Environment Canada:

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1 Polar Stratospheric t Ozone David W. Tarasick, Air Quality Research Division : tor ec ca/ 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

2 Outline The basics: what is it, where is it, why is it important? Methods of measurement Stratospheric ozone Ozone depletion Arctic ozone hole 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

3 What is ozone? Chapman Theory 1930 O 2 + h 2 ( < 240 nm) O + O oxygen molecule l ozone molecule l O + O 2 + M O 3 h + O 3 O 2 + O O + O 3 O 2 + O 2 It is the odour you smell after a lightning strike. Christian Friedrich Schönbein in 1840 detected the same odor in an electrical discharge in his laboratory in Bern, Switzerland. He recognized that the odor was not due to the electricity, but was due to the properties of a substance produced during the electrical process. He named this substance ozone (from ozein, Greek for "to smell"). 1883: Hartley identified ozone as the substance absorbing UV from the sun at wavelengths less than 290 nm Connaught Summer School in Arctic Science, July 14 18, 18,

4 Ozone is a trace gas --- only % of the atmosphere. Nevertheless it is responsible for the temperature structure of the atmosphere, due to its absorption of UV radiation, and is an important greenhouse gas as well. Dobson Unit - Definition Composition of air 77% N 2 21% O 2 ~1% H 2 O 0.9% Ar 0.04% 04% CO Centre for Atmospheric Science, Cambridge University 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

5 Stratosphere: above troposphere, permanent inversion layer (heated from above by O 3 absorption of solar UV) Troposphere: lowest part of the atmosphere, where weather occurs (heated from below by IR emission, unstable) [WMO Ozone Assessment 2002] 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

6 A) Solar spectrum above the atmosphere, from the SUSIM Atlas-1 flight (Brueckner et al., 1993) B) measured at the ground at Boulder, with Brewer #039, June 18, 1995 C) June 19, 1995 D) calculated l from curve A with 297 DU of ozone and an airmass factor of 1.05, using the absorption cross sections of Molina and Molina (1986) E) the CIE erythemal action curve. The UV-Index is computed by integrating the irradiance over the UV-B spectrum weighted by curve E, in watts m-2, then multiplying by Connaught Summer School in Arctic Science, July 14 18, 18,

7 Early History of Ozone Measurements 1880s s: Ozone layer is discovered d by UK and French scientists and is recognized to absorb UV-B radiation. 1927: The Dobson Spectrophotometer is invented, and would later be used to discover the Antarctic ozone hole. 1935: Canadian student E. H. Gowan studied with Dobson and brought a Féry spectrograph back to. Dobson s Féry spectrograph 1959: Alan Brewer, a colleague of Dobson s s, co-invents the ozonesonde Connaught Summer School in Arctic Science, July 14 18, 18,

8 Ozone Research Comes to 1961: The World Ozone Data Center is founded at EC. 1966: Routine ozone soundings start at Resolute Bay, the start of the EC s Canadian ozonesonde network : Concern is raised about ozone depletion via catalytic destruction by NO x and Cl 1982: The Brewer Ozone Spectrophotometer is invented by EC scientists McElroy, Wardle and Kerr. 1985: spearheads the Vienna Convention on the Protection of the Ozone Layer, and is the first country to sign it in : signs The Montreal Protocol on Substances that Deplete the Ozone Layer, Perhaps the single most successful international agreement to date (Kofi Annan, former Secretary General of the United Nations) Connaught Summer School in Arctic Science, July 14 18, 18,

9 The automated Brewer ozone spectrophotometer measures total ozone and spectral UV irradiation ( nm) every minutes during the daytime. It can also measure ozone using the light of a full moon when the sky is clear; this is useful in the Arctic winter. The TRIAD, pictured here, comprises three independently characterized Brewer instruments operated nearly continuously at Toronto. Total ozone measurement 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

10 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

11 Ozonesondes Attached to a radiosonde which measures pressure, temperature and water vapour. A balloon carries it into the sky, sampling ozone continuously, at all altitudes, from the ground to ~30 km. Weekly at 8 sites in Connaught Summer School in Arctic Science, July 14 18, 18,

12 ECC ozonesonde Non-reactive Teflon pump Chemical reaction of ozone with KI O3 2 I H 2 O O2 2 OH I 2 I 2 2e 2I In principle, measurement is absolute, as the device counts ozone molecules l 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

13 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

14 Brewer and ozonesonde sites in 2014 Connaught Summer School in Arctic Science, Science, July ,

15 Atmospheric Chemistry Experiment (AC Canadian Space Agency Instruments: ACE-FTS, MAESTRO Climate Change Ozone Chemistry Atmospheric Dynamics Ozone ( trop & strat) Aerosol Other Trace Species 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

Stratospheric ozone Both affects, and is affected by the large-scale circulation of the

is long (month to years) below 25 km, and much shorter at the higher altitudes of the primary

16 Stratospheric ozone Both affects, and is affected by the large-scale circulation of the atmosphere. Average values of ozone mixing ratio as a function of altitude for March Data from SAGE II. Schematic diagram of stratospheric transport [WMO Ozone Assessment 2002] The lifetime of ozone is long (month to years) below 25 km, and much shorter at the higher altitudes of the primary production region. Atmospheric transport (poleward and downward) causes it to accumulate at higher latitudes Connaught Summer School in Arctic Science, July 14 18, 18,

17 Mean total ozone by latitude and longitude for April and November (pre-1980 averages) ages) 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

18 Dynamics: Polar ozone in spring correlates well with polar stratospheric temperatures (e.g. Newmann et al., 2001) and with planetary wave activity during winter (e.g. Fusco & Salby, 1999, Randel et al., 2002, Weber et al., 2003) 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

Ozone is a renewable resource: it exists in

loss. In fact, the sun produces ozone at a

or H + reactions like XO + XO X + X + O 2

19 Ozone is a renewable resource: it exists in a quasi-steady state between production and loss. In fact, the sun produces ozone at a rate sufficient to regenerate the entire stratospheric ozone layer in ~10 days. The energy involved is about 100 times what humans use in all forms. X + O 3 XO + O 2 where X = Cl, Br, NO, OH, or H + reactions like XO + XO X + X + O Connaught Summer School in Arctic Science, July 14 18, 18,

ClNO 2 + HNO (T < -78 º C) 3 ClONO 2 + H 2 O HOCl + HNO 3 2014

20 ClO + NO 2 + M ClONO 2 + M ClO + OH HCl + O 2 Gas phase On surfaces of HCl + ClONO 2 Cl 2 + HNO 3 NAT PSCs HCl + N 2 O 5 ClNO 2 + HNO (T < -78 º C) 3 ClONO 2 + H 2 O HOCl + HNO Connaught Summer School in Arctic Science, July 14 18, 18,

21 Mean total ozone by latitude and longitude for April and November 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

22 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

23 Ozone and the UV Index: history First clear-sky UV forecast - May 1992 UV forecast with cloud correction Renewed UV Index based on WHO recommendations Connaught Summer School in Arctic Science, July 14 18, Science, 18,

24 Is it working? ) ratio (ppt l surface mixing r Global measurements expected Measurements show that CFC burdens in the atmosphere are decreasing almost as fast as expected Connaught Summer School in Arctic Science, July 14 18, 18,

25 World Avoided What would have happened to the ozone layer if ODSs had not been regulated? Annual average global ozone for the WORLD AVOIDED (solid black), reference future (red), fixed chlorine (green), and reference past (blue) simulations. The dashed line shows the 2-D coupled model simulation of the world avoided. The thin horizontal lines indicate the 220-DU level (the level usually indicating the nominal edge of the Antarctic ozone hole) and the 310-DU level (the 1980 global value). The inset shows the WORLD AVOIDED total ozone plotted against global EESC at 4.5 hpa. From Newman et al., [2009] UV index vs year for the WORLD AVOIDED (black), reference future (red), and fixed chlorine (green) simulations. The UV index is calculated using the July N zonal-mean ozone, assuming a time of local noon on 2 July. The standard UV index risk scale is superimposed at the bottom left. The horizontal grey line shows the average UV index from the fixed chlorine simulation Connaught Summer School in Arctic Science, July 14 18, 18,

Past, present, and future ozone and UV Schematic of the influence of ozone depleting substances

ozone levels to pre-1980 levels, but the expectation is that climate change will hasten this

the return of stratospheric chlorine and bromine to the 1980 benchmark value, and before the

26 Past, present, and future ozone and UV Schematic of the influence of ozone depleting substances (ODSs) and climate change on the stratospheric ozone layer, and the influence of ozone changes on surface ultraviolet radiation. Natural variability makes it difficult to identify the projected return of northern midlatitude ozone levels to pre-1980 levels, but the expectation is that climate change will hasten this return by several decades, such that it will occur before the middle of the 21st century (before the return of stratospheric chlorine and bromine to the 1980 benchmark value, and before the return of Antarctic ozone). Source: EXECUTIVE SUMMARY, WMO/UNEP Scientific Assessment of Ozone Depletion: Connaught Summer School in Arctic Science, July 14 18, 18,

27 An Arctic Ozone Hole? 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

28 Arctic 1997 Antarctic 2011 Arctic 2005 Arctic Connaught Summer School in Arctic Science, July 14 18, 18,

29 30 Eureka, Nunavut 80.1 N, 86.4 W Eureka Altitud de (km) 10 Day 26 Day 36 Day 38 (-18%) Day 45 (-32%) Day 52 (-23%) Day 55 (-26%) Day 58 (-32%) Day 60 (-31%) Day 61 (-34%) Day 62 (-29%) Day 65 (-28%) Day 66 (-29%) Day 67 (-30%) Day 68 (-39%) Day 70 (-39%) Day 71 (-39%) Feb/Mar Ozone Partial Pressure (mpa) Deviations in integrated total ozone are relative to the mean 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

30 Match project Ozonsonde station Lidar station Air mass trajectory (day/night) 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

31 Evolution of ozone profile inside vortex on e, laminae removed M. Rex and the Match team 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

32 Average ozone inside e =465K Minimum reached during 1985 Antarctic ozone hole Antarctic at this level M. Rex and the Match team 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

550 Ozone loss profiles Arctic - Antarctic Po

33 550 Ozone loss profiles Arctic - Antarctic Po otential tem mperature Antarctic: ti Arctic: Ozone hole range (indicated by 1985 & 2003) (as of March 31) Ozone loss [ppmv] M. Rex and the Match team 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

Meteorology of the Arctic lower stratosphere: a: Vortex strength (as

temperature (~18km altitude) b: Fraction of vortex volume at potential

2010. Antarctic ti dates (top axis in a) are shifted by six months to show

$c: Winter mean V psc expressed as a fraction of vortex volume.$

34 Meteorology of the Arctic lower stratosphere: a: Vortex strength (as indicated by maximum potential vorticity (PV) gradients) at 460K potential temperature (~18km altitude) b: Fraction of vortex volume at potential temperatures between 390 and 550K with a temperature t less than the chlorine activation threshold (T act ). Light (dark) grey shading shows range of Arctic (Antarctic) values for Antarctic ti dates (top axis in a) are shifted by six months to show the equivalent season. c: Winter mean V psc expressed as a fraction of vortex volume. Red, orange, green, purple and blue lines/bars show the , , , and Arctic winters, respectively Connaught Summer School in Arctic Science, July 14 18, 18,

35 Chemical composition in the lower stratosphere: Vortex-averaged time series at 485K potential temperature (~20 km) for HNO 3 (a), HCl (b), ClO (c) and O 3 (d); mixing ratios from Aura MLS are shown. Blue (purple) triangles on time series, ( ) values from UARS MLS. Light (dark) grey shading shows range of Arctic (Antarctic) values for Aura MLS measurements from Antarctic dates are shifted by six months (top axis on time series) to show the equivalent season. b c d 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

36 Long term evolution of V PSC 31 March as of 3 M. Rex and the Match team 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

37 Chemical loss of ozone in Arctic winter 2011 is larger than in any previous winter since sufficiently frequent ozonesonde measurements started in the Arctic in Based on the long term evolution of V PSC and concentrations of ODS, it is very likely the largest anthropogenic loss ever in the Arctic. Over 80% loss of ozone occurred between 18 and 20 km. The degree and vertical distribution of ozone loss is very similar to the 1985 Antarctic ozone o hole. Cold Arctic winters have become colder over the past four decades, leading to increased ozone loss during some winters since the 1990s. Rapid depletion was observed in December 2012 but a Sudden Stratospheric Warming ended the depletion in early Connaught Summer School in Arctic Science, July 14 18, 18,

38 The abnormally low stratospheric ozone in the spring of 2011 led to substantially elevated UV Indices Total ozone deviations from normal in % UV Index=8.6-45% ozone depletion March 29-40% Total ozone deviations from normal in % 48 o N April 17 Larger absolute increases of UV Indices occurred at lower latitudes during excursions of the polar vortex in April. Estimated UV index values at 48 N in Mongolia in late April were as high as June-JulyJuly values at the same latitude in 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

39 Annual mean ozone mixing ratio at 19.5 km (~60 hpa) and at 245km(~30hPa)averaged 24.5 averaged over N. Area-weighted average from a climatology using ozonesonde data with a domain-filling trajectory mapping. The influence of the 2011 Arctic ozone hole is evident. Ozone (ppmv) 2.9 Ozone (ppmv), 30 o N-90 o N, at 19.5 km ~ 60 hpa Ozone (ppmv), 30 o N-90 o N, at 24.5 km ~ 30 hpa 4.9 Ozone (ppmv) Connaught Summer School in Arctic Science, July 14 18, 18,

40 Annual mean total ozone from for several latitude bands, from ground-based and satellite data. The influence of the 2011 Arctic ozone hole is evident Connaught Summer School in Arctic Science, July 14 18, 18,

Post-1997 linear trends differ for some latitudes from ESC trend

41 Trend change after 1997 (statistically robust outside the tropics) success of Montreal Protocol! Post-1997 linear trends differ for some latitudes from ESC trend indicates additional contribution from atmospheric dynamics 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

42 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

43 February 25, Connaught Summer School in Arctic Science, July 14 18, 18,

44 March 17 17, Connaught Summer School in Arctic Science, Science, July ,

45 Questions? We need to monitor, study, and understand our environment, and our impact on it Connaught Summer School in Arctic Science, July 14 18, 18,

46 Ozonesondes can (and in general, do) yield quite accurate measurements of ozone, both in the stratosphere and in the troposphere, as this comparison of an EC ozonesonde with a UV photometer during the JOSIE96 international intercomparison experiment shows. Pressure (h hpa) Flight #1 -Ascent Photometer 5A Ozone Partial Pressure (mpa) 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

47 Factors affecting UV Index Factor Short-term fluctuations (days) Ozone 20-30% >50% increase for the Arctic and Antarctic ozone holes Clouds 90% 10-15% Long-term changes (years) 2-3% summer, 4-5% winterspring; more for the Antarctic The Solar variability Trace gases (SO 2, NO 2 ) <1% <1% 1-3% typically; 15-25% in highly polluted sites; >50% for volcanic SO 2 2-3% for highly polluted sites Albedo (snow) Up to 40% 10-15% Aerosols 10-15%, up to 90% for forest Up to 10% fires plume 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

UV Index: science 15 SPECTR RAL IRRADIANCE (W Watts/m 2 /nm) 1.0000 0.1000 0.0100 0.0010 0.

(cm -1 ) Atmospheric ozone blocks solar UV-C (100-280 nm) radiation and reduced UV- B (280-315 nm) radiation 0 290

48 UV Index: science 15 SPECTR RAL IRRADIANCE (W Watts/m 2 /nm) SURFACE < > UV-B UV-A SPACE SUNBURNING ACTION SPECTRUM OZONE ABSORPTION 10 5 OZONE AB BSORPTION COEFF FICIENT (cm -1 ) Atmospheric ozone blocks solar UV-C ( nm) radiation and reduced UV- B ( nm) radiation WAVELENGTH (nm) Ultraviolet radiation measured from space (black) and on the ground (blue). Absorption by stratospheric ozone is the main cause for the decrease by several orders of magnitude with decreasing wavelength. Also shown is the erythemal action spectrum illustrating that sunburning potential increases with decreasing wavelength The UV-Index is an irradiance scale computed by multiplying the erythemal irradiance in watts m -2 by 40. Erythemally weighted UV irradiance Toronto, May 4, Connaught Summer School in Arctic Science, July 14 18, 18,

49 What is wavelength? Hartley bands: nm Huggins bands: nm Chappuis bands: nm Wulf bands: ~ 4.7, 9.6 & 14.1 m 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

50 Column ozone and UV: climatology, monitoring, forecasting The automated Brewer ozone spectrophotometer measures total ozone and spectral UV irradiation ( nm) every minutes during the daytime. It can also measure ozone using the light of a full moon when the sky is clear; this is useful in the Arctic winter. UV Index climatology maps Estimated clear sky UV Daily max UVI Clear sky UV climatology 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

51 Stations Reporting Ozone 2014 Connaught Summer School in Arctic Science, July 14 18, 18,

Measured Ozone Depletion

Measured Ozone Depletion Global Ozone After carefully accounting for all of the known natural variations, a net decrease of about 3% per decade for the period 1978-1991 was found. This is a global average