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Download Ch. 22 - The Atmosphere part 2 - Tri-City
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5/12/15 Wind Earth’s Rotation and Winds Differences in pressure create wind Earth’s rotation influences the direction in which wind moves Commercial airplanes fly at 10 km to 13km above Earth Low pressure Difference in air pressure from one place to another is called pressure gradient We call this the Coriolis effect Points at different latitudes on Earth move at different speeds as Earth rotates Air moves from area of high pressure to areas of low pressure We call this movement of air wind Coriolis Effect Consider two houses: one on equator, one on north pole House on equator travels faster than house on pole How is this true? Earth has one full rotation every 24 hours House on equator must travel circumference of Earth Circle of latitude is smaller at pole than at equator House closer to poles moves shorter distance Thus, house at poles moves more slowly https://www.youtube.com/watch?v=i2mec3vgeaI Wind Patterns Predictable air circulation forms wind patterns Winds moving north or south are also affected by coriolis effect Winds moving north in North hemisphere curve right Winds moving south in southern hemisphere curve left Consider air moving south from north pole Wind lags behind rotation of Earth and travels West Because wind has slower speed that spinning Earth 1 5/12/15 Circulation Cells 22.3 Weather and Climate Global wind patterns form circulation cells Key Ideas: These patterns are predictable enough that people can use them to travel the entire planet How do fronts affect the weather? How is climate different from weather? Much of air moving towards poles sinks about 30 degrees in latitude High pressure area forms near surface High pressure moves toward low pressure areas and creates a loop Air in each hemisphere completes three loops called cells Key Terms Weather Air mass Meteorologist – people who study weather Front Climate Topography Gather data about weather condition Attempt to make weather forecasats Track movements of large bodies of air called air masses Interactions between air masses have predictable effects on weather Fronts and Severe Weather You may have heard of warm and cold fronts Front – place where a cold air mass and a warm air mass meet Clouds, rain, and sometimes snow occur at fronts When fronts move through an area, the result is usually precipitation and a change in wind direction and temperature 2 5/12/15 Front Types Warm Front Types: As warm air is pushed up, cools and forms clouds Warm Cold Stationary Warm front: Mass of warm air moves toward and over a slower, denser mass of cold air As warm front approaches Cirrus and cirrostratus clouds can be seen As time passes: Lower-lying clouds move overhead Often, nimbostratus clouds release steady precipitation for 1-2 days Warm Front Cold Front Forward edge of a mass of cold air moves under slower mass of warm air Pushes warm mass up Front edge of cold front is steeper than edge of warm front Causes warm air to rise quickly, forming cumulonimbus clouds creates high winds, thunderstorms, and tornadoes Cold Front Stationary Front Two fronts meet but neither is displaced Air masses will move side by side along the front Weather conditions near stationary front are similar to those near a warm front 3 5/12/15 Lightning Tornadoes Discharge of electrical energy Funnels of high-speed wind Water droplets and ice crystals build up electrical charge Most violent winds on Earth Charge builds up in one place Happen most commonly in United States Lightning may result May reach speeds of 310 mi/h Especially in Midwest Lightning instantly heats air up around it Air expands faster than speed of sound Shockwave we hear as thunder Tornadoes Tornadoes Happen most frequently in Spring and early Summer Result of high pressure rushing to low pressure Typically along front of cool, dry air and warm, humid air Typically begins as column of water droplets Called a funnel cloud Air inside funnel has very low pressure High, intense winds Rotating winds on outer edge can tear apart homes and trees Too fast and unpredictable to out run As funnel touches ground, higher air pressure rushes to low pressure inside funnel Always go to basement, or central room of house with few to no windows Why? If outside, find low-lying ditch and cover head Never under road overpasses Tornadoes Hurricanes Are large, rotating tropical storm systems Occur over warm oceans Called hurricanes North America and Caribbean Called cyclones Indian Ocean Called typhoons Western Pacific 4 5/12/15 Hurricanes Hurricanes Occur in late summer, early fall Powered by energy released as water vapor condenses to form clouds Warm water evaporates and rises Forms intense low-pressure areas called tropical depressions Tropical depressions can build strength and become hurricanes Diameters of hurricanes can be more than 373 mi. Condensing releases heat into the air Air heats up and expands Pressure inside clouds decrease Warm-moist air continues to rise and condense Releases even more energy Rising air creates fierce winds Gradually weakens as it passes over land Hurricanes Move fairly slowly but extremely powerful Winds reach 73 mi/h to 155 mi/h The eye or center is very calm Can be misleading Storm comes again, winds usually going in opposite direction as first part Climate Temperature Weather changes from day to day Tend to be warmer closer to the equator Climate does not change as quickly Climate – average weather of a region and is measured over many years Sunlight strikes Earth at different angles Surface of Earth at equator is almost always perpendicular to solar radiation The poles and solar radiation are almost parallel 5 5/12/15 Earth’s Tilt and Rotation Earth’s Tilt and Rotation Account for the seasons When North pole is pointed toward the sun Northern hemisphere More daylight in summer than in winter Earth’s orbit is an ellipse Sun rises higher into the sky in Northern hemisphere More daylight and warmer temperatures Season is now summer in northern hemisphere and winter in Southern hemisphere This causes the Earth to be farthest away from sun on July 4 and closest to sun on about January 3 Because of Earth’s tilt on its axis Different portions of Earth receive more direct sunlight in different seasons Earth’s Surface Features Topography – rise and fall of a land surface Topography of region affects climate Mountains have especially important effect on climate Air rises over mountain and cools, forming clouds Mountains near ocean – air is so humid that condensation happens easily and ocean-side of mountain gets a lot of rain Earth’s Surface Features Global Climate Changes Other side of mountain Earth’s climate has varied greatly over time Cool, dry air warms as it descends the mountain Deserts usually form on this side of the mountain Said to be in the rain shadow – clouds have released most of their moisture by the time they reach dry side of mountain Broad, flat surface like Great Plains Factors that changed it: Volcano eruptions Shifting continents Changes in Earth’s tilt over long periods of time Shorter-term climate change Do not stop wind flow Increase in human-made greenhouse gases Winds can come from far off and merge at the plains Increase in global average temperature Producing thunderstorms and even tornadoes 6 5/12/15 WORD BANK O3 Funnel cloud Oxygen Nitrogen 7
