Heat, Temperature, Pressure & Humidity Flashcards
Water in the atmosphere can exist in three different states:
Ice - this is the lowest energy state in which water exists, individual molecules remain still and separate
Liquid - more energy than ice, movement within body of liquid
Vapour - highest energy state. Individual molecules can move about three dimensionally to occupy a space
Water cannot change from one state to another without what taking place?
Latent heat exchange.
The amount of water vapour in a parcel of air at a given pressure depends on its what?
Temperature.
When the amount of water vapour present is such that a parcel of air can hold no more:
It is completely saturated.
As the temperature of a parcel of air is reduced at a constant pressure, its ability to hold water vapour…
Reduces.
There are two ways a parcel of air can reach a saturated state:
At constant temperature, water can be added until saturated.
With a constant amount of water, temperature can be reduced until it can no longer hold that vapour (most important process during saturation).
Relative humidity is:
A ratio of the mass of water vapour actually present in a given parcel of air to the mass of water vapour which would cause saturation at the same temperature and pressure.
Dew point temperature is:
The temperature at which saturation would occur on a given parcel of air.
Lower air density will occur if:
- The temperature increases
- There is a higher humidity or
- The air pressure is lowered
The atmosphere is said to be ‘absolutely stable’ when:
The parcel of air ceases rising or falling of its own accord.
The atmosphere is said to be ‘absolutely unstable’ when:
The air continuously rises.
The atmosphere is said to be ‘continuously unstable’ when:
The air continues to rise or fall of its own accord.
ELR
Environmental Lapse Rate.
The standard environmental lapse rate in ISA conditions is 2C/1000’
On most days the ELR is anything but 2C/1000’
The ELR on any particular day largely determines the stability of:
The atmosphere.
