6.4

Question 1

what types of molecules trap heat?

Answer 1

2+ atoms (polyatomic)

Question 2

99.9% of molecules in atmosphere don’t absorb IR radiation including:

Answer 2

• N2 = 78%
• O2= 21%
• Ar = 0.9%

Question 3

2 molecular requirements for IR absorption:

Answer 3

1. 1. energy of radiation matches energy of molecular transition (nuclei/electron vibrations)
2. 2. molecular transition (atmospheric molecules) must change electric field (alter molecule’s dipole moment)

Question 4

why does Ar NOT absorb IR?

Answer 4

no nuclei vibrations

Question 5

dipole moment =

Answer 5

(vector sum of atomic charges) * (distance from molecule’s center of mass)

Question 6

why do N2 and O2 NOT absorb IR?

Answer 6

• they have nuclei vibrations BUT
• NO change in dipole moment (bc symmetrical dipole always = 0)

Question 7

all homonuclear diatomic molecules =

Answer 7

infrared inactive

Question 8

homonuclear diatomic molecules

Answer 8

molecule w/ 2 of the same atoms (H2, O2, N2, etc.)

Question 9

all heteronuclear diatomic molecules =

Answer 9

have altered dipole moment = absorb IR

Question 10

heteronuclear diatomic molecules

Answer 10

molecules w/ 2 diff atoms (CO, NO, HCI)

Question 11

polyatomic molecules w/ vibrations that change dipole =

Answer 11

IR active

Question 12

all gasses that contribute to GHG effect =

Answer 12

polyatomic

Question 13

2 most important GHG molecules =

Answer 13

H2O and CO2

Question 14

H2O:

Answer 14

3 vibrations = 3 Δ-dipole

Question 15

CO2:

Answer 15

symmetric = no Δ-dipole
- BUT net Δ-dipole = altered by stretch/bending of vibrations

Question 16

molecular vibrational transitions allow for absorption of …

Answer 16

specific energies

Question 17

rates of rotation

Answer 17

for each vibration, IR photons change rotational levels

Question 18

rotational absorptions = ? and allow for absorption of…

Answer 18

gain/loss of energy during collision
- broad absorption band

Question 19

CO2: bending vibration

Answer 19

14,922 nm

Question 20

CO2: main absorption band

Answer 20

15 µ band

Question 21

1 µ =

Answer 21

1 µm = 1000 nm = 1 x 10^6 m

Question 22

H2O: bending vibration

Answer 22

6269 nm (major absorption band)

Question 23

H2O rotational vibrations =

Answer 23

wavelengths > 20,000 nm

Question 24

why do CO2 and H2O absorb no significant radiation

Answer 24

wavelengths = short

Question 25

atmospheric window

Answer 25

region 8000-12,000 nm where radiation can escape

Question 26

chlorofluorocarbons

Answer 26

polyatomic molecules; major destroyers of stratospheric ozone
- CH4, N2O, O3
- major GHGs

Question 27

CO2 absorptions =

Answer 27

nearly saturated

Question 28

“saturated” absorption

Answer 28

most radiation emitted w/in absorption bands = already absorbed

Question 29

CO2 molecules = contribute __ amnt to total absorption

Answer 29

small

Question 30

CFC molecules = contribute __ amnt to total absorption bc…

Answer 30

large
- they absorb small amnts from window regions

Question 31

1 CFC molecule =___ effect of 1 CO2 molecule

Answer 31

times thousands

Question 32

Beer-Lambert Law:

Answer 32

evaluating UV screening effect of ozone layer

Question 33

any form of radiation passing through absorbing material (beer-lambert equation=…)

Answer 33

T = I/I0 = e-El

Question 34

Beer-Lambert: T =

Answer 34

% transmitted light thru global layer of absorbing gas

Question 35

Beer-Lambert: l =

Answer 35

equivalent thickness

Question 36

Beer-Lambert: E =

Answer 36

absorptivity

Question 37

ozone layer = Δ-transmitted fraction produced by small change in absorbing gas (beer-lambert equation=…)

Answer 37

dT = -e-El dl
- dT = Δ-light

Question 38

Δ-% outgoing IR = __ as ↑ GHG

Answer 38

↓

Question 39

if [initial concentration] = small, [dependence] = __ bc..

Answer 39

linear
- e^-El approaches e^0 =1

Question 40

effect of outgoing radiation/molecule = greatest @ __ concentrations or __ absorptivity

Answer 40

LOW

Question 41

main effects of CO2/H2O added =

Answer 41

↓ transmitted light at edges of absorption bands (E ↓ rapidly)

Question 42

adding molecules found in low concentration =

Answer 42

absorb light in proportion to absorptivity in atmospheric window

Question 43

2 vibrational modes involved in CO2 absorption

Answer 43

asymmetrical stretching + bending = net Δ-dipole = absorbs IR