Chapter 7 - Humidity Flashcards
Can Water Vapour been seen?
No, and should not be confused with Water droplets i.e clouds or steam
Where is a lot of water vapour present
Over the oceans
What does water vapour molecules need to start condensing?
What is the size of an average cloud droplet
Tiny particles of matter/ cloud condensation nuclei/ micrometrical particles
ie dust, salt particles and pollen
0.02mm
What are super cool water droplets
ice droplets because there’s not enough nuclei
-0 to -40
For any given pressure or temperature water vapour the air can?
only hold a certain amount of water vapour
How much water vapour can warm air hold?
A lot more than cold
Absolute Humidity?
Is the amount water vapour in a volume of air g/m3
Specific Humidity / Mixing ratio?
Is the amount of water vapour in mass with a mass of air expressed in g
RE / relative humidity is?
Is expressed as a percentage of basically how much water vapour is present compared to air
How do we measure humidity
hair hydrometer, psychrometer or wet & dry bulb.
How does the wet and dry bulb thermometer work?
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.
What is the Dew point?
It is where the air has become saturated and if it is cooled any more it starts to condense
If the Dew point and ambient temp are close together what can you expect?
Low cloud, Fog
if you have 10g of water vapour and 30g of air what is the RE?
25%
if you have 10g of water vapour and 20g of air what is the RE?
33%
