THE ATMOSPHERE COMPOSITION Invisible mixture of gases Nitrogen & Oxygen most common in lower level Hydrogen more common in upper atmosphere Water Vapor & Carbon dioxide in smaller amounts Other materials Salt Rock particles & dust STRUCTURE 1st Layer (bottom) : Troposphere Height from Earth is 7km to 16 km Temperature around 65ºF Air pressure & density decreases as you go up Tropopause: boundary 2nd Layer Stratosphere Height 50 km from the troposphere Temperature 55º F Upper region contains oxygen (ozone layer) Absorbs UV radiation STRUCTURE Stratopause: Boundary 3rd Layer: Mesosphere Height from stratosphere is 80 km Temperature 100º F meteors burn up in this layer Mesopause: Boundary 4th layer: Thermosphere Height from Mesosphere about 500 km Some space craft orbit here Absorbs a lot of radiation Temperature 1000 ºF Contains ionosphere Electronically charged particles (ions) are in place by Earth’s magnetic field Radio signals can be reflected STRUCTURE Thermopause: Boundary 5th Layer: Exosphere Extends into outer space Satellite orbit here Van Allen belts found here (collects radiation from sun to protect us) HEAT TRANSFER IN THE ATMOSPHERE Radiation: energy that travels in the form of waves (a wave is a carrier of energy) Earth & atmosphere are heated by radiation Is absorbed or reflected Wavelength: distance from the crest of one wave to the crest of another wave Waves with short wavelengths have more energy than waves with long wavelengths HEAT TRANSFER IN THE ATMOSPHERE Radiant Energy 30 % is reflected back by the atmosphere, clouds & Earth’s surface 20 % is absorbed by atmosphere 50 % is absorbed by Earth’s surface The surface cools, long waves of energy are given off The surface warms, it absorbs long waves of energy (greenhouse effect) GREENHOUSE EFFECT Greenhouse Effect: the rise in temperature that the Earth experiences because certain gases in the atmosphere trap energy from the sun. Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF colder. Greenhouse gases: water vapor, carbon dioxide, nitrous oxide, and methane Runaway Greenhouse Effect: could cause melting of glaciers, burns off protective atmospheric layers, rise in oceans occurs on planet Venus WAYS OF MOVEMENT As radiant energy is absorbed by the earth or atmosphere, it moves from high concentration to low concentration 1. Conduction: heat moves from one object to another while in contact with each other 2. Convection: heat energy is moved by a carrier (ex: water, wind) Convection current: continuous movement of air (think of convection currents in Earth’s mantle) DEW POINT Dew point – temperature to which air must be cooled to become saturated. (it will rain) - When relative humidity (amount of moisture in air) is high dew point is close to air’s temperature. * Temperature doesn’t need to be lowered much for saturation. * If relative humidity is lower; dew point is much less than air temperature so need a large decrease in temperature for saturation THE WATER CYCLE The water cycle has no starting or ending point 96% of Earth’s water is in the ocean The Sun drives the water cycle as it heats Earth’s oceans and rivers Evaporation: water that is heated turns into a gas (water vapor) and enters Earth’s atmosphere Sublimation: ice and snow can be directly turned from a solid into a gas TRANSPIRATION The process of evaporation from plants is called transpiration. (In other words, it’s like plants sweating.) CONDENSATION As water (in the form of gas) rises higher in the atmosphere, it starts to cool and become a liquid again. This process is called condensation. When a large amount of water vapor condenses, it results in the formation of clouds. You can see this at home when you take a shower and the windows and mirrors in the bathroom fog up. You can also do this by breathing on a mirror. PRECIPITATION Precipitation occurs when so much water has condensed that the air cannot hold it anymore. The clouds get heavy and water falls back to the earth. Forms: rain, hail, sleet or snow ACCUMULATION When rain falls on the land, some of the water is absorbed into the ground forming pockets of water called groundwater. Most groundwater eventually returns to the ocean. Other precipitation runs directly into streams or rivers. Water that collects in rivers, streams, and oceans is called runoff. AQUIFERS! Runoff, and ground-water seepage, accumulate and are stored as freshwater in lakes. Not all runoff flows into rivers, though. Much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes AQUIFERS (saturated subsurface rock), which store huge amounts of freshwater for long periods of time. WATER CYCLE Over time, though, all of this water keeps moving, some to reenter the ocean, where the water cycle "ends" ... oops - I mean, where it "begins." MORE ON RAIN Process to form rain. A. Warm-cloud process - tiny droplets form by condensation and then grow by bumping into and combining with other droplets. - different sizes are more likely to join than same size. - in the cloud longer, larger droplets. - larger droplets grow around a large salt nuclei. ( condensation nuclei) - droplets shrink from evaporation when falling. MORE ON RAIN B. Ice process - in upper layer of clouds - super cooled water evaporates quickly and deposits on the ice crystal. - larger ice crystals get heavy enough, the start to fall. - as they fall they will melt with warmer temperatures. CLOUDS Clouds- water droplets and /or pieces of ice floating in atmosphere. - most form in troposphere - indicated direction and speed of wind and amount of water vapor by shape and position. *For water to condense from air 1. air must contain water vapor 2. condensation nuclei (dust in air) 3. air temperature must drop to the dew point. CLOUDS * Air cools by: 1. Coming into contact with cool surface . ex. Cold water 2. As heat radiates from it into space. ex. Fog forms in early morning after clear nights temp. near ground decreases to dew point. ( fog is cloud near ground) 3. As air rises it cools ex. Clouds form when air rises to dew point. Causes flat bases on clouds Temperature changes occurring without heat – adiabatic changes. TYPES OF CLOUDS Clouds: named by shape. 1. Cumulus- heaped, fluffy clouds often flat base. Form- warm air rises, only when temperature falls to dew point. Found- all altitudes Shows- fair weather below 2km and 7km are altocumulus above 7km are cirrocumulus. - may extend into atmosphere this forms thunder heads- cumulonimbus May bring violent weather. (thunder, hail, lightening and tornadoes) * nimbus or nimbo- cloud is precipitating. TYPES OF CLOUDS 2. Stratus- spread out where large body air slowly lifted. - indicate rainy weather - block sun for long periods of time below 2km and 7km are altostratus. above 7km are cirrostratus * cirrostratus causes a halo around sun or moon. Nimbostratus- light but steady rain or snow that lasts more than a day. 3. Cirrus- feathery at high altitudes. thin and wispy Form- temperature is below freezing- made of ice crystals. Found- where air is thin Shows- fair-weather CLUES TO WEATHER Cirrus clouds followed by cirrostratus- rainy period, temperature increases. Cumulus followed by Cumulonimbus- short period of heavy rain and temperature decreases.
