Unit 9: Weather and Climate- Part 2
I Forecasting the Weather
A. Air Masses : are large bodies of air with
nearly the same temperature and
humidity features.
(Text p.560)
1. The temp. and humidity features of an
air mass are determined by where it
formed. This is called its
Source Region .
2. Air Mass Vocabulary

Polar (P): Cold air. Formed at a high latitude

Tropical (T): Warm air. Formed at a low latitude


Continental (c): Dry air. Formed over land.

Maritime (m): Moist air. Formed over a large body of water.
3. Air Mass Types:
Name Symbol Features Possible
Source Region
(see text p.560)
Continental polar
Continental tropical cP Cold, dry Central
Canada mP
Warm, humid
View satellite movies of air masses moving across North America.
Air Masses - YouTube 1

B. Weather Fronts: form where two air masses meet.
(text p.565-567)
1.
Cold Fronts : form when cooler air
pushes into a warmer air mass. (p. 566)
[Diagram: cross section, map symbol] animation:
Compare and contrast warm and cold fronts.
Cold fronts bring brief but heavy precipitation followed by cooler, drier weather.
2. Warm Fronts : occur when warmer air
pushes into a cooler air mass. (p.565)
[diagram-cross section, map symbol] animation:
Compare and contrast warm and cold fronts.
Warm fronts bring long lasting, light

precipitation, followed by warmer more humid air.
3.
Stationary Fronts : occur at a boundary where neither air mass is moving
[map symbol]
4. Occluded Fronts : occur where two
cooler air masses lift a warmer air mass
completely off the ground.
[map symbol, p.567]
Current US Fronts: current US surface map
Fronts-Hommocks Earth Science Department - YouTube
C. Information on a Weather Map:
(See text p.746, ESRT p.13)
1. Review:


Isobars show lines of equal air pressure and identify centers of Low and High
Pressure.
AMS The DataStreme Project

Fronts mark boundaries of air masses and areas of unsettled weather.
AMS The DataStreme Project current US surface map
2. Station Model Symbols describe the
weather conditions in major cities.
Station
Model
(See ESRT p.13)
[Draw B,C, and D]
A
(ESRT p.13)
B
(on board)
28
C
(on board)
D
(on board)
E
(RVC)
Air Temp.
(F.)
Dewpoint
Temp. (F.)
% Cloud
Cover
27
75

Wind
Direction
SW
Wind
Speed(knots)
Air Pressure
(mb)
15
1019.6
Present Snow
Weather
0.5 --- --- --- --- Visibility
(miles)
Air Pressure
Trend (mb.)
+1.9 --- --- --- ---
Converting Air Pressure:

If air pressure # is less than 500, put a
“10” in front and decimal before last number.
Ex. 125 = 1012.5 mb.

If air pressure # is greater than 500, put a
“9” in front and decimal before last number.

Ex. 997 = 999.7 mb.
11570 Weather Forecast and Conditions
[Fill in chart for RVC]
YouTube - Reference Table Page 13-The Station Model-Hommocks Earth
Science Department
II Storms : are caused by intense low
pressure systems.
A.
Thunderstorms occur when moist, warm air rises quickly.
(see text p. 571-572)
[Diagram]
Observe an animation of a thunderstorm.
1.
Friction of raindrops builds an electric charge causing lightning .
2.
Sudden heating and expansion of air causes thunder.
Lightning Strikes! - YouTube

B.
Mid Latitude Cyclones : are low pressure systems that form between 30 and 60 degrees of latitude. (p.568)
Visualizing a Mid-Latitude Storm System
1. They move from west to east across the
U.S. (see text p.569)
Examine how barometric pressure changes with weather conditions.
2. High altitude winds called the
Jet Stream determine the exact path.
Great Rivers of Air
NOVA Online | Vanished! | Five-day view of the jetstream
CRWS Jet Stream Map Menu
3. These storms are sometimes called
“Nor’Easters”
because the wind often
blows from the Northeast. ex. “The Perfect Storm”
NCDC: Satellite Events Art Gallery: Cyclones

Historic Halloween Storms - weather.com
YouTube - The Perfect Storm
4. In Winter, strong winds and snow can
combine to form a Blizzard.
C. Hurricanes are powerful low pressure systems that form over the tropical
ocean .
Also called
“Cyclones”
or
“Typhoons”
(see text p.575-577)
Worldwide Tropical Cyclone Names
Geophysical Fluid Dynamics Laboratory - Visualizations - Hurricanes
Observe an animation of a hurricane.
1.
Hurricanes gain strength from warm water.
They lose strength rapidly when moving over land or cooler water.
2.
Winds can exceed 200 mph!

3.
Hurricane intensity is measured using the
Saffir-Simpson Scale (1-5)
(text p.577)
4.
Small area of sinking air in the center is called the Eye .
(text p. 576)
5.
Atlantic Hurricanes follow a standard Storm Track :
West-NW-N-NE
(See text p.584 #30-34) atlantic hurricane tracks - Google Search
2005 Tropical Storm/Hurricane tracks - YouTube
6.
Most hurricane damage occurs in coastal areas by large waves and rise in sealevel called a
Storm Surge
YouTube - Hurricane Katrina: Extreme Video

Long Island Storm Surge Maps
Hurricanes 101 - YouTube
D. Tornadoes : are the most powerful storms on Earth.
[diagram] website:
Tornado Formation
1. Winds can exceed 300 mph!
2. Average diameter only about 0.25 miles.
Examine an animation of a tornado.
3. Intensity is measured using the
Fujita Scale(0-V) text p.574
The Fujita Scale of Tornado Intensity
Tweaking a twister
Top Ten US Killer Tornadoes
Tornado Destruction - YouTube
Inside the Tornado - YouTube
Youtube video lesson: hurricanes and tornadoes

III Climate : the average weather
conditions over a long period of time.
Climate includes the avg. temperature and avg. moisture .
A. Factors Affecting the Avg.Temperature
1. Latitude : The greater the lat., the
lower the avg. temperature.

This occurs because the greater the lat., the lower the angle, and the weaker, the suns rays are.
[Diagrams- demo]

Insolation is the in coming sol ar radi ation

The greater the angle of insolation , the greater the intensity of insolation.

[Graph]

The angle of insolation depends on the
Season and time of day. lat. and suns path
2. Elevation : the greater the elev., the
lower the avg. temperature.
The temp. decreases about 1 C. for every
100 m. rise in elevation.
[Diagram] example: Mt. Kilimanjaro in Kenya http://www.pbs.org/wgbh/nova/kilimanjaro/tour.html
NOVA | Volcano Above the Clouds | Preview –
3. Large Bodies of Water decrease the temperature range of nearby land.
This makes warmer winters and cooler
summers.

This is because water surfaces heat up and cool down much slower than land surfaces.
Example: Long Island
[graph: n. hem. Inland / coastal]
Other Climate graphs to know: See text p.596-597
Interactive Climate Map
[graphs: s. hem., tropical]
4. Ocean currents : modify the climate of nearby land masses.
Finding Nemo - Fin, Noggin', Duuude! - YouTube
See ESRT p.4 examples:

The Gulf Stream warms the climate of western Europe. ocean.currents


The California Current cools west coast of U.S.
Variations in Temperature
B. Factors Affecting Moisture global.annual.precip
1. Sides of mountains facing the prevailing winds ( windward side ) are cool and moist.
Other side of mountains ( leeward side ) are warm and dry.
[Diagram]
Mountain Weather (Flash) | PBS examples: Death Valley; Arica (Chile): worlds driest place
2. Prevailing Winds form humid zones at
0°, and 60° of latitude.
Desert Belts form at 30°, and 90° of lat.
See ESRT p.14

global wind and climate animation
YouTube - Climatic Conditions
3. El Nino is an unusual warming of the
Water along the west coast of South
America.

It occurs every 3-10 years.

This affects global wind patterns and world climates
Brian Slocum Explains El Nino - YouTube
Can We Blame El Niño for These Events?
IV Climate Change
A. The Earths Climate has changed through geologic time.
How do we know?
Study of deep sea sediments
. deep sea sediment cores - Google Search
Study of ice cores .
Drilling for ice - Horizon - Big chill - BBC - YouTube

What the data shows:
Long term :
Temperature and CO2 concentration past 400 000 years
Shorter term : temperature variation 2000 years
1. Colder times are called Ice Ages .
2. Warmer times are called Interglacials .
3.
Much of these changes may be caused by changes in the Earths orbit around the sun.
How an Ice Age is born - YouTube
B. The Greenhouse Effect
What is a greenhouse?
How does it work?
[Diagram- Greenhouse]
1.
Sunlight is composed of many types of
Electromagnetic Energy
Review ESRT p.14.

2.
The greatest intensity of sunlight, at the
Earths surface, is in the visible wavelengths.
[set up diagram]
3. Some of this visible light is absorbed by the Earths surface and reradiated as infrared heat . [add to diagram]
4. Much of this outgoing heat is absorbed by Greenhouse Gases such as

Carbon Dioxide (CO
2
)

Methane (CH
4
) and

Water Vapor (H
2
O)
[add to diagram]
Greenhouse Effect - animated diagram
5. The Greenhouse Effect helps keep the
Earth comfortably warm and makes life possible.
C. Global Warming

1. Human activities are increasing the amount of greenhouse gases in the atmosphere.
2. These activities include

Burning fossil fuels (gas, oil, coal)

Deforestation (chopping down trees and burning wood.)

Raising Cattle and Rice.
3. This increases the amount of heat energy trapped, warming the Earths climate.
Is the Earth really warming?
(see text p.602-603)
If you are not sure if global warming is real- check out these animations:
The Habitable Planet 12 - Earth's Changing Climate - Visuals
3.
Possible Effects of Global warming
(based on computer models)

Change in climate patterns.


Increased number and strength of hurricanes

Melting of the polar ice caps and rise in sealevel.
NOVA: Secrets Beneath the Ice