scholarly journals Seasonal impact of biogenic VSL bromine on the evolution of mid-latitude lowermost stratospheric ozone during the 21<sup>st</sup> century

2020 ◽  
Author(s):  
Javer A. Barrera ◽  
Rafael P. Fernandez ◽  
Fernando Iglesias-Suarez ◽  
Carlos A. Cuevas ◽  
Jean-Francois Lamarque ◽  
...  
Keyword(s):  
21St Century ◽  
Total Ozone ◽  
Stratospheric Ozone ◽  
Polar Regions ◽  
Total Ozone Column ◽  
Seasonal Impact ◽  
The Tropics ◽  
The Impact ◽  
Ozone Column ◽  
Modelling Study

Abstract. Biogenic very short-lived bromine (VSLBr) represents, nowadays, ~ 25 % of the total stratospheric bromine loading. Owing to their much shorter lifetime compared to anthropogenic long-lived bromine (LLBr, e.g., halons) and chlorine (LLCl, e.g., chlorofluorocarbons) substances, the impact of VSLBr on ozone peaks at the extratropical lowermost stratosphere, a key climatic and radiative atmospheric region. Here we present a modelling study of the evolution of stratospheric ozone and its chemical losses in extra-polar regions during the 21st century, under two different scenarios: considering and neglecting the additional stratospheric injection of 5 ppt biogenic VSLBr naturally released from the ocean. Our analysis shows that the inclusion of VSLBr result in a realistic stratospheric bromine loading and improves the quantitative 1980–2015 model-satellite agreement of total ozone column (TOC) in the mid-latitudes. We show that the overall ozone response to VSLBr within the mid-latitudes follows the stratospheric abundances evolution of long-lived inorganic chlorine and bromine throughout the 21st century. Additional ozone losses due to VSLBr are maximised during the present-day period (1990–2010), with TOC differences of −8 DU (−3 %) and −5.5 DU (−2 %) for the southern (SH-ML) and northern (NH-ML) mid-latitudes, respectively. Moreover, the projected TOC differences at the end of the 21st century are at least half of the values found for the present-day period. In the tropics, a small (

Seasonal impact of biogenic very short-lived bromocarbons on lowermost stratospheric ozone between 60◦ N and 60◦ S during the 21st century

2021 ◽  
Author(s):  
Javier Barrera ◽  
Rafael Fernandez ◽  
Fernando Iglesias-Suarez ◽  
Carlos A. Cuevas ◽  
Jean-Francois Lamarque ◽  
...  
Keyword(s):  
21St Century ◽  
Seasonal Changes ◽  
Total Ozone ◽  
Hemispheric Asymmetry ◽  
Stratospheric Ozone ◽  
Ice Crystals ◽  
Seasonal Impact ◽  
The Tropics ◽  
The Impact ◽  
Ozone Column

&lt;p&gt;Biogenic very short-lived bromocarbons (VSLBr) currently represent &amp;#8764;25 % of the total stratospheric bromine loading. Owing to their much shorter lifetime compared to anthropogenic long-lived bromine (e.g. halons) and chlorine (e.g. chlorofluorocarbons), the impact of VSLBr on ozone peaks in the lowermost stratosphere, which is a key climatic and radiative atmospheric region. Here we present a modelling study of the evolution of stratospheric ozone and its chemical loss within the tropics and at mid-latitudes during the 21st century. Two different experiments are explored: considering and neglecting the additional stratospheric injection of 5 ppt biogenic bromine naturally released from the ocean. Our analysis shows that the inclusion of VSLBr results in a realistic stratospheric bromine loading and improves the agreement between the model and satellite observations of the total ozone column (TOC) for the 1980&amp;#8211;2015 period at mid-latitudes. We show that the overall ozone response to VSLBr at mid-latitudes follows the stratospheric evolution of long-lived inorganic chlorine and bromine throughout the 21st century. Moreover, the seasonal VSLBr impact on lowermost stratospheric ozone at mid-latitude is influenced by the seasonality of the heterogeneous inorganic-chlorine reactivation processes on ice crystals. Indeed, due to the more efficient reactivation of chlorine reservoirs (mainly ClONO2 and HCl) within the colder SH-ML lowermost stratosphere, the seasonal VSLBr impact shows a small but persistent hemispheric asymmetry through the whole modelled period. We conclude that the link between biogenic bromine sources and seasonal changes in heterogeneous chlorine reactivation is a key feature for future projections of mid-latitude lowermost stratospheric ozone during the 21st century.&lt;/p&gt;

scholarly journals Seasonal impact of biogenic very short-lived bromocarbons on lowermost stratospheric ozone between 60° N and 60° S during the 21st century

2020 ◽  
Vol 20 (13) ◽  
pp. 8083-8102
Author(s):  
Javier Alejandro Barrera ◽  
Rafael Pedro Fernandez ◽  
Fernando Iglesias-Suarez ◽  
Carlos Alberto Cuevas ◽  
Jean-Francois Lamarque ◽  
...  
Keyword(s):  
21St Century ◽  
Ozone Depletion ◽  
Hemispheric Asymmetry ◽  
Stratospheric Ozone ◽  
Ozone Loss ◽  
Seasonal Impact ◽  
Low Sensitivity ◽  
The Tropics ◽  
The Impact ◽  
Ozone Column

Abstract. Biogenic very short-lived bromocarbons (VSLBr) currently represent ∼25 % of the total stratospheric bromine loading. Owing to their much shorter lifetime compared to anthropogenic long-lived bromine (e.g. halons) and chlorine (e.g. chlorofluorocarbons), the impact of VSLBr on ozone peaks in the lowermost stratosphere, which is a key climatic and radiative atmospheric region. Here we present a modelling study of the evolution of stratospheric ozone and its chemical loss within the tropics and at mid-latitudes during the 21st century. Two different experiments are explored: considering and neglecting the additional stratospheric injection of 5 ppt biogenic bromine naturally released from the ocean. Our analysis shows that the inclusion of VSLBr results in a realistic stratospheric bromine loading and improves the agreement between the model and satellite observations of the total ozone column (TOC) for the 1980–2015 period at mid-latitudes. We show that the overall ozone response to VSLBr at mid-latitudes follows the stratospheric evolution of long-lived inorganic chlorine and bromine throughout the 21st century. Additional ozone loss due to VSLBr is maximized during the present-day period (1990–2010), with TOC differences of −8 DU (−3 %) and −5.5 DU (−2 %) for the Southern Hemisphere and Northern Hemisphere mid-latitudes (SH-MLs and NH-MLs), respectively. Moreover, the projected TOC differences at the end of the 21st century are ∼50 % lower than the values found for the present-day period. We find that seasonal VSLBr impact on lowermost stratospheric ozone at mid-latitude is influenced by the seasonality of the heterogeneous inorganic-chlorine reactivation processes on ice crystals. Indeed, due to the more efficient reactivation of chlorine reservoirs (mainly ClONO2 and HCl) within the colder SH-ML lowermost stratosphere, the seasonal VSLBr impact shows a small but persistent hemispheric asymmetry through the whole modelled period. Our results indicate that, although the overall VSLBr-driven ozone destruction is greatest during spring, the halogen-mediated (Halogx-Loss) ozone loss cycle in the mid-latitude lowermost stratosphere during winter is comparatively more efficient than the HOx cycle with respect to other seasons. Indeed, when VSLBr are considered, Halogx-Loss dominates wintertime lowermost stratospheric ozone loss at SH-MLs between 1985 and 2020, with a contribution of inter-halogen ClOx–BrOx cycles to Halogx-Loss of ∼50 %. Within the tropics, a small (<-2.5 DU) and relatively constant (∼-1 %) ozone depletion mediated by VSLBr is closely related to their fixed emissions throughout the modelled period. By including the VSLBr sources, the seasonal Halogx-Loss contribution to lowermost stratospheric ozone loss is practically dominated by the BrOx cycle, reflecting the low sensitivity of very short-lived (VSL) bromine to background halogen abundances to drive tropical stratospheric ozone depletion. We conclude that the link between biogenic bromine sources and seasonal changes in heterogeneous chlorine reactivation is a key feature for future projections of mid-latitude lowermost stratospheric ozone during the 21st century.

scholarly journals Record low ozone values over the Arctic in boreal spring 2020

2021 ◽  
Vol 21 (2) ◽  
pp. 617-633
Author(s):  
Martin Dameris ◽  
Diego G. Loyola ◽  
Matthias Nützel ◽  
Melanie Coldewey-Egbers ◽  
Christophe Lerot ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Total Ozone ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Ozone Hole ◽  
The Arctic ◽  
Atmospheric Conditions ◽  
Total Ozone Column ◽  
The Antarctic ◽  
Ozone Column

Abstract. Ozone data derived from the Tropospheric Monitoring Instrument (TROPOMI) sensor on board the Sentinel-5 Precursor satellite show exceptionally low total ozone columns in the polar region of the Northern Hemisphere (Arctic) in spring 2020. Minimum total ozone column values around or below 220 Dobson units (DU) were seen over the Arctic for 5 weeks in March and early April 2020. Usually the persistence of such low total ozone column values in spring is only observed in the polar Southern Hemisphere (Antarctic) and not over the Arctic. These record low total ozone columns were caused by a particularly strong polar vortex in the stratosphere with a persistent cold stratosphere at higher latitudes, a prerequisite for ozone depletion through heterogeneous chemistry. Based on the ERA5, which is the fifth generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis, the Northern Hemisphere winter 2019/2020 (from December to March) showed minimum polar cap temperatures consistently below 195 K around 20 km altitude, which enabled enhanced formation of polar stratospheric clouds. The special situation in spring 2020 is compared and discussed in context with two other Northern Hemisphere spring seasons, namely those in 1997 and 2011, which also displayed relatively low total ozone column values. However, during these years, total ozone columns below 220 DU over several consecutive days were not observed in spring. The similarities and differences of the atmospheric conditions of these three events and possible explanations for the observed features are presented and discussed. It becomes apparent that the monthly mean of the minimum total ozone column value for March 2020 (221 DU) was clearly below the respective values found in March 1997 (267 DU) and 2011 (252 DU), which highlights the special evolution of the polar stratospheric ozone layer in the Northern Hemisphere in spring 2020. A comparison with a typical ozone hole over the Antarctic (e.g., in 2016) indicates that although the Arctic spring 2020 situation is remarkable, with total ozone column values around or below 220 DU observed over a considerable area (up to 0.9 million km2), the Antarctic ozone hole shows total ozone columns typically below 150 DU over a much larger area (of the order of 20 million km2). Furthermore, total ozone columns below 220 DU are typically observed over the Antarctic for about 4 months.

scholarly journals Reassessment of causes of ozone column variability following the eruption of Mount Pinatubo using a nudged CCM

2009 ◽  
Vol 9 (2) ◽  
pp. 5423-5446 ◽  
Author(s):  
P. Telford ◽  
P. Braesicke ◽  
O. Morgenstern ◽  
J. Pyle
Keyword(s):  
Total Ozone ◽  
Global Scale ◽  
Heterogeneous Chemistry ◽  
Mount Pinatubo ◽  
Complementary Approach ◽  
The Tropics ◽  
The Impact ◽  
Enhanced Surface ◽  
Ozone Column ◽  
Polar Ozone

Abstract. The eruption of Mount Pinatubo produced the largest loading of stratospheric sulphate aerosol in the twentieth century. This heated the tropical lower stratosphere, affecting stratospheric circulation, and provided enhanced surface area for heterogeneous chemistry. These factors combined to produce record low values of extra-polar total ozone column. Though well studied, there remains some uncertainty about the attribution of this low ozone, with contributions from both chemical and dynamical effects. We take a complementary approach to previous studies, nudging the temperature and horizontal winds in the new UKCA CCM to reproduce the atmospheric response and assess the impact on global total ozone. We then combine model runs and observations to attribute the variability to chemical and dynamical effects. To estimate the effects of increased heterogeneous chemistry we compare runs with volcanically enhanced and background surface aerosol density, noting that this causes depletion of global ozone peaking at about 7 DU in early 1993, in good agreement with observations. We subtract this effect from the observed variability and attribute the remaining variability to dynamical effects. We see that the remaining variability is dominated by the QBO. In addition to global averages we examine tropical and mid-latitude ozone, diagnosing contributions from El Niño in the tropics and some dynamically driven low ozone in northern mid-latitudes, which we see as possible evidence of changes in the QBO. We conclude that, on a global scale, the record lows of extra-polar ozone are produced by the increased heterogeneous chemistry, although there is evidence for dynamics having producing low ozone in certain regions, such as northern mid-latitudes.

scholarly journals Total ozone column from Ozone Mapping and Profiler Suite Nadir Mapper (OMPS-NM) measurements using the broadband weighting function fitting approach (WFFA)

2021 ◽  
Vol 14 (8) ◽  
pp. 5771-5789
Author(s):  
Andrea Orfanoz-Cheuquelaf ◽  
Alexei Rozanov ◽  
Mark Weber ◽  
Carlo Arosio ◽  
Annette Ladstätter-Weißenmayer ◽  
...  
Keyword(s):  
Total Ozone ◽  
Weighting Function ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Polar Regions ◽  
Total Ozone Column ◽  
Function Fitting ◽  
Ozone Column ◽  
Good Agreement ◽  
Column Product

Abstract. A scientific total ozone column product from Ozone Mapping and Profiler Suite Nadir Mapper (OMPS-NM) observations and the retrieval algorithm are presented. The retrieval employs the weighting function fitting approach (WFFA), a modification of the weighting function differential optical absorption spectroscopy (WFDOAS) technique. The total ozone columns retrieved with WFFA are in very good agreement with other datasets. A mean difference of 0.3 % with respect to ground-based Brewer and Dobson measurements is observed. Seasonal and latitudinal variations are well represented and in agreement with other satellite datasets. The comparison of our product with the operational product of OMPS-NM indicates a mean bias of around zero. The comparison with the Tropospheric Monitoring Instrument products (S5P/TROPOMI) OFFL and WFDOAS shows a persistent negative bias of about −0.6 % for OFFL and −2.5 % for WFDOAS. Larger differences are only observed in the polar regions. This data product is intended to be used for trend analysis and the retrieval of tropospheric ozone combined with the OMPS limb profiler data.

scholarly journals The January 2006 low ozone event over the UK

2006 ◽  
Vol 6 (5) ◽  
pp. 8457-8483 ◽  
Author(s):  
M. Keil ◽  
D. R. Jackson ◽  
M. C. Hort
Keyword(s):  
Total Ozone ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
British Isles ◽  
Stratospheric Polar Vortex ◽  
North West ◽  
Total Ozone Column ◽  
Mixing Ratios ◽  
The Uk ◽  
Ozone Column

Abstract. A record low total ozone column of 177 DU was observed at Reading, UK, on 19 January 2006. Low ozone values were also recorded at other stations in the British Isles and North West Europe on, and around, this date. Hemispheric maps of total ozone from the World Meteorological Organisation (WMO) Ozone Mapping Centre also show the evolution of this ozone minimum from 15–20 January 2006 over North West Europe. Ozonesonde measurements made at Lerwick, UK, show that ozone mixing ratios in the mid-stratosphere on 18 January are around 1–2 ppmv lower than both climatology and observations made one and two weeks prior to this date. In addition, ozone mixing ratios in the UTLS region were also noticeably reduced on 18 January. Analysis of the ozonesonde observations indicate that the mid-stratosphere ozone accounts for around a third of the reduction in total ozone column measurements while the UTLS ozone values account for two thirds of the depletion. It is evident from the ozonesonde data that ozone loss is occuring at two distinct vertical regions. Met Office analyses indicate that stratospheric polar vortex temperatures were cold enough for Polar Stratospheric Cloud (PSC) formation during 14 days in January prior to the low ozone event on 19 January. The presence of PSCs is confirmed by observations from the Scanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY). As a consequence of a stratospheric sudden warming that was in progress during January 2006, the polar vortex was shifted southwards over northwest Europe. This includes a period from 16 to 19 January where PSCs were present in the vortex over the UK. Throughout most of January suitable conditions were present for ozone destruction by heterogenous chemistry within the polar vortex. Evidence from Lerwick and Sodankylä ozonesonde profiles, and maps of Ertel's potential vorticity calculated from Met Office analyses, strongly suggests that the air inside the stratospheric vortex was poor in ozone for at least one week prior to 18 January. It is also possible that local chemical destruction of stratospheric ozone further contributed to the record low ozone observed at Reading. A closer examination of the WMO total ozone maps shows that the daily minima are often of synoptic, rather than planetary, scale. This therefore suggests a tropospheric, rather than stratospheric, mechanism for the ozone minima. Moderate total ozone depletion is commonly observed in the northern hemisphere middle and high latitude winter. This depletion is related to the lifting of the tropopause associated with the presence of an upper troposphere/lower stratosphere anticyclone. We show a strong link between the ozone minima in the WMO maps and 100 hPa geopotential height from Met Office analyses, and therefore it appears that this may also be a plausible mechanism for the record low ozone column that is observed. Back trajectories calculated by the Met Office NAME III model show that air parcels in the mid-stratosphere do arrive over the British Isles on 19 January via the polar vortex. The NAME III model results also show that air parcels near the tropopause arrive from low latitudes and are transported anticyclonically. Therefore this strongly suggests that the record low ozone values are due to a combination of a raised tropopause and the presence of low ozone stratospheric air aloft.

scholarly journals Influence of the Change in Total Ozone Column (TOC) on the Occurrence of Tropospheric Ozone Depletion Events (ODEs) in the Antarctic

2021 ◽  
Author(s):  
Le Cao ◽  
Linjie Fan ◽  
Simeng Li ◽  
Shuangyan Yang
Keyword(s):  
Observational Data ◽  
Ozone Depletion ◽  
Tropospheric Ozone ◽  
Total Ozone ◽  
Numerical Models ◽  
Total Ozone Column ◽  
Speed Up ◽  
The Antarctic ◽  
The Impact ◽  
Ozone Column

Abstract. The occurrence of the tropospheric ozone depletion events (ODEs) in the Antarctic can be influenced by the change in Total Ozone Column (TOC). In this study, we combined the observational data obtained from ground observation stations with two numerical models (TUV and KINAL), to figure out the relationship between the TOC change and the occurrence of ODEs in the Antarctic. A sensitivity analysis was also performed on the change in ozone and major bromine species (BrO, HOBr and HBr) to find out key photolysis reactions determining the impact on the occurrence of tropospheric ODEs brought by the change in TOC. From the analysis of the observational data and the numerical results, we suggested that the occurrence frequency of ODEs in the Antarctic seems negatively correlated with the variation of TOC. Moreover, major ODE accelerating reactions (i.e. photolysis of ozone, H2O2 and HCHO) and decelerating reactions (i.e. photolysis of BrO and HOBr), which heavily control the start of ODEs, were also identified. It was found that when TOC varies, the major ODE accelerating reactions speed up significantly, while major ODE decelerating reactions are only slightly affected, thus leading to the negative dependence of the ODE occurrence on the change in TOC.

scholarly journals First description and classification of the ozone hole over the Arctic in boreal spring 2020

2020 ◽  
Author(s):  
Martin Dameris ◽  
Diego G. Loyola ◽  
Matthias Nützel ◽  
Melanie Coldewey-Egbers ◽  
Christophe Lerot ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Total Ozone ◽  
Stratospheric Ozone ◽  
Ozone Hole ◽  
The Arctic ◽  
Atmospheric Conditions ◽  
Total Ozone Column ◽  
Boreal Spring ◽  
Ozone Column

Abstract. Ozone data derived from the TROPOMI sensor onboard the Sentinel-5 Precursor satellite are showing an atypical ozone hole feature in the polar region of the Northern hemisphere (Arctic) in spring 2020. A persistent ozone hole pattern with minimum total ozone column values around or below 220 Dobson units (DU) was seen for the first time over the Arctic for about 5 weeks in March and early April 2020. Usually an ozone hole with such low total ozone column values has only been observed in the polar Southern hemisphere (Antarctic) in spring over the last 4 decades, but not over the Arctic. The ozone hole pattern was caused by a particularly stable polar vortex in the stratosphere, enabling a persistent cold stratosphere at higher latitudes, a prerequisite for ozone depletion through heterogeneous chemistry. Based on the ERA5 reanalysis from ECMWF, the Northern winter 2019/2020 (from December to March) showed minimum polar cap temperatures consistently below 195 K around 20 km altitude, which enabled enhanced formation of polar stratospheric clouds. The special situation in spring 2020 is compared and discussed in context with two other ozone hole-like features in spring 1997 and 2011 that were showing comparable dynamical conditions in the stratosphere in combination with low total ozone column values. However, during these years total ozone columns below 220 DU over larger areas and over several consecutive days have not been observed. The similarities and differences of the atmospheric conditions of these three events and possible explanations are presented and discussed. It becomes apparent that the monthly mean of the minimum total ozone column value for March 2020 (i.e. 221 DU) was clearly below the respective values found in March 1997 (i.e. 267 DU) and 2011 (i.e. 252 DU), which emphasizes the noteworthiness of the evolution of the polar stratospheric ozone layer in Northern hemisphere spring 2020. These results provide a first description and classification of the development of the Arctic ozone hole in boreal spring 2020 and highlight its peculiarity.

scholarly journals Synergy of Using Nadir and Limb Instruments for Tropospheric Ozone Monitoring

2021 ◽  
Author(s):  
Viktoria F. Sofieva ◽  
Risto Hänninen ◽  
Mikhail Sofiev ◽  
Monika Szelag ◽  
Hei Shing Lee ◽  
...  
Keyword(s):  
Satellite Data ◽  
Tropospheric Ozone ◽  
Total Ozone ◽  
Stratospheric Ozone ◽  
Intermediate Step ◽  
Residual Method ◽  
Total Ozone Column ◽  
Clear Sky ◽  
Ozone Column ◽  
Good Agreement

Abstract. The satellite measurements in nadir and limb viewing geometry provide a complementary view of the atmosphere. An effective combination of the limb and nadir measurements can provide a new information about atmospheric composition. In this work, we present tropospheric ozone column datasets that have been created using combination of total ozone column from OMI and TROPOMI with stratospheric ozone column dataset from several available limb-viewing instruments (MLS, OSIRIS, MIPAS, SCIAMACHY, OMPS-LP, GOMOS). We have developed further the methodological aspects of assessment of tropospheric ozone using the residual method using simulations with the chemistry-transport model SILAM. It has been shown that the accurate assessment of ozone in the upper troposphere and the lower stratosphere (UTLS) is of high importance for detecting the ground-level ozone patterns. The stratospheric ozone column is derived from a combination of ozone profiles from several satellite instruments in limb-viewing geometry. We developed a method for the data homogenization, which includes the removal of biases and a-posteriori estimation (validation) of random uncertainties, thus making the data from different instruments compatible with each other. The high horizontal and vertical resolution dataset of ozone profiles is created via interpolation of the limb profiles from each day to 1° × 1° horizonal grid. A new kriging-type interpolation method, which takes into account data uncertainties and the information about natural ozone variations from the SILAM-adjusted ozone field, has been developed. To mitigate the limited accuracy and coverage of the limb profile data in the UTLS, a smooth transition to the model data is applied below the tropopause. This allows estimation of stratospheric ozone column with full coverage of the UTLS. The derived ozone profiles are in very good agreement with collocated ozonesonde measurements. The residual method was successfully applied to OMI and TROPOMI clear-sky total ozone data in combination with the stratospheric ozone column from the high-resolution limb profile dataset. The resulting tropospheric ozone column is in very good agreement with other satellite data. The global distributions of tropospheric ozone exhibit enhancements associated with the regions of high tropospheric ozone production. The main created datasets are (i) monthly 1° × 1° global tropospheric ozone column dataset using OMI and limb instruments, (ii) monthly 1° × 1° global tropospheric ozone column dataset using TROPOMI and limb instruments and (iii) daily 1° × 1° interpolated stratospheric ozone column from limb instruments. Other datasets, which are created as an intermediate step of creating the tropospheric ozone column data, are: (i) daily 1° × 1° clear sky and total ozone column from OMI and TROPOMI (ii) Daily 1° × 1° homogenized and interpolated dataset of ozone profiles and (iii) daily 1° × 1° dataset of ozone profiles from SILAM simulations with adjustment to satellite data. These datasets can be used in various studies related to ozone distributions, variability and trends, both in the troposphere and the stratosphere.

scholarly journals Reassessment of causes of ozone column variability following the eruption of Mount Pinatubo using a nudged CCM

2009 ◽  
Vol 9 (13) ◽  
pp. 4251-4260 ◽  
Author(s):  
P. Telford ◽  
P. Braesicke ◽  
O. Morgenstern ◽  
J. Pyle
Keyword(s):  
Total Ozone ◽  
Climate Model ◽  
Potential Temperature ◽  
Global Scale ◽  
Heterogeneous Chemistry ◽  
Mount Pinatubo ◽  
Complementary Approach ◽  
The Tropics ◽  
The Impact ◽  
Ozone Column

Abstract. The eruption of Mount Pinatubo produced the largest loading of stratospheric sulphate aerosol in the twentieth century. This heated the tropical lower stratosphere, affecting stratospheric circulation, and provided enhanced surface area for heterogeneous chemistry. These factors combined to produce record low values of "global" total ozone column. Though well studied, there remains some uncertainty about the attribution of this low ozone, with contributions from both chemical and dynamical effects. We take a complementary approach to previous studies, nudging the potential temperature and horizontal winds in the new UKCA chemistry climate model to reproduce the atmospheric response and assess the impact on global total ozone. We then combine model runs and observations to distinguish between chemical and dynamical effects. To estimate the effects of increased heterogeneous chemistry on ozone we compare runs with volcanically enhanced and background surface aerosol density. The modelled depletion of global ozone peaks at about 7 DU in early 1993, in good agreement with values obtained from observations. We subtract the modelled aerosol induced ozone loss from the observed ozone record and attribute the remaining variability to `dynamical' effects. The remaining variability is dominated by the QBO. We also examine tropical and mid-latitude ozone, diagnosing contributions from El Niño in the tropics and identifying dynamically driven low ozone in northern mid-latitudes, which we interpret as possible evidence of changes in the QBO. We conclude that, on a global scale, the record lows of extra-polar ozone are produced by the increased heterogeneous chemistry, although there is evidence for dynamics produced low ozone in certain regions, including northern mid-latitudes.

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