Iterating over a dictionary in a for loop - checking code has worked

[ndc85430]

I expect many here aren't going to be familiar with whichever field this is (atmospheric physics?) and are likely to find it difficult to know what your code is doing. Is it possible to formulate the problem you have in terms of an input and an expected output (into and from a function, say)? That way, you could at least write a unit test to verify that given that input, the output is what you expect.