Chapter 11

Question 1

Why are moist and dry adiabatic rates of cooling different?

Answer 1

Adiabatic rates refers to the situation where a parcel of air expands and cools, compress and warms with no interchange of heat with the surrounding air

DALR - 10 degrees per 1000m
MALR - 6 degrees per 1000m

Because heat added during condensation offset some of the cooling due to expansion, the air no longer cools at a dry adiabatic lapse rate but at a lesser rate called moist adiabatic lapse rate. A saturated parcel containing water droplets were to sink, it will compress and warm at a moist adiabatic lapse rate because the evaporation of water vapour offsets the rate of compressional warming

Question 2

What is a stable atmosphere and how can it form?

Answer 2

An absolutely stable atmosphere is when the environmental lapse rate is lower than the moist adiabatic lapse rate. In an absolutely stable atmosphere, a rising air parcel is colder and more dense than the surrounding air, causing it to return to its original position.

Question 3

Describe the general characteristics of clouds associated

with stable and unstable atmospheres.

Answer 3

Since air in a stable atmosphere have strong resistance to upward vertical motion, it will be spread out horizontally if forced to do so. Clouds formed in the rising air will then be spread out horizontally in relatively thin layers forming flat tops and bases. Formation of clouds such as cirrostratus, altostratus, nimbostratus, and stratus clouds

Since air in unstable atmosphere is warmer and less dense than the surrounding air, it will rise, constantly rising away from its original position forming cauliflower shaped cloud such as cumulus clouds

Question 4

List four primary ways clouds form, and describe the

formation of one cloud type by each method.

Answer 4

1. Surface heating and convection (IMPT)
   On a hot day, the sun heats up the earth’s surface and the surface warms the air above it. Warm air rises and condenses into cloud particles when reach dew point temperature. The outer edge of the cloud cools, gets heavier and sink to the bottom forming a convection current.
2. Orographic uplifting
3. Convergence of surface air
4. Uplifting along weather front