Bell Ringer 2/21/17 • Create a circle map on what you know about WEATHER
Air Pressure & Wind • Air Pressure & Wind 2/21/2017
Air pressure - the pressure exerted by the weight of air above • Exerted in all directions (up, down, and sideways) • Air pressure doesn’t just push down on an object, it pushes all aroundthe object (High or low?)
Barometer: device used for measuring air pressure • Unit: • millibars (mb) • inches of mercury • Torricelli: invented the mercury barometer in 1643 • https://www.youtube.com/watch?v=GRxglLS1YWI
The unequal heating of earth’s surface generates pressure differences • Solar radiation is the ultimate energy source for wind
Isobars • lines on a map that connect places of equal air pressure • A pressure gradient • The spacing of isobars shows the amount of pressure change over a given time
Closely spaced isobars: indicatea steep pressure gradient and high winds. • Widely spaced isobars: indicate a weak pressure gradient and light winds.
Wind is a result of horizontaldifferences in air pressure • Air flows from areas of high pressure to areas of lowerpressure.
Jet streams are fast-moving rivers of air • Speed: 120 and 240 kilometers per hour • Direction: West-to-east direction. • https://www.youtube.com/watch?v=WAve9PlK4Gg • https://www.youtube.com/watch?v=CgMWwx7Cll4 https://www.youtube.com/watch?v=huweohIh_Bw
Direction • Labeled by the direction from which they blow • Ex: winds blowing from the Southeast. • Tool: Wind Vane
Anemometer • Measures how fast wind is blowing
Air Masses & Fronts • Air Masses & Fronts 2/22
Probing Questions • Refer back to heating of land and water activity • Now lets look at heating of land and water on a global scale! (continental and maritime) • Go back to solar radiation. Warmer at the equator. (Tropical and Polar) at equator and poles.
Air Mass • An air mass is a big body of air that is characterized by similar temps and moisture • When an air mass moves out of the area it formed over, it keeps the same temp and moisture conditions • As it moves, the characteristics of an air mass change and so does the weather in the area it moves over
Classifying Air Masses • Air masses are classified by temperature and surface area over which they form
Weather in North America is influenced by continental polar and maritime tropical air masses
Probing QuestionsProbe to get to that air masses move (wind) and the space between two air masses is the front.
Fronts • When two air masses meet • boundary separating the two air masses.
Warm Front • A warm front – warm air moves into an area formerly covered by cooler air • Warm air glides up over a cold, dense air mass • Weather Conditions: Light to moderate rain
Cold Front Cold air mass moves into an area occupied by warmer air. Weather Conditions: Thunderstorms
Stationary and Occluded Fronts • stationary front: The surface position of the front does not move (steady rain for days) • occluded front: when an active cold front overtakes a warm front
Tornadoes & Thunderstorms • Tornadoes & Thunderstorms 2/23/2017
Severe Storms -Thunderstorms -Tornadoes -Hurricanes
Thunderstorms -Is a storm that generates thunder and lightning -Frequently produces gusty winds, heavy rain, and hail Associated with cumulonimbus clouds
Lightning: results from the build up and discharge of electric energy between positively (ground) and negatively (clouds) charged area -Thunder: the sound of rapidly expanding gases usually associated with lightning https://www.youtube.com/watch?v=G7GbOFlFODE https://www.youtube.com/watch?v=jM8h60S1GsM
Occurrence and Development • Occurrence • At any given time, there are an estimated 2000 thunderstorms in progress on Earth • Mostly in the tropics • Development • Thunderstorms form when warm, humid air rises in an unstable environment • 3 Stages
3 Stages • Cumulus: build up of clouds and moisture • Mature: Heavy rainfall, most active time • Dissipating: light rain, storm is calming down
Tornadoes • Tornadoes - violent low pressure windstorms that take the form of a rotating column of air (vortex). • The vortex extends downward from a cumulonimbus cloud producingrain and hail • Move counterclockwise https://www.youtube.com/watch?v=oQPBjQHG8gc https://www.youtube.com/watch?v=V-Xbj0aEkRQ
Occurrence, Development, and Intensity of Tornadoes • Occurrence • 770 occur each year • Tornado Season • April to June • Associated with severe thunderstorms • Intensity • Fujita Tornado scale • Based on the amount of damage
Tornado Warnings vs. Watches • Watches : Possibility of a tornado to be developed in the area • Warning: Tornado has been seen by people or indicated by radar
Hurricanes 2/24/2017 • HURRICANES
Hurricanes • Whirling tropical cyclones (low pressure system) producing winds of at least 119 km per hour (73 mph) • US – Hurricanes • Pacific – Typhoons • Indian Ocean – Cyclones • Most powerful storm on Earth
Occurrence and Development of Hurricanes Occurrence • Form between 5 and 20 degrees north and south latitude • Season: June 1 to November 30th Development of Hurricanes • Hurricane develop most often in the late summer when water temperatures are warm enough to provide the necessary heat and moisture to the air • Low Pressure: Spins counterclockwise
Parts of a Hurricane Eye: Center of storm, warmest part, winds cease, rain ceases Eye wall: Strongest winds and rain Spiral Rain Bands: extend out from the eye wall https://www.youtube.com/watch?v=Wk_FVXVnE2I
Hurricane Intensity • Storm Surge: is a dome of water that sweep across the coast caused by the hurricane’s winds • Categorized on the Saffir-Simpson Scale (based on wind speed)
Hurricane Warning and Watches • Hurricane Watch: could see hurricane related hazards within 48 hours • Hurricane Warning: Could see hurricane winds within 36 hours