EESA09H3 Lecture Notes - Lecture 3: Ozone Depletion, Thermocline, Atmospheric Circulation
1 Jun 2018
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Wind
EESA09- Lecture 3- Global Wind Circulation
From lecture 2: ✰Vertical Structure of the Atmosphere
❖Troposphere
❖Stratosphere
❖Mesosphere
❖Thermosphere
⭐Important to understand for midterm and final:
1. Warm air rises and cool air sinks
2. Cooling of air causes condensation
a. This is what causes clouds to form
*Whenever air begins to sink, it is related to centers of high pressure and whenever air begins
to rise, there is a belt of low pressure.
Global Circulation:
There are three categories of atmospheric wind circulations that transport heat from the
tropical latitudes to the polar latitudes.
1. Global- 10,000’s of km
2. Synoptic- 100’s to 1,000’s of klm
3. Small scales- <100 km
➢There is more energy released
in the polar regions than is received from the sun and the
opposite is true for the equatorial region.
○In other words, the equatorial region receives a lot of energy which is then
shifted with wind towards the poles, and radiation is released from the poles.
○Wind controls the entire globes circulation.
Wind
One Cell Theory: This cell was first introduced by a meteorologist named George Hadley
1685-1768. When warm air from the equator rises and moves towards the poles, it begins to
cool and sinks at the poles. One hadley cell according to this theory extends from 90 degrees
North to the equator, and the other cell extends from 90 degrees South to the equator.
However, this theory suggests that 30 degrees from the equator is where all the heat is
concentrated but this is not the case as Toronto experiences warm summers when it is above
30 degrees.
Heat can be transported in the atmosphere through different methods:
Sensible heat: heat that you can sense or feel
Latent heat: heat that is absorbed by water vapor during evaporation, or the heat that is
released when water is condensed.
- Heat is exchanged when there is a phase change
According to the one cell theory, energy in the form of heat is transported in the form of
sensible heat and latent heat.
- Due to the Earth’s rotation, it impacts the moving object by deflecting its path called the
Coriolis effect. This Theory cannot explain the Coriolis effect so this is another reason
why the theory cannot be accepted.
★Summary of why the One Cell Theory cannot explain the Earth’s global wind circulation:
○The Coriolis Effect cannot be explained as there is no rotation of the Earth
○The fact that the Earth’s tilt causes the seasons to change cannot be explained
○Continentality causes the land and sea to vary in its thermal inertia
Three Cell Theory: This cell divides the movement of the wind into three sections.
➔Hadley Cell: This cell covers the latitudes from 0 degrees to 30 degrees North or South.
In the Hadley cell, hot air rises at the equator and begins to cool/sink around 30 degrees
latitude.
➔Ferrel Cell:Named and discovered after William Ferrel (1817-1891)who was an
American meteorologist. This cell exists between the latitudes 30 and 60 degrees (North
Document Summary
From lecture 2 : vertical structure of the atmosphere. Important to understand for midterm and final: warm air rises and cool air sinks, cooling of air causes condensation, this is what causes clouds to form. *whenever air begins to sink, it is related to centers of high pressure and whenever air begins to rise, there is a belt of low pressure. There are three categories of atmospheric wind circulations that transport heat from the tropical latitudes to the polar latitudes: global - 10,000"s of km, synoptic - 100"s to 1,000"s of klm, small scales - <100 km. There is more energy released in the polar regions than is received from the sun and the opposite is true for the equatorial region. In other words, the equatorial region receives a lot of energy which is then shifted with wind towards the poles, and radiation is released from the poles.
