Download Chapter 21, guest starring Ch. 20, Section 2

Chapter 21, guest starring Ch. 20, Section 2
Vocabulary
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
Coriolis effect
21.
Trade winds
22.
Westerlies
23.
Easterlies
24.
Doldrums
25.
Horse latitudes
26.
Air mass
27.
Continental polar air mass 28.
Continental tropical air mass 29.
Maritime polar air mass
30.
Maritime tropical air mass 31.
Cloud
32.
Troposphere
33.
Advective cooling
34.
Stratus clouds
35.
Nimbostratus
36.
Altostratus
37.
Cumulus clouds
38.
Cumulonimbus
39.
Altocumulus
40.
Stratocumulus
Cirrus clouds
Cirrocumulus
Cirrostratus
Crepuscular rays
Fog
Radiation fog
Advection fog
Upslope fog
Steam fog
Front
Cold front
Warm front
Squall line
Stationary front
Occluded front
Polar front
Midlatitude cyclones
Anticyclones
Thunderstorm
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
Cumulus stage
Mature stage
Dissipating stage
Lightning
Thunder
Hurricane
Latent heat
Storm surge
Saffir-Simpson scale
Tornado
Barometer
Anemometer
Wind vane
Radar
Station model
Isotherms
Isobars
Watch
Warning
Cloud seeding
I.
Air Masses
A. Air Movement
1. Uneven heating of Earth’s surface causes differences
in air pressure
a.
b.
c.
Equator gets more solar energy than poles
Heated air rises – creates low-pressure system
Cold air sinks – creates high-pressure system
Air moves from high-pressure areas to low-pressure
areas
2.
a.
b.
So surface air usually moves from poles to equator
At high altitudes, air moves from equator to poles
3. Differences in temp & pressure create wind belts
a.
b.
c.
d.
3 wind belts in each hemisphere (Northern & Southern)
i.
Trade Winds: 0° - 30°
ii.
Westerlies: 30° - 60°
iii.
Easterlies: 60° - 90°
Wind belts are influenced by the Coriolis effect – Earth’s
rotation causes wind deflection
Doldrums: low-pressure zone at equator (0°)
Horse latitudes: high-pressure zones at 30° N and S
B. Formation of Air Masses
1. Air mass: large body of air with nearly uniform
conditions of temperature and moisture content
2. Temperature of air masses usually depend on the
climate where they form
a.
b.
Polar regions have cold, dry air masses
Tropical oceans have warm, wet air masses
C. Types of Air Masses
1. Classified according to where they form
2. Take on characteristics of areas where they form
3. Continental air masses develop over land & usually have low
humidity – bring dry conditions when they travel
1.
2.
Continental tropical (cT): form over warm, dry areas of land (southwest
U.S.)
Continental polar (cP): form over cold, dry areas of land (polar Canada)
Maritime air masses develop over water & have high humidity –
bring precipitation & fog when they travel
4.
1.
2.
Maritime tropical (mT): form over warm, wet areas (tropical Pacific &
Atlantic)
Maritime polar (mP): form over cold, wet areas (polar Pacific & Atlantic)
D. Air Masses in North America
1. Continental air masses
a.
i.
b.
i.
Continental tropical develop over deserts in southwest U.S.
Bring hot, dry weather in summer; don’t form in winter
Continental polar develop over northern Canada where it’s covered
with snow/ice & move into the northern U.S.
Bring cool, dry weather in summer; very cold weather in winter
(polar vortex!)
Maritime air masses
2.
a.
b.
Maritime tropical develop in warm areas of Atlantic, Caribbean, &
Gulf of Mexico, then travel to eastern U.S.
i.
Bring hot, humid weather in summer; mild, cloudy weather in
winter
Maritime polar develop in north Pacific & move into northwest U.S.
i.
Bring cool, foggy weather in summer; rain & snow in winter
ii.
Sometimes dry out as they move over mountains in western U.S.,
bringing cool & dry weather to central U.S.
Fronts
 See Interactive Reading Packet
Clouds (Chapter 20, section 2)
A.
Cloud: collection of small
water droplets or ice
crystals suspended in the
air; forms when air is
cooled & condensation
occurs
1. Form in troposphere:
lowest layer of the
atmosphere, about 7
miles thick
B.
Advective Cooling:
process by which
temperature of an air mass decreases as it moves over a cold surface;
causes air to cool & form clouds
C. Types of Clouds
1. Stratus Clouds: found 0 – 6500 ft. above Earth’s surface
a.
b.
c.
d.
e.
Have a flat, uniform base
Cover large areas of sky, may block out sun
Rarely produce precipitation
Nimbostratus: dark gray, produce heavy precipitation
Altostratus: type of stratus cloud that occurs at middle altitude;
usually doesn’t produce precipitation
2. Cumulus Clouds: vertical clouds with dark bottoms &
cotton-y looking top
a.
b.
c.
d.
e.
Form when warm, moist air rises & cools
Height depends on stability of troposphere
a.
Tallest clouds form on hot, humid days
Cumulonimbus: high, dark storm clouds; produce thunder,
rain, lightning, & other severe weather
Altocumulus: mid-altitude cumulus clouds; thunderstorms may
follow
Stratocumulus: low-altitude clouds that are combination of
stratus & cumulus
3. Cirrus Clouds: thin, feathery clouds formed above
20,000 ft. above surface
a.
b.
c.
d.
Composed of ice crystals
Usually indicate fair or pleasant weather
Cirrocumulus: high-altitude, small puffy clouds; indicate
upcoming snowfall or rainfall
Cirrostratus: long, thin clouds covering most of sky; may cause
halos!
4. Crepuscular rays: rays of sunlight that stream through
gaps in clouds, especially stratocumulus
5. Fog: water vapor condensed near Earth’s surface;
essentially clouds that form on the ground
a.
b.
c.
d.
Radiation fog: forms from nightly cooling of earth; thickest in
valleys & low elevations
Advection fog: forms when warm, moist air moves across a
cold surface; common along coasts & over oceans
Upslope fog: forms by lifting & cooling of air as air rises over
land slopes (hills, mountains, etc.)
Steam fog: shallow layer formed when cool air moves over a
warm body of water (rivers)
III. Weather Instruments
A. Lower Atmosphere Weather
1. Thermometer: indicates & measures temperature
a.
b.
c.
Usually uses mercury or alcohol in a sealed glass tube
Rise in temp. causes liquid to expand & fill more of the tube
Electric thermometers are based on electrical currents that
increase with temperature
2. Barometer: measures air pressure, can indicate fronts
approaching
3.
4.
Anemometer: measures wind speed
a.
Small cups are attached to a rotating base -- wind
pushes the cups & causes the base to rotate,
which triggers an electrical signal to register wind
speed
b.
Used at airports to determine flight conditions
Wind vane: determines wind direction
a.
Arrow-shaped device rotates as tail catches the
wind
b.
Described using compass directions
B. Upper Atmosphere Weather
1. Radiosonde: group of instruments carried by balloons to
measure conditions in the upper atmosphere
a.
b.
Sends measurements as radio waves
Path of balloon is tracked to determine speed & direction of winds
Radar: uses reflected radio waves to determine the velocity &
location of objects
2.
a.
Can track precipitation & thunderstorms through how radar pulses
reflect off of water particles
Satellites are used to monitor weather that cannot be
tracked from the ground
4. Computers store weather data, solve complex equations
about atmospheric tendencies, and provide more reliable
forecasts
3.
IV. Forecasting Weather
A. Global Weather
1. Monitored by the World Meteorological Organization
a.
b.
c.
World Weather Watch enables the rapid exchange of weather
data around the world
Helps establish &
improve forecasting
in developing
countries
Offers insight about
how weather impacts
human activities
2.
Weather Maps
a.
Used to communicate a lot information at once
b.
Station model: group of symbols indicating weather
conditions at a given location
i.
Cloud cover, wind speed, wind direction, dew
point, temperature, atmospheric pressure, etc.
c.
Different types of lines are used on weather maps
to indicate conditions
i.
Isotherms: connect points of equal temperature
ii.
Isobars: connect points of equal atmospheric
pressure
3.
Forecasts
a.
Weather data gathered from radar, satellites, and other
instruments are input into computer models to create
forecasts
b.
Meteorologists compare models to create more reliable
predictions
c.
Relatively easy to determine temperature, pressure,
wind speed & direction, but can be difficult to anticipate
precise timing & amount of precipitation
d.
Severe weather predictions have different levels:
i.
Watch: conditions are ideal for severe weather
ii.
Warning: severe weather has been spotted or is
expected within 24 hours
4.
Controlling Weather
a.
Scientists are currently investigating if there are ways to
control rain, hail, and lightning
b.
Cloud seeding: produces rain through adding particles to
clouds that cause them to produce precipitation
i.
Can be used to prevent more severe precipitation, like
cause rain instead of hail
c.
Attempts at hurricane control have been generally
unsuccessful
d.
It is possible to generate
artificial lightning, but
there is no conclusive
information about
modifying preexisting
lightning