Global Weather 1
north pole northern hemisphere equator southern hemisphere south pole 2
We have seasons because of the Earth's tilt The seasons are opposite in the northern and southern hemispheres winter summer 3
High Pressure System "H" In the northern hemisphere, high pressure system winds spin clockwise, moving from the center outward High pressure systems usually bring sunny days Low Pressure Systems (L) In the northern hemisphere, a low pressure system forces winds to spin counterclockwise Air is forced toward the center of this spiral and has nowhere to go but up. As the air rises, it cools (because the atmosphere gets colder as the altitude increases) Cold air can't hold as much water vapor, so it condenses and forms clouds When the water droplets get too heavy, they may fall as rain or snow 4
Low Pressure System High Pressure System 5
High Pressure vs. Low Pressure High Pressure Area Air sinks and the pressure gets higher This makes condensation unlikely No condensation= No clouds= Happy Weather Low Pressure Area Air rises and causes the pressure to get lower Rising air cools and the water vapor in the air condenses This condensation makes clouds Condensation= Clouds= Lousy Weather 6
Global Weather Because the Earth is round and not flat, the Sun s rays don t fall evenly on the land and oceans The Sun shines more directly near the equator bringing these areas more warmth The polar regions get little or no sunlight during the winter, causing colder temperatures. These differences in temperature create a restless movement of air and water in great swirling currents to distribute heat energy from the Sun across the planet 7
Latitude Invisible lines around the globe that run west and east and measure degrees north and south of the equator 90 N 60 N 30 N 0 30 S 60 S 90 S equator Like climbing ladder rungs 8
Longitude Invisible lines around the globe that run north and south and measure degrees west and east of the prime meridian prime meridian 90 W 60 W 30 W 0 30 E 60 E 90 E 9
Global Weather Trade Winds etc.notebook Global Wind Patterns 10
W N polar easterlies westerlies trade winds trade winds E equator westerlies polar easterlies S 11
Trade Winds A belt of winds that blow towards the equator They are warm, steady breezes that blow almost continuously equator 12
Prevailing Westerlies Responsible for many of the weather movements across the United States and Canada in the northern hemisphere The winds that move toward the poles appear to curve to the east. This is because winds are named from the direction in which they originate equator 13
How the wind is blowing at the earth's surface is often different than the how it is blowing in the upper levels in the atmosphere... 14
Jet Stream Upper level winds located at the top of the troposphere A fast flowing and narrow (skinny) air current Jet streams can move weather systems around They blow most weather systems from west to east in the United States In conclusion... They are a river of air at the top of the troposphere! 15
Jet Stream 16
The Coriolis Effect "The curving of the path of a moving object caused by Earth's rotation" The Coriolis effect causes trade winds to bend/curve Winds curve to the right in the northern hemisphere Winds curve to the left in the southern hemisphere 17
Gulf Stream One of the strong ocean currents that carries warm water to higher latitudes Stretches from the Gulf of Mexico up the east coast of the United States 18
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El Niño Climate pattern where water in the Pacific Ocean near the equator becomes warmer than usual, which affects the atmosphere and weather around the world El Niño climate conditions occur every few years, and they are not predictable 20
El Niño Climate Pattern The climate pattern can change the weather of the United States, particularly in California and the southern states El Niño brings more rain and higher temperatures El Niño may also bring warmer than normal winter temperatures to the eastern part of the United States 21
El Niño Cause Effect 1 2 3 Trade winds calm down Surface water becomes warm Nutrients (food) decrease Causes warm water to come to the surface Kills nutrients Plankton, fish, and sea birds die. Scientists do not know what causes El Nino. It occurs naturally every 2 7 years and lasts for approximately 8 10 months 22
La Niña La Niña is sort of the opposite of El Niño During a La Niña, the water along the tropical west coast of South America becomes cooler, which affects weather around the globe and in the U.S. Trade winds and ocean currents bring this cold water to the surface According to scientists, La Niña cycles generally create a more active hurricane season in the Atlantic 23
La Niña Cause Effect 1 2 3 4 Warmer water is push out of the way by wind The air above the ocean in the eastern Pacific becomes cool Waters in the western Pacific become warmer Humidity and temperature increase in the west Colder waters are exposed to the surface Prevents rain needed in this part of the world (dry) Humidity and temperature increase in the west The number of rain storms increases in the west 24
El Niño warmer temperatures high pressure affect patterns of rainfall and air pressure La Niña cooler temperatures low pressure 25
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