This directory contains an alternative to glint that can be used when a GCM
passes already-downscaled fields: glad (where the "a.d." stands for "already
downscaled"). glad acts as a lightweight layer between the GCM and the rest of
CISM. It is responsible for:

(1) Handling time stepping and temporal averaging

(2) Providing a simpler interface to the climate model, rather than requiring
the climate model to make detailed calls to things like glide_tstep_p1, etc.

(3) Translating inputs and outputs into appropriate quantities

Eventually, it is possible that this layer could be removed, moving some of its
functionality up into the GLC layer of CESM/ACME, and some of its functionality
down into the rest of the CISM code. However, we may choose to keep this
lightweight layer in place, because it does have some value.

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The main differences between the code here and the code in libglint are:

(1) libglad does not do any upscaling / downscaling / interpolation

(2) libglad currently only works with SMB inputs - not PDD, etc.

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Note that a few modules here are also used by libglint, including:

- glad_constants.F90

- glad_restart_gcm.F90

So those may contain a bit of code that is needed by libglint but not by
libglad.