scholarly journals The impact of mixing across the polar vortex edge on Match ozone loss estimates

2007 ◽  
Vol 7 (4) ◽  
pp. 11725-11759 ◽  
Author(s):  
J.-U. Grooß ◽  
R. Müller ◽  
P. Konopka ◽  
H.-M. Steinhorst ◽  
A. Engel ◽  
...  
Keyword(s):  
Time Integration ◽  
Polar Vortex ◽  
Lagrangian Model ◽  
Match Method ◽  
Transport Barrier ◽  
Ozone Loss ◽  
The Impact ◽  
Loss Rates

Abstract. The Match method for quantification of polar chemical ozone loss is investigated mainly with respect to the impact of mixing across the vortex edge onto this estimate. We show for the winter 2002/03 that significant mixing across the vortex edge occurred and was accurately modeled by the Chemical Lagrangian Model of the Stratosphere. Observations of inert tracers and ozone in-situ from HAGAR on the Geophysica aircraft and sondes and also remote from MIPAS on ENVISAT were reproduced well. The model even reproduced a small vortex remnant that was isolated until June 2003 and was observed in-situ by a balloon-borne whole air sampler. We use this CLaMS simulation to quantify the impact of cross vortex edge mixing on the results of the Match method. It is shown that a time integration of the determined vortex average ozone loss rates as performed in Match results in larger ozone loss than the polar vortex average ozone loss in CLaMS. Also, the determination of the Match ozone loss rates can be influenced by mixing. This is especially important below 430 K, where ozone outside the vortex is lower than inside and the vortex boundary is not a strong transport barrier. This effect and further sampling effects cause an offset between vortex average ozone loss rates derived from Match and deduced from CLaMS with an even sampling for the entire vortex. Both, the time-integration of ozone loss and the determination of ozone loss rates for Match are evaluated using the winter 2002/03 CLaMS simulation. These impacts can explain the differences between CLaMS and Match column ozone loss. While the investigated effects somewhat reduce the apparent discrepancy in January ozone loss rates, a discrepancy between simulations and Match remains. However, its contribution to the accumulated ozone loss over the winter is not large.

scholarly journals The impact of transport across the polar vortex edge on Match ozone loss estimates

2008 ◽  
Vol 8 (3) ◽  
pp. 565-578 ◽  
Author(s):  
J.-U. Grooß ◽  
R. Müller ◽  
P. Konopka ◽  
H.-M. Steinhorst ◽  
A. Engel ◽  
...  
Keyword(s):  
Time Integration ◽  
Polar Vortex ◽  
Lagrangian Model ◽  
Match Method ◽  
Ozone Loss ◽  
Air Sampler ◽  
The Impact ◽  
Loss Rates

Abstract. The Match method for the quantification of polar chemical ozone loss is investigated mainly with respect to the impact of the transport of air masses across the vortex edge. For the winter 2002/03, we show that significant transport across the vortex edge occurred and was simulated by the Chemical Lagrangian Model of the Stratosphere. In-situ observations of inert tracers and ozone from HAGAR on the Geophysica aircraft and balloon-borne sondes, and remote observations from MIPAS on the ENVISAT satellite were reproduced well by CLaMS. The model even reproduced a small vortex remnant that remained a distinct feature until June 2003 and was also observed in-situ by a balloon-borne whole air sampler. We use this CLaMS simulation to quantify the impact of transport across the vortex edge on ozone loss estimates from the Match method. We show that a time integration of the determined vortex average ozone loss rates, as performed in Match, results in a larger ozone loss than the polar vortex average ozone loss in CLaMS. The determination of the Match ozone loss rates is also influenced by the transport of air across the vortex edge. We use the model to investigate how the sampling of the ozone sondes on which Match is based represents the vortex average ozone loss rate. Both the time integration of ozone loss and the determination of ozone loss rates for Match are evaluated using the winter 2002/2003 CLaMS simulation. These impacts can explain the majority of the differences between CLaMS and Match column ozone loss. While the investigated effects somewhat reduce the apparent discrepancy in January ozone loss rates reported earlier, a distinct discrepancy between simulations and Match remains. However, its contribution to the accumulated ozone loss over the winter is not large.

scholarly journals The impact of mid-latitude intrusions into the polar vortex on ozone loss estimates

2003 ◽  
Vol 3 (2) ◽  
pp. 395-402 ◽  
Author(s):  
J.-U. Grooß ◽  
R. Müller
Keyword(s):  
Large Scale ◽  
Loss Rate ◽  
Polar Vortex ◽  
Control Measures ◽  
Lagrangian Model ◽  
The Arctic ◽  
Match Method ◽  
Ozone Loss ◽  
The Impact ◽  
Loss Rates

Abstract. Current stratospheric chemical model simulations underestimate substantially the large ozone loss rates that are derived for the Arctic from ozone sondes for January of some years. Until now, no explanation for this discrepancy has been found. Here, we examine the influence of intrusions of mid-latitude air into the polar vortex on these ozone loss estimates. This study focuses on the winter 1991/92, because during this winter the discrepancy between simulated and experimentally derived ozone loss rates is reported to be the largest. Also during the considered period the vortex was disturbed by a strong warming event with large-scale intrusions of mid-latitude air into the polar vortex, which is quite unusual for this time of the year. The study is based on simulations performed with the Chemical Lagrangian Model of the Stratosphere (CLaMS). Two methods for determination the ozone loss are investigated, the so-called vortex average approach and the Match method. The simulations for January 1992 show that the intrusions induce a reduction of vortex average ozone mixing ratio corresponding to a systematic offset of the ozone loss rate of about 12 ppb per day. This should be corrected for in the vortex average method. The simulations further suggest, that these intrusions do not cause a significant bias for the Match method due to effective quality control measures in the Match technique.

scholarly journals The impact of mid-latitude intrusions into the polar vortex on ozone loss estimates

2002 ◽  
Vol 2 (6) ◽  
pp. 2489-2506
Author(s):  
J.-U. Grooß ◽  
R. Müller
Keyword(s):  
Loss Rate ◽  
Polar Vortex ◽  
Lagrangian Model ◽  
The Arctic ◽  
Mixing Ratio ◽  
Match Method ◽  
Air Masses ◽  
Model Simulations ◽  
Ozone Loss ◽  
The Impact

Abstract. Current stratospheric chemical model simulations underestimate substantially the large ozone loss rates that are derived for the Arctic from ozone sondes for January of some years. Until now, no explanation for this discrepancy has been found. Here, we examine the influence of intrusions of mid-latitude air into the polar vortex on these ozone loss estimates. This study focuses on the winter 1991/92. It is based on simulations performed with the Chemical Lagrangian Model of the Stratosphere (CLaMS). The simulations for January 1992 show that the intrusions induce a reduction of vortex average ozone mixing ratio corresponding to a systematic offset of the ozone loss rate of about 12 ppb per day. Further, the results of the Match method are influenced by the intrusions, since the intruded air masses are deformed and reach dimensions below the Match radius. From our calculations we deduce a systematic offset of the Match ozone loss rate by about 10 ppb/day, which may explain about 28% of the published discrepancy between Match and box model simulations for the winter 1991/92.

scholarly journals Dynamics and chemistry of vortex remnants in late Arctic spring 1997 and 2000: Simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS)

2003 ◽  
Vol 3 (3) ◽  
pp. 839-849 ◽  
Author(s):  
P. Konopka ◽  
J.-U. Grooß ◽  
S. Bausch ◽  
R. Müller ◽  
D. S. McKenna ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Polar Vortex ◽  
Lagrangian Model ◽  
The Arctic ◽  
Summer Circulation ◽  
Air Masses ◽  
Ozone Loss ◽  
Mixing Ratios ◽  
Photochemical Decomposition ◽  
The Impact

Abstract. High-resolution simulations of the chemical composition of the Arctic stratosphere during late spring 1997 and 2000 were performed with the Chemical Lagrangian Model of the Stratosphere (CLaMS). The simulations were performed for the entire northern hemisphere on two isentropic levels 450 K (~18 km) and 585 K (~24 km). The spatial distribution and the lifetime of the vortex remnants formed after the vortex breakup in May 1997 display different behavior above and below 20 km. Above 20 km, vortex remnants propagate southward (up to 40°N) and are "frozen in'' in the summer circulation without significant mixing. Below 20 km the southward propagation of the remnants is bounded by the subtropical jet. Their lifetime is shorter by a factor of 2 than that above 20 km, owing to significant stirring below this altitude. The behavior of vortex remnants formed in March 2000 is similar but, due to an earlier vortex breakup, dominated during the first 6 weeks after the vortex breakup by westerly winds, even above 20 km. Vortex remnants formed in May 1997 are characterized by large mixing ratios of HCl indicating negligible, halogen-induced ozone loss. In contrast, mid-latitude ozone loss in late boreal spring 2000 is dominated, until mid-April, by halogen-induced ozone destruction within the vortex remnants, and subsequent transport of the ozone-depleted polar air masses (dilution) into the mid-latitudes. By varying the intensity of mixing in CLaMS, the impact of mixing on the formation of ClONO2 and ozone depletion is investigated. We find that the photochemical decomposition of HNO3 and not mixing with NOx-rich mid-latitude air is the main source of NOx within the vortex remnants in March and April 2000. Ozone depletion in the remnants is driven by ClOx photolytically formed from ClONO2. At the end of May 1997, the halogen-induced ozone deficit at 450 K poleward of 30°N amounts to ~12% with ~10% in the polar vortex and ~2% in well-isolated vortex remnants after the vortex breakup.

scholarly journals Linking the uncertainty in simulated arctic ozone losses to modelling of tropical stratospheric water vapour

2018 ◽  
Author(s):  
Laura Thölix ◽  
Alexey Karpechko ◽  
Leif Backman ◽  
Rigel Kivi
Keyword(s):  
Water Vapour ◽  
Climate Models ◽  
Polar Vortex ◽  
The Arctic ◽  
Ozone Loss ◽  
Tropical Tropopause ◽  
Water Vapour Concentration ◽  
Vapour Concentration ◽  
The Impact ◽  
Stratospheric Water Vapour

Abstract. Stratospheric water vapor plays a key role in radiative and chemical processes, it e.g. influences the chemical ozone loss via controlling the polar stratospheric cloud formation in the polar stratosphere. The amount of water entering the stratosphere through the tropical tropopause differs substantially between chemistry-climate models. This is because the present-day models have difficulties in capturing the whole complexity of processes that control the water transport across the tropopause. As a result there are large differences in the stratospheric water vapour between the models. In this study we investigate the sensitivity of simulated Arctic ozone loss to the amount of water, which enters the stratosphere through the tropical tropopause. We used a chemical transport model, FinROSE-CTM, forced by ERA-Interim meteorology. The water vapour concentration in the tropical tropopause was varied between 0.5 and 1.6 times the concentration in ERA-Interim, which is similar to the range seen in chemistry climate models. The water vapour changes in the tropical tropopause led to about 1.5 and 2 ppm more water vapour in the Arctic polar vortex compared to the ERA-Interim, respectively. We found that the impact of water vapour changes on ozone loss in the Arctic polar vortex depend on the meteorological conditions. Polar stratospheric clouds form in the cold conditions within the Arctic vortex, and chlorine activation on their surface lead to ozone loss. If the cold conditions persist long enough (e.g. in 2010/11), the chlorine activation is nearly complete. In this case addition of water vapour to the stratosphere increased the formation of ICE clouds, but did not increase the chlorine activation and ozone destruction significantly. In the warm winter 2012/13 the impact of water vapour concentration on ozone loss was small, because the ozone loss was mainly NOx induced. In intermediately cold conditions, e.g. 2013/14, the effect of added water vapour was more prominent than in the other studied winters. The results show that the simulated water vapour concentration in the tropical tropopause has a significant impact on the Arctic ozone loss and deserves attention in order to improve future projections of ozone layer recovery.

scholarly journals A Match-based approach to the estimation of polar stratospheric ozone loss using Aura Microwave Limb Sounder observations

2015 ◽  
Vol 15 (17) ◽  
pp. 9945-9963 ◽  
Author(s):  
N. J. Livesey ◽  
M. L. Santee ◽  
G. L. Manney
Keyword(s):  
Stratospheric Ozone ◽  
Potential Temperature ◽  
Polar Vortex ◽  
Rate Of Change ◽  
The Arctic ◽  
Air Mass ◽  
Ozone Loss ◽  
Chemical Destruction ◽  
Induced Changes ◽  
The Impact

Abstract. The well-established "Match" approach to quantifying chemical destruction of ozone in the polar lower stratosphere is applied to ozone observations from the Microwave Limb Sounder (MLS) on NASA's Aura spacecraft. Quantification of ozone loss requires distinguishing transport- and chemically induced changes in ozone abundance. This is accomplished in the Match approach by examining cases where trajectories indicate that the same air mass has been observed on multiple occasions. The method was pioneered using ozonesonde observations, for which hundreds of matched ozone observations per winter are typically available. The dense coverage of the MLS measurements, particularly at polar latitudes, allows matches to be made to thousands of observations each day. This study is enabled by recently developed MLS Lagrangian trajectory diagnostic (LTD) support products. Sensitivity studies indicate that the largest influence on the ozone loss estimates are the value of potential vorticity (PV) used to define the edge of the polar vortex (within which matched observations must lie) and the degree to which the PV of an air mass is allowed to vary between matched observations. Applying Match calculations to MLS observations of nitrous oxide, a long-lived tracer whose expected rate of change is negligible on the weekly to monthly timescales considered here, enables quantification of the impact of transport errors on the Match-based ozone loss estimates. Our loss estimates are generally in agreement with previous estimates for selected Arctic winters, though indicating smaller losses than many other studies. Arctic ozone losses are greatest during the 2010/11 winter, as seen in prior studies, with 2.0 ppmv (parts per million by volume) loss estimated at 450 K potential temperature (~ 18 km altitude). As expected, Antarctic winter ozone losses are consistently greater than those for the Arctic, with less interannual variability (e.g., ranging between 2.3 and 3.0 ppmv at 450 K). This study exemplifies the insights into atmospheric processes that can be obtained by applying the Match methodology to a densely sampled observation record such as that from Aura MLS.

scholarly journals Denitrification by large NAT particles: the impact of reduced settling velocities and hints on particle characteristics

2014 ◽  
Vol 14 (20) ◽  
pp. 11525-11544 ◽  
Author(s):  
W. Woiwode ◽  
J.-U. Grooß ◽  
H. Oelhaf ◽  
S. Molleker ◽  
S. Borrmann ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
Spherical Particles ◽  
Lagrangian Model ◽  
The Arctic ◽  
Reference Scenario ◽  
Climate Interactions ◽  
Stratospheric Clouds ◽  
The Impact ◽  
Good Agreement

Abstract. Vertical redistribution of HNO3 through large HNO3-containing particles associated with polar stratospheric clouds (PSCs) plays an important role in the chemistry of the Arctic winter stratosphere. During the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) campaign, apparently very large NAT (nitric acid trihydrate) particles were observed by the airborne in situ probe FSSP-100 (Molleker et al., 2014). Our analysis shows that the FSSP-100 observations associated with the flight on 25 January 2010 cannot easily be explained assuming compact spherical NAT particles due to much too short growing time at temperatures below the existence temperature of NAT (TNAT). State-of-the-art simulations using CLaMS (Chemical Lagrangian Model of the Stratosphere; Grooß et al., 2014) suggest considerably smaller particles. We consider the hypothesis that the simulation reproduces the NAT particle masses in a realistic way, but that real NAT particles may have larger apparent sizes compared to compact spherical particles, e.g. due to non-compact morphology or aspheric shape. Our study focuses on the consequence that such particles would have reduced settling velocities compared to compact spheres, altering the vertical redistribution of HNO3. Utilising CLaMS simulations, we investigate the impact of reduced settling velocities of NAT particles on vertical HNO3 redistribution and compare the results with observations of gas-phase HNO3 by the airborne Fourier transform spectrometer MIPAS-STR associated with two RECONCILE flights. The MIPAS-STR observations confirm conditions consistent with denitrification by NAT particles for the flight on 25 January 2010 and show good agreement with the simulations within the limitations of the comparison. Best agreement is found if settling velocities between 100 and 50% relative to compact spherical particles are considered (slight preference for the 70% scenario). In contrast, relative settling velocities of 30% result in too weak vertical HNO3 redistribution. Sensitivity simulations considering temperature biases of ±1 K and multiplying the simulated nucleation rates by factors of 0.5 and 2.0 affect the comparisons to a similar extent, but result in no effective improvement compared to the reference scenario. Our results show that an accurate knowledge of the settling velocities of NAT particles is important for quantitative simulations of vertical HNO3 redistribution.

scholarly journals Variability in Antarctic ozone loss in the last decade (2004–2013): high-resolution simulations compared to Aura MLS observations

2015 ◽  
Vol 15 (18) ◽  
pp. 10385-10397 ◽  
Author(s):  
J. Kuttippurath ◽  
S. Godin-Beekmann ◽  
F. Lefèvre ◽  
M. L. Santee ◽  
L. Froidevaux ◽  
...  
Keyword(s):  
High Resolution ◽  
High Frequency ◽  
Polar Vortex ◽  
Ozone Loss ◽  
Maximum Loss ◽  
Vertical Range ◽  
Antarctic Ozone ◽  
June July ◽  
The Antarctic ◽  
Loss Rates

Abstract. A detailed analysis of the polar ozone loss processes during 10 recent Antarctic winters is presented with high-resolution MIMOSA–CHIM (Modèle Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection avec CHIMie) model simulations and high-frequency polar vortex observations from the Aura microwave limb sounder (MLS) instrument. The high-frequency measurements and simulations help to characterize the winters and assist the interpretation of interannual variability better than either data or simulations alone. Our model results for the Antarctic winters of 2004–2013 show that chemical ozone loss starts in the edge region of the vortex at equivalent latitudes (EqLs) of 65–67° S in mid-June–July. The loss progresses with time at higher EqLs and intensifies during August–September over the range 400–600 K. The loss peaks in late September–early October, when all EqLs (65–83° S) show a similar loss and the maximum loss (> 2 ppmv – parts per million by volume) is found over a broad vertical range of 475–550 K. In the lower stratosphere, most winters show similar ozone loss and production rates. In general, at 500 K, the loss rates are about 2–3 ppbv sh−1 (parts per billion by volume per sunlit hour) in July and 4–5 ppbv sh−1 in August–mid-September, while they drop rapidly to 0 by mid-October. In the middle stratosphere, the loss rates are about 3–5 ppbv sh−1 in July–August and October at 675 K. On average, the MIMOSA–CHIM simulations show that the very cold winters of 2005 and 2006 exhibit a maximum loss of ~ 3.5 ppmv around 550 K or about 149–173 DU over 350–850 K, and the warmer winters of 2004, 2010, and 2012 show a loss of ~ 2.6 ppmv around 475–500 K or 131–154 DU over 350–850 K. The winters of 2007, 2008, and 2011 were moderately cold, and thus both ozone loss and peak loss altitudes are between these two ranges (3 ppmv around 500 K or 150 ± 10 DU). The modeled ozone loss values are in reasonably good agreement with those estimated from Aura MLS measurements, but the model underestimates the observed ClO, largely due to the slower vertical descent in the model during spring.

Comment on "Cosmic-ray-driven reaction and greenhouse effect of halogenated molecules: Culprits for atmospheric ozone depletion and global climate change"

2014 ◽  
Vol 28 (13) ◽  
pp. 1482001 ◽  
Author(s):  
Rolf Müller ◽  
Jens-Uwe Grooß
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Total Ozone ◽  
Stratospheric Ozone ◽  
Cosmic Ray ◽  
Alternative Mechanism ◽  
Ozone Loss ◽  
Global Sea Level ◽  
The Impact ◽  
Loss Rates

Lu's "cosmic-ray-driven electron-induced reaction (CRE) theory" is based on the assumption that the CRE reaction of halogenated molecules (e.g., chlorofluorocarbons (CFCs), HCl, ClONO2) adsorbed or trapped in polar stratospheric clouds in the winter polar stratosphere is the key step in forming photoactive halogen species that are the cause of the springtime ozone hole. This theory has been extended to a warming theory of halogenated molecules for climate change. In this comment, we discuss the chemical and physical foundations of these theories and the conclusions derived from the theories. First, it is unclear whether the loss rates of halogenated molecules induced by dissociative electron attachment (DEA) observed in the laboratory can also be interpreted as atmospheric loss rates, but even if this were the case, the impact of DEA-induced reactions on polar chlorine activation and ozone loss in the stratosphere is limited. Second, we falsify several conclusions that are reported on the basis of the CRE theory: There is no polar ozone loss in darkness, there is no apparent 11-year periodicity in polar total ozone measurements, the age of air in the polar lower stratosphere is much older than 1–2 years, and the reported detection of a pronounced recovery (by about 20–25%) in Antarctic total ozone measurements by the year 2010 is in error. There are also conclusions about the future development of sea ice and global sea level which are fundamentally flawed because Archimedes' principle is neglected. Many elements of the CRE theory are based solely on correlations between certain datasets which are no substitute for providing physical and chemical mechanisms causing a particular behavior noticeable in observations. In summary, the CRE theory cannot be considered as an independent, alternative mechanism for polar stratospheric ozone loss and the conclusions on recent and future surface temperature and global sea level change do not have a physical basis.

scholarly journals Impact of Lagrangian transport on lower-stratospheric transport timescales in a climate model

2020 ◽  
Vol 20 (23) ◽  
pp. 15227-15245
Author(s):  
Edward J. Charlesworth ◽  
Ann-Kristin Dugstad ◽  
Frauke Fritsch ◽  
Patrick Jöckel ◽  
Felix Plöger
Keyword(s):  
Atmospheric Chemistry ◽  
Large Scale ◽  
Climate Model ◽  
Polar Vortex ◽  
Transport Processes ◽  
Lagrangian Model ◽  
Trace Gas ◽  
Lagrangian Transport ◽  
Transport Barriers ◽  
The Impact

Abstract. We investigate the impact of model trace gas transport schemes on the representation of transport processes in the upper troposphere and lower stratosphere. Towards this end, the Chemical Lagrangian Model of the Stratosphere (CLaMS) was coupled to the ECHAM/MESSy Atmospheric Chemistry (EMAC) model and results from the two transport schemes (Lagrangian critical Lyapunov scheme and flux-form semi-Lagrangian, respectively) were compared. Advection in CLaMS was driven by the EMAC simulation winds, and thereby the only differences in transport between the two sets of results were caused by differences in the transport schemes. To analyze the timescales of large-scale transport, multiple tropical-surface-emitted tracer pulses were performed to calculate age of air spectra, while smaller-scale transport was analyzed via idealized, radioactively decaying tracers emitted in smaller regions (nine grid cells) within the stratosphere. The results show that stratospheric transport barriers are significantly stronger for Lagrangian EMAC-CLaMS transport due to reduced numerical diffusion. In particular, stronger tracer gradients emerge around the polar vortex, at the subtropical jets, and at the edge of the tropical pipe. Inside the polar vortex, the more diffusive EMAC flux-form semi-Lagrangian transport scheme results in a substantially higher amount of air with ages from 0 to 2 years (up to a factor of 5 higher). In the lowermost stratosphere, mean age of air is much smaller in EMAC, owing to stronger diffusive cross-tropopause transport. Conversely, EMAC-CLaMS shows a summertime lowermost stratosphere age inversion – a layer of older air residing below younger air (an “eave”). This pattern is caused by strong poleward transport above the subtropical jet and is entirely blurred by diffusive cross-tropopause transport in EMAC. Potential consequences from the choice of the transport scheme on chemistry–climate and geoengineering simulations are discussed.

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