Geo 4

Cloud and Absorption

Clouds are made of water droplets or ice crystals, but they are suspended in the atmosphere and interact with incoming and outgoing radiation Clouds absorb a little shortwave radiation Clouds absorb almost all long

Balancing the Energy Budget means

Energy is being redistribute

Continentaility

Land cools and heats rapidly

Mode of Energy Transfer; Convection

Occurs in fluids, molecules are displaced Liquids & gases Heating water: water on bottom warms and expands, after expansion it is less dense, and rises, hot molecules run into cooler molecules as they move

Ocean currents

Ocean currents are a part of the global redistribution of energy

The Sun as a Star; Distance

The Sun is about 150 million km (93 million miles) away from Earth. The situation is similar to the honey bee hovering about two football fields away from the line- backer. The mass of the Sun is 1.99x1030 kg, or about 333,000 times Earth's mass. This is the same ratio as between the linebacker (100 kg) and three honey bees (0.1 g each).

Electromagnetic Radiation & Behavior of Magnetic Objects

The energy emitted by the Sun is mostly in the form of electromagnetic radiation. To understand this kind of radiation better, we can think of a familiar situation of weather maps. The Universe can also be thought of as being permeated by an electric field. All electrically charged particles (such as electrons) have a region of space around them where they influence the behavior of other charged particles wandering there. This region can be described as an electric field around the particle. Just as temperatures in different parts of the country create the temperature field of the United States, the electric charges in the Universe can be thought of as creating an electric field permeating the whole Universe. Magnetic objects behave in a similar fashion: every magnetic object creates a magnetic field around it, and their collective magnetic field permeates the Universe.

The troposphere (is / is not) heated by the sun directly

The troposphere is NOT heated by the sun directly!

On Earth, there are fundamentally only three ways in which energy can be transferred from one place to another:

conduction, convection, and radiation

Sensible Heat

heat that we can sense. A thermometer can be used to measure this form of heat. Several different scales of measurement exist for measuring sensible heat. The most common are: Celsius scale, Fahrenheit scale, and the Kelvin scale.

Conduction

involves the adjacent transfer of heat energy from one atom to another through the mass of a gas, liquid, or solid. Condution results in the continuous flow of heat energy along a temperature gradient from areas of higher to lower temperature

Atomic Energy

is the energy released from an atomic nucleus because of a change in its subatomic mass.

Sunlight

is the source of life-sustaining energy on Earth. Its effects range from allowing temperatures on our planet to remain hospitable for life to providing energy for photosynthesis.

Earth's Average Albedo

reflectance from both the atmosphere and the surface, is about 30%.

Heat Capacity

the amount of heat energy absorbed by a substance associated to its corresponding temperature increase.

Radiatiom

the emission of energy from a material object in the form of electromagnetic waves and photons.

Energy comes in a variety of forms

Kinetic & Potential Heat, electricity, sound, energy of chemical reactions, magnetic attraction, energy of atomic reactions, and light.

Kinetic Energy; Temperature

Kinetic energy is also related to the concept of temperature. Temperature is defined as the measure of the average speed of atoms and molecules. The higher the temperature, the faster these particles of matter move. At a temperature of -273.15° Celsius (absolute zero) all atomic motion stops. Heat is often defined as energy in the process of being transferred from one object to another because of difference in temperature between them.

Latent Heat

Latent Heat Transfer: energy absorbed which changes the phase (and NOT the temperature) of a substance Elements can exist in 3 phases Solid Liquid Gas It takes extra energy to change the phase of a substance

Shortwave Radiation is

Absorbed by the Earth and clouds Scattered by gases and clouds Reflected by the Earth's surface and clouds Transmitted to the Earth's surface

Absorption

Absorption means energy increases in the absorber Energy changes forms Sensible heat: increases temperature/kinetic energy Latent heat: changes phase of water/breaks bonds

Atmospheric Interaction with Radiation

4 possibilities: Reflection Scattering Transmission Absorption

Transmission

Radiation passing through the atmosphere without attenuation (loss).

Radiation emitted by Sun

consists of all types of electromagnetic radiation. At the speed of light, it takes about eight minutes for the radiation emitted from the surface of the Sun to reach Earth.

Three atmospheric processes

modify the solar radiation passing through our atmosphere destined to the Earth's surface. These processes act on the radiation when it interacts with gases and suspended particles found in the atmosphere.

Scattering occurs when

"The process of atmospheric scattering causes rays of sunlight to be redirected to a new direction after hitting a particle in the atmosphere." Small particles and gas molecules diffuse part of the incoming solar radiation in random directions without any alteration to the wavelength of the electromagnetic energy. Scattering does, however, reduce the amount of incoming radiation reaching the Earth's surface. A significant proportion of scattered shortwave solar radiation is redirected back to space. The amount of scattering that takes place is dependent on two factors: wavelength of the incoming radiation and the size of the scattering particle or gas molecule. In the Earth's atmosphere, the presence of a large number of particles with a size of about 0.5 microns results in shorter wavelengths being preferentially scattered. This factor also causes our sky to look blue because this color corresponds to those wavelengths that are best diffused. If scattering did not occur in our atmosphere the daylight sky would be black.

Visible Light

A familiar example of this kind of wave is visible light. Different colors of visible light have slightly different wavelengths, and there are waves which have much higher and shorter wavelengths than the light that humans can see. Together, the waves of all different wavelengths are called electromagnetic radiation, and the whole array of different kinds of light, arranged according to their wavelength, is called the electromagnetic spectrum. We can see part of the Sun's spectrum in a rainbow, when the visible light is spread out by raindrops in the Earth's atmosphere. We cannot see the other parts of the spectrum beyond visible light (longer wave- length than red or shorter wavelength than blue light), but they can be detected with instruments. Visible light has a spectrum that ranges from 0.40 to 0.71 micrometers (µm)

Greenhouse Gasses

A number of gases are involved in the human caused enhancement of the greenhouse effect (see Table 7h-1 below). These gases include: carbon dioxide (CO2); methane (CH4); nitrous oxide (N2O); chlorofluorocarbons (CFxClx); and tropospheric ozone (O3). Of these gases, the single most important gas is carbon dioxide which accounts for about 55% of the change in the intensity of the Earth's greenhouse effect. The contributions of the other gases are 25% for chlorofluorocarbons, 15% for methane, and 5% for nitrous oxide. Ozone's contribution to the enhancement of greenhouse effect is still yet to be quantified.

Absorption; Longwave

ABSORPTION -- LONGWAVE The earth emits longwave radiation and Greenhouse gases (GHGs) Water vapor, CO2, and methane absorb some of this longwave energy. Some longwave energy is transmitted by (passes through) the atmosphere and escapes to space. If it didn't escape, our global temperature would keep rising.

Greenhouse Effect Warming Cycle

Absorption of longwave radiation by the atmosphere causes additional heat energy to be added to the Earth's atmospheric system. The now warmer atmospheric greenhouse gas molecules begin radiating longwave energy in all directions. Over 90% of this emission of longwave energy is directed back to the Earth's surface where it once again is absorbed by the surface. The heating of the ground by the longwave radiation causes the ground surface to once again radiate, repeating the cycle described above, again and again, until no more longwave is available for absorption.

Radiation; Objects above absolute zero

All objects above the temperature of absolute zero (-273.15° Celsius) radiate energy to their surrounding environment. This energy, or radiation, is emitted as electromagnetic waves that travel at the speed of light. Many different types of radiation have been identified. Each of these types is defined by its wavelength. The wavelength of electromagnetic radiation can vary from being infinitely short to infinitely long (Figure 6f-1).

Temperature

An object's temperature describes the level of motion and vibration in the atoms and molecules of which it is composed. The higher the temperature of the object, the more its atoms and molecules move around, and the more disorderly is their motion. This means that heat flowing into an object increases the internal energy and disorder in that object, while heat flowing out of it decreases the internal energy and disorder in that object. For example, the water molecules in a snowflake are arranged in an orderly pat- tern. If you hold a snowflake in your hand, it will melt and become a drop of water. In this case, the orderly pattern of the snowflake changes into the more disorderly form of liquid water.

Solar Thermal Conversion System

Another way to take advantage of the power of sun- light is a solar thermal conversion system, which uses reflectors to concentrate solar energy to very high levels. The heat generated in this manner can be used to heat water or to drive a steam turbine to produce electricity. A device called a solar furnace can be used to collect solar radiation to produce temperatures high enough for use in industrial processes, such as processing steel, while smaller-scale versions can be used to cook food. Different variations of this theme are used in different parts of the world to produce power in a manner that is best suited for the region and the application.

Percentage of Energy

As energy from the Sun passes through the atmosphere a number of things take place. A portion of the energy (26% globally) is reflected or scattered back to space by clouds and other atmospheric particles. About 19% of the energy available is absorbed by clouds, gases (like ozone), and particles in the atmosphere. Of the remaining 55% of the solar energy passing through the Earth's atmosphere, 4% is reflected from the surface back to space. On average, about 51% of the Sun's radiation reaches the surface. This energy is then used in a number of processes, including the heating of the ground surface; the melting of ice and snow and the evaporation of water; and plant photosynthesis.

Energy and Weather

Earth's surface is heated by the sun: shortwave radiation, Atmosphere is heated by the surface: conduction and infrared radiation Energy moves through the air: convection and infrared radiation

Longwave Radiation is

Emitted by the Earth, clouds, atmosphere Absorbed by the atmosphere, clouds and Earth Transmitted to outer space

Latent heat exchanges of energy involved with the phase changes of water.

Figures 6c-2 and 6c-3 show the net absorption and release of latent heat energy for the Earth's surface for January and July, respectively. The highest values of flux or flow occur near the subtropical oceans where high temperatures and a plentiful supply of water encourage the evaporation of water. Negative values of latent heat flux indicate a net release of latent energy back into the environment because of the condensation or freezing of water. Values of latent heat flux are generally low over landmasses because of a limited supply of water at the ground surface.

Gas Molecules

Gas molecules are 100x smaller than visible light wavelengths

The atmosphere redistributes energy

Heat flows from hot areas to cold areas: gradient

Kinetic Energy; Heat

Heat is often defined as energy in the process of being transferred from one object to another because of difference in temperature between them.

Heat

Heat passes from one substance or object to another by three methods—conduction, convection, and radiation. Although conduction (heat moving through material) and convection (heat transferred by moving material) need media through which to transfer energy, heat can be transmitted via radiation through infrared or other rays, without need for material. The Sun can therefore send its energy through the vacuum of space via radiation. Note that radiation may also work when material is present. For example, after traveling through space, sunlight passes through the Earth's atmosphere to reach the surface. As discussed earlier, both radiation and convection play a role in transferring the energy generated inside the Sun to its surface.

Absorption

If intercepted, some gases and particles in the atmosphere have the ability to absorb incoming insolation. Absorption is defined as a process in which solar radiation is retained by a substance and converted into heat energy. The creation of heat energy also causes the substance to emit its own radiation. In general, the absorption of solar radiation by substances in the Earth's atmosphere results in temperatures that get no higher than 1800° Celsius. According to Wien's Law, bodies with temperatures at this level or lower would emit their radiation in the longwave band. Further, this emission of radiation is in all directions so a sizable proportion of this energy is lost to space. In this process, sunlight is absorbed by an atmospheric particle, transferred into heat energy, and then converted into longwave radiation emissions that come from the particle.

The MESSENGER - Long Term Sun Study

In addition to investigating radiation reflected or re- radiated by Mercury's surface, MESSENGER will also study radiation coming directly from the Sun. Orbiting Mercury for the duration of one Earth year will offer an excellent opportunity to make long-term observations of the space environment near the Sun, and to investigate the effect of the Sun's activity on the environment. In this manner, the spacecraft will not only help us understand the planet Mercury better, but will also provide invaluable information about the Sun.

Fusion vs Fission

In fusion, nuclear matter is converted to energy by joining hydrogen atoms into helium, with accompanying release of energy. Fusion is a very efficient way to make energy, as compared with fission, in which a nucleus of a heavy atom is split to release energy. Fission is the way nuclear energy is produced in nuclear power plants here on Earth. The possibility of being able to pro- duce energy on Earth via fusion is very tantalizing, especially since the by-products of fission can be quite harmful for life, while fusion products are harmless. Unfortunately, we do not yet have the technology to efficiently produce energy via fusion on Earth.

Kirchhoff's Law

In general, good emitters of radiation are also good absorbers of radiation at specific wavelength bands. This is especially true of gases and is responsible for the Earth's greenhouse effect. Likewise, weak emitters of radiation are also weak absorbers of radiation at specific wavelength bands. This fact is referred to as Kirchhoff's Law.

All affect temperature

Latitude, Altitude, Time of day, time of year, & continentality

Influences on Temperature

Latitude: determines how much solar energy is received Altitude: less atmosphere to interfere with outgoing Contrasts between land and water Ocean currents Diurnal cycle

Sunsets

Longer atmospheric path length affects sunset colors

energy transfer by way of conduction and convection depends on the presence of ______.

Matter. (These forms of energy transfer do not operate in the vacuum of space.)

Latent Heat Example; Ice

Melting Ice Suppose you have a kg of ice with a temperature of -1oC Sensible heat: 1 kg ice at -1oC + 4190 J 1 kg ice at 0oC Latent heat (of fusion) - melting ice; solid ---> liquid To get water, you must add extra 335,000 Joules of energy!! 1 kg ice at 0oC + 335,000 J ---> 1 kg water at 0oC NO temperature change! Boiling Water NOW THAT WE HAVE MELTED THE ICE To warm our 1 kg of water up to the boiling point It takes 4190J/degree C x 100 degrees C = 419,000 J What about getting that water to evaporate? LATENT HEAT (of vaporization): evaporation (liquid ---> gas) The most important energy transfer mechanism in the atmosphere 1 kg H2O (l) at 100oC + ? J ---> 1 kg H2O (g) at 100oC Answer: 2,500,000 Joules!

Absorption; Shortwave

Most shortwave radiation is not absorbed by the atmospheric gases How do we know? Ozone is the exception: It absorbs UV in the stratosphere 51% of incoming shortwave radiation (mostly light) is absorbed at the surface of the Earth

Changes in Velocity of an Electric Charge

Most things in the Universe tend to move around, and electric charges are rarely an exception. If the velocity of an electric charge changes (that is, it accelerates or decelerates), it creates a disturbance in the electric and magnetic fields permeating the Universe. These disturbances move across the Universe as waves in the "fabric" of the electric and magnetic fields. The waves also carry energy from the disturbance with them, in a similar way that the energy of the wind striking a flag is carried across the fabric by the waving of the flag. The waves carrying the energy of the disturbance across the Universe are characterized by their wavelength, which measures the distance between two consecutive wave crests.

Non-Selective Scattering

Non-Selective Scattering Scattering agent: H2O droplets White or grey in color: Clouds, haze

Surface Reflectivity / "Albedo"

Not all of the direct and diffused radiation available at the Earth's surface is used to do work(photosynthesis, creation of sensible heat, evaporation, etc.). As in the atmosphere, some of the radiation received at the Earth's surface is redirected back to space by reflection known as surface reflectivity.

On a local scale, the incoming energy (does / does not) equal the outgoing energy

On a local scale, the incoming energy does not equal the outgoing energy

Kinetic Energy; Heat Energy

One important form of energy, relative to life on Earth, is kinetic energy. Simply defined, kinetic energy is the energy of motion. The amount of kinetic energy that a body possesses is dependent on the speed of its motion and its mass. At the atomic scale, the kinetic energy of atoms and molecules is sometimes referred to as heat energy.

Greenhouse

One of the most familiar human uses of solar energy is a greenhouse. Windows let the sunlight through, but the heat generated by the sunlight in the green- house is trapped in, and it can escape only slowly. This creates a warm environment for plants to grow, making production of fresh vegetables and flowers possible during winter in cold climates.

Radiative Zone

Outside the Sun's core is the radiative zone, which is named for the way that energy produced in the core travels through the zone—mainly via radiation. The radiative zone extends from the outer edge of the core (at 25% of the solar radius) to about 70% of the solar radius.

Reflection; Shortwave

REFLECTION - SHORTWAVE Change in direction of energy, without absorption Energy is not increased in the reflector Albedo = the percentage of light reflected by a surface The planetary albedo is about 30%

Radio Waves

Radio waves are in the long-wavelength (low-frequency) and the gamma rays in the short-wavelength (high- frequency) end of the spectrum, with visible light located between infrared and ultraviolet. Electromagnetic radiation travels at the speed of light (300,000 km/s or 186,000 miles/s in a vacuum such as space).

Mode of Energy Transfer; Radiation

Requires no physical medium Moves energy through the vacuum of space Radiation emitted by all substances Amount and type of radiation depends on the object's temperature (radiation laws).

Scattering; Shortwave

SCATTERING -- SHORTWAVE A SPECIAL KIND OF REFLECTION Light is broken up into rays which are reflected in different directions Scattering produces diffuse radiation (light under trees, in the shade, on a cloudy day) Some wavelengths of light are scattered by the atmospheric gasses All wavelengths of light are scattered by cloud droplet

Sensible Heat

SENSIBLE HEAT - HEAT YOU CAN FEEL Sensible Heat: Energy absorbed which results in raising the temperature of something You can measure, or "sense," this change How much the temperature changes depends on substance

Rayleigh Scattering

Scattering agent: gas molecules Blue light is more likely to be scattered Gives the atmosphere it's blue color

Earth's Energy Budget

Shortwave energy from the sun enters Longwave energy from the earth leaves This energy must move through the atmosphere. The Earth's "energy budget" is the balance between incoming radiation from the sun (mostly visible light) and the outgoing thermal (infrared) energy from Earth.

Energy Balance

Shortwave energy radiated to planet Longwave energy radiated away from planet The Balance is the Earth's average temperature

Solar Cells & Power Production

Solar energy can be converted into electric power in solar cells. They employ the photovoltaic effect, in which energy in the sunlight creates an electric current in a conductive material. For most uses, cells are grouped into modules, and multiple modules may be arranged into arrays to provide sufficient current for the application. Examples of power production by solar cells include spacecraft, satellites, handheld calculators, and wristwatches. Solar cells can also be used for everyday electricity production in areas where there is plenty of sunlight available most of the year.

Black Bodies

Some objects in nature have almost completely perfect abilities to absorb and emit radiation. We call these objects black bodies. The radiation characteristics of the Sun and the Earth are very close to being black bodies.

Direct vs Diffused Solar Radiation

Sunlight reaching the Earth's surface unmodified by any of the above atmospheric processes is termed direct solar radiation. Solar radiation that reaches the Earth's surface after it was altered by the process of scattering is called diffussed solar radiation.

Waves passing through to Earth

The Earth's atmosphere reflects away or absorbs much of the electromagnetic spectrum, so that only part of the radiation reaches the surface. Most of the radio waves come through the atmosphere unimpeded, visible light passes through without much difficulty, while only some infrared radiation, very little of the ultraviolet rays, and none of the X-rays and gamma rays reach the surface. This is actually very fortunate for life on Earth, especially with regards to harmful, high-energy radiation (ultraviolet, X-rays and gamma rays).

Solar Radiation Spectrum; Wavelength Band

The Sun emits only a portion (44 %) of its radiation in zone. Solar radiation spans a spectrum from approximately 0.1 to 4.0 micrometers. The band from 0.1 to 0.4 micrometers is called ultraviolet radiation. About 7% of the Sun's emission is in this wavelength band. About 48% of the Sun's radiation falls in the region between 0.71 to 4.0 micrometers. This band is called the near (0.71 to 1.5 micrometers) and far infrared (1.5 to 4.0 micrometers).

Particle Radiation & Solar Wind

The Sun emits particle radiation from the corona, made up mostly of protons and electrons, but also of some heavier ions. These spread out to the Solar System as the solar wind. Solar particle radiation can be quite damaging to life, but fortunately Earth's magnetic field prevents the solar wind particles from reaching the surface. Because this protection is less or completely absent in space, the amount of particle radiation to which the astronauts are exposed is carefully monitored to prevent serious health effects. The amount of solar particle radiation arriving at Earth depends on the level of the Sun's activity. When there is an explosion on the Sun (a solar flare), especially large concentrations of particles can arrive at Earth and cause aurorae (commonly known as the Northern and Southern Lights), as the particles collide with atoms in the upper layers of the atmosphere. They can also cause geomagnetic storms, which in turn can disrupt electrical equipment on Earth.

The MESSENGER - Solar panels

The Sun has a very important role in the MESSENGER mission to Mercury. Mercury's surface reflects sunlight, and this reflected radiation is used to see features on the planet, in the same way that we see objects here on Earth during the day. The intense solar radiation also heats up Mercury's surface. The heated surface radiates infrared light into space. This infrared radiation can be used to determine the composition and other properties of the planet's surface. The MESSENGER spacecraft relies on solar radiation to produce electricity. Two solar panels, totaling 5.3 m2 in area, provide sufficient power for the spacecraft during the mission.

The Sun as a Star; Size

The Sun is a fairly typical star, just one of over 200 billion stars in our Galaxy, the Milky Way. It is not among the brightest or the faintest stars. It is not the most massive star; even though it is more massive than about 96% of the stars in the Milky Way, there are billions of stars more massive than the Sun. The Sun's radius is about 696,000 km (432,000 miles), roughly 109 times Earth's radius. This is the same ratio as between the height of an NFL linebacker (185 cm) and the size of a honey bee (1.7 cm).

The Sun in the Solar System

The Sun is at the center of the Solar System. The nine planets, their moons, as well as the smaller bodies— asteroids, comets, and small icy worlds in the outer reaches of the Solar System called Kuiper Belt Objects -- all revolve around the Sun. The Sun's central role comes from its high mass; it has 99.8 percent of the mass in the Solar System and, therefore, guides the movement of the other objects in the Solar System via gravitational forces. Radiation from the Sun also determines the conditions prevalent at the planets, from making the sunlit side of Mercury bake in 700 K (427˚C; 800˚F) heat to providing the hospitable environment for life on Earth.

The Sun as a Star; Gasses & Plasma

The Sun is made up entirely of gas, mostly of hydrogen (91% of the atoms) and helium (8.9%), with heavier ele- ments such as oxygen, carbon, neon and nitrogen mixed in to make up the remaining 0.1%. In the con ditions prevalent in the Sun, the gas is almost completely ionized-that is, the atoms have lost one or more of their electrons to become ions. This form of electrically charged gas is called plasma. The electric charge and high temperature make plasma's behavior so different from ordinary gas that some scientists call it a fourth phase of matter, separate from the traditional three (solid, liquid, and gas).

Sun's Total Power Output & Earth's Solar Constant

The Sun provides most of the energy on Earth. Some heat is generated inside the Earth, but it is a very small effect compared with sunlight. Without the Sun, the Earth would be cold and lifeless. Yet, only a small fraction of the energy produced by the Sun ever actually arrives on Earth; most of it is radiated in other directions toward the far reaches of space. The total power output of the Sun (the amount of energy radiated per second) is 3.83x1026 W (watt; joules per second). Since the radius of the Sun, Rs, is 696,000 km, the power output per square meter of the surface of the Sun is 6.29x107 W/m2 (3.83x1026 W / (4πRs2)). But since this energy is radiated in all directions, only a small part of it reaches the top of Earth's atmosphere. The amount of solar radiation arriving on Earth, known as the solar constant, is 1370 W/m2. This can be calculated by using the total power output of the Sun and spreading it over a sphere with a radius equal to the Earth's distance from the Sun.

Solar Power and Solar Energy

The Sun's energy can be harnessed to power human activities. Unfortunately, solar energy is spread over a large area and must be collected and concentrated to produce useable power. This is why, at the present time, solar energy is a more expensive power source than fossil fuels in most places and for most applications. Scientific and technological research is underway to make the use of solar power more efficient. But even now, nearly all the energy that we use is actually solar energy, just in a different form. For example, fossil fuels are made of plants that lived millions of years ago and stored solar energy in themselves before dying and becoming the fuels we use today.

The Sun's Internal Structure

The Sun's internal structure can be described in terms of several zones or layers. At the heart of the Sun is its core, which extends from the center to about one-fourth of the way to the surface. The maximum temperature in the core is over 15 million K, and this is where almost all of the Sun's energy comes from via nuclear fusion. The high temperature in the Sun's core is essential for the operation of the fusion process; otherwise joining hydrogen atoms together would not be possible.

The Sun's Magnetic Field

The Sun's magnetic field is created by the movement of plasma inside the Sun. The number of sunspots on the Sun's surface is a measure of (magnetic) activity in the Sun. The sunspot number changes from a minimum to a maximum and back to a minimum over a sunspot cycle, with an average period of about 11 years. At the end of the sunspot cycle the magnetic field of the Sun quickly changes its polarity (the region that used to be the magnetic north pole becomes the magnetic south pole, and vice versa). A similar change in the polarity of the Earth's magnetic field takes place, but on a much longer timescale— about 500,000 years or so—and not always at regular intervals.

Perfect Emitter & the Stefan-Boltzmann Law

The amount of electromagnetic radiation emitted by a body is directly related to its temperature. If the body is a perfect emitter (black body), the amount of radiation given off is proportional to the 4th power of its temperature as measured in Kelvin units. This natural phenomenon is described by the Stefan-Boltzmann Law. The following simple equation describes this law mathematically: E = Sigma (X) T 4th power. Where Sigma = 5.67 (X) 10 -8th power (X) Wm -2nd power (X) K -4th power and T= Temperature in Kelvin According to the Stephan-Boltzmann equation, a small increase in the temperature of a radiating body results in a large amount of additional radiation being emitted.

Industrial Revolution

The amount of heat energery added to the atmosphere by the greenhouse effect is controlled by the concentration of greenhouse gases in the Earth's atmosphere. All of the major greenhouse gases have increased in concentration since the beginning of the Industrial Revolution (about 1700 AD). As a result of these higher concentrations, scientists predict that the greenhouse effect will be enhanced and the Earth's climate will become warmer. Predicting the amount of warming is accomplished by computer modeling.

Energy

The capacity to do work

Specific Heat

The exact (specific) amount of energy it takes to raise the temperature of a kg of a particular substance by 1 K Unit: Joules / kg (X) k Each substances has its own specific heat value Things that warm or cool quickly have low specific heat Things that warm or cool slowly have high specific heats Water is KEY to weather and climate Water has a high specific heat: about 4190 J/(kg.K) For copper, specific heat is 386 J/(kg.K)

Reflection

The final process in the atmosphere that modifies incoming solar radiation is reflection (Figure 7f-3). Reflection is a process where sunlight is redirect by 180° after it strikes an atmospheric particle. This redirection causes a 100% loss of the insolation. Most of the reflection in our atmosphere occurs in clouds when light is intercepted by particles of liquid and frozen water. The reflectivity of a cloud can range from 40 to 90%. In this process, the solar radiation striking an atmospheric particle is redirected back to space unchanged.

The Greenhouse Effect

The greenhouse effect is a naturally occurring process that aids in heating the Earth's surface and atmosphere. It results from the fact that certain atmospheric gases, such as carbon dioxide, water vapor, and methane, are able to change the energy balance of the planet by absorbing longwave radiation emitted from the Earth's surface

Infrared Radiation from Earth's Surface

The heating of the ground by sunlight causes the Earth's surface to become a radiator of energy in the longwave band (sometimes called infrared radiation). This emission of energy is generally directed to space. However, only a small portion of this energy actually makes it back to space. The majority of the outgoing infrared radiation is absorbed by the greenhouse gases.

The MESSENGER - Intense Radiation

The intense radiation from the Sun is also a concern for the mission. While orbiting Mercury, the space- craft will get within 0.3 AU of the Sun. (Remember: One Astronomical Unit, AU, is the average distance from the Earth to the Sun; about 150 million kilometers, or 93 million miles.) The amount of sunlight to which the spacecraft is exposed depends on its distance from the Sun, R, as 1/R2. In other words, the MESSENGER spacecraft will be exposed to up to 11 times more sunlight than it would experience in orbit around Earth (1/0.32 = 11). Since the Earth's atmosphere allows only about half of solar radiation to pass through, the MESSENGER spacecraft will be exposed to as much as 22 times the amount of solar radiation as it would on the surface of Earth. This means that, unprotected, the spacecraft components could experience temperatures as high as 700 K (427 ̊C; 800 ̊F) or more, as happens on the sunlit areas of Mercury's surface.

Heat Capacity

The most common result of heat interacting with matter is a change in the material's temperature. The amount of heat needed to raise the temperature of one gram of a substance one degree Celsius is called the specific heat capacity (or just specific heat) of the sub- stance. Two substances with the same mass but different specific heats require different amounts of heat to reach the same temperature. For example, the specific heat of water is 4186 joules per kilogram per degree Celsius, while the specific heat of air is 1005 J/kg/ ̊C. This means that is takes over four times as much energy to heat 1 kg of water by 1 ̊C that it does to heat 1 kg of air. Heat can also change the size or physical state of the material, but these processes are not important in this lesson.

Convection Zone

The outermost layer of the Sun's interior structure is the convection zone, which goes from the outer edge of the radiative zone to the Sun's surface. The name comes from the fact that energy travels through this region via convective motions—hot regions in the bottom rise up while cooler material from above falls down.

Layers of the Solar Atmosphere

The photosphere is the lowest layer of the solar atmosphere. The bottom of this layer is the visible surface of the Sun, which has a temperature of about 5800 K (5500°C; 10,000°F). The next layer is the chromosphere, in which the temperature rises rapidly with increasing altitude. The uppermost level of the solar atmosphere is called the corona, which has temperatures of 500,000 K to 6 million K but is also very tenuous. The coronal gas is so hot that it emits X-rays and expands continuously outward to the rest of the Solar System as the solar wind, a fast outflow of electrons and ions.

Image; The Structure of the Sun

The solar interior consists of the core, the radiative zone, and the convective zone. Above the visible surface, the photosphere, are the chromosphere and the corona.

Wien's Law

The wavelength of maximum emission of any body is inversely proportional to its absolute temperature. Thus, the higher the temperature, the shorter the wavelength of maximum emission. This phenomenon is often called Wien's Law. The following equation describes this law: λ Max = C/T, when C is a constant = to 2897 and T is the Temperature in Kelvin. Wien's law suggests that as the temperature of a body increases, the wavelength of maximum emission becomes smaller. According to the above equation the wavelength of maximum emission for the Sun (5800 Kelvins) is about 0.5 micrometers, while the wavelength of maximum emission for the Earth (288 Kelvins) is approximately 10.0 micrometers. A graph that describes the quantity of radiation that is emitted from a body at particular wavelengths is commonly called a spectrum.

The MESSENGER - Protection

To make sure that the spacecraft components are not damaged by the intense solar radiation, a variety of solutions will be employed by the MESSENGER design team. For example, heat-resistant materials are used to build the components of the spacecraft, and a sunshade is constructed to protect the sensitive instruments from the Sun. The spacecraft's orbit around Mercury has been designed so that its closest approach to the planet is away from the most sun- baked region of the surface and so that it flies quickly over the sunlit areas. This is achieved by an orbit where the periapsis (the closest point to the surface of Mercury and also the part of the orbit where the spacecraft's speed is at its highest; the distance from the surface is 200 km, or 124 miles) is at a high latitude, and the apoapsis (the farthest point of the orbit and also the part of the orbit where the spacecraft's speed is at its lowest; the distance from the surface is 15,193 km, or 9443 miles) is far away from the surface of Mercury. This orbital design keeps the amount of infrared radiation received from the planet's extremely hot surface at safe levels. The solar panels are constructed from materials that can withstand high temperatures, and the system is designed so that the panels do not face the Sun directly. Using these precautions, the operating temperature at the solar panels is expected to be less than 135 ̊C, and the instruments are in a thermal environment comparable to room temperature: during Mercury's orbit around the Sun, the temperature on the instrument deck of MESSENGER is expected to vary from a few degrees below 0 ̊C (32 ̊F) to 33 ̊C (91 ̊F).

Mode of Energy Transfer; Conduction

Transfers energy between molecules in a solid or from a solid to a fluid surface Heating a pan on electric stove Stove element gets hot and heats pan bottom Pan gets hot and conducts heat to the water in it Molecules aren't displaced.

Water Droplets / H20

Water droplets are much larger than visible light wavelengths

Shortwave Radiation

Wavelengths < 4µm = More energetic Visible light is shortwave radiation. The Sun emits primarily shortwave radiation.

Longwave Radiation

Wavelengths > 4µm = Less energetic The Earth emits in the longwave region of the spectrum

Temperature through the day; Diurnal Temperature Cycle

What determines the temperature through the day? Amount of energy in, amount of energy out. On a clear night, what time does the lowest temperature occur? This cycle is an energy balance on its own Earth emitting IR (heat) (outgoing) Earth absorbing solar radiation (light) (incoming) Increase in temperature occurs when incoming > outgoing... otherwise temperature is falling Highest temperature: 2-4 p.m. Noon has most incoming energy, BUT, afternoon incoming energy is greater than outgoing energy Lowest daily temperature: shortly after sunrise Surface cools all night The daily temperature cycle also depends on cloudiness and geographic influences like water and mountains.

The Sun's "Surface"

When the Sun is observed with special instruments, it appears to have a surface. But since the Sun is entirely made of gas, it does not have a solid surface like Earth does. Instead, the apparent surface of the Sun is the region where the light that we see starts its journey toward us and where the visible solar features appear. On top of the basic granular surface appearance of the Sun, striking visible features include sunspots (relatively cool, darker regions), prominences (cool, dense plasma extending outward from the "surface,") and flares (great explosions on the most violent eruptions in the Solar System). The behavior of these surface features is largely guided by the Sun's magnetic field.

The Greenhouse Effect

With the Greenhouse Effect: Earth's average annual global temperature: 15o C Without the Greenhouse Effect Earth's average annual global temperature: -18o C Greenhouse effect impacts both Weather and Climate Greenhouse gasses absorb heat, increasing the temperature of the atmosphere

Heat Energy

a form of energy created by the combined internal motion of atoms in a substance

Specific Heat

equivalent to the heat capacity of a unit mass of a substance or the heat needed to raise the temperature of one gram (g) of a substance one degree Celsius. Water requires about 4 to 5 times more heat energy to raise its temperature when compared to an equal mass of most types of solid matter. This explains why water bodies heat more slowly than adjacent land surfaces.

Convection

involves the transfer of heat energy by way of mass movements of a substance in gas or liquid form in a vertical direction (horizontal transfer is called advection). Convection is often seen as rising masses of gas or liquid called convection currents.

Without the Greenhouse Effect

life on this planet would probably not exist as the average temperature of the Earth would be a chilly -18° Celsius, rather than the present 15° Celsius.

Albert Einstein

suggested early in this century that energy and matter are related to each other at the atomic level. Einstein theorized that it should be possible to convert matter into energy. From Einstein's theories, scientists were able to harness the energy of matter beginning in the 1940s through nuclear fission. The most spectacular example of this process is a nuclear explosion from an atomic bomb. A more peaceful example of our use of this fact of nature is the production of electricity from controlled fission reactions in nuclear reactors. Einstein also suggested that it should be possible to transform energy into matter.

Latent Heat

the energy needed to change a substance to a higher state of matter. This same energy is released from the substance when the change of state (or phase) is reversed. The diagram below describes the various exchanges of heat involved with 1 gram of water.

Electrical Energy

the energy produced from the force between two objects having the physical property of electrical charge.

Chemical Energy

the energy produced or consumed in chemical reactions.

Matter

the material (atoms and molecules) that constructs things on the Earth and in the Universe

Radiation

the only means of energy transfer that can occur across outer space. The transfer of radiation produced at the Sun's surface through space supplies the Earth with most of its energy.