Deck 4: Atmospheric Humidity

Question 1

Which of the following terms refers to the temperature to which air must be cooled in order to become saturated?

A)wet-bulb temperature
B)minimum temperature
C)dew-point temperature
D)freezing point

Answer 1

C

Question 2

Dew Point
To which of the following percentages is relative humidity often nearest in the polar regions?

A)70%
B)60%
C)100%
D)40%

Answer 2

C

Question 3

Which of the following statements describes what occurs when the air temperature remains constant and water is evaporated into the air?

A)The relative humidity decreases.
B)The relative humidity oscillates between increases and decreases.
C)The relative humidity remains stable.
D)The relative humidity increases.

Answer 3

D

Question 4

If very cold air is brought indoors and warmed with no change in its moisture content, which of the following will happen to the relative humidity of this air?

A)It will decrease.
B)It will keep increasing and then decreasing.
C)It will increase.
D)It will remain stable.

Question 5

Which of the following is the BEST indicator of the actual amount of water vapour in the air?

A)saturation vapour pressure
B)dew point temperature
C)relative humidity
D)air temperature

Question 6

At 4ºC, the atmosphere is saturated with water vapour. If the air temperature increases to 15ºC, with no addition or removal of water vapour, what is the dew point?

A)about 2ºC
B)about 15ºC
C)about 8ºC
D)about 4ºC

Question 7

Which of the following statements explains why night-time temperatures rarely drop below the dew-point temperature?

A)The ground releases sensible heat stored during daytime.
B)Saturation vapour pressures always increase at night.
C)The dew will absorb all the heat.
D)At saturation, latent heat of condensation is released into the air.

Question 8

Dew Point
Which city has the least amount of water vapour in the air?

A)City A
B)City B
C)City C
D)City D

Question 9

At which of the following times of day is the relative humidity normally at a minimum?

A)when the air temperature is lowest
B)just before sunrise
C)about midnight
D)when the air temperature is highest

Question 10

Dew Point
Which of the following is the measure of the total amount of water vapour in the air?

A)average temperature
B)dew point temperature
C)maximum temperature
D)minimum temperature

Question 11

Which of the following terms refers to the percentage of water vapour present in the air compared to that required for saturation?

A)relative humidity
B)mixing ratio
C)absolute humidity
D)dew point

Question 12

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following instruments uses wet-bulb and dry-bulb temperature to obtain relative humidity?

A)infrared hygrometer
B)hair hygrometer
C)sling psychrometer
D)electrical hygrometer

Question 13

Which of the following is the main reason why vegetables take longer to cook in boiling water at high altitudes?

A)The temperature of the boiling water decreases with increasing altitude.
B)Saturation vapour pressure decreases with increasing altitude.
C)Water boils at a higher temperature at higher altitudes.
D)There is less oxygen in the air at high altitudes.

Question 14

As the air temperature increases, with no addition of water vapour to the air, which of the following will happen to the dew point?

A)It will increase.
B)It will become equal to the air temperature.
C)It will decrease.
D)It will remain the same.

Question 15

As air temperature increases, which of the following happens to the air's capacity for water vapour?

A)It can either increase or decrease.
B)It increases.
C)It decreases.
D)It remains constant.

Question 16

Which of the following is the name for the maximum pressure that water vapour molecules exert when the air is saturated?

A)boiling point
B)absolute humidity
C)mixing ratio
D)saturation vapour pressure

Question 17

When the air is saturated, which of the following conditions occurs?

A)The air temperature equals the wet-bulb temperature.
B)The relative humidity is 90 percent.
C)A decrease in temperature causes condensation to occur.
D)The air temperature is lower than the dew point temperature.

Question 18

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
How much water would cover the globe if all the water vapour in the atmosphere condensed and fell to the ground?

A)about 100 centimetres
B)about 1 metre
C)about 2.5 centimetres
D)about 1 millimetre

Question 19

Which of the following terms refers to the density of water vapour in a given parcel of air?

A)mixing ratio
B)specific humidity
C)absolute humidity
D)relative humidity

Question 20

Dew Point
Which of the following describes what a high water vapour pressure indicates?

A)A relatively high rate of evaporation is occurring.
B)An abundant supply of condensation nuclei is in the air.
C)A relatively large number of water vapour molecules are in the air.
D)A relatively small number of water vapour molecules are in the air.

Question 21

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Suppose saturated polar air has an air temperature and dew point of -10ºC, and unsaturated desert air has an air temperature of 35ºC and a dew point of 10ºC. Which of the following describes the water vapour and relative humidity of desert air compared to polar air?

A)Desert air has less water vapour and lower relative humidity than polar air.
B)Desert air has less water vapour and higher relative humidity than polar air.
C)Desert air has more water vapour and lower relative humidity than polar air.
D)Desert air has more water vapour and higher relative humidity than polar air.

Question 22

Which of the following amounts is the water vapour pressure that occurs when water vapour comprises 3.5 percent of an air parcel whose total pressure is 100 kPa?

A)103.5 kPa
B)35 kPa
C)96.5 kPa
D)3.5 kPa

Question 23

Which of the following factors will increase in a rising parcel of air?

A)air temperature
B)saturation vapour pressure
C)mixing ratio
D)relative humidity

Question 24

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following is used to directly measure the relative humidity?

A)nephelometer
B)anenometer
C)disdrometer
D)sling psychrometer

Question 25

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Consider the situation where the air temperature in a room is 21ºC, the saturation vapour pressure is 25 hPa, the dew point temperature is 7ºC, and the actual vapour pressure is 10 hPa. Which of the following is the relative humidity?

A)near 40%
B)near 35%
C)near 20%
D)near 15%

Question 26

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Suppose it is snowing outside and the air is saturated. The air temperature and dew point are both -9ºC, and the actual vapour pressure is 3 hPa. If this air is brought indoors and warmed to 24ºC, what would be the relative humidity of this air, assuming that its moisture content does not change? (The saturation vapour pressure at 24ºC is 30 hPa.)

A)50%
B)5%
C)10%
D)30%

Question 27

Which of the following factors mainly determines the temperature at which water boils?

A)air temperature
B)air pressure
C)air density
D)relative humidity

Question 28

At which of the following times of day does the relative humidity usually reach a maximum value?

A)the time when the air temperature is lowest
B)just before sunrise
C)the middle of the afternoon
D)the time when the air temperature is highest

Question 29

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
In which of the following summer climates are evaporative coolers primarily used?

A)cold and humid
B)hot and humid
C)cold and dry
D)hot and dry

Question 30

Which of the following gives the main reason why eastern Canada is more humid in summer than the Canadian coastal areas of the Pacific?

A)There is lower air temperature in Southern British Columbia.
B)There is low relative humidity of the air over the Pacific Ocean.
C)There is higher water temperature in the Gulf of Mexico.
D)There is higher air temperature in eastern Canada.

Question 31

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
In which part of Canada are average summer dew point temperatures highest?

A)the West Coast
B)the Arctic
C)the Prairies
D)Southern Ontario

Question 32

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Without any addition or removal of water vapour, what happens to the actual vapour pressure when the air temperature increases?

A)It stays the same.
B)It decreases.
C)It becomes greater than the saturation vapour pressure.
D)It increases.

Question 33

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
As the difference between the air temperature and the dew point increases, which of the following happens to the relative humidity?

A)It increases.
B)It remains constant and equal to 100 percent.
C)It remains constant at a value less than 100 percent.
D)It decreases.

Question 34

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
If very cold air is brought indoors and warmed with no change in its moisture content, which of the following will happen to the saturation vapour pressure of this air?

A)It will remain stable.
B)It will keep increasing and then decreasing.
C)It will increase.
D)It will decrease.

Question 35

On which of the following does saturation vapour pressure depend?

A)the volume of air
B)the mass of water vapour
C)air temperature
D)the total mass of air

Question 36

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following occurs when a glass of water is surrounded by saturated air?

A)The water temperature slowly increases.
B)The water level in the glass does not change.
C)The water temperature slowly decreases.
D)The water level in the glass slowly decreases.

Question 37

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
A baseball hit nearly 100 metres on a hot, humid day will travel about what percentage of the same distance on a hot, dry day?

A)100%
B)95%
C)50%
D)30%

Question 38

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Ignoring the contributions of wind, which of the following statements explains why a baseball can be expected to travel farther in warm, humid air?

A)Water vapour helps to lift the baseball even higher.
B)Water vapour is less dense than dry air.
C)Water vapour reduces the weight of the ball.
D)Water vapour sticks to baseballs.

Question 39

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which city has the highest relative humidity?

A)City A
B)City B
C)City C
D)City D

Question 40

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which city has the greatest amount of water vapour in the air?

A)City A
B)City B
C)City C
D)City D

Question 41

When calculating a water budget for a Canadian location, in which of the following seasons does the actual evapotranspiration typically NOT keep pace with the potential evapotranspiration?

A)winter
B)spring
C)summer
D)autumn

Question 42

Which of the following describes the saturation vapour pressure over water when the air temperature is below freezing?

A)equal to the saturation vapour pressure over ice
B)greater than the saturation vapour pressure over ice
C)equal to zero
D)less than the saturation vapour pressure over ice

Question 43

Which of the following statements describes what occurs when the air temperature remains constant and water is evaporated into the air?

A)The dew point oscillates between increases and decreases.
B)The dew point remains stable.
C)The dew point increases.
D)The dew point decreases.

Question 44

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Suppose the dew point of cold outside air is the same as the dew point of the indoor air. If the door is opened and cold air replaces some of the warm air, what is the new relative humidity indoors?

A)higher than before
B)the same as before
C)impossible to tell from the information given
D)lower than before

Question 45

When air temperature increases, which of the following happens to the saturation vapour pressure?

A)It remains the same.
B)It keeps increasing and decreasing.
C)It increases.
D)It decreases.

Question 46

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following instruments measures humidity by measuring the amount of radiant energy absorbed by water vapour?

A)sling psychrometer
B)electrical hygrometer
C)hair hygrometer
D)infrared hygrometer

Question 47

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following statements about water vapour is correct?

A)Vapour pressure decreases with increasing altitude.
B)A decrease in the number of water vapour molecules will increase the vapour pressure.
C)If air pressure falls, vapour pressure will increase.
D)The vapour pressure is typically higher than the partial pressure exerted by oxygen.

Question 48

Which of the following factors will decrease in a rising parcel of air?

A)specific humidity
B)mixing ratio
C)relative humidity
D)absolute humidity

Question 49

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
A humidex reading over which of the following values is considered dangerous?

A)30
B)40
C)46
D)54

Question 50

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following is the name for the lowest temperature that can be attained by evaporating water into the air?

A)frost point
B)heat index
C)minimum temperature
D)wet-bulb temperature

Question 51

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
In a blinding snowstorm in Whitehorse, the air temperature and dew point temperature are both -1ºC. Meanwhile, under clear skies in Toronto, the air temperature is 29ºC and the dew point temperature is 3ºC. Which of the following can be concluded from this information?

A)Whitehorse and Toronto are both located next to the ocean.
B)The same amount of water vapour is found in the air in Toronto and Whitehorse.
C)There is more water vapour in the air in Toronto.
D)There is more water vapour in the Whitehorse snowstorm.

Question 52

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following terms refers to the ratio of the mass of water vapour in a given volume (parcel) of air to the mass of the remaining dry air?

A)absolute humidity
B)mixing ratio
C)relative humidity
D)dew point

Question 53

For the following questions refer to the temperature and dew point data in the following cities:
During the winter, which of these factors leads to the irritation of the mucus membranes in the nose and throat?

A)the low relative humidity
B)the wind chill
C)the reduced daylight
D)the low air temperature

Question 54

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which city has the highest saturation vapour pressure?

A)City A
B)City B
C)City C
D)City D

Question 55

Which of the following describes the mixing ratio?

A)It changes with temperature.
B)It is expressed in grams of water vapour per kilogram of dry air.
C)It increases with the increase of a given volume of air.
D)It is a relative measure of water vapour.

Question 56

When comparing the water budgets from each of the following locations, on average which would have the lowest amount of runoff?

A)Regina, SK
B)Toronto, ON
C)Vancouver, BC
D)St.John's NL

Question 57

In which of the following conditions does wet laundry hanging outdoors on a clothesline dry most quickly?

A)15 75% 20
B)15 50% 20
C)4 50% 10
D)4 75% 20

Question 58

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following describes how much of the world's supply of precipitation is equivalent to the total mass of water vapour stored in the atmosphere at any moment?

A)about 1 week's supply
B)about 1 month's supply
C)about 1 day's supply
D)about 1 year's supply

Question 59

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following will happen to the relative humidity as the air temperature increases, and with no addition of water vapour to the air?

A)It will increase.
B)It will decrease.
C)It will remain the same.
D)It will increase until it equals the dew point temperature.

Question 60

For the following questions refer to the temperature and dew point data in the following cities:
Which of the following changes happens to the humidity if the amount of water vapour in the atmosphere remains constant?

A)It must change, regardless of which measure of humidity is used.
B)It might change, depending on which measure of humidity is used.
C)It cannot change, if absolute humidity is the measure of humidity used.
D)It will change only if absolute humidity is the measure of humidity used.Dew Point

Question 61

Does lowering the temperature in your home during the winter cause the relative humidity to increase or decrease? Why? What physiological effects might you experience during both humid and dry conditions?

Question 62

Describe the differences in the molecular structure of the water molecules in the gas, liquid, and ice phases of water.

Question 63

Explain why the temperature overnight seldom drops below the afternoon dew point.

Question 64

Explain why the statement "warm air can hold more water vapour molecules" is misleading and commonly misinterpreted. Suggest a better way to explain this concept.

Question 65

Explain why the dew point temperature provides a better indication of the air's actual water vapour content rather than its relative humidity.

Question 66

Explain why high humidity in the summer makes us feel warmer than the air temperature suggests.

Question 67

Explain why condensation is more likely to occur on a glass of water sitting on a table outdoors on a warm day as opposed to a cold day.

Question 68

In order to reduce evaporation and conserve water, is it better to water a lawn in the early morning or early evening? Explain why.

Question 69

Explain why, at temperatures below freezing, the saturation vapour pressure over water is greater than the saturation vapour pressure over ice.

Question 70

Even if the relative humidity of polar air is often close to 100 percent, explain why polar air is often described as dry.

Question 71

Describe the hydrologic cycle and draw a diagram to illustrate the circulation of water in the atmosphere.

Question 72

How can you heat air without decreasing its relative humidity?

Question 73

An enterprising travel agent trying to sell you a summer vacation package to Calgary, Alberta, claims that the summertime relative humidity is above 90 percent. Can this be true? Explain.

Question 74

Dew Point
For the following questions refer to the temperature and dew point data in the following cities:
Which of the following procedures will increase the relative humidity in a home during the winter?

A)lowering the temperature of the air inside the home
B)taking a shower and letting the air circulate in the home
C)increasing the thermostat setting
D)sealing the house against drafts

Question 75

What is meant by the terms "water vapour saturation" and "saturation vapour pressure"? Why does the saturation vapour pressure increase with increasing air temperature?

Question 76

People who wear glasses know that when they enter a warm building after being outdoors in subfreezing temperatures, condensation occurs on the lenses of their glasses. Why doesn't condensation occur on the lenses when they go outside after a lengthy stay inside the warm building?

Question 77

In terms of the air temperature and water vapour content, explain how the relative humidity normally changes during a 24-hour day.

Question 78

Describe how a sling psychrometer is used to determine the relative humidity or dew point.