thard-choices.rst - pism - [fork] customized build of PISM, the parallel ice sheet model (tillflux branch)
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       thard-choices.rst (1903B)
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            1 .. include:: ../../global.txt
            2 
            3 .. _sec-hard-choices:
            4 
            5 Dealing with more difficult modeling choices
            6 --------------------------------------------
            7 
            8 Most uses of an ice sheet model depend on careful modeling choices in situations where
            9 there are considerable uncertainties *and* the model results depend strongly on those
           10 choices. There may be, at the present state of knowledge, *no clear default values* that
           11 PISM can provide. Furthermore, the available PISM options and sub-models are known to
           12 *not* be sufficient for all users. Thus there are modelling situations for which we know
           13 the user may have to do a great deal more hard work than just choose among PISM runtime
           14 options.
           15 
           16 Here are example cases where users have worked hard:
           17 
           18 - User made use of available data in order to choose parameters for existing PISM models.
           19   These parameters then override PISM defaults.
           20 
           21   .. admonition:: Example
           22      :class: note
           23 
           24      Use regional atmosphere model output to identify PDD parameters suitable for modeling
           25      surface mass balance on a particular ice sheet. Then supply these parameters to PISM
           26      by a ``-config_override`` file.
           27 
           28      .. our UAF current situation with Greenland
           29 
           30 - User wrote code, including code which modified current PISM internals, either to add
           31   additional processes or to "correct" PISM default process models.
           32 
           33   .. admonition:: Example
           34      :class: note
           35 
           36      Add a new sub-ice-shelf melt model by modifying C++ code in the ``src/coupler/``
           37      directory.
           38 
           39      .. PIK ocean models
           40 
           41 - User simplified the model in use, instead of the default which was more elaborate.
           42 
           43   .. admonition:: Example
           44      :class: note
           45 
           46      Instead of using the PISM default mechanism connecting basal melt rate and basal
           47      strength, bypass this mechanism by generating a map of yield stress ``tauc`` directly
           48      and supplying it as input.
           49 
           50      .. Nick's -yield_stress constant choice