scholarly journals Persistence and photochemical decay of springtime total ozone anomalies in the Canadian Middle Atmosphere Model

2007 ◽  
Vol 7 (2) ◽  
pp. 485-493 ◽  
Author(s):  
S. Tegtmeier ◽  
T. G. Shepherd
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Total Ozone ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Correlation Coefficients ◽  
Polar Regions ◽  
Vertical Diffusion ◽  
Ozone Loss ◽  
Atmosphere Model

Abstract. The persistence and decay of springtime total ozone anomalies over the entire extratropics (midlatitudes plus polar regions) is analysed using results from the Canadian Middle Atmosphere Model (CMAM), a comprehensive chemistry-climate model. As in the observations, interannual anomalies established through winter and spring persist with very high correlation coefficients (above 0.8) through summer until early autumn, while decaying in amplitude as a result of photochemical relaxation in the quiescent summertime stratosphere. The persistence and decay of the ozone anomalies in CMAM agrees extremely well with observations, even in the southern hemisphere when the model is run without heterogeneous chemistry (in which case there is no ozone hole and the seasonal cycle of ozone is quite different from observations). However in a version of CMAM with strong vertical diffusion, the northern hemisphere anomalies decay far too rapidly compared to observations. This shows that ozone anomaly persistence and decay does not depend on how the springtime anomalies are created or on their magnitude, but reflects the transport and photochemical decay in the model. The seasonality of the long-term trends over the entire extratropics is found to be explained by the persistence of the interannual anomalies, as in the observations, demonstrating that summertime ozone trends reflect winter/spring trends rather than any change in summertime ozone chemistry. However this mechanism fails in the northern hemisphere midlatitudes because of the relatively large impact, compared to observations, of the CMAM polar anomalies. As in the southern hemisphere, the influence of polar ozone loss in CMAM increases the midlatitude summertime loss, leading to a relatively weak seasonal dependence of ozone loss in the Northern Hemisphere compared to the observations.

scholarly journals Persistence and photochemical decay of springtime total ozone anomalies in the Canadian Middle Atmosphere Model

2006 ◽  
Vol 6 (2) ◽  
pp. 3403-3417 ◽  
Author(s):  
S. Tegtmeier ◽  
T. G. Shepherd
Keyword(s):  
Seasonal Cycle ◽  
Total Ozone ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Model Performance ◽  
Correlation Coefficients ◽  
Polar Regions ◽  
External Forcing ◽  
Atmosphere Model ◽  
Very High

Abstract. The persistence and decay of springtime total ozone anomalies over the entire extratropics (midlatitudes plus polar regions) is analysed using results from the Canadian Middle Atmosphere Model (CMAM), a comprehensive chemistry-climate model. As in the observations, interannual anomalies established through winter and spring persist with very high correlation coefficients (above 0.8) through summer until early autumn, while decaying in amplitude as a result of photochemical relaxation in the quiescent summertime stratosphere. The persistence and decay of the ozone anomalies in CMAM agrees extremely well with observations, even in the southern hemisphere when the model is run without heterogeneous chemistry (in which case there is no ozone hole and the seasonal cycle of ozone is quite different from observations), and even in the northern hemisphere where this version of CMAM (run with fixed external forcing) strongly underestimates the observed interannual variability. This shows that ozone anomaly persistence and decay does not depend on how the springtime anomalies are created or on their magnitude, but reflects the transport and photochemical decay in the model. It is thus a robust diagnostic of model performance.

scholarly journals Aircraft pollution: a futuristic view

2007 ◽  
Vol 7 (1) ◽  
pp. 2531-2560 ◽  
Author(s):  
O. A. Søvde ◽  
M. Gauss ◽  
I. S. A. Isaksen ◽  
G. Pitari ◽  
C. Marizy
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Total Ozone ◽  
Transport Processes ◽  
Ozone Production ◽  
Aircraft Emissions ◽  
Total Ozone Column ◽  
Ozone Loss ◽  
Supersonic Aircraft ◽  
Ozone Column

Abstract. Impacts of NOx, H2O and aerosol emissions from a projected 2050 aircraft fleet, provided in the EU project SCENIC, are investigated using the Oslo CTM2, a 3-D chemical transport model including comprehensive chemistry for the stratosphere and the troposphere. The aircraft emission scenarios comprise emissions from subsonic and supersonic aircraft. The increases in NOy due to emissions from the mixed fleet are comparable for subsonic (at 11–12 km) and supersonic (at 18–20 km) aircraft, with annual zonal means of 1.35 ppbv and 0.83 ppbv, respectively. H2O increases are also comparable at these altitudes: 630 and 599 ppbv, respectively. The aircraft emissions increase tropospheric ozone by about 10 ppbv in the Northern Hemisphere due to increased ozone production, mainly because of subsonic aircraft. Supersonic aircraft contribute to a reduction of stratospheric ozone due to increased ozone loss at higher altitudes. In the Northern Hemisphere the reduction is about 39 ppbv, but also in the Southern Hemisphere a 22 ppbv stratospheric decrease is modeled due to transport of supersonic aircraft emissions and ozone depleted air. The total ozone column is increased in lower and Northern mid-latitudes, otherwise the increase of ozone loss contributes to a decrease of the total ozone column. Two exceptions are the Northern Hemispheric spring, where the ozone loss increase is small due to transport processes, and tropical latitudes during summer where the effect of subsonic aircraft is low due to a high tropopause. Aerosol particles emitted by aircraft reduce both aircraft and background NOx, more than counterweighting the effect of NOx and H2O aircraft emissions in the stratosphere. Above about 20 km altitude, the NOx (and thus ozone loss) reduction is large enough to give an increase in ozone due to aircraft emissions. This effect is comparable in the Northern and Southern Hemisphere. At 11–20 km altitude, however, ozone production is reduced due to less NOx. Also ClONO2 is increased at this altitude due to enhanced heterogeneous reactions (lowered HCl), and ClO is increased due to less NOx, further enhancing ozone loss in this region. This results in a 14 ppbv further reduction of ozone. Mainly, this results in an increase of the total ozone column due to a decrease in ozone loss caused by the NOx cycle (at the highest altitudes). At the lowermost latitudes, the reduced loss due to the NOx cycle is small. However, ozone production at lower altitudes is reduced and the loss due to ClO is increased, giving a decrease in the total ozone column. Also, at high latitudes during spring the heterogeneous chemistry is more efficient on PSCs, increasing the ozone loss.

scholarly journals Hemispheric ozone variability indices derived from satellite observations and comparison to a coupled chemistry-climate model

2006 ◽  
Vol 6 (12) ◽  
pp. 5105-5120 ◽  
Author(s):  
T. Erbertseder ◽  
V. Eyring ◽  
M. Bittner ◽  
M. Dameris ◽  
V. Grewe
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Total Ozone ◽  
Planetary Wave ◽  
Climate Model ◽  
Model Simulation ◽  
Wave Activity ◽  
Satellite Observations ◽  
Ozone Hole ◽  
Total Column Ozone

Abstract. Total column ozone is used to trace the dynamics of the lower and middle stratosphere which is governed by planetary waves. In order to analyse the planetary wave activity a Harmonic Analysis is applied to global multi-year total ozone observations from the Total Ozone Monitoring Spectrometer (TOMS). As diagnostic variables we introduce the hemispheric ozone variability indices one and two. They are defined as the hemispheric means of the amplitudes of the zonal waves number one and two, respectively, as traced by the total ozone field. The application of these indices as a simple diagnostic for the evaluation of coupled chemistry-climate models (CCMs) is demonstrated by comparing results of the CCM ECHAM4.L39(DLR)/CHEM (hereafter: E39/C) against satellite observations. It is quantified to what extent a multi-year model simulation of E39/C (representing "2000" climate conditions) is able to reproduce the zonal and hemispheric planetary wave activity derived from TOMS data (1996–2004, Version 8). Compared to the reference observations the hemispheric ozone variability indices one and two of E39/C are too high in the Northern Hemisphere and too low in the Southern Hemisphere. In the Northern Hemisphere, where the agreement is generally better, E39/C produces too strong a planetary wave one activity in winter and spring and too high an interannual variability. For the Southern Hemisphere we reveal that the indices from observations and model differ significantly during the ozone hole season. The indices are used to give reasons for the late formation of the Antarctic ozone hole, the insufficient vortex elongation and eventually the delayed final warming in E39/C. In general, the hemispheric ozone variability indices can be regarded as a simple and robust diagnostic to quantify model-observation differences concerning planetary wave activity. It allows a first-guess on how the dynamics is represented in a model simulation before applying costly and more specific diagnostics.

scholarly journals Ultraviolet Radiation modelling using output from the Chemistry Climate Model Initiative

2018 ◽  
Author(s):  
Kévin Lamy ◽  
Thierry Portafaix ◽  
Béatrice Josse ◽  
Colette Brogniez ◽  
Sophie Godin-Beekmann ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Northern Hemisphere ◽  
Total Ozone ◽  
Climate Model ◽  
Sudden Increase ◽  
Total Ozone Column ◽  
Rcp 8.5 ◽  
Ozone Column

Abstract. We have derived values of the Ultraviolet Index (UVI) at solar noon from the Tropospheric Ultraviolet Model (TUV) driven by ozone, temperature and aerosol fields from the first phase of the Chemistry-Climate Model Initiative (CCMI-1). Since clouds remain one of the largest uncertainties in climate projections, we simulated only clear-sky UVI. We compared the UVI climatologies obtained from CCMI and TUV against present-day climatological values of UVI derived from satellite data (the OMI-Aura OMUVBd product) and ground-based measurements (from the NDACC network). Depending on the region, relative differences between the UVI obtained from CCMI and TUV and ground-based measurements ranged between −4 % and 11 %. We calculated the UVI evolution throughout the 21st century for the four Representative Concentration Pathways (RCPs 2.6, 4.5, 6.0 and 8.5). Compared to 1960s values, we found an average increase in UVI in 2100 (of 2–4 %) in the tropical belt (30° N–30° S). For the mid-latitudes, we observed a 1.8 to 3.4 % increase in the Southern Hemisphere for RCP 2.6, 4.5 and 6.0, and found a 2.3 % decrease in RCP 8.5. Higher UV indices are projected in the Northern Hemisphere except for RCP 8.5. At high latitudes, ozone recovery is well identified and induces a complete return of mean UVI levels to 1960 values for RCP 8.5 in the Southern Hemisphere. In the Northern Hemisphere, UVI levels in 2100 are higher by 0.5 to 5.5 % for RCP 2.6, 4.5 and 6.0 and they are lower by 7.9 % for RCP 8.5. We analysed the impacts of greenhouse gases (GHGs) and ozone-depleting substances (ODSs) on UVI from 1960 by comparing CCMI sensitivity simulations (1960–2100) with fixed GHGs or ODSs at their respective 1960 levels. As expected with ODS fixed at their 1960 levels, there is no large decrease in ozone levels and consequently no sudden increase in UVI levels. With fixed GHG, we observed a delayed return of ozone to 1960 values, the same signal is observed on UVI, and looking at the UVI difference between 2090s values and 1960s values, we found an 8 % increase in the tropical belt during the summer of each hemisphere. Finally, we show that, while in the Southern Hemisphere UVI is mainly driven by total ozone column, in the Northern Hemisphere both total ozone column and aerosol optical depth drive UVI levels, with aerosol optical depth having twice as much influence on UVI as total column does.

scholarly journals Clear-sky ultraviolet radiation modelling using output from the Chemistry Climate Model Initiative

2019 ◽  
Vol 19 (15) ◽  
pp. 10087-10110 ◽  
Author(s):  
Kévin Lamy ◽  
Thierry Portafaix ◽  
Béatrice Josse ◽  
Colette Brogniez ◽  
Sophie Godin-Beekmann ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Northern Hemisphere ◽  
Total Ozone ◽  
Climate Model ◽  
Total Ozone Column ◽  
Clear Sky ◽  
Rcp 8.5 ◽  
Ozone Column

Abstract. We have derived values of the ultraviolet index (UVI) at solar noon using the Tropospheric Ultraviolet Model (TUV) driven by ozone, temperature and aerosol fields from climate simulations of the first phase of the Chemistry-Climate Model Initiative (CCMI-1). Since clouds remain one of the largest uncertainties in climate projections, we simulated only the clear-sky UVI. We compared the modelled UVI climatologies against present-day climatological values of UVI derived from both satellite data (the OMI-Aura OMUVBd product) and ground-based measurements (from the NDACC network). Depending on the region, relative differences between the UVI obtained from CCMI/TUV calculations and the ground-based measurements ranged between −5.9 % and 10.6 %. We then calculated the UVI evolution throughout the 21st century for the four Representative Concentration Pathways (RCPs 2.6, 4.5, 6.0 and 8.5). Compared to 1960s values, we found an average increase in the UVI in 2100 (of 2 %–4 %) in the tropical belt (30∘ N–30∘ S). For the mid-latitudes, we observed a 1.8 % to 3.4 % increase in the Southern Hemisphere for RCPs 2.6, 4.5 and 6.0 and found a 2.3 % decrease in RCP 8.5. Higher increases in UVI are projected in the Northern Hemisphere except for RCP 8.5. At high latitudes, ozone recovery is well identified and induces a complete return of mean UVI levels to 1960 values for RCP 8.5 in the Southern Hemisphere. In the Northern Hemisphere, UVI levels in 2100 are higher by 0.5 % to 5.5 % for RCPs 2.6, 4.5 and 6.0 and they are lower by 7.9 % for RCP 8.5. We analysed the impacts of greenhouse gases (GHGs) and ozone-depleting substances (ODSs) on UVI from 1960 by comparing CCMI sensitivity simulations (1960–2100) with fixed GHGs or ODSs at their respective 1960 levels. As expected with ODS fixed at their 1960 levels, there is no large decrease in ozone levels and consequently no sudden increase in UVI levels. With fixed GHG, we observed a delayed return of ozone to 1960 values, with a corresponding pattern of change observed on UVI, and looking at the UVI difference between 2090s values and 1960s values, we found an 8 % increase in the tropical belt during the summer of each hemisphere. Finally we show that, while in the Southern Hemisphere the UVI is mainly driven by total ozone column, in the Northern Hemisphere both total ozone column and aerosol optical depth drive UVI levels, with aerosol optical depth having twice as much influence on the UVI as total ozone column does.

scholarly journals Summertime stratospheric processes at northern mid-latitudes: comparisons between MANTRA balloon measurements and the Canadian Middle Atmosphere Model

2007 ◽  
Vol 7 (4) ◽  
pp. 11621-11646 ◽  
Author(s):  
S. M. L. Melo ◽  
R. Blatherwick ◽  
J. Davies ◽  
P. Fogal ◽  
J. de Grandpré ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Polar Vortex ◽  
Late Summer ◽  
Atmospheric Nitrogen ◽  
Vertical Diffusion ◽  
Trend Assessment ◽  
Atmosphere Model ◽  
Vertical Diffusion Coefficient ◽  
Self Consistency ◽  
Balloon Measurements

Abstract. In this paper we report on a study conducted using the Middle Atmospheric Nitrogen TRend Assessment (MANTRA) balloon measurements of stratospheric constituents and temperature and the Canadian Middle Atmosphere Model (CMAM) in order to evaluate the ability of the model to reproduce the measured fields and to thereby test our ability to describe mid-latitude summertime stratospheric processes. The MANTRA measurements used here are vertical profiles of ozone, temperature, N2O, CH4, HNO3, and HCl obtained during four campaigns, involving the launch of both ozonesondes and large balloons from Vanscoy, Saskatchewan, Canada (52° N, 107° W). The campaigns were conducted in August and September 1998, 2000, 2002 and 2004. During late summer at mid-latitudes, the stratosphere is close to photochemical control, providing an ideal scenario for the study reported here. From this analysis we found that: (1) reducing the value for the vertical diffusion coefficient in CMAM to a more physically reasonable value results in the model better reproducing the measured profiles of long-lived species; (2) the existence of compact correlations among the constituents, as expected from independent measurements in the literature and from models, confirms the self-consistency of the MANTRA measurements; and (3) the 1998 ozone measurements show a narrow layer of low ozone centered near 25 km that is consistent with fossil debris from the polar vortex, suggesting that localized springtime ozone anomalies can persist through summer, affecting ozone levels at mid-latitudes.

scholarly journals Simple measures of ozone depletion in the polar stratosphere

2008 ◽  
Vol 8 (2) ◽  
pp. 251-264 ◽  
Author(s):  
R. Müller ◽  
J.-U. Grooß ◽  
C. Lemmen ◽  
D. Heinze ◽  
M. Dameris ◽  
...  
Keyword(s):  
Total Ozone ◽  
Climate Model ◽  
The Arctic ◽  
Total Column Ozone ◽  
Ozone Loss ◽  
Break Up ◽  
Column Ozone ◽  
The Impact ◽  
Polar Ozone ◽  
Daily Total

Abstract. We investigate the extent to which quantities that are based on total column ozone are applicable as measures of ozone loss in the polar vortices. Such quantities have been used frequently in ozone assessments by the World Meteorological Organization (WMO) and also to assess the performance of chemistry-climate models. The most commonly considered quantities are March and October mean column ozone poleward of geometric latitude 63° and the spring minimum of daily total ozone minima poleward of a given latitude. Particularly in the Arctic, the former measure is affected by vortex variability and vortex break-up in spring. The minimum of daily total ozone minima poleward of a particular latitude is debatable, insofar as it relies on one single measurement or model grid point. We find that, for Arctic conditions, this minimum value often occurs in air outside the polar vortex, both in the observations and in a chemistry-climate model. Neither of the two measures shows a good correlation with chemical ozone loss in the vortex deduced from observations. We recommend that the minimum of daily minima should no longer be used when comparing polar ozone loss in observations and models. As an alternative to the March and October mean column polar ozone we suggest considering the minimum of daily average total ozone poleward of 63° equivalent latitude in spring (except for winters with an early vortex break-up). Such a definition both obviates relying on one single data point and reduces the impact of year-to-year variability in the Arctic vortex break-up on ozone loss measures. Further, this measure shows a reasonable correlation (r=–0.75) with observed chemical ozone loss. Nonetheless, simple measures of polar ozone loss must be used with caution; if possible, it is preferable to use more sophisticated measures that include additional information to disentangle the impact of transport and chemistry on ozone.

Fish Antifreeze Proteins: Recent Gene Evolution

1986 ◽  
Vol 43 (5) ◽  
pp. 1028-1034 ◽  
Author(s):  
Gary K. Scott ◽  
Garth L. Fletcher ◽  
Peter L. Davies
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Genomic Organization ◽  
Gene Evolution ◽  
Antifreeze Proteins ◽  
Gene Organization ◽  
Ice Formation ◽  
Polar Regions ◽  
Subzero Temperatures ◽  
Combining Evidence

A variety of antifreeze proteins is produced by marine teleosts inhabiting polar regions to ensure protection from internal ice formation at subzero temperatures. Combining evidence from paleoclimatology, teleostian evolution, and studies of antifreeze gene organization, the case is made for Cenozoic cooling as the force driving antifreeze evolution in marine teleosts. The distribution of antifreeze types amongst teleost suborders, families, genera, and species correlates with Cenozoic glaciation in the Southern Hemisphere preceding that in the Northern Hemisphere by approximately 25 million yr. The genomic organization of antifreeze genes suggests recent and extensive amplification, an event compatible with their proposed stress-induced origin. Also, a realignment of the nototheniids with the Gadiformes based on antifreeze protein data is suggested.

scholarly journals Summertime stratospheric processes at northern mid-latitudes: comparisons between MANTRA balloon measurements and the Canadian Middle Atmosphere Model

2008 ◽  
Vol 8 (7) ◽  
pp. 2057-2071 ◽  
Author(s):  
S. M. L. Melo ◽  
R. Blatherwick ◽  
J. Davies ◽  
P. Fogal ◽  
J. de Grandpré ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Chemical Species ◽  
Late Summer ◽  
Vertical Diffusion ◽  
Long Term Trends ◽  
Trend Assessment ◽  
Atmosphere Model ◽  
Vertical Diffusion Coefficient ◽  
Balloon Measurements

Abstract. In this paper we report on a study conducted using the Middle Atmospheric Nitrogen TRend Assessment (MANTRA) balloon measurements of stratospheric constituents and temperature and the Canadian Middle Atmosphere Model (CMAM). Three different kinds of data are used to assess the inter-consistency of the combined dataset: single profiles of long-lived species from MANTRA 1998, sparse climatologies from the ozonesonde measurements during the four MANTRA campaigns and from HALOE satellite measurements, and the CMAM climatology. In doing so, we evaluate the ability of the model to reproduce the measured fields and to thereby test our ability to describe mid-latitude summertime stratospheric processes. The MANTRA campaigns were conducted at Vanscoy, Saskatchewan, Canada (52° N, 107° W) in late August and early September of 1998, 2000, 2002 and 2004. During late summer at mid-latitudes, the stratosphere is close to photochemical control, providing an ideal scenario for the study reported here. From this analysis we find that: (1) reducing the value for the vertical diffusion coefficient in CMAM to a more physically reasonable value results in the model better reproducing the measured profiles of long-lived species; (2) the existence of compact correlations among the constituents, as expected from independent measurements in the literature and from models, confirms the self-consistency of the MANTRA measurements; and (3) the 1998 measurements show structures in the chemical species profiles that can be associated with transport, adding to the growing evidence that the summertime stratosphere can be much more disturbed than anticipated. The mechanisms responsible for such disturbances need to be understood in order to assess the representativeness of the measurements and to isolate long-term trends.

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