Rainfall

Question 1

What are all types of rainfall caused by?

Answer 1

All types of rainfall are cause by air being forced to rise

1. Air rises and cools
2. Cooler air cannot hold much moisture as it could when it was warmer
3. Air reaches 100% saturation (cannot hold any more water) - the dew point
4. Above the dew point, air begins to condensate (water vapour - a gas - that is held in the air is turned back into water droplets - a liquid)
5. Condensate air falls as rain

Question 2

How does convectional rainfall work?

Answer 2

i. Surface of the air is heated by the sun
ii. Warm surface heats the air above it, causing the air to rise as it is heated (has more energy so expands –> becomes less dense –> lighter so it rises through the colder air)
iii. The air (that is rising) begins to cool and condensate
iv. Further rising and cooling causes a large amount of condensation to occur and rain is formed

Question 3

What type of clouds does convectional rainfall produce?

Answer 3

Tends to produce towering cumulo-nimbus clouds, which produce heavy rain and possible thunder and lightening.

Question 4

Where is frontal rainfall most common?

Answer 4

Associated with the movement of depressions (low pressure systems and cold fronts)

Question 5

What kinds of clouds/conditions does frontal rainfall cause?

Answer 5

Produces a variety of clouds, which bring moderate to heavy rainfall.

Question 6

What are the three kinds of rainfall?

Answer 6

1/ Frontal Rainfall

2. Relief rainfall
3. Convectional rainfall

Question 7

What kind of rainfall operates in rainforests?

Answer 7

Convectional rainfall due to equatorial temperatures.

- Ground is heated by the hot sun

Question 8

How does frontal rainfall work?

Answer 8

i. Two air masses meet, one warm air and one a cold air mass
ii. The lighter, less dense, warm air is forced to rise over the denser, cold air.
iii. Warm air begins to cool at higher altitude and begins to condense
iv. As the warm air is forces to rise further, condensation occurs and rain is formed

Question 9

Where is relief rainfall most common?

Answer 9

Very common in UK, especially on the West coast since the prevailing weather comes from that direction. Associated with coastal mountainous regions.

Question 10

How does relief rainfall work?

Answer 10

i. Prevailing winds pick up moisture from the sea as they travel across it –> makes the air moist
ii. Moist air reaches the coast and is forced to rise over hills and mountains
iii. Moist air cools and condenses in the higher altitudes over the mountains and drops its moisture as relief rain
iv. Once over the top of the mountain and travelling down the other side, air warms again, giving it a greater ability to carry moisture
v. –> little rain occurs on the far side of the mountain - called the rain shadow.