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Weather
Vocabulary and Notes
Vocabulary
1. Conduction – Direct transfer of heat from one substance to another substance that it is touching.
2. Convection – Transfer of heat by movement of fluid (gas/liquid). Ex. Cold air sinks while warm air
rises. This movement causes winds to blow.
3. Radiation – Direct transfer of energy by electromagnetic waves.
4. Wind – Horizontal movement of air from an area of high pressure to an area of low pressure.
5. Coriolis effect – The way Earth’s rotation makes winds curve.
6. Jet stream – Bands of high speed winds about 10 km above Earth’s surface.
7. Ocean currents – Streams of water within the oceans that move in regular patterns.
8. Humidity – A measure of the amount of water vapor in the air.
9. Cumulus Clouds – Clouds that form less than 2 km above the ground and look like fluffy rounded
piles of cotton (usually indicate fair weather).
10. Cirrus Clouds – Clouds that form at high levels (about 6 km above ground), are wispy or feathery,
and are made mostly of ice crystals.
11. Stratus Clouds – Clouds that form in flat layers and usually cover most or all of the sky. May produce
drizzle, rain, or snow.
12. Nimbus – prefix or suffix that comes from the Latin word meaning “rain”.
13. Air mass – A huge body of air that has similar temperature, pressure and humidity throughout.
14. Maritime polar – Air mass that forms over the icy cold North Pacific and North Atlantic oceans which
brings cool, humid air to the West Coast of the United States.
15. Continental polar – Air mass that forms over central and northern Canada and Alaska which brings
cold air to the central and eastern United States.
16. Maritime tropical – Air mass that forms over oceans near the tropics which brings warm, humid air
to the United States.
17. Continental tropical – Hot, dry air mass that forms mostly in summer over dry areas of the
Southwest United States and northern Mexico.
18. Front – The area where air masses meet and do not mix. The collision often causes storms and
changeable weather.
19. Warm Front – A warm air mass moves over a cold air mass.
20. Cold Front - A cold air mass moves beneath a warm air mass.
21. Stationary Front – Neither a cold air mass nor a warm air mass has enough force to move the other,
so the front does not move.
22. Occluded Front – Warm air is caught between two cooler air masses and is pushed upward.
23. Isobars – Lines on the weather map joining places that have the same air pressure.
24. Isotherms – Lines on the weather map joining places that have the same temperatures.
25. Meteorologist – Scientist who studies the causes of weather and tries to predict it.
Notes
1. Heat moves (transfers) in three ways – conduction, convection and radiation
2. Heat transfer by conduction, convection and radiation causes temperature to change, winds to blow,
and rain to fall.
3. All winds are caused by differences in air pressure, which are the result of unequal heating of Earth’s
surface. Cold air has higher air pressure and warm air has lower air pressure.
4. The movement of air between the equator and the poles produces global winds.
5. If Earth did not rotate, global winds would blow in a straight line from the poles to the equator.
Because Earth is rotating, global winds do not follow a straight path. The way Earth’s rotation makes
winds curve is called the Coriolis effect.
6. The major global wind belts are the trade winds, the polar easterlies, and the prevailing westerlies.
7. Near the equator, the trade winds blow from the east to the west (easterly winds).
8. At the poles, the polar easterlies blow from east to the west (easterly winds).
9. In between the trade winds and the polar easterlies, the prevailing westerlies blow from west to east
(westerly winds). The prevailing westerlies are the major wind belts in the continental United States.
10. The name of the wind tells the direction the wind is coming FROM. For example, a prevailing
westerly blows from west to east.
11. The jet streams blow from west to east at speeds of 200 to 400 kilometers per hour. As they travel
around Earth, they wander north and south along a wavy path.
12. Clouds form when water vapor in the air becomes liquid water or ice crystals. The water vapor
condenses onto tiny particles in the air, such as salt crystals, dust, or smoke.
13. Meteorologists classify clouds into three main types: cumulus, stratus, and cirrus.
14. Four major types of air masses influence the weather in North America: Maritime Tropical,
Continental Tropical, Maritime Polar and Continental Polar.
15. When air masses collide, they form four types of fronts: cold fronts, warm fronts, stationary fronts
and occluded fronts.
16. Cold fronts move quickly, so they can cause abrupt weather changes, including violent thunderstorms.
After a cold front passes through an area, cool, dry air moves in, often bringing clear skies and cooler
temperatures.
17. Warm fronts move more slowly than cold fronts, so the weather may be rainy or foggy for several
days. After a warm front passes through an area, the weather is likely to be warmer and more humid.
18. Stationary fronts may bring many days of clouds and precipitation.
19. At an occluded front the temperature near the ground becomes cooler. The rising warm air may
cause the weather to turn cloudy and rainy or snowy.
20. Meteorologists use maps, charts and computers to analyze weather data and to prepare weather
forecasts.
21. Technological improvements in gathering weather data and using computers have improved the
accuracy of weather forecasts.
22. Isotherms may be labeled with the temperature in degrees Fahrenheit, degrees Celsius or both.
23. The numbers on the isobars are pressure readings. Air pressure readings may be given in inches of
mercury or in millibars or both.