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  • ddc:551.5  (20)
  • ddc:330  (5)
  • Inorganic Chemistry
  • English  (25)
  • 2020-2023  (25)
  • 1990-1994
  • 2021  (25)
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  • 1
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    A Lagrangian Perspective on Stable Water Isotopes During the West African Monsoon (2021)
    Details
    Publication Date: 2022-04-01
    Description: We present a Lagrangian framework for identifying mechanisms that control the isotopic composition of mid‐tropospheric water vapor in the Sahel region during the West African Monsoon 2016. In this region mixing between contrasting air masses, strong convective activity, as well as surface and rain evaporation lead to high variability in the distribution of stable water isotopologues. Using backward trajectories based on high‐resolution isotope‐enabled model data, we obtain information not only about the source regions of Sahelian air masses, but also about the evolution of H2O and its isotopologue HDO (expressed as δD) along the pathways of individual air parcels. We sort the full trajectory ensemble into groups with similar transport pathways and hydro‐meteorological properties, such as precipitation and relative humidity, and investigate the evolution of the corresponding paired {H2O, δD} distributions. The use of idealized process curves in the {H2O, δD} phase space allows us to attribute isotopic changes to contributions from (a) air mass mixing, (b) Rayleigh condensation during convection, and (c) microphysical processes depleting the vapor beyond the Rayleigh prediction, i.e., partial rain evaporation in unsaturated and isotopic equilibration in saturated conditions. Different combinations of these processes along the trajectory ensembles are found to determine the final isotopic composition in the Sahelian troposphere during the monsoon. The presented Lagrangian framework is a powerful tool for interpreting tropospheric water vapor distributions. In the future, it will be applied to satellite observations of {H2O, δD} over Africa and other regions in order to better quantify characteristics of the hydrological cycle.
    Description: Key Points: New Lagrangian framework to attribute variability in {H2O, δD} distributions to air mass mixing and phase changes of water. Application to West African Monsoon season 2016 shows characteristic mixing and precipitation effects along trajectories. New framework can be used for the interpretation of satellite and in‐situ observations, and for model validation in future work.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: Swiss National Science Foundation
    Description: European Space Agency
    Description: Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347
    Description: Ministerium für Wissenschaft, Forschung und Kunst Baden‐Württemberg (MWK) http://dx.doi.org/10.13039/501100003542
    Keywords: ddc:551.5
    Language: English
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  • 2
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    Observed and Simulated Variability of Droplet Spectral Dispersion in Convective Clouds Over the Amazon (2021)
    Details
    Publication Date: 2022-03-30
    Description: In this study, the variability of the spectral dispersion of droplet size distributions (DSDs) in convective clouds is investigated. Analyses are based on aircraft measurements of growing cumuli near the Amazon basin, and on numerical simulations of an idealized ice‐free cumulus. In cleaner clouds, the relative dispersion ϵ, defined as the ratio of the standard deviation to the mean value of the droplet diameter, is negatively correlated with the ratio of the cloud water content (qc) to the adiabatic liquid water content (qa), while no strong correlation between ϵ and qc/qa is seen in polluted clouds. Bin microphysics numerical simulations suggest that these contrasting behaviors are associated with the effect of collision‐coalescence in cleaner clouds, and secondary droplet activation in polluted clouds, in addition to the turbulent mixing of parcels that experienced different paths within the cloud. Collision‐coalescence simultaneously broadens the DSDs and decreases qc, explaining the inverse relationship between ϵ and qc/qa in cleaner clouds. Secondary droplet activation broadens the DSDs but has little direct impact on qc. The combination of a rather modest DSD broadening due to weak collision‐coalescence with enhanced droplet activation in both diluted and highly undiluted cloud regions may contribute to maintain a relatively uniform ϵ within polluted clouds. These findings can be useful for parameterizing the shape parameter (μ) of gamma DSDs in bulk microphysics cloud‐resolving models. It is shown that emulating the observed μ−qc/qa relationship improves the estimation of the collision‐coalescence rate in bulk microphysics simulations compared to the bin simulations.
    Description: Key Points: Droplet size distribution patterns observed in warm cumuli reflect the roles of collision‐coalescence, secondary activation, and mixing. The intra‐cloud distribution of droplet spectral dispersion varies with aerosol loading. Emulating the observed shape‐parameter improves bulk estimations of collision‐coalescence in models.
    Description: Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) http://dx.doi.org/10.13039/501100001807
    Description: Max Planck Society (MPG)
    Description: U.S. Department of Energy (DOE) http://dx.doi.org/10.13039/100000015
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: HALO
    Keywords: ddc:551.5
    Language: English
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  • 3
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    Absorbing aerosol decreases cloud cover in cloud‐resolving simulations over Germany (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2022-03-31
    Description: Aerosol can affect clouds in various ways. Beside the microphysical impact of aerosol particles on cloud formation, the interference of aerosol with atmospheric radiation leads to changes in local heating, surface fluxes and thus mesoscale circulations, all of which may also modify clouds. Rather little is known about these so‐called semi‐direct effects in realistic settings – a reason why this study investigates the impact of absorbing aerosol particles on cloud and radiation fields over Germany. Using advanced high‐resolution simulations with grid spacings of 312 and 625 m, numerical experiments with different aerosol optical properties are contrasted using purely scattering aerosol as a control case and realistic absorbing aerosol as a perturbation. The combined effect of surface dimming and atmospheric heating induces positive temperature and negative moisture anomalies between 800 and 900 hPa, impacting low‐level cloud formation. Decreased relative humidity as well as increased atmospheric stability below clouds lead to a reduction of low‐level cloud cover, liquid water path and precipitation. It is further found that direct and semi‐direct effects of absorbing aerosol forcing have similar magnitudes and contribute equally to a reduction of net radiation at the top of the atmosphere.
    Description: Atmospheric aerosol particles can absorb solar radiation, altering the thermal structure of the atmosphere and surface fluxes. Using advanced high‐resolution simulations over Germany with grid spacings of 312 and 625 m, we find that boundary‐layer absorbing aerosol reduces low‐level cloud cover, liquid water path and precipitation. Direct and semi‐direct effects have similar magnitudes and contribute equally to a positive absorbing aerosol forcing.
    Description: German Ministry for Education and Research EU Horizon 2020 project CONSTRAIN
    Description: https://cera-www.dkrz.de/WDCC/ui/cerasearch/entry?acronym=DKRZ_LTA_1174_ds00001
    Keywords: ddc:551.5
    Language: English
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  • 4
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    Targeted covariance inflation for 3D‐volume radar reflectivity assimilation with the LETKF (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-03-31
    Description: The local ensemble transform Kalman filter (LETKF) suggested by Hunt et al., 2007 is a very popular method for ensemble data assimilation. It is the operational method for convective‐scale data assimilation at Deutscher Wetterdienst (DWD). At DWD, based on the LETKF, three‐dimensional volume radar observations are assimilated operationally for the operational ICON‐D2. However, one major challenge for the LETKF is the situation where observations show precipitation (reflectivity) whereas all ensemble members do not show such reflectivity at a given point in space. In this case, there is no sensitivity of the LETKF with respect to the observations, and the analysis increment based on the observed reflectivity is zero. The goal of this work is to develop a targeted covariance inflation (TCI) for the assimilation of 3D‐volume radar data based on the LETKF, adding artificial sensitivity and making the LETKF react properly to the radar observations. The basic idea of the TCI is to employ an additive covariance inflation as entrance point for the LETKF. Here, we construct perturbations to the simulated observation which are used by the core LETKF assimilation step. The perturbations are constructed such that they exhibit a correlation between humidity and reflectivity. This leads to a change in humidity in such a way that precipitation is more likely to occur. We describe and demonstrate the theoretical basis of the method. We then present a case study where targeted covariance inflation leads to a clear improvement of the LETKF and precipitation forecast. All examples are based on the German radar network and the ICON‐D2 model over Central Europe.
    Description: The goal of this work is to develop a targeted covariance inflation (TCI) for the assimilation of 3D‐volume radar data based on the local ensemble transform Kalman filter (LETKF), adding artificial sensitivity and making the LETKF react properly to the radar observations. Perturbations to the simulated observations are constructed such that they exhibit an empirically derived correlation between humidity and reflectivity. This leads to a change in humidity in such a way that precipitation is more likely to occur.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.5
    Language: English
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  • 5
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    Changes in the Tropical Lapse Rate due to Entrainment and Their Impact on Climate Sensitivity (2021)
    Details
    Publication Date: 2022-03-31
    Description: The tropical temperature in the free troposphere deviates from a theoretical moist‐adiabat. The overall deviations are attributed to the entrainment of dry surrounding air. The deviations gradually approach zero in the upper troposphere, which we explain with a buoyancy‐sorting mechanism: the height to which individual convective parcels rise depends on parcel buoyancy, which is closely tied to the impact of entrainment during ascent. In higher altitudes, the temperature is increasingly controlled by the convective parcels that are warmer and more buoyant because of weaker entrainment effects. We represent such temperature deviations from moist‐adiabats in a clear‐sky one‐dimensional radiative‐convective equilibrium model. Compared with a moist‐adiabatic adjustment, having the entrainment‐induced temperature deviations lead to higher clear‐sky climate sensitivity. As the impact of entrainment depends on the saturation deficit, which increases with warming, our model predicts even more amplified surface warming from entrainment in a warmer climate.
    Description: Plain Language Summary: The tropical temperature structure is determined by regions with deep convection, which is believed to be moist‐adiabatic. However, both models and observations show that the temperature deviates from moist‐adiabats. This is because convective parcels often mix with dry environmental air during ascent, pushing the temperature away from the moist‐adiabatic structure. More importantly, the tropical temperature is not dominated by one or a few strongest convective plumes, but rather controlled by the combined effect of many convective plumes of different strengths and depths. Therefore, the tropical temperature structure reflects the composition of convection happening at different values of boundary‐layer energy and mixing processes of variable efficiency with the environment. Using an idealized model, we find that representing such a deviation in the temperature structure increases the surface warming, because the resulting temperature lapse rate (LR) is more similar to a constant LR, showing less temperature increases higher than a moist‐adiabatic LR. This effect is likely amplified in a warmer climate due to this mixing process becoming more efficient in pushing the temperature further away from moist‐adiabats.
    Description: Key Points: The tropical temperature profile in the free troposphere deviates from that following a moist‐adiabatic lapse rate (LR). The deviations from the moist‐adiabatic LR can be explained by entrainment with a buoyancy‐sorting mechanism. The temperature deviations from moist‐adiabats increase climate sensitivity.
    Description: https://doi.org/10.5281/zenodo.1313687
    Description: https://cds.climate.copernicus.eu/cdsapp#%21/dataset/reanalysis-era5-pressure-levels-monthly-means?tab=overview
    Description: https://esgf-data.dkrz.de/projects/cmip6-dkrz/
    Description: http://hdl.handle.net/21.11116/0000-0008-FDA6-0
    Keywords: ddc:551.5
    Language: English
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  • 6
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    Intercalibration of the Plasma Density Measurements in Earth's Topside Ionosphere (2021)
    Details
    Publication Date: 2022-03-25
    Description: Over the last 20 years, a large number of instruments have provided plasma density measurements in Earth's topside ionosphere. To utilize all of the collected observations for empirical modeling, it is necessary to ensure that they do not exhibit systematic differences and are adjusted to the same reference frame. In this study, we compare satellite plasma density observations from Gravity Recovery and Climate Experiment (GRACE), Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), CHAllenging Minisatellite Payload (CHAMP), Swarm, and Communications/Navigation Outage Forecasting System (C/NOFS) missions. Electron densities retrieved from GRACE K‐Band Ranging (KBR) system, previously shown to be in excellent agreement with incoherent scatter radar (ISR) measurements, are used as a reference. We find that COSMIC radio occultation (RO) densities are highly consistent with GRACE‐KBR observations showing a mean relative difference of 〈2%, and therefore no calibration factors between them are necessary. We utilize the outstanding three‐dimensional coverage of the topside ionosphere by the COSMIC mission to perform conjunction analysis with in situ density observations from CHAMP, C/NOFS, and Swarm missions. CHAMP measurements are lower than COSMIC by ∼11%. Swarm densities are generally lower at daytime and higher at nighttime compared to COSMIC. C/NOFS ion densities agree well with COSMIC, with a relative bias of ∼7%. The resulting cross‐calibration factors, derived from the probability distribution functions, help to eliminate the systematic leveling differences between the data sets, and allow using these data jointly in a large number of ionospheric applications.
    Description: Key Points: A systematic comparison of the plasma density data from CHAMP, C/NOFS, GRACE, COSMIC, and Swarm missions is performed. Electron densities retrieved from COSMIC‐RO agree well with GRACE‐KBR observations showing a relative difference of less than 2%. Intercalibration factors, allowing to eliminate the systematic offsets between the considered data sets, are presented.
    Description: Helmholtz Pilot Projects Information & Data Science II, MAchine learning based Plasma density model project
    Description: National Center for Atmospheric Research http://dx.doi.org/10.13039/100005323
    Description: Air Force Office of Scientific Research http://dx.doi.org/10.13039/100000181
    Description: National Science Foundation http://dx.doi.org/10.13039/100000001
    Keywords: ddc:538.76 ; ddc:551.5
    Language: English
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  • 7
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    Paleoclimate Evolution on Titan After Episodic Massive Methane Outgassing Simulated by a Global Climate Model (2021)
    Details
    Publication Date: 2022-03-25
    Description: Titan's paleoclimate after the onset of the putative last major methane outgassing event 700 Myr ago is simulated by a global climate model. If the atmosphere was methane‐depleted prior to outgassing, outgassed methane initially causes warming due to increased greenhouse effect. Further outgassing leads to methane snowfall, which in turn cools the troposphere and surface by an ice‐albedo feedback and thereby initiates a lengthy ice age. Formation of ice sheets begins in the polar region, but with increasing methane inventory the entire globe is eventually covered by surface methane frost as thick as 100 m, with local accumulation on elevated terrains. Among various time‐dependent input parameters the methane inventory by far exerts the greatest control over the climate evolution. As Titan's climate transitions from a dry state via a partially ice‐covered state to a globally ice‐covered state, the circulation and precipitation pattern change profoundly and the tropospheric temperature further decreases. Globally ice‐covered snowball Titan is characterized by weak meridional circulation, weak seasonality and widespread snowfall. Frost ablation begins after the end of outgassing due to photochemical destruction of atmospheric methane. It is conceivable that Titan's polar seas resulted from melting of the polar caps within the past 10 Myr and subsequent drainage to the polar basins. Surface methane frost could only melt when the frost retreated to the polar region, which led to global warming by lowering of the surface albedo at low latitudes and increased greenhouse effect.
    Description: Plain Language Summary: Saturn's moon Titan may have experienced long periods of cold climate in the past when the nitrogen atmosphere contained no methane unlike the present atmosphere. We simulated how Titan's climate may have changed when large amounts of methane were outgassed into such a cold atmosphere as indicated by models of Titan's evolution. The atmosphere can hold a certain amount of methane but the vast majority of outgassed methane condenses out as snow and is deposited on the surface. Bright methane snow on the surface keeps the surface cold and thereby prevents efficient greenhouse warming. Initially, surface methane frost is confined to high latitudes, but eventually the entire globe will be ice‐covered under the assumed total amount of outgassed methane. The seasonal and global pattern of atmospheric circulation and snowfall strongly depend on the degree of frost coverage. The surface frost sublimes away long after outgassing has ceased because methane is destroyed in the atmosphere by photochemistry. Eventually, the polar caps melt, leaving behind the observed polar seas.
    Description: Key Points: Massive methane outgassing into Titan's atmosphere should have caused global ice sheets if the atmosphere was previously depleted in methane. Climate of methane snowball Titan is characterized by weak circulation, low temperature, weak seasonality and widespread snowfall. Melting polar caps in geologically recent past may have resulted in polar seas.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:523 ; ddc:551.5
    Language: English
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  • 8
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    Life Cycle of Shallow Marine Cumulus Clouds From Geostationary Satellite Observations (2021)
    Details
    Publication Date: 2022-03-25
    Description: An analysis of the life cycle of shallow marine cumulus clouds is presented based on geostationary observations by the Spinning Enhanced Visible and InfraRed Imager aboard Meteosat Second Generation (MSG‐SEVIRI). Trajectories of about 250,000 individual shallow marine cumulus clouds have been derived by applying Particle Image Velocimetry to the Satellite Application Facility on Climate Monitoring CLoud property dAtAset using SEVIRI for a region in the trade wind zone centered around the Canary Islands in August 2015. The temporal evolution of the physical properties of these clouds allows to characterize cloud development and to infer the distribution of cloud life time and cloud extent. In the derived data set, the life time distribution follows a double power law with most clouds existing on a time scale of tens of minutes. The cloud physical properties, available during daytime, are analyzed along the cloud tracks. Relative time series of cloud extent, cloud water path, cloud droplet effective radius at cloud top, cloud optical thickness, and cloud droplet number concentration for clouds in two temporal ranges reveal conditions that can be attributed to long‐lasting clouds. Clouds of a certain horizontal extent and cloud top height as well as cloud droplet radius show longer life times if they are optically more dense, i.e., have a higher droplet number concentration. Furthermore, the investigation of the content of liquid cloud water regarding cloud life time and cloud extent shows that small short‐living clouds significantly contribute to cloud radiative effects.
    Description: Plain Language Summary: A comprehensive analysis of the life cycle of shallow marine cumulus clouds is presented based on measurements of a specialized instrument, called SEVIRI, aboard Meteosat's Second Generation geostationary meteorological satellite. A new method is applied to derive the physic‐property temporal evolution of approximately 250,000 individual clouds in a region around the Canary Islands during August 2015. Several constraints are applied to infer the relationship between cloud life time and various cloud parameters. The study reveals that cloud life time is related to the optical thickness when constrained by horizontal extent, cloud top height, and droplet radius. The analysis further shows that small short‐living clouds significantly contribute to cloud radiative effects.
    Description: Key Points: The life cycle of shallow marine cumulus clouds is inferred using a passive space‐based geostationary instrument. Life cycle is quantified by top temperature/height, cloud extent, cloud water path, optical thickness, and droplet radius/number concentration. Cumulus clouds of a certain horizontal extent, cloud top height as well as droplet radius live longer if they are optically denser.
    Description: DAAD, German Academic Exchange Service
    Keywords: ddc:551.5
    Language: English
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  • 9
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    Scale Factors of the Thermospheric Density: A Comparison of Satellite Laser Ranging and Accelerometer Solutions (2021)
    Details
    Publication Date: 2022-03-25
    Description: A major problem in the precise orbit determination (POD) of satellites at altitudes below 1,000 km is the modeling of the aerodynamic drag which mainly depends on the thermospheric density and causes the largest non‐gravitational acceleration. Typically, empirical thermosphere models are used to calculate density values at satellite positions but current thermosphere models cannot provide the required accuracy. Thus, unaccounted variations in the thermospheric density may lead to significantly incorrect satellite positions. For the first time, we bring together thermospheric density corrections for the NRLMSISE‐00 model in terms of scale factors with a temporal resolution of 12 hr derived from satellite laser ranging (SLR) and accelerometer measurements. Whereas, the latter are in situ information given along the satellite orbit, SLR results have to be interpreted as mean values along the orbit within the underlying time interval. From their comparison, we notice a rather similar behavior with correlations of up to 80% and more depending on altitude. During high solar activity, scale factors vary around 30% at low solar activity and up to 70% at high solar activity from the value one. In addition, we found the scaled thermospheric density decreasing stronger as the modeled density of NRLMSISE‐00. To check the reliability of the SLR‐derived scale factors, we compare the POD result of two different software packages, namely DOGS‐OC from DGFI‐TUM and GROOPS from IGG Bonn. Furthermore, a validation of our estimated scale factors with respect to an external data set proofs the high quality of the obtained results.
    Description: Plain Language Summary: Variations in the density of the thermosphere must be taken into account when modeling and predicting the motion of satellites in the near‐Earth environment. Typically, thermospheric densities at the position of satellites are provided by models, but their accuracy is limited. Due to the sensitivity of satellites orbiting the Earth in the altitude range of the thermosphere, they can be used to derive information about the thermospheric density. In this study, we compare for the first time thermospheric density corrections in terms of scale factors for the NRLMSISE‐00 model with a temporal resolution of 12 hr derived from two geodetic measurement techniques, namely satellite laser ranging (SLR) and accelerometry. Our results demonstrate that both measurement techniques can be used to derive comparable scale factors of the thermospheric density, which vary around the desired value one. This indicates to which extent the NRLMSISE‐00 model differs from the observed thermospheric density. On average, during high solar activity, the model underestimates the thermospheric density and can be scaled up using the estimated scale factors. We additionally discuss our estimated scale factors with respect to an external data set. Furthermore, we validate the approach of deriving scale factors from SLR measurements by using two independent software packages.
    Description: Key Points: For the first time, we compare scale factors of the thermospheric density derived from satellite laser ranging (SLR) and accelerometer measurements. The estimated scale factors vary by up to 30% at low solar activity and up to 70% at high solar activity from the desired value 1. Correlations of 0.7–0.8 are obtained between the estimated scale factors from SLR and accelerometer measurements depending on the height.
    Description: German Research Foundation (DFG)
    Description: Technical University of Munich (TUM)
    Keywords: ddc:551.5 ; ddc:526.1
    Language: English
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  • 10
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    Temperatures Near the Lunar Poles and Their Correlation With Hydrogen Predicted by LEND (2021)
    Details
    Publication Date: 2022-03-24
    Description: The lunar polar regions offer permanently shadowed regions (PSRs) representing the only regions which are cold enough for water ice to accumulate on the surface. The Lunar Exploration Neutron Detector (LEND) aboard the Lunar Reconnaissance Orbiter (LRO) has mapped the polar regions for their hydrogen abundance which possibly resides there in the form of water ice. Neutron suppression regions (NSRs) are regions of excessive hydrogen concentrations and were previously identified using LEND data. At each pole, we applied thermal modeling to three NSRs and one unclassified region to evaluate the correlation between hydrogen concentrations and temperatures. Our thermal model delivers temperature estimates for the surface and for 29 layers in the sub‐surface down to 2 m depth. We compared our temperature maps at each layer to LEND neutron suppression maps to reveal the range of depths at which both maps correlate best. As anticipated, we find the three south polar NSRs which are coincident with PSRs in agreement with respective (near)‐surface temperatures that support the accumulation of water ice. Water ice is suspected to be present in the upper ≈19 cm layer of regolith. The three north polar NSRs however lie in non‐PSR areas and are counter‐intuitive as such that most surfaces reach temperatures that are too high for water ice to exist. However, we find that temperatures are cold enough in the shallow sub‐surface and suggest water ice to be present at depths down to ≈35–65 cm. Additionally we find ideal conditions for ice pumping into the sub‐surface at the north polar NSRs. The reported depths are observable by LEND and can, at least in part, explain the existence and shape of the observed hydrogen signal. Although we can substantiate the anticipated correlation between hydrogen abundance and temperature the converse argument cannot be made.
    Description: Plain Language Summary: The lunar poles have quite unique illumination conditions. For instance, the Sun never shines on some crater floors. As a consequence, the floors of those craters are very cold and dark. Here, water ice can accumulate on the surface and can be preserved for long periods of time. One of the instruments mounted on the Moon‐orbiting satellite Lunar Reconnaissance Orbiter is capable of detecting areas where hydrogen is located, which is assumed to be present in the form of water ice. For instance, the instrument detected several areas at the lunar poles where a lot more water ice is found than at other locations. For these special locations, we calculated the temperatures at the surface and near sub‐surface to see whether they are indeed cold enough for water to freeze. At some of these locations, surface temperatures turn out to be too warm. However, we found that at these warm surfaces where no water ice can exist it can be transported into the sub‐surface and survive there. This mechanism is referred to as ice pumping. In summary, we could show that temperatures at all these special locations are usually cold enough for water ice, either right at the surface or within the first meter of soil.
    Description: Key Points: Some neutron suppression regions (NSRs) form from surface ice deposits while others may form through ice pumping in the sub‐surface. NSRs identified by Lunar Exploration Neutron Detector correlate well with low surface temperatures in permanently shadowed regions (PSRs) and are in agreement with sub‐surface temperatures in non‐PSR.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:523 ; ddc:551.5
    Language: English
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  • 11
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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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  • 12
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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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    Toward Parametrization of Precipitating Shallow Cumulus Cloud Organization via Moisture Variance (2021)
    Details
    Publication Date: 2022-03-24
    Description: The influence of the initial vertical moisture profile on precipitating shallow cumulus cloud organization in terms of the column‐averaged moisture variance is investigated using large‐eddy simulations. Five idealized simulations based on the Rain in Cumulus over the Ocean field experiment with different initial moisture profiles are investigated. All cases simulate precipitating shallow cumulus convection in a marine sub‐tropical region under large‐scale subsidence. The results show that the moisture variance is mainly generated through the interaction of the moisture flux and the moisture gradient in the gradient production term at the top of the boundary layer. The development is characterized by three regimes: initial, transition, and quasi‐steady regime. During the initial regime, the moisture gradient is built up by moisture accumulation until precipitating convection starts. Within the transition regime, precipitation enables mesoscale cloud organization with enhanced convective activity and moisture fluxes. The moisture variance increases from the moist to the dry initial moisture profiles. In a following quasi‐steady regime, the moisture variance is approximately preserved. Thereby, the initial moisture gradient between the average sub‐cloud layer and the free atmosphere is found to be an important factor for the generation of the quasi‐steady column‐averaged moisture variance. The result suggests that a resolved‐scale variable like the moisture gradient can be used to estimate the quasi‐steady state conditions resulting from cloud organization. This finding may serve as a starting point for the parametrization of the subgrid scale cloud organization caused by precipitating shallow convection.
    Description: Key Points: Mesoscale organization of precipitating shallow cumulus changes the bulk properties of the atmospheric boundary layer (e.g., cloud cover). The increase of moisture variance during cloud organization is sensitive to the initial vertical moisture profiles. The average gradient between the average sub‐cloud layer and the free atmosphere is a good predictor of the moisture variance.
    Description: Hans Ertel Centre for Weather Research
    Keywords: ddc:551.5
    Language: English
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    Sensitivity of Convection Permitting Simulations to Lateral Boundary Conditions in Idealized Experiments (2021)
    Details
    Publication Date: 2022-03-28
    Description: Limited‐area convection‐permitting climate models (CPMs) with horizontal grid‐spacing less than 4 km and not relying on deep convection parameterisations (CPs) are being used more and more frequently. CPMs represent small‐scale features such as deep convection more realistically than coarser regional climate models (RCMs) with deep CPs. Because of computational costs, CPMs tend to use smaller horizontal domains than RCMs. As all limited‐area models (LAMs), CPMs suffer issues with lateral boundary conditions (LBCs) and nesting. We investigated these issues using idealized Big‐Brother (BB) experiments with the LAM COSMO‐CLM. Grid‐spacing of the reference BB simulation was 2.4 km. Deep convection was triggered by idealized hills with driving data from simulations with different spatial resolutions, with/without deep CP, and with different nesting frequencies and LBC formulations. All our nested idealized 2.4‐km Little‐Brother (LB) experiments performed worse than a coarser CPM simulation (4.9 km) which used a four times larger computational domain and yet spent only half the computational cost. A boundary zone of 〉100 grid‐points of the LBs could not be interpreted meteorologically because of spin‐up of convection and boundary inconsistencies. Hosts with grid‐spacing in the so‐called gray zone of convection (ca. 4–20 km) were not advantageous to the LB performance. The LB's performance was insensitive to the applied LBC formulation and updating (if ≤ 3‐hourly). Therefore, our idealized experiments suggested to opt for a larger domain instead of a higher resolution even if coarser than usual (∼5 $\sim 5$ km) as a compromise between the harmful boundary problems, computational cost and improved representation of processes by CPMs.
    Description: Plain Language Summary: Recently, very high resolution (grid‐spacing 〈 4 km) so‐called convection‐permitting climate models (CPMs) were developed, which represent deep convection explicitly. CPMs, however, are computationally very expensive. They need information about the state of the atmosphere at their lateral boundaries from coarser models. This paper investigates the setting of the lateral boundary formulation. We used idealized experiments with grid‐spacing of ≈ 2.4 km, where deep convection was triggered by small hills. We found that a CPM boundary zone 〉 100 grid points cannot be interpreted reliably. The boundary data should be given to the CPM every 3 hr or more often. Small‐domain CPM simulations all performed worse than a reference simulation on a larger domain with the same resolution or with an even two times lower resolution. We tested different resolutions of the driving data for the CPMs and found that driving data from a model in the “gray zone” of convection (about 4–20 km) is not advantageous for the CPM performance. We concluded that it often might be better to opt for a larger domain with an unusually coarse CPM resolution (ca. 5 km) than for a much smaller domain with grid‐spacing 〈 4 km.
    Description: Key Points: The nesting challenge of convection‐permitting climate modeling (CPM) is investigated with idealized simulation experiments. Nesting the CPM into host simulations with grid‐spacing in the gray zone of convection is not better than into coarser simulations. Large boundary areas with poor simulation quality suggest using large domains even with grid‐spacing coarser than usually accepted for CPM.
    Description: European Union's H2020 Research and Innovation Programme http://dx.doi.org/10.13039/100010661
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.5
    Language: English
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    Examining the Wind Shear Theory of Sporadic E With ICON/MIGHTI Winds and COSMIC‐2 Radio 2 Occultation Data (2021)
    Details
    Publication Date: 2022-03-28
    Description: The wind shear theory is widely accepted as an explanation for the formation of a sporadic E (Es) layer, but the direct comparison of Es with the local wind shear has been limited due to the lack of neutral wind measurements. This study examines the role of the vertical wind shear for Es, using signal‐to‐noise ratio profiles from COSMIC‐2 radio occultation measurements and concurrent measurements of neutral wind profiles from the Ionospheric Connection Explorer. It is observed that the Es occurrence rate and average S4 index are correlated with the negative vertical shear of the eastward wind, providing observational support for the wind shear theory. Es can be observed even when the vertical wind shear is positive, which is interpreted as metallic ion layers generated at an earlier time.
    Description: Plain Language Summary: Sporadic E (Es) is anomalous radio propagation resulting from intense clouds of ionization at heights of the E‐region ionosphere (90–120 km). The formation of an Es layer is generally attributed to the vertical wind shear, which can move metallic ions in the vertical direction by the Lorentz force. According to the wind shear theory, a negative shear of the eastward wind is effective in converging the metallic ions into a thin layer to produce Es. Although previous observations and modeling studies have supported the theory to various degrees, the direct comparison of Es with the vertical wind shear has been limited due to sparse observations of neutral winds at E‐region heights. Neutral wind profiles from the Ionospheric Connection Explorer mission, together with Es data from COSMIC‐2 radio occultation measurements, provide an opportunity to fill this knowledge gap. Direct comparisons of these measurements reveal that the Es occurrence rate is higher and lower for larger negative and positive wind shears, respectively, providing observational evidence for the wind shear theory.
    Description: Key Points: Conjunction observations of sporadic E (Es) from COSMIC‐2 and neutral wind profiles from Ionospheric Connection Explorer/Michelson Interferometer for Global High‐Resolution Thermospheric Imaging are analyzed. Es occurrence rate correlates with the negative vertical shear of eastward wind, providing observational evidence for the wind shear theory. Es can be observed even when the vertical shear of the local eastward wind is positive.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: NASA
    Description: DFG Priority Program Dynamic Earth
    Keywords: ddc:551.5
    Language: English
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    Chemical Evolution of the Exceptional Arctic Stratospheric Winter 2019/2020 Compared to Previous Arctic and Antarctic Winters (2021)
    Details
    Publication Date: 2022-03-28
    Description: The winter 2019/2020 showed the lowest ozone mixing ratios ever observed in the Arctic winter stratosphere. It was the coldest Arctic stratospheric winter on record and was characterized by an unusually strong and long‐lasting polar vortex. We study the chemical evolution and ozone depletion in the winter 2019/2020 using the global Chemistry and Transport Model ATLAS. We examine whether the chemical processes in 2019/2020 are more characteristic of typical conditions in Antarctic winters or in average Arctic winters. Model runs for the winter 2019/2020 are compared to simulations of the Arctic winters 2004/2005, 2009/2010, and 2010/2011 and of the Antarctic winters 2006 and 2011, to assess differences in chemical evolution in winters with different meteorological conditions. In some respects, the winter 2019/2020 (and also the winter 2010/2011) was a hybrid between Arctic and Antarctic conditions, for example, with respect to the fraction of chlorine deactivation into HCl versus ClONO2, the amount of denitrification, and the importance of the heterogeneous HOCl + HCl reaction for chlorine activation. The pronounced ozone minimum of less than 0.2 ppm at about 450 K potential temperature that was observed in about 20% of the polar vortex area in 2019/2020 was caused by exceptionally long periods in the history of these air masses with low temperatures in sunlight. Based on a simple extrapolation of observed loss rates, only an additional 21–46 h spent below the upper temperature limit for polar stratospheric cloud formation and in sunlight would have been necessary to reduce ozone to near zero values (0.05 ppm) in these parts of the vortex.
    Description: Key Points: The Arctic stratospheric winter 2019/2020 showed the lowest ozone mixing ratios ever observed and was one of the coldest on record. Chemical evolution of the Arctic winter 2019/2020 was a hybrid between typical Arctic and typical Antarctic conditions. Only an additional 21–46 h below PSC temperatures and in sunlight would have been necessary to reduce ozone to near zero locally.
    Description: International Multidisciplinary Drifting Observatory for the Study of the Arctic Climate (MOSAiC)
    Keywords: ddc:551.5 ; ddc:551.9
    Language: English
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    Innovation in housing decarbonisation: Germany (2021)
    Details
    Publication Date: 2022-02-18
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
    Type: contributiontoperiodical , doc-type:contributionToPeriodical
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    Germany's transition to a circular economy : how to unlock the potential of cross-industry collaboration (2021)
    Berlin : Econsense
    Details
    Publication Date: 2022-02-18
    Description: The transition from today's "take, make, waste" economic paradigm to a circular economy requires a joint effort from actors on all levels: governments, business, and civil society. While companies are among the drivers of the circular transformation, they find it hard to achieve a circular economy on their own. Hence, cross-industry collaboration is one of the imperatives for scaling a circular economy. Against this background, econsense, together with Accenture and the Wuppertal Institute, launched its study "Germany's Transition to a Circular Economy - How to Unlock the Potential of Cross-Industry Collaboration". Based on a survey and expert interviews within the econsense community, the study finds that companies are yet to unlock the full potential of cross-industry collaboration. While two thirds of analysed industry collaborations have a high potential for scaling the circular economy, only 43 per cent of those already show a high degree of interaction. The study provides concrete guidance for companies to get started with circularity and identify the right partners for cross-industry collaboration. Specifically, the report recommends companies: 1) Understand what circularity is about and map it on their own operations and processes. 2) Understand the different circular business models and identify the ones relevant to each business. 3) Discover areas where collaboration can help to create the needed foundation and to execute circular actions.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
    Type: report , doc-type:report
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    Eco-innovation and digitalisation : case studies, environmental and policy lessons from EU member states for the EU green deal and the circular economy : EIO biennial report 2020 (2021)
    Brussels : European Commission
    Details
    Publication Date: 2022-02-18
    Description: Digitalisation is taking place at a fast pace in all European countries and it is transforming the economies, societies, communication, jobs and the necessary skills for the workplace and everyday life. The Covid-19 pandemic is also accelerating digitalisation at many levels. To address the great challenges resulting from this, the European Commission has launched the Green Deal, a long-term transformation strategy towards an innovative and sustainable society. Three important initiatives under the Green Deal are the New Circular Economy Action Plan, the Biodiversity Strategy for 2030 and the Zero Pollution Action Plan. The various strategies and action plans draw up a large portfolio of measures, instruments and milestones that are always linked to digital technologies. Ideally, these are eco-innovative and sustainable and contribute to improving living conditions in Europe. The EIO Biennial Report 2020, which looks at a different topic every two years, considers digitalisation a major opportunity to accelerate the transition to a circular Europe. In the current report, the authors provide an overview of eco-innovation trends, illustrated by digital technology and policy practices that can further drive the circular economy.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
    Type: report , doc-type:report
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    Sensitivity to changes in the surface‐layer turbulence parameterization for stable conditions in winter: A case study with a regional climate model over the Arctic (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-03-23
    Description: The modeling of the atmospheric boundary layer over sea ice is still challenging because of the complex interaction between clouds, radiation and turbulence over the often inhomogeneous sea ice cover. There is still much uncertainty concerning sea ice roughness, near‐surface thermal stability and related processes, and their accurate parameterization. Here, a regional Arctic climate model forced by ERA‐Interim data was used to test the sensitivity of climate simulations to a modified surface flux parameterization for wintertime conditions over the Arctic. The reference parameterization as well as the modified one is based on Monin–Obukhov similarity theory, but different roughness lengths were prescribed and the stability dependence of the transfer coefficients for momentum, heat and moisture differed from each other. The modified parameterization accounts for the most comprehensive observations that are presently available over sea ice in the inner Arctic. Independent of the parameterization used, the model was able to reproduce the two observed dominant winter states with respect to cloud cover and longwave radiation. A stepwise use of the different parameterization assumptions showed that modifications of both surface roughness and stability dependence had a considerable impact on quantities such as air pressure, wind and near‐surface turbulent fluxes. However, the reduction of surface roughness to values agreeing with those observed during the Surface Heat Budget of the Arctic Ocean campaign led to an improvement in the western Arctic, while the modified stability parameterization had only a minor impact. The latter could be traced back to the model's underestimation of the strength of stability over sea ice. Future work should concentrate on possible reasons for this underestimation and on the question of generality of the results for other climate models.
    Description: The modeling of the atmospheric boundary layer over sea ice is challenging. This is, among others, due to the distinct sea ice surface roughness and pressure ridges as shown in the image, and the often stably stratified atmosphere. We quantified the impact of used parameterizations and show that both surface roughness and stability dependence have a considerable impact on near‐surface turbulent fluxes and atmospheric circulation in Arctic climate simulations.
    Description: German Research Foundation (DFG)
    Description: Helmholtz Association (HGF), POLEX http://dx.doi.org/10.13039/100003872
    Description: Russian Science Foundation (RSF) http://dx.doi.org/10.13039/501100006769
    Keywords: ddc:551.5
    Language: English
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    Tropical cyclone life cycle in a three‐dimensional numerical simulation (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2022-03-29
    Description: An idealized, three‐dimensional, numerical simulation of tropical cyclone evolution in a quiescent environment on an f‐plane is used to explore aspects of the cyclone's life cycle in the context of the rotating‐convection paradigm. In the 20‐day simulation, the vortex undergoes a life cycle including a gestation period culminating in genesis, a rapid intensification phase, a mature phase, a transient decay and re‐intensification phase, a second mature phase and a rapid decay phase. During much of the life cycle, the flow evolution is highly asymmetric, although important aspects of it can be understood within an azimuthally averaged framework, central to which are a boundary‐layer control mechanism and a new ventilation diagnostic. The boundary‐layer control mechanism provides an explanation for the gradual expansion of the inner core of the vortex. The ventilation diagnostic characterizes the ability of deep convection within a given radius to evacuate the mass of air ascending out of the boundary layer within that radius. The transient decay and re‐intensification phase is not associated with an eyewall replacement cycle, but rather with a hitherto undescribed process in which the eyewall becomes fragmented as a rainband complex forms beyond it. This process is interpreted as an interplay between the boundary layer and ventilation. The final rapid decay of the vortex results from the ever increasing difficulty of deep convection to ventilate the air exiting the boundary layer. Any unventilated air flows radially outwards in the lower troposphere and leads to spin‐down because of the approximate conservation of mean absolute angular momentum. If found in real cyclones, such transience or final decay might be erroneously attributed to ambient vertical wind shear. The results support the hypothesis that, even in a quiescent environment, isolated tropical cyclone vortices are intrinsically transient and never reach a globally steady state.
    Description: A three‐dimensional, idealized numerical simulation of tropical cyclone evolution on an f‐plane is used to explore aspects of the cyclone's life cycle in the framework of the rotating‐convection paradigm. In the simulation, which lasts for 20 days, the vortex undergoes a life cycle that includes a gestation period cultimating in genesis, a rapid intensification period, a mature stage followed by a transient decay and re‐intensification stage, a second mature stage and a final rapid decay stage. The results support the hypothesis that, even in a quiescent environment on an f‐plane, isolated tropical cyclone vortices are intrinsically transient and never reach a globally steady state.
    Description: U.S. Office of Naval Research http://dx.doi.org/10.13039/100000006
    Description: German Research Council
    Keywords: ddc:551.5
    Language: English
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    Characterization and Evolution of Organized Shallow Convection in the Downstream North Atlantic Trades (2021)
    Details
    Publication Date: 2022-03-29
    Description: Four previously identified patterns of meso‐scale cloud organization in the trades — called Sugar, Gravel, Flowers, and Fish — are studied using long‐term records of ground‐based measurements, satellite observations and reanalyzes. A deep neural network trained to detect these patterns is applied to satellite imagery to identify periods during which a particular pattern is observed over the Barbados Cloud Observatory. Surface‐based remote sensing at the observatory is composited and shows that the patterns can be distinguished by differences in cloud geometry. Variations in total cloudiness among the patterns are dominated by variations in cloud‐top cloudiness. Cloud amount near cloud base varies little. Each pattern is associated with a distinct atmospheric environment whose characteristics are traced back to origins that are not solely within the trades. Sugar air‐masses are characterized by weak winds and of tropical origin. Fish are driven by convergence lines originating from synoptical disturbances. Gravel and Flowers are most native to the trades, but distinguish themselves with slightly stronger winds and stronger subsidence in the first case and greater stability in the latter. The patterns with the higher cloud amounts and more negative cloud‐radiative effects, Flowers and Fish, are selected by conditions expected to occur less frequently with greenhouse warming.
    Description: Key Points: Meso‐scale patterns of trade‐wind clouds are identified with a neural network and characterized based on observations. The four analyzed patterns distinguish themselves by stratiform cloudiness and less by cloudiness at the lifting condensation level. Two patterns are imprinted by tropical, respectively extra‐tropical intrusions.
    Description: European Union's Horizon 2020 Research and Innovation Programme
    Description: NASA
    Description: https://doi.org/10.5281/zenodo.4767674
    Keywords: ddc:551.5
    Language: English
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    Real‐Time Monitoring of Ionosphere VTEC Using Multi‐GNSS Carrier‐Phase Observations and B‐Splines (2021)
    Details
    Publication Date: 2022-03-29
    Description: Monitoring the Vertical Total Electron Content (VTEC) of the ionosphere is important for applications ranging from navigation to detection of space weather events. Therefore, emerging efforts have been made by several analysis centers to estimate the VTEC using different approaches in real‐time. Global Navigation Satellite Systems (GNSS) is a crucial technology for ionosphere modeling due to its worldwide distributed receivers, high temporal resolution, and low latency data dissemination capability. The selection of a convenient approach to extract ionosphere information from GNSS and the representation of VTEC by an appropriate mathematical model are essential factors for providing fast and accurate ionosphere products. Contrarily to the widespread phase‐leveling method, which uses noisy and erroneous code measurements, the modeling concept in this paper utilizes pure carrier‐phase measurements. Measurements acquired through the International GNSS Service (IGS) real‐time service in Radio Technical Commission for Maritime Services format are from GPS, GLONASS, and GALILEO. The measurement biases, including the ambiguity of carrier‐phase measurements, are simultaneously estimated along with VTEC model parameters. In our approach, VTEC is represented by B‐spline expansions embedded into a Kalman filter. Due to their localizing feature, B‐splines form a highly sparse structure in the filter measurement model. Thus, matrix operations for large‐scale problems can be performed fast using sparse matrix operations, as is done in this study. The differential slant total electron content (dSTEC) analysis and the comparison with Jason‐3 altimetry VTEC were performed for validation within selected periods in 2019. The dSTEC analysis shows that the quality of the generated real‐time VTEC maps slightly outperforms those provided by the other IGS analysis centers.
    Description: Plain Language Summary: As part of the Earth's upper atmosphere, the ionosphere is coupled to the Sun and the Earth's lower atmosphere by complex electromagnetic and dynamic interactions of charged particles (electrons and ions) and neutral species. Spatio‐temporal variations of the ionosphere electron content are of particular importance for technologies utilizing electromagnetic signals such as navigation and telecommunication since the electromagnetic waves are refracted/reflected while traveling through the ionosphere. There has been an increasing demand for real‐time ionosphere products to compute interactions between electromagnetic waves and the ionosphere in real‐time. In this context, the IGS and its several analysis centers have been developing models to provide global Vertical Electron Content (VTEC) products using different approaches based on Global Navigation Satellite Systems (GNSS) observations. By considering the crucial impact of the ionosphere and its constituents on our life, in this study, we model the ionosphere VTEC represented by B‐splines embedded into a Kalman filter in real‐time using carrier‐phase observations from geodetic GNSS receivers.
    Description: Key Points: A new real‐time approach estimating simultaneously coefficients of the B‐spline representation and biases of carrier‐phases was introduced. Carrier‐phase observations from GPS, GLONASS, and GALILEO were incorporated into an adaptive Kalman filter. Global Navigation Satellite Systems (GNSS) observations were obtained in Radio Technical Commission for Maritime Services format via the International GNSS Service real‐time service.
    Description: Technical University of Munich http://dx.doi.org/10.13039/501100005713
    Description: German Research Foundation
    Description: Bundeswehr GeoInformation Center
    Description: German Space Situational Awareness Centre
    Keywords: ddc:538.76 ; ddc:551.5
    Language: English
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    Sustainable supply chains : global cooperative regional economies for prosperity and resilience (2021)
    Wuppertal : Wuppertal Institut für Klima, Umwelt, Energie
    Details
    Publication Date: 2022-02-23
    Description: Two thirds of today's world trade is based on global value chains and supply networks. Purely regional supply chains have become less important in recent decades. The effects of these globalised structures are manifold. On the one hand, they promote employment and generate prosperity. On the other hand, they are beset by extreme social, ecological and economic imbalances. The COVID-19 pandemic has demonstrated the fragility of existing supply chain systems. The lockdown continues to disrupt complex supply chains and many problems of existing production and consumption continue to worsen. COVID-19 is one example of the crises that can shake globally networked supply chains in the short term. Other crises, such as climate change, develop more insidiously and are less immediately recognisable. Different as they are, such crises have one thing in common: they highlight the vulnerability of global social and economic structures and illustrate the impact of global trade on the regions and people of the world. This is precisely where global sustainability strategy comes in - it aims to fundamentally reduce differences and inequalities in opportunities and quality of life. The COVID-19 pandemic has forced the entire world into upheaval, creating an opportunity to make sustainability a central political resilience strategy. In the wake of the Corona pandemic, the discussion about resilient communities has flared up. In order to guarantee supply in the face of such crises, these should be more strongly regional and circular in their economic approach and global and sustainable in their perspective. The aim should be sustainable, transparent, non-exploitative supply chains that guarantee the security of supply to cover basic needs and public services despite sudden changes and crises. This discussion paper draws a future scenario of globally cooperative, circular regional economies that fundamentally reduce global inequalities in opportunities and quality of life, while at the same time permanently preserving the natural foundations of life.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
    Type: workingpaper , doc-type:workingPaper
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    Untapped: understanding the consumer in circular economy activities : empirical case studies on consumer behavior and motivation in the context of circular economy (2021)
    Details
    Publication Date: 2022-08-09
    Description: With increasing world population and an unsettling resource scarcity in the back, sustainble consumption has moved to the foreground of political, economical and social discussions. One major school-of-thought is Circular Economy (CE), an approach summarizing various sustainable consumption activites under one roof. However, quantitative studies on the consumer are rare, yet crucial for a transfer from linear to circular consumption. This dissertation adds to literature by providing pioneer insights into consumer behavior in CE as an overarching concept, instead limiting research on singular subconcepts. Namely, four consumer activities are studied: recycling, upcycling, renting and sharing. In order to identify relevant insights for both academics and practitioners in CE, the research question ("what drives participation in CE?") is broken down into sub-hypotheses, which are addressed by three empirical studies. Using the SOR-Model (adaption Belk 1975) as overarching logic, the three studies deal with (1) the consumer (and their motivation) and situational stimuli (both (2) offline and (3) online). Respectively, three data sets are consulted to assess the sub-hypotheses and to identify overarching insights on how to accelerate consumer participation in CE, The research methodology employed ranges from a structured equation model (SEM), a random allocation field experiment during Fashion Week in Berlin to a discrete-choice model with best-worst scaling. The dissertation succeeds in revealing that (1) different activities in CE can be summarized in one latent variable, proving CE as a wholesome concept in consumer-related activities; that (2) Trust has a leveraging effect on participation in CE activities. Further, Trust can be enhanced offline via face-to-face interaction and online via third-party online attributes.; and that (3) experience in CE activities affects perception of online attributes, implying the need for adapted measures when dealing with CE-unexperienced consumers as compared to consumers with prior experience in CE activities.
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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