Light surfaces
Reflect sunlight and remain cooler (snow and ice covered surfaces natural reflects - 80-95% reflection of the solar energy received), high albedo
Darker surfaces
Absorb sunlight and heat up (ocean reflects only about 10% of insolation), low albedo
Percentage of reflection
Albedo, the reflective value of a surface
What decreases albedo?
Particulates from the atmosphere (black carbon accumulation)
What accounts for Earth's seasonal rhythms?
Driven by the concentrations of solar energy on Earth's surface, which vary with latitude
What drives ocean currents and heats Earth's surface?
Solar energy
Energy budget
overall balance between shortwave solar radiation to Earth and shortwave and long wave radiation to space (for Earth, income = insolation and expenditure = radiation to space), not the same at every location on Earth's surface because of latitude and seas
Transmission
the uninterrupted passage of shortwave and long wave energy through either atmosphere or water
Shortwave radiation inputs
(UV light, visible light, near-infrared wavelengths)
Longwave radiation outputs
(Thermal infrared wavelengths)
Energy
Capacity to do work, or move matter
Matter
Mass that assumes a physical shape and occupies space
Kinetic energy
Energy of motion produced by the vibrational energy of molecules that we measure as temperature
Potential energy
stored energy (stored either due to composition or position) that has the capacity to do work under the right conditions (ex. petroleum)
Both kinetic and potential energy produce what?
Work, in which matter is moved into a new position or location
Heat
the flow of kinetic energy between molecules and from one body or substance to another resulting from a temperature difference between them, flows from high temp to low temp, stops when the temperatures (amounts of kinetic energy) become equal
Two types of heat energy
Sensible heat - can be "sensed" by humans as temperature, comes from kinetic energy of molecular motion
Latent heat - "hidden heat", energy gained or lost when a substance changes from one state to another (ex. water to ice)
Sensible heat flux
Back and forth transfer between air and surface in turbulent eddies through convection and conduction where T is the land surface temp and Tair is the air temperature
- T > Tair, H increases
- T = Tair, H = 0
- T< Tair, H decreases
Ground heat flux
Energy that flows into or out of the ground surface by conduction where T is the land surface temperature and Td is the deep soil temperature
- T>Td, G decreases
If T = Td, G = 0
If T <Td, G increases
Latent heat flux
Energy that is stored in water vapor as water evaporates
- water absorbs large quantities of this latent heat as it changes state to water vapor, thus removing this heat energy from the surface
Latent heat difference from sensible heat
As long as a physical change in state is taking place, the substance itself does not change temperature
Radiation
Transfer of heat in electromagnetic waves, such as from Sun to Earth (temp of the object determines the wavelength of radiation it emits), waves do not need to travel through a medium in order to transfer heat
Heat and wavelengths
The hotter an object, the shorter the wavelengths that are emitted
Conduction
Molecule-to-molecule transfer of heat energy as it diffuses through a substance (heat flow transfers energy through matter at varying rates, depending on the conductivity of the material- Earth's land surface better conductor than air, moist air better co
Convection
Transfer of heat by mixing or circulation (warmer masses in ocean tend to rise and cooler sink, establishing patterns of convection involving a strong vertical motion)
Advection
Horizontal transfer of heat by mixing or circulation
Radiation and conduction
Pertain to surface energy budgets, temperature differences between land and water and dark and light, and temperature variations in Earth materials
Convection and advection
Atmospheric and oceanic circulation, air mass movements, weather systems, internal motions deep within Earth, movements in Earth's crust; advection: winds from land to sea and sea to land, fog, air mass movements
Insolation
Incoming solar radiation, single energy input driving the Earth-atmosphere system; not equal at all surfaces
- decreases toward the poles
- great insolation occurs in low-latitude deserts because of cloudless skies
Scattering
Accounts for a percentage of insolation that does not reach Earth's surface but is reflected back to space (atmospheric gases and molecules interact with insolation to redirect radiation, changing the direction of the light's movement without altering its
Diffuse radiation
Incoming energy that reaches Earth's surface after scattering; weaker, dispersed radiation composed of waves traveling in different directions, shadowless light on the ground
Direct radiation
Travels in a straight line to Earth's surface without being scattered
Rayleigh scattering
Applies to radiation scattered by small gas molecules and relates amount of scattering in atmosphere to wavelengths of light - shorter wavelengths are scattered more, longer scattered less
- why sunrises are red and sky is blue
- does not apply to atmosph
Altitude of the Sun
determines the thickness of the atmosphere through which its rays must pass to reach an observer
- direct rays pass through less atmosphere and experience less scattering than low oblique-angle rays
Refraction
Traditions that subject insolation to a change of speed, which also shifts its direction
- creates a rainbow
- add approximately 8 minutes of daylight
- change in speed and direction of light as light passes from one medium to another
Mirage
Example of refraction, an image that appears near the horizon when light waves are refracted by layers of air at different temperatures
Reflection
A portion of arriving energy bounces directly back into space without being absorbed or performing any work
Albedo
The reflective quality, or intrinsic brightness, of a surface
- important control over the amount of insolation that reaches Earth
- smooth surfaces increase albedo over rough
- lower angles produce more reflection than higher
-albedo of water surface var
What percentage of albedo do Earth and its atmosphere reflect?
31%
- glow of Earth's albedo is called earthshine
Absorption
the assimilation of radiation by molecules of matter, converting the radiation from one form of energy to another
- raises temperatures of surfaces
- Earth's surface absorbs more radiation than atmosphere
- CO2 and water vapor absorb solar radiation and l
Greenhouse effect
Longwave radiation trapped by an insulating cloud layer creating a warming of Earth's atmosphere
- longwave radiation absorbed by CO2, water vapor, CFCs (greenhouse gases) and emitted back (reradiated toward Earth)
- a real greenhouse traps heat inside
at
Global dimming
Describes the pollution-related decline in insolation to Earth's surface; can be causing warming in Earth's lower atmosphere
Cloud-albedo forcing
Refers to an increase in albedo caused by low-thick stratus clouds (reflect about 90% of insolation)
Cloud-greenhouse forcing
Causes warming of Earth's climate
- caused by cirrus clouds acting as insulation (50% reflection) trapping long wave radiation and raising temperatures
Jet contrails
Condensation trails; produce high cirrus clouds stimulated by aircraft exhaust - false cirrus clouds
- cool and warm the atmosphere
Average annual energy distribution
Positive for Earth's surface and negative for the atmosphere as it radiates energy to space
- atmosphere radiates 58% of the absorbed energy back to space
Energy surplus
Between the tropics, the angle of incoming insolation is high and daylength is consistent, with little seasonal variation, so more energy is gained than lost
Energy deficits
In polar regions, Sun is low in the sky, surfaces are light and reflective, and up to 6 months no insolation is received, so more energy lost than gained
- at around 36 latitude, a balance exists between energy gains and losses for the Earth-atmosphere sy
When do maximum heights for insolation curves occur?
Summer solstice (June 21 in North hemisphere and December 21 in the Southern hemisphere)
- Air temperature generally peaks between 3 and 4 PM ad dips to lowest point at sunrise
- lag between insolation curve and air temperature: warmest time of day occurs
Boundary layer
Where energy and moisture are continually exchanged with the lower atmosphere at Earth's surface
- height not constant over time or space
Microclimatology
science of physical conditions, including radiation, heat, and moisture, in the boundary layer at or near Earth's surface
- microclimates: local climate conditions over a relatively small area (such as park)
How the surface in any given location receives and loses shortwave and long wave energy
+SW (down) - SW (up) + LW (down)- LW (up) = NET R
Net radiation (NET R)
the sum of all radiation gains and losses at any defined location on Earth's surface
- varies with daylight, seasons, cloudiness, latitude
- NET R positive during daylight, peaks after noon, negative at night
- zero value is a perfect balance - rarely occ
Outgoing shortwave
Albedo x insolation
Incoming shortwave
(1-albedo) x insolation
Average annual net radiation
Positive over most of Earth's surface
- negative values occur over ice-covered surfaces at 70 latitude in both hemispheres
- highest net radiation, 185 W/m occurs north of the equator in Arabian Sea
- positive net radiation loses heat for balance from lat
Steady state equilibrium
Input = insolation
Output = reflect shortwave + outgoing longwave
if input = output, then storage change = 0
Earth-Atmosphere energy system
Open system
Energy conservation law: input - output = storage change
Urban Environments
- 6 degrees C hotter than surrounding suburban and rural areas
Urban heat island
both maximum and minimum temperatures higher than nearby rural settings
- planting of vegetation in parks, open space, rooftop gardens, high-albedo roots, and lighter colored pavements can mitigate the effects of UHIs
Dust dome
- airborne pollution trapped by certain characteristics of air circulation in urban heat islands
- collect with a dec. in wind speed in urban centers, then rise as surface heats and remain in air above city