Water Vapour Flashcards
Explain sources of water vapour in atmosphere and characteristics
Evaporation/sublimation form any wet surface
Transpiration = plants releasing water vapour
Most water in troposphere
4% at equator, almost 0% at poles
Describe vapour pressure and saturation vapour pressure
Vapour pressure = partial pressure of water vapour in air
Does not change with temperature
Saturation vapour pressure = vapour pressure when it saturates/maximum it can hold
Changes With temp
Increase = higher VP required and lower is reverse
Define latent heat
Heat energy released/absorbed when substance changes state.
Does not change its own temperature
Describe the condensation process
Water vapour changing to liquid state
•Cooled to dew point/saturation vapour pressure
•Release latent heat
Describe the freezing processes with reference to latent heat
Freezing = temperature below 0°C
•Liquid to solid change in state
•Release latent heat
Describe the melting processes with reference to latent heat
Melting = temperature above 0°C
•Solid to liquid change in state
•Absorb/stored in the liquid
Describe the diurnal variation of relative humidity and dew point
On the basis that moisture content remains constant and since RH is temperature dependent and warmer air can hold more water vapour so the amount of vapour needed to saturate is greater therefore RH decreases during the day with the lowest at the afternoon.
RH is maximum approximately 30 minutes after sunrise when the temperature is minimum
Describe the effects of moisture content on the density of the air
Water vapour light gas compared to oxygen and nitrogen
•Water is H2O (hydrogen and oxygen)
•Hydrogen = lightest element on periodic table
•Increase moisture content = decrease in density
Describe the condensation process
Environment is cooled to its dew point temp, thus becoming saturated with respect to water vapour. Latent heat stored in water.
Vapour is released to the environment when condensation occurs.
