Scaling precipitation to FastScape

[jeanbraun]

Hello @benbovy. I made a modification to the orographic_precipitation FastScape extension such that flowacc is properly scaled. For this I introduced a rainfall_frequency input parameter that is the number of storm of 1 hour duration per day. Note that the flow accumulation routine multiplies the runoff (in mm/hr) by the cell area (in m^2) such that the resulting flowacc is in mm m^2/hr (and not in mm^3/hr as specified in the current version). Therefore in order to get the flowacc in m^3/yr as expected in the SPL, one needs to scale it by:
self.flowacc *= 8.76*self.rainfall_frequency
I have also modified the test by adding a parameter rainfall_frequency in the file fixture_orographic_precipitation.py that contains the input parameters.
Unfortunately I forgot to create a new branch and I think I have overwritten the master branch on the GitHub repo. Sorry...
Jean.

[benbovy]

Thanks @jeanbraun. I fixed a typo in e58dd04 (tests were failing).

Two comments / questions:

• I think we should move the rainfall_frequency variable to the OrographicDrainageDischarge process. It is currently declared in OrographicPrecipitation but it is not used in that process. Unless this parameter has potential to be used in other processes that depend on OrographicPrecipitation?

• Is there any good default value for it?