Chapter 2 Notes

• Force=Mass*Acceleration
• Acceleration = change in speed or a change in directions of objects movement
• Work- done on an object, distance traveled times the force in the direction of that displacement.
• Energy- the capacity to do work.
• 4 Forms of Energy
• Kinetic- work that a body can do by virtue of its motion.
• Potential- work an object can do as a result of its relative position, represents stored energy that can be converted to other energy forms
• Heat
• Electrical
• Temperature- a measure of the average kinetic energy of a substance
• Calorie- unit used to measure energy, the energy needed to raise the temp of 1 gram of water 1 degree Celsius
• Joule-another unit used to measure energy
• Power- the rate at which energy is transferred, received, or released. Units for power are Watts (transfer of 1 joule of energy per second)
• Heat- the energy produced by the random motions of molecules and atoms, the total kinetic energy of a sample of a substance. Also, could be defined as the energy transferred between objects as a result of the temperature difference between them.
• Specific Heat- a low specific heat means a substance warms and cools easily, a high specific heat means it takes a lot of energy to change the temperature.

Methods of Energy Transfer

• Conduction- the process of heat transfer from molecule to molecule, requires contact, Example: when we touch something to see if it is warm or cold
• The ability of a substance to conduct heat by molecular motions is its thermal conductivity (wood has low conductivity, metal has high conductivity). Conduction not efficient for transferring energy on a global scale, only over small distances.
• Convection- the process of transferring energy vertically.
• Strong over deserts in the summer due to warming of sand. Inefficient mode of transfer in the poles due the surface air being cooler than the air above.

• Temperature Advection- horizontal transport of energy in the atmosphere
• Warm Advection- when warm air replaces cooler air. Cold advection is the opposite.
• Latent Heating- the heat absorbed or released per unit mass when water changes phases
• Latent heat of melting- energy absorbed by water to change ice to liquid water
• Latent heat of fusion- amount of energy released to the environment when water freezes
• Latent heat of vaporization- amount of heat required to evaporate liquid water
• Latent heat of condensation- the amount of energy released when water vapor condenses to liquid form
• Deposition- Phase change from gas to solid
• Sublimation- Phase change from solid to gas

• Sublimation, Evaporation, and Melting are all cooling processes (removes energy from the atmosphere)
• Condensation, Freezing, and Deposition are warming processes (add energy to atmosphere)

Radiative Heat Transfer

• Radiation- energy in the form of waves that are not composed of matter
• Waves characterized by two properties: Wavelength (distance b/tw wave crests), Amplitude (half the height from the peak of the crest to the lowest point of the wave)
• Radiation Law- all objects with a temperature above absolute zero emit radiation.
• A warmer object emits more radiation that a cold object.
• Wien’s Law- the hotter the object, the shorter the wavelength of maximum emission of radiation.
• When radiation interacts with an object it can be: Absorbed, Reflected, or Transmitted (ART)
• Albedo- describes the percentage of light an object reflects (Snow has high albedo)
• The amount of radiation energy the atmosphere absorbs depends on radiative properties of the material, amount of time exposed to energy, the amount of material, the proximity to the energy source, and the angle at which radiation occurs.
• Blackbody- an object that absorbs all the electromagnetic energy that falls on the object
• Kirchhoff’s Law- a good absorber of radiation is also a good emitter of radiation at that same wavelength.

Sun and Seasons

• The Earth’s tilt, not the distance from the sun, causes the seasons.
• The tilt is referred to as the angle of inclination.
• As the Earth orbits around the sun in an ellipse shape, the distribution of sunlight changes on the Earth’s surface at a given latitude.
• Solstice- Sun’s rays strike the equator at an angle of 23.5 degrees (June 21, Dec 21)
• Equinox- Sun’s rays strike the equator at an angle of 90 degrees (March 21, Sept. 22) -- All locations on Earth experience both 12 hours of daylight and darkness.
• Solar Zenith Angle- the angle at which the Sun’s energy strikes a particular location on Earth. (0 degrees when Sun is directly overhead and increases as Sun sets until Sun is on the horizon and the angle is 90 degrees).
• A larger zenith angle means more solar energy is distributed over a larger area, thus it receives less energy. This is because the Sun’s energy must pass through more atmosphere, giving solar energy more change of atmospheric absorption.
• The further poleward you travel, the more daylight you have during the summer and the fewer daylight hours in the winter.

Radiative Properties of the Atmosphere

• Atmospheric gases are selective in the solar wavelengths that they absorb.
• The atmospheric window (10-12 micrometers spectral region) allows the Earth to cool off and emit its energy to outer space.
• Clouds are good reflectors of solar energy, and they are good emitters and absorbers of longwave energy.
• The Greenhouse Effect- It is caused by the Earth’s surface being heated by shortwave and longwave absorption emitted by gases (such as water vapor and CO2) in the atmosphere. If it did not occur, the Earth surface would be 60 degrees F cooler than it is today.
• The enhanced Greenhouse effect is used to explain the relationship between the observed rise in global temperatures and an increase in atmospheric carbon dioxide
• Increased carbon dioxide produces more infrared energy being absorbed which warms the atmosphere. The now-warmer atmosphere will then emit more longwave energy than it did previously and will increase the longwave energy hitting the Earth’s surface warming it too.
• Greenhouse gases are transparent to solar energy and absorb terrestrial energy and warm the atmosphere b/c they allow solar energy to reach the surface and inhibit longwave radiation from going to space. (Ex: water vapor, CO2, methane)
• Radiative Balance- when the energy losses equal the energy gains
• The tropics gain and the poles lose radiant energy on a yearly basis, so the energy must be transported between the tropics to the poles to balance each other. This transport is done through the atmosphere and ocean currents and is major reason for weather occurring.
• Heat Transfers- Sensible and Latent Heat transfers