Paul Newman Talk

Recovery of the Antarctic ozone holeP. Newman1, E. Nash1, S. R. Kawa1, S. Montzka2, Susan Schauffler3, R. Stolarski1, S. Pawson1, A. Douglass1, J. E. Nielsen1, S. Frith1University College Dublin, Sept. 21, 2006: 

Recovery of the Antarctic ozone hole P. Newman1, E. Nash1, S. R. Kawa1, S. Montzka2, Susan Schauffler3, R. Stolarski1, S. Pawson1, A. Douglass1, J. E. Nielsen1, S. Frith1 University College Dublin, Sept. 21, 2006 Introduction Ozone Hole trends CCM model prediction of ozone hole Parametric model Controlling factors Model outline Predictions of Recovery Estimating recovery Uncertainties Climate Change and Recovery Summary 1NASA/GSFC, 2NOAA/ESRL, 3NCAR

Introduction: 

Introduction

Why is understanding ozone hole recovery important?: 

Why is understanding ozone hole recovery important? The ozone hole is the poster child of atmospheric ozone depletion Scientists staked their reputations on ozone depletion - international regulations were implemented. We need to carry our predictions through. Severe ozone holes lead to acute UV events in mid-latitudes Possible regulation changes could accelerate the phase out of ozone depleting chemicals. The ozone hole is a fundamental example of mankind’s ability to alter our atmosphere and climate - forming a useful example on climate change policy

Ozone Hole Trends: 

Ozone Hole Trends

TOMS 1984: 

TOMS 1984 October 1984 TOMS total ozone

October Average Ozone Hole: 

October Average Ozone Hole Low Ozone High Ozone

October Antarctic Ozone: 

October Antarctic Ozone

ozonewatch.gsfc.nasa.gov: 

ozonewatch.gsfc.nasa.gov

Defining the Hole: 

Defining the Hole Antarctic Ozone Hole on Oct. 4, 1998 Ozone hole area is defined by the area coverage of ozone values less than 220 DU = 24.7 M km2 220 DU located near strong gradient 220 DU is lower than values observed prior to 1979 Values of 220 tend to appear in early September. TOMS doesn’t make measurements in polar night! Values of 220 tend to disappear in late November Ozone hole minimum is 94 DU

Daily Ozone Hole Area: 

Daily Ozone Hole Area 24.7 M km2 on Oct. 4, 1998 Derive average size from an average of daily values: Sep. 7-Oct. 13

Seasonal Ozone Hole Area: 

Seasonal Ozone Hole Area

Current Conditions: 

Current Conditions

Sept. 17, 2006: 

Sept. 17, 2006 Aura OMI Ozone < 220 DU

Current Conditions: 

Current Conditions

Assessment of the ozone hole’s recovery (WMO, 2003): 

Assessment of the ozone hole’s recovery (WMO, 2003) Chapter 3 - Polar Ozone

Model area estimates: 

Model area estimates WMO Fig. 3-47

Model area estimates: 

Model area estimates WMO Fig. 3-47

Model area estimates: 

Model area estimates WMO Fig. 3-47

Minimum Ozone: 

Minimum Ozone WMO Fig. 3-47

Model Predictions Summary: 

Model Predictions Summary WMO assessment (2004): “These models suggest that the minimum column ozone may have already occurred or should occur within the next decade, and that recovery to 1980 levels may be expected in the 2045 to 2055 period.” CCM losses tend to be too small All of the CCMs underestimate the ozone hole area. In general, the CCMs overestimate the depth of the ozone hole.

What controls Antarctic ozone losses?: 

What controls Antarctic ozone losses?

PSCs: 

PSCs PSC composition & phase are key to heterogeneous reaction rates II - Crystaline water Ice ~ 188 K Ia - Crystaline particles above frost point ~ 195 K Ib - liquid particles above the frost point ~ 192 K PSCs control de-nitrification and de-hydration, which influences ozone loss Photo: Paul A. Newman - Jan. 14, 2003 - Southern Scandanavia

Antarctic ozone hole theory: 

Solomon et al. (1986), Wofsy and McElroy (1986), and Crutzen and Arnold (1986) suggest reactions on cloud particle surfaces as mechanism for activating Chlorine Cl2 is easily photolyzed by UV & blue/green light HNO3 is sequestered on PSC Antarctic ozone hole theory

Polar Ozone Destruction: 

Polar Ozone Destruction Only visible light (blue/green) needed for photolyzing ClOOCl No oxygen atoms required Net: 2O3 + h  3O2 2 O3

Chlorine and Bromine: 

Chlorine and Bromine NOZE 1 & 2 missions in 1986: High-concentrations of chlorine monoxide at low altitudes in the Antarctic spring stratosphere - diurnal-variations, R. Dezafra, M. Jaramillo, A. Parrish, P. Solomon, B. Connor, J. Barrett, Nature, 1987 AAOE mission in August-September 1987: observations inside the polar vortex show high ClO is related to a strong decrease of ozone over the course of the Antarctic spring: J. Anderson et al., JGR, 1989 Latitude (˚S) Ozone (ppmv)

Ozone Hole Area Versus Year: 

Ozone Hole Area Versus Year Polar vortex ≈ 33 Million km2

Ozone Hole Residual Area Vs. T: 

Ozone Hole Residual Area Vs. T O3 residual area: 9/21-9/30 T: 9/11 - 9/20, 50 hPa, 55-75ºS If the temperature is 1 K below normal, then ozone hole’s area will be 1.1 Million km2 larger than normal. See Newman and Nash, GRL, 2004

Problem: 

Problem We have reasonably good estimates of temperatures over Antarctica from radiosondes and satellite temperature retrievals We only have snapshots of Cl and Br over Antarctica How can we estimate Cl and Br over Antarctica for all of our observed ozone holes?

Chlorine over Antarctica: 

Chlorine over Antarctica

Ozone Loss Source Chemicals: 

Ozone Loss Source Chemicals Surface concentrations ~ 1998 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

Atmospheric Chlorine Trends from NOAA/ERL - Climate Monitoring Division: 

Atmospheric Chlorine Trends from NOAA/ERL - Climate Monitoring Division Updated Figure made by Dr. James Elkins from Trends of the Commonly Used Halons Below Published by Butler et al. [1998], All CFC-113 from Steve Montzka (flasks by GC/MS), and recent updates of all other gases from Geoff Dutton (in situ GC). 50 years 102 years 5 years 42 years 85 years Steady growth of CFCs up to 1992 CFC-11 CH3CCl3 CCl4 CFC-113 CFC-12

CFC-12 (CCl2F2) pathway to Antarctica: 

CFC-12 released in troposphere Carried into stratosphere in the tropics by slow rising circulation CFC-12 photolyzed in stratosphere by solar UV, releasing Cl Cl catalytically destroys O3 Cl reacts with CH4 or NO2 to form HCl or ClONO2 HCl and ClONO2 react on the surfaces of PSCs CFC-12 (CCl2F2) pathway to Antarctica -90 -60 -30 0 30 60 90 Latitude 1000 100 10 1 0.1 0.01 Pressure (hPa) 16 Altitude (km) 0 32 48 64 80

Mean Age-of-air: 

Mean Age-of-air

CCM mean age-of-air (Sept.): 

CCM mean age-of-air (Sept.) GSFC GEOS-4 mean age-of-air derived from advected age tracer. Magenta line is the tropopause, white lines are zonal mean zonal wind Grey lines schematically show mean flow.

CCM mean age-of-air (Sept.): 

CCM mean age-of-air (Sept.) Air at a particular point in the stratosphere is a mixture of air parcels that have come together from a multitude of pathways with different times of transit. This “spectrum” of transit time forms an “age-spectrum” that has a mean value and a spectrum “width”

Age Spectra: 

Age Spectra The spectrum is convolved with the surface observation time series to yield the stratospheric time series.

Fractional Release: 

Fractional Release

CCM mean age-of-air (Sept.): 

CCM mean age-of-air (Sept.)

CCM mean age-of-air (Sept.): 

CCM mean age-of-air (Sept.) If we know the mean age of air (), and we know the fractional release rate as a function of , then we can estimate the chlorine available from CFC-11 for ozone loss

CFC-11 break down: 

CFC-11 break down Schauffler et al. (2003)

Estimating chlorine over Antarctica: 

Estimating chlorine over Antarctica

Estimating halogen (Cl & Br) levels over Antarctica: 

Estimating halogen (Cl & Br) levels over Antarctica Observations show that it takes about 5.5 years for air to get to the Antarctic stratosphere - tropospheric CFCs in January 2000 yield Antarctic stratospheric Cl in July 2005! We use observed CFCs & mean age-of-air estimates to calculate fractional release rates as a fcn. of age EESC = equivalent effective stratospheric chlorine n = # Cl or Br atoms, f = release rate,  = chemical mixing ratio,  = scaling factor to account for Br efficiency for ozone loss

EESC: 

EESC Observed total chlorine* (surface) Estimated stratospheric chlorine

Parametric model of the ozone hole Methodfit ozone hole size to quadratic functions of EESC and temperature: 

Parametric model of the ozone hole Methodfit ozone hole size to quadratic functions of EESC and temperature

Ozone Hole Parametric Model: 

Ozone Hole Parametric Model EESCmax = 3.642 ppbv a0 = -69.5 million km2 a1 = 50.9 million km2/ppbv a2 = -1.08 million km2/K A = 0 for EESC = 1.817 ppbv  = residual area r = 0.971 (r2=.943) Area is a function of Effective Equivalent Stratospheric chlorine (EESC) and temperature EESC = 0.8 G(CCly) + G(CBry) G = Age Spectrum (6 year mean age, 3 year width) CCly and CBry from WMO (2003)

Recovery Predictions: 

Recovery Predictions

Ozone Hole Area vs. Year (1): 

Ozone Hole Area vs. Year (1)

Ozone Hole Area vs. Year (2): 

Ozone Hole Area vs. Year (2) Temperature effect is removed

Ozone Hole Area vs. Year (3): 

Ozone Hole Area vs. Year (3) Black line represents the fit of area to EESC Area residual  = 1.8 M km2 (92) Unexplained residual for 1992 ~ 3 m km2

Ozone Hole Area vs. Year (4): 

Ozone Hole Area vs. Year (4) Using WMO (2003) Cly and Bry projections, we use our fit to project the ozone hole area

Ozone Hole Area vs. Year (5): 

Ozone Hole Area vs. Year (5)

Add uncertainty to fits: 

Add uncertainty to fits EESC: We assume mean age = 5.5 years and the spectrum width = 2.75 years = EESC0 Monte Carlo mean age (= 0.5 years) and width (= 0.5 years) to generate new EESC time series = EESC1 Add 80 pptv of “noise” to EESC1 = EESC2 Area: Use original area fit (A0) + added noise re-sampled from area residuals = A1 Refit new Area (A1) as a function of EESC2 Project forward using EESC1 for calculating new recovery dates

Ozone Hole Area vs. Year (6): 

Ozone Hole Area vs. Year (6) The ozone hole area peaked in 2001 from the area fit to EESC The ozone hole area will remain large (and relatively unchanged for 20 years (1997-2017) Area will start decreasing in approximately 2017 The area will have decreased 1- by 2018 and 2- by 2027 Based upon our boot-strap statistics, recovery will first be detected in 2024 The area will be zero in 2070

Uncertainties: 

Uncertainties

Uncertainties: 

Uncertainties Are the chlorine and bromine levels over Antarctica well represented by using WMO (2003) and an age-spectrum for the 1979-2004 period? How good is WMO (2003)? New revisions (A1) increased recovery to 2070 from 2068. Is a 5.5 year mean age and a 2.75 width appropriate for the age spectrum? How do we represent interannual variability in age, Cly and Bry estimates? Will climate change impact H2O levels and the initial conditions for the ozone hole?

Full Recovery vs. mean age-of-air: 

Full Recovery vs. mean age-of-air The recovery dates are proportional to our estimate of the mean age-of-air inside the Antarctic vortex: Age sensitivity=9.0 yr/yr Critical to improve our understanding of age in the vortex and to understand age variation in future climate scenarios

Climate change effect on ozone hole recovery: 

Climate change effect on ozone hole recovery

How will climate change impact the ozone hole?: 

How will climate change impact the ozone hole? -0.25 K/decade cooling CMIP2 data from IPCC (2001) Peak size 2011 (2004) Area will start decreasing in approximately 2018 (2017) The area will have decreased 1- by 2025 (2024) and 2- by 2031 (2029) Based upon our boot-strap statistics, recovery will first be detected in 2028 (2027) The area will be zero in 2079 (2075) magenta - no T-trend No trend

Summary: 

Summary The area of the ozone hole is well represented by T and Cl and Br - We can use this to predict future size and minimum values of Antarctic ozone. Based upon our parametric model: The ozone hole will remain large for a least another decade with no evidence of improvement Actual decreases will begin in about 2017, but can not be detected until 2023 The full recovery will not occur until 2070 GHG change will have small impact on recovery Recovery is strongly dependent on age-of-air and future CFC scenarios Current coupled models are still inadequate for recovery predictions

END: 

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