Precipitation is caused when moist air rises, water vapour in the air cools and condenses to forms clouds.
Air cools upwards through the atmosphere because temperature falls with altitude because the Earth’s atmosphere is heated from the Earth’s surface up over.
When the water droplets in clouds grow to a certain size, gravity causes them to fall because of their own weight. Water droplet will fall as rainwater or precipitation.
Three main types of precipitation
Convectional rainfall is more common in Brunei. It occurs in areas with hot, humid climates like equatorial regions.
This type of rain happens when the earth gets so hot that the warm air mass above it rises.
The air cools, condenses and cumulonimbus clouds form.
Heavy rainfall with thunder and lightning follows.
Relief rainfall occurs where the air over the sea moves over the land and is forced to rise over hills or a mountain range.
This air cools, condenses and forms clouds – the result is rain.
As the air descends the mountain on the other side, it warms and sinks.
Much less rain occurs on this side of the mountain. (Rainshadow)
This rain occurs when a warm air mass meets a cool air mass.
The warm air mass is forced to rise over the cold air mass.
When the warm air rises it cools, condenses and forms rain clouds.