CH7 - Humidity Flashcards
What is humidity?
The word to describe water vapour in the air.
What is water vapour?
It is the water in its gaseous form.
Is water vapour and water droplets the same thing? Why?
No. Water droplets are visible, water vapour is not.
E.g. a kettle.
What are the different states of water?
Solid (ice), liquid (water) and gas (water vapour).
How is it called the change between one state to another?
Phase change.
From solid, to liquid, to gas.
What is “sublimation”? How does it work?
It’s the phase change DIRECTLY from solid to gas or from gas to solid.
Gas > CONDESATION > Liquid > FREEZING > Ice
Ice > MELTING > Liquid > EVAPORATION > Gas
What is the “dew point” or “saturation point”?
It’s the moment at which, reached a particular temperature, it becomes impossible to hold all the water vapour molecules.
What is the main problem for pilots when facing to supercooled water droplets?
Supercooled water droplets can result in instant and severe airframe icing.
What is the way to measure humidity?
Hygrometer.
What are the different units of humidity?
Absolute humidity, the mass of the water vapour in grams per unit volume of air (m3) which is g/m3.
Relative humidity, the ratio of the partial pressure of the water vapour to the saturated vapour pressure, expressed as a percentage.
What is the formula to work out the cloud base (ft)?
Temp - Dew Point x 400 = Cloud base (ft)
