The Atmosphere The sun’s energy interacts with the atmosphere and the oceans, providing Earth’s climate and weather.

The Structure of the Atmosphere Troposphere Temperatures decrease with altitude 16oC  -60oC

The Structure of the Atmosphere Troposphere The air is warmed by heat radiating from Earth’s surface, the evaporation of water vapor, and water vapor condensing back to Earth. Extends from Earth’s surface upward 12 km (7 miles) and contains 90% of the atmospheric gases.

The Structure of the Atmosphere (cont’d) Stratosphere The tropopause (the dividing line between the troposphere and the stratosphere) occurs where the temperature no longer decreases. Temperatures increase with altitude -60oC  0oC

The Structure of the Atmosphere (cont’d) Stratosphere Contains the ozone layer (O3) that reduces the amount of harmful ultraviolet radiation. Extends from 12 km to 50 km (7-30 miles). Contains 9% of the atmospheric gases.

The Structure of the Atmosphere (cont’d) Mesosphere The stratopause (between the stratosphere and mesosphere) occurs where the temperature stops increasing. The temperature decreases with altitude 0oC  -90oC

The Structure of the Atmosphere (cont’d) Mesosphere There are very few gas molecules, so the pressure is 1/1000th of that at Earth’s surface. Extends from 50 km to 90 km (30-54 miles).

The Structure of the Atmosphere (cont’d) Thermosphere The mesopause (between the mesosphere and thermosphere) occurs where the temperature stops going down.

How you look when you have a new pair of J’s

The Structure of the Atmosphere (cont’d) Thermosphere The temperature increases with altitude -90oC  unknown This is the site of the Aurora Borealis

Composition of Air and Air Pressure Air contains nitrogen (78%); Oxygen (21%); Argon (1%); Carbon Dioxide (0.03%); and Neon, Helium, Krypton, Xenon, and Hydrogen (trace amounts) Water vapor and other contaminants are not included in the composition listed above.

Composition of Air and Air Pressure Air pressure is the force with which a column of air presses down on Earth’s surface. The average atmospheric pressure on Earth’s surface at sea level = 1 atm (atmosphere).