04. Cloud cover and Rainfall
Look at this photograph showing dark clouds looming over an area in Singapore
What do you think will happen next?
Which is the wettest area in Singapore in 2013? Why do you think this part of Singapore receive higher amount of rainfall?
Watch this video clip on how convectional rain is formed and learn how to draw an annotated diagram to show its formation.
Reminder - condition for the formation of convectional rain is the high temperatures which heat up the ground. Thus it is common in tropical areas and summer in temperate areas.
Watch this video clip on how relief rain is formed and learn how to draw an annotated diagram to show its formation.
Relief rain is also known as orographic rain.
Reminder - condition for the formation of relief rain is that there must be a mountain barrier and onshore wind carrying moisture/ wind blowing from the sea.
How is data on rainfall collected?
Rain is collected using a rain gauge. It is partially sank into the ground with 30cm protruding above the ground so that it does not topple when the rain is heavy. The funnel direct the rain into the glass bottle where the rain will be collected and pour into a measuring cylinder every 24 hour and the amount collected is recorded. The rain gauge must be sited in an open field away from trees and buildings so that there is no blockage to the rain. It should not be sited on concrete ground as the water will bounce back from the concrete into the funnel.
The rain gauge which your teacher showed you is a bit different in that it is attached to a fence.
The rain gauge is transparent and you can read the amount collected.
