Question

why do you think the glass measuring cylinder of the rain gauge is inside or outside container?;​

Answer 1

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Insulation. It’s supposed to be protected from sunlight to prevent evaporation affecting results on hot days/low precipitation.

Additionally I’ve run into a couple of occasions when it’s rained so hard the inner container has overflowed and the contents of the outer container has had to be poured back in to get the actual rainfall (measure inner, pour out, refill from overflow, measure again, add together). That’s why the outer container is a container and not just a shield.