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The Atmosphere and Atmospheric Ozone

The Atmosphere and Atmospheric Ozone. Dr. Paul A. Newman http://code916.gsfc.nasa.gov/People/Newman/ NASA’s Goddard Space Flight Center 2005 NASA Earth System Science Teacher Workshop NASA GSFC April 22, 2005. What are the main issues in atmospheric physics?. Ozone depletion

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The Atmosphere and Atmospheric Ozone

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  1. The Atmosphere and Atmospheric Ozone Dr. Paul A. Newman http://code916.gsfc.nasa.gov/People/Newman/ NASA’s Goddard Space Flight Center 2005 NASA Earth System Science Teacher Workshop NASA GSFC April 22, 2005

  2. What are the main issues in atmospheric physics? • Ozone depletion • Atmospheric pollution • Climate change All 3 issues are related to changing atmospheric composition

  3. Outline • Atmospheric Basics & Solar Radiation • Ozone: basics and photochemistry • Ozone loss in the atmosphere • Summary • Educational activities

  4. Atmospheric Basics

  5. Atmospheric Structure -135oF -99oF -63oF -27oF 9oF 45oF 81oF 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 20 20 10 0 0 180 200 220 240 260 280 300 Temperature (K) Thermosphere Mesosphere Stratosphere Troposphere

  6. Atmospheric Structure 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 20 20 10 0 0 Thermosphere Mesosphere Stratosphere Airliners fly at 30,000-40,000 feet Troposphere

  7. Atmospheric Structure 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 20 20 10 0 0 Thermosphere Mesosphere ER-2 flies at 70,000 feet Stratosphere Troposphere

  8. Atmospheric Structure 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 20 20 10 0 0 Thermosphere Mesosphere Oxygen (21%) Nitrogen (78%) Stratosphere Troposphere

  9. Atmospheric Composition • Nitrogen 0.781 • Oxygen 0.209 • Argon 0.009 • Water 0.014 (tropics) 0.002 (poles) 0.000004 (stratosphere) • CO2 0.000360 • O3 0.0000100 (stratosphere) 0.0000001 (troposphere)

  10. Solar Radiation: The photochemistry driver

  11. 10-12 10-10 10-8 10-6 10-4 10-2 1 The Electromagnetic Spectrum Scale (meters) -ray X-ray UltraViolet Vis InfraRed Microwave Radio H2O Protein Virus E. Coli Cell Flea Baseball Lower Energy Higher Energy 1 nm = 1x10-9 m =1 billionth of a meter

  12. IR UV Solar Energy Outside Earth’s Atmosphere (from space) Solar Energy at Earth’s Surface 1 m = 1x10-6 m =1 millionth of a meter

  13. Absorption of UV by ozone

  14. UV radiation • Solar radiation exists at a variety of wavelengths, most commonly visible radiation from 400 nm (nanometers or billionths of a meter) to about 700 nm. • UV radiation extends from 1-400 nm (invisible to the human eye). • http://sohowww.nascom.nasa.gov/data/realtime-images.html Extreme UV images from the Extreme ultraviolet Imaging Telescope (EIT), and the Michelson Doppler Imager (MDI) • A UV photon is more energetic than a visible photon, and the UV photon can break the bonds of biological molecules such as proteins and DNA. 677 nm visible radiation 04/18/2003 images 30.4 nm UV radiation 60,000-80,000 K

  15. What is ozone?

  16. Atmospheric Structure 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 Ozone Oxygen 20 20 10 0 0 Thermosphere Mesosphere Stratosphere Troposphere

  17. Ozone Facts 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 20 20 10 0 0 Thermosphere Mesosphere 90% of ozone is in the stratosphere Troposphere 0 2 4 6 8 Ozone (parts per million)

  18. Ozone Facts 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 20 20 10 0 0 Thermosphere Mesosphere Stratosphere 10% of ozone is in the troposphere 0 2 4 6 8 Ozone (parts per million)

  19. What does ozone do?Absorbs UV radiation

  20. Ozone Facts 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 20 20 10 0 0 Ozone is the Earth’s natural sunscreen UVc - 100% Absorption UVb - 90% Absorption UVa - 50% Absorption & Scattering Stratosphere 0 2 4 6 8 Ozone (part per million)

  21. Ozone Facts 100 60 80 50 40 60 Altitude (miles) Altitude (km) 30 40 20 20 10 0 0 Thermosphere Mesosphere Ozone is a pollutant, lung and esophagus irritant Stratosphere Troposphere

  22. UV Health Facts • UV pluses: produces vitamin D in the skin - necessary to maintain levels of calcium and phosphorus (10-15 minutes twice a week) • UV minuses: • Eye damage: cataracts, photokerititus (snowblinding), ocular cancers • Skin cancers: basal, squamous, melanoma • photoaging • Damage to various land speciesDamage to aquatic species • Increased pollution levels in urban environments Cataract Melanoma Mexico City

  23. Ozone Photochemistry

  24. Ozone Absorption of UV 2. An O2 reacts with An O atom to reform O3 1. O3 is split by UV radiation UV radiation (200-300 nm) converted to heat Net: O3 + h  O3 At 30 km, this reaction takes 0.1 seconds

  25. Ozone Production UV  < 240 nm O + O2 + M O3 + M O2 + h  2 O Ozone is created by oxygen molecules and energetic UV radiation Net: O2 + h  2 O3

  26. Catalytic Ozone Loss 1. 1. O3 + h  O2 + O 2. O3 + X O2 + XO 3. XO + O O2 + X Net: 2 O3 3 O2 3. 2. Principal ingredients for ozone loss: UV radiation and a free radical X = OH, NO, Cl, Br

  27. Photochemical balance

  28. Source gases for ozone loss

  29. Source Gases • Cl is much more abundant than Br • Br is about 50 times more effective at O3 destruction From Ozone FAQ - see http://www.unep.org/ozone/faq.shtml

  30. Atmospheric Chlorine Trends from NOAA/CMDL -HATS Group 102 years CFC-12 50 years Steady growth of CFCs up to 1992 5 years 42 years 85 years Figure from Trends of the Commonly Used Halons Below Published by Butler et al. [1998]

  31. Photochemical balance

  32. What’s happened to polar ozone?

  33. Antarctic Measurements Aurora over Halley Bay Station, Antarctica, 75.6ºS 26.5ºE Brunt Ice Shelf, Coats Land 105 days of continuous darkness, twice per year re-supply Population: 65 in summer, 15 in winter

  34. Digression: Dobson Units • Total Ozone is a measure of the total column amount above us. Measured in Dobson Units • If we bring all of the ozone above us down to the Earth’s surface • The thickness would be about 3 millimeters (~0.1 inches) = 300 Dobson Units (approximately the global average) • 100 Dobson Units = 1 millimeter in thickness ozone layer 2¢ 10¢ 3 mm = 300 Dobson Units • The Dobson Unit is a convenient unit of measurement for total column ozone

  35. October Antarctic Ozone • Halley Bay October Averages  Minimum value of October TOMS average

  36. Antarctic ozone hole is defined as the region covered by low ozone values Orange/Yellow indicates higher ozone levels. Dark color over pole shows the extent of polar night, no ozone observations Blue colors indicate low ozone values TOMS - August 31, 2003

  37. The 2003 Movie Greg Shirah, NASA/GSFC SVS

  38. low ozone high ozone October Average Ozone Hole

  39. Arctic & Antarctic Trends

  40. Polar Stratospheric Clouds HCl and ClONO2 react on the surface of cloud particles, releasing Cl2. As the sun rises in the spring, the Cl2 is photolyzed by visible light, starting a catalytic reaction that depletes ozone 1-2% per day! Central, Sweden January 14, 2003 - P. Newman

  41. El Chichon Pinatubo Solar maxima Volcanoes Quasi-biennial Oscillation Global Total Ozone 60˚S-60˚N

  42. What’s being done?

  43. 102 years 50 years U. S. CFC production stopped by President George Bush in 1992 5 years Montreal Protocol Signed (1987) 42 years 85 years Atmospheric Chlorine Trends from NOAA/CMDL -HATS Group CFC-12 Figure from Trends of the Commonly Used Halons Below Published by Butler et al. [1998]

  44. NASA continues to measure ozone and gases that destroy ozone

  45. Future Antarctic Ozone Levels 1.Will CFCs and halons decrease as expected? 2. Greenhouse gas warming of the lower atmosphere has a cooling affect in the stratosphere, increasing polar O3 loss 3. Stratospheric water vapor increases (of unknown origin) will increase polar O3 loss WMO Assessment [2003]

  46. What Can You Do? • Avoid excessive solar exposure (limit sun between 11AM and 2PM). • Wear and encourage others to wear sunscreen (SPF rating of 15). Even with sunscreen, prolonged exposure is not smart. • Check your skin regularly. • Wear sunglasses that screen UV. • Hats and other coverings • Make note of the UV index on the news or web: http://www.epa.gov/sunwise/uvindex.html

  47. Summary • Stratospheric ozone is a critical gas for screening solar UV radiation. • Human produced ozone destroying substances (ODS) have caused large losses of ozone over both poles and small global losses. • ODSs have been regulated under international agreements and are slowly decreasing. Ozone levels should recover within the next 50-70 years.

  48. Educational Activities and Resources • Jeannie Allen (Sr. Science Education Specialist) Jeannette_Allen@ssaihq.com 301-614-6627 • See handout prepared by Jeannie • Chem Matters http://chemistry.org/education/chemmatters.html

  49. END Jan. 10, 2003 - local noon, Kiruna, Sweden

  50. What About Global Warming?

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