Lecture 19: Atmosphere Part 1 Flashcards
-The Atmosphere and How it Evolved -Composition and Structure of the Atmosphere -The Greenhouse Effect
What is the atmosphere?
It is a gaseous envelope that surrounds a celestial body.
What elements/compounds made up the atmosphere of early Earth (Hadean)?
Hydrogen, Helium, Methane, Ammonia, and Water.
How did Earth’s secondary atmosphere get formed?
Volcanic outgassing released volatiles to the surface.
How did early Earth’s atmosphere get oxygen in it (Archean to Proterozoic)?
Traces of oxygen would have been formed by ultraviolet light breaking down water. Larger amounts would have been formed by the process of photosynthesis by cyanobacteria.
What is temperature?
A measure of the average kinetic energy of molecules.
What is heat?
The total kinetic energy of all molecules in a substance.
Which layer is the troposphere and how is it heated?
It is the first layer of the atmosphere and is primarily heated through energy transfer from the Earth’s surface, thus the base of the troposphere is typically the warmest.
What is the tropopause?
The of surface of the troposphere and its height varies with latitude.
Which layer is the stratosphere, does its temperature increase or decrease upwards and why?
The second layer, extends from the top of the troposphere. Its temperature increases upwards due to the absorption of solar UV energy by ozone.
What is the stratopause?
The upper boundary of the statosphere.
Which layer is the mesosphere, does its temperature increase or decrease upward and why?
The third layer, above the stratosphere. Its temperature decreases upward due to the atmospheric particles being widely spaced and no ozone to absorb solar energy.
What is the mesopause?
The upper boundary of the mesosphere.
Which layer is the thermosphere, does its temperature increase or decrease upward and why?
The last layer, above the mesosphere. Its temperature increases upward due to it being directly exposed to the Sun’s radiation.
Why does the thermosphere feel so cold?
Because the atmospheric density is so low which causes heat content to be also very low. (great example of how heat and temperature are different)
What is the ionosphere and what happens here?
It is a region above the thermosphere where high-energy photons strip electrons from atmospheric gas molecules, causing them so become ionized. This leads to the Aurora Borealis.
What gases make up the modern atmosphere?
- Nitrogen, Oxygen, Argon, Water vapor
- Traces of Carbon Dioxide, Ozone, and Methane
What aerosols make up the modern atmosphere?
-Water droplets, ice particles, solid particles (dust, salt, and carbon from fires)
How does the greenhouse effect work?
Some of the infrared radiation passes through the atmosphere but most is absorbed and re-emitted in all directions by greenhouse gas molecules and clouds.
-The effect of this is to warm the Earth’s surface and the lower atmosphere.
How is adding Carbon Dioxide to the atmosphere an example of a positive feedback loop?
Adding carbon dioxide to the atmosphere tends to warm the atmosphere, causing global warming. The warm atmosphere causes surface water to evaporate and become water vapor. Since water vapor is a greenhouse gas, the atmosphere tends to warm even more as the water vapor increases.
How is adding Carbon Dioxide to the atmosphere an example of a negative feedback loop?
Adding carbon dioxide to the atmosphere tends to warm the atmosphere, causing global warming. The warm atmosphere causes surface water to evaporate and become water vapor. Some water vapor condenses to form clouds. Cloud contribute to the greenhouse effect by trapping heat in the atmosphere, but they also reflect solar energy back to space, helping cool the planet.
