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  • 1
    Electronic Resource
    Electronic Resource
    Climate and CCN (1995)
    [s.l.] : Nature Publishing Group
    Nature 375 (1995), S. 111-111 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] TOUMI ET AL. REPLY - We agree with the points raised by Rodhe and Crutzen. However, we still maintain that the main uncertainty is the relationship between H2SO4 and cloud droplets and not the extent to which H2SO4 production has changed. We are encouraged by a recent modelling ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/375111b0
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Indirect influence of ozone depletion on climate forcing by clouds (1994)
    [s.l.] : Nature Publishing Group
    Nature 372 (1994), S. 348-351 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The hydroxyl radical is primarily produced by the photodisso-ciation of ozone (O3) by radiation of wavelength near 310 nm in the presence of water vapour. O3+H2O+hv 2OH+O2 OH can then initiate the oxidation of SO2 to sulphuric acid. The production rate, R, of sulphuric acid is thought to be a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/372348a0
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A model study of ATMOS observations and the heterogeneous loss of N2O5 by the sulphate aerosol layer (1993)
    Springer
    Journal of atmospheric chemistry 16 (1993), S. 135-144 
    Details
    ISSN: 1573-0662
    Keywords: Ozone ; ATMOS ; stratosphere ; N2O5 ; aerosol layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The heterogeneous removal of N2O5 by sulphuric acid aerosols as been invoked to explain the decline of mid-latitude ozone in the last decade. We have used a photochemical model to study measurements of odd-nitrogen made by Spacelab 3. The gas-phase photochemical model overestimates the amount of N2O5 present. The loss of N2O5 by aerosols does reduce N2O5, but is likely to be slower than assumed in WMO (1992). The sunset measurements at 25.5 km cannot be explained by heterogeneous loss of N2O5 and is more likely to be due to a faster photolysis than assumed. New absorption cross-sections of HNO3 reduce the photolysis of HNO3 so that the model with gas-phase chemistry only gives better agreement at 19 km, than a model including heterogeneous chemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702783
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    Paper (German National Licenses)
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  • 4
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    Multi-model comparison of the volcanic sulfate deposition from the 1815 eruption of Mt. Tambora (2018)
    Copernicus Publications (EGU)
    In:  Atmospheric Chemistry and Physics, 18 (3). pp. 2307-2328.
    Details
    Publication Date: 2021-02-08
    Description: The eruption of Mt. Tambora in 1815 was the largest volcanic eruption of the past 500 years. The eruption had significant climatic impacts, leading to the 1816 "year without a summer", and remains a valuable event from which to understand the climatic effects of large stratospheric volcanic sulfur dioxide injections. The eruption also resulted in one of the strongest and most easily identifiable volcanic sulfate signals in polar ice cores, which are widely used to reconstruct the timing and atmospheric sulfate loading of past eruptions. As part of the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP), five state-of-the-art global aerosol models simulated this eruption. We analyse both simulated background (no Tambora) and volcanic (with Tambora) sulfate deposition to polar regions and compare to ice core records. The models simulate overall similar patterns of background sulfate deposition, al-though there are differences in regional details and magnitude. However, the volcanic sulfate deposition varies considerably between the models with differences in timing, spatial pattern and magnitude. Mean simulated deposited sulfate on Antarctica ranges from 19 to 264 kgkm-2 and on Greenland from 31 to 194 kgkm-2, as compared to the mean ice-corederived estimates of roughly 50 kgkm-2 for both Greenland and Antarctica. The ratio of the hemispheric atmospheric sulfate aerosol burden after the eruption to the average ice sheet deposited sulfate varies between models by up to a factor of 15. Sources of this inter-model variability include differences in both the formation and the transport of sulfate aerosol. Our results suggest that deriving relationships between sulfate deposited on ice sheets and atmospheric sulfate burdens from model simulations may be associated with greater uncertainties than previously thought.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.5194/acp-18-2307-2018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    The Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP): experimental design and forcing input data for CMIP6 (2016)
    Copernicus Publications (EGU)
    In:  Geoscientific Model Development, 9 . pp. 2701-2719.
    Details
    Publication Date: 2019-02-01
    Description: The enhancement of the stratospheric aerosol layer by volcanic eruptions induces a complex set of responses causing global and regional climate effects on a broad range of timescales. Uncertainties exist regarding the climatic response to strong volcanic forcing identified in coupled climate simulations that contributed to the fifth phase of the Coupled Model Intercomparison Project (CMIP5). In order to better understand the sources of these model diversities, the Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP) has defined a coordinated set of idealized volcanic perturbation experiments to be carried out in alignment with the CMIP6 protocol. VolMIP provides a common stratospheric aerosol data set for each experiment to minimize differences in the applied volcanic forcing. It defines a set of initial conditions to assess how internal climate variability contributes to determining the response. VolMIP will assess to what extent volcanically forced responses of the coupled ocean–atmosphere system are robustly simulated by state-of-the-art coupled climate models and identify the causes that limit robust simulated behavior, especially differences in the treatment of physical processes. This paper illustrates the design of the idealized volcanic perturbation experiments in the VolMIP protocol and describes the common aerosol forcing input data sets to be used.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.5194/gmd-9-2701-2016
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    The representation of solar cycle signals in stratospheric ozone. Part II: Analysis of global models (2018)
    Copernicus Publications (EGU)
    In:  Atmospheric Chemistry and Physics, 18 . pp. 11323-11343.
    Details
    Publication Date: 2021-02-08
    Description: The impact of changes in incoming solar irradiance on stratospheric ozone abundances should be included in climate simulations to aid in capturing the atmospheric response to solar cycle variability. This study presents the first systematic comparison of the representation of the 11-year solar cycle ozone response (SOR) in chemistry–climate models (CCMs) and in pre-calculated ozone databases specified in climate models that do not include chemistry, with a special focus on comparing the recommended protocols for the Coupled Model Intercomparison Project Phase 5 and Phase 6 (CMIP5 and CMIP6). We analyse the SOR in eight CCMs from the Chemistry–Climate Model Initiative (CCMI-1) and compare these with results from three ozone databases for climate models: the Bodeker Scientific ozone database, the SPARC/Atmospheric Chemistry and Climate (AC&C) ozone database for CMIP5 and the SPARC/CCMI ozone database for CMIP6. The peak amplitude of the annual mean SOR in the tropical upper stratosphere (1–5hPa) decreases by more than a factor of 2, from around 5 to 2%, between the CMIP5 and CMIP6 ozone databases. This substantial decrease can be traced to the CMIP5 ozone database being constructed from a regression model fit to satellite and ozonesonde measurements, while the CMIP6 database is constructed from CCM simulations. The SOR in the CMIP6 ozone database therefore implicitly resembles the SOR in the CCMI-1 models. The structure in latitude of the SOR in the CMIP6 ozone database and CCMI-1 models is considerably smoother than in the CMIP5 database, which shows unrealistic sharp gradients in the SOR across the middle latitudes owing to the paucity of long-term ozone measurements in polar regions. The SORs in the CMIP6 ozone database and the CCMI-1 models show a seasonal dependence with enhanced meridional gradients at mid- to high latitudes in the winter hemisphere. The CMIP5 ozone database does not account for seasonal variations in the SOR, which is unrealistic. Sensitivity experiments with a global atmospheric model without chemistry (ECHAM6.3) are performed to assess the atmospheric impacts of changes in the representation of the SOR and solar spectral irradiance (SSI) forcing between CMIP5 and CMIP6. The larger amplitude of the SOR in the CMIP5 ozone database compared to CMIP6 causes a likely overestimation of the modelled tropical stratospheric temperature response between 11-year solar cycle minimum and maximum by up to 0.55K, or around 80% of the total amplitude. This effect is substantially larger than the change in temperature response due to differences in SSI forcing between CMIP5 and CMIP6. The results emphasize the importance of adequately representing the SOR in global models to capture the impact of the 11-year solar cycle on the atmosphere. Since a number of limitations in the representation of the SOR in the CMIP5 ozone database have been identified, we recommend that CMIP6 models without chemistry use the CMIP6 ozone database and the CMIP6 SSI dataset to better capture the climate impacts of solar variability. The SOR coefficients from the CMIP6 ozone database are published with this paper.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.5194/acp-18-11323-2018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Model physics and chemistry causing intermodel disagreement within the VolMIP-Tambora Interactive Stratospheric Aerosol ensemble (2021)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-02-07
    Description: 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.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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