables is associated with a date. So, the file is named

If you are starting a simulation with a file :
- the date should be consistent with the starting date of the simulation.
- the state of the soil / snow must be consistent with the options of your simulation. For example, if your file comes from a simulation without impurity, it can’t be used for a simulation with impurity. Similarly the PREP files must have been generated by a simulation using the same number of soil and snow layers than the incoming one.
- at the end of the simulation, the resulting state of the soil / snow properties for the ending date is written in another which can be used for a future simulation restarting at this date.

NB : When necessary, is possible to use a « false date » file to start a simulation (see Run a SURFEX-Crocus experiment without vortex)

What are the results of a local SURFEX-Crocus simulation :
After the first test, there is a folder named « output » (or another name if you change the -o option of the s2m command) which is created. This folder contains 5 subfolders:
  • meteo :
    for the meteorological FORCING. It is only used to save forcing files in cases they are modifie through the s2m command (e.g. geometry changes, etc.)
  • prep :
    for PGD and PREP files. After the simulation, it contains
    • the file
    • a file if there were no PREP file at the beginning of the simulation (this is the case for the first test)
    • a file : state of snow cover for starting date
    • a file : state of snow cover for ending date
  • pro :
    This folder contains the result of the simulation : file proving all simulation diagnostics for the whole simulation period.
    Output diagnostics should be defined in the namelist to adjust the output volume to what you really need (this is the CSELECT choice in the namelist).
Running directories
All computations are performed in dedicated running directories that you should not need to modify yourself or even access for regular simulations.
However, these directories can contain useful informations to understand the origin of unexpected bugs.
  • workClimxxxxxx
    This directory is used to compute soil initialization files based on air temperature climatology.
  • workSurfexxxxxx
    This directory is used for all the main computations of the simulation. It can be used to identify all input files used in an aborted or suspicous execution, as well as some log files produced by SURFEX useful to investigate bugs.
    Input files:
    • Ecoclimap files
    •, and files
      During the execution process, the files initially provided with dates (for PREP and FORCING) are renamed and with symbolic links as OFFLINE execution only opens '', '' and ''
    • Namelist : OPTIONS.nam
      Other output files (commonly not needed to be saved)
    • some log files : LISTING_PGD.txt, LISTING_PREP0.txt, ... if there is a simulation with several cores, the number is corresponding to the thread.
    • some OUT files * produced by SURFEX but not used in default simulations dedicated to snow cover.