Today – Friday, 1/20/12  Attendance  Calendar  Review Weather  Lab # 26 Isoline Review

Weather Hey, is this cool or what?

Weather – the short term condition of the atmosphere

Meteorologist – scientist who studies the weather

A. Temperature – the amount of heat energy

The angle of the sun influences the temperature.

It is colder at night where there are no clouds.

Rotation – spinning on an axis

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

Temperature is measured with a thermometer.

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

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

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

Fair Weather – blue skies, less humid

Stormy Weather

High air pressure gradients make high winds.

C. Water Vapor – water in the form of a gas.  mini movie on phases of water - brain pop mini movie on phases of water - brain pop mini movie on phases of water - brain pop

Humidity – the amount of water vapor in the air. Humidity – the amount of water vapor in the air.  humidity brainpop humidity brainpop humidity brainpop

Sling Psychrometer - used to measure relative humidity

Relative Humidity Chart

Dew – drops of water that form on substances when the air gets too cold to hold water vapor.

Dew Point Chart

D. Air Movements  Why does air circulate (move) around in the atmosphere?

D. Air Movements Less dense (warmer) air rises Less dense (warmer) air rises More dense (cooler) air sinks More dense (cooler) air sinks

D. Air Movements  Some Definitions: Air currents: are vertical movements of air Air currents: are vertical movements of air Wind: horizontal movement of air Wind: 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 Movements Wind Vane – is a pointer that shows direction Anemometer – an instrument that measures wind speed.

E. Atmospheric Transparency  All the gases in our atmosphere are transparent (see through).  There are many substances that become suspended in the atmosphere that are not transparent (dust, ash, smoke, salt, droplets of liquid called aerosols)

E. Atmospheric Transparency  Visibility is the horizontal distance through which the eye can distinguish objects in miles.

III. Weather Stations  Know how to read weather stations.  Cloud cover is the fraction of the sky that is blocked by the clouds.

IV. Relationships  A. Air Temperature and Pressure As temperature increases, the pressure decreases As temperature increases, the pressure decreases When the temperature increases, the molecules move faster, spread out and become less dense.When the temperature increases, the molecules move faster, spread out and become less dense. As temperature decreases, the air pressure increases. As temperature decreases, the air pressure increases. Colder, slower, closer, more dense, more pressureColder, slower, closer, more dense, more pressure

IV. Relationships  A. Air temperature and pressure As P increases, T increases As P increases, T increases Move closer, more friction, more heatMove closer, more friction, more heat As P decreases, T decreases As P decreases, T decreases Move away, less friction, less heatMove away, less friction, less heat

IV. Relationships BBBB. Air pressure and humidity Water Vapor is much lighter than the other gases in the atmosphere. So if the amount of water vapor increases, the other heavier molecules are pushed out. The higher the humidity, the ___ the air pressure. The lower the humidity, the ___ the air pressure.

 C. Air Temperature and humidity If the temperature increases, the relative humidity will decrease. If the temperature increases, the relative humidity will decrease. Warmer air has the capacity to hold more, % decreasesWarmer air has the capacity to hold more, % decreases If the temperature decreases, the relative humidity increases. If the temperature decreases, the relative humidity increases. Cooler air has holds less water vapor, % increases.Cooler air has holds less water vapor, % increases.

IV. Relationships  D. Air pressure and wind Winds blow from regions of HIGH air pressure to regions of LOW air pressure. Winds blow from regions of HIGH air pressure to regions of LOW air pressure. HL

IV. Relationships  Winds curve to the right in the Northern 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 BREEZE

IV. Relationships  E. Global Winds/Planetary Winds

E. Cloud Formation  Clouds and precipitation are formed when air is cooled below its dew point and water vapor condenses into tiny water droplets or ice crystals. Condensation means changing phases from a gas to a liquid. Condensation means changing phases from a gas to a liquid.  Precipitation removes dust/dirt and many pollutants from the atmosphere.

E. Cloud Formation  Sublimation is the change of phase from a gas directly to a solid  Fog is a cloud whose base is at ground level. It forms when moist air at the ground level is cooled below its dew point.

More on Clouds  brainpop clouds brainpop clouds brainpop clouds