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Chapter 12. Meteorology 12.1 – The Causes of Weather. Types of atmospheric “meteors”. Meteor – ancient Greek – meaning “high in the air” Clouds Raindrops Snowflakes Fog Dust Rainbows. Various phenomena. Hydrometeors –primary types are cloud droplets and forms of precipitation - PowerPoint PPT Presentation
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Chapter 12Meteorology
12.1 – The Causes of Weather
Meteor – ancient Greek – meaning “high in the air”1. Clouds2. Raindrops3. Snowflakes4. Fog5. Dust6. Rainbows
Types of atmospheric “meteors”
Hydrometeors –primary types are cloud droplets and forms of precipitation
Lithometeor – smoke, haze, dust, or condensation nuclei
Electrometeors – thunder and lightning
Various phenomena
WEATHER CLIMATE
DESCRIPTION Current state of atmosphere Average weather
TERM, MEASURE OF VARIATIONS
Short term variations (minutes, hrs, days, weeks, months, years)
Over a long period, 30 years or more
CONTRAST Weather and Climate
TYPE of Air MassSource of Air
Mass
Weather Associated with
Air Mass
Continental Tropical (cT)
Desert Southwest & Mexico
Hot, dry summers
Maritime Tropical(mT)
Caribbean Sea Gulf of Mexico
Hot & humid summers
Continental Polar (cP)
Interior of Canada and Alaska
Very cold, frigid winter when nights are long
Maritime Polar (mP)
North Atlantic North Pacific
Heavy rains in winter on West Coast
Artic (A) Siberia & Arctic Basin
No solar radiation. Very cold/bitter cold & dry
Compare major masses impacting North America
MeteorologySection 12.2
Weather Systems
Why are most tropical rain forests located near the equator?
Equator- the trade winds from both hemispheres meet
ITCZ (Inter tropical convergence zone)
The rising air over a large area creates clouds and abundant precipitation
Global Wind Systems3 basic zones/wind systems in each hemisphere
1. Trade winds – occur near 300 north & south latitudeAir sinks, warms, and moves towards the equatorMoves in a westerly direction (east to west)
2. Prevailing Westerlies – occur between 30° and 60° north and south latitudeCirculation pattern, opposite that of the trade windsMoves towards the poles Moves in an easterly direction ( west to east)
3. Polar Easterlies –Occur between 60° latitude and the polesSimilar to trade winds
Jet StreamsJet Streams affect the movement of air masses.Resemble jets of waterNarrow bands of fast, high-altitude, westerly winds
speed 185 km/hr
Types of frontsTypes of front
Map symbol
Description of air movement
Associated weather
COLD FRONT
Forces warm air up along a steep front
Clouds, showers, some thunderstorms
WARM FRONT
Warm air displaces cold air, warm air encounters less friction w/ ground
Extensive cloudiness & precipitation
STATIONARY FRONT
Two air masses meet. Neither advances to the others territory
Similar to warm front
OCCLUDED FRONT
Moves rapidly that it overtakes a warm front
precipitation
Earth’s rotation affects air movement
Rising & sinking air, combined with Coriolis effect result in formation of low & high pressure systems.Air at Earth’s surface spreads away from the center
Pressure Systems
-
-Rising air-Winds move
counter clockwise -Stormy weather
- Sinking air- Winds move clockwise- Fair weather
Air moves
in circula
r motion
High PressureLow pressure
Gathering Weather DataShow videohttp://
app.discoveryeducation.com/player/view/assetGuid/25B0B2A7-D01A-43D3-90BC-BC94FC1258F3
Chapter 12Meteorology
Section 12.3Gathering Weather Data
Meteorologist (weather man)Measure atmospheric variables to make accurate weather forecasts.
1. temperature, 2. air pressure, 3. wind, and 4. relative humidity
Surface Weather Data InstrumentsInstrument
What does it measure?
How does it work?
Thermometer Temperature Mercury / alcohol expand with heat
Barometer Air pressure
Changes in pressure measured by changes in height of column of mercury
Anemometer Wind speed & direction
Rotates as the wind blows
Hygrometer Relative humidity Wet and dry bulb thermometers
Ceilometer Height of cloud layers Data collected by ASOS
Radiosonde – balloon-borne pkg.
Upper –level date (temp air pressure, humidity
Radio signal back to ground station
The End