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I) Sun, heat, temperature and radiation
A) Earth’s tilt and the seasons
1) Earth spins on its axis (rotates) as it orbits (revolves) around the Sun
(a) Axis is tilted at 23º with respect to the plane about which the Earth orbits
(b) Earth remains at same angle throughout its ellipse (path)
(1) Half of Earth is pointed at Sun
(i) Receiving more heat
(2) Other half is pointed away from Sun
(i) Receiving less heat
(3) On opposite side of Sun, the reverse is true
(4) Twice a year, equal amounts of sunlight are received by both Northern and Southern hemispheres
(i) Autumnal and Vernal Equinoxes
B) Electromagnetic radiation
1) Radiation is the only mechanism of heat transfer than can transit energy across empty space
2) Energy that powers our weather comes from the Sun
(a) Visible spectrum (white light) accounts for small part of the radiation from the Sun
(b) Vast majority of radiative energy is invisible
(1) Same form as light, different wavelengths
(i) Radio waves
(iii) Infrared waves
(iv) Ultraviolet waves
(vi) Gamma rays
C) Heat Transfer and the Greenhouse effect
1) 50% of the solar energy striking the surface is absorbed
(a) Atmosphere basically transparent to short wavelength, high energy light
(b) Not all light is reflected back into space
(c) Some is reflected back to Earth by carbon dioxide
(1) Greenhouse effect
2) Land heats faster and to higher temperatures than water and also cools faster
(a) Leads to great temperature variations for cities near coasts and those inland
(b) Body of water acts as a “brake” to moderate the temperature
D) Heat versus temperature
1) Heat is microscopic vibration of particles that constitute an object
(a) Heat is energy
2) Temperature is a way of comparing average energy of particles in one object to the energy in another
(a) Temperature is a measurement
E) Wind Chill effect
1) Created when cool air moves over a surface and carries away heat
F) Cloud formation
1) Cirrus Clouds
(a) Highest clouds
(b) 17,000 – 50,000 feet high
(c) Precede low-pressure systems that form rain and snow cloud
(1) Do not actually produce rain
2) Middle (Alto) Clouds
(1) 6,000 – 17,000 feet
(2) Fluffy, white – common on partly sunny days
(1) 6,000 – 17,000 feet
(2) Grayish, uniform clouds
3) Low Clouds
(1) Low, gray, cover uniformly
(1) Cause rain
(1) Stratus clouds, cover sky, but produce no rain
(1) Low, fluffy clouds that produce no rain
4) Cumulonimbus Clouds
(a) Lightning storms, hail and tornadoes
(b) Produced when unstable air (hotter than its surroundings) is lifted into atmosphere by a cold front
(c) Warm air is cooled, thereby producing rain
5) Mammatus Cloud
(a) Bulging, lumpy clouds located on the bottom of a Cumulonimbus cloud
(b) Associated with severe weather
6) Orographic Cloud
(a) Produced when warm air is lifted by mountains into the upper, cooler atmosphere
7) Mixed skies
(a) Characterized by several different types of clouds
The seasons occur because the tilt of the Earth's axis keeps a constant orientation as the Earth revolves around the Sun. When it is summer in the northern hemisphere, it is winter in southern hemisphere.
Click here for a visual table of the electromagnetic spectrum.
The Greenhouse Effect
Heat Index Chart
Wind Chill Chart
Forces leading to cloud formation
Under most circumstances, two or more lifting forces operate at the same time.
A. Density lifting causes a convection cell as warm, low-density air rises and cold, higher-density air sinks.
B. Frontal lifting. A warm front occurs when flowing warm air overrides cold air and is forced upward.
C. Frontal lifting. A cold front occurs when a wedge of forward-moving cold air slides under warm air and forces it upward.
D. Orographic lifting occurs when flowing air is forced upward by mountains or other sloping ground.
E. Convergence lifting occurs when masses of air collide and are forced upward.
The altitudes of clouds
An anvil head is the flattened top of a cumulonimbus cloud that spreads across the top of the troposphere.
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