Today – Friday, 1/20/12Today – Friday, 1/20/12 AttendanceAttendance CalendarCalendar Review WeatherReview Weather

Lab # 26 Lab # 26 Isoline Isoline ReviewReview

WeatherWeather

Hey, is this cool or what?Hey, is this cool or what?

Weather – the short term Weather – the short term condition of the atmospherecondition of the atmosphere

Meteorologist – scientist who Meteorologist – scientist who studies the weatherstudies the weather

A. Temperature – the amount of A. Temperature – the amount of heat energyheat energy

The angle of the sun influences The angle of the sun influences the temperature.the temperature.

It is colder at night where there It is colder at night where there are no clouds.are no clouds.

Rotation – spinning on an axisRotation – spinning on an axis

Seasons occur because 1) the Seasons occur because 1) the Earth is tilted 2) the Earth Earth is tilted 2) the Earth revolves around the sun.revolves around the sun.

Temperature Temperature is measured is measured

with a with a thermometer.thermometer.

B. Air has weight that presses B. Air has weight that presses down on thedown on the

earth. earth.

Aneroid Barometers – measure Aneroid Barometers – measure air pressure by measuring how air pressure by measuring how much air is pushing in on the much air is pushing in on the

can.can.

Mercury Barometers – measure Mercury Barometers – measure the force of air pressing on liquid the force of air pressing on liquid mercury.mercury.

Fair Weather – blue skies, less Fair Weather – blue skies, less humidhumid

Stormy WeatherStormy Weather

High air pressure gradients High air pressure gradients make high winds.make high winds.

C. Water Vapor – water in the C. Water Vapor – water in the form of a gas.form of a gas.

mini movie on phases of water - brain popmini movie on phases of water - brain pop

Humidity – the amount of water Humidity – the amount of water vapor in the air.vapor in the air.

humidity brainpophumidity brainpop

Sling Psychrometer - used to Sling Psychrometer - used to measure relative humiditymeasure relative humidity

Relative Humidity ChartRelative Humidity Chart

Dew – drops of water that form Dew – drops of water that form on substances when the air gets on substances when the air gets

too cold to hold water vapor.too cold to hold water vapor.

Dew Point ChartDew Point Chart

D. Air MovementsD. Air Movements

Why does air circulate (move) around in Why does air circulate (move) around in the atmosphere? the atmosphere?

D. Air MovementsD. Air Movements

Less dense (warmer) air risesLess dense (warmer) air rises

More dense (cooler) air sinksMore dense (cooler) air sinks

D. Air MovementsD. Air Movements

Some Definitions:Some Definitions: Air currentsAir currents: are vertical movements of air : are vertical movements of air

WindWind: horizontal movement of air : horizontal movement of air • Described in both direction and speedDescribed in both direction and speed• Named for the direction from which it blowsNamed for the direction from which it blows

D. Air MovementsD. Air Movements

Wind VaneWind Vane – is a – is a pointer that shows pointer that shows directiondirection

AnemometerAnemometer – an – an instrument that instrument that measures wind speed.measures wind speed.

E. Atmospheric TransparencyE. Atmospheric Transparency

All the gases in our atmosphere are All the gases in our atmosphere are transparent (see through).transparent (see through).

There are many substances that become There are many substances that become suspended in the atmosphere that are not suspended in the atmosphere that are not transparent (dust, ash, smoke, salt, transparent (dust, ash, smoke, salt, droplets of liquid called aerosols)droplets of liquid called aerosols)

E. Atmospheric TransparencyE. Atmospheric Transparency

VisibilityVisibility is the horizontal distance through is the horizontal distance through which the eye can distinguish objects in which the eye can distinguish objects in miles.miles.

III. Weather StationsIII. Weather Stations

Know how to read Know how to read weather stations.weather stations.

Cloud coverCloud cover is the is the fraction of the sky that fraction of the sky that is blocked by the is blocked by the clouds.clouds.

IV. RelationshipsIV. Relationships

A. A. Air Temperature and PressureAir Temperature and Pressure As temperature increases, the pressure As temperature increases, the pressure

decreasesdecreases• When the temperature increases, the molecules When the temperature increases, the molecules

move faster, spread out and become less dense.move faster, spread out and become less dense. As temperature decreases, the air pressure As temperature decreases, the air pressure

increases.increases.• Colder, slower, closer, more dense, more pressureColder, slower, closer, more dense, more pressure

IV. RelationshipsIV. Relationships

A. A. Air temperature and pressureAir temperature and pressure As P increases, T increasesAs P increases, T increases

• Move closer, more friction, more heatMove closer, more friction, more heat As P decreases, T decreasesAs P decreases, T decreases

• Move away, less friction, less heatMove away, less friction, less heat

IV. RelationshipsIV. Relationships

B. B. Air pressure and humidityAir pressure and humidity Water Vapor is much lighter than the other Water Vapor is much lighter than the other

gases in the atmosphere.gases in the atmosphere.• So if the amount of water vapor increases, the So if the amount of water vapor increases, the

other heavier molecules are pushed out.other heavier molecules are pushed out. The higher the humidity, the ___ the air The higher the humidity, the ___ the air

pressure.pressure. The lower the humidity, the ___ the air The lower the humidity, the ___ the air

pressure.pressure.

IV. RelationshipsIV. Relationships

C. C. Air Temperature and humidityAir Temperature and humidity If the temperature increases, the relative If the temperature increases, the relative

humidity will decrease.humidity will decrease.• Warmer air has the capacity to hold more, % Warmer air has the capacity to hold more, %

decreasesdecreases If the temperature decreases, the relative If the temperature decreases, the relative

humidity increases.humidity increases.• Cooler air has holds less water vapor, % Cooler air has holds less water vapor, %

increases.increases.

IV. RelationshipsIV. Relationships

D. D. Air pressure and windAir pressure and wind Winds blow from regions of HIGH air pressure Winds blow from regions of HIGH air pressure

to regions of LOW air pressure.to regions of LOW air pressure.

HH LL

IV. RelationshipsIV. Relationships

Winds curve to the right in the Northern Winds curve to the right in the Northern Hemisphere because of the Coriolis Effect.Hemisphere because of the Coriolis Effect. (Curve to the left in the Southern Hemisphere)(Curve to the left in the Southern Hemisphere)

Get it? SEA BREEZEGet it? SEA BREEZE

IV. RelationshipsIV. Relationships

E. Global Winds/Planetary WindsE. Global Winds/Planetary Winds

E. Cloud FormationE. Cloud Formation

Clouds and precipitation are formed Clouds and precipitation are formed when air is cooled below its dew point when air is cooled below its dew point and water vapor condenses into tiny and water vapor condenses into tiny water droplets or ice crystals.water droplets or ice crystals. CondensationCondensation means changing phases from means changing phases from

a gas to a liquid.a gas to a liquid.

Precipitation removes dust/dirt and many Precipitation removes dust/dirt and many pollutants from the atmosphere.pollutants from the atmosphere.

E. Cloud FormationE. Cloud Formation

SublimationSublimation is the change of phase from a is the change of phase from a gas directly to a solidgas directly to a solid

FogFog is a cloud whose base is at ground is a cloud whose base is at ground level. It forms when moist air at the level. It forms when moist air at the ground level is cooled below its dew point.ground level is cooled below its dew point.

More on CloudsMore on Clouds

brainpop cloudsbrainpop clouds