1. The Atmosphere & Climate
Lecture #1
The Atmosphere & Climate

2. The Atmosphere and Climate
Weather - daily temperature and moisture conditions in a place
Climate - a description of the long-term weather pattern in a particular area

4. The Atmosphere and Climate
Troposphere
Ranges in depth from 18 km over the equator to 8 km over the poles.
All weather occurs here.
Convection currents redistribute heat and moisture around the globe.
Air temperature drops rapidly with increasing altitude.
Tropopause - transition boundary that limits mixing between the troposphere and upper zones

5. The Atmosphere and Climate
Stratosphere
From tropopause up to about 50 km
Has almost no water vapor, but 1000X more ozone than the troposphere
Ozone absorbs ultraviolet light, which warms upper part of stratosphere.
Ozone protects all life on Earth since UV radiation damages living tissues.
Ozone being depleted

6. The Atmosphere and Climate
Mesosphere
Middle Layer
Thermosphere
Begins at 80 km
Ionized gases and high temperatures
Lower thermosphere has ions which are struck by high energy radiation.
Aurora borealis (northern lights)

8. Energy and the Greenhouse Effect
Of the solar energy that reaches the outer atmosphere:
About one-quarter is reflected by clouds and the atmosphere.
Another quarter is absorbed by carbon dioxide, water vapor, ozone and a few other gases.
About half reaches the earth’s surface.

9. Energy Balance

10. Energy and the Greenhouse Effect
Surfaces that reflect energy have a high albedo (reflectivity).
Fresh clean snow %
Surfaces that absorb energy have low albedo.
Dark soil 3%
Net average of earth 30%
Absorbed energy evaporates water and runs photosynthesis. Absorbed energy released as heat.

11. Energy and the Greenhouse Effect
Most solar energy reaching the Earth is near infrared (short wavelength).
Energy reemitted by the earth is mainly far infrared radiation (long wavelength, heat)
Longer wavelengths are absorbed in the lower atmosphere, trapping heat close to the earth’s surface.
Greenhouse Effect
Atmosphere transmits sunlight while trapping heat.

12. Greenhouse Effect
Gases in the atmosphere, especially carbon dioxide and water vapor, are the substances that retain heat.
Burning fossil fuels releases extra carbon dioxide.
Deforestation destroys carbon sinks.
Positive feedback loop - poles covered with ice reflect solar radiation back into space. Now that ice is melting, open water is absorbing more heat, which in turn is melting more ice, leading to more warming.