Learning Objectives MET 112 Global Climate Change - Lecture 20 Ozone and UV radiation To understand the role ozone plays in the Earth’s system. Eugene Cordero San Jose State University, Spring 2004 To understand how surface UV radiation varies. Outline What is ozone, why is it important? What about UV radiation? Activity 13 MET 112 Global Climate Change What is ozone? 1 MET 112 Global Climate Change 2 How is ozone produced? Ozone is produced and destroyed naturally Production: – It is formed when oxygen absorbs solar radiation Ozone reacts with various other chemicals, and thus is highly reactive (i.e.) The ozone molecule contains three oxygen atoms, hence O3 is ozone. Net : O3 +O→ 2O2 One Cl atom can destroy ~100,000 ozone molecules MET 112 Global Climate Change 4 Why is the ozone layer important Ozone acts as the Earth’s protective shield against the Sun’s harmful Ultraviolet radiation (UV radiation). The natural development of the ozone layer permitted life to evolve above water. MET 112 Global Climate Change 7 Ozone, the good and the bad Ozone in the Atmosphere Ozone is often confused: Ozone is produced and destroyed naturally in the atmosphere. Stratosphere Good ozone: Bad ozone: Altitude (km) Ozone is also transported around by winds. The ozone layer is measured in ________________ which correspond to the__________, which is the column of ozone from the surface to the top of the atmosphere. Troposphere Ozone values change daily and from season to season, but have a ‘regular’ cycle. ozone amount Q1: At what altitude is the ozone layer a maximum? Q2: Where is the ozone layer? Ozone is responsible for the heating of the stratosphere: – ~ 23-25 km Stratosphere MET 112 Global Climate Change Dobson Units (DU) as a measure of total ozone Yesterday’s Total Ozone MET 112 Global Climate Change 14 16 MET 112 Global Climate Change 17 Total ozone over different cities Total ozone amount on October 3, 2000 over: – San Francisco _____________ DU – Punta Arenas, Chile _________DU – Darwin, Australia ____________DU – South Pole, Antarctica ________DU MET 112 Global Climate Change 18 MET 112 Global Climate Change 20 UV radiation UV radiation is emitted from the sun with wavelength from 200-400 nm (nanometers) UV radiation is divided into three ranges – UV-A, 320 - 400 nm – UV-B, 290 - 320 nm – UV-C, 200 - 290 nm MET 112 Global Climate Change 21 Ozone profile with height and UV MET 112 Global Climate Change 23 UV radiation What affects the amount of UV radiation hitting the Earth? _______________________ _______________________ _______________________ _______________________ _______________________ MET 112 Global Climate Change 24 MET 112 Global Climate Change 26 UV changes during the day Satellite image of UV radiation January June MET 112 Global Climate Change 30 MET 112 Global Climate Change Summary Questions Concept Map Terms Ozone UV radiation Sun Gas Skin Cancer Summer Winter Spring Atmosphere CFC’s South Pole Trends Ozone hole Chlorine Can ozone be replaced if it’s destroyed? Why do ozone values change from day to day? Why is the ozone layer important? What factors affect surface UV radiation intensity? MET 112 Global Climate Change 32 33 Dobson Unit Total Ozone Tropospheric ozone Good ozone Stratospheric ozone Bad ozone TOMS MET 112 Global Climate Change 35
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