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N Butchart,
A J Charlton‐perez,
I Cionni,
S C Hardiman,
P H Haynes,
K Krüger,
P J Kushner,
P A Newman,
S M Osprey,
J Perlwitz, [......],
J Pyle,
E Rozanov,
J Scinocca,
T G Shepherd,
K Shibata,
D Smale,
H Teyssèdre,
W Tian,
D Waugh,
Y Yamashita
[show abstract]
[hide abstract]
ABSTRACT: 1] The stratospheric climate and variability from simulations of sixteen chemistry‐ climate models is evaluated. On average the polar night jet is well reproduced though its variability is less well reproduced with a large spread between models. Polar temperature biases are less than 5 K except in the Southern Hemisphere (SH) lower stratosphere in spring. The accumulated area of low temperatures responsible for polar stratospheric cloud formation is accurately reproduced for the Antarctic but underestimated for the Arctic. The shape and position of the polar vortex is well simulated, as is the tropical upwelling in the lower stratosphere. There is a wide model spread in the frequency of major sudden stratospheric warnings (SSWs), late biases in the breakup of the SH vortex, and a weak annual cycle in the zonal wind in the tropical upper stratosphere. Quantitatively, "metrics" indicate a wide spread in model performance for most diagnostics with systematic biases in many, and poorer performance in the SH than in the Northern Hemisphere (NH). Correlations were found in the SH between errors in the final warming, polar temperatures, the leading mode of variability, and jet strength, and in the NH between errors in polar temperatures, frequency of major SSWs, and jet strength. Models with a stronger QBO have stronger tropical upwelling and a colder NH vortex. Both the qualitative and quantitative analysis indicate a number of common and long‐standing model problems, particularly related to the simulation of the SH and stratospheric variability.
J. Geophys. Res. 01/2011; 116.
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O Morgenstern,
H Akiyoshi,
S Bekki,
P Braesicke,
N Butchart,
M P Chipperfield,
D Cugnet,
M Deushi,
S S Dhomse,
R R Garcia, [......],
E Rozanov,
D Saint‐martin,
J F Scinocca,
K Shibata,
M Sigmond,
D Smale,
H Teyssèdre,
W Tian,
A Voldoire,
Y Yamashita
[show abstract]
[hide abstract]
ABSTRACT: 1] We address the question of how ozone and long‐lived greenhouse gas changes impact the Northern Annular Mode (NAM). Using reanalyses and results from the Chemistry‐Climate Model Validation 2 (CCMVal‐2) initiative, we calculate seasonal NAM indices from geopotential height for winter and spring. From these, we determine the strength of stratosphere‐troposphere coupling in the model simulations and the reanalyses. For both seasons, we find a large spread in the ability of models to represent the vertical coherence of the NAM, although most models are within the 95% confidence interval. In winter, many models underestimate the vertical coherence derived from the reanalyses. Some models exhibit substantial differences in vertical coherence between simulations driven with modeled and observed ocean conditions. In spring, in the simulations using modeled ocean conditions, models with poorer horizontal or vertical resolution tend to underestimate the vertical coupling, and vice versa for models with better resolution. Accounting for model deficits in producing an appropriate troposphere‐stratosphere coupling, we show significant correlations of the NAM in winter with three indices representing the anthropogenic impact. Analysis of cross‐correlations between these indices suggests that increasing CO 2 is the main reason for these correlations in this season. In the CCMVal‐2 simulations, CO 2 increases are associated with a weakening of the NAM in winter. For spring, we show that the dominant effect is chemical ozone depletion leading to a transient strengthening of the NAM, with CO 2 changes playing an insignificant role.
J. Geophys. Res. 01/2010; 115:0-3.
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[show abstract]
[hide abstract]
ABSTRACT: The purpose of the present study is to evaluate the present-day
climatology in the stratosphere from the new coupled chemistry-climate
model CNRM-ACM. This Chemical Climate Model (CCM) is composed of the
General Circulation Model (GCM) ARPEGE Climat and the Chemical Transport
Model (CTM) MOCAGE-Climat, both developed at Météo-France.
This objective is achieved by comparing experiments from CTM forced by
ECMWF reanalyses or by GCM outputs, and from the coupled CCM. The
meteorological and chemical fields generated by our models are also
compared with the data obtained from different models (results of the
CCM Validation activity of the SPARC program) and from observational
products (such as ERA-40 reanalyses, spatial instrument HALOE and the
NIWA database). Results reveal that the CNRM-ACM model well reproduced
the mean recent stratosphere for dynamics and for chemical species, i.e.
methane, water vapour, HCl and ozone. However, the temperature and the
mean age of air are too low in our model.
03/2009; 11:2152.
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[show abstract]
[hide abstract]
ABSTRACT: The multi-scale CTM MOCAGE has been applied to study pollution episodes
documented during the ESCOMPTE field campain in June July 2001 in south
eastern France (http://medias.obs-mip.fr/escompte). Several sensitivity
studies have been performed on the basis of the 2nd IOP, covering 6
continuous days. The main objective of the present work is to
investigate the question of chemical boundary conditions, as on the
vertical than on the horizontal, for regional air quality simulations of
several days. This issue, that often tended to be oversimplified (use of
fixed continental climatology), raises increasing interest,
particurlarly with the perspective of space-born tropospheric chemisry
data assimilation in global model. In addition, we have examined how
resolution refinements impact on the quality of the model outputs, at
the surface and in altitude, against the observational database of
dynamic and chemistry : resolution of the model by the way of the four
nested models (from 2° to 0.01°), but also resolution of
emission inventories (from 1° to 0.01°). Lastly, the impact of
the refinement in the representation of chemistry has been assessed by
using either detailed chemical schemes, such as RAM or SAPRC, or schemes
used in global modelling, which just account for a limited amount of
volatil hydrocarbon.
03/2003; -1:6141.
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[show abstract]
[hide abstract]
ABSTRACT: Surface exchanges considered in the MOCAGE multiscale Chemistry and
Transport Model (CTM) of Météo-France include dry
deposition of gaseous species. To compute realistic time-dependent
fluxes at the surface, a 2D interface between MOCAGE and ARPEGE, the
French operational numerical weather prediction model, has been
developed. Dry deposition of species including ozone, sulfur dioxide,
nitrogen-containing compounds, long-lived and short-lived intermediates
organic compounds, have been parameterised according to the [Wesely,
1989] scheme. A number of modifications has been made, for instance
concerning the deposition against wet surfaces. The formulation of the
aerodynamic resistance follows [Louis, 1979], and that of the stomatal
resistance, the Interaction Soil Biosphere Atmosphere (ISBA)
Météo-France scheme. Resistances are computed using the
surface meteorological fields obtained from the analyses or forecasts of
ARPEGE. Vegetation fields such as the Leaf Area Index are prescribed
with a one-degree spatial resolution at the global scale, and a
five-minute resolution over Europe. Calculated dry deposition velocities
of ozone, sulfur dioxide and nitric acid have been evaluated against
field experimental data at various locations around the world, from
tropical regions, rain forest or savannah over Central Africa and
Amazonia (EXPRESSO and LBA campaigns), to Mediterranean regions,
including forested and crop sites (ESCOMPTE campaign), and temperate
areas (deciduous and evergreen forests). Hourly values, monthly and
seasonal means have been examined, as well as the impact of the model
resolution, from 2 degrees over the globe to 0.08 degrees over regional
domains. The contributions to the global budget of ozone of the
deposition fluxes in these different regions of the globe will be also
presented.
03/2003; -1:8526.
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[show abstract]
[hide abstract]
ABSTRACT: Dry deposition velocity of particles has been parameterized in the global multi-scale Chemistry and Transport Model MOCAGE as a function of particle size and density, surface properties, and micro-meteorological conditions near the surface. Hourly deposition velocities have been simulated over the year 2000 using the analyses and forecasts of the French operational numerical weather prediction model ARPEGE. Results were compared with measurements available in the literature. Predictions of our model are generally satisfactory, showing the largest uncertainty in the 0.1– particle size interval over highly rough surfaces. According to the one-year global average, deposition velocity over continents is about an order of magnitude higher than over oceans, for all particle sizes. Seasonal variations are nearly undetectable, while diurnal variations over land exist with a maximum around 12– local solar time. Spatially, mid-latitudes regions usually have higher deposition velocities than tropical and polar ones, particularly over continents.
Atmospheric Environment.
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[show abstract]
[hide abstract]
ABSTRACT: Measurements of the dry deposition velocity of ozone have been made by the eddy correlation method during ESCOMPTE (Etude sur Site pour COntraindre les Modèles de Pollution atmosphérique et de Transport d'Emissions). The strong local variability of natural ecosystems was sampled over several weeks in May, June and July 2001 for four sites with varying surface characteristics. The sites included a maize field, a Mediterranean forest, a Mediterranean shrub-land, and an almost bare soil. Measurements of nitrogen oxide deposition fluxes by the relaxed eddy correlation method have also been carried out at the same bare soil site. An evaluation of the deposition velocities computed by the surface module of the multi-scale Chemistry and Transport Model MOCAGE is presented. This module relies on a resistance approach, with a detailed treatment of the stomatal contribution to the surface resistance. Simulations at the finest model horizontal resolution (around 10 km) are compared to observations. If the seasonal variations are in agreement with the literature, comparisons between raw model outputs and observations, at the different measurement sites and for the specific observing periods, are contrasted. As the simulated meteorology at the scale of 10 km nicely captures the observed situations, the default set of surface characteristics (averaged at the resolution of a grid cell) appears to be one of the main reasons for the discrepancies found with observations. For each case, sensitivity studies have been performed in order to see the impact of adjusting the surface characteristics to the observed ones, when available. Generally, a correct agreement with the observations of deposition velocities is obtained. This advocates for a sub-grid scale representation of surface characteristics for the simulation of dry deposition velocities over such a complex area. Two other aspects appear in the discussion. Firstly, the strong influence of the soil water content to the plant response, specifically in conditions of stress, is confirmed. Second, we point out the difficulty in interpreting measurements of nitrogen oxide deposition velocities: a synergetic approach combining measurements and modeling is practical.
Atmospheric Research.
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S.-W. Son,
E. P. Gerber,
J. Perlwitz,
L. M. Polvani,
N. P. Gillett,
K.-H. Seo,
V. Eyring,
T. G. Shepherd,
D. Waugh,
H Akiyoshi, [......],
G. Pitari,
D. A. Plummer,
J. Pyle,
E. Rozanov,
J. F. Scinocca,
K Shibata,
D. Smale,
H. Teyssedre,
W Tian,
Y Yamashita
Journal of Geophysical Research D: Atmospheres.
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A. Gettelman,
M. I. Hegglin,
S.-W. Son,
J. Kim,
M Fujiwara,
T. Birner,
S. Kremser,
M. Rex,
J. A. Anel,
H Akiyoshi, [......],
G. Pitari,
D. A. Plummer,
J. A. Pyle,
E. Rozanov,
J. Scinocca,
T. G. Shepherd,
K Shibata,
D. Smale,
H. Teyssedre,
W Tian
[show abstract]
[hide abstract]
ABSTRACT: The performance of 18 coupled Chemistry Climate Models (CCMs) in the Tropical Tropopause Layer (TTL) is evaluated using qualitative and quantitative diagnostics. Trends in tropopause quantities in the tropics and the extratropical Upper Troposphere and Lower Stratosphere (UTLS) are analyzed. A quantitative grading methodology for evaluating CCMs is extended to include variability and used to develop four different grades for tropical tropopause temperature and pressure, water vapor and ozone. Four of the 18 models and the multi‐model mean meet quantitative and qualitative standards for reproducing key processes in the TTL. Several diagnostics are performed on a subset of the models analyzing the Tropopause Inversion Layer (TIL), Lagrangian cold point and TTL transit time. Historical decreases in tropical tropopause pressure and decreases in water vapor are simulated, lending confidence to future projections. The models simulate continued decreases in tropopause pressure in the 21st century, along with ∼1K increases per century in cold point tropopause temperature and 0.5–1 ppmv per century increases in water vapor above the tropical tropopause. TTL water vapor increases below the cold point. In two models, these trends are associated with 35% increases in TTL cloud fraction. These changes indicate significant perturbations to TTL processes, specifically to deep convective heating and humidity transport. Ozone in the extratropical lowermost stratosphere has significant and hemispheric asymmetric trends. O3 is projected to increase by nearly 30% due to ozone recovery in the Southern Hemisphere (SH) and due to enhancements in the stratospheric circulation. These UTLS ozone trends may have significant effects in the TTL and the troposphere.
Journal of Geophysical Research D: Atmospheres.
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L. D. Oman,
D. A. Plummer,
D. W. Waugh,
J. Austin,
J. F. Scinocca,
A. R. Douglass,
R. J. Salawitch,
T. Canty,
H Akiyoshi,
Slimane Bekki, [......],
G. Pitari,
J. Pyle,
E. Rozanov,
T. G. Shepherd,
K Shibata,
R. S. Stolarski,
H. Teyssedre,
W Tian,
Y Yamashita,
J. R. Ziemke
Journal of Geophysical Research D: Atmospheres.
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M. I. Hegglin,
A. Gettelman,
P. Hoor,
R. Krichevsky,
G. L. Manney,
L. L. Pan,
S.-W. Son,
G. Stiller,
S. Tilmes,
K. A. Walker, [......],
G. Pitari,
D. A. Plummer,
J. A. Pyle,
E. Rozanov,
J. F. Scinocca,
K Shibata,
D. Smale,
H. Teyssedre,
W Tian,
Y Yamashita
[show abstract]
[hide abstract]
ABSTRACT: A multimodel assessment of the performance of chemistry-climate models (CCMs) in the extratropical upper troposphere/lower stratosphere (UTLS) is conducted for the first time. Process-oriented diagnostics are used to validate dynamical and transport characteristics of 18 CCMs using meteorological analyses and aircraft and satellite observations. The main dynamical and chemical climatological characteristics of the extratropical UTLS are generally well represented by the models, despite the limited horizontal and vertical resolution. The seasonal cycle of lowermost stratospheric mass is realistic, however with a wide spread in its mean value. A tropopause inversion layer is present in most models, although the maximum in static stability is located too high above the tropopause and is somewhat too weak, as expected from limited model resolution. Similar comments apply to the extratropical tropopause transition layer. The seasonality in lower stratospheric chemical tracers is consistent with the seasonality in the Brewer-Dobson circulation. Both vertical and meridional tracer gradients are of similar strength to those found in observations. Models that perform less well tend to use a semi-Lagrangian transport scheme and/or have a very low resolution. Two models, and the multimodel mean, score consistently well on all diagnostics, while seven other models score well on all diagnostics except the seasonal cycle of water vapor. Only four of the models are consistently below average. The lack of tropospheric chemistry in most models limits their evaluation in the upper troposphere. Finally, the UTLS is relatively sparsely sampled by observations, limiting our ability to quantitatively evaluate many aspects of model performance.
Journal of Geophysical Research D: Atmospheres.
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J. Austin,
H. Struthers,
J. Scinocca,
D. A. Plummer,
H Akiyoshi,
A. J. G. Baumgaertner,
S. Bekki,
G. E. Bodeker,
P. Braesicke,
C. Brühl, [......],
T Nakamura,
J. E. Nielsen,
G. Pitari,
J. Pyle,
E. Rozanov,
T. G. Shepherd,
K Shibata,
D. Smale,
H. Teyssèdre,
Y Yamashita
Journal of Geophysical Research-Atmospheres, v.115 (2010).
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A. Gettelman,
M. I. Hegglin,
S.-W. Son,
J. Kim,
M Fujiwara,
T. Birner,
S. Kremser,
M. Rex,
J. A. Anel,
H Akiyoshi, [......],
G. Pitari,
D. Plummer,
J. A. Pyle,
E. Rozanov,
J. Scinocca,
T. G. Shepherd,
K Shibata,
D. Smale,
H. Teyssèdre,
W Tian
Journal of Geophysical Research-Atmospheres, v.115 (2010).
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M. I. Hegglin,
A. Gettelman,
P. Hoor,
R. Krichevsky,
G. L. Manney,
L. L. Pan,
S.-W. Son,
G. Stiller,
S. Tilmes,
K. A. Walker, [......],
G. Pitari,
D. A. Plummer,
J. A. Pyle,
E. Rozanov,
J. F. Scinocca,
K Shibata,
D. Smale,
H. Teyssèdre,
W Tian,
Y Yamashita
Journal of Geophysical Research-Atmospheres, v.115 (2010).
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S.-W. Son,
E. P. Gerber,
J. Perlwitz,
L. M. Polvani,
N. P. Gillett,
K.-H. Seo,
V. Eyring,
T. G. Shepherd,
D. Waugh,
H Akiyoshi, [......],
G. Pitari,
D. A. Plummer,
J. Pyle,
E. Rozanov,
J. F. Scinocca,
K Shibata,
D. Smale,
H. Teyssédre,
W Tian,
Y Yamashita
Journal of Geophysical Research-Atmospheres, v.115 (2010).
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A. F. Bais,
K. Tourpali,
A. Kazantzidis,
H Akiyoshi,
Slimane Bekki,
P. Braesicke,
M. P. Chipperfield,
M. Dameris,
V. Eyring,
H. Garny, [......],
O. Morgenstern,
T Nakamura,
P. A. Newman,
G. Pitari,
D. A. Plummer,
E. Rozanov,
T. G. Shepherd,
K Shibata,
W Tian,
Y Yamashita
[show abstract]
[hide abstract]
ABSTRACT: Surface erythemal solar irradiance (UV-Ery) from 1960 to 2100 has been derived using radiative transfer calculations and projections of ozone, temperature and cloud change from 14 chemistry climate models (CCM), as part of the CCMVal-2 activity of SPARC. Our calculations show the influence of ozone depletion and recovery on erythemal irradiance. In addition, we investigate UV-Ery changes caused by climate changes due to increasing greenhouse gas concentrations. The latter include effects on both stratospheric ozone and cloud changes. The derived estimates provide a global picture of the likely changes in erythemal irradiance during the 21st century. Uncertainties arise from the assumed scenarios, different parameterizations - particularly of cloud effects on UV-Ery - and from the diversity in the CCM projections. The calculations suggest that relative to 1980 annually mean UV-Ery in the 2090s will be on average ~12% lower at high latitudes in both hemispheres, ~3% lower at mid latitudes, and marginally higher (~1%) in the tropics. The largest reduction (~16%) is projected for Antarctica in October. Cloud effects result in additional 2-3% reduction in UV-Ery at high latitudes, but they slightly moderate it at mid-latitudes (~1%). The year of return of erythemal irradiance to values of certain milestones (1965 and 1980) depends largely on the return of column ozone to the corresponding levels and is associated with large uncertainties mainly due to the spread of the model projections. The inclusion of cloud effects in the calculations has only a small effect of the return years. At mid and high latitudes, changes in clouds and stratospheric ozone dynamics due to greenhouse gases will sustain the erythemal irradiance at levels below those in 1965, despite the removal of ozone depleting substances. At high northern latitudes, the projected decreases in cloud transmittance towards the end of the 21st century will likely reduce the yearly average surface erythemal irradiance by up to 10% with respect to the 1960s.
Atmospheric Chemistry and Physics Discussions.
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N. Bousserez,
J. L. Attié,
V. H. Peuch, M. Michou,
G. Pfister,
D. Edwards,
L. Emmons,
C. Mari,
B. Barret,
S. R. Arnold,
A. Heckel,
A. Richter,
H. Schlager,
A. Lewis,
M. Avery,
E. V. Browell,
J. W. Hair
[show abstract]
[hide abstract]
ABSTRACT: Intercontinental Transport of Ozone and Precursors (ITOP), part of International Consortium for Atmospheric Research on Transport and Transformation (ICARTT), was a large experimental campaign designed to improve our understanding of the chemical transformations within plumes during long-range transport (LRT) of pollution from North America to Europe. This campaign took place in July and August 2004, when a strong fire season occurred in North America. Burning by-products were transported over large distances, sometimes reaching Europe. A chemical transport model, Modélisation de la Chimie Atmosphérique Grande Echelle (MOCAGE), with a high grid resolution (0.5 x 0.5) over the North Atlantic area and a daily inventory of biomass burning emissions over the United States, has been used to simulate the period. By comparing our results with available aircraft in situ measurements and satellite data (MOPITT CO and SCIAMACHY NO2), we show that MOCAGE is capable of representing the main characteristics of the tropospheric ozone-NOx-hydrocarbon chemistry during the ITOP experiment. In particular, high resolution allows the accurate representation of the pathway of exported pollution over the Atlantic, where plumes were transported preferentially at 6 km altitude. The model overestimates OH mixing ratios up to a factor of 2 in the lower troposphere, which results in a global overestimation of hydrocarbons oxidation by-products (PAN and ketones) and an excess of O3 (30–50 ppbv) in the planetary boundary layer (PBL) over the continental United States. Sensitivity study revealed that lightning NO emissions contributed significantly to the NOx budget in the upper troposphere of northeast America during the summer 2004.
Journal of Geophysical Research. 112(2007-D10S42):1-18.
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John Austin,
H. Struthers,
J. Scinocca,
D.A. Plummer,
H. Akiyoshi,
A.J.G. Baumgaertner,
S. Bekki,
G.E. Bodeker,
P. Braesicke,
C. Brühl, [......],
T. Nakamura,
J.E. Nielsen,
G. Pitari,
J. Pyle,
E. Rozanov,
T.G. Shepherd,
K. Shibata,
D. Smale,
H. Teyssèdre,
Y. Yamashita
[show abstract]
[hide abstract]
ABSTRACT: Coupled chemistry‐climate model simulations covering the recent past and continuing throughout the 21st century have been completed with a range of different models.
Common forcings are used for the halogen amounts and greenhouse gas concentrations, as expected under the Montreal Protocol (with amendments) and Intergovernmental Panel on Climate Change A1b Scenario. The simulations of the Antarctic ozone hole are compared using commonly used diagnostics: the minimum ozone, the maximum area of
ozone below 220 DU, and the ozone mass deficit below 220 DU. Despite the fact that the processes responsible for ozone depletion are reasonably well understood, a wide range of results is obtained. Comparisons with observations indicate that one of the reasons for the model underprediction in ozone hole area is the tendency for models to underpredict, by up to 35%, the area of low temperatures responsible for polar stratospheric cloud formation. Models also typically have species gradients that are too weak at the edge of the polar vortex, suggesting that there is too much mixing of air across the vortex edge. Other models show a high bias in total column ozone which restricts the size of the ozone hole (defined by a 220 DU threshold). The results of those models which agree best with observations are examined in more detail. For several models the ozone hole does not disappear this century but a small ozone hole of up to three million square kilometers continues to occur in most springs even after 2070.
Journal of Geophysical Research. 115(2010-D00M11):1-21.
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John Austin,
J. Scinocca,
D.A. Plummer,
L. Oman,
D. Waugh,
H. Akiyoshi,
S. Bekki,
P. Braesicke,
N. Butchart,
M.P. Chipperfield, [......],
T. Nakamura,
S. Pawson,
G. Pitari,
J. Pyle,
E. Rozanov,
T.G. Shepherd,
K. Shibata,
H. Teyssèdre,
R.J. Wilson,
Y. Yamashita
[show abstract]
[hide abstract]
ABSTRACT: Simulations of 15 coupled chemistry climate models, for the period 1960–2100, are presented. The models include a detailed stratosphere, as well as including a realistic
representation of the tropospheric climate. The simulations assume a consistent set of changing greenhouse gas concentrations, as well as temporally varying chlorofluorocarbon concentrations in accordance with observations for the past and expectations for the future.
The ozone results are analyzed using a nonparametric additive statistical model.
Comparisons are made with observations for the recent past, and the recovery of ozone, indicated by a return to 1960 and 1980 values, is investigated as a function of latitude.
Although chlorine amounts are simulated to return to 1980 values by about 2050, with only weak latitudinal variations, column ozone amounts recover at different rates due to
the influence of greenhouse gas changes. In the tropics, simulated peak ozone amounts occur by about 2050 and thereafter total ozone column declines. Consequently,
simulated ozone does not recover to values which existed prior to the early 1980s. The results also show a distinct hemispheric asymmetry, with recovery to 1980 values in the Northern Hemisphere extratropics ahead of the chlorine return by about 20 years. In the Southern Hemisphere midlatitudes, ozone is simulated to return to 1980 levels only 10 years ahead of chlorine. In the Antarctic, annually averaged ozone recovers at about the same rate as chlorine in high latitudes and hence does not return to 1960s values
until the last decade of the simulations.
Journal of Geophysical Research. 115(2010-D00M10):1-23.
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L.D. Oman,
D.A. Plummer,
D.W. Waugh,
J. Austin,
J.F. Scinocca,
A.R. Douglass,
R.J. Salawitch,
T. Canty,
H. Akiyoshi,
S. Bekki, [......],
G. Pitari,
J. Pyle,
E. Rozanov,
T.G. Shepherd,
K. Shibata,
R.S. Stolarski,
H. Teyssèdre,
W. Tian,
Y. Yamashita,
J.R. Ziemke
[show abstract]
[hide abstract]
ABSTRACT: The evolution of stratospheric ozone from 1960 to 2100 is examined in simulations from 14 chemistry-climate models, driven by prescribed levels of halogens and greenhouse gases. There is general agreement among the models that total column ozone reached a minimum around year 2000 at all latitudes, projected to be followed by an increase over the first half of the 21st century. In the second half of the 21st century, ozone is projected to continue increasing, level off, or even decrease depending on the latitude. Separation into partial columns above and below 20 hPa reveals that these latitudinal differences are almost completely caused by differences in the model projections of ozone in the lower stratosphere. At all latitudes, upper stratospheric ozone increases throughout the 21st century and is projected to return to 1960 levels well before the end of the century, although there is a spread among models in the dates that ozone returns to specific historical values. We find decreasing halogens and declining upper atmospheric temperatures, driven by increasing greenhouse gases, contribute almost equally to increases in upper stratospheric ozone. In the tropical lower stratosphere, an increase in upwelling causes a steady decrease in ozone through the 21st century, and total column ozone does not return to 1960 levels in most of the models. In contrast, lower stratospheric and total column ozone in middle and high latitudes increases during the 21st century, returning to 1960 levels well before the end of the century in most models.
Journal of Geophysical Research. 115(2010-02-D24306):1-21.
