Earth’s Oceans and Earth’s Oceans and Weather SystemsWeather Systems

Weather FactorsWeather Factors

Think of a sunny summer day. Think of a sunny summer day. When you get up in the morning, When you get up in the morning, the sun is low in the sky and the the sun is low in the sky and the air is cool. As the sun rises, the air is cool. As the sun rises, the temperature increases. By noon it temperature increases. By noon it is quite hot. is quite hot.

As you will see in this chapter, As you will see in this chapter, heat is a major factor in the heat is a major factor in the weather. The movement of heat in weather. The movement of heat in the atmosphere causes the atmosphere causes temperatures to change, winds to temperatures to change, winds to blow, and rain to fall. blow, and rain to fall.

►Even though you may not feel them, Even though you may not feel them, you are being showered by you are being showered by electromagnetic waves. electromagnetic waves.

Energy from the SunEnergy from the Sun ►Electromagnetic wavesElectromagnetic waves are a are a

form of energy that can travel form of energy that can travel through space. through space.

►Electromagnetic waves are Electromagnetic waves are classified according to classified according to wavelengthwavelength..

► The direct transfer of energy by The direct transfer of energy by electromagnetic waves is called electromagnetic waves is called radiationradiation. .

In what form does In what form does energy from the sun energy from the sun

travel to Earth?travel to Earth?Visible light Visible light Infrared radiationInfrared radiationSmall amount of Small amount of ultraviolet radiationultraviolet radiation

Visible LightVisible Light

►Most of the energy from the sun Most of the energy from the sun reaches Earth in the form of reaches Earth in the form of visible light and infrared visible light and infrared radiation, and a small amount of radiation, and a small amount of ultraviolet radiationultraviolet radiation

Transverse WaveTransverse Wave

Electromagnetic SpectrumElectromagnetic Spectrum

Most of the energy that keeps Earth warm comes from the sun. Most of the energy that keeps Earth warm comes from the sun. Some of this energy is reflected or absorbed in the atmosphere. Some of this energy is reflected or absorbed in the atmosphere.

The rest of the energy reached Earth’s surface, where it is The rest of the energy reached Earth’s surface, where it is reflected or absorbed. reflected or absorbed.

Warming EarthWarming Earth► Sunlight travels through the atmosphere to Sunlight travels through the atmosphere to

Earth’s surface.Earth’s surface.► Earth’s surface then gives off infrared Earth’s surface then gives off infrared

radiation. radiation. ► Much of this energy is held by the Much of this energy is held by the

atmosphere, warming it. atmosphere, warming it.

What happens to energy from What happens to energy from the sun when it reaches Earth? the sun when it reaches Earth?

Whenever the energy Whenever the energy reaches Earth’s surface is reaches Earth’s surface is heated, it radiates some of heated, it radiates some of the energy back into the the energy back into the atmosphere as infrared atmosphere as infrared radiation.radiation.

14-1 Energy in the Atmosphere 14-1 Energy in the Atmosphere

Heat TransferHeat Transfer

► Thermal Energy and Thermal Energy and Temperature Temperature The The lemonade is cold, so lemonade is cold, so the molecules move the molecules move slowly. The herbal tea slowly. The herbal tea is hot, so the is hot, so the molecules move faster molecules move faster than the molecules in than the molecules in the lemonade. the lemonade.

► InferringInferring Which liquid Which liquid has a higher has a higher temperature? temperature?

TemperatureTemperature

►How is temperature measured? How is temperature measured? Air temperature is usually measured Air temperature is usually measured

with a thermometer. with a thermometer. A A thermometerthermometer is a thin glass tube is a thin glass tube

with a bulb on one end that contains with a bulb on one end that contains a liquid, usually colored alcohol. a liquid, usually colored alcohol.

TemperatureTemperature

►Temperature units are degrees. Temperature units are degrees. ►Two most common scales:Two most common scales:

Scientists use the Celsius scale. Scientists use the Celsius scale. ►Freezing point of pure water is 0°C Freezing point of pure water is 0°C ►Boiling point of pure water is 100°C.Boiling point of pure water is 100°C.

Weather reports in the United States Weather reports in the United States use the Fahrenheit scale.use the Fahrenheit scale.

Fahrenheit scale:Fahrenheit scale:►Freezing point of water is 32°F Freezing point of water is 32°F ►Boiling point is 212°F. Boiling point is 212°F.

►MeasuringMeasuring According According to this thermometer, to this thermometer, what is the air what is the air temperature in degrees temperature in degrees Celsius? Celsius?

How Heat Is TransferredHow Heat Is Transferred

►Radiation: Radiation: electromagnetic waves electromagnetic waves ►Conduction: Conduction: direct contact of direct contact of

moleculesmolecules►Convection: Convection: movement of a fluid movement of a fluid

Heat Transfer in the Heat Transfer in the TroposphereTroposphere

Heat 14-2Heat 14-2

WindsWinds►Horizontal movement of air from an Horizontal movement of air from an

area of area of highhigh pressure to an area of pressure to an area of lowerlower pressure. pressure.

►All winds are caused by differences in All winds are caused by differences in air pressure. air pressure.

AnemometerAnemometer►Measures Wind SpeedMeasures Wind Speed► An anemometer has three or four cups An anemometer has three or four cups

mounted at the ends of spokes that spin on an mounted at the ends of spokes that spin on an axle. axle.

► The increased cooling that a wind can cause is The increased cooling that a wind can cause is called the called the wind-chill factorwind-chill factor. .

Local windsLocal winds► Local windsLocal winds are winds that blow over short are winds that blow over short

distancesdistances Caused by unequal heating of Earth’s surface Caused by unequal heating of Earth’s surface

► Sea Breeze: Sea Breeze: wind that blows from an ocean wind that blows from an ocean or lake onto landor lake onto land

► Land Breeze: Land Breeze: flow of air from land to a body flow of air from land to a body of water of water

MonsoonsMonsoons►Sea and land breezes over a large Sea and land breezes over a large

region that change direction with the region that change direction with the seasons seasons

Global WindsGlobal Winds

►Coriolis EffectCoriolis Effect: Earth’s rotation makes : Earth’s rotation makes winds curvewinds curve

► It is named for the French mathematician It is named for the French mathematician who studied and explained it in 1835. who studied and explained it in 1835.

Longitude and Latitude Longitude and Latitude

►Northern HemisphereNorthern Hemisphere, , All global winds gradually turn toward the All global winds gradually turn toward the

rightright A wind blowing toward the north gradually A wind blowing toward the north gradually

turns toward the northeast. turns toward the northeast.

►Southern HemisphereSouthern Hemisphere Winds curve toward the Winds curve toward the leftleft. . A south wind becomes an southeast wind, A south wind becomes an southeast wind,

and a north wind becomes a northwest wind. and a north wind becomes a northwest wind.

► Coriolis Effect Coriolis Effect As Earth rotates on its axis, As Earth rotates on its axis, the Coriolis effect turns winds in the the Coriolis effect turns winds in the Northern Hemisphere toward the right. Northern Hemisphere toward the right.

► Interpreting DiagramsInterpreting Diagrams Which way do Which way do winds turn in the Southern Hemisphere?winds turn in the Southern Hemisphere?

Global Wind BeltsGlobal Wind Belts ►Doldrums: Doldrums: Near Near

the equator, the the equator, the sun heats the sun heats the surface stronglysurface strongly Warm air rises Warm air rises

steadily, creating steadily, creating an area of low an area of low pressure pressure

Regions near the Regions near the equator with equator with little or no wind little or no wind

Global Wind BeltsGlobal Wind Belts ►Horse Horse

Latitudes: Latitudes: Warm air that Warm air that rises at the rises at the equator divides equator divides and flows both and flows both north and north and south. south.

► At about 30° At about 30° north and south north and south latitudes, the latitudes, the air stops air stops moving toward moving toward the poles and the poles and sinks. sinks.

Trade Winds  Trade Winds   ►Cold air over the Cold air over the

horse latitudes horse latitudes sinks, it sinks, it produces a produces a region of high region of high pressure. pressure.

►This high This high pressure causes pressure causes surface winds to surface winds to blow both blow both toward the toward the equator and equator and away from it. away from it.

Prevailing Westerlies  Prevailing Westerlies  

► In the mid-In the mid-latitudes, winds latitudes, winds that blow toward that blow toward the poles are the poles are turned toward the turned toward the east by the east by the Coriolis effect Coriolis effect

Polar Easterlies  Polar Easterlies  

►Cold air near the Cold air near the poles sinks and poles sinks and flows back flows back toward lower toward lower latitudes. latitudes.

Jet StreamsJet Streams► Bands of high-speed Bands of high-speed

windswinds► Jet streams blow Jet streams blow

from west to east at from west to east at speeds of 200 to 400 speeds of 200 to 400 kilometers per hour.kilometers per hour.

► As jet streams travel As jet streams travel around Earth, they around Earth, they wander north and wander north and south along a wavy south along a wavy path. path.

14-3 Concept Map14-3 Concept Map

HumidityHumidity

►Humidity:Humidity: Measure of the amount of Measure of the amount of water vapor in the airwater vapor in the air

►Relative HumidityRelative Humidity: Percentage of : Percentage of water vapor in the air compared to the water vapor in the air compared to the maximum amount the air could hold maximum amount the air could hold

Measuring Relative Measuring Relative HumidityHumidity

►Relative humidity can be Relative humidity can be measured with a psychrometer. measured with a psychrometer.

►A A psychrometerpsychrometer has two has two thermometers, a wet-bulb thermometers, a wet-bulb thermometer and a dry-bulb thermometer and a dry-bulb thermometer. thermometer.

Relative Humidity Relative Humidity ► For example, at 10°C, 1 cubic meter of air can For example, at 10°C, 1 cubic meter of air can

hold a maximum of 8 grams of water vapor. hold a maximum of 8 grams of water vapor. ► If there actually were 8 grams of water vapor in If there actually were 8 grams of water vapor in

the air, then the relative humidity of the air the air, then the relative humidity of the air would be 100 percent. would be 100 percent.

► If the air held 4 grams of water vapor, the If the air held 4 grams of water vapor, the relative humidity would be half, or 50 percent. relative humidity would be half, or 50 percent.

► The amount of water vapor that the air can hold The amount of water vapor that the air can hold depends on its temperature. depends on its temperature.

► Warm air can hold more water vapor than cool Warm air can hold more water vapor than cool air. air.

Interpreting Data Interpreting Data ►At lunchtime you At lunchtime you

use a use a psychrometer and psychrometer and get readings of get readings of 26°C on the dry-26°C on the dry-bulb thermometer bulb thermometer and 21°C on the and 21°C on the wet-bulb wet-bulb thermometer. thermometer.

►Use the table to Use the table to the left to find the the left to find the relative humidity. relative humidity.

Interpreting Data Interpreting Data ► Later in the day you Later in the day you

use the use the psychrometer again psychrometer again and this time get and this time get readings of 20°C on readings of 20°C on the dry-bulb the dry-bulb thermometer and thermometer and 19°C on the wet-19°C on the wet-bulb thermometer. bulb thermometer.

► Find the new Find the new relative humidity. relative humidity.

► Is the relative Is the relative humidity increasing humidity increasing or decreasing? or decreasing?

How Clouds FormHow Clouds Form

► Clouds form when water vapor in the air Clouds form when water vapor in the air becomes liquid water or ice crystals. becomes liquid water or ice crystals.

► The process by which molecules of water vapor The process by which molecules of water vapor in the air become liquid water is called in the air become liquid water is called Condensation Condensation

►How does water condense? How does water condense? As you know, cold air can hold less water vapor than As you know, cold air can hold less water vapor than

warm air. As air cools, the amount of water vapor it warm air. As air cools, the amount of water vapor it can hold decreases. Some of the water vapor in the can hold decreases. Some of the water vapor in the air condenses to form droplets of liquid water. air condenses to form droplets of liquid water.

Dew PointDew Point

►The temperature at which condensation The temperature at which condensation begins is called the begins is called the Dew PointDew Point. .

► If the dew point is below the freezing If the dew point is below the freezing point, the water vapor may change point, the water vapor may change directly into ice crystals. directly into ice crystals.

►When you look at a cloud, you are When you look at a cloud, you are seeing millions of tiny ice crystals or seeing millions of tiny ice crystals or water droplets. water droplets.

Cloud Formation Cloud Formation Humid air cools as it is Humid air cools as it is blown up the side of a mountain. blown up the side of a mountain. PredictingPredicting What happens when water vapor condenses What happens when water vapor condenses

out of the air? out of the air?

Classifying CloudsClassifying Clouds

►Meteorologists classify clouds into Meteorologists classify clouds into three main types: three main types: CumulusCumulus Stratus Stratus CirrusCirrus

►Clouds are also classified by their Clouds are also classified by their altitudealtitude. .

►Each type of cloud is associated with a Each type of cloud is associated with a differentdifferent type of type of weatherweather

CumulusCumulus

►Clouds that look like fluffy, rounded Clouds that look like fluffy, rounded piles of cotton piles of cotton

►CumulusCumulus means “heap” or “mass.” means “heap” or “mass.” ►Form less than 2 kilometers above the Form less than 2 kilometers above the

ground, but may grow in size and ground, but may grow in size and height until they extend upward as height until they extend upward as much as 18 kilometers. much as 18 kilometers.

► Indicate fair weatherIndicate fair weather

StratusStratus

►Clouds that form in flat layers are called Clouds that form in flat layers are called stratusstratus clouds. clouds.

►StratoStrato means “spread out.” means “spread out.” ►Stratus clouds usually cover all or most Stratus clouds usually cover all or most

of the sky. of the sky. ►As stratus clouds thicken, they may As stratus clouds thicken, they may

produce drizzle, rain, or snow. produce drizzle, rain, or snow. ►They are then called nimbostratus They are then called nimbostratus

clouds. clouds.

CirrusCirrus

►Wispy, feathery clouds are called Wispy, feathery clouds are called cirruscirrus clouds. clouds.

►Feathery “hooked” ends are Feathery “hooked” ends are sometimes called mare’s tails. sometimes called mare’s tails.

►Cirrus clouds form only at high levels, Cirrus clouds form only at high levels, above about 6 kilometers, where above about 6 kilometers, where temperatures are very low. temperatures are very low.

►As a result, cirrus clouds are made of As a result, cirrus clouds are made of ice crystals. ice crystals.

14-4 Concept Map14-4 Concept Map

PrecipitationPrecipitation

►This water eventually returns to the This water eventually returns to the surface as precipitation. surface as precipitation.

►PrecipitationPrecipitation is any form of water is any form of water that falls from clouds and reaches that falls from clouds and reaches Earth’s surface. Earth’s surface.

Measuring PrecipitationMeasuring Precipitation

►Meteorologists measure rainfall Meteorologists measure rainfall with a rain gaugewith a rain gauge

►open-ended can or tube that collects open-ended can or tube that collects rainfall. The amount of rainfall is rainfall. The amount of rainfall is measured by dipping a ruler into the measured by dipping a ruler into the water or by reading a marked scale.water or by reading a marked scale.

Rain Gauge Rain Gauge A rain gauge measures the A rain gauge measures the depth of rain that falls. depth of rain that falls.

ObservingObserving How much rain was collected in How much rain was collected in

the measuring tube of this rain gauge?the measuring tube of this rain gauge?

Controlling PrecipitationControlling Precipitation

► In some regions, there may be periods In some regions, there may be periods that are much drier than usual. that are much drier than usual.

►Long periods of unusually low Long periods of unusually low precipitation are called precipitation are called droughtsdroughts. .

►Droughts can cause great hardship. Droughts can cause great hardship. ► In the farming regions of the Midwest, In the farming regions of the Midwest,

for example, droughts may cause for example, droughts may cause entire crops to fail. entire crops to fail.