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Weather. Weather Weather is the term used to describe the conditions that exist in a certain place for a short time.

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Presentation on theme: "Weather. Weather Weather is the term used to describe the conditions that exist in a certain place for a short time."— Presentation transcript:

1 Weather

2 Weather Weather is the term used to describe the conditions that exist in a certain place for a short time.

3 The Force Behind Weather The Sun provides the energy that forms weather. The Sun provides the energy that forms weather. Solar energy heats the equator more than the poles. Solar energy heats the equator more than the poles.

4 The Force Behind Weather As land or the ocean warms, it heats the air next to it and this air begins rising. As the heated air rises, air from elsewhere flows in to replace it. What is this type of heat transfer called?

5 Convection causes pressure changes Low pressure Low pressure –caused by rising air –counterclockwise rotation –associated with storms High pressure High pressure –caused by sinking air –clockwise rotation –associated with sunny days and calm weather

6 What causes winds? Wind is a horizontal movement of air from an area of high pressure to an area of low pressure Wind is a horizontal movement of air from an area of high pressure to an area of low pressure It is this difference in pressure that makes the air move=wind It is this difference in pressure that makes the air move=wind Winds are measured by direction and speed Winds are measured by direction and speed Wind speed is measured with an anemometer. Wind speed is measured with an anemometer.

7 Local Winds Winds that blow over short distances Winds that blow over short distances Caused by unequal heating of Earth’s surface over a small area Caused by unequal heating of Earth’s surface over a small area Often occurs near a large body of water because land heats and cools faster than water Often occurs near a large body of water because land heats and cools faster than water

8 Sea Breeze Land warms up faster than water. Land warms up faster than water. The air over the land becomes warmer than the air over the water. The air over the land becomes warmer than the air over the water. The warmer air rises and cooler air blows inland from the water. The warmer air rises and cooler air blows inland from the water.

9 Land Breeze Land cools faster than water. Land cools faster than water. The air over the land becomes cooler than the air over the water. The air over the land becomes cooler than the air over the water. The warmer air rises and cooler air blows towards the water. The warmer air rises and cooler air blows towards the water.

10 Sea Breeze vs. Land Breeze

11 Monsoons Sea and land breezes over a large region that change direction with the seasons Sea and land breezes over a large region that change direction with the seasons In the summer in South and Southeast Asia, the land gradually gets warmer than the ocean. In the summer in South and Southeast Asia, the land gradually gets warmer than the ocean. –A large “sea breeze” blows steadily inland from the ocean all summer, even at night. In the winter, the land cools and becomes colder than the ocean. In the winter, the land cools and becomes colder than the ocean. –A “land breeze” blows steadily from the land to the ocean.

12 Global Winds Winds that blow steadily from specific directions over long distances Winds that blow steadily from specific directions over long distances created by convection currents in the atmosphere created by convection currents in the atmosphere

13 Coriolis Effect Because Earth is rotating, global winds do not follow a straight path. Because Earth is rotating, global winds do not follow a straight path. As the winds move, Earth rotates from west to east underneath them, making it seem as if the winds have curved. This is called the Coriolis effect. As the winds move, Earth rotates from west to east underneath them, making it seem as if the winds have curved. This is called the Coriolis effect. Northern Hemisphere- winds turn toward right. Northern Hemisphere- winds turn toward right. Southern Hemisphere, winds curve toward left. Southern Hemisphere, winds curve toward left.

14 Global Wind Belts Doldrums Doldrums –Regions near the equator with little or no wind. Horse Latitudes Horse Latitudes –belt of calm air at about 30° north and south latitudes where the air stops moving toward the poles and sinks

15 Global Wind Belts Trade Winds Trade Winds –steady easterly winds –From the equator to 30° north latitude and 30° south latitude Prevailing Westerlies Prevailing Westerlies –blow generally from the southwest between 30° and 60° north latitudes and from the northwest between 30° and 60° south latitudes. –play an important part in the weather of the United States. Polar Easterlies Polar Easterlies –meet the prevailing westerlies at about 60° north and 60° south latitudes, along a region called the polar front. –has a major effect on weather changes in the United States.

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17 huge body of air that has similar temperature, humidity, and air pressure throughout it huge body of air that has similar temperature, humidity, and air pressure throughout it has the same characteristics of the surface over which it develops has the same characteristics of the surface over which it develops Classified by Classified by –Humidity—Continental (dry) or Maritime (humid) –Temperature—Tropical (warm, low pressure) or Polar (cold, high pressure) generally move west to east in N. America generally move west to east in N. America Air Masses

18 Air Masses in N. America

19 Fronts the boundary between air masses the boundary between air masses Caused when air masses collide Caused when air masses collide Four types— Four types— –warm –cold –stationary –occluded

20 Warm Front warm air slides over departing cold air- large bands of precipitation form warm air slides over departing cold air- large bands of precipitation form This is the symbol on a map for a warm front

21 Cold Fronts Cold air pushes under a warm air mass. Warm air rises quickly=narrow bands of violent storms form Cold air pushes under a warm air mass. Warm air rises quickly=narrow bands of violent storms form This is the symbol for a cold front

22 Occluded Front 2 cold air masses merge and force warm air between them to rise quickly. Strong winds and heavy precipitation will occur 2 cold air masses merge and force warm air between them to rise quickly. Strong winds and heavy precipitation will occur This is the weather map symbol for an occluded front

23 Stationary Front Warm or cold front stops moving. Light wind and precipitation may occur across the front boundary Warm or cold front stops moving. Light wind and precipitation may occur across the front boundary This is the weather map symbol for a stationary front

24 Currents Also Affect Weather streams of water within the oceans that move in regular patterns streams of water within the oceans that move in regular patterns Warm currents carry warm water from tropics toward the poles. Warm currents carry warm water from tropics toward the poles. Cold currents bring cold water from polar zones toward the equator. Cold currents bring cold water from polar zones toward the equator. The surface of the water warms or cools the air above it. The warmed or cooled air then moves over the nearby land. The surface of the water warms or cools the air above it. The warmed or cooled air then moves over the nearby land.

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26 Weather Maps Show locations of fronts, precipitation, air masses and other data Show locations of fronts, precipitation, air masses and other data Can be used to help predict weather Can be used to help predict weather

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