Insolation & temp - chap 4 Flashcards
What drives atmosphere + weather/climate
unequal warming of Earth by SUN
Sun = ultimate source of energy –> nuclear fusion
Type of energy sun provides
electromagnetic radiation (radiant energy)
Inverse Square Law
Energy decreases with distance SO twice distance means 1/4 energy
Earth only receives tiny portion of total solar energy BUT 1 minute of solar radiation hitting earth = humanity’s yearly energy usage
Types of EM radiation
1) Visible: .4-.7 micrometers, 47% solar radiation = visible (ROYGBIV)
2) UV: .01-.5 micrometers, 8% solar radiation, most absorbed in ozone layer
3) .7 to 1000 micrometers, Sun emits near infrared (short waves), Earth emits thermal infrared (long waves)
diff between shortwave and terrestrial radiation
shortwave - visible, UV, IR, emitted by Sun (more energy = more damage)
terrestrial - only thermal infrared, referred to as LONGwave
ten basic heating and cooling processes
1) radiation
2) absorption
3) reflection
4) scattering
5) transmission
6) conduction
7) convection
8) advection
9) adiabatic cooling and warming
10) latent heat
Radiation/emission
process by which electromagnetic energy emitted from object
- hotter object = more intense radiation + shorter wavelengths
all objects emit radiation
blackbody radiator
body emits maximum possible amount of radiation at all wavelengths i.e. sun/Earth
atmosphere NOT blackbody
Absorption
EM waves assimilated into object (absorbed)
- EM waves force electrons/molecules to vibrate more –> increase in internal energy –> increase in temp
good radiators = good absorbers, vice versa
darker object = better absorber
Reflection
bounce back electromagnetic waves
deflects back to space at same angle + initial wavelength
albedo
reflectivity of object/surface as %
Scattering
Deflection + redirection of light waves caused by gas molecules/particulate matter (only changes direction NOT wavelength of energy)
shorter wavelength –> more readily scattered
Rayleigh vs Mie scattering
Rayleigh –> blue/violet scattered most –> why sky blue
Mie –> when lots of suspended aerosols in sky –> even scattering of wavelengths –> sky gray
Transmission
Electromagnetic waves pass completely through medium
*objects vary in how much they transmit (opaque –> less, clear –> more) BUT also in what types of radiation they transmit
ex: glass readily allows shortwave radiation to enter, not longwave to exit so cars get hotter
Greenhouse effect
atmosphere transmits incoming SHORTWAVE radiation from sun but greenhouse gases do not let LONGWAVE TERRESTRIAL radiation transmit out (often re-radiate longwave back to Earth surface –> warms it up)
Keeps troposphere warm –> important for life
Conduction
transfer of heat by contact
- hot molecule agitates cool molecule, increasing its movement + energy; this keeps getting passed along
better conductors - get warmer (conduct heat) faster
Convection
energy transfer from one point to another by vertical circulation of fluids (air/water)
updrafts/downdrafts = example of convection cell
Difference btwn convection + conduction
convection - molecules move from one place to another
conduction - molecules vibrate back + forth –> collisions
advection
advection = movement of fluid horizontally
/_/
/ = convection
_ = advection
adiabatic cooling
AIR RISING
cooling by expansion
- when air rises, it spreads out + average kinetic energy reduced –> temp decreases
adiabatic warming
AIR DESCENDING
air descends –> becomes warmer
- descends –> air is compressed –> work done from compression INCREASES average kinetic energy –> temp rises
latent heat
phase change involving energy exchange
mainly condensation + evaporation
- evaporation: heat absorbed, surroundings cooler
- condensation: heat released, surrounding warmer
Global Energy budget
annual balance btwn incoming + outgoing radiation
Why is there unequal warming by latitude
1) variations in angle of incidence
2) effect of atmosphere on radiation reaching earth
3) variations in day length
angle of incidence
PRIMARY factor determining solar radiation intensity
- more perpendicular –> more heating (hits smaller area, goes through less atmosphere)
high latitudes = lower insolation than tropics
Effect of atmosphere
radiation is reflected, absorbed, scattered by atmosphere
radiation reaching Earth’s surface is 1/2 strong as radiation hitting top of atmosphere
DEPENDS ON:
1) amount of atmopshere
2) transparency of air
Effect of day length
Longer days = more insolation received + more energy absorbed
Latitudinal Radiation Balance
energy surplus in tropics + energy deficit in high latitudes
net energy = 0 so there is balance
Warming of atmosphere
REMEMBER: atmosphere is warmed mainly by energy reradiated and transferred from Earth’s surface NOT by energy received directly from sun
Why does land warm faster than water
1) Specific heat: water’s high specific heat means it requires 5X more energy to increase 1 g by 1 degree than it does for land
2) Transmission: Sun’s rays penetrate water more deeply -> energy is spread out over greater volume in water (more energy spread = slower warming)
3) mobility = convection cells + currents in water mix warm + cool water, increasing time it takes to heat it up
4) evaporative cooling = more evaporation over water than over land = latent heat is constantly lost
Why does water cool slower?
pretty much for same reasons it heats slower
1) high specirfic heat
2) energy stored deeply + brought to surface slowly by radiation
3) cooling surface water continually replaced by warmer water (convection cells)
effect of land/water relationship
major difference between maritime climates + regions far away from water
coastal areas = more mild + smaller temp range
