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  • Authors: Grosse-Brauckmann, Gisbert;

    Für den Abschnitt "Torfe" der Bodenkundlichen Kartieranleitung, deren 4. Auflage zur Zeit vorbereitet wird, wurde ein neuer Textvorschlag erarbeitet, der hiermit vorgelegt wird. Behandelt werden darin 1) die unterschiedlichen Klassifikationsmöglichkeiten der Torfe auf "botanischer" Grundlage (in den Torfen vertretene Pflanzenreste) sowie im Hinblick auf (primäre) bodenkundlich-chemische Eigenschaften (Basen- und pH-Verhältnisse), 2) die wichtigsten im Gelände ansprechbaren Pflanzenreste und ihre Merkmale, 3) die Zuordnung von verbreiteten botanisch charakterisierten Torfarten (oder "Torfarteneinheiten") zu den bodenkundlichen "Torfartengruppen" Hoch-, Übergangs- und Niedermoortorf an Hand einer Tabelle. Das entscheidende Kriterium für die Zuordnung zum Hochmoortorf ist das ausschließliche Vorkommen der Reste von Hochmoorpflanzen (diese werden im einzelnen aufgeführt). Übergangsmoortorfe sind durch die Reste von Pflanzenarten ausgezeichnet, die an basen- und nährstoffärmere Standorte außerhalb von Hochmooren gebunden sind (neben ihnen können aber auch Hochmoorpflanzen-Reste vertreten sein). Niedermoortorfe sind charakterisiert durch Reste basen- und nährstoffanspruchsvoller Arten (neben denen auch Reste anspruchsloserer Arten vertreten sein können). Proposals are given for a new text of the section "Peat" of the German Soil Mapping Instruction, the 4th edition of which is now under preparation. The topics dealt with are as follows: 1. The different possibilities of classification of peat: on "botanical" basis (their contents of plant remains) and with respect to (primary) chemico-pedological characteristics (base and pH conditions). 2. The characteristics of the most common plant remains identifiable in the field. 3. The assignment of widespread botanical peat types to the three pedological peat groups: raised-bog peat, transitional-mire peat, and fen peat (shown by a table). The criterion decisive on the assignment of a given peat to raised-bog peat is the exclusive occurrence of remains of raised-bog plants (these are quoted in detail). Transitional-mire peats are distinguished by remains of plant species, which are restricted to sites poor in bases and nutrients (beyond the raised bogs, however), besides of them also raised-bog plant remains may be present. Fen peats are characterized by remains of base and nutrient demanding species (besides of them also remains of plants of poorer sites, but not of raised bogs may be present). DFG, SUB Göttingen research

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  • Authors: Bach, L. T.; Stange, P.; Taucher, J.; Achterberg, E. P.; +4 Authors

    Gravitational sinking of photosynthetically fixed particulate organic carbon (POC) constitutes a key component of the biological carbon pump. The fraction of POC leaving the surface ocean depends on POC sinking velocity (SV) and remineralization rate (Cremin), both of which depend on plankton community structure. However, the key drivers in plankton communities controlling SV and Cremin are poorly constrained. In fall 2014, we conducted a 6-week mesocosm experiment in the subtropical NE Atlantic Ocean to study the influence of plankton community structure on SV and Cremin. Oligotrophic conditions prevailed for the first 3 weeks, until nutrient-rich deep water injected into all mesocosms stimulated diatom blooms. SV declined steadily over the course of the experiment due to decreasing CaCO3 ballast and—according to an optical proxy proposed herein—due to increasing aggregate porosity mostly during an aggregation event after the diatom bloom. Furthermore, SV was positively correlated with the contribution of picophytoplankton to the total phytoplankton biomass. Cremin was highest during a Synechococcus bloom under oligotrophic conditions and in some mesocosms during the diatom bloom after the deep water addition, while it was particularly low during harmful algal blooms. The temporal changes were considerably larger in Cremin (max. fifteenfold) than in SV (max. threefold). Accordingly, estimated POC transfer efficiency to 1,000 m was mainly dependent on how the plankton community structure affected Cremin. Our approach revealed key players and interactions in the plankton food web influencing POC export efficiency thereby improving our mechanistic understanding of the biological carbon pump.

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  • Authors: Du, Muye; Kleidon, Axel; Sun, Fubao; Renner, Maik; +1 Authors

    Nonrainy days have rather different hydrologic and radiative conditions than rainy days, but few investigations considered how these different conditions contribute to the observed global warming. Here, we show that global warming is considerably stronger on nonrainy days using observations from China. We find that trends in mean temperature on nonrainy days are about 0.1 ° C/10 yr higher than on rainy days, and that about 80% of the total temperature increase is contributed by nonrainy days. The main reason is likely to be a stronger sensitivity of downwelling longwave radiation to greenhouse forcing on nonrainy days due to fewer clouds and water vapor compared with rainy days, which is not a hydrological effect but mainly a radiative effect. Our findings are consistent with the stronger mean temperature trends in drier regions and imply that the different temperature sensitivities on nonrainy and rainy days may have profound effects on natural and social systems.

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  • Authors: Schlüter, Thomas;

    Aufgabe der vorliegenden Arbeit war es, die in der Taphozönose fossiler Harze aus dem Cenomanium von NW-Frankreich vergesellschafteten Organismen zu analysieren, und dadurch zur Klärung systematischer und palökologischer Fragen beizutragen. In Form einer Monographie werden die Merkmale zusammengestellt, die für fossile Harze aus dem Cenomanium von NW-Frankreich und deren Taphozönose ermittelt werden können. Vergleichend und für Abgrenzungen notwendig werden die Eigenschaften anderer, überwiegend kretazischer fossilführender Harze erwähnt. DFG, SUB Göttingen research

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  • Authors: Haun, Stefan; Dietrich, Stephan;

    Hydro‐morphology describes the interactions between water and sediments in fluvial systems and the corresponding processes across all spatial and temporal scales. The results are natural and anthropogenically influenced bed structures and fluvial landforms. However, many of these hydro‐morphological processes cannot be described analytically yet, as a result of their stochastic behaviour and the multitude of processes involved across spatial and temporal scales. Deeper knowledge of these processes is essential, not only for understanding the system itself, but also for practical applications, which rely on correct and reliable investigations of these processes. During the European Geoscience Union (EGU) General Assembly (GA) 2018 in Vienna, Austria, the conveners of the session on “Measurements, monitoring and numerical modelling of sedimentary and hydro‐morphological processes in open‐water environments” had the idea of initiating a special issue, containing a collection of recent achievements in this research field. The aim of this extended introduction is twofold. First, an overview on research needs in investigating hydro‐morphological processes in open‐water environments is given in this article. Second, recently published studies that aim to improve the understanding of hydro‐morphological processes in rivers, lakes and reservoirs by innovative measurement approaches are discussed. In addition to submitted papers collected from the EGU GA in 2017, 2018 and 2019, related studies published in Earth Surface Processes and Landforms (ESPL) over the last two years are also incorporated into this special issue. The papers selected cover a wide range of studies with differing spatial and temporal resolutions. This broad spectrum of different scales clearly indicates the challenges associated with the development and use of advanced methods for investigating hydro‐morphological processes in open‐water environments. Baden‐Württemberg Stiftung http://dx.doi.org/10.13039/100008316

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  • Authors: Putrasahan, D. A.; von Storch, J.‐S.;

    Plain Language Summary: Large‐scale atmospheric circulation modes influence regional climate variability. For example, the North Atlantic Oscillation (NAO) is a circulation mode closely linked to surface temperatures variations over Europe, Africa, and North America. However, under global warming, changes in regional climate variability and their relation to circulation modes (co‐variability) can evolve differently and disparately depending on timescales. Here, we use the theory of evolutionary spectra to quantify these nonstationary changes and present a novel approach to estimate such changes on various timescales. The estimation approach is based on a large ensemble of climate change simulations. We show that changes in the NAO and regional surface temperature variability and their relationships evolve differently on individual timescales. On 20‐year timescales, co‐variability between NAO and surface temperature weakens over high‐latitude lands surrounding the northern North Atlantic, whereas the corresponding co‐variability on shorter timescales strengthens over subtropical North Africa. These differing evolution and timescale‐dependent changes shed new light on the controlling factors of circulation‐induced regional changes. Taking them into account can lead to the improvement of future regional climate predictions. Regional climate variability is strongly related to large‐scale circulation modes. However, little is known about changes in their spectral characteristics under climate change. Here, we introduce piecewise evolutionary spectra to quantify time‐varying variability and co‐variability of climate variables, and use ensemble periodograms to estimate these spectra. By employing a large ensemble of climate change simulations, we show that changes in the variability and relationships of the North Atlantic Oscillation (NAO) and regional surface temperatures are disparate on individual timescales. The relation between NAO and surface temperature over high‐latitude lands weakens the most on 20‐year timescales compared to shorter timescales, whereas the relation between NAO and temperature over subtropical North Africa strengthens more on shorter timescales than on 20‐year timescales. These projected evolution and timescale‐dependent changes shed new light on the controlling factors of circulation‐induced regional changes. Accounting for them can lead to the improvement of future regional climate predictions. Key Points: We define piecewise evolutionary spectra (special case of evolutionary spectra) to quantify time‐varying second moments in a warming climate. We introduce ensemble periodograms derived from a large ensemble as consistent estimators of piecewise evolutionary spectra. We find time‐dependent and timescale‐dependent changes in relations between NAO and surface temperature. Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659 Max‐Planck‐Gesellschaft http://dx.doi.org/10.13039/501100004189 EU Commission Horizon 2020: PRIMAVERA

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  • Authors: Gossler, Manuel A.; Bayer, Peter; Rau, Gabriel C.; Einsiedl, Florian; +1 Authors

    Heat transport in natural porous media, such as aquifers or streambeds, is generally modeled assuming local thermal equilibrium (LTE) between the fluid and solid phases. Yet, the mathematical and hydrogeological conditions and implications of this simplification have not been fully established for natural porous media. To quantify the occurrence and effects of local thermal disequilibrium during heat transport, we systematically compared thermal breakthrough curves from a LTE with those calculated using a local thermal nonequilibrium (LTNE) model, explicitly allowing for different temperatures in the fluid and solid phases. For the LTNE model, we developed a new correlation for the heat transfer coefficient representative of the conditions in natural porous aquifers using six published experimental results. By conducting an extensive parameter study (>50,000 simulations), we show that LTNE effects do not occur for grain sizes smaller than 7 mm or for groundwater flow velocities that are slower than 1.6 m day−1. The limits of LTE are likely exceeded in gravel aquifers or in the vicinity of pumped bores. For such aquifers, the use of a LTE model can lead to an underestimation of the effective thermal dispersion by a factor of up to 30 or higher, while the advective thermal velocity remains unaffected for most conditions. Based on a regression analysis of the simulation results, we provide a criterion which can be used to determine if LTNE effects are expected for particular conditions.

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  • Authors: Müller, W.A.; Borchert, L.; Ghosh, R.;

    We identify subdecadal variations in European summer temperatures in coupled and uncoupled century-long reanalyses. Spectral analyses reveal significant peaks at 5–10 years in the midtwentieth century. The subdecadal variations show substantial amplitudes of ~1–1.5 °C, associated with extremely warm summers during their positive phases. We use forced ocean model experiments and show that the European summer temperature variations are associated with the subdecadal coupled North Atlantic climate system. A positive winter NAO-like forcing is associated with changes in the ocean circulation and mass and heat convergence occurring 1–2 years prior to European summer temperature rise. Ocean heat content and sea surface temperature increase in the subtropical North Atlantic. The atmospheric response is barotropic and induces wave activity fluxes toward the European continent, modulation of the jet positions, and blocking frequency. The atmospheric response establishes a pathway connecting the subdecadal coupled North Atlantic climate system to European summer temperature.

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  • Authors: Beydoun, H.; Hoose, C.;

    We investigate the sensitivity of self-aggregated radiative-convective-equilibrium cloud-resolving model simulations to the cloud condensation nuclei (CCN) concentration. Experiments were conducted on a long (2,000-km × 120-km) channel domain, allowing the emergence of multiple convective clusters and dry regions of subsidence. Increasing the CCN concentration leads to increased moisture in the dry regions, increased midlevel and upper level clouds, decreased radiative cooling, and decreased precipitation. We find that these trends follow from a decrease in the strength of the self-aggregation as measured by the moist static energy (MSE) variance. In our simulations, precipitation is correlated, both locally and in total, with the distribution of MSE anomalies. We thus quantify changes in the adiabatic/diabatic contributions to MSE anomalies (Wing & Emanuel, 2014, https://doi.org/10.1002/2013MS000269) and relate those changes to changes in precipitation. Through a simple two-column conceptual model, we argue that the reduction in precipitation can be explained thermodynamically by the reduction in mean net radiative cooling and mechanistically by the weakening of the area-weighted radiatively driven subsidence velocity—defined as the ratio of the total radiative cooling over the dry regions and the static stability. We interpret the system's response to increasing CCN as a thermodynamically constrained realization of an aerosol indirect effect on clouds and precipitation.

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  • Authors: Bartkowiak, Maciej; Prokeš, Karel; Fromme, Michael; Budack, Anne; +2 Authors

    The Extreme Environment Diffractometer was a neutron time-of-flight instrument equipped with a constant-field hybrid magnet providing magnetic fields up to 26 T. The magnet infrastructure and sample environment imposed limitations on the geometry of the experiment, making it necessary to plan the experiment with care. EXEQ is the software tool developed to allow users of the instrument to find the optimal sample orientation for their diffraction experiment. InEXEQ fulfilled the same role for the inelastic neutron scattering experiments. The source code of the software is licensed under the GNU General Public Licence 3, allowing it to be used by other facilities and adapted for use on other instruments.

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  • Authors: Grosse-Brauckmann, Gisbert;

    Für den Abschnitt "Torfe" der Bodenkundlichen Kartieranleitung, deren 4. Auflage zur Zeit vorbereitet wird, wurde ein neuer Textvorschlag erarbeitet, der hiermit vorgelegt wird. Behandelt werden darin 1) die unterschiedlichen Klassifikationsmöglichkeiten der Torfe auf "botanischer" Grundlage (in den Torfen vertretene Pflanzenreste) sowie im Hinblick auf (primäre) bodenkundlich-chemische Eigenschaften (Basen- und pH-Verhältnisse), 2) die wichtigsten im Gelände ansprechbaren Pflanzenreste und ihre Merkmale, 3) die Zuordnung von verbreiteten botanisch charakterisierten Torfarten (oder "Torfarteneinheiten") zu den bodenkundlichen "Torfartengruppen" Hoch-, Übergangs- und Niedermoortorf an Hand einer Tabelle. Das entscheidende Kriterium für die Zuordnung zum Hochmoortorf ist das ausschließliche Vorkommen der Reste von Hochmoorpflanzen (diese werden im einzelnen aufgeführt). Übergangsmoortorfe sind durch die Reste von Pflanzenarten ausgezeichnet, die an basen- und nährstoffärmere Standorte außerhalb von Hochmooren gebunden sind (neben ihnen können aber auch Hochmoorpflanzen-Reste vertreten sein). Niedermoortorfe sind charakterisiert durch Reste basen- und nährstoffanspruchsvoller Arten (neben denen auch Reste anspruchsloserer Arten vertreten sein können). Proposals are given for a new text of the section "Peat" of the German Soil Mapping Instruction, the 4th edition of which is now under preparation. The topics dealt with are as follows: 1. The different possibilities of classification of peat: on "botanical" basis (their contents of plant remains) and with respect to (primary) chemico-pedological characteristics (base and pH conditions). 2. The characteristics of the most common plant remains identifiable in the field. 3. The assignment of widespread botanical peat types to the three pedological peat groups: raised-bog peat, transitional-mire peat, and fen peat (shown by a table). The criterion decisive on the assignment of a given peat to raised-bog peat is the exclusive occurrence of remains of raised-bog plants (these are quoted in detail). Transitional-mire peats are distinguished by remains of plant species, which are restricted to sites poor in bases and nutrients (beyond the raised bogs, however), besides of them also raised-bog plant remains may be present. Fen peats are characterized by remains of base and nutrient demanding species (besides of them also remains of plants of poorer sites, but not of raised bogs may be present). DFG, SUB Göttingen research

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  • Authors: Bach, L. T.; Stange, P.; Taucher, J.; Achterberg, E. P.; +4 Authors

    Gravitational sinking of photosynthetically fixed particulate organic carbon (POC) constitutes a key component of the biological carbon pump. The fraction of POC leaving the surface ocean depends on POC sinking velocity (SV) and remineralization rate (Cremin), both of which depend on plankton community structure. However, the key drivers in plankton communities controlling SV and Cremin are poorly constrained. In fall 2014, we conducted a 6-week mesocosm experiment in the subtropical NE Atlantic Ocean to study the influence of plankton community structure on SV and Cremin. Oligotrophic conditions prevailed for the first 3 weeks, until nutrient-rich deep water injected into all mesocosms stimulated diatom blooms. SV declined steadily over the course of the experiment due to decreasing CaCO3 ballast and—according to an optical proxy proposed herein—due to increasing aggregate porosity mostly during an aggregation event after the diatom bloom. Furthermore, SV was positively correlated with the contribution of picophytoplankton to the total phytoplankton biomass. Cremin was highest during a Synechococcus bloom under oligotrophic conditions and in some mesocosms during the diatom bloom after the deep water addition, while it was particularly low during harmful algal blooms. The temporal changes were considerably larger in Cremin (max. fifteenfold) than in SV (max. threefold). Accordingly, estimated POC transfer efficiency to 1,000 m was mainly dependent on how the plankton community structure affected Cremin. Our approach revealed key players and interactions in the plankton food web influencing POC export efficiency thereby improving our mechanistic understanding of the biological carbon pump.

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  • Authors: Du, Muye; Kleidon, Axel; Sun, Fubao; Renner, Maik; +1 Authors

    Nonrainy days have rather different hydrologic and radiative conditions than rainy days, but few investigations considered how these different conditions contribute to the observed global warming. Here, we show that global warming is considerably stronger on nonrainy days using observations from China. We find that trends in mean temperature on nonrainy days are about 0.1 ° C/10 yr higher than on rainy days, and that about 80% of the total temperature increase is contributed by nonrainy days. The main reason is likely to be a stronger sensitivity of downwelling longwave radiation to greenhouse forcing on nonrainy days due to fewer clouds and water vapor compared with rainy days, which is not a hydrological effect but mainly a radiative effect. Our findings are consistent with the stronger mean temperature trends in drier regions and imply that the different temperature sensitivities on nonrainy and rainy days may have profound effects on natural and social systems.

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  • Authors: Schlüter, Thomas;

    Aufgabe der vorliegenden Arbeit war es, die in der Taphozönose fossiler Harze aus dem Cenomanium von NW-Frankreich vergesellschafteten Organismen zu analysieren, und dadurch zur Klärung systematischer und palökologischer Fragen beizutragen. In Form einer Monographie werden die Merkmale zusammengestellt, die für fossile Harze aus dem Cenomanium von NW-Frankreich und deren Taphozönose ermittelt werden können. Vergleichend und für Abgrenzungen notwendig werden die Eigenschaften anderer, überwiegend kretazischer fossilführender Harze erwähnt. DFG, SUB Göttingen research

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  • Authors: Haun, Stefan; Dietrich, Stephan;

    Hydro‐morphology describes the interactions between water and sediments in fluvial systems and the corresponding processes across all spatial and temporal scales. The results are natural and anthropogenically influenced bed structures and fluvial landforms. However, many of these hydro‐morphological processes cannot be described analytically yet, as a result of their stochastic behaviour and the multitude of processes involved across spatial and temporal scales. Deeper knowledge of these processes is essential, not only for understanding the system itself, but also for practical applications, which rely on correct and reliable investigations of these processes. During the European Geoscience Union (EGU) General Assembly (GA) 2018 in Vienna, Austria, the conveners of the session on “Measurements, monitoring and numerical modelling of sedimentary and hydro‐morphological processes in open‐water environments” had the idea of initiating a special issue, containing a collection of recent achievements in this research field. The aim of this extended introduction is twofold. First, an overview on research needs in investigating hydro‐morphological processes in open‐water environments is given in this article. Second, recently published studies that aim to improve the understanding of hydro‐morphological processes in rivers, lakes and reservoirs by innovative measurement approaches are discussed. In addition to submitted papers collected from the EGU GA in 2017, 2018 and 2019, related studies published in Earth Surface Processes and Landforms (ESPL) over the last two years are also incorporated into this special issue. The papers selected cover a wide range of studies with differing spatial and temporal resolutions. This broad spectrum of different scales clearly indicates the challenges associated with the development and use of advanced methods for investigating hydro‐morphological processes in open‐water environments. Baden‐Württemberg Stiftung http://dx.doi.org/10.13039/100008316

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  • Authors: Putrasahan, D. A.; von Storch, J.‐S.;

    Plain Language Summary: Large‐scale atmospheric circulation modes influence regional climate variability. For example, the North Atlantic Oscillation (NAO) is a circulation mode closely linked to surface temperatures variations over Europe, Africa, and North America. However, under global warming, changes in regional climate variability and their relation to circulation modes (co‐variability) can evolve differently and disparately depending on timescales. Here, we use the theory of evolutionary spectra to quantify these nonstationary changes and present a novel approach to estimate such changes on various timescales. The estimation approach is based on a large ensemble of climate change simulations. We show that changes in the NAO and regional surface temperature variability and their relationships evolve differently on individual timescales. On 20‐year timescales, co‐variability between NAO and surface temperature weakens over high‐latitude lands surrounding the northern North Atlantic, whereas the corresponding co‐variability on shorter timescales strengthens over subtropical North Africa. These differing evolution and timescale‐dependent changes shed new light on the controlling factors of circulation‐induced regional changes. Taking them into account can lead to the improvement of future regional climate predictions. Regional climate variability is strongly related to large‐scale circulation modes. However, little is known about changes in their spectral characteristics under climate change. Here, we introduce piecewise evolutionary spectra to quantify time‐varying variability and co‐variability of climate variables, and use ensemble periodograms to estimate these spectra. By employing a large ensemble of climate change simulations, we show that changes in the variability and relationships of the North Atlantic Oscillation (NAO) and regional surface temperatures are disparate on individual timescales. The relation between NAO and surface temperature over high‐latitude lands weakens the most on 20‐year timescales compared to shorter timescales, whereas the relation between NAO and temperature over subtropical North Africa strengthens more on shorter timescales than on 20‐year timescales. These projected evolution and timescale‐dependent changes shed new light on the controlling factors of circulation‐induced regional changes. Accounting for them can lead to the improvement of future regional climate predictions. Key Points: We define piecewise evolutionary spectra (special case of evolutionary spectra) to quantify time‐varying second moments in a warming climate. We introduce ensemble periodograms derived from a large ensemble as consistent estimators of piecewise evolutionary spectra. We find time‐dependent and timescale‐dependent changes in relations between NAO and surface temperature. Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659 Max‐Planck‐Gesellschaft http://dx.doi.org/10.13039/501100004189 EU Commission Horizon 2020: PRIMAVERA

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  • Authors: Gossler, Manuel A.; Bayer, Peter; Rau, Gabriel C.; Einsiedl, Florian; +1 Authors

    Heat transport in natural porous media, such as aquifers or streambeds, is generally modeled assuming local thermal equilibrium (LTE) between the fluid and solid phases. Yet, the mathematical and hydrogeological conditions and implications of this simplification have not been fully established for natural porous media. To quantify the occurrence and effects of local thermal disequilibrium during heat transport, we systematically compared thermal breakthrough curves from a LTE with those calculated using a local thermal nonequilibrium (LTNE) model, explicitly allowing for different temperatures in the fluid and solid phases. For the LTNE model, we developed a new correlation for the heat transfer coefficient representative of the conditions in natural porous aquifers using six published experimental results. By conducting an extensive parameter study (>50,000 simulations), we show that LTNE effects do not occur for grain sizes smaller than 7 mm or for groundwater flow velocities that are slower than 1.6 m day−1. The limits of LTE are likely exceeded in gravel aquifers or in the vicinity of pumped bores. For such aquifers, the use of a LTE model can lead to an underestimation of the effective thermal dispersion by a factor of up to 30 or higher, while the advective thermal velocity remains unaffected for most conditions. Based on a regression analysis of the simulation results, we provide a criterion which can be used to determine if LTNE effects are expected for particular conditions.

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  • Authors: Müller, W.A.; Borchert, L.; Ghosh, R.;

    We identify subdecadal variations in European summer temperatures in coupled and uncoupled century-long reanalyses. Spectral analyses reveal significant peaks at 5–10 years in the midtwentieth century. The subdecadal variations show substantial amplitudes of ~1–1.5 °C, associated with extremely warm summers during their positive phases. We use forced ocean model experiments and show that the European summer temperature variations are associated with the subdecadal coupled North Atlantic climate system. A positive winter NAO-like forcing is associated with changes in the ocean circulation and mass and heat convergence occurring 1–2 years prior to European summer temperature rise. Ocean heat content and sea surface temperature increase in the subtropical North Atlantic. The atmospheric response is barotropic and induces wave activity fluxes toward the European continent, modulation of the jet positions, and blocking frequency. The atmospheric response establishes a pathway connecting the subdecadal coupled North Atlantic climate system to European summer temperature.

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  • Authors: Beydoun, H.; Hoose, C.;

    We investigate the sensitivity of self-aggregated radiative-convective-equilibrium cloud-resolving model simulations to the cloud condensation nuclei (CCN) concentration. Experiments were conducted on a long (2,000-km × 120-km) channel domain, allowing the emergence of multiple convective clusters and dry regions of subsidence. Increasing the CCN concentration leads to increased moisture in the dry regions, increased midlevel and upper level clouds, decreased radiative cooling, and decreased precipitation. We find that these trends follow from a decrease in the strength of the self-aggregation as measured by the moist static energy (MSE) variance. In our simulations, precipitation is correlated, both locally and in total, with the distribution of MSE anomalies. We thus quantify changes in the adiabatic/diabatic contributions to MSE anomalies (Wing & Emanuel, 2014, https://doi.org/10.1002/2013MS000269) and relate those changes to changes in precipitation. Through a simple two-column conceptual model, we argue that the reduction in precipitation can be explained thermodynamically by the reduction in mean net radiative cooling and mechanistically by the weakening of the area-weighted radiatively driven subsidence velocity—defined as the ratio of the total radiative cooling over the dry regions and the static stability. We interpret the system's response to increasing CCN as a thermodynamically constrained realization of an aerosol indirect effect on clouds and precipitation.

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  • Authors: Bartkowiak, Maciej; Prokeš, Karel; Fromme, Michael; Budack, Anne; +2 Authors

    The Extreme Environment Diffractometer was a neutron time-of-flight instrument equipped with a constant-field hybrid magnet providing magnetic fields up to 26 T. The magnet infrastructure and sample environment imposed limitations on the geometry of the experiment, making it necessary to plan the experiment with care. EXEQ is the software tool developed to allow users of the instrument to find the optimal sample orientation for their diffraction experiment. InEXEQ fulfilled the same role for the inelastic neutron scattering experiments. The source code of the software is licensed under the GNU General Public Licence 3, allowing it to be used by other facilities and adapted for use on other instruments.

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