 What is weather? State of the atmosphere at a specific time and place. Describes conditions such as: air pressure, wind, temp. and amount of moisture in the air (variables of weather)

SUN’S HEAT EARTH’S AIR & WATER  Sun provides almost all of Earth’s energy.  Sun causes evaporation  Which forms clouds  Which falls to Earth as rain or snow.  Repeat :-)

AIR MOLECULESTEMPERATURE  Always moving  Randomly – even when there is no wind.  Def.: measure of the average amount of motion of molecules (kinetic energy)  Temp – high – molecules move fast – feels warm  Temp – low- move less fast – feels cool

DEFINITIONAIR  Air moving in a specific direction  Measured w/  Weather vanes  Weather socks  Anemometer  “a nuh MAH muh tur” Warm – low atmospheric pressure Cool – high atmospheric pressure (denser - sinks) *****Air moves from regions of high to low pressure (cool to warm)

 Def: the force a column of air applies on the air or a surface below it.  Instrument used to measure air pressure = BAROMETER  Label = millibars (mb)

 Def. : amount of water vapor present in the air  Warmer temps – move too quickly to come together  Cooler temps – move slower so water vapor molecules stick together (condense!!!) Condensation = air is saturated

 DEF: measure of the amount of water vapor present in the air COMPARED to the maximum amount of water vapor the air could contain at that temperature. .

 Definition: TEMPERATURE at which air is saturated and condenses *** changes w/ the amount of water vapor in air.

 MiniLab  Use Fig 3 ~ GRAPH  Reading the graph  How much water vapor is in the air at 15 degrees C?  What temperature has 5 g/m 3 water vapor?

 Stratus  Flat white and layered.  Form at low altitudes (up to 2000 m)  Associated w/ fair weather or rain, snow  Cumulus  Puffy, white w/ flat bases ~ piled up.  Sometimes tower to great heights (2000 to 6000 m)  Cirrus  Thin, white, feathery ~ wispy.  Made of ice crystals  High – above 6000 m

 Different classifications of Clouds Different classifications of Clouds  Prefixes:  Cirro – describes high clouds  Alto – describes middle  Strato – low NIMBUS means “dark rain cloud” **associated w/ precipitation

 Stratus cloud near ground!!  Air is cooled to dew point!!  Reduces visibility.

 Def: water in liquid or solid form falling from atmosphere.

 1. Rain: water vapor forms raindrops when air is WARM.  2. Snow: water vapor forms snowflakes when air is COLD.  3. Sleet: Starts as rain but air near ground is cold so rain freezes. (Made up of small ice pellets.)  4. HAIL: Pellets of ice BUT they form INSIDE the cloud.

 Sept. 22, 2010 Mrs. Edelen’s house!

 Compare Contrast

 Role of WATER VAPOR in atmosphere  Relative HUMIDITY: tells whether day is dry or precip. will happen.  Air Temp of Atmosphere: determines what type of precip. will happen  Study Clouds: know what is coming  Understand the water cycle.

 There are …. SIX  Wind ~ direction and speed  Temperature  Air pressure  Humidity  Cloud coverage  Precipitation

 READ SECTION 1 (if you haven’t already)  Assignment:  P. 456 (1-10)