Air Masses and Weather Maps Investigation 9, Part 2 Weather and Climate Air Masses and Weather Maps Investigation 9, Part 2 TG- p.303-304

Review Air Masses Air masses: Large thick bodies of air Uniform in temperature and humidity Have distinct boundaries Cover large areas of earth’s surface Reach top of the troposphere Names for the source region TG- P.305

Colliding Air Masses Cold air masses from the polar regions move south and east Air masses don’t stay in one place TG- P.305 Warm air masses from the tropics move north and east

Colliding Air Masses Air masses don’t stay in one place TG- P.305 Movement of air masses creates opportunity for air masses of different temperatures and humidity to collide

Meeting of Air Masses Remember the density bottles What is going on inside of the bottle? Denser liquid below the less-dense one TG- P.305

Meeting of Air Masses Imagine I reach north Grab a cP (continental polar) air mass Shrink it Jam it into the bottle TG- P.306 cP

Meeting of Air Masses Imagine What happens to the air masses? mT cP I reach south Grab a mT (maritime tropical) air mass Shrink it Jam it into the bottle with the cP one What happens to the air masses? Polar air sinks because it is denser Tropical Air lifts to the top because it is less dense mT TG- P.306 cP

Air Mass Model Gases and liquids have fluid movement The liquid in the bottle represents what would happen in real life with air masses TG- P.306

Fronts If air masses meet, a boundary forms Front A boundary between two air masses TG- P.306

Origin of “Fronts” Originated after World War 1 Norwegian meteorologists The zone where 2 opposing armies clash is called a battlefront The boundary - violent weather changes often occur TG- P.306

Naming Fronts Takes the name of the air mass that is moving faster and overtakes a slower air mass TG- P.306

Cold Fronts A boundary that forms when a cold air mass overtakes warm air mass Clouds form TG- P.306 Cold, dense air plows under warm, less dense air Warm, humid air rises and cools

Weather and Cold Fronts Effects from cold fronts happen quickly Clouds form, can grow into thunderstorms Rain or snow can fall Lightning and hail Drop in temperature Pressure increases TG- P.306 A cold front moves in Cold front symbol on weather map

Warm Front The boundary that forms when a warm air mass overtakes a cold air mass Can be hundreds of km long Warm air slides up over cold air at a gentle slope TG- P.306

Weather and Warm Front Effects happen over long period of time A warm front moves in Effects happen over long period of time Air pressure decreases Temperature rises at the surface Clouds thicken and lower (first wispy, cirrus clouds) then others (cumulostratus, altostratus, nimobostratus, stratus, possibly fog) Rain, snow, sleet or freezing rain begin to fall TG- P.307 Warm front symbol on weather map

Surface Observations Meteorologists receive weather observations from stations all over the United States and the world These are called surface observations TG- P.308

Surface Observations Surface Observations include: Temperature Humidity Air Pressure Wind Speed and Direction Cloud Cover and Type Precipitation Type and Amount TG- P.308

Look at Weather Symbols Use special codes or symbols to represent weather data on a map Typical weather symbol TG- P.308

Weather Symbol From which it is blowing Short barb = 5 knots TG- P.308-309 From which it is blowing Short barb = 5 knots Long barb = 10 knots

Surface Observations Programmed into a computer that plots the information on a map Used by meteorologist to make weather predictions TG- P.308

Practice Reading Weather Maps Open to page 57 of your lab book and see if you can read a weather map. TG- P.308 Resources Book- P.87-88 Student Lab Notebook -P.57

Response Sheet- Weather and Climate Homework: Page 59 of your lab book. TG- P.308 Student Lab Notebook -P.59