154 results on '"Dhomse, Sandip S."'
Search Results
2. Analysis of the global atmospheric background sulfur budget in a multi-model framework
- Author
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Brodowsky, Christina V., primary, Sukhodolov, Timofei, additional, Chiodo, Gabriel, additional, Aquila, Valentina, additional, Bekki, Slimane, additional, Dhomse, Sandip S., additional, Höpfner, Michael, additional, Laakso, Anton, additional, Mann, Graham W., additional, Niemeier, Ulrike, additional, Pitari, Giovanni, additional, Quaglia, Ilaria, additional, Rozanov, Eugene, additional, Schmidt, Anja, additional, Sekiya, Takashi, additional, Tilmes, Simone, additional, Timmreck, Claudia, additional, Vattioni, Sandro, additional, Visioni, Daniele, additional, Yu, Pengfei, additional, Zhu, Yunqian, additional, and Peter, Thomas, additional
- Published
- 2024
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3. Recent Trends in Stratospheric Chlorine From Very Short‐Lived Substances
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Hossaini, Ryan, Atlas, Elliot, Dhomse, Sandip S, Chipperfield, Martyn P, Bernath, Peter F, Fernando, Anton M, Mühle, Jens, Leeson, Amber A, Montzka, Stephen A, Feng, Wuhu, Harrison, Jeremy J, Krummel, Paul, Vollmer, Martin K, Reimann, Stefan, O'Doherty, Simon, Young, Dickon, Maione, Michela, Arduini, Jgor, and Lunder, Chris R
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Earth Sciences ,Atmospheric Sciences ,chlorine ,stratosphere ,VSLS ,chloroform ,dichloromethane ,ozone ,Physical Geography and Environmental Geoscience ,Atmospheric sciences ,Climate change science - Abstract
Very short-lived substances (VSLS), including dichloromethane (CH2Cl2), chloroform (CHCl3), perchloroethylene (C2Cl4), and 1,2-dichloroethane (C2H4Cl2), are a stratospheric chlorine source and therefore contribute to ozone depletion. We quantify stratospheric chlorine trends from these VSLS (VSLCltot) using a chemical transport model and atmospheric measurements, including novel high-altitude aircraft data from the NASA VIRGAS (2015) and POSIDON (2016) missions. We estimate VSLCltot increased from 69 (±14) parts per trillion (ppt) Cl in 2000 to 111 (±22) ppt Cl in 2017, with >80% delivered to the stratosphere through source gas injection, and the remainder from product gases. The modeled evolution of chlorine source gas injection agrees well with historical aircraft data, which corroborate reported surface CH2Cl2 increases since the mid-2000s. The relative contribution of VSLS to total stratospheric chlorine increased from ~2% in 2000 to ~3.4% in 2017, reflecting both VSLS growth and decreases in long-lived halocarbons. We derive a mean VSLCltot growth rate of 3.8 (±0.3) ppt Cl/year between 2004 and 2017, though year-to-year growth rates are variable and were small or negative in the period 2015-2017. Whether this is a transient effect, or longer-term stabilization, requires monitoring. In the upper stratosphere, the modeled rate of HCl decline (2004-2017) is -5.2% per decade with VSLS included, in good agreement to ACE satellite data (-4.8% per decade), and 15% slower than a model simulation without VSLS. Thus, VSLS have offset a portion of stratospheric chlorine reductions since the mid-2000s.
- Published
- 2019
4. Record High March 2024 Arctic Total Column Ozone.
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Newman, Paul A., Lait, Leslie R., Kramarova, Natalya A., Coy, Lawrence, Frith, Stacey M., Oman, Luke D., and Dhomse, Sandip S.
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OZONE layer ,EDDY flux ,OZONE layer depletion ,VIENNA Convention for the Protection of the Ozone Layer (1985). Protocols, etc., 1987 Sept. 15 ,POLAR vortex - Abstract
Observations of March 2024 Arctic (63°N–90°N) total column ozone set a record high of 477 Dobson Units (DU) against the 1979–2023 satellite era time series. It was about 60 DU higher than average and 6 DU higher than the previous March 1979 471 DU record. Daily Arctic ozone was above average for every day in March 2024, and set record highs from 11–26 March 2024. Microwave Limb Sounder data show this record ozone anomaly was concentrated in the lower stratosphere (10–30 km). These record values developed over the 2023–2024 winter and can be associated with vertically propagating planetary‐scale wave events that caused significant stratospheric warmings. These wave events forced poleward and downward ozone advection into the lower stratosphere, leading to record column ozone levels. The above average levels persisted through August 2024 and across the northern hemisphere. Plain Language Summary: Man‐made chlorofluorocarbons (CFCs) depleted the Earth ozone layer. The 1987 Montreal Protocol curbed CFC growth, but because CFCs have multi‐decadal lifetimes, Arctic ozone is not expected to recover back to 1980 levels until ∼2045. Current high CFC levels combined with persistent and cold polar vortices led to severe Arctic ozone spring depletion in 1997, 2011, and 2020. Contrary to expectations, March 2024 Arctic ozone showed a record high level, dramatically contrasting against the severe depletion events. Meteorological and ozone profile information show that the exceptional 2024 ozone was mainly found in the lowermost Arctic stratosphere, in association with record high lowermost stratospheric temperatures. The ozone levels incrementally increased during the 2023–2024 winter because of large‐scale weather systems that propagated from the troposphere into the stratosphere. Collectively, these weather systems also were at a record level, moving higher ozone concentrations from the mid‐latitudes and upper stratospheric into the Arctic region. This record high ozone would likely have not occurred if CFC levels had not begun slowly declining in response to the Montreal Protocol. Given the absence of high Arctic ozone since the 1970s, the March 2024 record high should be considered a positive harbinger of the future Arctic ozone layer. Key Points: Arctic total column ozone in March 2024 set a record high for the 1979‐present periodPolar lower stratosphere temperatures also set a record high in March 2024 in the MERRA‐2 reanalysis dataA record amount of Rossby waves propagating upward from the troposphere caused the record total ozone and lower stratospheric temperature [ABSTRACT FROM AUTHOR]
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- 2024
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5. Investigation of the impact of satellite vertical sensitivity on long-term retrieved lower-tropospheric ozone trends.
- Author
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Pope, Richard J., O'Connor, Fiona M., Dalvi, Mohit, Kerridge, Brian J., Siddans, Richard, Latter, Barry G., Barret, Brice, Le Flochmoen, Eric, Boynard, Anne, Chipperfield, Martyn P., Feng, Wuhu, Pimlott, Matilda A., Dhomse, Sandip S., Retscher, Christian, Wespes, Catherine, and Rigby, Richard
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AIR pollutants ,RADIATIVE transfer ,OZONE ,TIME series analysis ,TROPOSPHERIC ozone ,TROPOSPHERE - Abstract
Ozone is a potent air pollutant in the lower troposphere and an important short-lived climate forcer (SLCF) in the upper troposphere. Studies investigating long-term trends in the tropospheric column ozone (TCO 3) have shown large-scale spatio-temporal inconsistencies. Here, we investigate the long-term trends in lower-tropospheric column ozone (LTCO 3 , surface–450 hPa sub-column) by exploiting a synergy of satellite and ozonesonde data sets and an Earth system model (UK's Earth System Model, UKESM) over North America, Europe, and East Asia for the decade 2008–2017. Overall, we typically find small LTCO 3 linear trends with large uncertainty ranges using the Ozone Monitoring Instrument (OMI) and the Infrared Atmospheric Sounding Interferometer (IASI), while model simulations indicate a stable LTCO 3 tendency. The satellite a priori data sets show negligible trends, indicating that any year-to-year changes in the spatio-temporal sampling of these satellite data sets over the period concerned have not artificially influenced their LTCO 3 temporal evolution. The application of the satellite averaging kernels (AKs) to the UKESM simulated ozone profiles, accounting for the satellite vertical sensitivity and allowing for like-for-like comparisons, has a limited impact on the modelled LTCO 3 tendency in most cases. While, in relative terms, this is more substantial (e.g. on the order of 100 %), the absolute magnitudes of the model trends show negligible change. However, as the model has a near-zero tendency, artificial trends were imposed on the model time series (i.e. LTCO 3 values rearranged from smallest to largest) to test the influence of the AKs, but simulated LTCO 3 trends remained small. Therefore, the LTCO 3 tendencies between 2008 and 2017 in northern-hemispheric regions are likely to be small, with large uncertainties, and it is difficult to detect any small underlying linear trends due to interannual variability or other factors which require further investigation (e.g. the radiative transfer scheme (RTS) used and/or the inputs (e.g. meteorological fields) used in the RTS). [ABSTRACT FROM AUTHOR]
- Published
- 2024
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6. Investigation of spatial and temporal variability in lower tropospheric ozone from RAL Space UV–Vis satellite products
- Author
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Pope, Richard J., primary, Kerridge, Brian J., additional, Siddans, Richard, additional, Latter, Barry G., additional, Chipperfield, Martyn P., additional, Feng, Wuhu, additional, Pimlott, Matilda A., additional, Dhomse, Sandip S., additional, Retscher, Christian, additional, and Rigby, Richard, additional
- Published
- 2023
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7. Antarctic Vortex Dehydration in 2023 as a Substantial Removal Pathway for Hunga Tonga‐Hunga Ha'apai Water Vapor.
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Zhou, Xin, Dhomse, Sandip S., Feng, Wuhu, Mann, Graham, Heddell, Saffron, Pumphrey, Hugh, Kerridge, Brian J., Latter, Barry, Siddans, Richard, Ventress, Lucy, Querel, Richard, Smale, Penny, Asher, Elizabeth, Hall, Emrys G., Bekki, Slimane, and Chipperfield, Martyn P.
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WATER vapor , *POLAR vortex , *STRATOSPHERIC aerosols , *HUNGA Tonga-Hunga Ha'apai Eruption & Tsunami, 2022 , *ATMOSPHERIC water vapor measurement , *OZONE layer depletion , *ATMOSPHERIC models , *STRATOSPHERIC chemistry - Abstract
The January 2022 eruption of Hunga Tonga‐Hunga Ha'apai (HTHH) injected a huge amount (∼150 Tg) of water vapor (H2O) into the stratosphere, along with small amount of SO2. An off‐line 3‐D chemical transport model (CTM) successfully reproduces the spread of the injected H2O through October 2023 as observed by the Microwave Limb Sounder. Dehydration in the 2023 Antarctic polar vortex caused the first substantial (∼20 Tg) removal of HTHH H2O from the stratosphere. The CTM indicates that this process will dominate removal of HTHH H2O for the coming years, giving an overall e‐folding timescale of 4 years; around 25 Tg of the injected H2O is predicted to still remain in the stratosphere by 2030. Following relatively low Antarctic column ozone in midwinter 2023 due to transport effects, additional springtime depletion due to H2O‐related chemistry was small and maximized at the vortex edge (10 DU in column). Plain Language Summary: Around 150 Tg (150 million tons) of water vapor was injected into the stratosphere during the eruption of Hunga Tonga‐Hunga Ha'apai. Water vapor is a greenhouse gas and this increase is expected to have a warming effect in the troposphere, as well causing perturbations in stratospheric chemistry and aerosols. We use an atmospheric model to study the residence time of this excess water vapor and its impact on the recent Antarctic ozone hole. The model performance is evaluated by comparison with satellite measurements. Wintertime dehydration in the Antarctic stratosphere in 2023 is found to be an important mechanism for removal of the volcanic water from the stratosphere. However, the overall removal rate is predicted to be slow; around 25 Tg (17%) is still present in 2030. The direct impact of the excess water vapor on ozone via chemical processes in the Antarctic ozone hole in 2023 is small. Key Points: Antarctic dehydration is a major removal pathway of stratospheric H2O injected from Hunga Tonga‐Hunga Ha'apai (HTHH) eruptionHTHH H2O caused small (up to 10 DU) additional chemical ozone depletion in 2023 Antarctic springModel indicates e‐folding timescale of 4 years for removal of HTHH H2O from stratosphere [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
8. Quantifying the tropospheric ozone radiative effect and its temporal evolution in the satellite era.
- Author
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Pope, Richard J., Rap, Alexandru, Pimlott, Matilda A., Barret, Brice, Le Flochmoen, Eric, Kerridge, Brian J., Siddans, Richard, Latter, Barry G., Ventress, Lucy J., Boynard, Anne, Retscher, Christian, Feng, Wuhu, Rigby, Richard, Dhomse, Sandip S., Wespes, Catherine, and Chipperfield, Martyn P.
- Subjects
TROPOSPHERIC ozone ,OZONE ,CHEMICAL models ,METEOROLOGY - Abstract
Using state-of-the-art satellite ozone profile products, and a chemical transport model, we provide an updated estimate of the tropospheric ozone radiative effect (TO 3 RE) and observational constraint on its variability over the decade 2008–2017. Previous studies have shown the short-term (i.e. a few years) globally weighted average TO 3 RE to be 1.17 ± 0.03 W m -2. However, from our analysis, using decadal (2008–2017) ozone profile datasets from the Infrared Atmospheric Sounding Interferometer, average TO 3 RE ranges between 1.21 and 1.26 W m -2. Over this decade, the modelled and observational TO 3 RE linear trends show a negligible change (e.g. ± 0.1 % yr -1). Two model sensitivity experiments fixing emissions and meteorology to 1 year (i.e. start year – 2008) show that temporal changes in ozone precursor emissions (increasing contribution) and meteorological factors (decreasing contribution) have counteracting tendencies, leading to a negligible globally weighted average TO 3 RE trend. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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9. The Influence of Internal Climate Variability on Stratospheric Water Vapor Increases After Large‐Magnitude Explosive Tropical Volcanic Eruptions
- Author
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Zhou, Xin, primary, Mann, Graham W., additional, Feng, Wuhu, additional, Dhomse, Sandip S., additional, and Chipperfield, Martyn P., additional
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- 2023
- Full Text
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10. Quantifying effects of long-range transport of NO2 over Delhi using back trajectories and satellite data.
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Graham, Ailish M., Pope, Richard J., Chipperfield, Martyn P., Dhomse, Sandip S., Pimlott, Matilda, Feng, Wuhu, Singh, Vikas, Chen, Ying, Wild, Oliver, Sokhi, Ranjeet, and Beig, Gufran
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EMISSION inventories ,INCINERATION ,AGRICULTURAL wastes ,ATMOSPHERIC methane ,AIR pollution ,BOUNDARY layer (Aerodynamics) ,AIR quality ,WILDFIRES - Abstract
Exposure to air pollution is a leading public health risk factor in India, especially over densely populated Delhi and the surrounding Indo-Gangetic Plain. During the post-monsoon seasons, the prevailing north-westerly winds are known to influence aerosol pollution events in Delhi by advecting pollutants from agricultural fires as well as from local sources. Here we investigate the year-round impact of meteorology on gaseous nitrogen oxides (NOx=NO+NO2). We use bottom-up NOx emission inventories (anthropogenic and fire) and high-resolution satellite measurement based tropospheric column NO2 (TCNO 2) data, from S5P aboard TROPOMI, alongside a back-trajectory model (ROTRAJ) to investigate the balance of local and external sources influencing air pollution changes in Delhi, with a focus on different emissions sectors. Our analysis shows that accumulated emissions (i.e. integrated along the trajectory path, allowing for chemical loss) are highest under westerly, north-westerly and northerly flow during pre-monsoon (February–May) and post-monsoon (October–February) seasons. According to this analysis, during the pre-monsoon season, the highest accumulated satellite TCNO 2 trajectories come from the east and north-west of Delhi. TCNO 2 is elevated within Delhi and the Indo-Gangetic Plain (IGP) to the east of city. The accumulated NOx emission trajectories indicate that the transport and industry sectors together account for more than 80 % of the total accumulated emissions, which are dominated by local sources (>70 %) under easterly winds and north-westerly winds. The high accumulated emissions estimated during the pre-monsoon season under north-westerly wind directions are likely to be driven by high NOx emissions locally and in nearby regions (since NOx lifetime is reduced and the boundary layer is relatively deeper in this season). During the post-monsoon season the highest accumulated satellite TCNO 2 trajectories are advected from Punjab and Haryana, where satellite TCNO 2 is elevated, indicating the potential for the long-range transport of agricultural burning emissions to Delhi. However, accumulated NOx emissions indicate local (70 %) emissions from the transport sector are the largest contributor to the total accumulated emissions. High local emissions, coupled with a relatively long NOx atmospheric lifetime and shallow boundary layer, aid the build-up of emissions locally and along the trajectory path. This indicates the possibility that fire emissions datasets may not capture emissions from agricultural waste burning in the north-west sufficiently to accurately quantify their influence on Delhi air quality (AQ). Analysis of daily ground-based NO2 observations indicates that high-pollution episodes (>90 th percentile) occur predominantly in the post-monsoon season, and more than 75 % of high-pollution events are primarily caused by local sources. But there is also a considerable influence from non-local (30 %) emissions from the transport sector during the post-monsoon season. Overall, we find that in the post-monsoon season, there is substantial accumulation of high local NOx emissions from the transport sector (70 % of total emissions, 70 % local), alongside the import of NOx pollution into Delhi (30 % non-local). This work indicates that both high local NOx emissions from the transport sector and the advection of highly polluted air originating from outside Delhi are of concern for the population. As a result, air quality mitigation strategies need to be adopted not only in Delhi but in the surrounding regions to successfully control this issue. In addition, our analysis suggests that the largest benefits to Delhi NOx air quality would be seen with targeted reductions in emissions from the transport and agricultural waste burning sectors, particularly during the post-monsoon season. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
11. Investigation of satellite vertical sensitivity on long-term retrieved lower tropospheric 1 ozone trends.
- Author
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Pope, Richard J., O'Connor, Fiona M., Dalvi, Mohit, Kerridge, Brian J., Siddans, Richard, Latter, Barry G., Barret, Brice, Flochmoen, Eric Le, Boynard, Anne, Chipperfield, Martyn P., Wuhu Feng, Pimlott, Matilda A., Dhomse, Sandip S., Retscher, Christian, Wespes, Catherine, and Rigby, Richard
- Abstract
Ozone is a potent air pollutant in the lower troposphere and an important short-lived climate forcer (SLCF) in the upper troposphere. Studies investigating long-term trends in tropospheric column ozone (TCO3) have shown large-scale spatiotemporal inconsistencies. Here, we investigate the long-term trends in lower tropospheric column ozone (LTCO3, surface-450 hPa sub-column) by exploiting a synergy of satellite and ozonesonde datasets and an Earth System Model (UKESM) over North America, Europe and East Asia for the decade 2008-2017. Overall, we typically find small LTCO3 linear trends with large uncertainty ranges from the Ozone Monitoring Instrument (OMI) and the Infrared Atmospheric Sounding Interferometer (IASI), while model simulations indicate a stable LTCO3 tendency. Trends in the satellite a priori datasets show negligible trends indicating year-to-year sampling is not an issue. The application of the satellite averaging kernels AKs) to the UKESM ozone profiles, accounting for the satellite vertical sensitivity and allowing for like-for41 like comparisons, has a limited impact on the modelled LTCO3 tendency in most cases. While, in relative terms, this is more substantial (e.g. in the order of 100%), the absolute magnitudes of the model trends show negligible change. However, as the model has a near-zero tendency, artificial trends were imposed on the model time-series (i.e. LTCO3 values rearranged from smallest to largest) to test the influence of the AKs but simulated LTCO3 trends remained small. Therefore, the LTCO3 tendency between 2008 and 2017 in northern hemispheric regions are likely small, with large uncertainties, and it is difficult to detect any small underlying linear trends due to inter-annual variability or other factors which require further investigation. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
12. Using machine learning to construct TOMCAT model and occultation measurement-based stratospheric methane (TCOM-CH4) and nitrous oxide (TCOM-N2O) profile data sets.
- Author
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Dhomse, Sandip S. and Chipperfield, Martyn P.
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NITROUS oxide , *MACHINE learning , *FOURIER transform spectrometers , *OZONE layer , *ATMOSPHERIC chemistry , *METHANE , *CHEMISTRY experiments - Abstract
Monitoring the atmospheric concentrations of greenhouse gases (GHGs) is crucial to improve our understanding of their climate impact. However, there are no long-term profile data sets of important GHGs that can be used to gain a better insight into the processes controlling their variations in the atmosphere. In this study, we apply corrections to chemical transport model (CTM) output based on profile measurements from two solar occultation instruments: the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS). The goal is to construct long-term (1991–2021), gap-free stratospheric profile data sets, hereafter referred to as TCOM, for two important GHGs. To estimate the corrections that need to be applied to the CTM profiles, we use the extreme gradient boosting (XGBoost) regression model. For methane (TCOM-CH4), we utilize both HALOE and ACE satellite profile measurements from 1992 to 2018 to train the XGBoost model, while profiles from 2019 to 2021 serve as an independent evaluation data set. As there are no nitrous oxide (N 2 O) profile measurements for earlier years, we derive XGBoost-derived correction terms to construct TCOM-N2O profiles using only ACE-FTS profiles from the 2004–2018 time period, with profiles from 2019–2021 used for the independent evaluation. Overall, both TCOM-CH4 and TCOM-N2O profiles exhibit excellent agreement with the available satellite-measurement-based data sets. We find that compared to evaluation profiles, biases in TCOM-CH4 and TCOM-N2O are generally less than 10 % and 50 %, respectively, throughout the stratosphere. The daily zonal mean profile data sets, covering altitude (15–60 km) and pressure (300–0.1 hPa) levels, are publicly available via the following links: 10.5281/zenodo.7293740 for TCOM-CH4 and 10.5281/zenodo.7386001 for TCOM-N2O. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
13. Investigation of spatial and temporal variability in lower tropospheric ozone from RAL Space UV-Vis satellite products
- Author
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Pope, Richard J., Kerridge, Brian J., Siddans, Richard, Latter, Barry G., Chipperfield, Martyn P., Feng, Wuhu, Pimlott, Matilda A., Dhomse, Sandip S., Retscher, Christian, and Rigby, Richard
- Abstract
Ozone is a potent air pollutant in the lower troposphere and an important short-lived climate forcer (SLCF) in the upper troposphere. Studies using satellite data to investigate spatiotemporal variability of troposphere ozone (TO3) have predominantly focussed on the tropospheric column metric. This is the first study to investigate long-term spatiotemporal variability in lower tropospheric column ozone (LTCO3, surface-450 hPa sub-column) by merging multiple European Space Agency – Climate Change Initiative (ESA-CCI) products produced by the Rutherford Appleton Laboratory (RAL) Space. We find that in the LTCO3, the degrees of freedom of signal (DOFS) from these products varies with latitude range and season and is up to 0.65, indicating that the retrievals contain useful information on lower TO3. The spatial and seasonal variation of the RAL Space products are in good agreement with each other but there are systematic offsets of up to 3.0–5.0 DU between them. Comparison with ozonesondes shows that the Global Ozone Monitoring Experiment (GOME-1, 1996–2003), the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY, 2003–2010) and the Ozone Monitoring Instrument (OMI, 2005–2017) have stable LTCO3 records over their respective periods, which can be merged together. While GOME-2 (2008–2018) shows substantial drift in its bias with respect to ozonesondes. We have therefore constructed a robust merged dataset of LTCO3 from GOME-1, SCIAMACHY and OMI between 1996 and 2017. Comparing the LTCO3 differences between the 1996–2000 and 2013–2017 5-year averages, we find significant positive increases (3.0–5.0 DU) in the tropics/sub-tropics, while in the northern mid-latitudes, we find small scale differences in LTCO3. Therefore, we conclude that there has been a substantial increase in tropical/sub-tropical LTCO3 during the satellite-era.
- Published
- 2023
14. Quantifying stratospheric ozone trends over 1984–2020: a comparison of ordinary and regularized multivariate regression models.
- Author
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Li, Yajuan, Dhomse, Sandip S., Chipperfield, Martyn P., Feng, Wuhu, Bian, Jianchun, Xia, Yuan, and Guo, Dong
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OZONE layer ,EL Nino ,ANTARCTIC oscillation ,REGRESSION analysis ,SOLAR oscillations ,ARCTIC oscillation - Abstract
Accurate quantification of long-term trends in stratospheric ozone can be challenging due to their sensitivity to natural variability, the quality of the observational datasets, and non-linear changes in forcing processes as well as the statistical methodologies. Multivariate linear regression (MLR) is the most commonly used tool for ozone trend analysis; however, the complex coupling in many atmospheric processes can make it prone to the issue of over-fitting when using the conventional ordinary-least-squares (OLS) approach. To overcome this issue, here we adopt a regularized (ridge) regression method to estimate ozone trends and quantify the influence of individual processes. We use the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) merged dataset (v2.7) to derive stratospheric ozone profile trends for the period 1984–2020. Besides SWOOSH, we also analyse a machine-learning-based satellite-corrected gap-free global stratospheric ozone profile dataset from a chemical transport model (ML-TOMCAT) and output from a chemical transport model (TOMCAT) simulation forced with European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis. For 1984–1997, we observe smaller negative trends in the SWOOSH stratospheric ozone profile using ridge regression compared to OLS. Except for the tropical lower stratosphere, the largest differences arise in the mid-latitude lowermost stratosphere (>4 % per decade difference at 100 hPa). From 1998 and the onset of ozone recovery in the upper stratosphere, the positive trends estimated using the ridge regression model (∼1 % per decade near 2 hPa) are smaller than those using OLS (∼2 % per decade). In the lower stratosphere, post-1998 negative trends with large uncertainties are observed and ridge-based trend estimates are somewhat smaller and less variable in magnitude compared to the OLS regression. Aside from the tropical lower stratosphere, the largest difference is around 2 % per decade at 100 hPa (with ∼3 % per decade uncertainties for individual trends) in northern mid-latitudes. For both time periods the SWOOSH data produce large negative trends in the tropical lower stratosphere with a correspondingly large difference between the two trend methods. In both cases the ridge method produces a smaller trend. The regression coefficients from both OLS and ridge models, which represent ozone variations associated with natural processes (e.g. the quasi-biennial oscillation, solar variability, El Niño–Southern Oscillation, Arctic Oscillation, Antarctic Oscillation, and Eliassen–Palm flux), highlight the dominance of dynamical processes in controlling lower-stratospheric ozone concentrations. Ridge regression generally yields smaller regression coefficients due to correlated explanatory variables, and care must be exercised when comparing fit coefficients and their statistical significance across different regression methods. Comparing the ML-TOMCAT-based trend estimates with the ERA5-forced model simulation, we find ML-TOMCAT shows significant improvements with much better consistency with the SWOOSH dataset, despite the ML-TOMCAT training period overlapping with SWOOSH only for the Microwave Limb Sounder (MLS) measurement period. The largest inconsistencies with respect to SWOOSH-based trends post-1998 appear in the lower stratosphere where the ERA5-forced model simulation shows positive trends for both the tropics and the mid-latitudes. The large differences between satellite-based data and the ERA5-forced model simulation confirm significant uncertainties in ozone trend estimates, especially in the lower stratosphere, underscoring the need for caution when interpreting results obtained with different regression methods and datasets. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
15. Quantifying the tropospheric ozone radiative effect and its temporal evolution in the satellite-era.
- Author
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Pope, Richard J., Rap, Alexandru, Pimlott, Matilda A., Barret, Brice, Le Flochmoen, Eric, Kerridge, Brian J., Siddans, Richard, Latter, Barry G., Ventress, Lucy J., Boynard, Anne, Retscher, Christian, Wuhu Feng, Rigby, Richard, Dhomse, Sandip S., Wespes, Catherine, and Chipperfield, Martyn P.
- Abstract
Using state-of-the-art satellite ozone profile products, and chemical transport model, we provide an updated estimate of the tropospheric ozone radiative effect (TO
3 RE) and observational constraint on its variability over the decade 2008–2017. Previous studies have shown the short-term (i.e. a few years) globally weighted average TO3 RE to be 1.17±0.03 W/m², while our analysis suggests that the long-term (2008–2017) average TO3 RE to be 1.21–1.28 W/m². Over this decade, the modelled/observational TO3 RE linear trends show negligible change (i.e. ±0.1 %/year), so the tropospheric ozone radiative contribution to climate has remained stable with time. Two model sensitivity experiments fixing emissions and meteorology to one year (i.e. start year – 2008) show that ozone precursor emissions (meteorological factors) have had limited (substantial) impacts on the long-term tendency of globally weighted average TO3 RE. Here, the meteorological variability in the tropical/sub-tropical upper troposphere is dampening any tendency in TO3 RE from other factors (e.g. emissions, atmospheric chemistry). [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
16. Analysis of the global atmospheric background sulfur budget in a multi-model framework.
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Brodowsky, Christina V., Sukhodolov, Timofei, Chiodo, Gabriel, Aquila, Valentina, Bekki, Slimane, Dhomse, Sandip S., Laakso, Anton, Mann, Graham W., Niemeier, Ulrike, Quaglia, Ilaria, Rozanov, Eugene, Schmidt, Anja, Takashi Sekiya, Tilmes, Simone, Timmreck, Claudia, Vattioni, Sandro, Visioni, Daniele, Pengfei Yu, Yunqian Zhu, and Peter, Thomas
- Published
- 2023
- Full Text
- View/download PDF
17. Interactive stratospheric aerosol models' response to different amounts and altitudes of SO2 injection during the 1991 Pinatubo eruption
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Quaglia, Ilaria, primary, Timmreck, Claudia, additional, Niemeier, Ulrike, additional, Visioni, Daniele, additional, Pitari, Giovanni, additional, Brodowsky, Christina, additional, Brühl, Christoph, additional, Dhomse, Sandip S., additional, Franke, Henning, additional, Laakso, Anton, additional, Mann, Graham W., additional, Rozanov, Eugene, additional, and Sukhodolov, Timofei, additional
- Published
- 2023
- Full Text
- View/download PDF
18. Comment on “Observation of large and all-season ozone losses over the tropics” [AIP Adv. 12, 075006 (2022)]
- Author
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Chipperfield, Martyn P., primary, Chrysanthou, Andreas, additional, Damadeo, Robert, additional, Dameris, Martin, additional, Dhomse, Sandip S., additional, Fioletov, Vitali, additional, Frith, Stacey M., additional, Godin-Beekmann, Sophie, additional, Hassler, Birgit, additional, Liu, Jane, additional, Müller, Rolf, additional, Petropavlovskikh, Irina, additional, Santee, Michelle L., additional, Stauffer, Ryan M., additional, Tarasick, David, additional, Thompson, Anne M., additional, Weber, Mark, additional, and Young, Paul J., additional
- Published
- 2022
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19. Effects of reanalysis forcing fields on ozone trends and age of air from a chemical transport model
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Li, Yajuan, primary, Dhomse, Sandip S., additional, Chipperfield, Martyn P., additional, Feng, Wuhu, additional, Chrysanthou, Andreas, additional, Xia, Yuan, additional, and Guo, Dong, additional
- Published
- 2022
- Full Text
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20. Tropospheric Jet Response to Antarctic Ozone Depletion: An Update with Chemistry-Climate Model Initiative (CCMI) Models
- Author
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Son, Seok-Woo, Han, Bo-Reum, Garfinkel, Chaim I, Kim, Seo-Yeon, Park, Rokjin, Abraham, N. Luke, Akiyoshi, Hideharu, Archibald, Alexander T, Butchart, N, Chipperfield, Martyn P, Dameris, Martin, Deushi, Makoto, Dhomse, Sandip S, Hardiman, Steven C, Jockel, Patrick, Kinnison, Douglas, Michou, Martine, Morgenstern, Olaf, O’Connor, Fiona M, Oman, Luke D, Plummer, David A, Pozzer, Andrea, Revell, Laura E, Rozanov, Eugene, Stenke, Andrea, Stone, Kane, Tilmes, Simone, Yamashita, Yousuke, and Zeng, Guang
- Subjects
Geosciences (General) - Abstract
The Southern Hemisphere (SH) zonal-mean circulation change in response to Antarctic ozone depletion is re-visited by examining a set of the latest model simulations archived for the Chemistry-Climate Model Initiative (CCMI) project. All models reasonably well reproduce Antarctic ozone depletion in the late 20th century. The related SH-summer circulation changes, such as a poleward intensification of westerly jet and a poleward expansion of the Hadley cell, are also well captured. All experiments exhibit quantitatively the same multi-model mean trend, irrespective of whether the ocean is coupled or prescribed. Results are also quantitatively similar to those derived from the Coupled Model Intercomparison Project phase 5 (CMIP5) high-top model simulations in which the stratospheric ozone is mostly prescribed with monthly- and zonally-averaged values. These results suggest that the ozone-hole-induced SH-summer circulation changes are robust across the models irrespective of the specific chemistry-atmosphere-ocean coupling.
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- 2018
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21. Ozone Sensitivity to Varying Greenhouse Gases and Ozone-Depleting Substances in CCMI-1 Simulations
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Morgenstern, Olaf, Stone, Kane A, Schofield, Robyn, Akiyoshi, Hideharu, Yamashita, Yousuke, Kinnison, Douglas E, Garcia, Rolando R, Sudo, Kengo, Plummer, David A, Scinocca, John, Oman, Luke D, Manyin, Michael E, Zeng, Guang, Rozanov, Eugene, Stenke, Andrea, Revell, Laura E, Pitari, Giovanni, Mancini, Eva, Genova, Glauco Di, Visioni, Daniele, Dhomse, Sandip S, and Chipperfield, Martyn P
- Subjects
Geosciences (General) - Abstract
Ozone fields simulated for the first phase of the Chemistry-Climate Model Initiative (CCMI-1) will be used as forcing data in the 6th Coupled Model Intercomparison Project. Here we assess, using reference and sensitivity simulations produced for CCMI-1, the suitability of CCMI-1 model results for this process, investigating the degree of consistency amongst models regarding their responses to variations in individual forcings. We consider the influences of methane, nitrous oxide, a combination of chlorinated or brominated ozone-depleting substances, and a combination of carbon dioxide and other greenhouse gases. We find varying degrees of consistency in the models' responses in ozone to these individual forcings, including some considerable disagreement. In particular, the response of total-column ozone to these forcings is less consistent across the multi-model ensemble than profile comparisons. We analyse how stratospheric age of air, a commonly used diagnostic of stratospheric transport, responds to the forcings. For this diagnostic we find some salient differences in model behaviour, which may explain some of the findings for ozone. The findings imply that the ozone fields derived from CCMI-1 are subject to considerable uncertainties regarding the impacts of these anthropogenic forcings. We offer some thoughts on how to best approach the problem of generating a consensus ozone database from a multi-model ensemble such as CCMI-1.
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- 2018
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22. TCOR-CH4: Daily global 3-D stratospheric methane profile dataset constructed using TOMCAT CTM, Occultation measurements and Random Forest
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Dhomse Sandip, S.
- Subjects
methane profiles, stratosphere, Random Forest, Satellite data - Abstract
These are 31-data files (1 per calendar year) containing daily 3D global methane profile data set. Vertical profiles are available at 1 km vertical resolution (10km-60km) for 1991-2021 time period at 128 X 64 degree horizontal resolution (12 UTC). The data set are constructed using methane profiles from TOMCAT CTM that are corrected using Random Forest w.r.t. vertical profiles measurements from two solar occultation instruments (HALOE [1991-2005] and ACE [2004-2021]). Methodology: TOMCAT simulation is performed at T64L32 resolution that is similar to the one used in Dhomse et al., (2021, 2022) for 1991-2021 time period. Collocated methane profiles are divided in five latitude bins: SH polar (90S-60S), SH mid-lat (60S-30S), tropics (30S-30N), NH mid-lat (30N-60N) and NH polar (60N-90N). Initially, differences are calculated for each zonal bins for 51 height levels (10km to 60km). Then separate Random Forest regression models are trained for the methane differences between TOMCAT and measurements at each level for a given latitude bin. Same model is used for all 11323 days for TOMCAT output at 12 UTC to get bias corrections for a given model grid that are added to the original TOMCAT profiles. Note that there are fewer occultation measurements below tropopause, hence TCOR profiles below tropopause are not well constrained. Dataset also includes two additional files: ch4-monthly-TCOR-19910101-2021231.nc – monthly mean fields (3D) zmch4-daily-TCOR-19910101-2021231.nc – zonal mean daily fields We are not sure about exact cause of unusual methane variations during 1991-1994, but some recent studies argue that it could be due to sudden changes in methane loss processes following Mount Pinatubo eruption as well as significant changes in methane emissions following collapse of soviet union.
- Published
- 2022
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23. Comment on “Observation of large and all-season ozone losses over the tropics” [AIP Adv. 12, 075006 (2022)]
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Chipperfield, Martyn P., Chrysanthou, Andreas, Damadeo, Robert, Dameris, Martin, Dhomse, Sandip S., Fioletov, Vitali, Frith, Stacey M., Godin-Beekmann, Sophie, Hassler, Birgit, Liu, Jane, Müller, Rolf, Petropavlovskikh, Irina, Santee, Michelle L., Stauffer, Ryan M., Tarasick, David, Thompson, Anne M., Weber, Mark, Young, Paul J., Chipperfield, Martyn P., Chrysanthou, Andreas, Damadeo, Robert, Dameris, Martin, Dhomse, Sandip S., Fioletov, Vitali, Frith, Stacey M., Godin-Beekmann, Sophie, Hassler, Birgit, Liu, Jane, Müller, Rolf, Petropavlovskikh, Irina, Santee, Michelle L., Stauffer, Ryan M., Tarasick, David, Thompson, Anne M., Weber, Mark, and Young, Paul J.
- Published
- 2022
24. Stratospheric ozone trends and attribution over 1984-2020 using ordinary and regularised multivariate regression models.
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Yajuan Li, Dhomse, Sandip S., Chipperfield, Martyn P., Wuhu Feng, Jianchun Bian, Yuan Xia, and Dong Guo
- Abstract
Accurate quantification of long-term trends in stratospheric ozone can be challenging due to their sensitivity to natural variability, the quality of the observational datasets, non-linear changes in forcing processes as well as the statistical methodologies. Multivariate linear regression (MLR) is the most commonly used tool for ozone trend analysis, however, the complex coupling in most atmospheric processes can make it prone to the over-fitting or multi-collinearity-related issues when using the conventional Ordinary Least Squares (OLS) setting. To overcome this issue, we adopt a regularised (Ridge) regression method to estimate ozone trends and quantify the influence of individual processes. Here, we use the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) merged data set (v2.7) to derive stratospheric ozone profile trends for the period 1984-2020. Beside SWOOSH, we also analyse a machine-learning-based satellite-corrected gap-free global stratospheric ozone profile dataset from a chemical transport model (ML-TOMCAT), and output from two chemical transport model (TOMCAT) simulations forced with ECMWF reanalyses ERA-Interim and ERA5. With Ridge regression, the stratospheric ozone profile trends from SWOOSH data show smaller declines during 1984-1997 compared to OLS with the largest differences in the lowermost stratosphere (>4 % per decade at 100 hPa). Upper stratospheric ozone has increased since 1998 with maximum (~2 % per decade near 2 hPa) in local winter for mid-latitudes. Negative trends with large uncertainties are observed in the lower stratosphere with the most pronounced in the tropics. The largest differences in post-1998 trend estimates between OLS and Ridge regression methods appear in the tropical lower stratosphere (with ~7 % per decade difference at 100 hPa). Ozone variations associated with natural processes such as the quasi-biennial oscillation QBO), the solar variability, the El Niño-Southern Oscillation (ENSO), the Arctic oscillation (AO) and the Antarctic oscillation (AAO) also indicate that Ridge regression coefficients are somewhat smaller and less variable compared to the OLS-based estimates. Additionally, ML-TOMCAT based trend estimates are consistent with SWOOSH data set. Finally, we argue that the large differences between the satellite-based data and model simulations confirm that there are still large uncertainties in ozone trend estimates especially in the lower stratosphere, and caution is needed when discussing results if explanatory variables used are correlated. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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25. Quantifying effects of long-range transport of NO2 over Delhi using back-trajectories and satellite data.
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Graham, Ailish M., Pope, Richard J., Chipperfield, Martyn P., Dhomse, Sandip S., Pimlott, Matilda, Wuhu Feng, Singh, Vikas, Ying Chen, Wild, Oliver, Sokhi, Ranjeet, and Beig, Gufran
- Abstract
Exposure to air pollution is a leading public health risk factor in India, especially over densely populated Delhi and the surrounding Indo-Gangetic Plain. During the post-monsoon months, the prevailing northwesterly winds are known to influence aerosol pollution events in Delhi, by advecting pollutants from agricultural fires as well as from local sources. Here we investigate the year-round impact of meteorology on gaseous nitrogen oxides (NO
x =NO + NO2 ), a hazardous primary air pollutant for health, which can lead to the formation of secondary aerosols and ozone. We use bottom-up NOx emission inventories (anthropogenic and fire) and high-resolution satellite measurement based tropospheric column NO2 (TCNO2 ) data, from S5P on-board TROPOMI, alongside a back-trajectory model (ROTRAJ) to investigate the balance of local and external sources influencing air pollution changes in Delhi, with a focus on different emission sectors. Our analysis shows that accumulated emissions (i.e. integrated along the trajectory path, allowing for chemical loss) are highest under westerly, north-westerly and northerly flow during pre- (February - March) and post- (October - January) monsoon periods. During the premonsoon period, the residential and transport sectors together account for more than 50% of the total accumulated emissions, which are dominated by local sources (90%) under easterly winds and by non35 local sources (>70%) under north-westerly winds. The high accumulated emissions estimated during the pre-monsoon season under north-westerly wind directions are likely to be driven by high NOx emissions locally and in nearby regions (since NOx lifetime is reduced and the boundary layer is relatively deeper in this period). During the post-monsoon period non-local (60%) transport emissions are the largest contributor to the total accumulated emissions as high emissions, coupled with a relatively long NOx atmospheric lifetime and shallow boundary-layer aid the build-up of emissions along the trajectory path. Analysis of surface daily NO2 observations indicates that high pollution episodes (> 90th percentile) occur predominantly in the post-monsoon and more than 75% of high pollution events are primarily caused by non-local sources. Overall, we find that in the post-monsoon period, there is a substantial import of NOx pollution into Delhi with a large contribution from the transport sector. This work indicates that the advection of highly polluted air originating from outside Delhi is of concern for the population and air quality mitigation strategies need to be adopted not only in Delhi but in the surrounding regions to successfully control this issue. In addition, our analysis suggests that the largest benefits to Delhi NOx air quality would be seen with targeted reductions in emissions from the transport sector, particularly during post-monsoon months. [ABSTRACT FROM AUTHOR]- Published
- 2023
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26. Review of the Global Models Used Within Phase 1 of the Chemistry-Climate Model Initiative (CCMI)
- Author
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Morgenstern, Olaf, Hegglin, Michaela I, Rozanov, Eugene, O’Connor, Fiona M, Abraham, N. Luke, Akiyoshi, Hideharu, Archibald, Alexander T, Bekki, Slimane, Butchart, Neal, Chipperfield, Martyn P, Deushi, Makoto, Dhomse, Sandip S, Garcia, Rolando R, Hardiman, Steven C, Horowitz, Larry W, Jockel, Patrick, Josse, Beatrice, Kinnison, Douglas, Lin, Meiyun, Mancini, Eva, Manyin, Michael E, Marchand, Marion, Marecal, Virginie, Michou, Martine, Oman, Luke D, Pitari, Giovanni, Plummer, David A, Revell, Laura E, Saint-Martin, David, Schofield, Robyn, Stenke, Andrea, Stone, Kane, Sudo, Kengo, Tanaka, Taichu Y, Tilmes, Simone, Yamashita, Yousuke, Yoshida, Kohei, and Zeng, Guang
- Subjects
Geosciences (General) - Abstract
We present an overview of state-of-the-art chemistry-climate and chemistry transport models that are used within phase 1 of the Chemistry-Climate Model Initiative (CCMI-1). The CCMI aims to conduct a detailed evaluation of participating models using process-oriented diagnostics derived from observations in order to gain confidence in the models' projections of the stratospheric ozone layer, tropospheric composition, air quality, where applicable global climate change, and the interactions between them. Interpretation of these diagnostics requires detailed knowledge of the radiative, chemical, dynamical, and physical processes incorporated in the models. Also an understanding of the degree to which CCMI-1 recommendations for simulations have been followed is necessary to understand model responses to anthropogenic and natural forcing and also to explain inter-model differences. This becomes even more important given the ongoing development and the ever-growing complexity of these models. This paper also provides an overview of the available CCMI-1 simulations with the aim of informing CCMI data users.
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- 2017
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27. A single-peak-structured solar cycle signal in stratospheric ozone based on Microwave Limb Sounder observations and model simulations
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Dhomse, Sandip S., primary, Chipperfield, Martyn P., additional, Feng, Wuhu, additional, Hossaini, Ryan, additional, Mann, Graham W., additional, Santee, Michelle L., additional, and Weber, Mark, additional
- Published
- 2022
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28. ML-TOMCAT: machine-learning-based satellite-corrected global stratospheric ozone profile data set from a chemical transport model
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Dhomse, Sandip S., primary, Arosio, Carlo, additional, Feng, Wuhu, additional, Rozanov, Alexei, additional, Weber, Mark, additional, and Chipperfield, Martyn P., additional
- Published
- 2021
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29. Recovery of the first ever multi-year lidar dataset of the stratospheric aerosol layer, from Lexington, MA, and Fairbanks, AK, January 1964 to July 1965
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Antuña-Marrero, Juan-Carlos, primary, Mann, Graham W., additional, Barnes, John, additional, Rodríguez-Vega, Albeht, additional, Shallcross, Sarah, additional, Dhomse, Sandip S., additional, Fiocco, Giorgio, additional, and Grams, Gerald W., additional
- Published
- 2021
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30. The recovery and re-calibration of a 13-month aerosol extinction profiles dataset from searchlight observations from New Mexico, after the 1963 Agung eruption.
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Antuña-Marrero, Juan-Carlos, Mann, Graham W., Barnes, John, Calle, Abel, Dhomse, Sandip S., Revilla, Victoria E. Cachorro, Deshler, Terry, Li Zhengyao, Sharma, Nimmi, and Elterman, Louis
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TROPOSPHERIC aerosols ,PANGAEA (Supercontinent) ,STRATOSPHERIC aerosols ,AEROSOLS ,DATA libraries ,PARTICLE size distribution ,VOLCANIC eruptions - Abstract
We report the recovery and re-calibration of an extensive dataset of vertical profile measurements of the 1963/64 stratospheric aerosol layer measured from a two-site searchlight measurement facility at White Sands missile base and Sacramento Peak observatory, in New Mexico, US. The recovered dataset comprises 105 profiles of 550nm aerosol extinction (β
p (z)) and is part of a longer program of measurements with the US Air Force Cambridge Research Laboratories (AFCRL) searchlight facility that began in February 1963. The recovered series of βp (z) profiles span the 13-month period December 1963 to December 1964 and provide a unique record of the altitude and vertical extent of the Northern Hemisphere dispersed portion of the aerosol cloud from the March 1963 Agung volcanic eruption. The data recovery methodology involved first re-digitizing the 105 original βp (z) profiles (βp (z)) from individual Figures within an AFCRL research report (Elterman, 1966a). The re-calibration involves inverting the original equation used to compute βp (z) in Elterman (1966a; 1966b) to retrieve a normalized detector response (Er (z) Er (35)) profile for each of the 105 re-digitized βp 0(z) profiles. An iterative procedure was then used to compute the re-calibration βp (z) profiles (βp Ra (z)), with the molecular extinction profile calculated with the corresponding daily molecular extinction profile calculated from local soundings, rather than the US Standard Atmosphere 1962 in the original dataset. Two-way molecular and aerosol transmittance corrections are applied using the MODTRAN (MODerate resolution atmospheric TRANsmission) code in transmission mode, applying a best-estimate aerosol phase function calculated from measurements, applied for the entire 2.76 to 35.2 km column. For the tropospheric aerosol transmittance, the AERONET aerosol phase function from White Sands High Energy Laser Systems Test Facility (HELSTF) was applied (2.76 to 10.7 km), a separate stratospheric phase function applied between 11.2 and 35.2 km, calculated from a set of particle size distributions measured by the U-2 high-altitude aircraft over a US region in the vicinity of White Sands in early 1964. Errors were estimated taking as a reference the errors determined in the computation of βp 0(z). Using available tabulated data from the original procedure the errors in the re-digitalization of βp 0(z) and in the retrieval of the Er (z) Er (35) procedures were calculated and later added to the original estimates. Both the βp R(z) and the stratospheric aerosol optical depth magnitudes showed higher magnitudes than βp 0(z) and the original stratospheric aerosol optical depth, however their magnitudes show a reasonable agreement with other contemporary observations. Both the original and recalibration datasets are being submitted to PANGAEA data repository for its storage and public access. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
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31. Model physics and chemistry causing intermodel disagreement within the VolMIP-Tambora Interactive Stratospheric Aerosol ensemble
- Author
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Clyne, Margot (author), Lamarque, Jean-Francois (author), Mills, Michael J. (author), Khodri, Myriam (author), Ball, W.T. (author), Bekki, Slimane (author), Dhomse, Sandip S. (author), Lebas, Nicolas (author), Mann, Graham (author), Clyne, Margot (author), Lamarque, Jean-Francois (author), Mills, Michael J. (author), Khodri, Myriam (author), Ball, W.T. (author), Bekki, Slimane (author), Dhomse, Sandip S. (author), Lebas, Nicolas (author), and Mann, Graham (author)
- Abstract
As part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP), several climate modeling centers performed a coordinated prestudy experiment with interactive stratospheric aerosol models simulating the volcanic aerosol cloud from an eruption resembling the 1815 Mt. Tambora eruption (VolMIP-Tambora ISA ensemble). The pre-study provided the ancillary ability to assess intermodel diversity in the radiative forcing for a large stratospheric-injecting equatorial eruption when the volcanic aerosol cloud is simulated interactively. An initial analysis of the VolMIP-Tambora ISA ensemble showed large disparities between models in the stratospheric global mean aerosol optical depth (AOD). In this study, we now show that stratospheric global mean AOD differences among the participating models are primarily due to differences in aerosol size, which we track here by effective radius. We identify specific physical and chemical processes that are missing in some models and/or parameterized differently between models, which are together causing the differences in effective radius. In particular, our analysis indicates that interactively tracking hydroxyl radical (OH) chemistry following a large volcanic injection of sulfur dioxide (SO2) is an important fac tor in allowing for the timescale for sulfate formation to be properly simulated. In addition, depending on the timescale of sulfate formation, there can be a large difference in effective radius and subsequently AOD that results from whether the SO2 is injected in a single model grid cell near the location of the volcanic eruption, or whether it is injected as a longitudinally averaged band around the Earth., Atmospheric Remote Sensing
- Published
- 2021
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32. The increasing threat to stratospheric ozone from dichloromethane
- Author
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Hossaini, Ryan, Chipperfield, Martyn P., Montzka, Stephen A., Leeson, Amber A., Dhomse, Sandip S., Pyle, John A., Hossaini, Ryan [0000-0003-2395-6657], Montzka, Stephen A [0000-0002-9396-0400], Dhomse, Sandip S [0000-0003-3854-5383], and Apollo - University of Cambridge Repository
- Subjects
Science ,0399 Other Chemical Sciences ,Article - Abstract
It is well established that anthropogenic chlorine-containing chemicals contribute to ozone layer depletion. The successful implementation of the Montreal Protocol has led to reductions in the atmospheric concentration of many ozone-depleting gases, such as chlorofluorocarbons. As a consequence, stratospheric chlorine levels are declining and ozone is projected to return to levels observed pre-1980 later this century. However, recent observations show the atmospheric concentration of dichloromethane—an ozone-depleting gas not controlled by the Montreal Protocol—is increasing rapidly. Using atmospheric model simulations, we show that although currently modest, the impact of dichloromethane on ozone has increased markedly in recent years and if these increases continue into the future, the return of Antarctic ozone to pre-1980 levels could be substantially delayed. Sustained growth in dichloromethane would therefore offset some of the gains achieved by the Montreal Protocol, further delaying recovery of Earth’s ozone layer., Chlorine-containing species deplete stratospheric ozone and while chlorofluorocarbons have been drastically reduced, dichloromethane concentrations have recently increased rapidly. Hossaini et al. show that continued growth at this rate could result in important delays to Antarctic ozone recovery.
- Published
- 2017
33. COVID-19 lockdown-induced changes in NO<sub>2</sub> levels across India observed by multi-satellite and surface observations
- Author
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Biswal, Akash, primary, Singh, Vikas, additional, Singh, Shweta, additional, Kesarkar, Amit P., additional, Ravindra, Khaiwal, additional, Sokhi, Ranjeet S., additional, Chipperfield, Martyn P., additional, Dhomse, Sandip S., additional, Pope, Richard J., additional, Singh, Tanbir, additional, and Mor, Suman, additional
- Published
- 2021
- Full Text
- View/download PDF
34. Model physics and chemistry causing intermodel disagreement within the VolMIP-Tambora Interactive Stratospheric Aerosol ensemble
- Author
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Clyne, Margot, primary, Lamarque, Jean-Francois, additional, Mills, Michael J., additional, Khodri, Myriam, additional, Ball, William, additional, Bekki, Slimane, additional, Dhomse, Sandip S., additional, Lebas, Nicolas, additional, Mann, Graham, additional, Marshall, Lauren, additional, Niemeier, Ulrike, additional, Poulain, Virginie, additional, Robock, Alan, additional, Rozanov, Eugene, additional, Schmidt, Anja, additional, Stenke, Andrea, additional, Sukhodolov, Timofei, additional, Timmreck, Claudia, additional, Toohey, Matthew, additional, Tummon, Fiona, additional, Zanchettin, Davide, additional, Zhu, Yunqian, additional, and Toon, Owen B., additional
- Published
- 2021
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35. Arctic Ozone Depletion in 2019/20: Roles of Chemistry, Dynamics and the Montreal Protocol
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Feng, Wuhu, primary, Dhomse, Sandip S., additional, Arosio, Carlo, additional, Weber, Mark, additional, Burrows, John P., additional, Santee, Michelle L., additional, and Chipperfield, Martyn P., additional
- Published
- 2021
- Full Text
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36. COVID-19 lockdown induced changes in NO2 levels across India observed by multi-satellite and surface observations
- Author
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Biswal, Akash, Singh, Vikas, Singh, Shweta, Kesarkar, Amit P., Ravindra, Khaiwal, Sokhi, Ranjeet S., Chipperfield, Martyn P., Dhomse, Sandip S., Pope, Richard J., Singh, Tanbir, and Mor, Suman
- Abstract
We have estimated the spatial changes in NO2 levels over different regions of India during the COVID-19 lockdown (25th March–3rd May 2020) using the satellite-based tropospheric column NO2 observed by the Ozone Monitoring Instrument (OMI) and the Tropospheric Monitoring Instrument (TROPOMI), as well as surface NO2 concentrations obtained from the Central Pollution Control Board (CPCB) monitoring network. A substantial reduction in NO2 levels was observed across India during the lockdown compared to the same period during previous business-as-usual years, except for some regions that were influenced by anomalous fires in 2020. The reduction (negative change) over the urban agglomerations was substantial (∼ 20–40 %) and directly proportional to the urban size and population density. Rural regions across India also experienced lower NO2 values by ∼ 15–25 %. Localised enhancement of NO2 associated with isolated emission increase scattered across India, were also detected. Observed percentage changes in satellite and surface observations were consistent across most regions and cities, but the surface observations were subject to larger variability depending on their proximity to the local emission sources. Observations also indicate NO2 enhancements of up to ∼ 25 % during the lockdown associated with fire emissions over the north-east, and some parts of central regions. In addition, the cities located near the large fire emission sources show much smaller NO2 reduction than other urban areas as the decrease at the surface was masked by enhancement in NO2 due to the transport of the fire emissions.
- Published
- 2020
37. Evaluating the simulated radiative forcings, aerosol properties, and stratospheric warmings from the 1963 Mt Agung, 1982 El Chichón, and 1991 Mt Pinatubo volcanic aerosol clouds
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Dhomse, Sandip S., primary, Mann, Graham W., additional, Antuña Marrero, Juan Carlos, additional, Shallcross, Sarah E., additional, Chipperfield, Martyn P., additional, Carslaw, Kenneth S., additional, Marshall, Lauren, additional, Abraham, N. Luke, additional, and Johnson, Colin E., additional
- Published
- 2020
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38. Effects of Reanalysis Forcing Fields on Ozone Trends from a Chemical Transport Model.
- Author
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Yajuan Li, Dhomse, Sandip S., Chipperfield, Martyn P., Wuhu Feng, Chrysanthou, Andreas, Yuan Xia, and Dong Guo
- Abstract
We use the TOMCAT 3-dimensional (3D) off-line chemical transport model (CTM) forced by two different meteorological reanalysis datasets (ERA-Interim and ERA5) from the European Centre for Medium-Range weather Forecasts (ECMWF) to study stratospheric ozone trends and variability. The model-simulated ozone variations are evaluated against two observation-based data sets. For total column ozone (TCO) we use the Copernicus Climate Change Service (C3S) data (1979-2019), while for ozone profiles we use the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) database (1984-2019). We find that the CTM simulations forced by ERA-Interim (A_ERAI) and ERA5 (B_ERA5) can both successfully reproduce spatial and temporal variations in stratospheric ozone. Modelled TCO anomalies from B_ ERA5 show better agreement with C3S than A_ERAI, especially in northern hemisphere (NH) mid-latitudes, except that it produces large positive biases (> 15 DU) during winter-spring seasons. Ozone profile comparisons against SWOOSH data show larger differences between the two simulations. In the lower stratosphere, which controls the TCO, these are primarily due to differences in transport, whereas in the upper stratosphere they can be directly attributed to the differences in temperatures between the two reanalysis data sets. Although TCO anomalies from B_ERA5 show better agreement with C3S compared to A_ERAI, comparison with SWOOSH data does not confirm that B_ERA5 performs better in simulating the stratospheric ozone profiles. We employ a multi-variate regression model with piecewise linear trends (PWLT) to quantify ozone trends before and after peak stratospheric halogen loading in 1997. This model shows that compared to C3S, TCO recovery trends (since 1998) in simulation B_ERA5 are significantly overestimated in the southern hemisphere (SH) midlatitudes, while for A_ERAI in the NH mid-latitudes simulated ozone trends remain negative. Similarly, in the lower stratosphere B_ERA5 shows positive ozone recovery trends for both NH and SH mid-latitudes. In contrast, both SWOOSH and A_ERAI show opposite (negative) trends in the NH mid-latitudes. We analyse Age-of-Air (AoA) trends to diagnose transport differences between the two reanalysis data sets. Simulation B_ERA5 shows a positive AoA trend after 1998 and somewhat older age in the NH lower stratosphere compared to A_ERAI, indicating a slower Brewer-Dobson circulation does not translate into reduced wintertime ozone build-up in the NH extratropical lower stratosphere. Overall, our results show that models forced by the most recent ERA5 reanalyses may not yet be capable of reproducing observed changes in stratospheric ozone, particularly in the lower stratosphere. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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- View/download PDF
39. Analysis and attribution of total column ozone changes over the Tibetan Plateau during 1979–2017
- Author
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Li, Yajuan, primary, Chipperfield, Martyn P., additional, Feng, Wuhu, additional, Dhomse, Sandip S., additional, Pope, Richard J., additional, Li, Faquan, additional, and Guo, Dong, additional
- Published
- 2020
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40. Description and evaluation of the UKCA stratosphere–troposphere chemistry scheme (StratTrop vn 1.0) implemented in UKESM1
- Author
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Archibald, Alexander T., primary, O'Connor, Fiona M., additional, Abraham, Nathan Luke, additional, Archer-Nicholls, Scott, additional, Chipperfield, Martyn P., additional, Dalvi, Mohit, additional, Folberth, Gerd A., additional, Dennison, Fraser, additional, Dhomse, Sandip S., additional, Griffiths, Paul T., additional, Hardacre, Catherine, additional, Hewitt, Alan J., additional, Hill, Richard S., additional, Johnson, Colin E., additional, Keeble, James, additional, Köhler, Marcus O., additional, Morgenstern, Olaf, additional, Mulcahy, Jane P., additional, Ordóñez, Carlos, additional, Pope, Richard J., additional, Rumbold, Steven T., additional, Russo, Maria R., additional, Savage, Nicholas H., additional, Sellar, Alistair, additional, Stringer, Marc, additional, Turnock, Steven T., additional, Wild, Oliver, additional, and Zeng, Guang, additional
- Published
- 2020
- Full Text
- View/download PDF
41. Clear-sky ultraviolet radiation modelling using output from the Chemistry Climate Model Initiative
- Author
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Lamy, Kévin, Portafaix, Thierry, Josse, Béatrice, Brogniez, Colette, Godin-Beekmann, Sophie, Bencherif, Hassan, Revell, Laura, Akiyoshi, Hideharu, Bekki, Slimane, Hegglin, Michaela I., Jöckel, Patrick, Kirner, Oliver, Liley, Ben, Marecal, Virginie, Morgenstern, Olaf, Stenke, Andrea, Zeng, Guang, Abraham, N. Luke, Archibald, Alexander T., Butchart, Neil, Chipperfield, Martyn P., Di Genova, Glauco, Deushi, Makoto, Dhomse, Sandip S., Hu, Rong-Ming, Kinnison, Douglas, Kotkamp, Michael, McKenzie, Richard, Michou, Martine, O&, apos, Connor, Fiona M., Oman, Luke D., Pitari, Giovanni, Plummer, David A., Pyle, John A., Rozanov, Eugene, Saint-Martin, David, Sudo, Kengo, Tanaka, Taichu Y., Visioni, Daniele, and Yoshida, Kohei
- Subjects
DATA processing & computer science ,ddc:004 - 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.
- Published
- 2019
42. A Single-Peak-Structured Solar Cycle Signal in Stratospheric Ozone based on Microwave Limb Sounder Observations and Model Simulations.
- Author
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Dhomse, Sandip S., Chipperfield, Martyn P., Wuhu Feng, Hossaini, Ryan, Mann, Graham W., Santee, Michelle L., and Weber, Mark
- Abstract
Until now our understanding of the 11-year solar cycle signal (SCS) in stratospheric ozone has been largely based on high quality but sparse ozone profiles from the Stratospheric Aerosol and Gas Experiment (SAGE) II or coarsely resolved ozone profiles from the nadir-viewing Solar Backscatter Ultraviolet Radiometer (SBUV) satellite instruments. Here, we analyse 16 years (2005-2020) of ozone profile measurements from the Microwave Limb Sounder (MLS) instrument on the Aura satellite to estimate the 11-year SCS in stratospheric ozone. Our analysis of Aura-MLS data suggests a single-peak-structured SCS profile (about 3% near 4 hPa or 40 km) in tropical stratospheric ozone, which is significantly different to the SAGE II and SBUV-based double-peak-structured SCS. We also find that MLS-observed ozone variations are more consistent with ozone from our control model simulation that uses Naval Research Laboratory (NRL) v2 solar fluxes. However, in the lowermost stratosphere modelled ozone shows a negligible SCS compared to about 1% in Aura-MLS data. An ensemble of Ordinary Least Square (OLS) and three regularised (Lasso, Ridge and ElasticNet) linear regression models confirms the robustness of the estimated SCS. Our analysis of MLS and model simulations also shows a large SCS in the Antarctic lower stratosphere that was not seen in earlier studies. We also analyse chemical transport model simulations with alternative solar flux data. We find that in the upper (and middle) stratosphere the model simulation with Solar Radiation and Climate Experiment (SORCE) satellite solar fluxes is also consistent with the MLS-derived SCS and agrees well with the control simulation and one which uses Spectral and Total Irradiance Reconstructions (SATIRE) solar fluxes. Hence, our model simulation suggests that with recent adjustments and corrections, SORCE solar fluxes can be used to analyse effects of solar flux variations. Finally, we argue that the overall significantly different SCS compared to earlier estimates might be due to a combination of different factors such as much denser MLS measurements, almost linear stratospheric chlorine loading changes over the analysis period, as well as a stratospheric aerosol layer relatively unperturbed by major volcanic eruptions. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
43. ML-TOMCAT: Machine-Learning-Based Satellite-Corrected Global Stratospheric Ozone Profile Dataset from a Chemical Transport Model.
- Author
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Dhomse, Sandip S., Arosio, Carlo, Feng, Wuhu, Rozanov, Alexei, Weber, Mark, and Chipperfield, Martyn P.
- Subjects
- *
OZONE layer , *CHEMICAL models , *UPPER atmosphere , *ATMOSPHERIC models , *NATURAL satellite atmospheres , *OZONE - Abstract
High quality stratospheric ozone profile datasets are a key requirement for accurate quantification and attribution of long-term ozone changes. Satellite instruments obtain stratospheric ozone profile measurements over typical mission durations of 5-15 years. Various methodologies have then been applied to merge and homogenise the different satellite data in order to create longer term observation-based ozone profile datasets with minimal data gaps. However, individual satellite instruments use different measurement methods, sampling patterns and retrieval algorithms which complicate the merging of these different datasets. In contrast, atmospheric chemical models can produce chemically consistent long-term ozone simulations based on specified changes in external forcings, but they are subject to the deficiencies associated with incomplete understanding of complex atmospheric processes and uncertain photochemical parameters. Here, we use chemically self-consistent output from the TOMCAT 3-D chemical transport model (CTM) and a Random-Forest (RF) ensemble learning method to create a merged 42-year (1979-2020) stratospheric ozone profile dataset (ML-TOMCAT V1.0). The underlying CTM simulation was forced by meteorological reanalyses, specified trends in long-lived source gas, solar flux and aerosol variations. The RF is trained using the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) dataset over the time periods of the Microwave Limb Sounder (MLS) from the Upper Atmosphere Research Satellite (UARS) (1991-1998) and Aura (2005-2016) missions. We find that ML-TOMCAT shows excellent agreement with available independent satellite-based datasets which use pressure as the vertical coordinate (e.g. GOZCARDS, SWOOSH for non-MLS periods) but weaker agreement with the datasets which are height-based (e.g. SAGE-CCI-OMPS, SCIAMACHY-OMPS). We find that at almost all stratospheric levels ML-TOMCAT ozone concentrations are well within uncertainties in the observational datasets. The ML-TOMCAT dataset is thus ideally suited for the evaluation of model ozone profiles from the tropopause to 0.1 hPa. ML-TOMCAT data is freely available via https://zenodo.org/record/4997959#.YNzleUlKiUk (Dhomse et al., 2021). [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
44. Estimates of ozone return dates from Chemistry-Climate Model Initiative simulations
- Author
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Dhomse, Sandip S., Kinnison, Douglas, Chipperfield, Martyn P., Salawitch, Ross J., Cionni, Irene, Hegglin, Michaela I., Abraham, N. Luke, Akiyoshi, Hideharu, Archibald, Alex T., Bednarz, Ewa M., Bekki, Slimane, Braesicke, Peter, Butchart, Neal, Dameris, Martin, Deushi, Makoto, Frith, Stacey, Hardiman, Steven C., Hassler, Birgit, Horowitz, Larry W., Hu, Rong-Ming, Jöckel, Patrick, Josse, Beatrice, Kirner, Oliver, Kremser, Stefanie, Langematz, Ulrike, Lewis, Jared, Marchand, Marion, Lin, Meiyun, Mancini, Eva, Marécal, Virginie, Michou, Martine, Morgenstern, Olaf, O&, apos, Connor, Fiona M., Oman, Luke, Pitari, Giovanni, Plummer, David A., Pyle, John A., Revell, Laura E., Rozanov, Eugene, Schofield, Robyn, Stenke, Andrea, Stone, Kane, Sudo, Kengo, Tilmes, Simone, Visioni, Daniele, Yamashita, Yousuke, and Zeng, Guang
- Subjects
DATA processing & computer science ,ddc:004 - Published
- 2018
45. Clear-sky ultraviolet radiation modelling using output from the Chemistry Climate Model Initiative
- Author
-
Lamy, Kévin, primary, Portafaix, Thierry, additional, Josse, Béatrice, additional, Brogniez, Colette, additional, Godin-Beekmann, Sophie, additional, Bencherif, Hassan, additional, Revell, Laura, additional, Akiyoshi, Hideharu, additional, Bekki, Slimane, additional, Hegglin, Michaela I., additional, Jöckel, Patrick, additional, Kirner, Oliver, additional, Liley, Ben, additional, Marecal, Virginie, additional, Morgenstern, Olaf, additional, Stenke, Andrea, additional, Zeng, Guang, additional, Abraham, N. Luke, additional, Archibald, Alexander T., additional, Butchart, Neil, additional, Chipperfield, Martyn P., additional, Di Genova, Glauco, additional, Deushi, Makoto, additional, Dhomse, Sandip S., additional, Hu, Rong-Ming, additional, Kinnison, Douglas, additional, Kotkamp, Michael, additional, McKenzie, Richard, additional, Michou, Martine, additional, O'Connor, Fiona M., additional, Oman, Luke D., additional, Pitari, Giovanni, additional, Plummer, David A., additional, Pyle, John A., additional, Rozanov, Eugene, additional, Saint-Martin, David, additional, Sudo, Kengo, additional, Tanaka, Taichu Y., additional, Visioni, Daniele, additional, and Yoshida, Kohei, additional
- Published
- 2019
- Full Text
- View/download PDF
46. Dynamically controlled ozone decline in the tropical mid-stratosphere observed by SCIAMACHY
- Author
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Galytska, Evgenia, primary, Rozanov, Alexey, additional, Chipperfield, Martyn P., additional, Dhomse, Sandip. S., additional, Weber, Mark, additional, Arosio, Carlo, additional, Feng, Wuhu, additional, and Burrows, John P., additional
- Published
- 2019
- Full Text
- View/download PDF
47. Stratospheric ozone loss in the Arctic winters between 2005 and 2013 derived with ACE-FTS measurements
- Author
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Griffin, Debora, primary, Walker, Kaley A., additional, Wohltmann, Ingo, additional, Dhomse, Sandip S., additional, Rex, Markus, additional, Chipperfield, Martyn P., additional, Feng, Wuhu, additional, Manney, Gloria L., additional, Liu, Jane, additional, and Tarasick, David, additional
- Published
- 2019
- Full Text
- View/download PDF
48. Stratospheric Injection of Brominated Very Short-Lived Substances:Aircraft Observations in the Western Pacific and Representation in Global Models
- Author
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Wales, Pamela A., Salawitch, Ross J., Nicely, Julie M., Anderson, Daniel C., Canty, Timothy P., Baidar, Sunil, Dix, Barbara, Koenig, Theodore K., Volkamer, Rainer, Chen, Dexian, Huey, L. Gregory, Tanner, David J., Cuevas, Carlos A., Fernandez, Rafael P., Kinnison, Douglas E., Lamarque, Jean-francois, Saiz-lopez, Alfonso, Atlas, Elliot L., Hall, Samuel R., Navarro, Maria A., Pan, Laura L., Schauffler, Sue M., Stell, Meghan, Tilmes, Simone, Ullmann, Kirk, Weinheimer, Andrew J., Akiyoshi, Hideharu, Chipperfield, Martyn P., Deushi, Makoto, Dhomse, Sandip S., Feng, Wuhu, Graf, Phoebe, Hossaini, Ryan, Jöckel, Patrick, Mancini, Eva, Michou, Martine, Morgenstern, Olaf, Oman, Luke D., Pitari, Giovanni, Plummer, David A., Revell, Laura E., Rozanov, Eugene, Saint-martin, David, Schofield, Robyn, Stenke, Andrea, Stone, Kane A., Visioni, Daniele, Yamashita, Yousuke, Zeng, Guang, Wales, Pamela A., Salawitch, Ross J., Nicely, Julie M., Anderson, Daniel C., Canty, Timothy P., Baidar, Sunil, Dix, Barbara, Koenig, Theodore K., Volkamer, Rainer, Chen, Dexian, Huey, L. Gregory, Tanner, David J., Cuevas, Carlos A., Fernandez, Rafael P., Kinnison, Douglas E., Lamarque, Jean-francois, Saiz-lopez, Alfonso, Atlas, Elliot L., Hall, Samuel R., Navarro, Maria A., Pan, Laura L., Schauffler, Sue M., Stell, Meghan, Tilmes, Simone, Ullmann, Kirk, Weinheimer, Andrew J., Akiyoshi, Hideharu, Chipperfield, Martyn P., Deushi, Makoto, Dhomse, Sandip S., Feng, Wuhu, Graf, Phoebe, Hossaini, Ryan, Jöckel, Patrick, Mancini, Eva, Michou, Martine, Morgenstern, Olaf, Oman, Luke D., Pitari, Giovanni, Plummer, David A., Revell, Laura E., Rozanov, Eugene, Saint-martin, David, Schofield, Robyn, Stenke, Andrea, Stone, Kane A., Visioni, Daniele, Yamashita, Yousuke, and Zeng, Guang
- Abstract
We quantify the stratospheric injection of brominated very short‐lived substances (VSLS) based on aircraft observations acquired in winter 2014 above the Tropical Western Pacific during the CONvective TRansport of Active Species in the Tropics (CONTRAST) and the Airborne Tropical TRopopause EXperiment (ATTREX) campaigns. The overall contribution of VSLS to stratospheric bromine was determined to be 5.0 ± 2.1 ppt, in agreement with the 5 ± 3 ppt estimate provided in the 2014 World Meteorological Organization (WMO) Ozone Assessment report (WMO 2014), but with lower uncertainty. Measurements of organic bromine compounds, including VSLS, were analyzed using CFC‐11 as a reference stratospheric tracer. From this analysis, 2.9 ± 0.6 ppt of bromine enters the stratosphere via organic source gas injection of VSLS. This value is two times the mean bromine content of VSLS measured at the tropical tropopause, for regions outside of the Tropical Western Pacific, summarized in WMO 2014. A photochemical box model, constrained to CONTRAST observations, was used to estimate inorganic bromine from measurements of BrO collected by two instruments. The analysis indicates that 2.1 ± 2.1 ppt of bromine enters the stratosphere via inorganic product gas injection. We also examine the representation of brominated VSLS within 14 global models that participated in the Chemistry‐Climate Model Initiative. The representation of stratospheric bromine in these models generally lies within the range of our empirical estimate. Models that include explicit representations of VSLS compare better with bromine observations in the lower stratosphere than models that utilize longer‐lived chemicals as a surrogate for VSLS.
- Published
- 2018
49. The Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP): Motivation and experimental design
- Author
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Timmreck, Claudia, Mann, Graham W., Aquila, Valentina, Hommel, Rene, Lee, Lindsay A., Schmidt, Anja, Brühl, Christoph, Carn, Simon, Chin, Mian, Dhomse, Sandip S., Diehl, Thomas, English, Jason M., Mills, Michael J., Neely, Ryan, Sheng, Jianxiong, Toohey, Matthew, Weisenstein, Debra, Timmreck, Claudia, Mann, Graham W., Aquila, Valentina, Hommel, Rene, Lee, Lindsay A., Schmidt, Anja, Brühl, Christoph, Carn, Simon, Chin, Mian, Dhomse, Sandip S., Diehl, Thomas, English, Jason M., Mills, Michael J., Neely, Ryan, Sheng, Jianxiong, Toohey, Matthew, and Weisenstein, Debra
- Abstract
The Stratospheric Sulfur and its Role in Climate (SSiRC) interactive stratospheric aerosol model intercomparison project (ISA-MIP) explores uncertainties in the processes that connect volcanic emission of sulphur gas species and the radiative forcing associated with the resulting enhancement of the stratospheric aerosol layer. The central aim of ISA-MIP is to constrain and improve interactive stratospheric aerosol models and reduce uncertainties in the stratospheric aerosol forcing by comparing results of standardized model experiments with a range of observations. In this paper we present 4 co-ordinated inter-model experiments designed to investigate key processes which influence the formation and temporal development of stratospheric aerosol in different time periods of the observational record. The "Background" (BG) experiment will focus on microphysics and transport processes under volcanically quiescent conditions, when the stratospheric aerosol is controlled by the transport of aerosols and their precursors from the troposphere to the stratosphere. The "Transient Aerosol Record" (TAR) experiment will explore the role of small- to moderate-magnitude volcanic eruptions, anthropogenic sulphur emissions and transport processes over the period 1998–2012 and their role in the warming hiatus. Two further experiments will investigate the stratospheric sulphate aerosol evolution after major volcanic eruptions. The "Historical Eruptions SO2 Emission Assessment" (HErSEA) experiment will focus on the uncertainty in the initial emission of recent large-magnitude volcanic eruptions, while the "Pinatubo Emulation in Multiple models" (PoEMS) experiment will provide a comprehensive uncertainty analysis of the radiative forcing from the 1991 Mt. Pinatubo eruption.
- Published
- 2018
- Full Text
- View/download PDF
50. Stratospheric Injection of Brominated Very Short-Lived Substances : Aircraft Observations in the Western Pacific and Representation in Global Models
- Author
-
Wales, Pamela A., Salawitch, Ross J., Nicely, Julie M., Anderson, Daniel C., Canty, Timothy P., Baidar, Sunil, Dix, Barbara, Koenig, Theodore K., Volkamer, Rainer, Chen, Dexian, Huey, L. Gregory, Tanner, David J., Cuevas, Carlos A., Fernandez, Rafael P., Kinnison, Douglas E., Lamarque, Jean-francois, Saiz-lopez, Alfonso, Atlas, Elliot L., Hall, Samuel R., Navarro, Maria A., Pan, Laura L., Schauffler, Sue M., Stell, Meghan, Tilmes, Simone, Ullmann, Kirk, Weinheimer, Andrew J., Akiyoshi, Hideharu, Chipperfield, Martyn P., Deushi, Makoto, Dhomse, Sandip S., Feng, Wuhu, Graf, Phoebe, Hossaini, Ryan, Jöckel, Patrick, Mancini, Eva, Michou, Martine, Morgenstern, Olaf, Oman, Luke D., Pitari, Giovanni, Plummer, David A., Revell, Laura E., Rozanov, Eugene, Saint-martin, David, Schofield, Robyn, Stenke, Andrea, Stone, Kane A., Visioni, Daniele, Yamashita, Yousuke, Zeng, Guang, Wales, Pamela A., Salawitch, Ross J., Nicely, Julie M., Anderson, Daniel C., Canty, Timothy P., Baidar, Sunil, Dix, Barbara, Koenig, Theodore K., Volkamer, Rainer, Chen, Dexian, Huey, L. Gregory, Tanner, David J., Cuevas, Carlos A., Fernandez, Rafael P., Kinnison, Douglas E., Lamarque, Jean-francois, Saiz-lopez, Alfonso, Atlas, Elliot L., Hall, Samuel R., Navarro, Maria A., Pan, Laura L., Schauffler, Sue M., Stell, Meghan, Tilmes, Simone, Ullmann, Kirk, Weinheimer, Andrew J., Akiyoshi, Hideharu, Chipperfield, Martyn P., Deushi, Makoto, Dhomse, Sandip S., Feng, Wuhu, Graf, Phoebe, Hossaini, Ryan, Jöckel, Patrick, Mancini, Eva, Michou, Martine, Morgenstern, Olaf, Oman, Luke D., Pitari, Giovanni, Plummer, David A., Revell, Laura E., Rozanov, Eugene, Saint-martin, David, Schofield, Robyn, Stenke, Andrea, Stone, Kane A., Visioni, Daniele, Yamashita, Yousuke, and Zeng, Guang
- Abstract
We quantify the stratospheric injection of brominated very short‐lived substances (VSLS) based on aircraft observations acquired in winter 2014 above the Tropical Western Pacific during the CONvective TRansport of Active Species in the Tropics (CONTRAST) and the Airborne Tropical TRopopause EXperiment (ATTREX) campaigns. The overall contribution of VSLS to stratospheric bromine was determined to be 5.0 ± 2.1 ppt, in agreement with the 5 ± 3 ppt estimate provided in the 2014 World Meteorological Organization (WMO) Ozone Assessment report (WMO 2014), but with lower uncertainty. Measurements of organic bromine compounds, including VSLS, were analyzed using CFC‐11 as a reference stratospheric tracer. From this analysis, 2.9 ± 0.6 ppt of bromine enters the stratosphere via organic source gas injection of VSLS. This value is two times the mean bromine content of VSLS measured at the tropical tropopause, for regions outside of the Tropical Western Pacific, summarized in WMO 2014. A photochemical box model, constrained to CONTRAST observations, was used to estimate inorganic bromine from measurements of BrO collected by two instruments. The analysis indicates that 2.1 ± 2.1 ppt of bromine enters the stratosphere via inorganic product gas injection. We also examine the representation of brominated VSLS within 14 global models that participated in the Chemistry‐Climate Model Initiative. The representation of stratospheric bromine in these models generally lies within the range of our empirical estimate. Models that include explicit representations of VSLS compare better with bromine observations in the lower stratosphere than models that utilize longer‐lived chemicals as a surrogate for VSLS.
- Published
- 2018
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