bluuebunny/crossref_metadata_2025 huggingface dataset:
Climate normals and climate change: how to communicate these together?
Authors: Bessembinder Janette , Overbeek Bernadet , Siegmund Peter
Published: March 2021

Meteorological institutes all over the world are publishing new “climate normals” in 2021, as prescribed by the World Meteorological Organization. These “climate normals”, averages over the period 1991-2020, generally have higher temperatures than the previous climate normals over the period 1981-2010 or earlier 30-year periods. As a consequence, in weather forecasts from 2021 the expected temperatures for the coming days and weeks are less often “above normal”, compared to earlier years. In the Netherlands there has been already a lot of discussion about these “climate normals”. Several people, including climate researchers and weather providers, object to them, since they say that these “normals” obscure climate change. Especially the word “normals” is what bothers them, since the current state of the climate should not be considered normal. At KNMI we understand this problem, although we also see the importance of providing regular updates of the description of the “current” climate. Many aspects in society are designed and operated taking into account the averages and extremes in the current climate. Climate is an important aspect in almost any sector, from water management, agriculture to super markets and theme parks. Several visualizations (climate dashboard and weather and climate plume) are developed at the Royal Netherlands Meteorological Institute (KNMI) that combine information on “climate normals”, past and future climate change and weather forecasts.

During the presentation examples of the above described visualizations are shown and the advantages and disadvantages are described. Suggestions are presented on how to communicate about “climate normals” and climate change.
Quantification of SO2 emission rates from the Kilauea volcano in Hawaii by the divergence of the SO2 flux using S5P-TROPOMI satellite measurements
Authors: Jost Adrian , Beirle Steffen , Dörner Steffen , Wagner Thomas
Published: March 2021

With a nearly continuously effusive eruption since 1983, the Kilauea volcano (Hawaii, USA) is one of the most active volcanoes in the world. At the beginning of May 2018, a sequence of eruptions on the Lower East Rift Zone (LERZ) caused an enhanced outbreak of volcanic gases and aerosols, releasing them into the troposphere. Since these gases and particles affect climate, environment, traffic, and health on regional to global scales, a continuos monitoring of the emission rates is essential.

As satellites provide the opportunity to observe and quantify the emissions remotely from space, their contribution to the monitoring of volcanoes is significant. The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor satellite was successfully launched by the end of 2017 and provides measurements with unprecedented level of details with a resolution of 3.5 x 7 km2. This also allows for an accurate retrieval of trace gas species such as volcanic SO2.

Here, it will be shown that the location and strength of SO2 emissions from Kilauea can be determined by the divergence of the temporal mean SO2 flux. This approach, which is based on the continuity equation, has been demonstrated to work for NOX emissions of individual power plants (Beirle et al., Sci. Adv., 2019).

The present state of our work indicates that emission maps of SO2 can be derived by the combination of satellite measurements and wind fields on high spatial resolution. As the divergence is highly sensitive on point sources like the erupting fissures in the 2018 Kilauea eruption, they can be localized very precisely. The obtained emission rates are slightly lower than the ones reported from ground-based measurements in other studies like the one from Kern et al. (Bull. Volcanol., 2020). The effects of suboptimal conditions like high cloud fractions on the method probably affect the derived emission rates and have to be further analyzed.
Transition from continental rifting to oceanic spreading in the northern Red Sea area
Authors: El Khrepy Sami , Koulakov Ivan , Al-Arifi Nassir , S. Alajmi Mamdouh , N. Qadrouh Ayman
Published: March 2021

Lithosphere extension, which plays an essential role in plate tectonics, occurs both in continents (as rift systems) and oceans (spreading along mid-oceanic ridges). The northern Red Sea area is a unique natural geodynamic laboratory, where the ongoing transition from continental rifting to oceanic spreading can be observed. Here, we analyze travel time data from a merged catalogue provided by the Egyptian and Saudi Arabian seismic networks to build a three-dimensional model of seismic velocities in the crust and uppermost mantle beneath the northern Red Sea and surroundings. The derived structures clearly reveal a high-velocity anomaly coinciding with the Red Sea basin and a narrow low-velocity anomaly centered along the rift axis. We interpret these structures as a transition of lithospheric extension from continental rifting to oceanic spreading. The transitional lithosphere is manifested by a dominantly positive seismic anomaly indicating the presence of a 50–70-km-thick and 200–300-km-wide cold lithosphere. Along the forming oceanic ridge axis, an elongated low-velocity anomaly marks a narrow localized nascent spreading zone that disrupts the transitional lithosphere. Along the eastern margins of the Red Sea, the lithosphere is disturbed by the lower-velocity anomalies coinciding with areas of basaltic magmatism.
 Evaluation of dissolved 4He as a groundwater age tracer in shallow fractured aquifers 
Authors: Labasque Thierry , Chatton Eliot , Vergnaud Virginie , Aquilina Luc , Camille Bouchez
Published: March 2021

Anthropogenic gas tracers such as CFC, SF6, 85Kr, 36Cl or 3H have been widely used to study shallow groundwaters with residence time of less than 70 yr. For longer groundwater residence time (100- x1000 yr), 39Ar, 14C, 36Cl and 4He have been used. 4He can cover a dating range of 10 to thousands of years (Solomon et al., 1996). The main difficulty is to estimate the production rate through U and Th decay and the others fluxes: atmosphere, lithosphere and asthenosphere. In many cases U-Th production is not sufficient to explain the 4He concentrations observed in the aquifer. Other 4He fluxes can then be estimated through the use of other tracers: 14C, 36Cl or modeling. Fracturing may also enhance 4He concentrations in groundwater.

We present here the evaluation of 4He in a crystalline fractured aquifer in the Northwest of France (H+ national hydrogeological network), in order to investigate the range of groundwater residence time in this complex shallow aquifer. Previous studies on this aquifer reveal mixing between young (<70 yrs) and old waters (>1000 yrs) (Ayraud et al., 2008). The Helium radiogenic production rate is then evaluated through in situ production (U, Th, porosity), calibration with CFC and 14C, and modelling of the diffusion processes affecting 14C and 4He through physical characteristics of the aquifer (porosity, fracture spacing and aperture). Young groundwater residence times estimated by 4He agree with those estimated by CFC and 3H/3He. In this fractured media, old groundwater residence times (> 100 yr) are better estimated through the integration of the mass transfer between the fractures and the porous rock matrix through diffusion processes. 4He proves to be a valuable tool to characterize groundwater mixing processes and groundwater residence times from a decade to thousands of years.

Solomon, D. K., Hunt, A., & Poreda, R. J. (1996). Source of radiogenic helium 4 in shallow aquifers: Implications for dating young groundwater. Water Resources Research, 32(6), 1805-1813.

Ayraud, V., Aquilina, L., Labasque, T., Pauwels, H., Molenat, J., Pierson-Wickmann, A. C., ... & Fourre, E. (2008). Compartmentalization of physical and chemical properties in hard-rock aquifers deduced from chemical and groundwater age analyses. Applied geochemistry, 23(9), 2686-2707.
European beech is a net annual source of methane (CH4)
Authors: Machacova Katerina , Warlo Hannes , Svobodová Kateřina , Agyei Thomas , Uchytilová Tereza , Horáček Petr , Lang Friederike
Published: March 2021

Trees are known to be sources of methane (CH4), an important greenhouse gas, into the atmosphere. However, still little is known about the seasonality of the tree stem CH4 fluxes, particularly for the dormant season, and about the impact of environmental parameters on this gas exchange. This makes the estimation of net annual ecosystem CH4 fluxes difficult.

We determined seasonal dynamics of CH4 exchange of mature European beech stems (Fagus sylvatica) and of adjacent forest floor in a temperate montane forest of White Carpathians, Czech Republic, from November 2017 to December 2018. We used static chamber methods and gas chromatographic analyses. We aimed to understand the unknown role in seasonal changes of CH4 fluxes of these forests, and the spatiotemporal variability of the tree fluxes.

The beech stems were net annual sources for atmospheric CH4, whereas the forest floor was a predominant sink for CH4. The stem CH4 emissions showed high inter-individual variability and clear seasonality following the stem CO2 efflux. The fluxes of CH4 peaked during the vegetation season, and remained low but significant to the annual totals during winter dormancy. By contrast, the forest floor CH4 uptake followed an opposite flux trend with low CH4 uptake detected in the winter dormant season and elevated CH4 uptake during the vegetation season. Based on our preliminary analyses, the detected high spatial variability in stem CH4 emissions can be explained neither by the CH4 exchange at the forest floor level, nor by soil CH4 concentrations, soil water content and soil temperature, all measured in vertical soil profiles close to the studied trees.

European beech trees, native and widely spread species of Central Europe, seem to markedly contribute to the seasonal dynamics of the ecosystem CH4 exchange, and their CH4 fluxes should be included into forest greenhouse gas emission inventories.

 

Acknowledgement

This research was supported by the Czech Science Foundation (17-18112Y), National Programme for Sustainability I (LO1415), CzeCOS (LM2015061), and SustES - Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions (CZ.02.1.01/0.0/0.0/16_019/0000797). We thank Libor Borák and Leszek Dariusz Laptaszyński for their technical and field support.

 
Seasonal climate predictions for marine risk assessment in the Barents Sea
Authors: Polkova Iuliia , Schaffer Laura , Aarnes Øivin , Baehr Johanna
Published: March 2021

Marine risk embraces an assessment of likelihoods and consequences of impacts from climate fluctuations in order to identify time and regions vulnerable to climate hazards. This information can support sustainable and safe marine activities. The marine risk assessment is a part of the marine service provided by the DNV GL (short for Det Norske Veritas and Germanischer Lloyd). In their current risk application, likelihoods of extreme conditions on the sea are based on historical observations and atmospheric reanalyses. We assess predicted likelihoods of extreme conditions over 1990-2017 in the boreal summer (prediction months 2-4) from the seasonal forecast system provided by the German Meteorological Service (DWD). We chose summer as it represents the time of the open-water season, when the highest marine activity in the Barents Sea takes place. We selected three indicators from the marine risk assessment. Two of them represent meteorological properties such as wind speed and 2-meter temperature (T2m). The third indicator – the wind chill index (WCI) is a combination of the previous two and represents heat loss from the human body to its surroundings during cold and windy weather. As expected, the prediction skill assessment suggests different levels of predictability for the three indicators, with T2m having the highest skill followed by WCI and wind speed. The prediction skill represents the "trust layer" superimposed on the predicted likelihoods and used as input fields for marine risk assessment. From the likelihood maps for the test period of summer 2020 follows that large areas of the Barents Sea represent favorable conditions for marine operations considering high prediction skill and low likelihood for extreme WCI (>1000 W/m2) and T2m (<0 °C) conditions in July and August. The wind speed (>13.9 m/s) is poorly predictable beyond the first lead month. Thus, if risk assessment is based on a suite of climate indicators with the heterogeneous prediction skill, the total risk assessment might be limited by the skill of the indicator with the lowest prediction skill. However, not all climate indicators are equally contributing to the risk assessment. The study describes a workflow for application of seasonal climate predictions and points to a few lessons learned, which can be useful to future climate services.
A new vertical coordinate formulation to improve forecasts of fog and low stratus in high-resolution numerical weather prediction models
Authors: Westerhuis Stephanie , Fuhrer Oliver
Published: March 2021

Fog and low stratus pose a major challenge for numerical weather prediction (NWP) models. Despite high resolution in the horizontal (~1 km) and vertical (~20 m), operational NWP models often fail to accurately predict fog and low stratus. This is a major issue at airports which require visibility predictions, or for energy agencies estimating day-ahead input into the electrical grid from photovoltaic power.

Most studies dedicated to fog and low stratus forecasts have focused on the physical parameterisations or grid resolutions. We illustrate how horizontal advection at the cloud top of fog and low stratus in a grid with sloping vertical coordinates leads to spurious numerical diffusion and subsequent erroneous dissipation of the clouds. This cannot be prevented by employing a higher-order advection scheme. After all, the formulation of the terrain-following vertical coordinate plays a crucial role in regions which do not exhibit perfectly flat orography. We suggest a new vertical coordinate formulation which allows for a faster decay of the orographic signal with altitude and present its positive impact on fog and low stratus forecasts. Our experiments indicate that smoothing of the vertical coordinates at low altitudes is a crucial measure to prevent premature dissipation of fog and low stratus in high-resolution NWP models.
Evaporation from a large lowland reservoir – observed dynamics during a warm summer
Authors: Jansen Femke A. , Teuling Adriaan J. , Uijlenhoet Remko , Jacobs Cor M.J. , Hazenberg Pieter
Published: March 2021

Distinct differences in surface characteristics between a water body and a land surface result in different drivers of evaporation and therefore its dynamics. It is essential to include and represent this difference in the parameterization of open water evaporation (Ewater) to improve operational hydrological models. Additionally, more accurate parameterization becomes even more crucial to predict potential changes in quantity and dynamics of Ewater in a changing climate in support of optimal water management now and in the future.

For this purpose, we performed a long-term measurement campaign to measure Ewater and related meteorological variables over a large lowland reservoir in the Netherlands. During the summer seasons of 2019 and 2020 eddy-covariance systems were applied at two locations at the border of lake IJsselmeer in the Netherlands. These high temporal resolution measurements gave us the opportunity to explore the dynamics and identify the underlying driving mechanisms of Ewater. Using the data collected during the summer of 2019 we were able to develop a simple regression model for both measurement locations. Combinations, both sums and products, of the following independent variables were considered: global radiation, wind speed, water skin temperature, vapour pressure deficit, and vertical vapour pressure gradient. The product of wind speed and vertical vapour pressure gradient best explained the observed hourly Ewater rates, which is consistent with the commonly used aerodynamic approach. The model was validated using the data of 2020. Additionally, we compared measured Ewater to Ewater computed with Makkink’s equation, which is currently used in the Dutch operational hydrological models to estimate Ewater. Although a correction factor is applied to account for the difference between land evaporation and Ewater, Makkink is not able to capture the dynamics of Ewater. This was reflected in the timing and shape of the evaporation peak at both daily and monthly scales. The disagreement of Ewater dynamics found between the measured and simulated Ewater even more demonstrates the value and need of a correct parameterization of Ewater.
Exploring the functional strategies adopted by coastal plants along an ecological gradient by means of morpho-functional traits
Authors: Ciccarelli Daniela , Bona Cleusa
Published: March 2021

Coastal dunes are characterised by strong interactions between biotic and abiotic factors along a short gradient from the shoreline to the inland region. We carried out an ecological analysis of the vegetation in a protected area of the Italian coast to evaluate the relationships among species abundance; the occurrence of morphoanatomical traits related to leaves, stems and roots; and soil variables. Three transects were established perpendicular to the shoreline with 27 plots distributed in the frontal dunes, back dunes, and temporarily wet dune slacks.

The analysis based on community weighted mean values is consistent with the ecological constraints along the shoreline-inland gradient. The front-plots were characterised by the presence of pioneer communities (with succulent leaves as evidenced by the high limb thickness values and the low LDMC values) that are well adapted to the harsh environmental conditions of these habitats. Farther from the sea, the back-plot vegetation was characterised by functional traits (especially high LDMC values) that are consistent with the less-extreme ecological conditions. Last, the slack-plots seemed to be very interesting from a functional point of view. They were dominated by geophytes that had adopted C4 photosynthesis and had amphistomatic leaves and abundant aerenchyma in the roots.

The native vs. invasive status, C4 photosynthesis, leaf trichomes and aerenchyma in the roots were significantly correlated with soil moisture, organic matter content and pH. These results demonstrate the usefulness of anatomical traits (especially those of the root system) in understanding the functional strategies adopted by plants.

Last, invasive species tended to occupy plots with high levels of soil moisture, and they were not abundant in the habitats with more arid conditions. These data confirmed that alien species are less adapted to the harsh environmental conditions of coastal sand dunes. Increasing the spatial extent of the study area and integrating other functional traits, such as ecophysiological or regenerative characteristics, into the study may allow the development of a more comprehensive functional framework of the invasion process. All this information can be used to develop appropriate management strategies for coastal dune ecosystems.
The emergence of subaerial crust and onset of weathering 3.7 billion years ago
Authors: Roerdink Desiree , Ronen Yuval , Strauss Harald , Mason Paul
Published: March 2021

Reconstructing the emergence and weathering of continental crust in the Archean is crucial for our understanding of early ocean chemistry, biosphere evolution and the onset of plate tectonics. However, considerable disagreement exists between the various elemental and isotopic proxies that have been used to trace crustal input into marine sediments, and data are scarce prior to 3 billion years ago. Here we show that chemical weathering modified the Sr isotopic composition of Archean seawater as recorded in 3.52 to 3.20 Ga stratiform marine-hydrothermal barite deposits from three different cratons. We use a combination of barite crystal morphology, oxygen, multiple sulfur and strontium isotope data to select barite samples with the most seawater-like isotopic compositions, and subsequently use these in a hydrothermal mixing model to calculate a plausible seawater Sr isotope evolution trend from measured 87Sr/86Sr data. From modeled mixing ratios between seawater and hydrothermal fluids required for barite precipitation and comparison of 87Sr/86Sr in theoretical seawater-hydrothermal fluid mixtures with those recorded in the barite, we obtain a novel seawater Sr isotope evolution trend for Paleoarchean seawater that is much more radiogenic than the curve previously determined from carbonate rocks. Our findings require the presence and weathering of subaerial and evolved (high Rb/Sr) crust from 3.7 ± 0.1 Ga onwards, and demonstrate that crustal weathering affected the chemistry of the oceans 500 million years earlier than previously thought.
Heteroskedasticity between GNSS time-series repeatabilities and noise magnitudes
Authors: Duman Huseyin , Şanlı Doğan Uğur
Published: March 2021

In the analysis of GNSS time series, when the sampling frequency and time-series lengths are almost identical, it is possible to highlight a linear relationship between the series repeatabilities (i.e. WRMS) and noise magnitudes. In the literature, linear equations as a function of WRMSs allowed many researchers to estimate the noise magnitudes. However, this was built upon homoskedasticity. We experienced the higher WRMSs, the more erroneous analysis results using the noise magnitudes from the linear equations stated. We hence studied whether or not homoscedasticity clearly describes the modeling errors. To test that, we used the published results of GPS baseline components from the previous work in the literature and realized here that each component forms part of the totality. We introduced all baseline component results as a whole into statistical analysis to check heteroskedasticity. We established null and alternative hypotheses on the residuals which are homoscedastic (H0) or heteroskedastic (HA). We adopted both the Breusch-Pagan test and the Goldfeld-Quandt test to prove heteroskedasticity and obtained p-values for both methods. The p-value, which is the probability measure, equals to almost zero for both test methods, that is, we fail to accept the null hypothesis. Consequently, we can confidently state that the relationship between the WRMSs and the noise magnitudes is heteroskedastic.

Keywords: Noise magnitudes, repeatabilities, heteroskedasticity, time-series analysis
A coupled multi-proxy and process modelling approach for extraction of quantitative terrestrial ecosystem information from speleothems
Authors: Lechleitner Franziska , Day Christopher C. , Kost Oliver , Wilhelm Micah , Haghipour Negar , Henderson Gideon M. , Stoll Heather M.
Published: March 2021

Terrestrial ecosystems are intimately linked with the global climate system, but their response to ongoing and future anthropogenic climate change remains poorly understood. Reconstructing the response of terrestrial ecosystem processes over past periods of rapid and substantial climate change can serve as a tool to better constrain the sensitivity in the ecosystem-climate response.

In this talk, we will present a new reconstruction of soil respiration in the temperate region of Western Europe based on speleothem carbon isotopes (δ13C). Soil respiration remains poorly constrained over past climatic transitions, but is critical for understanding the global carbon cycle and its response to ongoing anthropogenic warming. Our study builds upon two decades of speleothem research in Western Europe, which has shown clear correlation between δ13C and regional temperature reconstructions during the last glacial and the deglaciation, with exceptional regional coherency in timing, amplitude, and absolute δ13C variation. By combining innovative multi-proxy geochemical analysis (δ13C, Ca isotopes, and radiocarbon) on three speleothems from Northern Spain, and quantitative forward modelling of processes in soil, karst, and cave, we show how deglacial variability in speleothem δ13C is best explained by increasing soil respiration. Our study is the first to quantify and remove the effects of prior calcite precipitation (PCP, using Ca isotopes) and bedrock dissolution (open vs closed system, using the radiocarbon reservoir effect) from the speleothem δ13C signal to derive changes in respired δ13C over time. Our approach allows us to estimate the temperature sensitivity of soil respiration (Q10), which is higher than current measurements, suggesting that part of the speleothem signal may be related to a change in the composition of the soil respired δ13C. This is likely related to changing substrate through increasing contribution from vegetation biomass with the onset of the Holocene.

These results highlight the exciting possibilities speleothems offer as a coupled archive for quantitative proxy-based reconstructions of climate and ecosystem conditions.
A global inventory of potential future glacial lakes
Authors: Frey Louis , Frey Holger , Huss Matthias , Allen Simon , Farinotti Daniel , Huggel Christian , Emmer Adam , Shugar Dan
Published: March 2021

A prominent phenomenon accompanying glacier retreat is the formation of new lakes. Such glacial lakes are the subject of numerous studies and investigations due to their potential to produce far-reaching glacial lake outburst floods (GLOFs), but also because they might provide opportunities for water resource management and energy production. Here we present a first global inventory of potential future glacial lakes, along with expected formation times under different RCP scenarios.

From published datasets of ice thickness distributions of all glaciers of the world, we identified glacier bed overdeepenings and extracted parameters of potential future lakes, such as area, depth and volume. The consideration of the ensemble of ice thicknesses allowed for a first-order quantification of uncertainties. We identified 67,000 (ranging from 55,000 to 87,000) overdeepenings with volumes larger than 1 x 106 m3, the total surface area and volume of corresponding potential lakes is 61,000 (56,000 to 64,000) km2 and 4,600 (3,100 to 7,200) km3, respectively. However, these numbers are based on the assumption of fully water-filled overdeepenings and therefore represent upper bound estimates. Global results are strongly influenced by very large depressions identified beneath (flat) polar glaciers and ice caps.  We then combined potential future lake sites with estimated future glacier extents from a global glacier evolution model (GloGEM), in order to estimate formation periods of these future lakes, considering different RCPs. Strong regional differences are also found in the anticipated formation periods: While in the low latitudes most future lakes are expected to form in the current decade, irrespective of the RCP, Arctic regions have highest lake formation rates towards the end of the 21st century, with the majority of bed overdeepening not being exposed by glacier retreat until 2100. In mid latitude mountain regions, large differences between RCP2.6 and RCP8.5 exist in regard of the timing of lake formation and the amount of total uncovered overdeepenings.

In addition to geometric properties and expected formation periods, the topographic potential for impacting mass movements, such as rock or ice avalanches, is determined for each overdeepening. In combination with potential lake volume and watershed area of the lake, these characteristics can be used for a first order estimation of lake outburst susceptibility. With a basic flow routing algorithm, potential outburst trajectories are modeled for each overdeepening. In combination with information on population density, settlements and further socio-economic and environmental datasets, this information can be used for future analyses of hazards, risks and opportunities associated with these potential future glacial lakes.
Spatial distribution of the sediments in the Gangkou River catchment: Evidence from chemical composition, rare earth elements, and lead isotopes
Authors: Chao Hung-Chun
Published: March 2021

    Sediment geochemistry has been widely used to indentify the source of the sediments delivered from catchment to the deposition basin.  In this study, bed load sediments, high terrace soils, beach sediments, and cores drilled at estuary were collected at the catchment of Gangkou River and its tributary, Linlu River, southern Taiwan.  All sediments were sieved by 0.062 μm sifter and exchangeable, carbonate, and iron oxide phases were leached and only residue silicate phase were digested.  Chemical composition, rare earth elements (REEs), and lead isotopes were measured.  The results show that two major catchments, Linlu River and Gangkou River, as well as high terrace soil and beach sediments can be successfully classified by chemical composition and lead isotopes.  However, REEs show signature of upper continental crust and no differences among all the samples, possibly due to the same source of high REEs minerals.  The characteristic of chemical composition and lead isotopes are different between two catchments and the estuary sediments as well as beach sediments near the estuary imply mixing behavior between two catchments.  The upper most of the estuary core samples, presented as modern sediment, have similar chemical composition and lead isotopes compared with the mainstream.  However, the beach sediment on the top of the dune and the lower part of the core samples, which are elder than 7 ka, have distinct chemical and isotopic characteristics, indicating different sediment sources.  In, summary, chemical composition and the lead isotopes are robust tracers for the leached fine sediments in Gangkou River catchment but REEs are not.  The results of estuary core indicate that the sediment source of the estuary before 7 ka is different from the present.
Response of precipitation extremes to warming: what have we learned from theory and idealized cloud-resolving simulations, and what remains to be learned?
Authors: Muller Caroline , Yukari Takayabu
Published: March 2021

In this work, we review recent important advances in our understanding of the response of precipitation extremes to warming from theory and from idealized cloud-resolving simulations. A theoretical scaling for precipitation extremes has been proposed and refined in the past decades, allowing to address separately the contributions from the thermodynamics, the dynamics and the microphysics. Theoretical constraints, as well as remaining uncertainties, associated with each of these three contributions to precipitation extremes, will be discussed. Notably, although to leading order precipitation extremes seem to follow the thermodynamic theoretical expectation in idealized simulations, considerable uncertainty remains regarding the response of the dynamics and of the microphysics to warming, and considerable departure from this theoretical expectation is found in observations and in more realistic simulations. We also emphasize key outstanding questions, in particular the response of mesoscale convective organization to warming. Observations suggest that extreme rainfall often comes from organized system in very moist environments. Improved understanding of the physical processes behind convective organization is needed in order to achieve accurate extreme rainfall prediction in our current, and in a warming climate.
Morphology of tidal bedforms, Weser Estuary, Germany
Authors: Lefebvre Alice , Herrling Gerald , Zorndt Anna , Krämer Knut , Becker Marius , Winter Christian
Published: March 2021

The distribution and morphology of tidal bedforms in the Weser Estuary, Germany, between the tidal limit (Weser-km 0 in Bremen) and the open North Sea (Weser-km 110) has been analysed for a five-year period (2009-2013) based on monthly bathymetric surveys carried out along the main waterway. Bedforms were detected from gridded bathymetry data (2x2 m) and their geometric properties described. In particular, the presence and position of a slip face, here defined as the portion of the lee side steeper than 15°, were determined. In earlier studies, this was shown to be a practical criterion for the presence of a permanent flow separation and a turbulent wake in the lee of bedforms. Here it is used as a simplified indicator of bedform roughness: if a bedform does feature a slip face, it is assumed to be an active roughness element. The results were related to measured river discharge and water levels and modelled flow velocities.

Bedforms properties varied spatially and temporally along the estuary. Along the main bedform field (Weser-km 12 to 55) bedforms were mostly flood-oriented upstream, gradually becoming symmetrical then ebb-oriented downstream. In times of high discharge, all bedforms were more ebb-oriented than in times of low discharge. Bedforms in the Weser Estuary can be described as predominantly low angle dunes and their steepest slope is situated near the bedform crest. The analysed bedforms (in the main navigational channel, which is deepened and constrained) are also very two-dimensional, with little variations of three-dimensionality in time or space.

Although the Weser bedforms are mainly low angle, a significant proportion of bedforms possesses a slip face. This implies that they have a strong potential to induce bed roughness. This roughness is likely to change spatially along the estuary due to the variations of bedform properties, but also vary in time as a function of the tidal phase (ebb and flood) and discharge. This has wide implications in terms of modelling hydrodynamics and sediment transport in estuaries.
Simulating the impact of future climate change on runoff processes in selected catchments of Slovakia
Authors: Výleta Roman , Aleksić Milica , Sleziak Patrik , Hlavcova Kamila
Published: March 2021

The future development of the runoff conditions, as a consequence of climate change, is of great interest for water managers. Information about the potential impacts of climate change on the hydrological regime is needed for long-term planning of water resources and flood protection.

The aim of this study is to evaluate the possible impacts of climate change on the runoff regime in five selected catchments located in the territory of Slovakia. Changes in climatic characteristics (i.e., precipitation and air temperature) for future time horizons were prepared by a regional climate model KNMI using the A1B emission scenario. The selected climatic scenario predicts a general increase in air temperature and precipitation (higher in winter than in summer). For simulations of runoff under changed conditions, a lumped rainfall-runoff model (the TUW model) was used. This model belongs to a group of conceptual models and follows a structure of a widely used Swedish HBV model. The TUW model was calibrated for the period of 2011 – 2019. We assumed that this period would be similar (to recent/warmer climate) in terms of the average daily air temperatures and daily precipitation totals. The future changes in runoff due to climate change were evaluated by comparing the simulated long-term mean monthly runoff for the current state (1981-2010) and modelled scenarios in three time periods (2011-2040, 2041-2070, and 2071-2100). The results indicate that changes in the long-term runoff seasonality and extremality of hydrological cycle could be expected in the future. The runoff should increase in winter months compared to the reference period. This increase is probably related to a rise in temperature and anticipated snowmelt. Conversely, during the summer periods, a decrease in the long-term runoff could be assumed. According to modelling, these changes will be more pronounced in the later time horizons.

It should be noted that the results of the simulation are dependent on the availability of the inputs, the hydrological/climate model used, the schematization of the simulated processes, etc. Therefore, they need to be interpreted with a sufficient degree of caution
Calcium [Ca] tracers using X-Ray fluorescence (XRF) as a potential high throughput measurement technique in ringless highly diverse tropical ecosystems.
Authors: Hufkens Koen , Regeur Solenn , Rivard Camille , Van den Bulcke Jan , Beeckman Hans , De Mil Tom , Wingate Lisa
Published: March 2021

Our understanding of plant responses to climate change, and their feedbacks to the climate system, rely heavily on consistent long-term observations. Yet, measuring tropical plant species is particularly demanding and results in a lack of spatial and temporal coverage to build relationships between forest dynamics and climatology in the central Congo Basin. Here dendrochronology and wood chemical analyses might provide important ecophysiological information addressing this knowledge gap, especially in tropical forests where the lack of a pronounced seasonality often makes it difficult to discern variability in xylem cell size and density. Conventional optical dendrochronology measurements therefore have strong limitations within these ecosystems, however chemical and elemental analysis can provide additional information. For example, seasonal fluctuations in the carbon (δ13C) and oxygen (δ18O) stable isotope composition of cellulose is linked to variations in local climate and changes in physiological function. A fewstudies have shown that intra-annual and inter-annual variations in the content of calcium [Ca] in tropical tree rings can be used to age tropical trees without rings, constraining estimates of biomass accumulation. Other studies have linked calcium accumulation in different plant organs to the rate of transpiration in trees making it a powerful predictor of inter-annual variability in rainfall for monsoon regions and a strong novel proxy for drought stress.

Here we present the first results of X-ray Fluorescence (XRF) measurements conducted at the SOLEIL synchrotron and analysis of [Ca] and [Sr], combined with ancillary data such as anatomical, stable isotope and climatological measurements for three tropical tree species. Most species show variability in calcium corresponding to previous proxy measurements, corroborating previous results and showing the potential of non-destructive XRF measurements of wood samples in support of ecophysiological research. The potential of high throughput scanning, in contrast to stable isotope measurements, opens possibilities to gather data on the large scale required to understand diverse tropical forest ecosystems and their responses to (drought) disturbances.
On mineral dust hygroscopicity
Authors: Tang Mingjin , Chen Lanxiadi , Peng Chao , Gu Wenjun
Published: March 2021

Despite its importance, hygroscopicity of mineral dust aerosol remains highly uncertain. In this work, we investigated water adsorption and hygroscopicity of different mineral dust samples at 25 ∘C, via measurement of sample mass at different relative humidity (RH, up to 90 %) using a vapor sorption analyzer. Mineral dust samples examined (21 in total) included seven authentic mineral dust samples from different regions in the world and 14 major minerals contained in mineral dust aerosol. At 90 % RH, the mass ratios of adsorbed water to the dry mineral ranged from 0.0011 to 0.3080, largely depending on the BET surface areas of mineral dust samples. The fractional surface coverages of adsorbed water were determined to vary between 1.26 and 8.63 at 90 % RH, and it was found that the Frenkel–Halsey–Hill (FHH) adsorption isotherm could describe surface coverages of adsorbed water as a function of RH well, with AFHH and BFHH parameters in the range of 0.15–4.39 and 1.10–1.91, respectively. The comprehensive and robust data obtained would largely improve our knowledge of hygroscopicity of mineral dust aerosol.
PRISMA Hyperspectral – First insights in the performance in urban surface cover and coastal seascape analysis
Authors: Poursanidis Dimitris , Chrysoulakis Nektarios
Published: March 2021

The characterization of the Earth’s surface cover based on predefined classes is among the fundamental activities in the domain of satellite image analysis image since the early 70s. It was the joint NASA/ U.S. Geological Survey Landsat series of Earth Observation satellites that start to continuously acquired images of the Earth's land surface, providing uninterrupted data to help land managers and policymakers make informed decisions about natural resources and the environment. However, in 2020, the collected data even if are of continuous flow in terms volume of terrabytes per day from various optical and radar systems, are limited in terms of spectral resolution since almost all sensors are limited to a maximum of 25 spectral channels in the visible, near-and-shortwave-and-thermal infrared spectrum. The need of denser spectral information has been highlighted in early 80s and the first satellite-based hyperspectral sensor, AVIRIS, start to provide data allowing the extraction information on material composition and precise surface cover information. Since then few attempt appear but more are undergoing for launching. In 2019, the Italian Space Agency launch the PRISMA hyperspectral satellite which collect spectral data in the 400-2500nm spectrum; in total 250 spectral channels with a spectral width of ~ 12nm, at 30m pixel size. Here we present first results of the use of Level 2D PRISMA hyperspectral data in mapping the surface characteristics of the urban and periurban area of Heraklion city along with the coastal zone of the urban front aiming at the simultaneous creation of a land-and-coastal cover map along with the extraction of coastal bathymetry information using artificial intelligence approaches within open access platforms. The use of hyperspectral information allow the separation of urban surfaces based on material signatures, while the availability of dense spectral information in the blue-green spectrum allow the more accurate retrieval of coastal seascape characteristics. It is envisaged that hyperspectral missions soon to be the normal in Earth Observation, allowing the accurate creation of geospatial information for further use in several applications.
The Deflection of the Vertical, from Bouguer to Vening-Meinesz, and Beyond – the unsung hero of geodesy and geophysics
Authors: Jekeli Christopher
Published: March 2021

When thinking of gravity in geodesy and geophysics, one usually thinks of its magnitude, often referred to a reference field, the normal gravity.  It is, after all, the free-air gravity anomaly that plays the significant role in terrestrial data bases that lead to Earth Gravitational Models (such as EGM96 or EGM2008) for a multitude of geodetic and geophysical applications.  It is the Bouguer anomaly that geologists and exploration geophysicists use to infer deep crustal density anomalies.  Yet, it was also Pierre Bouguer (1698-1758) who, using the measured direction of gravity, was the first to endeavor a determination of Earth’s mean density (to “weigh the Earth”), that is, by observing the deflection of the vertical due to Mount Chimborazo in Ecuador.  Bouguer’s results, moreover, sowed initial seeds for the theories of isostasy.  With these auspicious beginnings, the deflection of the vertical has been an important, if not illustrious, player in geodetic history that continues to the present day.  Neglecting the vertical deflection in fundamental surveying campaigns in the mid to late 18th century (e.g., Lacaille in South Africa and Méchain and Delambre in France) led to errors in the perceived shape of the Earth, as well as its scale that influenced the definition of the length of a meter.  The vertical deflection, though generally excluded from modern EGM developments, nevertheless forms a valuable resource to validate such models.  It is also the vertical deflection that is indispensable for precision autonomous navigation (i.e., without external aids such as GPS) using inertial measurement units.  It is the deflection of the vertical that, measured solely along horizontal lines, would readily provide geoid undulation profiles, essential for the modernization of height systems (i.e., vertical geodetic control) without the laborious and traditional methods of spirit leveling.  But, measuring the deflection of the vertical is itself an arduous undertaking and this has essentially contributed to its neglect and/or underusage.  Even Vening-Meinesz’s formulas of convolution with gravity anomalies do not greatly facilitate its determination.  This presentation offers a review of the many roles the vertical deflection has, or could have, played over the centuries, how it has been measured or computed, and how gravity gradiometry might eventually awaken its full potential.
Numerical Simulation for Coastal Area Inundation and its Application 
Authors: Son Kwang Ik , Jeong Woochang , Oh Seboong
Published: March 2021

Many extreme sea level rise events, such as tsunami and surges, caused by abnormal climate change results sea level rise to frequent and serious flooding at coastal basins. The Typhoon Mamie resulted 200M US dollars property damage, 3 thousand family refugees, and 14 victims at Changwon city in 2003.  Furthermore, it is expected that the extreme sea level rise events due to abnormal climate change might be getting frequent and serious as times go by.

In this study, a numerical simulation and analysis of flood inundation in a small-scale coastal area had been carried out. The applied numerical model adopts two-D finite volume method with a well-balanced HLLC(Harten–Lax–Van Leer contact) scheme. The calibration was performed with comparison between simulation results and real inundated records of Changwon city during the typhoon “Maemi” in September 2003.

The model was developed to provide overflow simulation capability of parapet wall along coastal line as boundary conditions. Inundation scenarios were simulated with various parapet wall heights and analyzed the efficiency of disaster prevention measures from inundation due to sea level rise.

Numerical inundation simulation study showed efficiency of parapet walls along coastal line as one of the structural measures. It was found that the inundation volume could be reduced with respect to non-parapet wall by providing parapet wall along coastal line. In addition, the economic analysis between damages due to inundation and construction cost for parapet wall was performed for optimal disaster prevention design.

Acknowledgement: This work was supported by Korea Environment Industry & Technology Institute(KEITI) though Water Management Research Program, funded by Korea Ministry of Environment(MOE)(79608). and Korean NRF (2019R1A2C1003604)