1. THE CAUSES OF WEATHER
Section 12.1

2. Meteorology Is the study of atmospheric phenomena
Root word (Greek – meteoros) means high in the air.
A meteor is anything that is high in the sky
DIFFERENT TYPES OF METEORS
hydrometeors – cloud droplets and precipitation
lithometeors – smoke, haze, dust, other particles
electrometeors – thunder and lightening

3. Weather versus climate
Weather- Short-term variations in atmospheric phenomena that interact and affect the environment and life on Earth.
Climate- The long term average of variations in weather for a particular area.
Know the difference “Beautiful climate we’re having today Bob.” WRONG

4. Heating Earth’s Surface
Sunlight, a part of solar radiation, is always heating some portion of the Earth’s surface.
The amount of thermal energy that the Earth receives is the same amount that the Earth radiates back to space.
Imbalanced heating
The Earth’s axis of rotation is tilted.
The number of hours of daylight and amount of solar radiation is greater in some places.
The Earth is a sphere

6. Thermal energy redistribution
The constant movement of air and water among the Earth’s surface help areas around Earth to maintain about the same average temperature over time.
This movement redistributes thermal energy around the world.
Weather is part of the ongoing redistribution of Earths thermal energy.

7. Air Masses
Air mass- Large volume of air that has the same characteristics (humidity and temperature) of the area over which it forms.
Source region- The area over which the air mass forms.
Modification – when an air mass exchanges thermal energy and/or moisture with the surface over which it travels

8. Types of air masses Maritime (over water) or Continental (over land)
Tropical air masses - form over warm bodies of water (Gulf of Mexico, Caribbean sea…) or warm land masses (southwest United States, Mexico)
Summer time brings hot, humid weather to two thirds of North America.
Polar air masses - form over cold bodies of water (North Atlantic, North Pacific) or cold land masses (Interior of Canada and Alaska).
The air masses that affect weather in the United States.
Arctic (extremely cold/frigid)
Continental polar
Continental tropical
Maritime polar
Maritime tropical

9. Weather Systems Section 12.2

10. Coriolis Effect Objects move in apparent curved path
Northern Hemisphere – curve to right
Southern Hemisphere – curve to left
This creates global wind systems; help to equalize thermal energy on earth

11. Coriolis Effect Animation

12. Coriolis Effect Activity
Find a partner.
One person cuts out a large circle from a piece of white paper.
One person rotates the circle while the other person attempts to draw a straight line from the center outward.
What is happening?

13. 3 basic wind systems Polar easterlies Prevailing westerlies
Trade winds

15. Polar Easterlies Location: Dense polar air sinks
60°N latitude and North Pole
60°S and South Pole
Dense polar air sinks
Earth spins, air deflected as it moves away from poles
Cold, weak winds

16. Prevailing Westerlies
Location:
30°N - 60°N
30°S - 60°S
Originate from the WEST
Steady winds
Move much of weather across US and Canada

17. Trade Winds 30°N - 30°S Air sinks, warms, and moves toward equator
At equator: rises and moves back towards 30° N and 30° S

18. RECALL FROM CH. 11… Warmer air has _________ pressure than colder air.
HIGHER
What causes wind?
Movement of air from higher to lower pressure.

19. Jet Streams
Larger temperature gradient + Coriolis effect = strong westerly winds (jet stream)
Speed varies with temperature differences
Position varies with season
Located in area of strongest temperature differences

20. Partner activity
How might jet streams have an effect on the aviation industry?

21. Jet Streams & Weather Storms form along them
Large-scale weather systems are generated
Weather systems follow the path of jet streams

22. Fronts and Pressure Systems
Fill out Table

23. Gathering Weather Data Section 12.3

24. There are four different atmospheric conditions that meteorologists measure
These are:
Temperature
Air pressure
Wind speed
Relative humidity
The accuracy and amount of data available are two important factors when forecasting weather.

25. Temperature and Air Pressure
Thermometer - measures temperature using Fahrenheit or Celsius scale
Barometer - measures air pressure

26. Wind Speed and Relative Humidity
Anemometer - instrument that measures wind speed
Hygrometer - instrument that measures humidity

27. Automated Surface Observing System
A system that gathers data in a consistent manner in different locations
Provides essential weather data for:
Aviation
Weather forecasting
Weather related research

28. Data from the Upper Atmosphere
Surface weather data is important but is largely the result of changes that take place in the troposphere
Data must be gathered at high altitudes
Up to 30,000 meters
Radiosond - Instrument used for gathering upper atmosphere data
i.e. air temperature, air pressure, and humidity

29. Weather Observation Systems
Weather radar system detects specific locations of precipitation
Doppler weather radar
Doppler effect - change in pitch or frequency that occurs due to relative motion of a wave, (i.e. sound or light) as it comes toward or goes away from an observer
Weather Satellites orbit earth to observe weather
These satellites use infrared imagery to make observations at night
Visible light imagery - satellites that require visible light in order to help determine cloud coverage
Water-vapor imagery - shows moisture in the atmosphere and helps meteorologists monitor storm systems even when clouds aren’t present

30. High and Low Pressure Systems