Download weather ch17 2014 notes - Clinton Public School District

Chapter 17, 2014 Weather
Heat is a major factor in weather: movement of heat in atmosphere causes
temperatures to change, winds to blow and rain to fall. Electromagnetic waves:
forms of energy that travel in waves.
Most of energy from sun reaches earth in form of visible light and infrared
radiation and a small amount of UV radiation.
Infrared: longer than red light: not visible: but can be felt as heat: heat lamps:
food: use both.
Sun also gives off uv radiation: wavelengths shorter than violet: sunburns: skin
cancer: eye damage
Energy in atmosphere:
Before sun’s ray can reach earth’s surface, they must pass through atmosphere
1. some is absorbed within atmosphere
2. water vapor and carbon dioxide absorb some infrared
3. ozone layer in stratosphere absorbs most of uv
4. clouds, dust and other gases also absorb energy
5. some layers are reflected: clouds are like mirrors: dust particles and
molecules of gas in atmosphere reflect light from sun in all directions:
Reflections of light in all directions is called scattering.
When earth’s surface is heated it radiates some of the energy back into
atmosphere as infrared radiation: most ofthis cannot travel all the way through
atmosphere and back into space: instead much is absorbed by water vapor, carbon
dioxide, methane and other gases: the energy from absorbed radiation heats
gases in the air: forms a blanket around the earth that holds heat in atmosphere:
process is called GREENHOUSE EFFECT.
Sec 2-2: Heat transfer:
Gases are made of small particles, molecules, that are constantly moving: faster
they move, the more energy they have.
The total energy of motion in molecules of a substance is called THERMAL
ENERGY.
TEMPERATURE IS THE AVERAGE AMOUNT OF ENERGY IN MOTION OF EACH
MOLECULE OF A SUBSTANCE.
Heat is transferred in 3 ways:
1. radiation: direct transfer of energy by electromagnetic waves, feel the
warmth of sun on our faces, campfire: infrared radiation:
2. conduction: barefoot on hot sand: fast moving molecules bump into nearby
slower moving molecules: direct transfer of heat from one substance to another:
that it is touching:
Conduction is most effective the closer the molecules in a substance : solids,
metals, glass
3. convection: transfer of heat by movement of a fluid: fluid being a fluid or a
gas. Heating house, room
READ PAGE 50 HEAT TRANSFERS IN TROPOSPHERE
Chapter 2, Sec 2-3
Because air is fluid, it moves easily from place to place: the force that makes air
move is caused by difference in air pressure: fluids ten to move from areas of
high pressure to low pressure
Wind: horizontal movement of air from an area of high pressure to an area of
lower pressure. All winds are caused by difference in air pressure: most caused
by unequal heating in atmosphere
Anemometer: instrument used to measure wind speed.
Wind vane: measure wind direction. NAME OF WIND tells you where wind is
blowing from: south wind is blowing from south to north
Wind chill factor: the increased cooling that a wind can cause.
Local winds: winds that blow over short distances caused by unequal heating of the
Earth’s surface over a small area.
Sun heats land faster than water: during the day, air over land becomes warmer
than air over water.
Sea breeze: cool air blows inland from the water: moves underneath warm air on
land
Land breeze: flow of air from land to a body of water
Monsoons: sea and land breezes over a region that change direction with the
seasons.
Global winds: winds that blow steadily from specific directions over long distances
Warm air rises at the equator and cold air sinks at the poles, causing winds at
the Earth’s surface to blow from the poles to the equator…higher in the
atmosphere, air flows away from equator to poles. The movement of air between
equator and poles produces global winds.
Coriolis Effect: the Earth’s rotation makes winds curve.
Because the earth’s rotation global winds do not blow in straight line: as winds
moves, earth rotates west to east underneath them, making it seem as if winds
have curbed: the way the rotation makes winds curve is Coriolis effect.
In the Northern Hemisphere, all global winds gradually turn toward right: In
Sourthern Hemisphere, all global winds gradually turn toward left.
Coriolis effect produces patterns of calm areas and wind belts around Earth:
Calm areas include doldrums, horse latitudes
Major global wind belts:
Horse latitudes: between 30degrees north and 30degrees south, latitudes are
horse latitudes where air stops moving toward poles and sinks. Sailors used to
have to throw their horses overboard as there was not enough wind to move ship.
Trade winds: between the equator and 30˚ North and South latitude: cold air
over horse latitudes sinks, produces an area of high pressure, this high pressure
causes surface winds to blow both toward and away from equator: winds that blow
toward the equator are turned west by Coriolis effect: winds in the N.
Hemisphere between 30 degrees N latitude and equator generally blow from the
NE.
In the S. Hemisphere 30 degrees south latitude and equator generally blow
from SE….steady easterly winds, sailors, etc.
Prevailing westerlies: between 30˚ and 60˚ North and South latitude. Mid
latitudes: winds that blow toward poles are turned east by the Coriolis effect,
they blow from west to east: prevailing westerlies between 30 degrees and 60
degrees north latitude blowe from SW: between 30 degrees and 60 degrees south
latitude, they blow from NW: SHOW TRANSPARENCIES
PREVAILING WESTERLIES PLAY IMPORTANT ROLE IN WEATHER CHANGE
IN US.
Polar easterlies: between 60˚ North and South latitudes and the poles. Cold air
sinks near poles and flows back toward lower latitudes: Coriolis effect shifts
these polar winds to west. Polar easterlies meet prevailing westerlies at about 60
degrees north and 60 degrees south latitudes along a region called the polar
front: mixing of warm and cold air along polar front has major effect on weather
changes in US
Jet stream: 10km above the Earth’s surface: bands of high speed winds that blow
WEST to EAST. (Usually in wavy bands) can reach 200 to 400 mph. As they
travel around earth they wander north and south. Airplanes can use them to help
when traveling east:
Sec 2-4:
Evaporation: process by which water molecules in liquid water escape into air as
water vapor
a. some forms clouds (condensation)
b. water is constantly moving between Earth and atmosphere
Humidity: measure of the amount of water vapor in the air. Relative humidity:
the percentage of water vapor in the air compared to the maximum amount the air
can hold. At 10 degrees C 1 cubic meter of air can hold a maximum of 8 grams of
water vapor: so if humidity is 4 grams, then relative humidity would be 50%.
SHOW OVERHEAD TRANSPARENCY AND GRAPHING EXCERISE (READING
AND INTERPRETATION)
Psychrometer: instrument with two thermometers-one wet bulb and one dry bulb,
that measures relative humidity.
Condensation: process by which molecules of water vapor in the air become liquid
water
a. as air cools, amount of water vapor it can hold decreases.
b. when air becomes saturated, water vapor in air condenses.
Dew point: temperature at which condensation begins
Clouds are formed when warm air rises and water vapor condenses.
3 Types of clouds: CLASSIFIED BY ALTITUDE
Cumulus: fluffy, rounded piles of cotton: usually indicate fair weather. USUALLY
LESS THAN 2 KM ABOVE GROUND
Stratus: form in flat layers, covers most or all of sky: when they thicken they may
produce drizzle rain or snow but are then called nimbostratus: stratus clouds that
produce rain/snow
Cirrus: wispy, feathery clouds: very high: made mostly of ice crystals
Clouds that form near the ground are called fog: usually forms when the ground
cools at night after a warm, humid day.
Chap 2, Sec 2-5
Precipitation: any form of water that falls from clouds and reaches the Earth’s
surface
a. cloud droplets or ice crystals grow heavy enough to fall through the air
b. one way clouds grow is by colliding and combining with other cloud droplets.
Common types o f precipitation:
Rain: 0.5 millimeters in diameter
Sleet: ice particles < 5 millimeters in diameter
Freezing rain: raindrops that freeze on a cold surface
Hail: round pellets of ice > 5 millimeters
Snow: water vapor in cloud that is converted directly to ice crystals: snow flakes
(6 sided)
MOST COMMON TYPE OF PRECIPITATION IS RAIN.
Meteorologists: scientists who study causes of weather and try to predict it.
Rain gauge: open ended tube that collects rainfall: 10 centimeters of snow
contains approximately 1 centimeter of rain.
Droughts: long periods of unusually low precipitation that can cause great
hardships