Question

After the rain of 12th June 2017, an ecologist measured a volume of 1414cm³ of rain water from 0 rain gauge with a funnel diameter of 24cm. Calculate the mm of rain that fell that day

Answer 1

Rainfall is measured as depth on the surface of the Earth, typically in mm. We know the volume of water in the rain gauge: 1414 cubic centimetres. We know need to know the area of the Earth that this volume fell on. This would be the area of the funnel opening that points up to the sky to catch the rain. We know the diameter is 24 cm. So we need to determine the area of a circle with a diameter of 24 cm. The equation to use is: area = pi * radius^2. Since the radius of a circle is half the diameter, the equation is:

So area is 3.14159 * 12^2

= 452.39 cm^2
Volume = depth * area
depth = volume/area
depth = 1414/452.39
= 3.13 cm = 31.3 mm