Atmospheric Stability, Clouds and Lapse Rates

Hot Air Rises

http://www.youtube.com/watch?v=YsCXw2bQU50&list=PL4D17D18D91FA431E&index=13 or

http://www.youtube.com/watch?v=0Hv07HLRlbc

PV/T=constant

http://www.metlink.org/pdf/teenagers/experiments/candle-water.pdf

http://www.youtube.com/watch?v=cNh3N_1e4wQ&list=PL4D17D18D91FA431E

Dry Adiabatic Lapse Rate

The rate at which dry air cools as rises through the atmosphere

DALR=9.8°C/km

Stability

unstable stable

How Clouds Form

http://www.youtube.com/watch?v=-nbU1TXT3Bg&list=PL4D17D18D91FA431E

When the rate of condensation is faster than the rate of evaporation, and the air is dirty, cloud droplets form. The rate of evaporation falls as the air gets colder, so there will be a certain temperature, called the dew point, at which cloud drops form.

Latent Heat ReleaseSaturated Adiabatic Lapse Rate

• When water vapour condenses to form cloud droplets, latent heat is released

• This heat warms the air around• So, when cloud droplets are forming, the

rate at which air cools as it rises is less than the DALR

• Typically, the SALR is usually between 4°C/ km and 9°C/km, but on average its 5°C/km.

Cloud Base Height