06 - Condensation and Cloud Formation

Question 1

How do clouds form (basic)?

Answer 1

• Hot air rises because it has expanded and become less dense.
• As it rises it cools causing water droplets held in the air to condense forming clouds.
• When the weight of the liquid water in the clouds is enough to overcome the force of gravity the water will fall as precipitation

Question 2

What is the Dew Point?

Answer 2

• The Dew point is the critical temperature at which condensation occurs
• A cloud will form when a parcel of air reaches dew point

Question 3

What is released as water condenses?

Answer 3

• Latent heat is released as the water condenses

Question 4

What does it mean when the air is saturated?

Answer 4

We describe the air as saturated once dew point is reached as it is at 100% relative humidity and cannot hold any more water as vapour

Question 5

What is the troposphere?

Answer 5

• The troposphere is the lowest portion of the Earth’s atmosphere, and is also where all weather takes place
• It contains approximately 75% of the atmosphere’s mass and 99% of its water vapour and aerosols

Question 6

What happens to the temperature of the air as you travel up through the troposphere?

Answer 6

• It gets colder
• Approximately 6.5^oC per Km

Question 7

Why does it not get hotter as you move closer to the sun?

Answer 7

• The surface is warmed by the sun not the air, through conduction so as the air parcel gets further away from the ground it cools

Question 8

What is a Lapse Rate?

Answer 8

• A lapse rate is the rate of decrease temperature with height.
• There are two main types of lapse rate:
  
  1. the Environmental and 2) the Adiabatic (dry and wet)

Question 9

What is the Environmental Lapse Rate (ELR)?

Answer 9

• As we move away from the ground level the air temperature changes, it falls. The rate of this change is the Environmental Lapse Rate (ELR)
• The ELR is, on average, 6.4 0C per 1000 m

Question 10

What is the Adiabatic Lapse rate (Non-Saturated Air)?

Answer 10

• The Adiabatic Lapse Rate is the change in temperature of the parcel of air due to a change in its pressure.
• The parcel of air is still a self-contained bubble, there is no exchange of heat with its surroundings.
• Air that is not saturated will rise expand and therefore cool at the set rate of 10⁰C per 1000m

Question 11

What happens when the dew point equals the air temperature?

Answer 11

• When the dew point equals the air temperature, the air is saturated and the relative humidity is 100%.

Question 12

What is the Saturated Adiabatic Lapse Rate (SALR) cooling rate?

Answer 12

• 5^oC per 1000m

Question 13

What is a Stable and Instable parcel of air?

Answer 13

• If the parcel of air is at the same temperature as the surrounding environment, it will stop rising and eventually sink down. It is stable.
• If a parcel of air is warmer than the surrounding environment, it will continue to rise. It is unstable.