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Module smb_simple

This IGM module models a simple surface mass balance (SMB) parametrized by time-evolving equilibrium line altitude (ELA) \(z_{ELA}\), ablation gradient \(\beta_{abl}\), accumulation gradient \(\beta_{acc}\), and maximum accumulation \(m_{acc}\) parameters:

\[SMB(z) = \begin{cases} \min(\beta_{acc} \cdot (z - z_{ELA}), m_{acc}) & \text{if } z > z_{ELA}, \\ \beta_{abl} \cdot (z - z_{ELA}) & \text{otherwise}. \end{cases}\]

These parameters can be provided in a file (specified by the file parameter) with the following format:

time   gradabl  gradacc    ela   accmax
1900     0.009    0.005   2800      2.0
2000     0.009    0.005   2900      2.0
2100     0.009    0.005   3300      2.0

Alternatively, they can be directly specified in the configuration file params.yaml as follows:

smb_simple:
  array: 
    - ["time", "gradabl", "gradacc", "ela", "accmax"]
    - [ 1900,      0.009,     0.005,  2800,      2.0]
    - [ 2000,      0.009,     0.005,  2900,      2.0]
    - [ 2100,      0.009,     0.005,  3300,      2.0]

If the array parameter is set to an empty list [], the module will read the data from the file specified by the file parameter. Otherwise, it will use the provided array (a list of lists).

The module computes the surface mass balance at a frequency defined by the update_freq parameter (default is 1 year) and interpolates the four parameters linearly over time.

If an "icemask" field is provided as input, the module will assign a negative surface mass balance (-10 m/y) to areas where a positive surface mass balance would otherwise occur outside the mask. This prevents overflow into neighboring catchments.

Contributors: G. Jouvet.

Parameters

Default configuration file (smb_simple.yaml): 

smb_simple:
  update_freq: 1.0
  file: param.txt
  array: []

Description of the parameters:

Name Description Default value Units
update_freq Update the mass balance each X years. 1.0 y
file Name of the input file for the simple mass balance model (time, gradabl, gradacc, ela, accmax). param.txt —
array Time dependent parameters for simple mass balance model (time, gradabl, gradacc, ela, accmax). [] —