Earth’s Oceans and Weather Systems Weather Factors

Think of a sunny summer day. When you get up in the morning, the sun is low in the sky and the air is cool. As the sun rises, the temperature increases. By noon it is quite hot. As you will see in this chapter, heat is a major factor in the weather. The movement of heat in the atmosphere causes winds to blow, ocean currents to form, temperatures to change, and rain to fall.

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

Energy from the Sun ► Electromagnetic waves are a form of energy that can travel through space. ► Electromagnetic waves are classified according to wavelength. ► The direct transfer of energy by electromagnetic waves is called radiation.

In what form does energy from the sun travel to Earth?  Visible light  Infrared radiation  Small amount of ultraviolet radiation

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

Transverse Wave

Electromagnetic Spectrum

Most of the energy that keeps Earth warm comes from the sun. Some of this energy is reflected or absorbed in the atmosphere. The rest of the energy reaches Earth’s surface, where it is reflected or absorbed.

Warming Earth ► Sunlight travels through the atmosphere to Earth’s surface. ► Earth’s surface then gives off infrared radiation. ► Much of this energy is held by the atmosphere, warming it.

What happens to energy from the sun when it reaches Earth?  Whenever the energy reaches Earth’s surface is heated, it radiates some of the energy back into the atmosphere as infrared radiation.

14-1 Energy in the Atmosphere

Heat Transfer ► Thermal Energy and Temperature The lemonade is cold, so the molecules move slowly. The herbal tea is hot, so the molecules move faster than the molecules in the lemonade. ► Inferring Which liquid has a higher temperature?

Temperature ► How is temperature measured?  Air temperature is usually measured with a thermometer.  A thermometer is a thin glass tube with a bulb on one end that contains a liquid, usually colored alcohol.

Temperature ► Temperature units are degrees. ► Two most common scales:  Scientists use the Celsius scale. ► Freezing point of pure water is 0°C ► Boiling point of pure water is 100°C.  Weather reports in the United States use the Fahrenheit scale.  Fahrenheit scale: ► Freezing point of water is 32°F ► Boiling point is 212°F.

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

How Heat Is Transferred ► Radiation: electromagnetic waves ► Conduction: direct contact of molecules ► Convection: movement of a fluid

Heat Transfer in the Troposphere

Heat 14-2

Winds ► Horizontal movement of air from an area of high pressure to an area of lower pressure. ► All winds are caused by differences in air pressure.

Anemometer ► Measures Wind Speed ► An anemometer has three or four cups mounted at the ends of spokes that spin on an axle. ► The increased cooling that a wind can cause is called the wind-chill factor.

Local winds ► Local winds are winds that blow over short distances  Caused by unequal heating of Earth’s surface ► Sea Breeze: wind that blows from an ocean or lake onto land ► Land Breeze: flow of air from land to a body of water

Monsoons ► Sea and land breezes over a large region that change direction with the seasons

Global Winds

► Coriolis Effect: Earth’s rotation makes winds curve ► It is named for the French mathematician who studied and explained it in 1835.

Longitude and Latitude

► Northern Hemisphere,  All global winds gradually turn toward the right  A wind blowing toward the north gradually turns toward the northeast.

► Southern Hemisphere  Winds curve toward the left.  A south wind becomes an southeast wind, and a north wind becomes a northwest wind.

► Coriolis Effect As Earth rotates on its axis, the Coriolis effect turns winds in the Northern Hemisphere toward the right. ► Interpreting Diagrams Which way do winds turn in the Southern Hemisphere?

Global Wind Belts ► Doldrums: Near the equator, the sun heats the surface strongly  Warm air rises steadily, creating an area of low pressure  Regions near the equator with little or no wind

Global Wind Belts ► Horse Latitudes: Warm air that rises at the equator divides and flows both north and south. ► At about 30° north and south latitudes, the air stops moving toward the poles and sinks.

Trade Winds Trade Winds ► Cold air over the horse latitudes sinks, it produces a region of high pressure. ► This high pressure causes surface winds to blow both toward the equator and away from it.

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

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

Jet Streams ► Bands of high-speed winds ► Jet streams blow from west to east at speeds of 200 to 400 kilometers per hour. ► As jet streams travel around Earth, they wander north and south along a wavy path.

14-3 Concept Map