Atmospheric Composition
What two gases make up 99% of Earth’s atmosphere?
Nitrogen (78%) and Oxygen (21%)
Which layer is where all weather occurs?
Troposphere
What protects Earth from harmful UV radiation?
The Ozone Layer
What is the term for incoming solar radiation?
Insolation
On which dates is the sun directly overhead the equator, giving 12 hrs of day/night everywhere?
Equinoxes (Mar 21 & Sep 22)
Which gas is 0.042% of the atmosphere but critical for climate regulation?
Carbon Dioxide (CO₂
Where do auroras occur?
Ionosphere
Which atmospheric layer absorbs cosmic rays, gamma rays, and X-rays?
Ionosphere
Earth is farthest from the Sun on which date?
July 4 (Aphelion)
On which date is the Northern Hemisphere tilted maximally toward the Sun?
June 21 (Summer Solstice)
What inert gas makes up 0.9% of the atmosphere?
Argon (Ar)
Which layer contains the ozone layer?
Stratosphere
What process breaks apart O₂ molecules so ozone can form?
Photodissociation
Earth receives how much of the Sun’s total energy output?
One two-billionth
What are the five reasons for the seasons?
Revolution, Rotation, Tilt, Axial Parallelism, Sphericity
What term describes the part of the atmosphere where gases are evenly mixed?
The Homosphere
Which layer has the coldest temperatures in the atmosphere?
Mesosphere
What international agreement phased out CFCs to protect the ozone?
The Montreal Protocol
What is the solar constant (average insolation at Earth’s top atmosphere)?
~1372 W/m²
On which date is Earth closest to the Sun?
January 3 (Perihelion)
What term describes the part of the atmosphere where gases are sorted by atomic weight?
The Heterosphere
Which layer has very high temperatures but little heat due to low density?
Thermosphere
One chlorine atom can destroy about how many ozone molecules?
100,000
At what temperature does Earth radiate most of its energy?
~288 K (15°C or 59°F)
At what latitude is the sun overhead during the Northern Hemisphere summer solstice?
Tropic of Cancer (23.5°N)