Air, Weather, and Climate

Earth’s Atmosphere Compared to the size of the Earth (12000 km), the atmosphere is a thin shell (120 km) Composed of: ~78% N2 gas 21% O2 gas 1% argon gas and other permanent gases

If the Earth is compared to this Orange… the Earth’s atmosphere would be thinner than the layer of pesticide on this Orange’s surface

Layers of the Atmosphere Troposphere Stratosphere Mesosphere Thermosphere Ionosphere Exosphere

Troposphere Closest to the earth’s surface Where we live Weather occurs here very thin (averaging 11 km or 7 miles high) Densest layer Most of nitrogen, oxygen and water vapor here Temp decreases as altitude increases

Stratosphere Above the troposphere extends to 50 kilometers (31 miles) high dry and less dense UV rays reach higher altitudes and warm them Ozone layer Ozone layer: made up of 3 oxygen atoms; absorbs UV-B and UV-C radiation

Mesosphere extends to 85 kilometers (53 miles) high temperature decrease with altitude reaching -90°C at the top

Thermosphere extends to 600 kilometers (372 miles) high temperatures go up as altitude increases due to absorption of solar radiation by oxygen molecules so few and far between that they collide rarely Farthest away from earth’s surface

Ionosphere Within the thermosphere Contains ions when hit by solar energy begin to glow and produce light Aurora Borealis reflects many types of radio waves allowing them to bounce around the world Ions=charged gas molecules Glow: driven by magnetic forces: best places to see them is in the higher latitudes

Exosphere Top of the thermosphere and continues until it merges with interplanetary gases, or space (372 to 6200 miles)

Seasonal Changes Occurs due to earth’s axis being tilted Creates opposite seasons Factor that determines global air circulation patterns

Seasons Seasons are short periods of climatic change. Certain areas receive changing amounts of radiation throughout the year Due to tilt of earth’s axis

Earth’s Seasons Earth SUMMER (Northern Hemisphere) North Pole Equator Earth South Pole WINTER (Southern Hemisphere)

Earth’s Seasons Continued…. Tilt of the Earth’s axis towards or away from the sun creates the seasons WINTER (Northern Hemisphere) North Pole South Pole Equator Earth SUMMER (Southern Hemisphere)

Weather Weather – daily temperature and moisture conditions in a place driven by atmosphere atmospheric conditions over short time periods (hours or days) in small geographic areas produced by interacting air masses Types of weather Warm Front-warm air displaces cool air Cold Front-cooler air displaces warmer air Severe-hurricanes, thunderstorms, tornadoes

Weather Contribute to Weather Air temperature Air pressure Humidity Cloud cover Precipitation Winds

Air Temperature As solar energy reaches the equator, regions heat up more than the poles. Warm air and water at the equator travel toward the poles while cold air and water at the poles travel toward the equator in an attempt to equalize the temperature Constant struggle = changing weather

http://www.usatoday.com/weather/tg/wglobale/wglobale.htm

Air Pressure Caused by the weight of air pressing down on the Earth High pressure-cool, dense air that descends towards surface of earth Fair weather Low pressure-less dense warm air goes toward the center of a low pressure air mass Produces cloudy and stormy weather Air pressure changes with weather

As air rises higher in the atmosphere, pressure decreases; lower pressure allows the rising air to expand in volume and this lowers the temp When air sinks towards the earth the pressure increases; higher pressure forces the air to decrease in volume and raises the temp of the air

Humidity and Cloud Cover Relative humidity-amount of water vapor in the air Cloud Cover clouds cool the planet by reflecting sunlight Albedo reduces the amount of heat that radiates into space

Winds Speed is determined by differences in pressure Coriolis effect Deflection of objects moving in a straight path relative to the earth’s surface Proportional to the speed of the earth’s rotation at different latitudes as latitude increases and the speed of the earth’s rotation decreases, Coriolis effect increases http://www.classzone.com/books/earth_science/terc/content/visualizations/es1904/es1904page01.cfm?chapter_no=visualization

Winds cont. Hadley cells Solar energy warms humid air in tropics Warm air rises, cools, condenses and precipitates Dry air sinks and is warmed Hot dry air causes deserts

Convection Currents