Lec 3

What is the driver of energy on Earth?

• radiation from the sun

• Sun is primary source of energy 

  • In form of radiation (form of energy that travels in a form of wave (electromagnetic wave)) 

What is radiation?

• Energy comes in waves and diff types of radiation 

  • Radiation: electromagnetic radiation that comes in based on wavelength onto the earth 

    • Most Shortwave radiation because sun in hot (ex: UV radiation) 

    • Also some visible spectrum, infrared spectrum 

  • Sun is pushing energy for processes 

• Traveling of radiation doesn't require any matter -> radiation from sun can travel large space to get to Earth 

What are the main drivers of spatial and temporal variation of the energy received from the Sun?

• Seasons

• Latitude

• Clouds

• Surface characteristics (ie reflectance)

How do seasons impact spatial and temporal variation of energy from the sun?

• Tilted and spinning Earth with orbit 

• Diff seasons -> more or less input of solar energy  

• Orbit: 

  • Sun closer to Earth -> more radiation will reach with less distance (more energy hitting Earth) 

How does latitude impact spatial and temporal variation of energy from the sun?

• How sun strike Earth 

  • 90 degree angle -> more energy absorbed by earth 

  • Shallow angle -> reflected more to space -> less energy absorbed 

• Equator: more direct pathway for sun 

• Pole: 24 hr of light during summer, 24hr darkness in winter 

How do clouds impact spatial and temporal variation of energy from the sun?

• Cloudy day: not as much solar radiation 

• Clear: lots of solar radiation 

• Clouds can separate energy -> less reaches Earth 

How does the surface impact spatial and temporal variation of energy from the sun?

• Color of surface, texture -> influences how much energy is absorbed to Earth's surface 

• More energy reflected -> less energy absorbed 

What is Planck’s law?

• the wavelength of the energy emitted by a surface decreases as its temperature increases

• Energy comes in waves 

  • When waves are closer together = shorter  

    • Hotter (lambda is smaller) -> the shorter the wavelength the hotter it is 

  • Waves farther apart = longer waves 

What does a hotter surface mean?

• The hotter the surface -> the shorter the wave length at which the emission of energy happens 

  • Ex: sun is hot -> emitting energy at shorter wave lengths than the energy the Earth is emitting 

What is Wien’s displacement law?

• calculates the wavelength at which maximum energy radiation occurs, given a specific surface temperature.

• Calculate at what wavelength the object has a max radiation emission 

• 
  

  

What is a wavelength?

• When object emits radiation -> spectrum of radiation with many diff wave lengths 

  • Wien 

    • All bodies emit energy in a spectrum  

What is a wavelengths max energy radiation?

• Lots of other wavelengths, but wavelength max is the most dominant/frequent

  • (highest energy wavelength in this spectrum of emission) 

• Seen the most in the middle -> wavelength being predicted as max emission by Wien 

• Emissions happening at other wave lengths , but weins predicts wavelengths associated with peak of bell curve 

• Average is 6000 K 

• 2897/6000 = 0.5 weirdMm  

  • Wavelength of max emission  

What are the parts of the electromagnetic spectrum?

• Infrared longer  

  • Eye cannot process it 

• UV shorter 

  • Eye cannot see it 

• Visible spectrum  

  • Reds are longer 

  • Violets are shorter 

Where is the un on the electromagnetic spectrum?

• Sun 0.5 is in the UV -> blue green visible -> can see the light 

  • Most things that drive Earth for energy sense is UV and infrared 

• Short and long wave length are relative -> relation is referring to Earth and sun radiation 

What is insolation?

• Insolation is energy received from the Sun (INcoming SOLar radiATION).

• Insolation is “shortwave” radiation

  • All insolation is shortwave radiation 

  • Only the sun radiation is shortwave 

What are shortwave radiation inputs?

• Ultraviolet light (UV) shorter

  • shorter

• Visible light

• Near-infrared wavelengths

  • longer

• Mostly UV 

• All three types together = solar radiation 

  • All short though because they all are from the sun 

• 2897/290 = 10 mm 

  • More in the infrared area 

  • 290 – 273.15  

• Higher wavelength = lower energy 

• 10 nm is in infrared range -> cannot see any visible light 

What is energy taken by the Earth?

• Insolation that is not reflected by the Earth’ s surface is absorbed.

• Constantly getting short wave radiation from sun towards Earths surface 

  • Most getting reflected, but some are absorbed at surface 

What happens when the Earth absorbs energy?

• Once this shortwave radiation is absorbed, it may later be emitted as an energy output.

• Earth emits energy according to its own temp 

  • Reflectance goes off with the same energy 

  • When absorbed 

    • Earth is cooler -> emitted at a much longer wavelength 

• Absorbed energy is being used earth surface to heat it up 

  • Energy not reflected back to space 

• Energy absorbed will be emitted back into space, but now long wave 

  • Go back to weins law 

  • Earth is much cooler than sun -> T is smaller -> longer wavelength radiation

Sun energy vs Earth energy

• Sun Energy = emits shortwave

• Earth Energy = emits longwave

What waves come into Earth?

• Waves go up and down at higher frequency than long waves 

• Short coming in  

  • Most is caught up in clouds, space,  

  • About half from sun is being absorbed by Earths surface 

• Sun puts in short 

  • Some is reflected to space 

  • Some is absorbed 

  • Some hits clouds (gas particles) -> reflected back to space 

  • Some hit gases in atmosphere

What happens to waves that hit clouds?

• Photon hits particles -> reflected in all directions -> some of the photons are reflected back to space and some are reflected to surface of Earth (diffuse radiation form the sun)  

  • Less intense, but is incoming radiation from sun to Earth 

What happens to waves that hit gases in the atmosphere?

• Gases in atmosphere (ex: water vapor, CO2 (global warming)) 

  • More GHG in atmos -> gases absorb some long wave -> some gases emit back to space 

  • Some of the gases point them back down Earth  

    • Waves emitted back towards Earth are based according to their temp 

    • Gas temp is cooler -> emits long wave back to Earth surface 

    • Creates trapping of energy in the near surface -> Greenhouse effect 

What happens to the waves absorbed by the Earth?

• Half absorbed -> Earth starts to emit energy back towards space as long energy 

• Warm earth will emit LW radiation back to atmosphere 

  • Some of LW goes to space 

  • Most is absorbed by GHG in atmos 

What causes global climate change?

• Global climate change: positive feedback mechanisms of the greenhouse effect (acceleration, more trapping of energy)  

• Need greenhouse effect for Earth to be habitable  

  • But acceleration of greenhouse effect is causing climate change 

• GHG warms up -> reemit back towards Earth -> traps most of the energy near surface of Earth -> keeps it warm and livable = greenhouse effect 

• Global climate warming is not because of greenhouse effect 

  • Human activity release excess GHG -> more energy trapped near surface -> temp increase more 

What is Stefan-Boltzmann Law

• describes the RATE at which energy is emitted from a substance

• Wats per meter square of energy emission  

  • Watt: joule (energy ) per second -> gets a rate  

  • J/s -> makes Qr a rate instead of a value 

  • How quickly a body can emit energy 

• How much of that energy is coming onto or how much energy is emitted a meter square area 

What is emissivity?

• How effectively a object can emit thermoradiation (energy) 

• Effiency of energy emission 

• Only thing in our system as perfect emitter of energy (black body) = Sun  

  • Emissivity of 1.0 = perfect emitting substance 

    • Object has ability to emit thermoradiation 

    • Everything else not: ex: water has 0.95 

  • The Earth has less etc (lec dude said the Earth also is a black body??) 

What is the solar constant?

• The sun’s energy arrives at the outer edge of the atmosphere at an average rate of: 1.74 x 10^17 W

  • total energy

• This, divided by the area of the earth (1.28 x 10^14 m^2 ) is 1367 W m^-2 = solar constant (Isc)

• Isc = 1367 W m ^-2

  • At every scale meter -> energy received from the sun is 1367 Watt in one second 

How does Isc vary?

• Only average at surface  

  • At center -> more energy 

  • At edge -> less energy 

What is true of energy coming into the Earth and exiting it?

• 100 = 100 % of solar constant  

  • = sum of reflected and outgoing radiation from the Earth 

    • 6+20+4+6+38+ 26 = balance of energy 

  • Outgoing energy includes energy being used by life 

• Incoming and outgoing energy is equal 

What happens to incoming radiation?

• 100% incoming solar radiation -> partially reflected to space or backscattered to space 

  • Some is absorbed by clouds  

  • Some gases and particles by atmosphere 

  • About half strikes Earth 

• 50% of incoming is absorbed by surface -> used to heat up Earths surface 

How much of the incoming radiation is reflected back to space?

• How much energy is left at surface 

  • Reflected portion of incoming radiation is 30% (abt 30% of insolation is reflected back to space)  

What would happen if the Earth kept accumulating energy?

• If half of the energy kept accumulating energy -> the Eart would be too hot and explode 

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What happens after the Earth absorbed the energy?

• Warm earth surface remit LW back to atmos 

  • Some go to space directly 

  • Most absorbed by GHG 

    • Some absorbed by GHG go back to space 

    • Most remitted to surface of Earth (greenhouse effect) 

      • Net radiation emission by GHG by long wave 

  • Net sensible heat flux

  • net latent heat flux

• Absorb radiant energy -> then gets used so Earth doesn’t continually heat up 

What is net sensible heat flux?

• Sensible heat flux keeps the temperature warm 

What is latent heat flux?

• Energies running hydrological cycle by breaking hydro bonds  

• Most dominated heat emitted by Earth and used by hydro 

• Used to evap water on Earth 

  • Absorb energy from air -> doesn't change temp of water, it breaks hydro bond -> water molecule is stretching -> evaporates 

What is the dominant energy for hydro processes?

• net sensible heat flux

• latent heat flux

What is causing climate change?

• Larger amount of net absorption by GHG -> little more energy that is being accumulated 

What is albedo?

• Albedo: how much sunlight is reflected back to the atmosphere/space 

What is reflection?

• sunlight is being reflected directly from surface without changing wavelength 

What is remission?

• solar radiation is already absorbed by an object -> temp change by the object -> the object remits LW back to space 

  • Wavelength of insolation has already changed 

What is the equation for albedo?

• Kup: radiation reflected back to atmos 

• Kdown: solar radiation from the sun 

• K = shortwave radiation 

What affects albedo?

• color of surface

• How the sun strikes the surface (angle)

• Roughness of surface

How does color impact albedo?

• Fresh snow: 8—95% of insolation is reflected back to space 

  • High 

  • Light colored 

• Asphalt: 5-10% -> absorb most of the sunlight 

  • Darker 

  • Less albedo 

How does the angle impact albedo?

• Hit equator -> steeper angle  

  • Stone will sink 

  • Absorb more energy -> Less albedo 

• Polar area -> weaker angle (smaller angle) 

  • More reflected -> More albedo 

  • Ex: skipping rocks 

How does the roughness of the surface impact albedo?

• Snow/icy -> very smooth -> all light reflected to one direction  

  • Predictable  

  • Albedo higher 

• Rough snow (grass) 

  • Incoming sunlight reflected to diff direction -> reduce how much sunlight reflected to atmos -> smaller albedo  

What is albedo’s short wave radiation?

• Albedo is shortwave radiation ONLY

• Albedo: Outgoing wavelength same as incoming wavelength

• Not albedo: Outgoing wavelength different from incoming wavelength

  • ex: the outgoing longwave radiation that is emitted (not reflected) from a surface is not part of albedo

How to measure albedo?

What device measures albedo?

• Albedo meter 

  • Both sensors are connected to own reading  

  • Upward 

    • Receive downward radiation 

  • Downward 

    • Receive upward radiation from ground 

    • Smaller than upward 

      • Albedo has to Be less or equal to 1 

      • Less than incoming radiation 

What is the radiation balance (Q*) equations?

• How much energy is available for hydrological processes 

  • SW and LW –> no other processes 

• Balance = net coming in and net going out 

  • Short wave coming in and out 

  • Long also coming and out 

What is K*?

• Net short wave

• incoming – how much reflect out to space via albedo 

What is L*?

• Net long wave (L*) 

  • Coming out (temp of earth, stefen bolz equation, Emison of longwave radiation from cool earth) 

  • Coming in – coming out 

  • Coming in 

    • Only source is function of GHG 

    • Radiation being absorbed from GHG and then remitted back towards surface of Earth 

  • Emission coming back towards earth – emission going out 

What does K equal?

• K = aK 

  • Outgoing short wave = albedo(incoming short wave) 

What is net radiation (Q*)?

• Net short wave + net long wave = net radiation (Q*) 

  • Wats per meter squared  

  • Q= (Kdown – Kup) + (Ldown – L up) 

    • If Q is negative -> losing energy from Earth 

      • Usually at night because of no solar input -> no ouptut 

        • Only LW from Earth and gases 

        • K= 0 at night - (Greater Lup than Ldown) -> negative 

What is Q* when Kdown= 200 W m^2, K up = 50 W m^2 , Ldown = 50, and Lup =70?

• Kdown= 200 W m^2 

• K up = 50 W m^2 

• 200 – 50 = 150 W m^2 of solar radiation input at certain time of day 

 

• Ldown (from GHG to surface) = 50 

• Lup (Earth to atmos) = 70 

• Q* = 150 + -20 = 130 

  • During point at the day -> net energy balance of 130 W m^2 -> earth is gaining energy  

    • Energy can be used to evaporate water, make you feel warmer 

How does incoming short waves look throughout 24hrs?

• Short wave peak at noon -> no short wave received at surface in at night (0 watts per m squared) (yellow) 

  • Insolation (also including those reflected by to space) 

  • Kdown (SWdown)= insolation 

  • Peaks at noon and decrease until evening 

  • No solar radiation at night  

How does outgoing short waves look throughout 24hrs?

• Shortwave coming out is smaller proportion of SW (red) (Kup) 

  • Also zero at night 

  • Function of albedo  

  • Relatively predictable in relation to SW coming in  

  • Shortwave reflected by surface back to atmos/space 

  • No input -> no reflection (only in day time) 

    • Negative =  direction 

      • Losing energy from earth and going into atmos 

      • As it gets deeper -> energy that Earth is losing increases 

How does outgoing long waves look throughout 24hrs?

• Long wave coming out (green) leaving Earth (green) 

  • Negative denotes direction that LW is coming form surface of Earth back towards space 

  • Less LW emitted at night because temp are lower with no incoming solar radiation  

  • min at afternoon when things get warmers 

  • At night -> amnt of outgoing LW goes down 

  • Noon: hotter -> surface heated up by sun -> more insolation -> more energy output from earth 

  • As K decrease -> LW are decreases 

How does incoming long waves look throughout 24hrs?

• Incoming LW (blue)  

  • Stable at day 

  • bump at early night because of accumulation of energy as sun is getting ready to set/after it sets (increasing water vapour at sunset) 

  • Energy going back down to ground emitted by GHG 

How does net radiation look throughout 24hrs?

• Net radiation (orange) = Q*

  • Follows incoming SW 

    • Short income radiation, insolation, incoming Sw all the same?? 

  • Rate becomes negative (loosing overall net radiation) at night 

    • Loss of LW radiation more than incoming LW at night 

  • Day time increases and peaks at noon  

  • During night: No insolation, but has some LW output  

    • LW output from Earth is greater than the LW down emitted from GHG 

      • Lose some energy during night time until sunrise 

    • With accelerated Greenhouse effect 

      • More GHG -> More LW remmited back to surface -> origin line can be higher than zero -> energy is not losing any energy -> its trapping more energy on surface -> temp inc more  

How is energy mostly used?

• Losses at night are not equal to gains at day 

  • Energy is used mostly in sensible and latent energy ??

What can happen to the Q*?

• Q* is the net amount of energy at the earth’s surface → this energy can be “transferred” or moved by several processes.

  • Q* can be transferred, used, or moved around  

    • Ex: by wind 

• By:

  • Conduction

  • Convection

  • Advection

What is conduction?

• molecule-to-molecule transfer of heat diffusing within a substance (i.e., coffee warmth to the outside of a cup) (only solids)

• Energy moved around in conduction  

• Movement caused by molecule to molecule of object 

  • Internal vibration causes the vibration in other object  

  • Vibration of molecule -> inc temp of object but actual subject doesn't move 

  • Heat only conduced by vibration of molecules 

• Ex: wavy hand  

  • Hand doesn't change location, just the movement  

  • This is the  molecule  

• Ex: coffee 

  • Coffee is liquid, mug is solid 

  • Liquid heat transferred to solid 

    • Liquid didn't change location -> still feel heat on outside of mug 

      • Only molecule change inside of the solid 

      • Liquid did not move outside mug 

What is convection?

• liquid or gas

• Convection: transport of heat by the vertical movement of a liquid or gas (i.e., warm air rising)

  • Vertical movement of the actual subject 

  • Heating up water on stove -> heat source from bottom and heat moving conduction into pot -> reaches water -> bottom water heats up and is convected up towards the upper parts of water -> circular motion of convection -> boiling where things are rising and falling 

  • Ex: wavy hand 

    • Hand is moving and changing location  

What is advection?

• Advection: transport of heat by the movement of a liquid or gas, dominantly horizontal (i.e., winds moving from sea to land)

  • Horizontal movement of the subject 

  • Winds move energy horiz from one place to another 

What energy heat transfers dominate hydro processes?

• Convention and conduction dominate hydo processes 

How is net radiation expended from a surface?

• Surplus of energy (net gain of energy) some are radiantly put back in atmosphere are LW 

• Energy emitted from Earth (one path way lost or GHG and back down, other pathway used for water) 

• 3 pathways

  • LE (latent heat of evaporation).

    • Latent heat flux

  • H (sensible heat)

    • sensible heat flux

  • Ground energy flux (ground heating or cooling)

What is LE (latent heat of evaporation)?

• This expenditure DOMINATES on earth in general and DEFINITELY when there is water present.

• Latent energy flux 

  • Energy stored in water vapor as it evaporates -> dominates on Earth and over water surface 

  • Latent heat of evap 

    • Lots of energy needed 

    • Doesn't change temp  

      • Only used to change the phase of water 

  • Much more than the others 

  • Most complex concept in hydro 

What is sensible heat flux?

• back and forth transfer between air and surface via convection and conduction within materials.

• Energy we can feel or sense 

• Measure with thermo 

What is Ground energy flux (ground heating or cooling)?

• Energy flowing into and out of ground via conduction

• Energy flowing into or out of the ground via conduction 

• Some energy go deeper into the ground -> some energy go back up to surface 

What pathway is Q* mostly used for?

• Q* is used mostly by latent, sensible -> some will go deeper in the ground (doesn't change water phase, just goes deeper) 

  • Back and forth cycling below the ground 

How do Net Radiation (Q*) and the Expenditure of Net Radiation Relate?

• Q* = how much energy is available for use 

• Energy is going to these three processes -> balance used by hydro processes (mostly LE) 

What happens during the day?

• Incoming solar radiation and outgoing (K) going towards the earth 

  • Albedo -> shorter amounts going out as short wave 

• Long wave coming in and LW going out 

 

• Right 

  • Accumulation of energy 

  • Energy is being pushed into ground and being expended towards sensible and latent heat flux to try to evaporate water 

What happens during the night?

• No incoming SR  

• Dominated by LW roughly equal to each other 

  • Slightly more coming out than in 

• Losing some energy 

  • Energy coming out of ground  

  • Tings are cooler -> sensible going down 

  • No longer breaking bonds, forming bonds (ex: dew and condensation) -> reversal of LE 

What happens when there is water available at the surface?

• If there is water available at surface that can be evaporated -> large amnt of energy available will go towards evaporation -> less energy available for sensible -> not feel as warm 

• In the desert (left) 

  • Almost no energy towards LE -> has to be expended mostly through sensible and some ground 

What happens when there’s little water available on the surface?

• Not lots of water available at surface -> no energy given into breaking hydrogen bonds of water  (LE) ->. Most goes towards sensible heat flux -> feel warmer 

• Right image (more water) 

  • Very high LE -> most is going to LE and little to sensible and some to G 

What is different between the desert and the oasis?

• Both images have the same yellow line -> how energy is used is fundamentally different 

  • Why you feel warmer is desert with same radiation vs oasis with water  

What does sweating do?

• How sweating makes you feel cooler 

  • Water on surface of skin -> energy hitting you from sun goes into latent energy and  less for sensible heat flux 

What is the Bowen ratio?

• Energy partitioning between the dominant heat fluxes may be described by the Bowen Ratio

• Sensible heat flux energy over the latent heat flux 

What happens when B>1?

• B>1 -> more energy is going to making you warm than evaporating water 

  • Sensible > latent -> more energy in air is used to change temp (hotter or colder) 

  • Where less water is available 

What happens when B<1?

• B<1 more energy going to evap water than making you warm 

  • More latent than sensible  

    • More energy to changing water phase than temp 

  • More water