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Running a simulation

Running an Alpine3D simulation requires several steps:

  1. Getting and compiling Alpine3D
  2. Defining the simulation
  3. Preparing the input data
  4. Configuring the simulation
  5. Running the simulation
  6. Extracting the data of interest from the outputs

Please note that usually, you would do several iterations on the steps 2-6. The goal of this document is to describe these steps.

Getting and compiling Alpine3D

Please see Getting started.

Defining the simulation

Here, you have to define the very basic parameters of the simulation:

  • The domain
    • which geographic area
    • which features of the landscape you want to include
    • the contours of the area within the rectangular Digital Elevation Model
  • The time interval
    • what is the starting date (usually, you want to start without snow in the domain)
    • if some spin up would be necessary, this gives you the actual simulation starting date
    • what is the end date (do you need to wait until all snow is melted in the domain?)
  • The overall goal of the simulation
    • is about hydrology?
    • is about snow transport?
    • is about snow cover distribution?
  • The meteorological input data
    • will you provide points measurements or gridded data?
    • in case of climate scenario, which scenario do you want to use?

Once you have answered these very basic questions, you can move forward and start preparing the simulation.

Preparing the input data and files structure

Please have a look at the documentation or Input data preparation. The recommended simulation files structure is laid out in Input data preparation.

Please keep in mind that Alpine3D simulations MUST run with soil (the SNP_SOIL key will be forced to "true") and with canopy (the CANOPY key will be forced to "true").

Configuring the simulation

This is done by two means: by the io.ini configuration file and by some command line options.

The io.ini configuration file

This file is structured by sections, focused on several aspects:

  • General, for a few gerenal options
  • Input, for the configuration of the inputs
  • Output, for the configuration of the outputs
  • Snowpack, for the specific snowpack model configuration
  • SnowpackAdvanced, for some advanced Snowpack options, including the necessary ALPINE3D = true key
  • Interpolations1D, for the temporal interpolations configuration
  • Interpolations2D, for the spatial interpolations configuration

These sections are described in the meteoio and snowpack documentation.

It is recommended to use Inishell to generate a proper io.ini for alpine3d, before running Alpine3D in batch mode.

Command line options

You can get the list of supported options by running alpine3d --help. These options focus on which modules should be enabled (for example, snowdrift), the number of workers for the modules that have been parallelized (for example, 4 workers for ebalance) and the start and end date of the simulation.

Configuring the gridded outputs

The exact outputs are provided with the GRIDS_PARAMETERS in the [Output] section of the ini file.

If you need soe custom parameters to be written as grids, you can do it by editing the source code. Open the file "snowpackinterface/" and look for the writeOutput method. This is where you can create new outputs. It is also possible to edit "snowpackinterface/" and write in the custom grid any snowpack parameter (or any other computation), then to write it out from "snowpackinterface/".

Running the simulation

Several "standard" simulations are available to test that a given installation is properly working. These range from very small (like the Stillberg or Dorfberg simulations) to huge (Graubunden simulation). Both sequential and parallel runs can be done (keeping in mind that a large simulation might not have enough memory to run sequentially).

Sequential simulation

First, once Alpine3D has been properly compiled and "deployed", copy content of the Alpine3D "bin" subdirectory into the simulation's "bin" subdirectory. Then, go into the "setup" directory and edit the "": this is the script that controls the simulation. You can configure a parallel (or not parallel) simulation as well as the number of workers (that would run in parallel for a parallel simulation, thus reducing the total computing time or one after another in a sequential simulation). To start a simulation, simply run this script: ./ Since most simulations last for quite a while, it is usually a good idea to detach the simulation process by using nohup, thus modifying the command line to become nohup ./ &. Very often, the simulation will be managed by a batch system (in this case, please ask your system administrator for how to submit jobs to your batch system).

Extracting output data

The gridded outputs should all be in the output subdirectory, while the runoff outputs would be in output/runoff.