atmosphere 1

earths first atmosphere

(4.0-3.8 Ga) proto-atmospheric He and H2 were removed and slowly replaced with gases from volcanoes, comets and meteorites: CO2, H2O, N2, NH3, CH4. differentiation of Earth’s layers helped develop the magnetic field, which aids in retaining light gases

earths second atsmosphere

(3.8- 2.7 Ga) gradually evolved into domination by N2 and CO2, H2O (settled into liquid), and NH3 (dec from UV rays, dissociating it). conc dropped. CO2 also begins to decrease as newly formed carbonate traps it in rocks

earths third atmosphere

(2.7-0.8 Ga) N2 and trace O2 were a result of cyanobacteria that had recently evolved to perform oxygenic photosynthesis, allowing the release of O2 into the water and atmosphere. banded iron formation and O2 budget inc .

stromatolites

rock-looking mounds that are many many layers of fossilized algae and bacteria

Great Oxidation Event (GOE)

occurred from algae and bacteria developing oxygenic photosynthesis during 2.7-0.8 Ga

earths current atmosphere 

(0.8Ga-present) O2 levels between 15% and 35%. ozone (O3) layer is formed, 

air density 

the total  mass of gas molecules per unit of volume 

heat

total kinetic energy of all atoms or molecules in a substance

temperature

The average kinetic energy of individual atoms or molecules in a substance

radiation

a way heat energy is transferred, transported by electromagnetic waves, does not require a medium to transfer.  

conduction

a way heat energy is transferred, transferred through matter and molecular collisions, moving in direction of higher T to lower T

convection

a way heat is transferred by mass movement of circulation in a substance, important for global heat transfer as convection occurs in the atmosphere

troposphere

lowest layer, 10-15km, dec in temperature with inc altitude, where major weather phenomena occur, where clouds are formed. hot air near the earth’s surface rises, and cool air sinks, promoting convection. 

tropopause

What separates the troposphere and the stratosphere, while in the troposphere T dec w altitude, T dec stops in tropopause

stratosphere

relatively const T for the first 10km, then a gradual inc in T untul 47km. this is bc it holds majority of O3 whihc absorbs UV radiation from the sun.

stratopause

separates stratosphere and mesosphere, max T of 0 C

mesophere

gradual decrease in T with inc Altitude, 47 to 82km. T drops to -85 °C at the top. lower capacity to absorb solar energy.

thermosphere

no clearly defined top, can extend from 82km to 1000km. T inc w altitude since N2 and O2 absorb short-wave solar rad. very few g molecules in this layer. (less than 1% of atmospheric g)

exosphere

The gradual transition from top of thermosphere into space starts at 500-1000 km and continues until 10,000km, until gas conc of the atmosphere is same as space.

homosphere

includes the troposphere, stratosphere and mesosphere. Atmospheric gases in the area are dense enough to collide with each other, which allows them to remain well mixed.

heterosphere

the transition into the thermosphere and all above where the density of atmospheric gases dec to the point of not being able to mix. seperate into sphericla layers (heaviest to lightest) N2-O2-He-H

ionosphere

an area spanning from a little before the mesosphere to the thermosphere where high energy, short-wave solar rad can strip electrons from N2 and O2to form positively charged ions. 

rules of em radiation

1. All objects above 0k emit radiation

2. Hotter objects radiate more total energy per unit than colder objects

3. Hotter objects radiate more of their energy as short-wavelength radiation than cooler objects

   1. All objects that are good absorbers of radiation are also good emitters

what can happen to solar radiation

absorbed, transmitted, redirected or reflected

reflection of solar rad

a way solar energy is redirected in which it is bounced back from an object at the same angle as the ray and at the same intensity.

albedo

The amount of rad reflected back from a surface

scattering of solar rad 

a way solar energy is redirected in which an incoming ray is split into several weaker rays traveling in mostly forward but many directions. 

absorption of solar rad

~47% of incoming solar rad is absorbed by the Earth’s surface. earth absorbs short wave radiation and converts it into long wave radiation that we feel as heat.

explain greenhouse gas effect 

Solar rad passes through Earth’s atmosphere, which is then absorbed, and re emitted by the Earth. a partial amount of the original rays from the sun is trapped in the atmosphere that heats the earth, but not to an extreme.