I’ve been thinking about rain gauge accuracy.
In calm weather, the rain gauge will sample a column of air and water directly above it; a column of air and water exactly the diameter of the rain gauge. That’s our baseline accuracy.
But what happens when the rain is not coming straight down? What happens to the accuracy when there is wind with the rain? If you imagine a column the same diameter as the top of the rain gauge, and slice it off perpendicularly, you’ll have a surface area on the end of the column exactly equal to the surface area of the top of the rain gauge. If you cut that column of air off diagonally though, indicating the rain striking the top of the rain gauge at an angle, you’ll increase the surface area of the face; the part that intersects the top of the rain gauge. For the same amount of rain, you’ll collect more rain than if the rain were coming straight down!
But then, if it rains too hard sideways you won’t get any rain in the rain gauge at all, it will just blow straight across the top. Probably, after a certain point, you get decreasing amounts of water in the gauge as more blows across, so my column of water analogy doesn’t hold up. The surface area on the face of a column of water would continue to increase, the more acutely you cut across it, to almost infinity, before it suddenly went to zero when the angle went to zero.
Guess I’d better think about something else ….., like maybe how to make perfectly clear ice-cubes in a home refrigerator.
