Lesson 4 - Precipitation and excess run off within the water cycle

Question 1

What process is involved in the formation of clouds?

Answer 1

Condensation

Question 2

What is the basic process of cloud formation?

Answer 2

Heat causes the uplift of water from the earths surface into the surrounding air (evaporation), as this air heats it rises. The pressure falls as the air rises causing it to expand. As it reaches a certain point it cools enough to form water droplets which present as clouds (condensation).

Question 3

What is the main return of water back to the earths surface?

Answer 3

Precipitation from clouds

Question 4

What is relief rainfall (Orographic)

Answer 4

When the prevailing wind forces the saturated air to hit the side of a mountain forcing it up the mountain, the air then condenses into clouds causing precipitation on the windward side of the mountain. The air falls down and warms back up on the offside of the mountain creating a rainfall shadow.

Question 5

What is convectional rainfall?

Answer 5

When the sun warms air on the earths surface causing it to rise, it rises to a certain point before becoming too cool and condensing into clouds. The cloud then becomes too heavy and sudden rainfall hits.

Question 6

What is frontal rainfall?

Answer 6

Frontal rainfall is when a mass of cold air meets a mass of warm air, the cold air forces the warm air to rise and condense into clouds before releasing precipitation. Mostly on the warm air side but can extend over.

Question 7

What are the two theories of precipitation formation?

Answer 7

• Collision mechanism theory
• Bergeron Findeisen Process

Question 8

How does the collision mechanism theory work?

Answer 8

The idea that the free water droplets within the cloud float around and collide with one another. They bond together to form larger droplets, as these droplets get larger they become much heavier and then fall down as rain due to gravity.

Question 9

How does the Bergeron Findeisen theory work?

Answer 9

The idea that a cold cloud contains both ice crystals and supercooled droplets. These ice crystals form and attract the supercooled droplets so they condense and freeze onto the crystals. The crystals then become too heavy and fall. If they remain frozen they fall as snow whereas they may cool and fall as rain.

Question 10

What are the main flows that cause excess run off generation into rivers etc?

Answer 10

• Through flow ( Vertical movement of water through the soil)
• Ground water flow (Lateral movement of water through the soil)
• Overland flow (water flows across the earths surface)

Question 11

Physical factors that affect excess run off generation

Answer 11

• Intensity and duration of rainfall
• Soil type
• Relief of land

Question 12

Explain how soil type may affect the types of run off in a drainage basin

Answer 12

If the soil type is more permeable then the through flow and ground water flow would increase however if it is less permeable then the overland flow would increase and others would decrease.

Question 13

Human factors that could affect excess run off generation

Answer 13

• Land use
• Urbanisation