bluuebunny/crossref_metadata_2025 huggingface dataset:
Observed Relationships between Cloud Fraction Trends of Shallow and Free-atmosphere Clouds
Authors: Liu Huan , Koren Ilan , Altaratz Orit
Published: March 2022

Clouds play a critical role in the climate system by modifying incoming and outgoing radiation. In turn, clouds are affected by climatic changes. Cloud fraction (CF, the part of the sky covered by clouds) is one of the most reliable observed cloud properties and can be regarded as a good first approximation for cloud radiative effects.

Different types of clouds modify the energy budget and respond to climatic changes differently. Current climate models predict a negative trend in CF of shallow clouds (with low top height), which will further warm the climate by reducing the reflection of solar radiation. For other types of clouds, the predicted trend in CF has a net-zero radiative effect. The modeled results suffer from large variability and it contributes greatly to the uncertainty of climate projections. Therefore, observational constraints are badly needed.

Here, we divide the cloud records into three classes: total clouds (including all clouds), shallow clouds (with top pressure > 700 hPa), and free-atmosphere clouds (other than shallow). For each class, we decompose the general CF into two parts: one which is related to clouds’ horizontal size (CF under cloudy conditions) and a second part, related to the frequency of occurrence (the ratio of cloudy days to all days). 17 years (2003-2019) of satellite observations (MODIS aboard Aqua) and reanalysis data (ERA5) are used in this work. Satellite records show significant regional CF trends. They show that: (1) the trend in shallow clouds’ size dominates the trend in total CF, (2) there are opposite trends between the shallow and free-atmosphere clouds’ occurrence, and (3) the trend in shallow clouds’ occurrence compensate the trend in shallow clouds’ size and lead to a weak trend in shallow CF. It can indicate the development of shallow clouds into free-atmosphere clouds and it can relate to an overlapping problem, where MODIS cannot detect shallow clouds under other clouds. Reanalysis data reveals that after considering a correction for the overlapping problem of cloudy layers, the observed opposite trends (point no. 2 above) are still detected, but to a smaller extent, indicating that this relationship in MODIS records is impacted by the clouds overlapping problem. This means that when considering a correction for the overlapping problem, larger local trends in shallow clouds’ CF (point no. 3 above) are expected. Our findings provide new statistical relationships between clouds’ trends by high-quality observational records and shows that the overlapping problem biases systemically the trends in cloud properties.
Tracking blue ice in time: deriving Antarctic blue ice fraction from MODIS images using spectral unmixing
Authors: Hu Zhongyang , Kuipers Munneke Peter , Lhermitte Stef , Dirscherl Mariel , Ji Chaonan , van den Broeke Michiel
Published: March 2022

Antarctic Blue Ice Areas (BIAs) are a sensitive indicator for climate change. They can be formed either by wind and sublimation or by surface melt, and vary over time. In this regard, distinguishing different blue ice types and observing their change over time can enhance our understanding of climate change in Antarctica. Presently, the areal extent of BIA is retrieved using Earth observation satellites. However, such products rarely provide time series of BIA extent over the entire continent. To fill this gap, we derived blue ice fraction over Antarctica from the moderate resolution imaging spectroradiometer (MODIS) using spectral mixture analysis. Blue ice fraction is defined as the fraction of each MODIS pixel that is covered by blue ice. The results provide a continuous time series of blue ice fraction during the austral summers 2000 to 2021. This time series shows Antarctic blue ice abundance and exposure over time, and indicates that melt-induced BIAs are more variable in time than wind-induced.  According to the accuracy assessment based on high-resolution Sentinel-2 images over six selected test sites in coastal East Antarctica, the blue ice fraction results have an overall uncertainty of around 15% and 25% in wind- and melt-induced BIAs, respectively. The uncertainties mainly arise due to the very similar spectral profiles among melt streams, lakes, and ponds. Overall, our results show great potential in (1) generating annual BIA maps, (2) separating wind-and melt-induced BIAs, (3) evaluating (regional) climate model outputs, and (4) deriving temporal variations in blue ice abundance and exposure.
Effects of subduction termination processes on continental lithosphere
Authors: Pilia Simone , Davies Rhodri , Hall Robert , Bacon Conor , Gilligan Amy , Greenfield Tim , Tongkul Felix , Rawlinson Nicholas
Published: March 2022

Subduction is the main driver of tectonic activity on Earth. Termination of subduction is followed by diverse and unexpected tectonic activity, such as anomalous magmatism, exhumation, subsidence and subsequent rapid uplift. What fundamentally drives these processes remain enigmatic. A prime example of subduction termination can be found in northern Borneo (Malaysia), where subduction ceased in the late Miocene and was followed by puzzling tectonic activity, as reconstructed from geological and petrological evidence. Our current understanding of the subduction cycle cannot be reconciled with evidence of post-subduction tectonics in both the near-surface geology and mantle of northern Borneo.

We use new passive-seismic data to image at unprecedent detail a sub-vertical lithospheric drip that developed as a Rayleigh-Taylor gravitational instability from the root of a volcanic arc, which formed above a subducting plate. We use thermo-mechanical simulations to reconcile these images with time-dependent dynamical processes within the crust and underlying mantle, following subduction termination. Our model predictions illustrate how significant extension from a downwelling lithospheric drip can thin the crust in an adjacent orogenic belt, causing lower crustal melting and possible exhumation of subcontinental material, which can explain core-complex formations seen in other areas of recent subduction termination.
Dependence of lightning occurrence in Europe on large-scale flow patterns
Authors: Ghasemifard Homa , Groenemeijer Pieter , Battaglioli Francesco , Pucik Tomas
Published: March 2022

There is ample evidence that the occurrence of deep convection changes as a result of global warming and that, across Europe, increases in convective instability as measured by CAPE are an important driver in many regions. This study is a first step in disentangling the role that climate change induced changes in flow pattern occurrence plays on the evolution of the frequency of thunderstorms. Here we evaluate the association between large-scale flow patterns with the (temporal and spatial) distribution of lightning in Europe as detected by the Met Office Arrival Time Difference Network (ATDnet). The seasonal cycle shows that the largest number of lightning days occurs in the summer from May to August, the period we, therefore, focus on. The large-scale flow pattern is expressed using the daily mean 500 hPa geopotential extracted from ERA5 reanalysis data. A hierarchical clustering algorithm (Ward's method) is applied to the daily mean geopotential heights in the selected four-month period between 2007 and 2019. The algorithm produces 9 patterns (Fig. 1), with cluster 1 being the most frequent, occurring around 20% of the time and pattern 3 being the least frequent, occurring around 4% of the time. The distributions of lightning associated with the clusters show that lightning often occurs in synoptically quiescent conditions or even underneath a ridge. Furthermore, lightning occurrence over western Europe seems to be more dependent on the synoptic situation, where it is strongly associated with clusters that have a southerly flow at 500 hPa, compared to lightning over the Alpine range or south-eastern Europe.

 

<img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.7cea6e95add166085191461/sdaolpUECMynit/22UGE&app=m&a=0&c=81d9a7497a5e9b1fbe32ac000c6e095c&ct=x&pn=gnp.elif&d=1" alt="" width="720" height="720">

Fig. 1: Large-scale flow patterns are shown in nine clusters, geopotential heights of ERA5 at 500 hPa are plotted in the foreground with 50hPa intervals, and the mean number of lightning strikes per day is shown as filled contours.
Typologies of community risk to climate change: fostering climate adaption networks 
Authors: Riach Nils , Glaser Rüdiger
Published: March 2022

Adapting to the effects of climate change will increasingly become a task of municipal planning and implementation in the coming years. This ranges from the consideration of increasing heat days to the retention of heavy rainfall. Climate related hazards, together with their dynamic interplay of exposure and vulnerability pose considerable adverse consequences for municipalities and need to be addressed through risk management plans. While this is understood in research and is increasingly being implemented in cities, it is found that particularly small and medium-sized municipalities often lack (1) the necessary evidence base for planning, (2) adequate capacities to engage in adaptation, and (3) practical analytical tools and informal planning instruments for adapting to the unavoidable consequences of climate change. Identifying communities that are similarly impacted and thus show comparable adaption needs can help local stakeholders in forming climate adaption networks. Here they can pool resources, develop solutions and exchange knowledge on the highly contextual challenges of climate change adaptation.

We derive cluster based typologies of communities in the German state of Baden-Württemberg, which show assimilable characteristics in climatic hazards, exposure and vulnerability.   While cluster analysis is often used to differentiate patterns of climate change, few assessments have included societal variables. We therefore couple a ten-member regional climate model ensemble (RCP8.5, 1971-2000, 2021-2050, 2071-2100) with socio-economic data in so-called bivariate climate impact maps. This allows for statewide community specific conclusions on climate related risks. Statistical cluster analysis enables grouping of communities based on similar risks and adaption needs. Our approach provides a data driven basis for so-called climate adaption networks, which may foster the implementation of communal adaption efforts.
Short-term asynchrony of root and shoot growth links to soil carbon flux dynamics
Authors: Nair Richard , Strube Martin , Schrumpf Marion , El-Madany Tarek , Migliavacca Mirco
Published: March 2022

Root dynamics and allocation belowground are a major uncertainty in ecosystem studies because roots are hard to measure in comparison to leaves, which can be assessed at fine timescales using a variety of remote sensing approaches. We built an automated minirhizotron system capable of taking root images on a sub-daily scale and analyzed all high frequency images from this with a neural network approach. We pair this with a daily series of above-ground vegetation indexes of the same plants from standardized ‘phenocam’ digital camera methods. Here we will demonstrate, from a mesocosm experiment that 1) in a mixed species mesocosm, root and shoot production (i.e. rate of change of indexes) as not synchronized on short (multi-day) timescales and 2) root growth rate was more important than overall biomass and leaf growth rate in determining variability in soil CO2 efflux. Hence this efflux was likely driven by root growth respiration rather than maintenance respiration. We also show the first results from applying similar principles to ecosystem measurements. 
How studying solidified, exposed magma chambers helps to interpret volcano deformation and pre-eruptive unrest
Authors: Burchardt Steffi , Rhodes Emma , Mattsson Tobias , Witcher Taylor , Schmiedel Tobias , Ronchin Erika , Greiner Sonja , Quintela Orlando , Barker Abigail C.
Published: March 2022

The remnants of kilometre-sized solidified magma bodies exposed in volcanic areas are the product of magma accumulation beneath active volcanoes. These magma bodies can have formed over time spans ranging from months to hundreds of thousands of years, and some have triggered unrest and fed eruptions at the volcano surface. Here, we focus on melt-dominated magma bodies in the upper crust, which represents a sub-volcanic magma-storage level overlying a deeper, likely mush-dominated, igneous plumbing system. Based on several examples in eastern Iceland, we present field observations, structural analyses, 3D reconstructions, and petrological and fabric analyses that shed light on (1) the growth of magma chambers during single, fast, or multiple, long-term, magma injection events and (2) the deformation of the surrounding host rock as a result of different styles of magma emplacement. Moreover, we present evidence for syn-emplacement eruptions from one of the field examples.

We then discuss how field studies of solidified upper crustal magma chambers can inform the interpretation of volcanic unrest signals at active volcanoes. For instance, certain styles of magma emplacement create pronounced surface deformation and seismicity, while others may show initial seismicity that resembles dyke and/or sill emplacement but then allows for the emplacement of vast amounts of magma at shallow depth. This emplacement can likely happen without any significant surface deformation and with very little seismicity. Hence, solidified, exposed magma chambers that formed in the upper crust can provide valuable clues to improve eruption risk and volcano hazard assessment.
Chemical characterization of volcanic plumes with multifunction UAVs and extra-lightweight drones: Concepts and first applications
Authors: Karbach Niklas , Geil Bastien , Gutiérrez Xochilt , Hoor Peter , Dötterl Anselm , Bobrowski Nicole , Hoffmann Thorsten
Published: March 2022

Investigating the chemical composition of volcanic plumes is an important method for obtaining geochemical information of volcanic systems, determining the environmental impact of volcanic outgassing and providing indications of impending activity of the volcano under investigation. However, sampling is not easy, particularly because of immediate meteorological influences on volcanic plume dispersion, but also, of course, because of potential hazards associated with sampling immediately at the rim of volcanic craters. 

When remote sensing methods are not available, UAVs offer the possibility of bringing measurement systems to the scene. Standard parameters that are commonly measured are SO2 and CO2, as well as a number of atmospheric state parameters such as pressure, temperature, and relative humidity. In flight data transmission via radio telemetry plays a significant role, as of course both orography and current meteorology make it otherwise difficult to locate the volcanic plume from several kilometers away. In addition to key components such as SO2, CO2, and water, there are also a number of other components of interest to geoscientists, such as H2S, CO, H2, and halogen compounds. Larger drones, such as the DJI Matrice M210 or the DJI M300, can be used to fly those research based measurement systems in parallel. This allows for the chemical characterization of highly transient plume structures simultaneously at two locations or at large distances from the source including the free troposphere. Results of such measurements carried out at Mt Etna and Vulcano Island, Italy during the last two years are presented in this contribution. Larger drone systems (with the DJI Matrice M210, DJI M300) have the disadvantage that they have a comparatively high weight and therefore make it difficult to bring to the sampling site which might not be accessible by car. Smaller drones like the DJI Mavic 3 significantly reduce the weight one has to carry. In addition, the relatively high cost of the larger drone systems prevents their use for daily monitoring tasks. Therefore, we have equipped a comparatively small drone (DJI Mavic 3) with suitable radio telemetry and sensors to gather basic chemical information in volcanic plumes with an extra-lightweight system. We will introduce this new miniaturized instrumentation and present first results of measurements with the new setup.
A method for adjusting design stormpeakedness to reduce biasin hydraulic simulations
Authors: Muhandes Samer , Dobson Barnaby , Mijic Ana
Published: March 2022

In the UK, decision-makers use hydraulic model outputs to inform funding, connection consent, adoption of new
drainage networks and planning application decisions. Current practice requires the application of design storms to
calculate sewer catchment performance metrics such as flood volume, discharge rate and flood count. With flooding
incidents occurring more frequently than their designs specify, hydraulic modelling outputs required by practice are
questionable. The main focus of this paper is the peakedness factor (ratio of maximum to average rainfall intensity)
of design storms, adjudging that this is a key contributor to model bias. Hydraulic models of two UK sewer
catchments were simulated under historical storms, design storms and design storms with modified peakedness to
test bias in modelling outputs and the effectiveness of peakedness modification in reducing bias. Sustainable
drainage systems (SuDS) were implemented at catchment scale and the betterment achieved in the modelling outputs
was tested. The proposed design storm modification reduced the bias that occurs when driving hydraulic models
using design storms in comparison with historical storms. It is concluded that SuDS benefits are underestimated when
using design rainfall because the synthetic rainfall shape prevents infiltration. Thus, SuDS interventions cannot
accurately be evaluated by design storms, modified or otherwise.
Geometry of overdeepenings obtained through three-dimensional gravity modelling
Authors: Bandou Dimitri , Schlunegger Fritz , Kissling Edi , Marti Urs , Schwenk Michael , Schläfli Patrick , Douillet Guilhem , Mair David
Published: March 2022

We investigated the formation mechanism of tunnel valleys, by producing 3D models of bedrock topography using gravimetry. We obtained the cross-sectional geometry of tunnel valleys in the Swiss foreland, near Bern. The combination of information about the densities of the sedimentary fill and of the bedrock together with borehole data and gravity surveys along profiles across the valleys served as input for our 3D gravity modelling software, Prisma. This finally allowed us to model the gravity effect of the Quaternary fill of the overdeepenings and to produce cross-sectional geometries of the overdeepenings. We focused on two sections situated in the Gürbe valley and in the Aare valley. We determined a density of 2’500 kg/m3 for the Upper Marine Molasse bedrock, and with Prisma we obtained a bulk density of kg/m3 for the Quaternary infill. Our gravity surveys across the valleys yielded a maximum residual anomaly of -2.9 mGal for the Gürbe valley and -4.1 mGal for the Aare valley. The application of our Prisma model showed that these anomalies can be explained by Quaternary suites with a thickness of 160 m and 235 m for the infill of the Gürbe and Aare valleys, respectively. The high-resolution information about the cross-sectional geometry of the tunnel valley flanks, from the application of Prisma, allowed us to infer a two-step formation process of the overdeepened trough.  A first glaciation, during MIS 6 or before, would have deepened the trough. And a second glaciation, during the Last Glacial Maximum  (MIS 2), would have widened the valleys. We explain this pattern by the differences between the ice thicknesses of the LGM and MIS 6 glaciers and by the relatively low erodibility of the Upper Marine Molasse bedrock. The Molasse units indeed comprise tender and porous sandstones and offer a lower erosional resistance than the Quaternary infill, which consists of cohesive and thus competent glacio-lacustrine marls. This probably offered ideal conditions for the thick and thus erosive MIS 6 glaciers to erode deeply into the Molasse bedrock. In contrast, the lacustrine fill of this trough possibly prevented the thinner and thus less erosive LGM or MIS 2 glaciers to further incise the bedrock. The consequence was that erosion of the LGM glaciers mainly occurred on the lateral sides, thereby resulting in a widening of the tunnel valleys. Finally, we apply this approach to the remaining gravity profiles, to create a 3D model of the geometry of the overdeepening network near Bern.
Monitoring present-day Saharan dust at sea
Authors: Stuut Jan-Berend , Guerreiro Catarina , Brummer Geert-Jan , van der Does Michèlle
Published: March 2022

Mineral dust plays an important role in the ocean’s carbon cycle through the input of nutrients and metals which potentially fertilise phytoplankton, and by ballasting organic matter from the surface ocean to the sea floor. However, time series and records of open-ocean dust deposition fluxes are sparse. Here, we present a series of Saharan dust collected  between 2015 and 2020 by dust-collecting buoys that are monitoring dust in the equatorial North Atlantic Ocean as well as by moored sediment traps at the buoys' positions at ~21°N/21°W and ~11°N/23°W. We present dust-flux data as well as particle-size distribution data, and make a comparison of the dust collected from the atmosphere at the ocean surface with the dust settling through the ocean and intercepted by the submarine sediment traps. See: www.nioz.nl/dust
Revealing hidden tipping in spatially-resolved Earth system analysis
Authors: Loriani Sina , Sakschewski Boris , Abrams Jesse F. , Drüke Markus , Lenton Timothy , Wunderling Nico , Zimm Caroline , Winkelmann Ricarda
Published: March 2022

The assessment of potential tipping elements in the Earth system and their associated tipping thresholds is essential for understanding long-term Earth system change and describing a safe operating space. However, their identification in model outputs and observational data typically requires making assumptions about the spatial extent of individual elements. While the resulting regional to continental aggregates allow for the study of collective time series, they are potentially based on subjective judgement and could mask non-linear behaviour on smaller scales.

In this work, we present a novel method based on a timescale- and variable-independent metric to automatically identify potential tipping elements in the Earth system with a few or no free parameters. Gridded datasets are scanned for abrupt shifts on the grid-cell level, which are subsequently automatically clustered in space and time. This allows for the creation of maps with areas grouped and classified by their dynamical behaviour without an a-priori definition of connected regions.

Applying the presented method to various Earth System model outputs, we detect clusters with different nonlinear responses to future emission scenarios which are otherwise masked. Consequently, our bottom-up approach provides insight into the spatial structures and temporal processes of large-scale tipping elements, and sheds light on ‘hidden’ tipping of their subsystems.

 
Advanced processing strategies for an improved GFZ GRACE/GRACE-FO Level-2 data release
Authors: Hauk Markus , Murböck Michael , Panafidina Natalia , Dahle Christoph , Wilms Josefine , Flechtner Frank , König Rolf
Published: March 2022

GFZ, as part of the GRACE/GRACE-FO Science Data System, is one of the official Level-2 processing centers routinely providing monthly gravity models. These models are used by a wide variety of geoscientists to infer mass changes mainly at the Earth’s surface. While the current release 6 (RL06) is still operationally processed, plans and internal tests for a reprocessed GFZ RL07 time series are already in progress.

In this context, recent developments have been made within the Research Unit (RU) NEROGRAV (New Refined Observations of Climate Change from Spaceborne Gravity Missions), funded for 3 years by the German Research Foundation DFG. The central hypothesis of this RU reads: “Only by concurrently improving and better understanding of sensor data, background models, and processing strategies of satellite gravimetry, the resolution, accuracy, and long-term consistency of mass transport series from satellite gravimetry can be significantly increased; and only in that case the potential of future technological sensor developments can be fully exploited.” Two of the individual projects within the RU closely interact on optimized space-time parameterization (reducing non-tidal temporal aliasing error effects) and stochastic modeling regarding instrument data (accelerometer and inter-satellite ranging observations) as well as background models (e.g. by the utilization of covariance information for ocean tides).

This presentation provides an overview of the developed advanced processing strategies, and their individual and combined impact on GFZ’s Level-2 products compared to current GFZ RL06 solutions.
A database of microphysical and optical properties of thin to thick cirrus clouds derived from bimodal particle size distributions
Authors: Spang Reinhold , Spelten Nicole , Krämer Martina
Published: March 2022

The detailed information on the particle size distributions (PSDs) of ice clouds is essential for various topics of radiative transport in a cloudy atmosphere. However, retrieval of microphysical and optical properties from PSDs from remote sensing instruments are affected by a lack in the information content of the measurement quantities, which does not allow to retrieve all parameter of a PSD. Usually, cirrus PSD parameterizations based on in situ measurements are used to reduce the number of unknowns in the retrieval process. The same arguments are applicable for model calculation on the radiative impact of cirrus clouds, where cirrus can have a warming or cooling effect depending on their microphysical (size, number, and shape) and macrophysical  (thickness and height) properties. Detailed information on the PSD shape are essential to improve the retrievals with forward models, where usually a priori information on the shape of the PSD are required, and for radiative transfer calculation for the quantification of the cloud radiative effect of cirrus. 

Here, we will present a more detailed analysis of the PSD measurements compiled in a recent large database (see Krämer et al., 2022, EGU, AS 1.15). With 11 campaigns and 238 flight hours in cloud conditions the database is currently the most comprehensive datasets for studying PSD parameters and the potential importance of the bimodality of ice cloud PSDs. The PSDs are not affected by the so-called shattering effect and cover for all campaigns particle diameters down to 3 microns. 

The procedure to derive microphysical and optical properties from the measured PSDs is to select predefined ice water content (IWC) and temperature grids for computing mean conditions. The database covers IWC from 10-6 to 1 g/m3 and is especially well-suited to investigate optically thinnest clouds hitherto not included in PSD data bases. Other gridding parameters have been also investigated, for example number density. An iterative approach for fitting bimodal lognormal functions to the measured PSD by minimizing a cost function have been applied to the data with overall good fitting results. Characteristics of the fitted PSDs and the corresponding microphysical and optical properties will be presented.    

 
Scientific evolution of the International Soil Moisture Network: Past, present, and future developments in support of soil moisture validation and applications
Authors: Petrakovic Ivana , Himmelbauer Irene , Aberer Daniel , Schremmer Lukas , Goryl Philippe , Crapolicchio Raffaele , Sabia Roberto , Scipal Klaus , Dietrich Stephan , Olarinoye Tunde , Böhmer Fay , Dorigo Wouter
Published: March 2022

With its steadily growing provider and user community (4000 active users), the International Soil Moisture Network (ISMN, https://ismn.earth)  is a unique centralized global data hosting facility, making in-situ soil moisture data easily and freely accessible. 

The main goal of the ISMN in the past decade was to build up the harmonized and quality-controlled in-situ soil moisture source it is today.

The ISMN provides benchmark data for several operational services such as ESA CCI Soil Moisture, the Copernicus Climate Change (C3S) and Global Land Service (CGLS), and the online validation tool QA4SM (https://qa4sm.eu). ISMN data is widely used for support of algorithm development and validation of different satellites, evaluation of soil moisture products, as a training set for various data-driven approaches, model developments, drought monitoring and diverse meteorological applications (Dorigo et. al 2021).

In this presentation, we will provide an overview of the ISMN scientific achievements accomplished in the last decade, show recent scientific and service developments, and present foreseen future developments.

We provide a review of hundreds of papers making use of ISMN data to identify major scientific breakthroughs facilitated through the ISMN. We also identify current limitations in data availability, functionality and challenges in data usage (e.g., in-situ data inclusion in data sparse regions, in-situ data inclusion from official governmental observation networks, data and measurement traceability, etc.).

One of the major successes has been the achievement of long-term financial support for the ISMN through the German Ministry of Digital Infrastructure and Transport. Therefore, the ISMN operations is currently transferred from Vienna Austria (TU Wien) to the new host in Koblenz, Germany (International Center for Water Resources and Climate Change - ICWRGC, Federal Institute for Hydrology – BfG).

This evolution not only opens up a stable future for the ISMN but also gives TU Wien once more the opportunity to focus on the scientific development of the ISMN as currently proceeded within the ESA project “Fiducial Reference Measurement for Soil Moisture (FRM4SM)”.  Within this two-year project (May 2021 – May 2023) the goal is also to identify and create standards for independent, fully characterized, accurate and traceable in-situ soil moisture measurements (from the ISMN) with corresponding uncertainty estimations and independent validation methods (inserted in the QA4SM service: https://qa4sm.eu).

 
Hard-coupling of water and power system models increases the complementarity of renewable energy sources
Authors: Koh Rachel , Kern Jordan , Galelli Stefano
Published: March 2022

Multi-sector modelling frameworks are fundamental platforms for exploring the complex interactions between the water and energy sectors. While acknowledging the pivotal role of hydropower within the energy system, it is essential to understand the feedback mechanisms between power and water systems to guide the design of hydropower operations and enhance water-energy management strategies. Here, we developed a novel modelling approach that hard-couples a reservoir system model and a power system model. The two-way dynamic feedback mechanism between the models allows for operational decisions to be made contingent upon the states of both water and energy systems. Operating the system as a whole offers flexibility in managing the physical storage of hydropower reservoirs to buffer the variability in other renewables, such as wind or solar. We evaluate the framework on a real-world case study based on the Cambodian grid, which relies on hydropower, coal, oil and imports from neighboring countries. In light of the country’s plan to further decarbonize its grid, we tested the framework on three grid configurations, the as-is grid, and the grid with two different levels of installed solar. To evaluate the effects of hard coupling, the experiments were simulated with and without feedback, and external inputs were varied with 1,000 stochastic generations of streamflow, solar and load. As demonstrated in our results, hard-coupling the water and energy systems brings benefits such as reduced operating costs, and boosts decarbonization efforts by supporting the integration of renewables in the grid. The two main external factors that determine the effectiveness of the feedback mechanism are streamflow and load. Under favorable conditions (large reservoir inflow and low electricity demand), the system experienced a 44% saving in annual operating costs and 53% reduction of CO2 emissions. A spatio-temporal analysis on the reservoir operations and transmission line usage reveals that the timing of the monsoon and interconnections between the grid components also play significant roles in influencing the system’s responses to the hard coupling. Overall, our modeling framework paves way for optimized operations within the water-energy nexus. By accounting for the interdependencies between the reservoir and power system, a more efficient operating scheme for hydropower reservoirs can be derived, leading to greater complementarity of renewable energy sources.
Effect of hydraulic gradient on the optimal cost of in-situ groundwater bioremediation 
Authors: Pathania Tinesh , Eldho T Iype
Published: March 2022

In the recent times, simulation-optimization (S/O) models are used to design the optimal in-situ bioremediation system for groundwater problems with constant hydraulic gradient. In such problems, the main objective is to achieve the maximum allowable contaminant concentration within a selected remediation period at a minimum cost. At a relatively higher hydraulic gradient, the contaminant moves faster towards the monitoring wells near the aquifer boundaries, therefore, in-situ bioremediation cost increases to eliminate the contaminant within the same remediation time. Here, the effect of different hydraulic gradients on the in-situ bioremediation cost of a hypothetical case study is systematically studied. The S/O model linking meshless element-free Galerkin method (EFGM) based BIOEFGM model with the particle swarm optimization (PSO) algorithm, known as BIOEFGM-PSO, is applied to estimate the optimized in-situ bioremediation cost. In this study, the different hydraulic conditions are created by changing the head values at the downstream boundary. The different combinations of injection and extraction wells are also tested to satisfy the water quality constraints for different gradient conditions.  The results of the above S/O model showed that in-situ bioremediation cost increases with an increase in hydraulic gradient, and more wells are required for remediation within the same duration under a higher hydraulic gradient.
Multiscale analysis of soil moisture variability for a typical semi-arid Mediterranean ecosystem
Authors: Corona Roberto , Montaldo Nicola , Katul Gabriel G.
Published: March 2022

Soil moisture content influences the partitioning of net radiation into latent and sensible heat fluxes that, in turn, affect the dynamics of the atmospheric boundary layer depth and concomitant generation of precipitation. The interactive effect between soil moisture and precipitation has been found to be stronger in areas where soil moisture temporal variability is enhanced such as in arid and semiarid regions, and in transitional regions between dry and wet climate. For this reason, variability in soil moisture at multiple time scales continues to draw attention in climate science and hydrology. In this work, the soil moisture variability at multiple scales for a typical Mediterranean ecosystem, has been quantified using the spectrum of soil moisture.The case study is the Orroli site in Sardinia (Italy), a typical semi-arid Mediterranean ecosystem which is an experimental site for the ALTOS European project of the PRIMA MED program.The spectrum of root-zone soil moisture content for this Mediterranean ecosystem is analyzed using 14-years of half-hourly measurements. A distinguishing hydro-climatic feature in such ecosystems is that sources (mainly rainfall) and sinks (mainly evapotranspiration) of soil moisture are roughly out of phase with each other. For over 4 decades of time scales and 7 decades of energy, the canonical shape of the measured soil moisture spectrum is shown to be approximately Lorentzian determined by the soil moisture variance and its memory but with two exceptions: the occurrences of a peak at diurnal-to daily time scales and weaker peak at near annual time scales. Model calculations and spectral analysis demonstrate that diurnal and seasonal variations in hydroclimate forcing responsible for variability in evapotranspiration had minor impact on the normalized shape of the soil moisture spectrum. However, their impact was captured by adjustments in the temporal variance. These findings indicate that precipitation and not evapotranspiration variability dominates the multi-scaling properties of soil moisture variability consistent with prior climate model simulations. Furthermore, the soil moisture memory inferred by the annual peak of soil moisture (340 d) is consistent with climate model simulations, while the memory evaluated from the loss function of a linearized mass balance approach leads to a smaller value (50 d), highlighting the effect of weak non-stationarity on soil moisture variability. Spatial variability in infiltration rates introduce some whitening of rainfall temporal auto-correlation recovering a spectral decay in soil moisture spectra consistent with  f2 at sub-weekly time scales, where f is the frequency or inverse time scale.
How does the Southern Annular Mode impact ice-shelf basal melt around Antarctica?
Authors: Verfaillie Deborah , Pelletier Charles , Goosse Hugues , Jourdain Nicolas C. , Bull Christopher Y.S. , Dalaiden Quentin , Favier Vincent , Fichefet Thierry , Wille Jonathan
Published: March 2022

The climate of the polar regions is characterized by large fluctuations and has experienced dramatic changes over the past decades. In particular, the patterns of changes in sea ice and ice sheet mass are complex in the Southern Hemisphere. The Antarctic Ice Sheet has also lost mass in the past decades, especially in Western Antarctica, with a spectacular thinning and weakening of ice shelves, i.e., the floating extensions of the grounded ice sheet. Despite recent advances in observing and modelling the Antarctic climate, the mechanisms behind this long-term mass loss remain poorly understood because of the limited amount of observations and the large biases of climate models in polar regions, in concert with the large internal variability prevailing in the Antarctic. Among all the processes involved in the mass variability, changes in the general atmospheric circulation of the Southern Hemisphere may have played a substantial role. One of the most important atmospheric modes of climate variability in the Southern Ocean is the Southern Annular Mode (SAM), which represents the position and the strength of the westerly winds. During years with a positive SAM index, lower sea level pressure at high latitudes and higher sea level pressure at low latitudes occur, resulting in a stronger pressure gradient and intensified Westerlies. However, the current knowledge of the impact of these fluctuations of the Westerlies on the Antarctic cryosphere is still limited. Over the past few years, some efforts investigated the impact of the SAM on the Antarctic sea ice and the surface mass balance of the ice sheet from an atmosphere-only perspective. Recently, a few oceanic studies have focused on the local impact of SAM-related fluctuations on the ice-shelf basal melt in specific regions of Antarctica, particularly Western Antarctica. However, to our knowledge, there is no such study at the scale of the whole Antarctic continent. In this study, we performed idealized experiments with a pan-Antarctic regional ice-shelf cavity-resolving ocean - sea-ice model for different phases of the SAM. We show that positive (negative) phases lead to increased (decreased) upwelling and subsurface ocean temperature and salinity close to ice shelves. A one-standard-deviation increase of the SAM leads to a net basal mass loss of 40 Gt yr-1, with strong regional contrasts: increased melt in the Western Pacific and Amundsen-Bellingshausen sectors and the opposite response in the Ross sector. Taking these as a baseline sensitivity, we estimate last millennium and end-of-21st-century ice-shelf basal melt changes due to SAM of -60.7 Gt yr-1 and 1.8 to 26.8 Gt yr-1 (depending on the emission scenario considered), respectively, compared to the present.
Impact assessment of flood damage on power grid customers
Authors: Asaridis Panagiotis , Molinari Daniela , Di Maio Francesco , Ballio Francesco , Zio Enrico
Published: March 2022

Natural hazards are a leading driver of power outages worldwide. Although flooding has lower impact compared to other natural hazards, it may still have a significant impact on power grids functionality in terms of frequency, magnitude, and duration of power outage. Maintaining the security of power supply under emergency conditions triggered by natural hazards, such as floods, is a challenging task because of the inherent structural and dynamic complexity of the system. In such a context, this paper presents a new model for the estimation of direct, indirect, and systemic flood damage to power grids. The key objective of the model is to be an operational tool able to: (i) consider the magnitude, probability of occurrence, and spatiotemporal variability of flood hazard, (ii) identify the vulnerable components of power grids and evaluate their probability of failure in case of flood, (iii) analyze the cascading effects of individual or multiple failure states on the power transmission and distribution networks, (iv) and assess the impacts of power outages on the power-dependent economic activities and infrastructures. To achieve this goal, the model combines deterministic flood hazard scenarios, a spatially distributed power flow model, fragility curves of power grid components for different voltage levels, and a social model, describing the various users connected to the power grid. For quantitative illustration purposes, a synthetic model has been developed by referring to the IEEE 14 bus system benchmark, to which a spatial dimension has been allocated. Furthermore, to account for differentiated social impacts, the power flow model has been linked to a synthetic social model including several communities (hubs) with different social and economic characteristics.

The development of the synthetic model constitutes a preliminary step in understanding and quantifying the impacts that sustained power interruptions caused by floods can have on the customers of power grids. Next research efforts will be devoted, on the one hand, to the adoption of a probabilistic approach, by substituting deterministic hazard scenarios with spatial dependent, probabilistic ones; on the other hand, to the sensitivity analysis of the different modeling phases to identify the components of the model on which the final damage scenario depends mostly. The final aim is to provide a modeling and simulation tool for risk analysis, so as to enable stakeholders, authorities, and policy makers to formulate effective strategies to guarantee public security and ensure financial well-being.
Do we necessarily need to increase model complexity to forecast soil carbon dynamics?
Authors: Guenet Bertrand , Le Noé Julia , Bruni Elisa , Abiven Samuel , Barré Pierre , Cécillon Lauric
Published: March 2022

The importance of carbon fluxes between soils and atmosphere and their storage capacities have made soils a key component of nature-based solutions to mitigate climate change. Consequently, the need to forecast soil carbon dynamics at the decadal time scales is becoming a key research avenue for soil scientists and biogeochemists. One of the most important tools to fill this objective is the use of models, which have been developed and implemented since the mid- 20th century. Presuming that integrating more mechanisms would improve these models, some models of increased complexity were recently developed. Indeed, since roughly two decades, several approaches have been proposed to better represent the effect of some key mechanisms in particular related to soil biology and soil physics. For instance, few models are now able to describe explicitly and reliably the importance of soil microorganisms on the soil carbon dynamics from plot to global scale. Here, we will discuss what is the rationale behind model complexity increase, what are the limitations associated and discuss the status of evaluation for model prediction. In particular, we will show that despite model of increased complexity may provide accurate predictions in some conditions, those complex models also came with their own implicit assumptions and limitations that must be well understood before using complex models to forecast soil carbon dynamics and feed policy decisions. We also consider that models of lower complexity, which have been generally developed earlier, have also their own assets and have often been better evaluated. As a consequence, models of lower complexity may be considered as more robust and more adapted to forecast soil carbon dynamic and the improvement of their parameterization should also be considered as a valuable alternative. We will also present why multi model approach is important to reduce uncertainties and explain why using model ensemble, when implemented a diversity of carefully evaluated models, is a key method to forecast soil carbon dynamics. Finally, we will show that the fabulous growth of model complexity and the societal needs associated to soil is an incredible opportunity for soil scientists to increase the understanding of soil carbon cycle, in particular in the context of global changes, and to improve our future predictions on soil carbon. 
Eddy covariance flux measurements of methane over an urban area in the Alps
Authors: Stichaner Michael , Karl Thomas , Graus Martin , Lamprecht Christian , Goded Ignacio , Jensen Niels
Published: March 2022

Methane is considered as the second most important contributor to radiative forcing and thus makes it the most important non-CO2 greenhouse gas originated from anthropogenic activities. The investigation of emission sources and the mitigation strategies of these is of major importance. One of several approaches quantifying methane emissions is the top-down eddy covariance flux measurement, which is used in the investigation here.

Long-term eddy covariance flux measurements of methane over urban areas can be used to constrain important urban emission sources. These include traffic, the residential, commercial and public sectors, industry, and biogenic sources. It is believed that a large fraction of methane emissions originates from fugitive emissions, but the magnitude and nature are still poorly constrained. Here we present initial results from long-term measurements at an Alpine city (Innsbruck, Austria), and compare methane fluxes with those available from other locations. We show that a statistical gap filling model allows to compare yearly top-down methane fluxes with bottom-up emission models. The temporal and spatial disaggregation of eddy covariance flux data can be used further to hunt down and identify potential urban emission sources, by combining these fluxes with additional tracer fluxes (e.g. NMVOC, NOx, CO2). An analysis of the methane fluxes referring to heating degree days and weekday/weekend effect combined with similar analysis for trace gases like NOx, provides additional clarity about the origin of the methane emissions (e.g. traffic, residential combustion).

First results from the methane flux measurements performed during the years 2020, 2021 and 2022 are presented here.