RADIATION BALANCE

ATMOSPHERIC TEMPERATURE

THE SUN AND IT’S ENERGYThe Sun is the star located at the center of our planetary system. It is composed mainly of hydrogen and helium. In the Sun's interior, a thermonuclear fusion reaction converts the hydrogen into helium releasing huge amounts of energy.  The energy created by the fusion reaction is converted into thermal energy (heat) . The solar heat energy travels through space in the form of electromagnetic waves  (As EM waves do not require a medium) enabling the transfer of heat through a process known as radiation.

WHAT IS INSOLATION The amount of solar radiation reaching a given

area.

In simple terms – It is the incoming solar radiation.

Insolation Varies Depending on:

Time of YearSolar DeclinationEarth-Sun DistanceLatitudeTime of day (solar zenith)Atmoshperic Conditions (Clouds, smoke, pollution, diffuse sky light

Energy Basics Energy Pathways and Principles 

Shortwave energy in from the Sun (ultraviolet, visible light, and near-infrared)

Longwave energy out from Earth (thermal infrared)

Transmission The passage of energy through atmosphere or water

Insolation input All radiation received at Earth’s surface – direct and

indirect

ENERGY BALANCE OF THE EARTH

The Earth’s climate is a solar powered system. Globally, over the course of the year, the Earth system—land surfaces, oceans, and atmosphere—absorbs an average of about 240 watts of solar power per square meter.

The absorbed sunlight drives photosynthesis, fuels evaporation, melts snow and ice, and warms the Earth system. The sun provides 99.97% of the energy required for all physical processes that take place on the earth and in the atmosphere

The Sun doesn’t heat the Earth evenly. Because the Earth is a sphere, the Sun heats equatorial regions more than polar regions. The atmosphere and ocean work non-stop to even out solar heating imbalances through evaporation of surface water, convection, rainfall, winds, and ocean circulation. This coupled atmosphere and ocean circulation is known as Earth’s heat engine.

ENERGY BALANCE OF THE EARTH

The climate’s heat engine must not only redistribute solar heat from the equator toward the poles, but also from the Earth’s surface and lower atmosphere back to space. Otherwise, Earth would endlessly heat up. Earth’s temperature doesn’t infinitely rise because the surface and the atmosphere are simultaneously radiating heat to space. This net flow of energy into and out of the Earth system is Earth’s energy budget.

ENERGY BALANCE OF THE EARTH

  The energy that Earth receives from sunlight is balanced by an equal amount of energy radiating into space. The energy escapes in the form of thermal infrared radiation: like the energy you feel radiating from a heat lamp.

ENERGY BALANCE OF THE EARTH

When the flow of incoming solar energy is balanced by an equal flow of heat to space, Earth is in radiative equilibrium, and global temperature is relatively stable. Anything that increases or decreases the amount of incoming or outgoing energy disturbs Earth’s radiative equilibrium; global temperatures rise or fall in response.

Methods of Heat Transfer

Heat always moves from a warmer place to a cooler place.

Hot objects in a cooler room will cool to room temperature.

Cold objects in a warmer room will heat up to room temperature.

Methods of Heat Transfer

Methods of Heat Transfer CONDUCTION When you heat a metal strip at one end, the heat

travels to the other end. As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat.

Methods of Heat Transfer

CONVECTION/ADVECTION

Convection is the transfer of heat by the physical movement of the heated medium itself. Convection occurs in liquids and gases but not in solids.

In convection the physical mixing involves a strong vertical motion.In advection – the horizontal motion dominates.

Methods of Heat Transfer RADIATION Radiation is the transfer of heat in the form of

waves through space (vacuum). Dull black surfaces are better than white shining ones at absorbing the radiated heat.

Radiation transfer from Sun to Earth.Properties of Solar radiation: The Sun is located at the center of our Solar System, at a distance of about 150 x 106 kilometers from Earth. With a surface temperature of 5780 K (degrees Kelvin = degrees C + 273.15), the energy flux at the surface of the Sun is approximately 63 x 106 W/m2 

Solar radiation on Earth: As the Sun's energy spreads through space its spectral characteristics do not change because space contains almost no interfering matter. However the energy flux drops monotonically as the square of the distance from the Sun. Thus, when the radiation reaches the outer limit of the Earth's atmosphere, several hundred kilometers over the Earth's surface, the radiative flux is approximately 1360 W/m2 

The global heat budget is the balance between incoming and outgoing solar radiation. Incoming solar energy varies at different times of year and for different locations across the globe.

Earth's energy budget accounts for how much energy comes into the Earth's climate system from the Sun, how much energy is lost to space, and accounting for the remainder on Earth and its atmosphere. Research to quantify changes in these amounts is required to accurately assess global warming.Received radiation is unevenly distributed over the planet, because the Sun heats equatorial regions more than polar regions. Energy is absorbed by the atmosphere and hydrosphere and, in a process informally described as Earth's heat engine, the solar heating is distributed through evaporation of surface water, convection, rainfall, winds, and ocean circulation. When incoming solar energy is balanced by an equal flow of heat to space, Earth is in radiative equilibrium and global temperatures become relatively stable.

The solar radiation that fills our sky can be direct, diffused or reflected radiation." Direct radiation" is also sometimes called "beam radiation" or "direct beam radiation". It is used to describe solar radiation traveling on a straight line from the sun down to the surface of the earth."Diffuse radiation", on the other hand, describes the sunlight that has been scattered by molecules and particles in the atmosphere but that has still made it down to the surface of the earth.Direct radiation has a definite direction but diffuse radiation is just going any which way.

Because when the radiation is direct, the rays are all travelling in the same direction, an object can block them all at once. This is why shadows are only produced when direct radiation is blocked.

Ratio of direct to diffuse radiationWhen the sky is clear and the sun is very high in thesky, direct radiation is around 85% of the total insolation striking the ground and diffuse radiation is about 15%. As the sun goes lower in the sky, the percent of diffuse radiation keeps going up until it reaches 40% when the sun is 10° above the horizon.Atmospheric conditions like clouds and pollution also increase the percentage of diffuse radiation. On an extremely

overcast day, pretty much 100% of the solar radiation is diffuse radiation. Generally speaking, the larger the percentage of diffuse radiation, the less the total insolation.Direct/diffuse ratio varies with latitude and climateThe percentage of the sky's radiation that is diffuse is much greater in higher latitude, cloudier places than in lower latitude, sunnier places. Also, the percentage of the total radiation that is diffuse radiation tends to be higher in the winter than the summer in these higher latitude, cloudier places. The sunniest places, by contrast, tend to have less seasonal variation in the ratio between diffuse and direct radiation.

Reflected RadiationReflected radiation describes sunlight that has been reflected off of non-atmospheric things such as the ground. Asphalt reflects about 4% of the light that strikes it and a lawn about 25%. However, solar panels tend to be tilted away from where the reflected light is going and reflected radiation rarely accounts for a significant part of the sunlight striking their surface.An exception is in very snowy conditions which can sometimes raise the percentage of reflected radiation quite high. Fresh snow reflects 80 to 90% of the radiation striking it.

Global Insolation

"Global insolation" is the total insolation: direct + diffuse + reflected light.

"Normal radiation" describes the radiation that strikes a surface that is at a 90° angle to the sun's rays. By constantly keeping our solar collectors at a 90° angle with the sun, we maximize the direct radiation received on that day.

Therefore, "normal global radiation" generally tells us what the absolutely most sun we could get is (as discussed earlier in this page, if all the radiation in the sky is diffuse, you do best to just lay your solar collectors down flat - although in that case you aren't going to be gathering much solar radiation anyway).

When you tilt your solar panels so that the sun's rays are hitting them at a 90° angle, you are maximizing the amount of direct radiation that they receive.However, since diffuse radiation is generally pretty equally distributed throughout the sky, the most diffuse radiation is gathered when your solar panels are laying down horizontally.The steeper your solar panels are tilted, the less of the sky they are facing and the more of the sky's diffuse radiation they miss out on. If, for example, your solar collectors are tilted at a 45° angle, they are facing away from about a quarter of the sky and would only collect about three-fourths of the diffuse radiation in the sky.

Still, because direct radiation is much more intense than diffuse radiation, the amount of radiation missed by tilted solar panels is generally more than compensated for by the extra radiation gained by tracking the sun.

The average temperature on the earth is : 15 C

This average temperature is due to the balance between incoming solar radiation and outgoing long wave radiation

70% of the solar radiation reaches the earth’s surface30% is reflected back to space by clouds, particles in the atmosphere or snow or sand or from the surface of the earth – this 30% is not used in the heating of the atmosphere or the surface of the earth.The 70% that stays in our atmosphere can be broken down :

1/3 Powers the hydrologic cycle2/3 Warms to Atmosphere – the oceans & the continents

When UV radiation hits the earth’s surface It is converted to Infrared (Heat)It is this infrared which is heating and keeping the atmosphere warm

EARTH’S ALBEDO = 30%

40

absorbed by clouds and dust, water vapour and other gases in the atmosphere

absorbed by surface

reflected by clouds and dust, water vapour and other gases

in the atmosphere

reflected by surface

100%

19%

26%

55%

4%

51%

SOLAR INSOLATION

absorbed by surface

reflected by atmosphere

reflected by surface

100%

19%

26%

55%

4%

51%

absorbed by atmosphere

solar insolation

reaches surface

TOTAL ALBEDO = 26 + 4

= 30%

TOTAL ABSORPTION = 19 + 51

= 70%

SOLAR INSOLATION

The proportion of radiation reflected or absorbed depends on the object's reflectivity or albedo, respectively.

An ideal white body has an albedo of 100% and an ideal black body, 0%.

TOTAL ALBEDO = 26 + 4= 30%

EARTH’S ENERGY BALANCESENERGY ENTERING TOP OF ATMOSPHERE (342) = ENERGY LEAVING TOP OF ATMOSPHERE(107+235)

TOTAL IN/OUT = 342

ENERGY GAINED BY ATMOSPHERE (67+350+78+24) = ENERGY LOST BY ATMOSPHERE (165+324+30)TOTAL IN/OUT = 519

ENERGY ENTERING EARTHS SURFACE (168+324) = ENERGY LEAVING EARTHS SURFACE (24+78+390)TOTAL IN/OUT = 492

Energy entering at the top of the atmosphere = 342 W/m2

Energy leaving at the top of the atmosphere = 107 (earths albedo)+ 235 (cumulative infra red radiation lost to space by earths atmosphere & surface

Energy gained by the atmosphere = 67 + 350 + 78 + 24 = 519

Energy lost by the atmosphere = 165 + 324 + 30 = 519

Energy entering the earths surface = 168 (Direct Insolation) + 324 (Back Radiation) = 492

Energy leaving earths surface = 24 + 78 + 390 = 492

COMPARISON BETWEEN EARTH & VENUS

The earth has clouds-oceans & landVenus is completely covered with a thick layer of Sulphuric acid clouds

Earths Albedo = 30%Venus Albedo = 70%

Insolation absorbed by earth = 70 unitsInsolation absorbed by Venus = 58 unitsVenus absorbs less solar radiation than earth – so Venus should be cooler!

However!

Earth’s average temperature = 15 CVenus’s average temperature = 480 C

VENUS IS HELL!

THE REASON!

SCATTERINGInsolation encounters an atmosphere of increasing density as it travels toward the surface. Atmospheric gases, dust, cloud droplets, water vapour and pollutants physically interact with the insolation. The gas molecules re-direct the radiation changing the direction of the light’s movement without altering its wave length. Scattering describes this phenomenon and represents 7% ofThe general rule is that – The shorter the wavelength the greater the

scattering – the longer the wave length the lesser the scattering.This is the reason behind the Raleigh Scattering – this is why the skies are blue and why sunsets/sunrises are red.

REFRACTION

When insolation enters the atmosphere – it passes from one medium to another – from a very rare region to a very dense region. This occurs when insolation passes from air into water. This causes the insolation to change speed which also causes its direction to shift – this is refraction. In the same way the prism refracts the incoming light waves.

VARIOUS ALBEDO VALUES

ALBEDO & REFLECTIONThe portion of arriving energy that bounces back into space without being absorbed or performing any work is called the Reflection process. Albedo is the reflective quality.0% is total absorption – 100% is total reflection.In the visible wave lengths – darker colors have lower albedos and lighter color have higher albedos. The angle of the solar rays also effect albedos – lower angles produce greater reflection

than do higher angles. Smooth surfaces increase albedo where as rough surfaces reduce it.

CLOUDS-AEROSOLS & ATMOSPHERES ALBEDO

CHANGES IN ALBEDO

Clouds reflect and cool the earth and at the same time they act as insulators – trapping long wave radiation from the earth and raising the minimum temperatures. Cloud greenhouse forcing is an increase in greenhouse warming caused by clouds.Industrialization is producing a haze of pollution including sulfate aerosols, soot & fly ash and black carbon. These suspended aerosols in the atmosphere act as an insolation-reflecting haze in clear sky conditions

Pollution causes both an atmospheric warming through absorption by the pollutants and a surface cooling through reduction in insolation reaching the surface. Clouds effect the heating of the lower atmosphere in several ways – depending on cloud type. The cloud cover is important as well as the cloud type, height and thickness of the cloud. High ice crystal clouds have an albedo value of about 50% whilst thick lower clouds have a 90% albedo value.

ABSORPTIONThe assimilation of radiation by molecules of matter and its conversion from one form of energy to another are absorption.The temperature of the absorbing surface is raised in the process and warmer surfaces radiate more total energy at shorter wavelengths – thus the hotter the surface – the shorter the wave lengths emitted.

ENERGY BALANCE IN THE TROPOSPHEREThe earth-atmosphere energy system naturally balances itself in a steady state equilibrium.

Several patterns are notable on the map. Insolation decreases pole ward from about 25 N/S. Consistent day lengths and a high sun altitude produce average annual values of 180-220 Watts/m2 throughout the equatorial and tropical latitudes. In general greater insolation of 240-280 W/m2 occurs in low latitude deserts worldwide because of frequently cloudless skies. Note this energy pattern in the cloudless subtropical deserts in both hemispheres e.g Sahara-Gobi-Kalahari & Australian deserts.

The net heating imbalance between the equator and poles drives an atmospheric and oceanic circulation that climate scientists describe as a “heat engine.” (In our everyday experience, we associate the word engine with automobiles, but to a scientist, an engine is any device or system that converts energy into motion.) The climate is an engine that uses heat energy to keep the atmosphere and ocean moving. Evaporation, convection, rainfall, winds, and ocean currents are all part of the Earth’s heat engine.

Earth’s heat engine does more than simply move heat from one part of the surface to another; it also moves heat from the Earth’s surface and lower atmosphere back to space. This flow of incoming and outgoing energy is Earth’s energy budget. For Earth’s temperature to be stable over long periods of time, incoming energy and outgoing energy have to be equal. In other words, the energy budget at the top of the atmosphere must balance. This state of balance is called radiative equilibrium.

Regionally and seasonally the earth absorbs more energy in the tropics and less in the polar regions – establishing the imbalance which drives the Global circulation patterns. 1. Between the tropics – the angle of

incoming insolation is high and daylight consistent – more energy is gained than lost – Energy surpluses dominate.

2. In the polar regions – the sun is low in the sky, surfaces are light (ice & snow) and reflective and up to 6 months a year no insolation is

received – so more energy is lost than gained – energy deficit prevails3. At around 36N/S a balance exists between energy gains and losses for the earth-atmosphere system. The imbalance of net radiation between the tropical surpluses and the polar deficits drives a vast global circulation of both energy and mass.

WHAT IS THE GREEN HOUSE EFFECT?The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases.

WHAT ARE GREEN HOUSE GASES?A gas that contributes to the greenhouse effect by absorbing infrared radiation. 

When greenhouse gas molecules absorb thermal infrared energy, their temperature rises. Like coals from a fire that are warm but not glowing, greenhouse gases then radiate an increased amount of thermal infrared energy in all directions. Heat radiated upward continues to encounter greenhouse gas molecules; those molecules absorb the heat, their temperature rises, and the amount of heat they radiate increases. At an altitude of roughly 5-6 kilometers, the concentration of greenhouse gases in the overlying atmosphere is so small that heat can radiate freely to space.

Because greenhouse gas molecules radiate heat in all directions, some of it spreads downward and ultimately comes back into contact with the Earth’s surface, where it is absorbed. The temperature of the surface becomes warmer than it would be if it were heated only by direct solar heating. This supplemental heating of the Earth’s surface by the atmosphere is the natural greenhouse effect.

Why doesn’t the natural greenhouse effect cause a runaway increase in surface temperature? Remember that the amount of energy a surface radiates always increases faster than its temperature rises—outgoing energy increases with the fourth power of temperature. As solar heating and “back radiation” from the atmosphere raise the surface temperature, the surface simultaneously releases an increasing amount of heat—equivalent to about 117 percent of incoming solar energy. The net upward heat flow, then, is equivalent to 17 percent of incoming sunlight (117 percent up minus 100 percent down).

The Energy Balance at The Earths surface

What happens if all greenhouse gases are removed Incoming energy would decrease

Earths surface would cool and Would emit less infrared radiationUntil the balance is restoredThe cooling would stop at (0 F)

If all the greenhouse gases were removed from the atmosphere – the atmosphere would not be able to absorb radiation emitted by the earth so energy emitted by greenhouse molecules would go to zero – this in turn would drastically reduce the incoming energy absorbed by the earths surface.

The Earths surface temperature = 15C - With greenhouse gases

Concentration of CO2 gasesIncreased by 50%

Earth’s surface would heatAnd emit more infrared radiationUntil balance is restored

The Greenhouse effect keeps the earth warm – without it the average temperature of the earth would be -18C.This would mean no life on earth because there would be no liquid water.The Greenhouse effect is truly important for our existence and the existence of all living things on the earth.The Greenhouse effect becomes a problem when we humans mess with it.

CO2 is the biggest gas influencing the greenhouse effect.

What will happen if we increase the amount of CO2 in our atmosphere?

MORE CO2

MORE HEAT BEING TRAPPED

HIGHER TEMPERATURES ON EARTH

What will happen if the level of CO2 gases increase in the atmosphere?

1. Global warming2. Glaciers & Icebergs will melt3. Sea levels will rise4. It will cause droughts

(Desertification) in one region and extra rains in other

5. Stronger storms & extreme events6. Increase in ocean acidification

ENERGY BALANCE AT THE EARTH’S SURFACE

This shows the daily pattern of incoming short wave energy absorbed and resulting air temperature. This is an ideal condition for bare soil on cloudless day in middle latitudes. Incoming energy arrives during day light – beginning at sunrise – peaking at noon & ending at sunset. The shape & height of the graph varies season & latitude.Within 24 hours – air temperature generally peaks between 1500 and 1600 hours and the minimum temperature is slightly after sunrise.

The interesting fact is that the insolation curve and the temperature curve do not align – there is a lag – The maximum temperature does not occur at the time of maximum insolation but at the time when a maximum of insolation is absorbed and emitted to the atmosphere from the ground. The maximum occurs when the incoming energy begins to diminish.The same is true for the annual patterns of insolation & temperature – January being colder than December & warmest month of July after June.

SIMPLIFIED SURFACE ENERGY BALANCE

Energy and moisture are continually exchanged at the surface – creating a variety of boundary layer climates. Sensible heat transfer in the soil is through conduction. – predominantly downward during the day and towards the surface at night. Energy from the atmosphere that is moving towards the surface is a positive (a gain) and energy that is moving away from the surface through sensible & latent heat is a negative (a loss).

The components of the equation vary with day length – seasons – cloudiness – latitude so does the net radiation received vary.

Latent and Sensible Heat

Latent and sensible heat are types of energy released or absorbed in the atmosphere.  Latent heat is related to changes in phase between liquids, gases, and solids.  Sensible heat is related to changes in temperature of a gas or object with no change in phase.

Latent heat is the energy absorbed by or released from a substance during a phase change from a gas to a liquid or a solid or vice versa.  If a substance is changing from a solid to a liquid, for example, the substance needs to absorb energy from the surrounding environment in order to spread out the molecules into a larger, more fluid volume.  If the substance is changing from something with lower density, like a gas, to a phase with higher density like a liquid, the substance gives off energy as the molecules come closer together and lose energy from motion and vibration.

On land the higher annual values of latent heat of evaporation (LE) occur in the tropics and decrease towards the pole . Over the oceans the highest LE values are over the sub-tropical latitudes where hot – dry air comes in contact with the warm ocean water.

GLOBAL LATENT HEAT OF EVAPORATION

Sensible HeatSensible heat is the energy required to change the temperature of a substance with no phase change. The temperature change can come from the absorption of sunlight by the soil or the air itself.  Or it can come from contact with the warmer air caused by release of latent heat.  Energy moves through the atmosphere using both latent and sensible heat acting on the atmosphere to drive the movement of air molecules which create wind and vertical motions.

The values for sensible heat (H) are highest in the sub-tropics – due to vast regions of sub-tropical deserts feature nearly waterless surfaces – cloudless skies and almost vegetation free landscapes. The bulk of NET R is expended as sensible heat in these dry regions. Moist & vegetated surfaces expend less in “H” and more in “LE”

GLOBAL SENSIBLE HEAT

NET RADIATION

Earth's net radiation, sometimes called net flux, is the balance between incoming and outgoing energy at the top of the atmosphere. It is the total energy that is available to influence the climate.

Net RadiationThe net radiation determines whether the surface temperature rises, falls, or remains the same:NET(R)= incoming solar - outgoing IR

If the net radiation > 0, surface warms ( 0600 to 1600 Hrs)if the net radiation < 0, surface cools (1600 – 0600 Hrs)

This also explains why the warmest part of the year is in July/August, not on 21 June during the summer solstice.

Effect of orbit's shape: The radiation at the top of the atmosphere varies by about 3.5% over the year, as the Earth spins around the Sun. This is because the Earth's orbit is not circular but elliptical, with the Sun located in one of the foci of the ellipse. The Earth is closer to the sun at one time of year (a point referred to as perihelion) than at the "opposite" time (a point referred to as aphelion). The time-of-year when the Earth is at perihelion moves continuously around the calendar year with a period of 21,000-years. At present perihelion occurs in the middle of the Northern Hemisphere winter. The annual average radiative solar flux at the top of the Earth's atmosphere (=1360 W/m2) is sometimes referred to as the Solar Constant because it has changed by no more than a few percent over the recent history of the Earth (last few hundred years). There are however important variations in this flux over longer, so-called "geological", time scales, to which the Earth glaciation cycles are attributed.

The tilt of the Earth's axis and the seasons: If the axis of Earth was perpendicular to the plane of its orbit (and the direction of incoming rays of sunlight), then the radiative energy flux would drop as the cosine of latitude as we move from equator to pole. However, as seen in Figure 6, the Earth axis tilts at an angle of 23.5° with respect to its plane of orbit, pointing towards a fix point in space as it travels around the sun. Once a year, on the Summer Solstice (on or about the 21st of June), the North Pole points directly towards the Sun and the South Pole is entirely hidden from the incoming radiation. Half a year from that day, on the Winter

Solstice (on or about the 21st of December) the North Pole points away from the Sun and does not receive any sunlight while the South Pole receives 24 hours of continued sunlight. During Solstices, incoming radiation is perpendicular to the Earth surface on either the latitude of Cancer or the latitude of Capricorn, 23.5° north or south of the equator, depending on whether it is summer or winter in the Northern Hemisphere, respectively. During the spring and fall (on the Equinox days, the 21st of March and 23rd of September) the Earth's axis tilts in parallel to the Sun and both Polar Regions get the same amount of light. At that time the radiation is largest at the true equator. Averaged over a full 24-hour period, the amount of incoming radiation varies with latitude and season as shown in Figure 7. Note that the figure combines the effect of the change in incidence angle with latitude and time of year and the number of hours of sunlight during the day. At the poles, during solstice, the earth is either exposed to sunlight over the entire (24-hours) day or is completely hidden from the Sun throughout the entire day. This is why the poles get no incoming radiation during their respective winter or more than the maximum radiation at the equator during their respective summer.

LithosphereThe lithosphere is the solid, rocky crust covering entire planet. This crust is inorganic and is composed of minerals. It covers the entire surface of the earth from the top of Mount Everest to the bottom of the Mariana Trench.HydrosphereThe hydrosphere is composed of all of the water on or near the earth. This includes the oceans, rivers, lakes, and even the moisture in the air. Ninety-seven percent of the earth's water is in the oceans. The remaining three percent is fresh water; three-quarters of the fresh water is solid and exists in ice sheets

BiosphereThe biosphere is composed of all living organisms. Plants, animals, and one-celled organisms are all part of the biosphere. Most of the planet's life is found from three meters below the ground to thirty meters above it and in the top 200 meters of the oceans and seas.

AtmosphereThe atmosphere is the body of air which surrounds our planet. Most of our atmosphere is located close to the earth's surface where it is most dense. The air of our planet is 79% nitrogen and just under 21% oxygen; the small amount remaining is composed of carbon dioxide and other gases. All four spheres can be and often are present in a single location.For example, a piece of soil will of course have mineral material from the lithosphere. Additionally, there will be elements of the hydrosphere present as moisture within the soil, the biosphere as insects and plants, and even the atmosphere as pockets of air between soil pieces.

Disturbances of Earth's radiative equilibrium, such as an increase of greenhouse gases, change global temperatures in response. However, Earth's energy balance and heat fluxes depend on many factors, such as the atmospheric chemistry composition (mainly aerosols, and greenhouse gases), the albedo (reflectivity) of surface properties, cloud cover, and vegetation and land use patterns. Changes in surface temperature due to Earth's energy budget do not occur instantaneously, due to the inertia (slow response) of the oceans and the cryosphere to react to the new energy budget. The net heat flux is buffered primarily in the ocean‘s heat content, until a new equilibrium state is established between incoming and outgoing radiative forcing and climate response.

The cryosphere is the frozen water part of the Earth system. Beaufort Sea, north of Alaska. One part of the cryosphere is ice that is found in water. This includes frozen parts of the ocean, such as waters surrounding Antarctica and the Arctic. There are places on Earth that are so cold that water is frozen solid.

Solar constant

Solar constant, the total radiation energy received from the Sun per unit of time per unit of area on a theoretical surface perpendicular to the Sun’s rays and at Earth’s mean distance from the Sun.

SOLAR DECLINATION

SOLAR DECLINATION Solar Declination (δ)

Earth's axial tilt is: 23.45º

Solar Declination = Latitude of the sub-solar point (where the sun is directly overhead at solar noon)

Solar Declination (δ) changes seasonally, and is calculated by the day of year using the following equation:

δ =23.45*cos(2*π*(JD-172)/365)Where: JD = Julian Day (count the days from Jan.1st)

SEASONS

Earth-Sun Distance

Earth-Sun Distance The sun and earth are closest during perihelion and

farthest away during aphelion. The Solar constant is the incoming solar radiation measured at the top of the Earth's atmosphere on a surface that is perpendicular to the incident rays. While the average is 1367 W/m2, it varies due to the earth-sun distance, since radiation intensity is proportional to the square inverse of the sun-earth distance. This is because the surface area (4*pi*r^2) over which the sun's energy is distributed will increase with r, the earth-sun distance, and therefore since the total energy is constant, the intensity (W/m2) must decrease.

LATITUDE

Insolation decreases with increased latitude