Ch 7 - Humidity Flashcards Preview

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Flashcards in Ch 7 - Humidity Deck (29):
1

What is humidity?

A measure of how much water vapour a mass or volume of air is holding

2

What is latent heat?

The heat absorbed or released when changing state

3

What is a Saturated Pressure Level?

- The level at which a given mass or volume of air can hold no more water vapour
- No more evaporation can take place into the air without water vapour first being lost through condensation

4

What does it mean if air is saturated?

100% humidity

5

Does dry air have a high or low water content?

Low

6

What is dry air?

Water content with a relative humidity less than 100%

7

Can water evaporate fast or slowly into dry air?

Fast

8

Can water evaporate fast or slowly into saturated air?

Slow

9

What is absolute humidity?

g/m3

Mass of water vapour (g) in a cubed metre of air

10

What is the mixing ratio?

g/kg

Mass of water vapour (g) in a kg of air

11

What is a parcel of air's Saturated Mixing Ratio?

The mixing ratio when it is saturated

12

What is the approximate maximum amount of water vapour that a kg of air can hold?

50g/kg (5%)

13

Is the mixing ratio affected by temperature changes?

No

14

What is relative humidity? (2 definitions)

- % of water content in a parcel of air, compared with the maximum it can hold

- Ratio between Mixing Ratio and Saturated Mixing Ratio

15

What is the air at 100% relative humidity?

Saturated

16

What happens to Relative Humidity as temperature increases?

Decreases

17

What happens to Relative Humidity as temperature decreases?

Increases

18

What is air when humidity > 100%?

Super saturated

19

What is the Dew Point?

The temperature at which a parcel of air will reach saturation/100% humidity, due to relative humidity decreasing as a result of cooling.

20

Does air have a higher dew point with a higher or lower humidity?

Higher humidity = higher dew point

21

Calculate cloud base level

(Outside Air Temperature - Dew Point) x 400ft

22

When will there be a high risk of low cloud or fog?

When the Outside Air Temperature and Dew Point are close together

23

Why do clouds form lower in Winter?

Temperatures are colder

24

Is the Dew Point affected by temperature?

No

25

What happens to evaporation when air above a water source becomes saturated?

It stops

26

When can more evaporation into air take place?

- Higher temperature
- Drier air

27

What is diurnal variation of Relative Humidity?

- Mirrors diurnal variation of temperature
- As temperature goes up, Relative Humidity goes down

28

When are lowest and maximum humidity?

Lowest: 30 minutes after sunrise
Maximum: 15:00

29

Where is most humidity found?

Equatorial regions