Class Notes and Powerpoints

Weather Notes

1.  Weather

2.  Weather is the condition of the Earth’s atmosphere at a particular place and time

2.  It is the movement of energy through the atmosphere

              3.  Energy comes from the Sun

                     4.  The sun is the force that drives weather

              3.  The sun’s energy interacts with earth’s atmosphere


A.  50 % absorbed by earth’s surface.  This heats the land and water

B.  Some absorbed energy is radiated back to the atmosphere.  As infrared radiation

C.  5% is reflected by the surface back into the atmosphere

D.  20% is absorbed by gases and particles in the atmosphere

E.  25% of incoming sun is reflected by dust, clouds, & particles

1.  Heat Transfer

2.  Conduction: direct transfer from one substance to another (touching)

2.  Radiation: direct transfer of heat by electromagnetic waves (through space)

2.  Convection: transfer of heat by the movement of fluid (liquid or gas)


1.  Wind

2.  Wind is the horizontal movement of air from an area of high pressure to an area of low pressure

              High pressure                                Low Pressure

       2.  Difference in pressure

              3.  Caused by the unequal heating of the atmosphere

                     4.  The hot air (by equator) rises

4.  The cool air sinks or rushes to replace the rising air

       2.  Measure wind

              3.  Use anemometer

                     4.  unit of measure m.p.h. (miles per hour)

2.  Wind chill: the blowing of wind on your skin makes you feel colder

       2.  Local winds: winds that blow over a small area

              3.  Caused by unequal heating in a small area

4.  Examples

5. Sea Breeze: cool air blows from water toward land where hotter air has risen

5.  Land Breeze: land cools faster than body of water at night

              6.  Hot air over water expands and rises

6.  Cool air from land rushes in over the water

2.  Global winds: winds that are caused by unequal heating of the globe

              3.  Occurs over large areas

3.  Form from giant convection currents in the atmosphere

4.  (Hot à up, Cold à down)

4.  Air pressure at the poles is higher than air pressure at the equator


3.  Coriolis Effect: global winds curve due to the rotation of the earth.

4.  The Coriolis effect is the way the earth’s rotation makes the wind curve

              4.  Winds in North curve right toward equator

              4.  Winds in South curve left toward equator

2.  Calm Areas

       3.  Doldrums: area near the equator

4.  The hot air rises and is replaced by cold air, but the cold air is heated so quickly there is not much horizontal movement

3.  Horse latitudes: occur at 30o North and South of equator

              4.  Cool air sinks: very calm area

2.  Global wind Belts

3.  Trade winds: blow from the horse latitudes toward the equator

              4.  Used for trade routes

3.  Polar easterlies: Cold air near the poles sinks and flows back toward the lower latitudes

4.  Coriolis effect shifts these winds so they meet prevailing westerlies

              5.  Creates the polar front

3.  Prevailing westerlies: occur in the mid-latitudes (30o-60o N & S)

4.  These blow towards the poles

4.  Very important to weather in the USA

2.  Jet Stream: bands of high speed air 10 km above the earth (200-400 km/hr)

       3.  Blow from West to East


Water in the Atmosphere

1.  Humidity

2.  Humidity: is a measure of the water vapor in the air

              3.  Warm air can hold more H2O vapor than cool air

2.  Relative Humidity:  The actual amount of water vapor the air can hold at a particular time

2.  Dew Point: The temperature where condensation begins

       3.  When water vapor turns to liquid water


1.  Clouds

2. Clouds form when water vapor in the air condenses to form liquid water or ice crystals

3.  Condensation occurs when the temperature changes and has small particles to rest on

       4.  Dew: condensation on a surface

       4.  Frost: condensation on a surface at a Temperature below freezing

       2.  Three main types of clouds

              3.  Classified by their altitude

              3.  Cirrus: wispy feathery “hooked ends”

                     4.  only at high altitude

                     4.  made of ice crystals

                     4.  storms is coming

              3.  Cumulus: fluffy white

                     4.  Some indicate fair weather

                     4.  others indicate thunderstorms (cumulonimbus)

                           5.  nimbus means rain

              3.  Stratus: flat layers

                     4.  can produce drizzle, rain or snow

                     4.  Thicker called nimbostratus

              3.  Altocumulus and Altostratus: mid level clouds

              3.  Fog: cloud that forms on or near ground


Air Masses and Fronts

1.  Air Mass

2.  Air Mass is a huge body of air that has similar temperature, humidity and air pressure.

       2.  There are 4 major air masses

          3.  Classified by the temperature and moisture content

4.  Tropical: warm

                 5.  Low air pressure

                 5.  form in the tropics

              4.  Polar: cold



Maritime (wet)

Continental (dry)

Tropical (Warm)

Maritime Tropical

Continental Tropical







   5.  Form north of the 50o N. Latitude or South of 50o S. Latitude

                 5.  High air pressure

              4.  Maritime: humid

                 5.  Forms over oceans

              4.  Continental: dry air

                 5.  forms over land

       2.  Air masses move 2 ways

              3.  Jet Stream

              3.  Prevailing westerlies

1.  Front

2.  Front: the boundary where air masses meet

2.  Four types of fronts

       3.  Cold Front: fast moving

              4.  Can have thunderstorms

              4.  heavy cold air pushes lighter warm air upwards


2. Warm Front: slow moving

3.  Precipitation

3.  Warm air replaces cold air by sliding over it


2.  Stationary Front: Cold air and warm air are at a standoff

3.  Precipitation can stall for days

3.  Neither warm nor cold air advances



2.  Occluded Front: Warm air is caught between 2 cool air fronts

              3.  Very complex

              3.  Precipitation

3.  Cold air is replacing cool air or vice versa at the surface, with warm air above


1.  Cyclone and Anticyclone

2.  Cyclone: an area of low pressure where wind spins counterclockwise

              3.  Area of precipitation

2.  Anticyclone:  an area of high pressure where wind spins clockwise

              3.  Clear dry weather


Storms: violent disturbance in the atmosphere

1.  Thunderstorms

2.  They form in a large cumulonimbus cloud

3. Thunderheads

2. Form when warm air is forced upward during a cold front

2.  Form on hot & humid afternoons

2.  Storm Movement

       3.  Heavy Rain

       3.  Strong updrafts within the cloud

2.  Lightening: charged particles travel between the cloud and earth



1.  Tornadoes

2.  Tornado is a rapidly whirling, funnel-shaped cloud that reaches the earth.

2.  Form most commonly in cumulonimbus clouds

1.  Warm moist air from the bottom of the cloud flows upward (LOW PRESSURE AREA IN CLOUD)

              2.  Warm air begins to rotate

              3.  Tornado forms as the funnel descends

       2.  Measuring Tornadoes

              3.  Fujita scale (F0-F5)

1.  Hurricanes

2.  Hurricane: tropical cyclone that has winds of 119 km/hr or higher

       2.  Formation of Hurricane

1. Warm moist air rises around the eye in spiraling bands

2.  Air flow outward near the top of the hurricane

3.  Cool dry air sinks in the eye

2.  Hurricanes form over warm ocean water

       3.  As low pressure

area or tropical


2.  Hurricanes move in the Atlantic by the Easterly Trade Winds


2.  Storm Surge: a dome of water that sweeps across the coast where the hurricane lands.

1.  Lake effect Snow: 

2.  Cool dry air mass moves over a body of water and picks up water vapor 

2.  Snow falls after the water vapor condenses again.

1.  Climate

2.  Factors affecting Temperature

              3.  Latitude (distance from equator)

                     4.  World Temperature Zones

       5.  Polar Zone: cold climates

       5.  Temperate zone:  warm or hot in summer, cool or cold in winter.

       5.  Tropical zone: warm climate



3.  Altitude (distance from sea level)

              3.  Distance from bodies of water

              3.  Ocean currents