RAINFALL 

Rain gauge is the instrument used to measure the amount of rainfall in a day.

It should be made of impermeable material which can’t absorb water.

How It’s Used/Works

• It’s taken to an open space to prevent water from dropping into the funnel.
• Its sunk into the ground to prevent evaporation
• The funnel top is left 30cm above the ground to prevent splashes of water and run off.
• After 24 hours water is emptied into the measuring cylinder.
• The reading of the amount of rainfall is got from the measuring cylinder in millimetres.
• The figure represents the millimetres of water falling on each square millimetre of the ground.
• It could be used to measure snow fall by melting it before the readings are gotten.

Calculating Rainfall

1. Monthly Rainfall Total

-Sum of rainfall recorded in a month.

2. Annual Rainfall Total

– Sum of monthly rainfall totals for 12 months.

3. Mean Monthly Rainfall

-Sum of rainfall totals for a particular month over several years divided by the number of the years of observation.

4. Mean Annual Rainfall

-Sum of mean monthly rainfall for 12 months of the year.