OGGM Mass-Balance sandbox

Next generation of OGGM's mass-balance models. Work in process!

You are welcome to discover already some new mass-balance options such as different climate resolutions or surface type distinction. However, we want to make clear that this is work in process and is part of my PhD project:

• the new mass-balance module from this sandbox is of course less stable, less robust, slower and less documented than the default MBmodel (i.e. the PastMassBalance class in OGGM)
• it has no pre-mass-balance-calibrated gdirs
• although I try to include tests as I can, they might be less rigorous as the ones from pure OGGM
• there is not yet any publication that has used it!

If you can't wait until it is integrated into OGGM default and want to use it already now for your specific OGGM application, please contact me first either by:

• opening an issue
• writing an e-mail to me (Lilian Schuster)
• or, the easiest way, discuss it inside of our OGGM slack channel

---

At the moment these options of climate resolution are available inside TIModel:

• to compute degree days:
  • using monthly temperatures ('mb_monthly'), default option in OGGM
  • using monthly temperatures and daily temp std to generate daily temp. assuming normal distributed data ('mb_pseudo_daily')
  • using daily temperatures ('mb_real_daily')
• temperature lapse rates:
  • using a constant calibrated value independent of location and season (-6.5 K/km, grad_type: cte), default option in OGGM
  • using lapse rates from ERA5 that vary throughout the year and inbetween glacier locations, but that are constant inbetween the years (grad_type: 'var_an_cycle')
  • ( this has not been tested: using lapse rates from ERA5 that vary throughout the year and inbetween glacier locations, different for each year (grad_type: 'var') )

In addition, a surface type distinction model is included with a bucket system together with a melt_f that varies with age inside of TIModel_Sfc_Type:

• there are two options included at the moment:

  • melt_f_update=annual
    • If annual, then it uses 1 snow and 5 firn buckets with yearly melt factor updates.
  • melt_f_update=monthly:
    • If monthly, each month the snow is ageing over 6 years (i.e., 72 months -> 72 buckets).
  • the ice bucket is thought as an "infinite" bucket (because we do not know the ice thickness at this model stage)
  • Melt factors are interpolated linearly inbetween the buckets. TODO: include non-linear melt factor change as an option!

• default is to use a spinup of 5 years. So to compute the specific mass balance between 2000 and 2020, with spinup=True, the annual mb is computed since 1994 where at first everything is ice, and then it accumulates over the next years, so that in 2000 there is something in each bucket ...

• the ratio of snow melt factor to ice melt factor is set to 0.5 (as in GloGEM, PyGEM, ...) but it can be changed via melt_f_ratio_snow_to_ice

  • if we set melt_f_ratio_snow_to_ice=1 the melt factor is equal for all buckets, hence the results are equal to no surface type distinction (as in TIModel)

• get_annual_mb and get_monthly_mb work as in PastMassBalance, however they only accept the height array that corresponds to the inversion height (so no mass-balance elevation feedback can be included at the moment!)

  • that means the given mass-balance ist the mass-balance over the inversion heights (before doing the inversion and so on)

• the buckets are automatically updated when using get_annual_mb or get_monthly_mb via the TIModel_Sfc_Type.pd_bucket dataframe

• to make sure that we do not compute mass-balance twice and to always have a spin-up of 6 years, we save the mass balance under

  • get_annual_mb.pd_mb_annual: for each year
    • when using get_monthly_mb for several years, after computing the December month, the pd_mb_annual dataframe is updated
  • get_annual_mb.pd_mb_monthly: for each month
    • note that this stays empty if we only use get_annual_mb with annual melt_f_update

All options have been tested with the elevation flowline from Huss.

How to install!

the newest OGGM developer version has to be installed in order that MBsandbox works: e.g. do:

$ conda create --name env_mb
$ source activate env_mb
$ git clone  https://github.com/OGGM/oggm.git
$ cd oggm 
$ pip install -e .
$ git clone https://github.com/OGGM/massbalance-sandbox
$ cd massbalance-sandbox
$ pip install -e .

Test the installation via pytest while being in the massbalance-sandbox folder:

$ pytest .

The MBsandbox package can be imported in python by

>>> import MBsandbox

code inside of MBsandbox

• mbmod_daily_oneflowline.py:
  • process different climate data (WFDE5_CRU, ERA5_daily, W5E5, W5E5_MSWEP(prcp from MSWEP, temp. from W5E5)),
  • new mass-balance model TIModel_Parent with children TIModel and TIModel_Sfc_Type
• flowline_TIModel.py: copies of run_from_climate, run_random_climate that are compatible with TIModel, not yet tested for TIModel_Sfc_Type
• help_func.py: helper functions to minimize the bias, optimise standard deviation quotient for reference glaciers, to calibrate the melt factor given the precipitation factor and geodetic observations, and to compute performance statistics
• tests: tests for different functions
• wip: work in process folder without documentation

How to use!

This is still work in process but there are some example notebooks with explanations inside of the docs folder:

• how_to_use.ipynb : simple use case that shows how to use different climate resolutions

• surface_type_distinction/oggm_sfc_type_bucket.ipynb : use case of how the surface type distinction with different melt factors works

  • inside of the folder surface_type_distinction there are some plots that show how the sfc type distinction and melt_f variation works

• how_to_daily_input_daily_output.ipynb : how to get daily mb output and calibrate with geodetic data

• hydro_compatility/hydro_compatibility_workflow.ipynb : use case of how to use MBsandbox with run_with_hydro (works for W5E5, WFDE5_CRU and W5E5_MSWEP climate)

other notebooks not directly related to MBSandbox:

• template_geodetic_MB_calibration.ipynb : template how to calibrate a glacier by using the geodetic estimates (for the default PastMassBalanceModel of OGGM )

• preprocess_ERA5_daily/cluster_aggregate_dailyERA5.ipynb : how to preprocess the ERA5_daily files (end product is here: https://cluster.klima.uni-bremen.de/~oggm/climate/era5/daily/v1.0/)

  • other preprocess / flattening workflows (for ISIMIP3a/3b, WFDE5, W5E5, MSWEP) are on the cluster (todo: upload them...?)

need to check if the following notebooks still work:

• intercomparison_w_figures/HEF_mb_type_intercomparison_oneflowline.ipynb : shows mb type intercomparison for Hintereisferner
  • plots in intercomparison_w_figures/figures_hef
• intercomparison_w_figures/refglaciersAlps_mb_type_intercomparison_oneflowline.ipynb : shows intercomparison for Alpine reference glaciers plots in:
  • intercomparison_w_figures/figures_alps (performance measures for Alpine reference glaciers)
  • intercomparison_w_figures/figures_alps_indiv (observed and modelled mb time series with performance measures for each Alpine reference glacier
  • intercomparison_w_figures/stats_Alps_6mb_models_N_5000_with_mean_an_cycle.csv : dataset of optimal DDFs and performance measures for all Alpine glaciers and all mb types