Moisture in the Atmosphere

Question 1

What three factors is evaporation governed by?

Answer 1

1. Amount of moisture already in the air; 2. Availability of moisture; 3. Availability of heat energy

Question 2

How does wind contribute to evaporation?

Answer 2

It is a minor factor that replaces saturated air with unsaturated air

Question 3

What is the main source of evaporation for the atmosphere?

Answer 3

Warm oceanic areas

Question 4

At what point will evaporation into overlying air cease?

Answer 4

When the air becomes saturated

Question 5

What does vapor (e) pressure represent?

Answer 5

The amount of water held in the air

Question 6

What does saturated vapor pressure (es) represent?

Answer 6

The maximum amount of water vapor which an air parcel can hold at the same temperature

Question 7

Water will continue to evaporate until (?) = (?)

Answer 7

E = Es

Question 8

Why is heat required for evaporation?

Answer 8

To provide the latent heat of evaporation

Question 9

What wind direction in respect to Uk geographic location would bring cold and dry air?

Answer 9

North or east winds

Question 10

What wind direction in respect to UK geographic location would bring warm, moist air?

Answer 10

West or South West

Question 11

What is relative humidity defined as?

Answer 11

RH is a measure of the %amount of moisture in the atmosphere

Question 12

How is relative humidity calculated?

Answer 12

e/es * 100

Question 13

When does condensation occur

Answer 13

This is when vapour pressure is equivalent to saturated vapour pressure, (e=es), and relative humidity is 100%

Question 14

When is molecular kinetic energy greater?

Answer 14

At a higher temperature

Question 15

What is the dew point temperature?

Answer 15

The temperature at which condensation occurs (RH=100% and e=es).

Question 16

What is a high Td indicative of?

Answer 16

Moister air

Question 17

What is a low Td indicative of?

Answer 17

Dryer air

Question 18

What is Adiabatic process

Answer 18

Lifting and cooling to form condensation can be considered adiabatic. This is when no heat energy is exchanged with outside air.

Question 19

How does Adiabatic cooling occur?

Answer 19

As an air parcel rises it expands because the surrouding pressure gets lower; when it expands work is done and therefore heat is lost. This causes internal energy to decrease and cooling of the air to occur.

Question 20

What is adiabatic heating

Answer 20

The reverse of adiabatic cooling - the effects of descending air.

Question 21

How does adiabatic heating occur?

Answer 21

As the iar subsides, it contracts due to increasd pressure; then work is done and warms the air.

Question 22

What sort of mass air movement can adiabatic heating be associated with?

Answer 22

Links to anticyclone behaviors because the increasing temperature, due to the decent, means that the air tends to dry out as it warms

Question 23

What are the main characteristics of ‘stable air’

Answer 23

It doesn’t rise from free convection; this is when air is colder below that the air above.

Question 24

What does air stability depend on?

Answer 24

The temperature of the rising air relative to the temperature of the stationary surrounding air.

Question 25

What does air stability determine?

Answer 25

Whether clouds form when air is uplifted and which type of cloud forms.

Question 26

What is potential instability of air?

Answer 26

A layer of air which is forced to rise may become unstable and freely convect in certain circumstances.

Question 27

How does potential instability occur?

Answer 27

If the DALR > ELR then the air is stable and cooling more quickly than the air it travels in; however if the DALR < ELR then the air is unstable as it cools less quickly than the air it passes through.

Question 28

What is stability a function of in terms of the ocean?

Answer 28

A function of density - which is function of temperature and salinity.

Question 29

What is the Mass mixing Ratio?

Answer 29

The mass of water vapour in grams per kilogram of dry air.

Question 30

When does the dew point temperature occur?

Answer 30

Temperature at which saturation occurs if air is cooled at constant pressure without addition or removal of vapour.

Question 31

What happens when the air pressure and dew point are equal?

Answer 31

The relative humidity is 100%

Question 32

What 4 types of instrument can atmospheric moisture be measured with?

Answer 32

Wet-bulb thermometer; Psychrometer; Dew-point hygrometer; Hydrograph

Question 33

How does a wet-bulb thermometer work?

Answer 33

Bulb of a standard thermometer wrapped in Muslin, which is kept moist by a wick from a reservoir of pure water. Evaporative cooling of the wet bulb gibes a reading that can be used in conjunction with a simultaneous dry-bulb temperatue

Question 34

What is a dew-point hygrometer.

Answer 34

Detects when condensation first occurs on a cooled surface.

Question 35

What is the latent heat required to evaporate 1kg of water at 0C?

Answer 35

2.5 * 10^6 J

Question 36

How is the energy requirded for evaporation obtained?

Answer 36

From the removal of heat from immediate surroudings - causing apparent heat loss, (latent heat).

Question 37

What factors does the rate of evaporation depend on?

Answer 37

The differecne betwen the SVP at the water surface and the vapour pressure of the air and the existence of a continual supply of energy to the surface.

Question 38

How does wind velocity affect evaporation rate?

Answer 38

The wind is generally associated with the advection of unsaturated airm which will absorb the available moisture.