9 14 15 9 16 15 9 18 15 and 9 21 15 Dr Frauenfeld Chapter 3 Earth s Modern Atmosphere I Earth s Modern Atmosphere a Atmosphere is a very thin layer of gases i If Earth was an apple the atmosphere would be the skin of the apple b Without it there would be no life on Earth i Protective filter UV rays cosmic rays gamma rays etc ii Maintains temperature c Composition of Inner Atmosphere You must know these numbers i Nitrogen 78 ii Oxygen 21 iii Argon 0 9 iv Carbon Dioxide 0 039 v Trace Gases 0 06 Regardless of where or when the air is sampled these numbers are consistent II Atmospheric Pressure a All of the gases are held down by gravity i Gravity compresses air denser near the surface ii Air thins rapidly with altitude b Fun Facts c Height i 50 of the atmospheric mass is in the bottom 5 5 km 3 4 miles ii 99 9 is below 50 km 31 miles i Pressure decreases exponentially with height ii Pressure is highest at sea level 1 Sea Level Pressure a 1 kg cm2 14 psi b 29 92 in Hg c 1013 25 millibars mb this is the one you need to know III Atmospheric Profile a Atmosphere extends to 32 000 km 20 000 miles 9 14 15 9 16 15 9 18 15 and 9 21 15 Dr Frauenfeld i Exosphere extremely few hydrogen and helium atoms are still held by gravity b Thermosphere is about 480 km 300 miles the top of the principal main atmosphere c Three ways to examine the atmosphere i Composition What particles are present ii Temperature If temperature is increasing or decreasing iii Function layers serve different purposes d Atmospheric Composition i Heterosphere Outer Atmosphere 1 Begins at 80 km 50 miles and goes up 2 0 001 of the atmosphere 3 Gases aren t blended they are sorted by gravity heterogeneous 4 stratified by atomic weight ii Homosphere Inner Atmosphere 1 Gases are evenly mixed concentrations are homogeneous 2 Extends from surface to 80 km 50 miles e Atmospheric Temperature i Thermosphere 1 80km 50 miles outward 2 Roughly the same as Heterosphere 3 Temperature is very high 2200 F but very little heat because so few particles so nothing to radiate or transfer heat ii Mesosphere 1 Temperature decreases lowest temperature in the entire atmosphere 90 C 130 F 2 50 km to 80 km 30 to 50 miles 3 Top of the mesosphere mesopause 1 Temperatures increase range between 57 C 70 F at the bottom to 0 C 32 F at the top stratopause 2 18 to 50 km 11 to 31 miles 3 Temperature increase due to the ozone layer 1 Temperature decreases at a rate of 6 4 C km 3 5 F 1000 ft as you go up in 2 Where all weather occurs hotter air is at the bottom but it wants to rise and so it mixes with the cold air which causes weather patterns 3 Extends from surface to 18 km 11 miles 4 Top is the tropopause but its height varies a Varies by latitude equator 18 km thick but at the poles 8 km thick b Varies by season c thicker with higher temperatures warm air expands iii Stratosphere iv Troposphere elevation 9 14 15 9 16 15 9 18 15 and 9 21 15 Dr Frauenfeld f Atmospheric Function i Ionosphere 1 Spans across the mesosphere and thermosphere 2 Changes incoming particles from atoms to ions i e auroras from solar winds 3 Absorbs cosmic rays gamma rays x rays and some UV rays ii Ozonosphere 1 Part of the stratosphere 2 Filters out the rest of the UV rays 3 Life wouldn t be possible without the ozone layer 4 Ozone 5 Ozone Hole a Photodissociation O2 light intense radiation O O unstable b O O2 O3 c Ozone absorbs UV radiation O3 UV O O2 This is an endless process that absorbs most of the UV radiation the absorption of the radiation explains why the temperature increases in the stratosphere a Over Antarctica b Not actually a hole but a thinning of the ozone layer c Ozone layer is normally only 3mm 1 in thick Dobson Units d There is a natural seasonal ozone hole because no ozone is created in the South Hemisphere six months out of the year e BUT synthetic compounds from refrigerants propellants and solvents Chlorofluorocarbons CFCs also end up in the stratosphere and they mess with the production of O3 UV radiation strips the Cl off of CFCs and the Cl bonds with O f Cl O ClO ClO O Cl O2 Forms more Cl which then creates more ClO ONE SINGLE CHLORINE ATOM CAN DESTROY AS MANY AS 100 000 OZONE MOLECULES It splits ozone molecules and prevents new ones from being formed g Montreal Protocol 1987 reduced and phased out the use of CFCs h Too early to say if it s getting better it isn t getting any worse 9 14 15 9 16 15 9 18 15 and 9 21 15 Dr Frauenfeld IV a Variable Atmospheric Components In addition to the nitrogen oxygen etc the atmosphere also contains i Variable gases carbon dioxide carbon monoxide methane and sulfur ii Particles smoke ash dust pollen and salt iii Chemicals smog b Sources i Natural ii Transported by winds iii Anthropogenic c Example i Mount Pinatubo erupted on June 15 1991 has to be a big eruption to have these effects 9 14 15 9 16 15 9 18 15 and 9 21 15 Dr Frauenfeld d Natural factors that affect air pollution i Winds transport variable components 1 Disperse 2 Concentrate ii Local and Regional Landscapes 1 Volcanic landscapes Volcanic Smog Vog 2 Mountain Barriers concentrated pollution 3 Valleys a Temperature Inversion temperatures normally decrease throughout the troposphere but in a valley an inversion layer where temperature suddenly increases can form i Form when a warm air mass moves in or in valleys the air closest to the ground cools off during the night so then when the sun rises the warm air is above the cold air so the two layers are stable and don t mix ii Bad because it means pollutants can t disperse and become concentrated iii CO2 Variability There is more in the colder months because plants aren t photosynthesizing in the warmer months there is less because plants are photosynthesizing 9 14 15 9 16 15 9 18 15 and 9 21 15 Dr Frauenfeld e Anthropogenic Pollution i Anthropogenic means human caused ii Types of Anthropogenic Pollution 1 Small particles of dust soot gas and pollution aerosols 2 Carbon Monoxide from burning Is also caused by natural sources like wildfires 3 Photochemical Smog completely man made produced by solar radiation hitting certain compounds and reacting with them 9 14 15 9 16 15 9 18 15 and 9 21 15 Dr Frauenfeld a Acid Rain Ozone Peroxyacetyl Nitrates PANs and Volatile Organic Compounds VOCs b Primarily from car exhaust 4 Fine Particulate Matter extremely fine dust that is harmful for …