1. The Atmosphere: Structure and Temperature
STURDIVANT

2. Atmospheric Basics
The atmosphere is a sea of gases, many of which are vital to our existence
What the atmosphere is doing in a particular location at a particular time is WEATHER
What the atmosphere does in general over a region is the CLIMATE
Weather and Climate include air temperature, humidity, type and amount of precipitation, air pressure, and wind speed/direction

3. Atmospheric Composition
The composition of the atmosphere has changed throughout Earth’s 4.6 billion year history
It is thought to have been created by gases released during volcanic eruptions
Data suggests that Oxygen did not appear in the atmosphere until 2.5 billion years ago

4. Atmospheric Composition - Major
The vast majority of the atmosphere is very constant – with 99% of its composition being Nitrogen and Oxygen
Of the remaining 1%, 0.93% is Argon
Despite their abundance, Nitrogen, Oxygen, and Argon play a limited role in weather
Carbon Dioxide makes up roughly % of the atmosphere

5. Atmospheric Composition - Variable
Some components of atmospheric air that vary with time and place are water vapor, dust, and ozone
These variable components significantly affect weather and climate
Water vapor varies from 0-4% of atmospheric volume, and is the source of clouds and precipitation
Ozone exists where sunlight energizes Oxygen molecules enough to combine into O3. Ozone absorbs UV rays that would make our planet uninhabitable

6. Atmospheric Structure
Unlike the ocean boundary, there is no “sharp” boundary to the atmosphere, as it slowly dissipates with height
Atmospheric Pressure depends on the weight of the atmosphere above
Because the atmosphere dissipates with height, atmospheric pressure drops quickly near the surface
Atmospheric Temperature, however, is more complex

7. Atmospheric Temperature
For relatively low elevations in the atmosphere – where humans live – we see temperatures dropping with elevation
This is why we see snow on mountain tops and not in low valleys
We divide the atmosphere into layers of increasing / decreasing temperature
These are the troposphere, stratosphere, mesosphere, and thermosphere

8. Earth-Sun Relationships
The Sun provides all the energy that drives weather patterns on Earth
The amount of time and angle at which light hits the Earth from the Sun determines weather and seasons
Earth both rotates and revolves, creating not only day and night, but seasons as well
Areas more directly facing the Sun see smaller seasonal changes (equator)

9. Heating the Atmosphere
To understand how heat and temperature changes within the atmosphere, we need to first understand HEAT
Heat – transfer of energy due to a temperature difference
Heat can be transferred in THREE ways – Conduction (direct molecule-to- molecule contact), Convection (fluid flow), and Radiation (electromagnetic waves)

10. Solar Radiation
Most atmospheric energy is derived from solar radiation, so it’s important to understand what solar radiation does
When INSOLATION (incoming solar radiation) hits an object, THREE things can happen
Absorption – light is stopped, heats the object
Transmission – light travels through, doesn’t interact with object
Reflection – object bounces radiation back. Some objects absorb radiation then re-emit (reflect) in all directions. This is called Scattering

11. What happens to Solar Radiation?

12. Greenhouse Effect
Gases in the atmosphere that absorb insolation create a Greenhouse Effect
This effect is important to keep our planet warm, but it can also over- warm the planet
Water Vapor and Carbon Dioxide both absorb infrared light, while allowing visible light to pass through

13. What else controls Temperature?
Temperature Control – any factor that causes temperature to vary
Latitude plays the biggest role, in general
Other controls are land vs water cover, altitude, geographic position, cloud cover, and ocean currents

14. Land/Water and Temperature
Land (rock, soil, etc) heats up and cools down much more easily than water.
Thus, we notice areas with more water have smaller daily and seasonal temperature changes
This is why, for example, temperatures in Vancouver, BC are more mild than temperatures in Winnipeg, Manitoba

15. Location and Temperature
Simply being near water doesn’t necessarily affect the temperature significantly
For example, the easterly wind through the United States causes water’s effect to be significant on the West coast, but not so much on the East coast

16. Altitude and Temperature
Within the troposphere, temperature decreases with elevation
This means areas similar in latitude but at different elevations have different annual temperature ranges
Guayaquil and Quito, Ecuador are both near the equation, but Quito lies within the Andes mountains

17. Other Factors
There are a variety of other factors that can affect surface temperatures outside of these
Albedo – fraction of insolation reflected
Areas covered in snow reflect a large amount of light away
Similarly, areas frequented with cloud cover reflect a large amount of light away