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 Very thin (averaging 11 km or 7 miles high) Densest layer 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 Absorbs?

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

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 Determines global air circulation patterns

Seasons Short periods of climatic change. Certain areas receive changing amounts of radiation throughout the year

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 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

Humidity and Cloud Cover Relative humidity Cloud Cover clouds cool the planet 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

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

Climate Climate – long term weather patterns driven by atmosphere determines distribution of biomes across Earth

What Factors Control Climate? Latitude Elevation/topography Nearby water Uneven heating of earth’s surface Ocean currents Vegetation Prevailing winds Seasons

Ocean Currents Warm/cold currents influence land climate Currents redistribute heat from sun which influences climate Gulf Stream current Upwelling-occurs along the west coasts of most continents Cold, nutrient filled water

ENSO (El Nino Southern Oscillation) Cycle Warm phase of ENSO El Nino – trade winds near SA weaken; allows warm equatorial water from the western Pacific to move eastward toward the west coast of SA Suppresses upwelling; decreases productivity Alters weather Cooler, wetter conditions in the se US Cold phase of ENSO La Nina Trade winds strengthen Upwelling of nutrient rich waters Drier conditions in the se US

“Natural” Greenhouse Effect Solar radiation passes through the atmosphere. ~51% of the sun's radiation reaches the surface This energy is then used in number of processes including: heating of the ground surface melting of ice and snow evaporation of water plant photosynthesis ~30% is reflected back to space by clouds and the surface ~19% of the energy available is absorbed by clouds and gases absorb and reradiate this outgoing radiation, storing some of the heat in the atmosphere, thus producing a net warming of the surface

“Natural” Greenhouse Effect cont. Kept the Earth's temperature about 60° F warmer than it would otherwise be.