1. Warm-up
What is weather?

2. Chapter 12
Meteorology

3. Causes of Weather
Meteorology – the study of atmospheric phenomena such as fog, clouds, snow, rain, and lighting
Weather- is the condition of the atmosphere at a certain time and place

4. Climate Climate is the long term weather for a particular area.
Usually averaged over 30 or more years.
Ex. The climate is hot and humid in Miami, but it is snowing in the picture to the right.

5. Air masses
Name
Description c
Continental
Dry m
Maritime
Wet E
Equatorial
Hot T
Tropical
Warm P
Polar
Cold A
Arctic
Very Cold
An air mass is a large body of air that takes on the characteristics of the area over which it forms.

6. Wind (review)
Wind- the movement of air caused by differences in air pressure
The greater the difference in pressure the faster wind moves

7. Global Wind Systems
Pressure belts - As warm air rises at the equator and moves towards the poles, it cools
As it cools, some of the air sinks around 30 degrees north and south of the equator
At the poles, cold air sinks and moves towards the equator

8. Global Wind Systems
Polar Easterlies- winds that blow from east to west between degrees latitude in both hemispheres.
Westerlies- The wind belt found between latitude in both hemispheres
Trade winds- Winds that blow northeast from 30 north latitude to the equator and that blow southeast from 30 degrees south latitude to the equator

9. Global Wind Systems
The combination of pressure belts and the Coriolis effect are the cause of Global winds.
Coriolis effect- deflection of particles to the right in the northern hemisphere and to the left in the southern hemisphere due to Earth’s rotation
Doldrums- Located along the equator where no winds blow, this creates slow rising air with very little pressure.
Horse Latitudes- weak winds that occur at 30 N and 30 S latitudes

10. Jet streams- Narrow belts of high speed winds that blow in the upper troposphere and lower stratosphere.
They can reach speeds of up to 400 km/h

11. Fronts
Front- An area in which two air-masses meet

12. Fronts
Cold Front- occur when a cold air mass runs into a warm air mass, forcing the warm mass to rise

13. Fronts
Warm Front- When warm masses run into cold masses and slowly displaces it

14. Fronts
Stationary Front- Two air masses meet and neither advances; air masses “stall”
Light wind and precipitation
Occluded Front – Cold air mass moves so rapidly that it overtakes a warm front
Strong winds, heavy precipitation

15. Pressure Systems
High Pressure Systems - Air sinks, then hits the Earth’s surface and spreads out.
Wind blows away from high pressure.
Clockwise in N. Hemisphere
Associated with fair weather

16. Pressure Systems Low Pressure System - Air rises, must be replaced.
Wind blows toward center of low pressure
Counter-Clockwise in N. Hemisphere
Associated with clouds and precipitation

17. Pressure Systems
Cyclone- an area in the atmosphere that has lower pressure than the surrounding areas that spiral towards the center
Anticyclone- the rotation of air around a high pressure center opposite to Earth’s rotation

18. Pressure Systems

19. Pressure Systems

20. Weather Instruments
Barometer- an instrument used to measure atmospheric air pressure.
Thermometer- measures temperature by using a liquid that moves up and down due to temperature differences.
Anemometer- an instrument used to measure wind speed.
Windsock- an instrument to measure wind direction

21. Weather Maps
Station Model

22. Weather Maps
Isobars- lines that connect equal points of equal pressure
Lines that are close = STRONG WINDS
Lines that are far apart = LIGHT WINDS