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Claudia Timmreck - One of the best experts on this subject based on the ideXlab platform.
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easy Volcanic Aerosol eva v1 0 an idealized forcing generator for climate simulations
Geoscientific Model Development, 2016Co-Authors: Matthew Toohey, Hauke Schmidt, Bjorn Stevens, Claudia TimmreckAbstract:Abstract. Stratospheric sulfate Aerosols from Volcanic eruptions have a significant impact on the Earth's climate. To include the effects of Volcanic eruptions in climate model simulations, the Easy Volcanic Aerosol (EVA) forcing generator provides stratospheric Aerosol optical properties as a function of time, latitude, height, and wavelength for a given input list of Volcanic eruption attributes. EVA is based on a parameterized three-box model of stratospheric transport and simple scaling relationships used to derive mid-visible (550 nm) Aerosol optical depth and Aerosol effective radius from stratospheric sulfate mass. Precalculated look-up tables computed from Mie theory are used to produce wavelength-dependent Aerosol extinction, single scattering albedo, and scattering asymmetry factor values. The structural form of EVA and the tuning of its parameters are chosen to produce best agreement with the satellite-based reconstruction of stratospheric Aerosol properties following the 1991 Pinatubo eruption, and with prior millennial-timescale forcing reconstructions, including the 1815 eruption of Tambora. EVA can be used to produce Volcanic forcing for climate models which is based on recent observations and physical understanding but internally self-consistent over any timescale of choice. In addition, EVA is constructed so as to allow for easy modification of different aspects of Aerosol properties, in order to be used in model experiments to help advance understanding of what aspects of the Volcanic Aerosol are important for the climate system.
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Easy Volcanic Aerosol (EVA v1.0): An idealized forcing generator for climate simulations
2016Co-Authors: Matthew Toohey, Hauke Schmidt, Bjorn Stevens, Claudia TimmreckAbstract:Abstract. The Easy Volcanic Aerosol (EVA) forcing generator produces stratospheric Aerosol optical properties as a function of time, latitude, height and wavelength for a given input list of Volcanic eruption attributes. EVA is based on a parameterized three-box model of stratospheric transport, and simple scaling relationships used to derive mid-visible (550 nm) Aerosol optical depth and Aerosol effective radius from stratospheric sulfate mass. Pre-calculated look up tables computed from Mie theory are used to produce wavelength dependent Aerosol extinction, single scattering albedo and scattering asymmetry factor values. The structural form of EVA, and the tuning of its parameters, are chosen to produce best agreement with the satellite-based reconstruction of stratospheric Aerosol properties following the 1991 Pinatubo eruption, and with prior millennial-time scale forcing reconstructions including the 1815 eruption of Tambora. EVA can be used to produce Volcanic forcing for climate models which is based on recent observations and physical understanding, but internally self-consistent over any time-scale of choice. In addition, EVA is constructed so as to allow for easy modification of different aspects of Aerosol properties, in order to be used in model experiments to help advance understanding of what aspects of the Volcanic Aerosol are important for the climate system.
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The impact of stratospheric Volcanic Aerosol on decadal-scale climate predictions
Geophysical Research Letters, 2016Co-Authors: Claudia Timmreck, Holger Pohlmann, Sebastian Illing, Christopher KadowAbstract:To understand the impact of Volcanic Aerosol on multiyear seasonal and decadal climate predictions, we performed Coupled Model Intercomparison Project Phase 5-type hindcasts without Volcanic Aerosol using the German Mittelfristige Klimaprognosen prediction system and compared them to the corresponding simulations including Aerosols. Our results show that Volcanic Aerosol significantly affects the prediction skill for global mean surface air temperature in the first five years after strong Volcanic eruptions. Also, on the regional scale a Volcanic imprint on decadal-scale variability is detectable. Neglecting Volcanic Aerosol leads to a reduced prediction skill over the tropical and subtropical Atlantic, Indic, and west Pacific but to an improvement over the tropical east Pacific, where the model has in general no skill. Multiseasonal differences in the skill for seasonal mean temperatures are evident over Continental Europe with significant skill loss due to neglection of Volcanic Aerosol in boreal winter over central Europe, Scandinavia and over southeastern Europe, and the East Mediterranean in boreal summer.
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The impact of Volcanic Aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure
Atmospheric Chemistry and Physics, 2014Co-Authors: M. Toohey, Claudia Timmreck, Kirstin Krüger, Matthias Bittner, Hauke SchmidtAbstract:Abstract. Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH) stratospheric polar vortex is stronger in winters following major Volcanic eruptions. However, recent studies show that climate models forced by prescribed Volcanic Aerosol fields fail to reproduce this effect. We investigate the impact of Volcanic Aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric Aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled Aerosol–climate model simulations. For all forcings, we find that simulated temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous Volcanic Aerosol heating. Instead, high-latitude effects result from enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High-latitude effects are therefore much less robust than would be expected if they were the direct result of Aerosol heating. Both observation-based forcing sets result in insignificant changes in vortex strength. For the model-based forcing sets, the vortex response is found to be sensitive to the structure of the forcing, with one forcing set leading to significant strengthening of the polar vortex in rough agreement with observation-based expectations. Differences in the dynamical response to the forcing sets imply that reproducing the polar vortex responses to past eruptions, or predicting the response to future eruptions, depends on accurate representation of the space–time structure of the Volcanic Aerosol forcing.
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simulation of mt pinatubo Volcanic Aerosol with the hamburg climate model echam4
Theoretical and Applied Climatology, 1999Co-Authors: Claudia Timmreck, Hansf Graf, Johann FeichterAbstract:We study the three-dimensional transport of Mt. Pinatubo Volcanic cloud with the climate model ECHAM4. In order to obtain model results comparable with observations a Newtonian relaxation technique was applied, which forces prognostic model variables towards the observations. A comparison of the simulated Aerosol distribution with satellite data reveals good agreement for the first months after the eruption. The model, however, is unable to simulate the tropical Aerosol maximum in 1992 and also overestimates the vertical downward and northward transport of Aerosols. Substantial improvement was achieved with the introduction of reduced advective vertical transport through the 380 K isentropic layer. Heating rates and top of the atmosphere fluxes, which were calculated online for the first half year after the eruption, are in the observed range. A comparison of Pinatubo simulations between three different vertical ECHAM4 versions (ECHAM4 L19, ECHAM4 L39, MA/ECHAM4) indicates that a vertical resolution of ≈ 700 m in the tropopause region is sufficient to realistically reduce the vertical transport through the tropopause. Consideration of the upper branch of the Brewer Dobson circulation in the MA/ECHAM4 model improves the geographical distribution of the Volcanic cloud. The application of a relaxation technique can further reduce major shortcomings of stratospheric simulations with the standard climate model. There remain, however some critical points in the global transport characteristics in all three models which are not fully understood.
Andreas Stohl - One of the best experts on this subject based on the ideXlab platform.
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Volcanic Aerosol optical properties and phase partitioning behavior after long range advection characterized by uv lidar measurements
Atmospheric Environment, 2012Co-Authors: Alain Miffre, G David, Benjamin Thomas, P Rairoux, A M Fjaeraa, N I Kristiansen, Andreas StohlAbstract:Abstract In this paper, an UV-polarization Lidar is used to study the optical properties of Volcanic Aerosol in the troposphere. The particles were released by the mid-April 2010 eruption of the Eyjafjallajokull volcano (63.63°N, 19.62°W, Iceland) and passed in the troposphere above Lyon (45.76°N, 4.83°E, France) after advection over 2600 km. The FLEXPART particle dispersion model was applied to simulate the Volcanic ash transport from Iceland to South West Europe, at the border of the air traffic closure area. Time-altitude plots of FLEXPART ash concentrations as well as of Aerosol backscattering are presented, showing the arrival of Volcanic particles in the troposphere above Lyon and their mixing into the planetary boundary layer. The particle UV-backscattering coefficient was typically 4 Mm−1 sr−1 and highly sensitive and accurate particle UV-depolarization measurements were performed, with depolarization ranging from a few to 44%. After few days long-range transport, observed ash particles are still non spherical. The observed variations of the backscattering and depolarization coefficients can be attributed to variations in the Volcanic particles content. Ash mass concentrations are then retrieved. Moreover, a partitioning into spherical and non spherical particles is evaluated from number concentration ratios between solid ash particles and spherical hydrated sulfate particles. The microphysical properties of Volcanic particles can thus be studied by associating an UV-polarization remote sensing instrument with a numerical Volcanic ash dispersion model.
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Volcanic Aerosol optical properties and phase partitioning behavior after long-range advection characterized by UV-Lidar measurements
Atmospheric environment, 2011Co-Authors: Alain Miffre, G David, Benjamin Thomas, P Rairoux, A M Fjaeraa, N I Kristiansen, Andreas StohlAbstract:In this paper, an UV-polarization Lidar is used to study the optical properties of Volcanic Aerosol in the troposphere. The particles were released by the mid-April 2010 eruption of the Eyjafjallajökull volcano (63.63°N, 19.62°W, Iceland) and passed in the troposphere above Lyon (45.76°N, 4.83°E, France) after advection over 2600 km. The FLEXPART particle dispersion model was applied to simulate the Volcanic ash transport from Iceland to South West Europe, at the border of the air traffic closure area. Time-altitude plots of FLEXPART ash concentrations as well as of Aerosol backscattering are presented, showing the arrival of Volcanic particles in the troposphere above Lyon and their mixing into the planetary boundary layer. The particle UV-backscattering coefficient was typically 4 Mm−1 sr−1 and highly sensitive and accurate particle UV-depolarization measurements were performed, with depolarization ranging from a few to 44%. After few days long-range transport, observed ash particles are still non spherical. The observed variations of the backscattering and depolarization coefficients can be attributed to variations in the Volcanic particles content. Ash mass concentrations are then retrieved. Moreover, a partitioning into spherical and non spherical particles is evaluated from number concentration ratios between solid ash particles and spherical hydrated sulfate particles. The microphysical properties of Volcanic particles can thus be studied by associating an UV-polarization remote sensing instrument with a numerical Volcanic ash dispersion model. Highlights - Volcanic ash particles concentration is measured by ground-based Lidar in troposphere. - Coupling with FLEXPART ash transport model allows to identify Volcanic ash particles. - Precise UV-depolarization data allows to discern spherical/non spherical particles. - Phase partitioning between non spherical ash and spherical sulfates is thus evaluated. - After long-range advection, PBL ash particles are low concentrated and still aspheric.
S T Massie - One of the best experts on this subject based on the ideXlab platform.
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global evolution of the mt pinatubo Volcanic Aerosols observed by the infrared limb sounding instruments claes and isams on the upper atmosphere research satellite
Journal of Geophysical Research, 1997Co-Authors: A Lambert, R G Grainger, C D Rodgers, F W Taylor, J L Mergenthaler, J B Kumer, S T MassieAbstract:The cryogenic limb array etalon spectrometer (CLAES) and the improved stratospheric and mesospheric sounder (ISAMS) instruments on board the Upper Atmosphere Research Satellite (UARS) have been used to produce global information on the Mt. Pinatubo Volcanic Aerosol for the period from October 1991 to April 1993. The satellite infrared extinction measurements near 12 μm are converted into the Aerosol-related parameters necessary for modelling the effects of the Volcanic Aerosol on the aeronomy of the stratosphere and are presented as zonal mean distributions for 80°S to 80°N averaged over ∼35-day periods. The Aerosol composition is derived from the CLAES and ISAMS temperature measurements and the water vapour abundances are obtained from the microwave limb sounder (MLS). The Aerosol volume density is obtained from the extinction measurements from which the surface area density and the effective particle radius are estimated. The maximum Aerosol surface area density has a value of about 50 μm 2 cm -3 at a height of 24 km at the equator in October 1991, before decaying exponentially with a time constant of 443 ± 10 days. The surface area density remained well above preeruption values in April 1993. The effective particle radius in the tropics decays monotonically from 0.65 μm in October 1991 to 0.4 μm in April 1993. The global Aerosol sulphate mass loading is 19.5 Mt in October 1991 and decays exponentially with a time constant of 342 ± 8 days to a value of 4.3 Mt by April 1993. Four months after the eruption the calculated optical thickness at 1.02 μm was ∼0.25 in the tropics. Rate constants are derived for the heterogeneous reactions of N 2 O 5 and ClONO 2 on the sulphate Aerosols. The application of the Aerosol parameters to the investigation of tracer transport, heterogeneous chemistry, and radiative transfer is discussed.
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Global evolution of the Mt. Pinatubo Volcanic Aerosols observed by the infrared limb‐sounding instruments CLAES and ISAMS on the Upper Atmosphere Research Satellite
Journal of Geophysical Research: Atmospheres, 1997Co-Authors: Alyn Lambert, Fredric W. Taylor, Roy G. Grainger, Clive D. Rodgers, J L Mergenthaler, J B Kumer, S T MassieAbstract:The cryogenic limb array etalon spectrometer (CLAES) and the improved stratospheric and mesospheric sounder (ISAMS) instruments on board the Upper Atmosphere Research Satellite (UARS) have been used to produce global information on the Mt. Pinatubo Volcanic Aerosol for the period from October 1991 to April 1993. The satellite infrared extinction measurements near 12 μm are converted into the Aerosol-related parameters necessary for modelling the effects of the Volcanic Aerosol on the aeronomy of the stratosphere and are presented as zonal mean distributions for 80°S to 80°N averaged over ∼35-day periods. The Aerosol composition is derived from the CLAES and ISAMS temperature measurements and the water vapour abundances are obtained from the microwave limb sounder (MLS). The Aerosol volume density is obtained from the extinction measurements from which the surface area density and the effective particle radius are estimated. The maximum Aerosol surface area density has a value of about 50 μm 2 cm -3 at a height of 24 km at the equator in October 1991, before decaying exponentially with a time constant of 443 ± 10 days. The surface area density remained well above preeruption values in April 1993. The effective particle radius in the tropics decays monotonically from 0.65 μm in October 1991 to 0.4 μm in April 1993. The global Aerosol sulphate mass loading is 19.5 Mt in October 1991 and decays exponentially with a time constant of 342 ± 8 days to a value of 4.3 Mt by April 1993. Four months after the eruption the calculated optical thickness at 1.02 μm was ∼0.25 in the tropics. Rate constants are derived for the heterogeneous reactions of N 2 O 5 and ClONO 2 on the sulphate Aerosols. The application of the Aerosol parameters to the investigation of tracer transport, heterogeneous chemistry, and radiative transfer is discussed.
John Remedios - One of the best experts on this subject based on the ideXlab platform.
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properties of northern hemisphere polar stratospheric clouds and Volcanic Aerosol in 1991 92 from uars isams satellite measurements
Journal of the Atmospheric Sciences, 1994Co-Authors: Fredric W. Taylor, Alyn Lambert, Roy G. Grainger, Clive D. Rodgers, John RemediosAbstract:Abstract Observations of polar stratospheric clouds by the Improved Stratospheric and Mesospheric Sounder (ISAMS) experiment on the Upper Atmospheric Research Satellite (UARS) have revealed new details of their global properties and behavior. These include the vertical and horizontal spatial distributions of Arctic and Antarctic polar stratospheric clouds (PSCs) as a function of time and air temperature, their optical thicknesses and estimated densities, their spectral properties, and their inferred composition. In particular, ISAMS spectral data allows different PSC types to be distinguished from each other and from Volcanic Aerosol by their compositional differences. Northern PSCs during the 1991/92 season are found to be more ephemeral and more compact than reported in previous years and to differ markedly in scale from those in the Southern Hemisphere, which cause the Antarctic ozone hole by activating stratospheric chlorine chemistry. There were only two episodes of dense PSC formation in the 1991/92...
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Properties of Northern Hemisphere polar stratospheric clouds and Volcanic Aerosol in 1991-92 from UARS/ISAMS satellite measurements
Journal of the Atmospheric Sciences, 1994Co-Authors: Fredric W. Taylor, Alyn Lambert, Roy G. Grainger, Clive D. Rodgers, John RemediosAbstract:Abstract Observations of polar stratospheric clouds by the Improved Stratospheric and Mesospheric Sounder (ISAMS) experiment on the Upper Atmospheric Research Satellite (UARS) have revealed new details of their global properties and behavior. These include the vertical and horizontal spatial distributions of Arctic and Antarctic polar stratospheric clouds (PSCs) as a function of time and air temperature, their optical thicknesses and estimated densities, their spectral properties, and their inferred composition. In particular, ISAMS spectral data allows different PSC types to be distinguished from each other and from Volcanic Aerosol by their compositional differences. Northern PSCs during the 1991/92 season are found to be more ephemeral and more compact than reported in previous years and to differ markedly in scale from those in the Southern Hemisphere, which cause the Antarctic ozone hole by activating stratospheric chlorine chemistry. There were only two episodes of dense PSC formation in the 1991/92...
Fredric W. Taylor - One of the best experts on this subject based on the ideXlab platform.
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Global evolution of the Mt. Pinatubo Volcanic Aerosols observed by the infrared limb‐sounding instruments CLAES and ISAMS on the Upper Atmosphere Research Satellite
Journal of Geophysical Research: Atmospheres, 1997Co-Authors: Alyn Lambert, Fredric W. Taylor, Roy G. Grainger, Clive D. Rodgers, J L Mergenthaler, J B Kumer, S T MassieAbstract:The cryogenic limb array etalon spectrometer (CLAES) and the improved stratospheric and mesospheric sounder (ISAMS) instruments on board the Upper Atmosphere Research Satellite (UARS) have been used to produce global information on the Mt. Pinatubo Volcanic Aerosol for the period from October 1991 to April 1993. The satellite infrared extinction measurements near 12 μm are converted into the Aerosol-related parameters necessary for modelling the effects of the Volcanic Aerosol on the aeronomy of the stratosphere and are presented as zonal mean distributions for 80°S to 80°N averaged over ∼35-day periods. The Aerosol composition is derived from the CLAES and ISAMS temperature measurements and the water vapour abundances are obtained from the microwave limb sounder (MLS). The Aerosol volume density is obtained from the extinction measurements from which the surface area density and the effective particle radius are estimated. The maximum Aerosol surface area density has a value of about 50 μm 2 cm -3 at a height of 24 km at the equator in October 1991, before decaying exponentially with a time constant of 443 ± 10 days. The surface area density remained well above preeruption values in April 1993. The effective particle radius in the tropics decays monotonically from 0.65 μm in October 1991 to 0.4 μm in April 1993. The global Aerosol sulphate mass loading is 19.5 Mt in October 1991 and decays exponentially with a time constant of 342 ± 8 days to a value of 4.3 Mt by April 1993. Four months after the eruption the calculated optical thickness at 1.02 μm was ∼0.25 in the tropics. Rate constants are derived for the heterogeneous reactions of N 2 O 5 and ClONO 2 on the sulphate Aerosols. The application of the Aerosol parameters to the investigation of tracer transport, heterogeneous chemistry, and radiative transfer is discussed.
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properties of northern hemisphere polar stratospheric clouds and Volcanic Aerosol in 1991 92 from uars isams satellite measurements
Journal of the Atmospheric Sciences, 1994Co-Authors: Fredric W. Taylor, Alyn Lambert, Roy G. Grainger, Clive D. Rodgers, John RemediosAbstract:Abstract Observations of polar stratospheric clouds by the Improved Stratospheric and Mesospheric Sounder (ISAMS) experiment on the Upper Atmospheric Research Satellite (UARS) have revealed new details of their global properties and behavior. These include the vertical and horizontal spatial distributions of Arctic and Antarctic polar stratospheric clouds (PSCs) as a function of time and air temperature, their optical thicknesses and estimated densities, their spectral properties, and their inferred composition. In particular, ISAMS spectral data allows different PSC types to be distinguished from each other and from Volcanic Aerosol by their compositional differences. Northern PSCs during the 1991/92 season are found to be more ephemeral and more compact than reported in previous years and to differ markedly in scale from those in the Southern Hemisphere, which cause the Antarctic ozone hole by activating stratospheric chlorine chemistry. There were only two episodes of dense PSC formation in the 1991/92...
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Properties of Northern Hemisphere polar stratospheric clouds and Volcanic Aerosol in 1991-92 from UARS/ISAMS satellite measurements
Journal of the Atmospheric Sciences, 1994Co-Authors: Fredric W. Taylor, Alyn Lambert, Roy G. Grainger, Clive D. Rodgers, John RemediosAbstract:Abstract Observations of polar stratospheric clouds by the Improved Stratospheric and Mesospheric Sounder (ISAMS) experiment on the Upper Atmospheric Research Satellite (UARS) have revealed new details of their global properties and behavior. These include the vertical and horizontal spatial distributions of Arctic and Antarctic polar stratospheric clouds (PSCs) as a function of time and air temperature, their optical thicknesses and estimated densities, their spectral properties, and their inferred composition. In particular, ISAMS spectral data allows different PSC types to be distinguished from each other and from Volcanic Aerosol by their compositional differences. Northern PSCs during the 1991/92 season are found to be more ephemeral and more compact than reported in previous years and to differ markedly in scale from those in the Southern Hemisphere, which cause the Antarctic ozone hole by activating stratospheric chlorine chemistry. There were only two episodes of dense PSC formation in the 1991/92...
