Wind and Weather Notes. 8 th Grade Science Mrs. Melka

Transcription

1 Wind and Weather Notes 8 th Grade Science Mrs. Melka

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3 Why is Wind Important? Part 1 Because wind systems determine major weather patterns on Earth. Wind also helps determine where planes and ships travel most efficiently.

4 How Wind Moves #1: Convection Uneven heating of Earth by the Sun causes some areas to be warmer than others Warm air rises = molecules are spread out; is less dense; has lower pressure Cold air sinks = molecules are closer together; is more dense; has higher pressure Cooler air displaces the warmer air causing convection currents (remember the lava lamp!)

5 How Wind Moves #2: Coriolis Effect The winds curve because of Earth s rotation on its axis Hot air near the equator rises & moves toward poles Cool air near the poles falls & moves toward equator Their paths are curved because of the Coriolis Effect Northern Hemisphere = curves right Southern Hemisphere = curves left

6 Global/Prevailing Winds The term horse latitudes supposedly originates from the days when Spanish sailing vessels transported horses to the West Indies. Ships would often become becalmed in mid-ocean in this latitude, thus severely prolonging the voyage; the resulting water shortages would make it necessary for crews to throw their horses overboard.

7 Global/Prevailing Winds Westerlies: Found between 30 o & 60 o north & south latitudes Blow from the west (from west to east) Move weather systems in the US from west to east Doldrums: Nearly windless, rainy zone found along equator Trade Winds: Air sinking near 30 o north & south latitudes Creates steady wind that blows from the east Called trade winds because early sailors used their dependability to establish trade routes

8 Global/Prevailing Winds Polar Easterlies: Found near poles Blow from the east (from east to west) Jet Streams: Narrow belts of strong winds in the upper atmosphere In US moves from west to east Planes = if flying eastward, pilots use jet stream to save time and fuel; if flying westward, pilots fly at different altitudes to avoid jet stream

9 Jet Streams: Global/Prevailing Winds

10 Weather: Weather Condition of atmosphere at specific time and place Occurs as result of Sun s heat energy and Earth s air and water interacting

11 Weather Weather Factors: Air Temperature Wind Humidity

12 Air Temperature: Weather Measure of average amount of motion of molecules Low Temperature = molecules move slower High Temperature = molecules move faster

13 Wind: Weather Wind is caused by air put into motion by the energy from the Sun. Warm air = less dense & lower pressure (RISES) Cold air = more dense & higher pressure (SINKS) Wind results because HIGH pressure air (cold air) moves toward LOW pressure air (warm air) and replaces it (the warm air moves up and cold air takes its place) Wind moves weather systems around Earth.

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15 Weather Interesting Wind Facts: The highest wind speed ever recorded on the surface of the Earth was 231 mph on April , atop Mt. Washington, New Hampshire. Dust in North Africa is kicked up by high winds and carried as high as 20,000 feet (6,100 meters), where it's caught up in the trade winds and carried across the ocean. Dust from China can make its way to North America, too.

16 Humidity: Weather Amount of water vapor present in air As temperature increases, the amount of water vapor it can hold increases Warm air = holds more water vapor Cool air = holds less water vapor

17 Weather Patterns Part 2 Air masses, pressure systems, and fronts cause weather to change

18 Air Masses = Weather Patterns Large bodies of air Its properties are similar to the part of Earth where it formed Air mass developed over land = dry Air mass developed over water = wet Air mass developed in tropics = warmer Air mass developed in poles = colder

19 Weather Patterns Air Masses

20 Weather Patterns Naming Air Masses: Continental = Forms Over Land (dry) Maritime = Forms Over Water (wet) Polar = Forms Over Polar Areas (cold) Tropical = Forms Over Tropical Areas (Warm)

21 Maritime Polar Weather Patterns Continental Polar Maritime Polar Maritime Tropical Continental Tropical Maritime Tropical

22 Pressure Systems = Weather Patterns Measured with barometer Low pressure system = [L = lousy weather] Areas of rising air (aka - warm air = less dense) Usually cloudy or bad weather Lows are usually associated with high winds, warm air, and atmospheric lifting. Because of this, lows normally produce clouds, precipitation, and other bad weather such as tropical storms and cyclones. High pressure system = [H = happy weather] Areas of sinking air (aka - cool air = more dense) Usually means good weather Highs are normally caused by a phenomenon called subsidence, meaning that as the air in the high cools it becomes denser and moves toward the ground. Pressure increases here because more air fills the space left from the low. Subsidence also evaporates most of the atmosphere's water vapor so high pressure systems are usually associated with clear skies and calm weather.

23 Barometer

24 Fronts = Weather Patterns A boundary between two air masses with different characteristics, such as density, moisture, or temperature At these boundaries you sometimes get cloudiness, precipitation or storms 3 types of fronts:»cold»warm»stationary

25 Fronts = Cold front Weather Patterns Cold air advances toward warm air Warm air is pushed up quickly by cold air If temperature difference is large, thunderstorms (even tornadoes) can form

26 Weather Patterns Fronts = Cold front symbol

27 Fronts = Warm front Weather Patterns Warm air advances toward cool air Warm air moves up & over cold front Can lead to long periods of precipitation

28 Weather Patterns Fronts = Warm front symbol

29 Weather Patterns Fronts = Stationary front Neither cold air or warm air moves Can lead to long periods of precipitation

30 Weather Patterns Fronts = Stationary front symbol

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32 Videos Brain Pop Video Winds wind/ Brain Pop Video Weather weather/ Username = harpool Password = longhorns

33 Let s Practice Predicting the Weather

34 Weather Symbols Cloud Cover White = Shaded In

35 Weather Symbols Wind Direction Wind blows along the line toward the circle. Wind is always written as where it s coming from. This wind is coming from the northeast.

36 Weather Symbols Wind Speed 1 knot = 1.15 mph Big Stick = 10 knots Represents 5 Little Stick = 5 knots Flag = 50 knots Represents 10 Represents 50

37 Weather Maps High Pressure Happy Weather Isobars = Connects areas with equal pressure Low Pressure Lousy Weather