Factors driving the change in magnitude of water stores over time and space— Condensation, Precipitation and Cloud Formation

Question 1

Define condensation

Answer 1

. When water vapour changes state to become a liquid — it loses energy to the surroundings

Question 2

Causes of warm air to cool (condensation), leading to precipitation

Answer 2

. Air containing water vapour needs to cool to its dew point but the volume of air remains constant. This occurs when:

— warm moist air passes over a cold surface

— In winter night, when heat is radiated out to space and the grounds get colder, cooling the air directly in contact with it

. When volume of air increases but there is NO addition of heat, instead there’s adiabatic cooling . Lower pressure exists at higher altitudes. This happens when air rises and expands in the lower pressure of the atmosphere. This happens due to:

Topography — when air meets mountains, it’s forced to rise, causing it to cool. This results in orographic precipitation

Other air masses — Warm air is less dense than cool air. As result when warm air meets cold air, the warm air forced up above the cool air. It cools down as it rises This results in frontal precipitation.

Convection — when the sun heats up the ground, moisture on the ground evaporates and rises up in a column of warm air. As it gets higher, it cools. This results in convective precipitation.

Question 3

Define dew point

Answer 3

The temperature at which water changes from gas to a liquid.

Question 4

Why does condensation leading to precipitation happen?

Answer 4

. As air cools it is able to hold less water

. If cooled sufficiently, air will get to a temperature at which it becomes fully saturated with water vapour. This is the dew point

. Excess water in the air will then be converted to liquid water in this process

Question 5

Factors that affect size / rate of condensation

Answer 5

. Amount of water vapour in the atmosphere — more water vapour in the the air, the higher the condensation rate

. Size of temperature drop — if there’s a rapid or large drop in temperature, condensation will be high

. Air pressure — the lower the pressure, the higher the condensation. If there is a fall in pressure, it is air is able to hold less water.

Question 6

Define adiabatic cooling

Answer 6

. the process of reducing heat through a change in air pressure caused by volume

Question 7

What is the cause of precipitation?

Answer 7

Condensation

Question 8

Define precipitation

Answer 8

.Precipitation is any liquid or frozen water that forms in the atmosphere and falls to the Earth

Question 9

How do clouds form, leading to precipitation?

Answer 9

1. )Heat from the sun warms the ground, causing warm air with water vapour to rise
2. ) Cloud formation is due to water vapour in the atmosphere becoming concentrated due to cooling of air and increase in water vapour
3. )Clouds form when warm air to cools down, causing the water vapour in it to condense into water droplets or ice crystals, which gather as clouds
4. )Water droplets caused by condensation are too small to form clouds on their own. For clouds to form, there have to be tiny particles of other substances (e.g dust or soot) to act as cloud condensation nuclei. They give water a surface to condense on. This encourages clouds to form, rather than allowing the moist air to disperse.
5. )When the water droplets gathered get big enough, they fall as precipitation

Question 10

Define Topography

Answer 10

the arrangement of the natural and artificial physical features of an area.

Question 11

Examples of precipitation

Answer 11

. Snow 
. Rain
. Hail
. Sleet
. Ice crystals

Question 12

How do cloud formation and precipitation vary in regards to time and space?

Answer 12

. Seasonally — e.g. in the UK there’s more rainfall in the winter than the summer

. Location — e.g. precipitation tends to be higher in the tropics than at the poles as cold air cannot hold as much water vapour. Remember this is as cold air can’t as much water vapour as warm air.

Question 13

Are clouds gas?

Answer 13

. Although clouds look like they are made out of gas, they are actually a large mass of water droplets of liquid water or ice crystals

Question 14

Name the three types of precipitation

Answer 14

. Convective precipitation
. Orographic precipitation
. Frontal precipitation

Question 15

Define condensation nuclei

Answer 15

. tiny particles (e.g. dust) in the atmosphere where water vapour condenses on.

Question 16

Define dew

Answer 16

. Moisture that forms as a result of condensation

Question 17

Where can water droplets be?

Answer 17

. Water droplets can stay in the atmosphere or flow to other subsystems

. e.g. when water condenses, it can form dew on leaves and other surfaces — this decreases the amount of water stored in the atmosphere.

Question 18

Define cloud

Answer 18

. Visible mass of water droplets or ice crystals suspended in the atmosphere