Energy in Earth’s Atmosphere  Where does heat in the Atmosphere come from?  The sun.  In what form does this energy travel to Earth?  Electromagnetic Waves  Radiation – the direct transfer of energy by electromagnetic waves  Most energy from the sun travels in the form of:  Visible light & Infrared Radiation  Small amount as Ultraviolet Radiation

Energy in the Atmosphere  What happens to the sun’s energy before reaching Earth?  Some is Absorbed  Most by ozone layer in stratosphere  By water vapor, carbon dioxide, clouds, dust  Some is Reflected  By Clouds (reflect it back into space)  By Dust particles and gas (called scattering)  Gas mostly scatters short wavelength  why daytime sky looks blue  Some Reaches Earth’s Surface  50 % absorbed by land and water and changed to heat  most of energy then radiates back to the atmosphere as infrared radiation  Greenhouse effect – process by which gases hold heat in the air

Thermal Energy and Temperature  Review:  All substances contain tiny, constantly moving particles.  The faster they move  the more energy they have  Temperature –AVERAGE amount of energy of motion of each particle of a substance (measure of hot/cold of object)  Thermal Energy – the TOTAL energy of motion in particles of a substance

Temperature  One of the most important factors affecting weather  Thermometer – measures Temperature  Thin glass tube, bulb on one end, usually filled with mercury  Mercury expands when heated & contract when cooled  Celcius Scale - 0 is freezing/ 100 is boiling  Fahrenheit - 32 is freezing/ 212 is boiling

How is Heat Transferred  Heat –  transfer of thermal energy from hotter object to co0ler object  Transferred in Three Ways:  1. Radiation  Directly from the sun  2. Conduction  Direct transfer of heat from one substance to another by touch  Touching warm substances: ground, buildings, cars  Convection  Transfer of heat by the movement of a fluid(liquids & gases)  Movement  hot rises/ cool sinks  cycle is created

Heating the Troposphere  Radiation, conduction, & convection work together to heat the troposphere.  How?  During the day, the sun heats Earth’s surface (radiation)  Land is warmer than air  Air is warmed by radiation and conduction  Most heat is transferred by convection  CONVECTION CURRENTS

What is Wind?  The horizontal movement of air from an area of high pressure to an area of lower pressure  Caused by differences in air pressure:  Most differences in air pressure caused by unequal heating (convection currents)  Sun heats Earth’s surface  air above the heated Earth expands & is less dense  air pressure decreases(due to density)  Cooler, more dense air with higher pressure flows underneath the warm, less dense air  cooler air forces warmer air to rise

Wind  Winds are described by their direction & speed.  Direction of Winds:  Determined with a wind vane  Wind swings the wind vane in the direction it is blowing  Name of the wind identifies where it is coming from  South wind from the south; North winds from the North  Speed of Winds:  Measured with an anemometer  3 or 4 cups on the ends of a spoke that spin on an axle  A meter on the axle shows the speed

 Wind-Chill Factor  The increased cooling a wind can cause  How?  As wind blows over your skin it removes your body heat

Types of Winds: Local Winds  Local Winds  Winds that blow over short distances  Caused by unequal heating of Earth’s surface within a small area  Form ONLY when large-scale winds are weak  2 Types:  1. Sea Breeze  2. Land Breeze

Sea Breeze Land Breeze  Daytime:  sun heats the land faster than water  Air over land is warmer than air over water  Warm “land air” expands & rises  Low-pressure area  Cool “water air” blows inland from over the water and moves under the warm air  creating a breeze  Nighttime:  Land cools more quickly than water  Air over the land becomes cooler than air over the water  Warm “water air” expands and rises  Cool “land air” moves beneath the warm “water air”  creating a breeze

Global Winds  Winds that blow steadily from specific directions over long distances  Created by the unequal heating of Earth’s surface  Occur over LARGE areas  Temperature near poles are much lower than near equator  Equator + middle of the day + sun almost directly over = intense heating to the middle of the Earth  Near the Poles + sun’s rays strike Earth at lower angle + sun’s energy spread over larger area = less heat to poles

How do Global Winds Develop?  Global Convection Currents:  Temperature difference between equator and poles create GIANT convection currents  Warm air at the equator rises  lower air pressure at equator  Cold air at the poles sinks  higher air pressure at poles  Difference in pressure  winds at Earth’s surface blow from the poles toward the equator  Higher in Atmosphere  air flows away from equator toward poles

How do Global Winds Develop?  Coriolis Effect  The Way Earth’s rotation makes winds curve  As the winds blow, Earth rotates from West to East underneath  makes it seem as if the winds curve  Global winds in Northern Hemisphere turn RIGHT.  Global winds in Southern Hemisphere turn LEFT.

Global Wind Belts  Coriolis Effect + other factors = a pattern of calm areas & wind belts around Earth  Calm Areas:  Doldrums  Horse Latitudes  Major Global Wind Belts:  Trade Winds  Prevailing Westerlies  Polar Easterlies

Calm Areas  Doldrums  Regions near the equator with little or no wind  Weak Winds due to Little Horizontal motion  Heated by the sun  warm air rises = area of low pressure  Cool air moves into the area but is warmed rapidly & rises also  Horse Latitudes ( Latitude – distance from the equator)  Warm, rising air from equator flows North & South  Around 30 degrees North & South from Equator the air cools and sinks = belt of calm air  Sailors caught in these calm waters too long threw their horses over board when they no long had food/water for them.

Major Global Wind Belts  1. Trade Winds  Regions of High pressure created when the cold air over the horse latitudes sink.  High pressure causes surface winds to blow toward equator and poles  Coriolis Effect causes:  Winds blowing to Equator to turn West  Northern Hemisphere winds between 30 degrees N and the equator  blow from Northeast  Southern Hemisphere winds between 30 degrees S and the equator  blow from Southeast

Major Global Wind Belts  2. Prevailing Westerlies  Location: mid-latitudes, between 30 degrees and 60 degrees N and S  Winds that blow toward the poles from the Horse Latitudes  Turned East by the Coriolis Effect  In Northern Latitude  blow FROM the southwest  In Southern Latitude  blow FROM the northwest  Play an important role weather of the United States

Major Global Wind Belts  3. Polar Easterlies  Cold air near the poles sinks and flows back toward lower latitudes  Shift to the west due to Coriolis Effect  Meet the Prevailing Westerlies at about 60 degrees N and S  Polar Front  Mixing of warm air (Prevailing Westerlies) and cold air (Polar Easterlies)  major effect on United States Weather

 Jet Streams  About 10 km above Earth’s surface  Bands of high-speed winds  Hundreds of km wide; only few km deep  Usually blow from west to east at 200 to 400 km per hour

Water in the Atmosphere  Water cycle – movement of water between the atmosphere and Earths surface

Humidity  Humidity – measure of amount of water vapor in the air  Relative Humidity  Percentage of water vapor ACTUALLY in the air compared to the maximum amount of water vapor the air can hold at that temperature  Example:  at 10 degree C, 1 cubic meter of air CAN hold up to 8 grams of water vapor  If 8 grams of water vapor in air  relative humidity is 100 % or SATURATED  If 4 grams of water vapor in air  humidity humidity is 50 %  Psychrometer  Instrument used to measure relative humidity  Consists of two thermometers: a wet-bulb & a dry-bulb

Clouds  How do they form?  When water vapor in the air condenses to form liquid water of ice crystals  2 conditions required for Condensation:  1. Dew Point - temperature where condensation begins  Cooler air holds less water vapor than warm air.  Above freezing  water droplets form  Below freezing  ice crystals form  2. Particles – have to be present for water to condense on  In Clouds  Salt crystals, dust from soil, smoke  Solid Surface  grass, window panes  Dew vs frost

Types of Clouds  3 Main Types:  1. Cirrus  Wispy, feathery  Only at high levels with low temps  Made of Ice Crystals  2. Cumulus  Fluffy, rounded piles of cotton  Found at middle levels  If not very tall = fair weather  If towering with flat tops = thunderstorms (cumulonimbus clouds)  3. Stratus  Flat layers  Usually cover all or most of the sky  Uniform, dull, gray color  If thicken to produce drizzle, rain, or snow  called nimbostratus clouds  Cloud Names based on height:  Altocumulus – “higher” than regular cumulus  Altostratus – “higher” than regular stratus

Types of Precipitation  Rain  Sleet  Freezing Rain  Snow  Hail