Atmosphere II : Climate

Question 1

what is climate

Answer 1

average or typical conditions of the atmosphere

Question 2

what are the most common components of climate

Answer 2

precipitation and temperature

Question 3

define proxy measurement

Answer 3

A proxy is an indirect measure of the desired outcome which is itself strongly correlated to that outcome. It is commonly used when direct measures of the outcome are unobservable and/or unavailable.

Question 4

what does climate average out

Answer 4

climate averages out weather, but not season

Question 5

define paleoclimate

Answer 5

a climate prevalent at a particular time in the geological past.

Question 6

do we only have current climate measurements

Answer 6

no we have climate measurements that span modern to past climates (paleoclimate)

Question 7

what are the three ways that energy can be transferred

Answer 7

through radiation, conduction and convection

Question 8

define radiation

Answer 8

transfer of energy as waves or particles through air (emission/transmission)

called electromagnetic radiation

Question 9

what is the electromagnetic spectrum

Answer 9

range of frequencies of em radiation and their wavelengths (or energies)

Question 10

how is the em spectrum seperated into 2

Answer 10

as longwave (low energy) and shortwave (high energy)

Question 11

the energy of EM radiation is inversely proportional to what

Answer 11

wavelength

Question 12

define conduction

Answer 12

heat(energy) transfer from one molecule to next as molecules vibrate

rate of transfer of heat depends on temperature difference (gradient)

e.g. heat moving along a metal bar

occurs in all phases, gas, liquid, solid

Question 13

define convection

Answer 13

transfers of heat by movement of a fluid (mass transfer)

caused by buoyancy forces due to changes in density that arise from changes in temperature

set up convection cells - these present in the atmosphere as turbulence (fluid mixing) or an instability (uneven heating)

Question 14

moist convection leads to…

Answer 14

thunderstorms

Question 15

how do convection cells forms on oceans and land

Answer 15

at night landmass cools quicker than the ocean so creates a cell the other way compared to day time

Question 16

how does convection lead to rainfall

Answer 16

When the land warms up, it heats the air above it. This causes the air to expand and rise. As the air rises it cools and condenses. If this process continues then rain will fall.

Question 17

how does the sun transfer heat

Answer 17

by radiation

Question 18

how does the ground transfer heat

Answer 18

the ground absorbs heat through by conduction, heat moves into atmosphere by radiation

Question 19

how does the atmosphere transfer heat

Answer 19

convection

Question 20

what is earths steady state theory

Answer 20

earths climate system, unperturbed, is in a (quasi-) steady state

energy in = energy out

incoming radiation = outgoing radiation

Question 21

as space is a vacuum, the only form of energy transfer is:

Answer 21

em radiation

Question 22

convection causes what type of cyclone

Answer 22

a low pressure cyclone

Question 23

what is blackbody radiation

Answer 23

a perfect blackbody is an object that absorbs all incoming radiation (that is, none is reflected)

Question 24

radiation emitted by a blacbody depends only what

Answer 24

its temperature

Question 25

what is plancks law about

Answer 25

plancks law of blackbody radiation defines the relationship how much radiation is emitted at a certain wavelength for a body of a certain temperature

Question 26

what is isotropic, what does it mean?

Answer 26

blackbody is isotropic (radiation emitted at equal intensity in all directions)

Question 27

what is radiance

Answer 27

power emitted by a blackbody (w/m^2/sr) sr = ser radian

Question 28

what is spectral radiance

Answer 28

radiance per unit frequency (w/m^2/sr/Hz)

Question 29

what waves are radiation from the sun

Answer 29

shortwave (UV/visible)

Question 30

radiation from the earth is...

Answer 30

longwave (infrared)

Question 31

the emission of radiation from the sun and earth...

Answer 31

hardly overlap

Question 32

what is the Stefan-Boltzmann law about

Answer 32

power radiated from a blackbody in terms of its temperature

Question 33

how to go from kelvin to degrees celsius

Answer 33

k = degree Celsius + 273.15k

Question 34

what is stefan-boltzmann law

Answer 34

total energy radiated per unit surface area of a blackbody is proportional to T^4 this relationship integrated in all directions over a hemisphere and over all frequencies is: I = sigma x t^4 where sigma = 5.67 x 10^-8 wm^-2k^-4 is the stefan b constant I = the blackbody irradiance or energy flux density

Question 35

what is a radiation modifier example

Answer 35

albedo and transmittance

Question 36

what is albedo

Answer 36

symbol alpha, a, it is the ratio of reflected radiation to incident radiation (incoming light striking a surface) 0 < a < 1

Question 37

what is transmittance

Answer 37

transmittance, gamma, y, is the ratio of transmitted radiation (radiation that passes through a fluid) to incident radiation: 0 < y < 1

Question 38

what is a grey body

Answer 38

a grey body is a body that emits according to plancks formula multiplied by fractional emissivity, epsilon, E 0 < E < 1

Question 39

tell me what the emissivity value means

Answer 39

where E is a measure of efficiency of emitting thermal radiation (0 for a shiny object, 1 for a blackbody)

Question 40

what is the global albedo

Answer 40

earth is not a perfect blackbody, clouds, ice, reflective land surfaces like deserts increase a and reduce E earths colour varies from white to deep blue (nearly blue)

Question 41

what are the albedo properties of the earth

Answer 41

water = near perfect blackbody snow = very reflective albedo varies as a function of properties of surface (land/cloud) the ocean albedo depends on the angle of the solar radiation striking the surface (sun glint) the albedo of bare sea ice depends on the density of the air bubbles earths global average = 0.3

Question 42

tell me about the global mean energy model (incoming radiation)

Answer 42

energy of incident shortwave solar radiation (solar constant) S(subscript 0) = 1366 w/m^2 s0 = incident solar radiation

Question 43

how do we calculate the global mean energy model (outgoing radiation)

Answer 43

energy of sun incident on earth = epsilon s0 /4 area of the earth the sun intercepts = pi x r^2 fraction of solar constant received by earth = pir^2/4pir^2 = s0/4 = 342 w/m^2 E = 1 - alpha = 0.7

Question 44

how can we integrate global mean temperature and the energy of a blackbody

Answer 44

the energy of blackbody is proportional to its temperature E(out) = sigma x t^4

Question 45

tell me about the penetration of radiation on the atmosphere

Answer 45

majority of shortwave penetrates the atmosphere, very little longwave escapes

Question 46

what are the natural greenhouse gases:

Answer 46

water vapour, co2, oxygen and ozone, methane, nitrous oxide

Question 47

what is the chemical symbol for methane

Answer 47

methane = CH4

Question 48

what is the chemical symbol for nitrous oxie

Answer 48

N20

Question 49

what is the grey atmosphere

Answer 49

gray atmoshpere is transparent in shortwave and includes a layer of infrared absorbing gases that intercept outgoing longwave radiation

Question 50

tell me about uneven heat in the world and its redistribution

Answer 50

equator gets more sun radiation than the poles, uneven heating. redistribution of heat: convection plays a role not as simple as Hadleys 1735 suggestion that convection cell extends from equator to the poles redistribution does not account for coriolis effect

Question 51

tell me about tropical Hadley cells

Answer 51

sun heats equator hot air rises air masses move towards poles air masses diverge from north-south path due to coriolis effect cool dry air sinks at about 30 degree latitude (deserts) still named hadley cell

Question 52

air rising (convective uplift) is associated with...

Answer 52

clouds and rain (tropical rainforests)

Question 53

air sinking (subsidence) associated with...

Answer 53

dry air (deserts)

Question 54

tell me about convective cells

Answer 54

moist, warm air rises forming clouds | cold, dry air subsides (compresses and warms)

Question 55

tell me about surface winds bestie

Answer 55

descending branch of cell reaches surfaces, forms surface winds that diverge due to Coriolis effect poleward and equatorward winds meet, air forced upward, maintains convective cells.

Question 56

tell me about annual mean surface temperature

Answer 56

warmest at the equator coldest at the poles Antarctic colder than arctic (isolated less land mass to redistribute head) colder at elevation canada colder than europe

Question 57

where does rain occur

Answer 57

most rain in intertropical convergence zone (ITCZ) (convective uplift) little rain at edge of tropics ~ 30 degrees north (subsidence) more rain over equatorial oceans = storm tracks

Question 58

why are circulation patterns not always stable

Answer 58

``` seasonal variation interannual variability north atlantic oscillation el-nino southern oscillation extreme weather longer-timescale variability (not the focus of this module) ```

Question 59

tell me about earths seasons

Answer 59

earth is tilted at an angle of 23.5 from its orbital plane different parts of the earth receive the suns most direct rays when north pole tilts toward the sun, it is summer in the northern hemisphere when south pole tilts toward the sun, its winter in the northern hemisphere