Atmosphere and Climate AP Environmental Science Chapters 7.1 and 18 Miller 16 AP ed. Thank you, Mark Ewoldsen, Ph.D. ---Dr. E ---rev. k2h2/14

Origin of Modern Atmosphere original atmosphere surrounded the homogenous planet Earth and probably was composed of H and He second atmosphere evolved from gases from molten Earth –H 2 O, CO 2, SO 2, CO, S 2, Cl 2, N 2, H 2, NH 3, and CH 4 –allowed formation of oceans and earliest life modern Atmosphere –evolved after Cyanobacteria started photosynthesizing –oxygen produced did not reach modern levels until about 400 million years ago

Compared to the size of the Earth (10 4 km), the atmosphere is a thin shell (120 km). If the Earth was an orange, the atmosphere would be the pesticides on its peel Earth’s Atmosphere

Exosphere Thermosphere (Ionosphere) Mesosphere Stratosphere Troposphere Atmosphere Layers

Stratosphere extends to 50 kilometers (31 miles) high dry and less dense temperature in this region increases gradually to -3 degrees Celsius, due to the absorption of ultraviolet radiation ozone layer absorbs and scatters the solar ultraviolet radiation ninety-nine percent of "air" is located in first two layers every 1000-m 11% less air pressure

Troposphere 8 to 14.5 kilometers high (5 to 9 miles) most dense the temperature drops from about 17 to -52 degrees Celsius almost all weather is in this region

Composition Nitrogen (N 2, 78%)Nitrogen Oxygen (O 2, 21%)Oxygen Argon (Ar, 1%) myriad of other very influential components are also present which include the Water (H 2 O, 0 - 7%), "greenhouse" gases or Ozone (O 3, %), Carbon Dioxide (CO 2, %),WaterOzone Carbon Dioxide

Weather

Humidity relative humidity is the amount of water vapor in the air compared with the potential amount at the air's current temperaturerelative humidity is the amount of water vapor in the air compared with the potential amount at the air's current temperature –expressed as a percentage –depends on air temperature, air pressure, and water availability the Earth has about 326 million cubic miles of waterthe Earth has about 326 million cubic miles of water only about 3,100 cubic miles of this water is in the air as water vapor > clouds > precipitationonly about 3,100 cubic miles of this water is in the air as water vapor > clouds > precipitation

Cloud cover 40%moisture in the atmosphere forms clouds which cover an average of 40% of the Earth at any given time a cloudless Earth would absorb nearly 20 percent more heat from the sun clouds cool the planet by reflecting sunlight back into space. This is known as Albedo However clouds reduce the amount of heat that radiates into space by absorbing the heat radiating from the surface and reradiating some of it back down the process traps heat like a blanket “Cloud cloudlg.htmwww.nasm.si.edu/earthtoday/ cloudlg.htm -Dec :52:11 EST

Precipitation Air containing water vapor cools in atmosphere and therefore condenses to form droplets of liquid water –Rain: liquid, falls, d >0.5 mm (sphere) –Freezing Rain: occurs when drop touches frozen surface –Sleet: ice pellets, d < 0,5 mm, begins as rain but enters air below freezing –Snow: water deposits in hexagonal nuclei below freezing –Snow Pellets: grains of ice, d = 2-5 mm –Hail: mm in diameter, concentric rings of ice

Other Factors that effect precipitation: -Prevailing winds -Mountain ranges

Winds horizontal wind moves from areas of high to low pressurehorizontal wind moves from areas of high to low pressure vertical wind moves from low to high pressurevertical wind moves from low to high pressure speed is determined by differences in pressurespeed is determined by differences in pressure Coriolis effect causes winds to spiral from high pressure zones and into low pressure zonesCoriolis effect causes winds to spiral from high pressure zones and into low pressure zones Spring98/feature_story.htm

Winds wind speed is detected by an anemometer direction is detected by a weather vane wind direction is based on where the wind is coming from: wind from the east is an easterly Beaufort Wind Speed Scale is has a range from 0 for calm to 12 for a hurricane with waves greater than 37 feet transcripts/1999/07/07.htm

Severe Weather - Thunderstorms occur from equator to Alaskaoccur from equator to Alaska may have hail, strong winds, lightning, thunder, rain & tornadoesmay have hail, strong winds, lightning, thunder, rain & tornadoes moist air rises due to frontal zone lifting causing loss of heat leading to cumulus clouds with updraftsmoist air rises due to frontal zone lifting causing loss of heat leading to cumulus clouds with updrafts at 42,000 feet downdrafts and precipitation startat 42,000 feet downdrafts and precipitation start may last an hourmay last an hour severe thunderstorms occur when cold front approaches warm front (which supplies moisture and energy)severe thunderstorms occur when cold front approaches warm front (which supplies moisture and energy) –winds over 60 mph –hail > 3/4 inch

Severe Weather - Tornadoes swirling masses of air with speeds of 300 mph+swirling masses of air with speeds of 300 mph+ waterspouts occur over waterwaterspouts occur over water center of tornado is extreme low pressure which causes buildings to implodecenter of tornado is extreme low pressure which causes buildings to implode destruction is usually less than 0.5 miles wide and 15 miles longdestruction is usually less than 0.5 miles wide and 15 miles long tornado alley is from Texas to Indiana (usually trailer homes)tornado alley is from Texas to Indiana (usually trailer homes) Wizard of Oz!Wizard of Oz!

Severe Weather - Hurricanes cause most property damage and loss of lifecause most property damage and loss of life winds speeds greater that 74 mph at the centerwinds speeds greater that 74 mph at the center begin over warm oceans of the tropicsbegin over warm oceans of the tropics solar insolation (water >80 o F) provides energy for huge evaporation, cloud formation, and atmospheric liftingsolar insolation (water >80 o F) provides energy for huge evaporation, cloud formation, and atmospheric lifting Thorpe, Gary S., M.S., (2002). Barron’s How to prepare for the AP Environmental Science Advanced Placement Exam

Severe Weather - Hurricanes stagesstages –separate thunderstorms over tropical ocean –cyclonic circulation which causes them to pick up more more moisture and heat energy from ocean –winds speeds of 23 to 40 mph lead to Tropical Depression –Tropical Storms have lower pressure and higher wind speeds (40-75) center is called the eyecenter is called the eye rainfall may exceed 24 inches in 24 hoursrainfall may exceed 24 inches in 24 hours

The El-Niño Southern Oscillation (ENSO) Occurs every few years ENSO’s occur when the prevailing westerly winds weaken or cease and surface waters along the South and North American Coasts become warmer Upwellings of cold nutrient rich waters are suppressed Leads to declines in fish populations

ENSO events result from weakening of tropical Pacific atmospheric and oceanic circulation Climatic connections carry these climate effects throughout the globe (e.g., El Niño creates warm winters in AK and lots of rain in California) 2.19

La Nina The opposite of el Nino is La Nina.The opposite of el Nino is La Nina. During La Nina, the winds blowing across the Pacific are stronger than normal and warm water accumulates in the western Pacific. The water near Peru is colder.During La Nina, the winds blowing across the Pacific are stronger than normal and warm water accumulates in the western Pacific. The water near Peru is colder. This causes droughts in the southern United states and excess rainfall in the northwestern Untied States.This causes droughts in the southern United states and excess rainfall in the northwestern Untied States.

Climate Definitions: Average long term weather of an area –Seasonal variations and weather extremes averaged over a long period (at least 30 years) 2 Main factors –Temperature –Precipitation amount distribution

Climate Continued… Factors that effect temperature: –Latitude

Unequal Heating of Earth This unequal heating is because: The variation in angle at which the Sun's rays strike The amount of surface area over which the Sun's rays are distributed Some areas of Earth reflect more solar energy than others. (Albedo)

Latitude Latitude is the measure of the distance north and south of the equator.Latitude is the measure of the distance north and south of the equator. –Measured in degrees. Areas close to the equator, or 0 degrees latitude, receive the direct rays of the sun. These direct rays provide the most radiant energy.Areas close to the equator, or 0 degrees latitude, receive the direct rays of the sun. These direct rays provide the most radiant energy. –Areas near the equator are warm. –Polar regions are cold.

High Latitudes During the year, the high latitudes near the poles have great differences in temperature and daylight hours.

Seasonal Changes Occur because the earth’s axis is tilted Creates opposite seasons in the northern and southern hemisphere Factor that determines global air circulation patterns

Seasons Seasons are short periods of climatic change.Seasons are short periods of climatic change. Because the Earth is tilted, certain areas of Earth receive changing amounts of radiation throughout the year.Because the Earth is tilted, certain areas of Earth receive changing amounts of radiation throughout the year.

Earth’s Seasons North Pole Earth When the north pole tilts toward the sun, it gets more radiation – more warmth during the summer SUMMER (Northern Hemisphere) South Pole WINTER (Southern Hemisphere) When the north pole tilts toward the sun, the south pole tilts away So when it’s summer in the north, it’s winter in the south Equator

Tilt of the Earth’s axis towards or away from the sun creates the seasons Earth’s Seasons Continued…. When the north pole tilts away from the sun, it gets less radiation – So it’s colder during the winter Earth WINTER (Northern Hemisphere) SUMMER (Southern Hemisphere) When the north pole tilts away from the sun, the south pole tilts toward it… When it’s winter in the north, it’s summer in the south North Pole South Pole Equator

Atmospheric Convection Currents Air has four properties that determines its movement: –Density- less dense air rises, denser air sinks. –Water vapor capacity- warm air has a higher capacity for water vapor than cold air. –Adiabatic heating or cooling- as air rises in the atmosphere its pressure decreases and the air expands. Conversely, as air sinks, the pressure increases and the air decreases in volume. –Latent heat release- when water vapor in the atmosphere condenses into liquid water and energy is released.

Formation of Convection Currents Atmospheric convection currents are global patterns of air movement that are initiated by the unequal heating of Earth.Atmospheric convection currents are global patterns of air movement that are initiated by the unequal heating of Earth. Hadley cells- the convection currents that cycle between the equator and 30˚ north and south.Hadley cells- the convection currents that cycle between the equator and 30˚ north and south. Intertropical convergence- the area of Earth that receives the most intense sunlight and where the ascending branches of the two Hadley cells converge.Intertropical convergence- the area of Earth that receives the most intense sunlight and where the ascending branches of the two Hadley cells converge. Polar cells- the convection currents that are formed by air that rises at 60˚ north and south and sinks at the poles (90˚ north and south)Polar cells- the convection currents that are formed by air that rises at 60˚ north and south and sinks at the poles (90˚ north and south)

Coriolis Effect As Earth rotates, its surface moves much faster at the equator than in mid-latitude and polar regions. The faster rotation speeds closer to the equator cause a deflection of objects that are moving directly north or south.

You Tube on Coriolis Effect Coriolis EffectCoriolis Effect

YOU TUBE: CORIOLIS EFFECT ON A MERRY-GO-ROUND

YOU TUBE CORIOLIS EFFECT (PBS)

Climate Continued… Factors that effect temperature: –Latitude –Elevation

Elevation

Climate Continued… Factors that effect temperature: –Latitude –Elevation –Closeness to large bodies of water

Closeness to Large Bodies of Water Water moderates the temperature creating cooler summers and warmer winters

Ocean Currents Sea-surface temperature influences air temperature as the ocean exchanges heat with the overlying atmosphere. Evaporation rates are generally higher where sea-surface temperature is higher

Some of the water that flows from the Gulf of Mexico to the North Atlantic freezes or evaporates, and the salt that remains behind increases the salt concentration of the water.Some of the water that flows from the Gulf of Mexico to the North Atlantic freezes or evaporates, and the salt that remains behind increases the salt concentration of the water. This cold, salty water is relatively dense, so it sinks to the bottom of the ocean, mixing with deeper ocean waters.This cold, salty water is relatively dense, so it sinks to the bottom of the ocean, mixing with deeper ocean waters. These two processes create the movement necessary to drive a deep, cold current that slowly moves past Antarctica and northward to the northern Pacific Ocean.These two processes create the movement necessary to drive a deep, cold current that slowly moves past Antarctica and northward to the northern Pacific Ocean.

Ocean Currents Ocean Currents There are two type of Ocean Currents: 1. Surface Currents--Surface Circulation –These waters make up about 10% of all the water in the ocean. –These waters are the upper 400 meters of the ocean.

Ocean Currents 2. Deep Water Currents These waters make up the other 90% of the ocean These waters move around the ocean basins by density driven forces and gravity. These deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase.

Ocean Currents Ocean Currents are influenced by two types of forces 1. Primary Forces--start the water moving 1. Solar Heating 2. Winds 3. Gravity 4. Coriolis 2. Secondary Forces--influence where the currents flow

The Rain Shadow Effect