1 UIUC ATMOS 397G Biogeochemical Cycles and Global Change Lecture 5: Atmospheric Structure / Earth System Don Wuebbles Department of Atmospheric Sciences University of Illinois, Urbana, IL February 4, 2003

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3 UIUC Dynamics, Transport, and Chemistry in UT/LS

4 UIUC Courtesy of L. Pan

5 UIUC Effect of Aircraft Emissions on Ozone Depends on Altitude of the Emissions NO + O3 --> NO2 + O2 NO2 + O --> NO + O2 O + O3 --> O2 + O2 OH + CO --> H + CO2 H + O2 + M --> HO2 + M HO2 + NO --> OH + NO2 NO2 + h --> O + NO O + O2 + M --> O3 + M CO + 2O2 + h --> CO2 + O3

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8 UIUC Ozone Density

9 UIUC Total Ozone (Dobson units)

10 UIUC Total Ozone

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13 UIUC Solar Irradiance with Altitude

14 UIUC UV Absorption by Ozone

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16 UIUC Formation of Ozone + M

17 UIUC Destruction of Ozone: Photolysis No net loss of Odd-Oxygen Oxygen atoms will likely reform ozone

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19 UIUC Destruction of Ozone: Catalytic Reactions Cl + O 3  ClO + O 2 ClO + O  Cl + O 2 ————————————— Net: O + O 3  2O 2

20 UIUC Stratospheric Ozone: Physics and Chemistry Production of Ozone The Chapman mechanism -- middle/upper stratosphere O 2 + hν  O + O ( < 240 nm) O + O 2 + M  O 3 + M (M=N 2, O 2, Ar, etc.) O3 + hν  O 2 + O O + O 3  O 2 “Smog” chemistry -- troposphere and lower stratosphere (CH 4, CO, HC) + OH  HO 2 HO 2 + NO  OH + NO 2 NO 2 + hν  NO + O O + O 2 + M  O 3 + M

21 UIUC Stratospheric O3: Physics and Chem. (cont.) Destruction of stratospheric ozone Primarily through catalytic mechanisms Examples: For X = OH or NO or Cl or Br X + O 3  XO + O 2 XO + O  X + O 2 ________________ O + O 3  2O 2

22 UIUC There have been large increases in atmospheric concentrations of greenhouse gases and in aerosols over the last century --- Human activities predominate as the causes of these increases

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25 UIUC Atmospheric Chlorine

26 UIUC Concentration of CFC-12

27 UIUC Stratospheric HCl Increase Over 1990s

28 UIUC Current and Potential Stresses on Ozone Human-induced Increasing concentrations of N 2 O (affects NOx) Increasing concentrations of CH 4 (HOx) Increasing concentrations of CO 2 (T) Aircraft emissions (NOx, H 2 O) Solid fuel rockets and space shuttle (HCl) Inc. conc. CFCs, Halons, other halocarbons (Cl, Br) Climate change (T, H 2 O, winds) Nuclear explosions (NOx) Natural Solar flux variations; solar events Volcanic eruptions

29 UIUC Temperature Dependence in Stratospheric Chemistry

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31 UIUC Observed Trends in Total Ozone Updated from Fioletov et al. (2002) Adjusted for Seasonal, QBO, and Solar Effects

32 UIUC Ozone “Hole”

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35 UIUC Antarctic Ozone ‘Hole’: Daily Minima

36 UIUC Daily Estimated Area of Ozone ‘Hole’

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46 UIUC Defining Ozone “Recovery” A lessening of the ozone decline, followed by an increase in total ozone “Recovery” occurs when total ozone returned to 1980 levels (or pre-1970 levels) Look for increase in ozone at specific levels in the atmosphere

47 UIUC Current Signs of Recovery Changes Occurring in the Concentrations of Ozone Depleting Substances (ODSs) in the Troposphere. Changes Occurring in the Concentrations of ODSs in the Stratosphere Lessening in total column ozone depletion rate at Northern mid-latitudes (?) “Stabilization” of Antarctic ozone hole by some metrics (magnitude of minimum)

48 UIUC Total Equivalent Chlorine -- Montreal Protocol Mixing Ratio of Equivalent Chlorine (ppbv) Year Equivalent Effective Stratospheric Chlorine

49 UIUC EECL -- Correlated Projection of Ozone Change Percent (%) Year Total Column Ozone Change

50 UIUC 2-D Models: Trends in Total Ozone

51 UIUC WMO 1999 Ozone Assessment Model Studies WMO 1999, total column ozone 10 models intercompared for WMO 2-D models given a specified scenario

52 UIUC Modeling the Recovery 2-D Models have been primary tools Models with interactive temperature feedback recover much sooner — ~2025 (models: NOCAR, GSFC-int) — (SUNY,AER, ULAQ, RIVM, UIUC) — >2070 to >2100 (CSIRO) Even models with T-feedback have limited dynamical feedbacks 3-D Models now becoming useful, but... Some models same as EECL (e.g., Nagashima et al. (2002) Some respond quicker (Schnadt et al., 2002) Some respond slower (Shindell, 2001; Austin et al., 2001; Dameris et al., 1998)

53 UIUC Australian 2-D Model Suggests No Recovery by 2100 Based on Randeniya et al. (2002)

54 UIUC Modeling studies: Most sensitive factors affecting recovery Cl, BrMinor, if Montreal protocol compliance N 2 OMajor (Growth inc., slower recovery) CH 4 Minor (Growth inc., slower recovery) TMajor (Decrease, faster recovery) DynamicsMajor (could be faster or slower recovery) If past due to climate change, then likely slower recovery H 2 OMajor (Increase, slower recovery) AerosolsMinor, unless major background change SolarMinor, unless major change in sun output AircraftLikely to be minor

55 UIUC Radiative Forcing on Climate