Moisture
There are two types of gases in the atmosphere: Constant and variable.
Water vapour is a variable gas.
It is very important that we have water vapour in the atmosphere because:
1) It determines the amount of precipitation which is very important for life,
cultivation etc
2) It in uence the heat balance of the earth
The three states of water:
fl
, Humidity
The amount of water vapour in the air.
• The higher the temperature the more water
vapour the air can contain before it is saturated.
• Warm saturated air when cooled can release
more moisture than cooler saturated air.
• More precipitation will occur when the rate of
cooling of air is rapped.
Thus the warmer the air the more water vapour
it can hold.
• When air is holding its maximum amount of water vapour (as much water
vapour as it can hold), we say the air is saturated.
• Air that is holding less than maximum water vapour capacity is said to be
unsaturated or dry.
• The actual amount of water vapour present in the air is referred to as
absolute humidity. But this makes it hard to compare samples.
Relative humidity
The amount of water vapour in the air expresses as a percentage of the
water vapour capacity of air at that temperature.
Formula:
RH= Absolute humidity
✖ 100
Water vapour capacity
• When the relative humidity is 100% we say that the air is saturated and if it
is less than 100% we say the air is unsaturated.
• If air is cooled the relative humidity increases and eventually the air
becomes saturated.
• If the air cools to below the saturation temperature it can no longer hold
the water vapour and the water vapour is released through condensation.
I.e it changes from a gas to a liquid.
There are two types of gases in the atmosphere: Constant and variable.
Water vapour is a variable gas.
It is very important that we have water vapour in the atmosphere because:
1) It determines the amount of precipitation which is very important for life,
cultivation etc
2) It in uence the heat balance of the earth
The three states of water:
fl
, Humidity
The amount of water vapour in the air.
• The higher the temperature the more water
vapour the air can contain before it is saturated.
• Warm saturated air when cooled can release
more moisture than cooler saturated air.
• More precipitation will occur when the rate of
cooling of air is rapped.
Thus the warmer the air the more water vapour
it can hold.
• When air is holding its maximum amount of water vapour (as much water
vapour as it can hold), we say the air is saturated.
• Air that is holding less than maximum water vapour capacity is said to be
unsaturated or dry.
• The actual amount of water vapour present in the air is referred to as
absolute humidity. But this makes it hard to compare samples.
Relative humidity
The amount of water vapour in the air expresses as a percentage of the
water vapour capacity of air at that temperature.
Formula:
RH= Absolute humidity
✖ 100
Water vapour capacity
• When the relative humidity is 100% we say that the air is saturated and if it
is less than 100% we say the air is unsaturated.
• If air is cooled the relative humidity increases and eventually the air
becomes saturated.
• If the air cools to below the saturation temperature it can no longer hold
the water vapour and the water vapour is released through condensation.
I.e it changes from a gas to a liquid.
