1. Evaluation of total ozone recovery inside the Antarctic vortex
A. Pazmino1, S. Godin-Beekmann1, A. Hauchecorne1, C. Claud2, F. Lefèvre1, S. Khaykin1, F. Goutail1, J. P. Pommereau1, C. Boonne3, E. Wolfram4, J. Salvador4, E. Quel4
LATMOS, CNRS/UVSQ/UPMC, France, (2) LMD, CNRS/Ecole Polytechnique, France, (3) IPSL, CNRS/UPMC, France, (4) CEILAP-UNIDEF, MINDEF/CONICET, Argentina
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CONTEXT
METHODOLOGY
DATA
Stabilization of the ozone loss in Antarctica since 2000
Important interannual variability in last decade
Significant increase of total ozone linked to Ozone depleted substances decrease (healing) not yet established for October and Sep-Oct-Nov average period (WMO, 2014)
Onset of healing process detected by Solomon et al., 2016 using satellites/sondes data in September. Data of particular years 2002 (SSW) and 2015 (influence of stratospheric aerosols from Calbuco volcano) not considered
But not significant increase in October when ozone depletion is maximum
Trend of total ozone columns (TOC) inside the vortex over period using multilinear regression model
Ozone trend simulated by a piecewise linear trend (PWLT) before and after the break year in 2000
Maximum ozone depletion period considered (Sept. 15 to Oct. 15)
Other months also considered (Sept., Oct.) for comparison
Proxy of ozone trend for maximum ozone depletion period: linear (1st period ), plateau (O3loss saturation ) and linear (2nd period )
Baroclinicity of the vortex considered. Two classifications of TOC values inside the vortex as a function of Equivalent Latitude (EL) using Nash et al. (1996) criterion
Standard: single isentropic level
(475K or 550K)
New: range of isentropic levels between
400K and 600K with a step of 25K
Ozone
SAOZ UV-Vis spectrometers
Dumont d’Urville (66.7°S, 140°E),
Concordia (75.1°S, 123.3°E),
TOMS/OMI satellite data, and SBUV in 1995
Vortex position determined using:
MIMOSA model (Hauchecorne et al., 2002)
forced by ERAinterim data
Equivalent Latitude/isentropic level coordinates 1
“Classical” proxies (deLaat et al., 2013)
Annual value calculated for the same period as TOC except for HF (Aug-Sept mean)
“New” proxy
Mean value of maximum PV gradient at 550K to take into account vortex stability
- 550K isentropic level representative of
the evolution of maximum depletion
- Mean value calculated in the studied period
- detrending was applied to avoid interferences
with final O3 trend
MERRA 45-day VT
45°S - 75°S, 70hPa
detrended serie
COMPARISON OF OZONE DATA SETS
Good agreement between SAOZ and TOMS/OMIT for 15 Sept - 15 Oct period et DDU and Concordia
QBO at 30 and 10hPa from Berlin University
Monthly mean bias (TOMS/OMIT – SAOZ)
TRENDS
AAO from NCEP/NOAA
Sept.
Oct
15 Sept – 15 Oct
DDU
-3.0±3.3%
1.8±5.4%
-0.1±2.6%
Concordia
-3.6±3.7%
1.5±3.5%
0.3±5.1%
Influence of vortex barocliniticty not observed (differences in trends between 2 classification criteria not significant at 2)
Solar Flux at 10.7 cm wavelength from NRCAN
15 Sept – 15 Oct period
TOC evolution from SAOZ and OMIT compared to passive ozone tracer of CTM model REPROBUS (Lèfevre et al., 1994)
- Agreement in daily variability between SAOZ and satellite
- Similar O3loss (O3 passive tracer – O3 measurements)
- Ozone evolution well reproduced by model
stratospheric AOD at 550nm from NASA/GISS
Dumont d’Urville
Concordia
2015
General behavior of interannual variability is well captured
Good agreement before and after the “plateau” period ( )
Worse correlation between measurements and model if a “plateau” in not added to the proxy of O3 trend
Last 5 years well simulated by the model only if “gradient” proxy is considered
Important influence on interannual variability of dynamical proxies
In 2015: record of ozone hole size in October
Good agreement for stable winters (ex. 2006, largest O3 hole) and perturbed winters (ex. 2002, major SSW)
VORTEX BAROCLINICITY
Vortex position at different isentropic levels in the maximum O3 depletion altitude range
CONCLUSIONS
Insignificant impact of vortex baroclinicity in O3loss and O3 trends estimation
O3 variability best explained in the maximum O3 depletion period (15Sept-15Oct) by the chosen proxies for period compared to Sept and Oct
Higher contribution to ozone interannual variability of Heat Flux and Gradient (vortex stability)
Positive trend observed in September, October and 15 Sept – 15 Oct for period. Only significant trend at 2 in September.
Contribution of proxies to interannual variability
Dominant influence of
Heat Flux (~27DU) and
Gradient (~18DU)
AAO, Aerosols and Solar Flux contribution <5DU in absolute value
Increase of vortex baroclinicity in October due to higher dynamical activity
Impact on TOC?
Comparison with other months
Interannual O3 variability of 15 Sept - 15 Oct period for different classifications inside the vortex
Sept
Oct
15 Sept – 15 Oct
Trend 1st period (DU/yr) K
475K
-5.7±0.8
-5.3±1.0
-7.1±1.0
-6.8±1.1
-8.2±0.9
-7.7±1.0
plateau No
Yes
Trend (DU/yr)
2.5±1.9
2.7±2.2
1.4±1.9
1.7±2.1
1.1±1.6
1.3±1.9 R2
0.91
0.87
0.93
0.95
0.94
STD of residual (DU)
11.2
12.9
9.3
8.3
9.7
Lowest ozone values for
K classification
Significant difference at 2 (standard error) between different classifications
REFERENCES
de Laat et al., Tracing the second stage of ozone recovery in the Antarctic ozone-hole with a “big data” approach to multivariate regressions, Atmos. Chem. Phys., 15, 79–97, 2015, doi: /acp
Goutail, et al., Total Ozone depletion in the Arctic during the winters of 1993–94 and 1994–95, J. Atmos. Chem., 32, 1–34, 1999.
Hauchecorne et al., Quantification of the transport of chemical constituents from the polar vortex to midlatitudes in the lower stratosphere using the high-resolution advection model MIMOSA and effective diffusivity, J. Geophys. Res., 107, 8289, doi: /2001JD000491, 2002.
Kuttippurath et al., Antarctic ozone loss in 1979–2010: first sign of ozone recovery, Atmos. Chem. Phys., 13, doi: /acp , , 2013.
Lefèvre et al., Chemistry of the 1991–92 stratospheric winter: three dimensional model simulations, J. Geophys. Res., 99, 8183–8195, 1994.
Nash et al., An objective determination of the polar vortex using Ertel’s potential vorticity, J. Geophys. Res., 101, 9471–9478,
Solomon et al., Emergence of healing in the Antarctic ozone layer, Science , /science.aae0061, 2016
WMO (World Meteorological Organization), Scientific Assessment of Ozone Depletion: 2014, Global Ozone Research and Monitoring Project – Report No. 55, 416 pp., Geneva, Switzerland, 2014.
… and what about the impact in O3loss ?
O3loss=O3passive tracer – O3satellite
calculated at different stations (Goutail et al., 1999)
More than 90% of interannual variability explained by proxies used in this study
Better determination coefficient in the 15S-15O period with lowest residual standard deviation
Trend in period 1: best estimation of the trend (-8DU/yr) when O3loss saturation considered. Lowest absolute value in September. Consistent with previous studies (Kuttipurath et al., 2013, deLaat et al., 2015)
Trend in period 2: not significant at two standard error except in September (consistent with Solomon et al., 2016)
50%
Highest O3loss for
K classification
But insignificant difference at 2 with other classifications
Weak increase of O3loss in 2014 and 2015
ACKNOWLEDGEMENTS
The authors thank SAOZ operators in stations as well as agencies supporting NDACC activities: INSU/CNRS, CNES, IPEV.
The authors thank gratefully the French « ESPRI Data Center » (former ETHER) for providing re-analysis data (ERA-Interim)
The authors are also thankful to NASA for satellite data (TOMS/OMI and SBUV)
This work was supported by the DYNOZPOL/LEFE project.