Chapter 7 - Humidity Flashcards Preview

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Flashcards in Chapter 7 - Humidity Deck (19)
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1
Q

Can Water Vapour been seen?

A

No, and should not be confused with Water droplets i.e clouds or steam

2
Q

Where is a lot of water vapour present

A

Over the oceans

3
Q

What does water vapour molecules need to start condensing?

What is the size of an average cloud droplet

A

Tiny particles of matter/ cloud condensation nuclei/ micrometrical particles

ie dust, salt particles and pollen

0.02mm

4
Q

What are super cool water droplets

A

ice droplets because there’s not enough nuclei

-0 to -40

5
Q

For any given pressure or temperature water vapour the air can?

A

only hold a certain amount of water vapour

6
Q

How much water vapour can warm air hold?

A

A lot more than cold

7
Q

Absolute Humidity?

A

Is the amount water vapour in a volume of air g/m3

8
Q

Specific Humidity / Mixing ratio?

A

Is the amount of water vapour in mass with a mass of air expressed in g

9
Q

RE / relative humidity is?

A

Is expressed as a percentage of basically how much water vapour is present compared to air

10
Q

How do we measure humidity

A

hair hydrometer, psychrometer or wet & dry bulb.

11
Q

How does the wet and dry bulb thermometer work?

A

dry one is a normal, the wet one has cloth and water at the bottom - if its a dry day = lots of evaporation and will read less.

if its a saturated day will more less read the same as dry.

12
Q

What is the Dew point?

A

It is where the air has become saturated and if it is cooled any more it starts to condense

13
Q

If the Dew point and ambient temp are close together what can you expect?

A

Low cloud, Fog

14
Q

if you have 10g of water vapour and 30g of air what is the RE?

A

25%

15
Q

if you have 10g of water vapour and 20g of air what is the RE?

A

33%

16
Q

What is 100% RE

A

the air is fully saturated with water vapour

17
Q

With a decrease of temperature what happens to RE?

A

increases

18
Q

What is the equation for RE?

A

Temp - Dew point x 400 = cloud base in ft

19
Q

Give the normal mass of WV in +10, +30 and -10

A
\+10 = 7.8
\+30 = 28g
-10 = 1.8g