2 2 important functions served by our atmosphere are: it protects Earth’s surface from the sun’s radiation AND it helps regulate the temperature of Earth’s surface.Without our atmosphere, we would likely die from radiation or heat.
3 Composition of the Atmosphere Permanent:Nitrogen-78%Oxygen-21%,Others - 1%Variable:Water vapor (H2O)Carbon dioxide (CO2)Ozone (O3)Particulates (dust & pollution)
4 Oxygen comprises 21% of Earth’s atmosphere. Natural processes maintain the chemical balance of oxygen in the atmosphere.Oxygen is continuously being cycled.6 ways oxygen is removed from the atmosphere1. Animals, 2. bacteria, 3. plants remove it for life processes4. Fires, 5. burning fuel, 6. chemical weathering of rocks
5 Parts of Atmosphere important to weather Water Vapor - as water evaporates from oceans, lakes, streams, and soil, it enters air as water vapor. Transpiration -the life process by which plants and animals give off water vapor Condensation & precipitation -removes water vapor as it enters the atmosphere5
6 3 factors that affect the percentage of water vapor in the air Time of dayLocationSeasonDry air has less than 1% waterMoist air may contain up to 4% water
8 Ozone Ozone high in the atmosphere is good Absorbs harmful UV rays Ozone here is formed naturally3 oxygen molecules = O3CFC’s break down good ozoneand cause the hole in the ozonelayer. This allows more of the sun’sradiation to heat the earth (globalwarming)
9 - Ozone low in the atmosphere is bad creates smogmade by humans
10 Particulates- Volcanic dust, ash from fires, pollen- Absorb water and helps to form clouds- Absorbs/reflects sunlight
11 Atmospheric PressureHolds gases of the atmosphere near Earth’s surface.The weight of the air above a point . Exerted equally in all directions.Measured with a barometerStandard Atmospheric Pressure = 1 atm or 760 mm of mercury or 1000mb11
12 Earth’s gravity keeps 99% of the total mass of the atmosphere within 32km of Earth’s surface. Because the pull of gravity is not as strong as it is at higher altitudes, the air molecules are farther apart and exert less pressure.***This is why atmospheric pressure changes with altitude!**As altitude increases, pressure decreases.
13 Besides altitude, two other factors that can cause changes in air pressure: Differences in temperatureAmount of water in the airAt sea level, when temperature increases, pressure decreases.Water molecules have less mass than nitrogen or oxygen. When air has a lot of water vapor in it, the mass of the water is less than the nitrogen/oxygen it displaced. This is why moist air is less dense than dry air is.
19 Troposphere Weather Sphere Lowest Layer Temperature decreases with height at constant rateMost cloudsMost water vaporMost airplanes fly hereTROPOPAUSE: upperboundary of troposphere
20 Stratosphere Ozone Layer Found between troposphere and mesosphere Increase Temp withheight because ozoneabsorbs UVSTRATOPAUSE – upperboundary of stratosphere
21 Mesosphere Coldest layer of atmosphere Temperature decreases to coldest point at the mesopause (upper boundary of mesosphere)(-90⁰C)Many meteors burn upin this layer.
22 Thermosphere Air is very thin. - Uppermost layer of atmosphere Temperature increases due to absorption of solar energy by nitrogen and oxygenSatellites orbit hereMESOPAUSE: lower regionof thermosphere
23 Ionosphere – part of the thermosphere Electrically charged layerAM radio waves reflect off of hereCauses auroras – phenomena caused by interactions between solar radiation & ionosphere