Nodes of different colours represent the following:
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descended from. Dashed arrows point from a module or program unit to
modules which it uses.
collision efficiency for rain collecting cloud water from Beard and Grover (1974)
if a/A < 0.25
https://doi.org/10.1175/1520-0469(1974)031<0543:NCEFSR>2.0.CO;2
otherwise uses polynomials to get close match of Pruppacher and Klett Fig. 14-9
Nodes of different colours represent the following:
Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.