Is annual rainfall a linear function?

Answer 1

Yes. In very simple terms, linear means line or set measurements on a single plain such as inches or centimetres on a ruler.

Rain falls into an opening which is generally larger than the collection device. This measurement is amplified in proportion to the difference in the size of the top opening to the collection and measurement container below. If the Top was 2" wide and the collection at the bottom was only 1" wide, then 1" of rainfall would be 4" in actual depth in the collection part. This is basic mathematics more easily shown by a square of 1" on all sides. Put another 1" square next to it and you have doubled it's size, but it is now a rectangle. You will need another 2 x 1" squares to make it square again. That makes 4 x 1" squares to make it 2" on all sides. It is now 4 times larger.

That's how rain is measured and calculated in linear.