Weather - Soundings - Cumulus Clouds?

Question

Which one of the following soundings is conditionally stable and would favor towering cumulus clouds - +3 C°/1000 m b) −2 C°/1000 m c) −8 C°/1000 m d) +1 C°/1000 m

−8 C°/1000 m

+3 C°/1000 m

−2 C°/1000 m

+1 C°/1000 m

Answer 1

The answer is -8ºC/1000m. This is known as the lapse rate, or basically the rate at which temperatures decrease with height. This means that for every 1000m (1km) you go up in the atmosphere, the temperature will drop 8ºC.

+3ºC/km and +1ºC/km are not possible because temperature does not increase with height (usually). For the purpose of the question, the development of towering cumulus clouds means that a parcel (pocket) of air must cool down as it goes up.

A lapse rate of 8ºC/km indicates a moderately unstable environment which is perfect for towering cumulus development. Lapse rates greater than 9.6ºC/km are absolutely unstable while lapse rates less than 6ºC/km are absolutely stable and would not favor towering cumulus development.