1. Meteorology 12.1 – The Causes of Weather
Chapter 12
Meteorology
12.1 – The Causes of Weather

2. Types of atmospheric “meteors”
Meteor – ancient Greek – meaning “high in the air”
Clouds
Raindrops
Snowflakes
Fog
Dust
Rainbows

3. Various phenomena
Hydrometeors –primary types are cloud droplets and forms of precipitation
Lithometeor – smoke, haze, dust, or condensation nuclei
Electrometeors – thunder and lightning

4. CONTRAST Weather and 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

5. Compare major masses impacting North America
TYPE of Air Mass
Source 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

6. Section 12.2 Weather Systems
Meteorology
Section 12.2
Weather Systems

7. 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

8. 3 basic zones/wind systems in each hemisphere
Global Wind Systems
3 basic zones/wind systems in each hemisphere
Trade winds –
occur near 300 north & south latitude
Air sinks, warms, and moves towards the equator
Moves in a westerly direction (east to west)
Prevailing Westerlies –
occur between 30° and 60° north and south latitude
Circulation pattern, opposite that of the trade winds
Moves towards the poles
Moves in an easterly direction ( west to east)
Polar Easterlies –
Occur between 60° latitude and the poles
Similar to trade winds

9. Jet Streams Jet Streams affect the movement of air masses.
Resemble jets of water
Narrow bands of fast, high-altitude, westerly winds
speed 185 km/hr

10. Types of fronts Types 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

11. 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

12. -Winds move counter clockwise
Pressure Systems
Low pressure
High Pressure -
-Rising air
-Winds move counter clockwise
-Stormy weather
- Sinking air
- Winds move clockwise
- Fair weather
Air
moves in
circular motion

13. Gathering Weather Data
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14. Section 12.3 Gathering Weather Data
Chapter 12 Meteorology
Section 12.3
Gathering Weather Data

15. Meteorologist (weather man)
Measure atmospheric variables to make accurate weather forecasts.
temperature,
air pressure,
wind, and
relative humidity

16. Surface Weather Data Instruments
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

17. The End