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  • ddc:551.5  (11)
  • ddc:551  (4)
  • Biostratigraphie  (2)
  • English  (17)
  • German
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  • 2020-2023  (15)
  • 1995-1999  (2)
  • 1
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    Biostratigraphy in Production and Development Geology (1999)
    London : The Geological Society
    Details
    Keywords: Biostratigraphie ; Erdölgeologie ; Bioestratigrafia ; Biostratigraphie ; Geology, Economic ; Geology, Stratigraphic ; Géologie économique ; Micropaleontologia ; Paleontology, Stratigraphic ; Petroleum ; Prospecting ; Prospecção geológica ; Pétrole - Géologie ; Stratigraphie
    Description / Table of Contents: R. W. Jones and M. D. Simmons: Preface and Introduction / Geological Society, London, Special Publications, 152:1-3, doi:10.1144/GSL.SP.1999.152.01.01 --- S. N. J. Payne, D. F. Ewen, and M. J. Bowman: The role and value of ‘high-impact biostratigraphy’ in reservoir appraisal and development / Geological Society, London, Special Publications, 152:5-22, doi:10.1144/GSL.SP.1999.152.01.02 --- S. Duxbury, D. Kadolsky, and S. Johansen: Sequence stratigraphic subdivision of the Humber Group in the Outer Moray Firth area (UKCS, North Sea) / Geological Society, London, Special Publications, 152:23-54, doi:10.1144/GSL.SP.1999.152.01.03 --- P. H. Morris, S. N. J. Payne, and D. P. J. Richards: Micropalaeontological biostratigraphy of the Magnus Sandstone Member (Kimmeridgian-Early Volgian), Magnus Field, UK North Sea / Geological Society, London, Special Publications, 152:55-73, doi:10.1144/GSL.SP.1999.152.01.04 --- D. J. Shipp: Well-site biostratigraphy of Danish horizontal wells / Geological Society, London, Special Publications, 152:75-84, doi:10.1144/GSL.SP.1999.152.01.05 --- J. A. Bergen and P. J. Sikora: Microfossil diachronism in southern Norwegian North Sea chalks: Valhall and Hod fields / Geological Society, London, Special Publications, 152:85-111, doi:10.1144/GSL.SP.1999.152.01.06 --- P. J. Sikora, J. A. Bergen, and C. L. Farmer: Chalk palaeoenvironments and depositional model, Valhall-Hod fields, southern Norwegian North Sea / Geological Society, London, Special Publications, 152:113-137, doi:10.1144/GSL.SP.1999.152.01.07 --- M. D. Bidgood, A. G. Mitlehner, G. D. Jones, and D. J. Jutson: Towards a stable and agreed nomenclature for North Sea Tertiary diatom floras — the ‘Coscinodiscus’ problem / Geological Society, London, Special Publications, 152:139-153, doi:10.1144/GSL.SP.1999.152.01.08 --- N. A. Holmes: The Andrew Formation and ‘biosteering’ — different reservoirs, different approaches / Geological Society, London, Special Publications, 152:155-166, doi:10.1144/GSL.SP.1999.152.01.09 --- G. Mangerud, T. Dreyer, L. Søyseth, O. Martinsen, and A. Ryseth: High-resolution biostratigraphy and sequence development of the Palaeocene succession, Grane Field, Norway / Geological Society, London, Special Publications, 152:167-184, doi:10.1144/GSL.SP.1999.152.01.10 --- R. W. Jones: Forties Field (North Sea) revisited: a demonstration of the value of historical micropalaeontological data / Geological Society, London, Special Publications, 152:185-200, doi:10.1144/GSL.SP.1999.152.01.11 --- D. McLean and S. J. Davies: Constraints on the application of palynology to the correlation of Euramerican Late Carboniferous clastic hydrocarbon reservoirs / Geological Society, London, Special Publications, 152:201-218, doi:10.1144/GSL.SP.1999.152.01.12 --- M. D. Simmons, M. D. Bidgood, P. Brenac, P. D. Crevello, J. J. Lambiase, and C. K. Morley: Microfossil assemblages as proxies for precise palaeoenvironmental determination — an example from Miocene sediments of northwest Borneo / Geological Society, London, Special Publications, 152:219-241, doi:10.1144/GSL.SP.1999.152.01.13 --- R. W. Jones, N. E. Jones, A. D. King, and D. Shaw: Reservoir biostratigraphy of the Pedernales Field, Venezuela / Geological Society, London, Special Publications, 152:243-257, doi:10.1144/GSL.SP.1999.152.01.14 --- J. M. Armentrout, L. B. Fearn, K. Rodgers, S. Root, W. D. Lyle, D. C. Herrick, R. B. Bloch, J. W. Snedden, and B. Nwankwo: High-resolution sequence biostratigraphy of a lowstand prograding deltaic wedge: Oso Field (late Miocene), Nigeria / Geological Society, London, Special Publications, 152:259-290, doi:10.1144/GSL.SP.1999.152.01.15 --- C. J. Van Der Zwan and W. A. Brugman: Biosignals from the EA Field, Nigeria / Geological Society, London, Special Publications, 152:291-301, doi:10.1144/GSL.SP.1999.152.01.16 --- B. J. O’Neill, A. E. DuVernay, and R. A. George: Applied palaeontology: a critical stratigraphic tool in Gulf of Mexico exploration and exploitation / Geological Society, London, Special Publications, 152:303-308, doi:10.1144/GSL.SP.1999.152.01.17
    Pages: Online-Ressource (318 Seiten) , Illustrationen, Diagramme ; 25cm + fold out charts
    ISBN: 1862390312
    URL: http://sp.lyellcollection.org/content/152/1
    Language: English
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  • 2
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    Stochastic Modeling Approach to Identify Uncertainties of Karst Conduit Networks in Carbonate Aquifers (2022)
    Details
    Publication Date: 2022-12-07
    Description: The characterization of the karst conduit network is an essential task to understand the complex flow system within karst aquifers. However, this task is challenging and often associated with uncertainty. Equivalent porous media approaches for modeling flow in karst aquifers fall short of capturing the hydraulic effect of individual karst features, while process‐oriented karst evolution models imply major computational efforts. In this study, we apply the Stochastic Karst Simulator (SKS) developed by Borghi et al. (2012) to generate karst conduit networks at a regional scale of a highly karstified carbonate aquifer located in the Eastern Mediterranean region and extensively used for water supply. The SKS generates conduit network geometries reasonably quick, using a mathematical proxy that mimics conduit evolution. The conduit simulation is based on a conceptual model of the genesis of the aquifer, consisting of different karstification phases. The stochastic approach of the algorithm enables us to generate an ensemble of conduit network realizations and to represent the uncertainties of these simulations in a Karst Probability Map. With only soft input information to constrain conduit evolution, multiple equivalent realizations yield similar resulting network geometries, indicating a robust approach. The presented methodology is numerically efficient, and its input can be easily adjusted. Subsequently, the resulting stochastic spatial distribution of conductivities can be employed for the parametrization of regional karst groundwater models.
    Description: Key Points: We statistically generate multiple sets of karst conduit network geometries using input data based on soft information. The resulting Karst Probability Map accounts for uncertainty in the spatial distribution of the karst conduit network. Our approach can assist in the integration of soft information into the parametrization of karst groundwater models.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: https://doi.org/10.14279/depositonce-16021
    Keywords: ddc:551 ; karst conduit modeling ; stochastic modeling ; structural uncertainty ; karst probability mapping ; groundwater modeling
    Language: English
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  • 3
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    Algorithmic Differentiation for Sensitivity Analysis in Cloud Microphysics (2022)
    Details
    Publication Date: 2022-10-04
    Description: The role of clouds for radiative transfer, precipitation formation, and their interaction with atmospheric dynamics depends strongly on cloud microphysics. The parameterization of cloud microphysical processes in weather and climate models is a well‐known source of uncertainties. Hence, robust quantification of this uncertainty is mandatory. Sensitivity analysis to date has typically investigated only a few model parameters. We propose algorithmic differentiation (AD) as a tool to detect the magnitude and timing at which a model state variable is sensitive to any of the hundreds of uncertain model parameters in the cloud microphysics parameterization. AD increases the computational cost by roughly a third in our simulations. We explore this methodology as the example of warm conveyor belt trajectories, that is, air parcels rising rapidly from the planetary boundary layer to the upper troposphere in the vicinity of an extratropical cyclone. Based on the information of derivatives with respect to the uncertain parameters, the ten parameters contributing most to uncertainty are selected. These uncertain parameters are mostly related to the representation of hydrometeor diameter and fall velocity, the activation of cloud condensation nuclei, and heterogeneous freezing. We demonstrate the meaningfulness of the AD‐estimated sensitivities by comparing the AD results with ensemble simulations spawned at different points along the trajectories, where different parameter settings are used in the various ensemble members. The ranking of the most important parameters from these ensemble simulations is consistent with the results from AD. Thus, AD is a helpful tool for selecting parameters contributing most to cloud microphysics uncertainty.
    Description: Plain Language Summary: The formation of clouds is determined by processes that act on smaller scales than weather prediction models can resolve. Consequently, a parameterization with typically hundreds of parameters is constructed to determine the effects of these processes on the resolved larger scales. These parameters are a well‐known source of uncertainty in weather and climate models. Classical attempts to quantify this uncertainty are typically limited to a few parameters. We propose algorithmic differentiation (AD) as a tool to detect parameters with the largest impact for any of the hundreds of parameters on multiple model state variables at every time step in our simulation. This increases the computational cost by roughly a third. The relevance of the AD‐estimated impact is demonstrated by comparing the AD results with ensemble simulations, where different parameter settings are used in the various ensemble members. The ranking of the most important parameters from these ensemble simulations is consistent with the results from AD. Thus, AD is a helpful tool to identify parameters objectively that contribute most to uncertainty in cloud parameterizations.
    Description: Key Points: Quantification of multi‐parameter uncertainty of cloud microphysical evolution of WCB trajectories using algorithmic differentiation. Uncertainty at every time step derived with algorithmic differentiation representative for key uncertainty over at least 30 min intervals. Parameterization of CCN activation, diameter size, and fall velocity of hydrometeors have the largest mean impact on water vapor contents.
    Description: Deutsch Forschungsgemeinschaft DFG
    Keywords: ddc:551.5
    Language: English
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  • 4
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    Basin‐scale estimates of greenhouse gas emissions from the Mara River, Kenya: Importance of discharge, stream size, and land use/land cover (2022)
    Mwanake, Ricky M. ; Gettel, Gretchen M. ; Ishimwe, Clarisse ; [et al.]
    John Wiley & Sons, Inc. | Hoboken, USA
    Details
    Publication Date: 2022-10-04
    Description: Greenhouse gas fluxes (CO2, CH4, and N2O) from African streams and rivers are under‐represented in global datasets, resulting in uncertainties in their contributions to regional and global budgets. We conducted year‐long sampling of 59 sites in a nested‐catchment design in the Mara River, Kenya in which fluxes were quantified and their underlying controls assessed. We estimated annual basin‐scale greenhouse gas emissions from measured in‐stream gas concentrations, modeled gas transfer velocities, and determined the sensitivity of up‐scaling to discharge. Based on the total annual CO2‐equivalent emissions calculated from global warming potentials (GWP), the Mara basin was a net greenhouse gas source (294 ± 35 Gg CO2 eq yr−1). Lower‐order streams (1–3) contributed 81% of the total fluxes, and higher stream orders (4–8) contributed 19%. Cropland‐draining streams also exhibited higher fluxes compared to forested streams. Seasonality in stream discharge affected stream widths (and stream area) and gas exchange rates, strongly influencing the basin‐wide annual flux, which was 10 times higher during the high and medium discharge periods than the low discharge period. The basin‐wide estimate was underestimated by up to 36% if discharge was ignored, and up to 37% for lower stream orders. Future research should therefore include seasonality in stream surface areas in upscaling procedures to better constrain basin‐wide fluxes. Given that agricultural activities are a major factor increasing riverine greenhouse gas fluxes in the study region, increased conversion of forests and agricultural intensification has the possibility of increasing the contribution of the African continent to global greenhouse gas sources.
    Description: Deutscher Akademischer Austauschdienst http://dx.doi.org/10.13039/501100001655
    Description: IHE Delft Institute for Water Education
    Description: Federal Ministry of Education and Research http://dx.doi.org/10.13039/501100002347
    Description: Helmholtz Association http://dx.doi.org/10.13039/501100009318
    Description: TERENO Bavarian Alps/ Pre‐Alps Observatory
    Keywords: ddc:551
    Language: English
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  • 5
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    Global‐Scale Ionospheric Tomography During the March 17, 2015 Geomagnetic Storm (2021)
    Details
    Publication Date: 2022-03-24
    Description: The correct representation of global‐scale electron density is crucial for monitoring and exploring the space weather. This study investigates whether the ground‐based Global Navigation Satellite System (GNSS) tomography can be used to reflect the global spatial and temporal responses of the ionosphere under storm conditions. A global tomography of the ionosphere electron density is constructed based on data from over 2,700 GNSS stations. In comparison to previous techniques, advances are made in spatial and temporal resolution, and in the assessment of results. To demonstrate the capabilities of the approach, the developed method is applied to the March 17, 2015 geomagnetic storm. The tomographic reconstructions show good agreement with electron density observations from worldwide ionosondes, Millstone Hill incoherent scatter radar and in‐situ measurements from satellite missions. Also, the results show that the tomographic technique is capable of reproducing plasma variabilities during geomagnetically disturbed periods including features such as equatorial ionization anomaly enhancements and depletion. Validation results of this brief study period show that the accuracy of our tomography is better than the Neustrelitz Electron Density Model, which is the model used as background, and physics‐based thermosphere‐ionosphere‐electrodynamics general circulation model. The results show that our tomography approach allows us to specify the global electron density from ground to ∼900 km accurately. Given the demonstrated quality, this global electron density reconstruction has potential for improving applications such as assessment of the effects of the electron density on radio signals, GNSS positioning, computation of ray tracing for radio‐signal transmission, and space weather monitoring.
    Description: Plain Language Summary: Computerized tomography allows the 3D imaging of several objects based on radio frequency signal measurements. Given the measurements and geometry of the current GPS (Global Positioning System) satellite constellation, there is an opportunity to apply tomography techniques and extract 3D snapshots of the Earth's atmosphere. This work presents an advanced global‐scale tomography that can represent the electron density in the Earth's upper atmosphere in a relatively high spatial and temporal resolution in the region of ∼100–1,000 km above the Earth's surface; referred to as the ionosphere. The work also validates the tomography results with multiple ionospheric observations from satellites and ground‐based radar instruments and compares with empirical and physical models. It is usually a challenge for models to reproduce the ionospheric system dynamics accurately during active space weather conditions, such as geomagnetic storms. This work, using the severe geomagnetic storm on March 17, 2015 as a case‐study, shows that the tomography is well poised for this task. The developed method could be extended to benefit several applications, such as space weather monitoring, GPS positioning and navigation, as well as to improve our understanding of the morphology and dynamics of the ionosphere.
    Description: Key Points: Presents an advanced global‐scale tomography of ionospheric electron density. Demonstrates the capability of the tomography model to reproduce the system dynamics during a severe geomagnetic storm. Validates the tomography results with multiple ground‐ and space‐based data and compares with empirical and physical models.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: Helmholtz‐Fonds (Helmholtz‐Fonds e.V.) http://dx.doi.org/10.13039/501100013655
    Keywords: ddc:551.5 ; ddc:538.7
    Language: English
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  • 6
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    Induced Magnetic Fields and Plasma Motions in the Inner Part of the Martian Magnetosphere (2021)
    Details
    Publication Date: 2022-03-24
    Description: Analysis of Mars Atmosphere and Volatile Evolution (MAVEN)/Supra‐Thermal And Thermal Ion Composition observations in the Martian upper atmosphere, bounded at higher altitudes by the shocked solar wind, shows that the draping of interplanetary magnetic field penetrates down to low altitudes (∼200−250 km) and governs dynamics of the ionosphere. The upper ionospheric plasma is driven into motion flowing around Mars similar to the shocked solar wind in the adjacent magnetosheath. Such a fluid‐like motion is accompanied by ion acceleration caused by the bending of the magnetic field, leading to ion extraction and finally to ion pickup. Extraction of ions and their acceleration produces a recoil effect of the bulk ionosphere in the opposite direction. This provides a strong asymmetry in ion dynamics in two different hemispheres, accompanied by wrapping of the magnetic field lines around Mars and respective reconnection.
    Description: Plain Language Summary: Although the Martian magnetosphere is hybrid and contains components of the induced and intrinsic magnetosphere, is possible to display these components by using the specific coordinate systems. Here we study the properties of the induced magnetosphere using the data obtained by MAVEN spacecraft. The interplanetary magnetic field penetrates deep into the Martian ionosphere draping around Mars and drive to the motion dense ionospheric plasma. Draping features and the induced plasma motions occur different in two hemispheres determined by the direction of the motional electric field in the solar wind. Ion acceleration and extraction is accompanied by a recoil effect that leads to a shift and asymmetry of the ionosphere.
    Description: Key Points: Draping of the interplanetary magnetic field around Mars penetrates deep to the ionosphere enveloping the planet and driving the ionosphere to the bulk motion. Draping and motion of the ionospheric plasma is characterized by asymmetry by the direction of the motional electric field in solar wind. Ion acceleration and extraction from the ionosphere is accompanied by a shift of the bulk ionosphere in the opposite direction.
    Description: National Aeronautics and Space Administration http://dx.doi.org/10.13039/100000104
    Description: DFG http://dx.doi.org/10.13039/501100001659
    Description: Russian Science Foundation http://dx.doi.org/10.13039/501100006769
    Keywords: ddc:523 ; ddc:551.5
    Language: English
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  • 7
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    Effective buoyancy and CAPE: Some implications for tropical cyclones (2022)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2022-10-04
    Description: We review the widely used concepts of “buoyancy” and “convective available potential energy” (CAPE) in relation to deep convection in tropical cyclones and discuss their limitations. A fact easily forgotten in applying these concepts is that the buoyancy force of an air parcel, as often defined, is non‐unique because it depends on the arbitrary definition of a reference density field. However, when calculating CAPE, the buoyancy of a lifted air parcel is related to the specific reference density field along a vertical column passing through that parcel. Both concepts can be generalized for a vortical flow and to slantwise ascent of a lifted air parcel in such a flow. In all cases, the air parcel is assumed to have infinitely small dimensions. In this article, we explore the consequences of generalizing buoyancy and CAPE for buoyant regions of finite size that perturb the pressure field in their immediate environment. Quantitative calculations of effective buoyancy, defined as the sum of the conventional buoyancy and the static vertical perturbation pressure gradient force induced by it, are shown for buoyant regions of finite width. For a judicious choice of reference density, the effective buoyancy per unit mass is essentially a unique force, independent of the reference density, but its distribution depends on the horizontal scale of the buoyant region. A corresponding concept of “effective CAPE” is introduced and its relevance to deep convection in tropical cyclones is discussed. The study is conceived as a first step to understanding the decreasing ability of inner‐core deep convection in tropical cyclones to ventilate the mass of air converging in the frictional boundary layer as the vortex matures and decays.
    Description: The buoyancy force of an infinitesimally small air parcel is non‐unique, depending on the arbitrary definition of a reference density field. When calculating the “convective available potential energy” (CAPE), the buoyancy of a lifted air parcel is related to the reference density field along a vertical column passing through that parcel. We generalize buoyancy and CAPE for buoyant regions of finite size that perturb the pressure field in their immediate environment and discuss the relevance to deep convection in tropical cyclones.
    Keywords: ddc:551.5
    Language: English
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  • 8
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    Variability in the Concentration of Lithium in the Indo‐Pacific Ocean (2022)
    Details
    Publication Date: 2022-10-04
    Description: Lithium has limited biological activity and can readily replace aluminium, magnesium and iron ions in aluminosilicates, making it a proxy for the inorganic silicate cycle and its potential link to the carbon cycle. Data from the North Pacific Ocean, tropical Indian Ocean, Southern Ocean and Red Sea suggest that salinity normalized dissolved lithium concentrations vary by up to 2%–3% in the Indo‐Pacific Ocean. The highest lithium concentrations were measured in surface waters of remote North Pacific and Indian Ocean stations that receive relatively high fluxes of dust. The lowest dissolved lithium concentrations were measured just below the surface mixed layer of the stations with highest surface water concentrations, consistent with removal into freshly forming aluminium rich phases and manganese oxides. In the North Pacific, water from depths 〉2,000 m is slightly depleted in lithium compared to the initial composition of Antarctic Bottom Water, likely due to uptake of lithium by authigenically forming aluminosilicates. The results of this study suggest that the residence time of lithium in the ocean may be significantly shorter than calculated from riverine and hydrothermal fluxes.
    Description: Key Points: Li/Na ratios vary by up to 2%–3% in the Indian and Pacific Oceans. Authigenic formation of aluminosilicates slightly deplete deep‐water lithium concentrations in the North Pacific. The residence time of lithium in the ocean is 240,000 ± 70,000 years, based on removal from North Pacific deep‐water.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: MoES, Indian National Centre for Ocean Information Services http://dx.doi.org/10.13039/501100004814
    Description: National Science Foundation USA
    Description: https://doi.pangaea.de/10.1594/PANGAEA.941888
    Keywords: ddc:551
    Language: English
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  • 9
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    Modeling the Transport and Deposition of 10Be Produced by the Strongest Solar Proton Event During the Holocene (2022)
    Details
    Publication Date: 2022-10-06
    Description: Prominent excursions in the number of cosmogenic nuclides (e.g., 10Be) around 774 CE/775 document the most severe solar proton event (SPE) throughout the Holocene. Its manifestation in ice cores is valuable for geochronology, but also for solar‐terrestrial physics and climate modeling. Using the ECHAM/MESSy Atmospheric Chemistry (EMAC) climate model in combination with the Warning System for Aviation Exposure to SEP (WASAVIES), we investigate the transport, mixing, and deposition of the cosmogenic nuclide 10Be produced by the 774 CE/775 SPE. By comparing the model results to the reconstructed 10Be time series from four ice core records, we study the atmospheric pathways of 10Be from its stratospheric source to its sink at Earth's surface. The reconstructed post‐SPE evolution of the 10Be surface fluxes at the ice core sites is well captured by the model. The downward transport of the 10Be atoms is controlled by the Brewer‐Dobson circulation in the stratosphere and cross‐tropopause transport via tropopause folds or large‐scale sinking. Clear hemispheric differences in the transport and deposition processes are identified. In both polar regions the 10Be surface fluxes peak in summertime, with a larger influence of wet deposition on the seasonal 10Be surface flux in Greenland than in Antarctica. Differences in the peak 10Be surface flux following the 774 CE/775 SPE at the drilling sites are explained by specific meteorological conditions depending on the geographic locations of the sites.
    Description: Plain Language Summary: During large solar storms, high energy particles are hurled with enormous force toward Earth by the Sun. As these particles collide with atmospheric constituents (such as oxygen or nitrogen) unique nuclides of cosmogenic origin are formed in the higher atmosphere. From there they are transported downwards and finally precipitate at the surface due to different sink processes. Their imprints can be conserved over thousands of years within natural archives, such as ice cores or tree rings. Analysis of these natural archives around the globe indicates that the strongest solar storm over the last 10.000 years happened around 774 CE/775. This event is estimated to have been up to two orders of magnitude stronger, than the strongest known events documented for the satellite era. In this study, we model and analyze the transport and deposition of the cosmogenic nuclides produced by the extreme 774 CE/775 event, by applying a new experimental setup. Our results might help to interpret the fingerprints of historical extreme events with respect to the prevailing atmospheric conditions.
    Description: Key Points: The modeled transport and deposition of the cosmogenic nuclide10Be produced by the 774/775 solar proton event was compared to 10Be ice core records. Hemispheric differences in stratospheric and cross‐tropopause transport, and deposition were identified, with polar summertime maxima of 10Be surface flux. Differences in reconstructed10Be surface fluxes are explained by the local ratio of wet to dry deposition maximizing in the summertime.
    Description: MEXT Japan Society for the Promotion of Science http://dx.doi.org/10.13039/501100001691
    Keywords: ddc:551.5
    Language: English
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    The effect of stochastically perturbed parametrisation tendencies (SPPT) on rapidly ascending air streams (2022)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2022-10-06
    Description: The stochastically perturbed parametrisation tendency (SPPT) scheme is a well‐established technique in ensemble forecasting to address model uncertainty by introducing perturbations into the tendencies provided by the physics parametrisations. The magnitude of the perturbations scales with the local net parametrisation tendency, resulting in large perturbations where diabatic processes are active. Rapidly ascending air streams, such as warm conveyor belts (WCBs) and organized tropical convection, are often driven by cloud diabatic processes and are therefore prone to such perturbations. This study investigates the effects of SPPT and initial condition perturbations on rapidly ascending air streams by computing trajectories in sensitivity experiments with the European Centre for Medium‐Range Weather Forecasts (ECMWF) ensemble prediction system, which are set up to disentangle the effects of initial conditions and physics perturbations. The results demonstrate that SPPT systematically increases the frequency of rapidly ascending air streams. The effect is observed globally, but is enhanced in regions where the latent heating along the trajectories is larger. Despite the frequency changes, there are only minor modifications to the physical properties of the trajectories due to SPPT. In contrast to SPPT, initial condition perturbations do not affect WCBs and tropical convection systematically. An Eulerian perspective on vertical velocities reveals that SPPT increases the frequency of strong upward motions compared with experiments with unperturbed model physics. Consistent with the altered vertical motions, precipitation rates are also affected by the model physics perturbations. The unperturbed control member shows the same characteristics as the experiments without SPPT regarding rapidly ascending air streams. We make use of this to corroborate the findings from the sensitivity experiments by analyzing the differences between perturbed and unperturbed members in operational ensemble forecasts of ECMWF. Finally, we give an explanation of how symmetric, zero‐mean perturbations can lead to a unidirectional response when applied in a nonlinear system.
    Description: The stochastically perturbed parametrisation tendencies (SPPT) scheme is used at ECMWF to perturb the model physics and introduces state‐dependent perturbations into the parametrisation tendencies. The frequency of rapidly ascending air streams is systematically enhanced when SPPT is active. This effect is stronger when the latent heating is large (panel a), and is therefore more pronounced in the Tropics than in the Extratropics. In contrast, the impact of SPPT on the physical properties of the air streams, such as the latent heat release, is very small (panel b).
    Description: Helmholtz Young Investigator Group ‘Sub‐ Seasonal Predictability: Understanding the Role of Diabatic Outflow’
    Keywords: ddc:551.5
    Language: English
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