bluuebunny/crossref_metadata_2025 huggingface dataset:
Sediment and carbon sequestration on global river delta plains
Authors: Nienhuis Jaap , Vaughn Derrick
Published: March 2022

Delta plains trap some of the sediments and carbon that are carried down rivers. Trapping keeps deltas above sea level, prevents carbon oxidation, and makes their soils fertile. Quantifying the fraction that is trapped (or retained) is tricky because it is a ratio of two uncertain numbers: delta plain accumulation and fluvial supply. Here we present our work that aims to overcome this issue by estimating trapping on large space and time scales. We quantified sediment and particulate organic carbon (POC) trapping for many coastal delta plains (n=4700), from the time or their inception 7000 years ago to the present, using modern global DEMs, estimates of lowstand channel profiles, and model-derived long-term fluvial fluxes. Our preliminary calculations suggest that modern delta plains, on average, have trapped 25% of the supplied sediment and now contain 30,400 Pg (~1.9.104 km3). They trapped 19% of the supplied POC, totalling 119 Pg C. It seems that sediment trapping has increased with time, as delta plain grew larger and gained more space to accumulate sediment. POC trapping might have decreased with time. Deltas grew out of their protective incised valleys and exposed POC to marine processes on continental shelves. Trapping will likely change in the future, but our long-term averages provide a useful baseline against which the additional effects of humans, sea-level rise, and other changes can be assessed.
Humidity regime in the world's mega cities
Authors: Lax Judi (Yehudit) , Saaroni Hadas , Price Colin
Published: March 2022

As urbanization continues to grow, it is expected that by 2050, the currently 55% of the world population living in urban areas will reach 68% (UN, 2016). The 'Urban Heat Island' is the most studied phenomenon in urban areas, but changes are expected also in the atmospheric humidity regime (Ziv & Saaroni, 2011). Generally, an urban dry island has been noted in previous studies (Luo & Lau, 2019).

Following the authors' findings in the field of hygroelectricity (Lax, Price & Saaroni, 2020)– energy extracted from isolated metals exposed to high relative humidity (RH) conditions – as spontaneous voltage accumulated on isolated metals starting from RH > 60%, investigation of suitable regions with high RH and its durations is needed. Such analysis is also applicative for numerous aspects, related to negative impacts caused by high RH, i.e., thermal comfort & health aspects, when associated with high temperatures, allergies related to dust mites & mold, fungi & bacteria survival, corrosion development, etc. However, high RH has advantages as well, moist-reliant renewable energies and moist harvesting for drinking water (Shen et. al., 2020). This is especially relevant in a warming world due to climate change.

Our study explored the climatology of the world's largest 33 mega-cities; High RH distribution & duration spells are analyzed on a seasonal & annual scales, based on a minimum of 10-years hourly data. Moreover, for cities with several stations, a spatial comparison is performed. The atmospheric variables included are not only the cities' RH, but also the specific humidity, dry and wet bulb temperatures and heat load. Cities are ranked in terms of their potential contribution to the above-mentioned technologies on the one hand and to their disadvantages in terms of human comfort on the other. Finally, we propose a tool to determine the potential of these cities for moist-reliant technologies.
Analysis of the filter time scale under stable conditions in mountainous terrain
Authors: Lehner Manuela , Rotach Mathias W.
Published: March 2022

To calculate turbulent fluxes from eddy-covariance measurements, an appropriate filter time needs to be selected to remove non-turbulent larger-scale motions from the raw time series, while retaining all of the turbulent contributions. Common choices include 30 min for convective conditions and 1-5 min for stable conditions. Eddy-covariance data from five i-Box stations in the Austrian Inn Valley are analyzed to determine the appropriate filter time scale under stable conditions using spectral analysis. The i-Box (Innsbruck Box) is a long-term measurement platform, which was designed to study boundary-layer processes in highly complex terrain and has been operational since 2012. The five stations are located in an approximately 6.5-km long section of the 2-3-km wide valley, with one station at the almost flat valley floor, two stations on relatively low-angle slopes of the south-facing sidewall, and two stations on steep slopes of the north-facing sidewall. Different methods, including Fourier analysis and multi-resolution flux decomposition, are tested to determine the filter time scale. As submeso motions affect temperature and the horizontal and vertical wind components differently, not all variances and covariances are equally well suited to identify the time scale. Using the correlation between the identified filter time and the mean near-surface wind speed and stability, the impact of different filter times, including a flexible, time-varying filter time, on near-surface turbulent fluxes is further discussed.
Changes in glacier and snow melt contributions to streamflow in James Ross Island, Antarctic Peninsula
Authors: Jenicek Michal , Nedelcev Ondrej , Kavan Jan
Published: March 2022

Antarctica has been significantly warming in the last decades. According to climate projections, the increase in air temperature is likely to continue in the future, which will affect runoff dynamics due to glacier retreat and changes in snow cover. Despite the large changes in glacier volume in some parts of Antarctica, little is known about streamflow dynamics and contribution of different water sources to total catchment runoff. Therefore, the objective of our research was to 1) describe runoff dynamics in six catchments located in the Ulu Peninsula, James Ross Island, which represents one of the largest deglaciated areas in Antarctica and 2) to assess the inter-annual variations in glacier melt, snowmelt and potentially rain contributions to runoff over the years 2015 – 2021. The study catchments have different glaciation, and thus considerable diurnal regime of streamflow. Streamflow measurements performed in 2018 austral summer were used to describe the streamflow dynamics of the six catchments. Additionally, a conceptual bucket-type catchment model has been set-up for two of the six catchments, first partly glacierized and second without glacier coverage. In-situ measurements of glacier ablations (2015–2019) and daily precipitation and air temperature partly measured directly at automatic weather stations located in the catchments and partly derived from ERA5-land reanalysis were used as model inputs. Since water level and streamflow data are limited for the study area, a genetic algorithm procedure was used to calibrate the model.

Direct streamflow measurements performed in 2018 austral summer showed the largest variations in Triangular and Shark Streams, which represent the most glaciated catchments among all study catchments. The less variable streamflow was found in Algal Stream, a completely deglaciated catchment. Highest streamflow was recorded in late afternoon, whereas minimum streamflow was recorded in late night or early morning which suggests the strong diurnal regime. In glacierized catchments, the streamflow responded fast on increased air temperature and solar radiation during day. In contrast, soil water stored in the active layer and snow patches mostly controlled streamflow dynamics in deglaciated catchments. Besides, the runoff response was somewhat delayed in these catchments compared to glaciated catchments due to temporal subsurface storage. The above findings were proved also by model simulations, which extended streamflow data for the period 2015-2021. Besides, the simulations showed different glacier and snow contributions to total runoff in study catchments and also different times of streamflow responses to changes in meteorological inputs in combination with different catchment storages which influence runoff delays.
Lessons learned from high-school students contribute to exposure database
Authors: Barnaba Carla , Peresan Antonella , Scaini Chiara , Poggi Valerio , Tamaro Alberto
Published: March 2022

The National Institute of Oceanography and Applied Geophysics – OGS is engaged in a wide range of educational and training activities for more than a decade, mainly focused on seismic risk mitigation through data acquisition in the field and practical stages. To by-pass the restrictions imposed by the COVID-19 pandemic, in 2021 OGS started a new project, deployed in fully remote mode, to involve high-school students and increase their risk awareness and preparedness. The Project, named “CEDAS: building CEnsus for seismic Damage Assessment”, consists in the collection and elaboration of data which is included in the exposure database. Knowing the type and distribution of exposed assets, in particular buildings, is thus paramount for effective mitigation of disasters. The students classified and georeferenced the main residential buildings typologies of northeastern Italy, a seismically active area which suffered consequences from strong past earthquakes. During the project, 170 high school students collected reports on more than 3200 buildings, performing a statistical analysis of their results.

The project activities consisted of two main phases: plenary virtual training meetings and individual data collection and processing. Tutors held intermediate meetings with students for verification and discussion and brainstorming sessions with their professors to discuss the efficacy of their actions. All the meetings, including those for direct training of students, were delivered in virtual mode. The training material (including the meeting recordings) was then shared remotely with students and teachers through cloud solutions, and remained available during the whole project. In this way the students were able to both collect basic data for exposure assessment, and carry out their preliminary analysis using standard statistical tools available online. The comparative data analysis, performed for selected sub-areas and for the overall dataset, allowed them for some basic interpretation and a better understanding of the exposed assets situation in sub-areas. The CEDAS project, though motivated by the need to provide a practical solution to the COVID-19-related restrictions, went well beyond the emergency situation, as it demonstrated that training activities can contribute to both enhancing the available exposure dataset and to increasing risk awareness among young students in the region.

 
Translating seasonal climate forecasts into decision-relevant water security forecasts
Authors: MacLeod David , Asfaw Dagmawi , Michaelides Katerina , Otenyo Erick , Tadege Abebe , Segele Zewdu , Otieno George , Hassaballah Khalid , Quichimbo Andrés , Cuthbert Mark , Singer Michael
Published: March 2022

Early warning of drought conditions can help protect lives and livelihoods, especially in dry regions of subsistence agriculture and pastoralism. Regions such as the Horn of Africa Drylands (HAD) may benefit from advance warning of changes to available water supplies, as rural communities make critical decisions about planting and moving livestock at particular points in time. However whilst the regionally-mandated seasonal forecast for HAD provides information on rainfall totals, it does not quantify expected impacts on water balance components such as soil moisture and groundwater storage. This latter information may be more useful to rural communities who rely on groundwater for water resources for humans and livestock, and soil moisture for crop growth. These hydrological quantities can typically be estimated with hydrological models, but in drylands the processes governing water partitioning are complex and largely unrepresented in most existing regional and global hydrological models. 

 

Here we leverage the capability of a dryland-specific hydrological model (DRYP) to produce rainfall-driven water security forecasts for HAD. DRYP incorporates spatially varying rainfall and evaporative demand, dynamic surface-groundwater interactions, ephemeral flow through channels and focused groundwater recharge. We employ DRYP in a pilot application to produce seasonal forecasts of soil moisture and groundwater recharge for a large catchment within the HAD. We use the objective seasonal forecasts provided by the IGAD Climate Prediction and Application Centre (ICPAC) and disseminated within the Greater Horn of Africa Climate Outlook Forum (GHACOF). Methodological approaches to integrate DRYP with the regional climate outlook disseminated by ICPAC are described, along with evaluation of potential skill of these new water security forecasts for the regional pilot catchment. Finally, we describe and update on an active forecast pilot activity, where water security forecasts for the current rainfall season (March-May 2022) have been co-produced with ICPAC and disseminated to stakeholders in February 2022 as part of the GHACOF event, now publicly available via the ICPAC East Africa Hazards Watch platform, under the EU H2020-funded DOWN2EARTH project. Co-design activity arising from recent stakeholder workshops will be described.
Assessing the influence of biogeochemical constraints on the enzymatic degradation and mineralization of peat 
Authors: Heffernan Liam , Grasset Charlotte , Kothawala Dolly , Tranvik Lars
Published: March 2022

Northern peatlands are important long-term sinks of atmospheric carbon (C) due peat accumulation rates greater than rates of decomposition. Slow decomposition in northern peatlands is due to the presence of water saturated and low oxygen conditions, low temperatures, and decay resistant plant litter. The activity of extracellular enzymes produced by soil microbes is the first step in decomposition however, the relative importance of these abiotic and biotic variables in constraining extracellular enzyme activity remains poorly known. To address the multiple proposed mechanisms of what constrains peat enzyme activity, this study manipulates the biochemical controls associated with the inhibition and stimulation of enzyme activity. These biochemical constraints are regulated by abiotic (redox conditions and temperature) and biotic (organic matter source) factors. A 90-day incubation was carried out using peat from hummock and hollow microforms and peat was maintained under oxic and anoxic conditions at 20°C. Replicates of each microform and redox condition was amended as the following treatments: control, Fe addition, phenolics addition, oxidative enzyme addition, pH manipulation, nutrient addition, and pH manipulation and nutrient addition. Extracellular enzyme kinetics and temperature sensitivity (Q10) of 6 hydrolytic and 2 oxidative enzymes was determined for each microform prior to treatment. Respiration rates of CO­2­ and CH4 were monitored throughout the incubation period. Following the termination of the incubation the enzyme kinetics and temperature sensitivity was determined for each treatment. This study provides the first comparison of multiple proposed mechanisms of what constrains peat enzyme activity within a single study. These results improve our understanding of what controls peat decomposition by assessing the relative importance of environmental, biological, and molecular resistance to enzymatic decay.
The effect of brittle-ductile weakening on the formation of detachment faults at ultraslow spreading ridges 
Authors: Liu Mingqi , Rozel Antoine , Gerya Taras
Published: March 2022

Large offset detachment faults form with exhuming mantle-derived rocks into the seafloor at the slow and ultralow spreading ridges. However, their formation mechanism still remains partly elusive.  The thick axial lithosphere of ultraslow spreading ridges detected by seismic studies may prevent the formation of detachment faults. Previous studies have proposed that only the combination of both serpentinization and grain size reduction in the mantle lithosphere can result in detachment faults which are consistent with the natural cases. Here, through 3D self-consistent magmatic-thermomechanical numerical models with both brittle/plastic strain weakening and grain size evolution, we systematically investigate effects of these coupled brittle-ductile weakening processes on the formation of detachment faults at ultraslow spreading ridges. Numerical results show that ultraslow ridges spontaneously break into shorter and warmer magma-rich (10-20% of the ridge length) and longer and colder magma-starved segments (80-90% of the ridge length). Small grain size formed in the deep root of detachment faults near the brittle-ductile transition depth at the magma-starved amagmatic segments. Then with mantle rocks exhumation into the surface, the decreasing temperature leads to the growth of small grain size, consistent with the deformation process of detachment fault systems in the amagmatic segments of the eastern part of the Southwest Indian Ridge. Through quantitatively exploring effects of grain size reduction and strain weakening, we obtained that strain weakening may be the primary factor to control the formation of detachment faults at the ultra-slow spreading ridges, although grain size evolution can also influence the spreading pattern in case of small (<= 1 mm) initial grain size of the lithospheric mantle. Furthermore, we also found that the weak ductile domain induced by the very small initial grain size (<= 0.1 mm) promotes the formation of detachment faults in the models without grain size evolution.
On The Convective Precipitation Contribution during Vb-events
Authors: Hamouda Mostafa , Ahrens Bodo
Published: March 2022

Recent studies have focused on the relationship between global warming and extreme precipitation events. It is consensed that the risk of flooding is increasing due to global warming, since warmer air temperatures accommodates more moisture content according to Clausius-Clapyeron relation. One of the major flood sources is known as Vb cyclones, i.e. cyclones travelling through the Mediterranean then moving northwards on the eastern flank of the Alps towards central Europe. In this study, a special focus is shed on the convection process during major Vb events. Using a convection tracking method (Purr et al. 2021) and mid-tropospheric vertical velocity and vorticity method (Poujol et al.2019) on convective-permitting simulations (3km resolution) driven by ERA5 reanalysis data, the results show that at least one third of the total amount of rainfall is produced by convection. Moreover, the diurnal cycle is found to contribute to enhancing the convective fraction, as the surface becomes warm in the afternoon, setting up suitable conditions for convection to occur. Both methods show similar patterns and comparable amplitudes. The added value of using such a computationally expensive simulation is also investigated, by comparing the results from the convection-permitting simulations to a lower resolution (11 km) downscaling with parameterized convection. Using Poujol et al. (2019) method, the the results do not show a completely accurate rainfall enhancement due to the diurnal cycle; however a comparable fraction due to convection during a Vb event is identified.

 

Purr, C, Brisson, E, Ahrens, B. Convective rain cell characteristics and scaling in climate projections for Germany. Int J Climatol. 2021; 41: 3174– 3185. https://doi.org/10.1002/joc.7012

Poujol, B, Sobolowski, S, Mooney, P, Berthou, S. A physically based precipitation separation algorithm for convection-permitting models over complex topography. Q J R Meteorol Soc. 2020; 146: 748– 761. https://doi.org/10.1002/qj.3706
Evidence for biomass burning-forced dimming in southern Africa
Authors: Ferreira Correa Lucas , Wild Martin , Folini Doris` , Chtirkova Boriana
Published: March 2022

Decadal trends in Surface solar radiation (SSR) have gained attention in the last few decades after several studies identified the non stable behaviour of such measurements. Also referred to as Global Dimming and Global Brightening, these decadal trends are known to be spatially heterogeneous, meaning that different regions might experience different trends, associated with different causes. While measurements have allowed the identification of trends around the world, the understanding of the causes of those trends is limited to a few regional studies mostly focusing on developed countries. The lack of data in developing countries leads to an underrepresentation of those regions in what regards to global dimming and brightening research. In this work, we use around 39 years  (1967-2005) of daily SSR measurements of two stations in Zimbabwe, and apply a new method for clear-sky derivation, using satellite cloud fraction to identify optimal daily transmittance thresholds for clear-sky identification. The all-sky and clear-sky time series of SSR are then compared to cloud fraction and water vapor data from ERA5 reanalysis and to aerosol emissions from the EDGAR database. The SSR time series show a persistent dimming of similar magnitude both in all-sky and clear-sky. The cloud fraction does not show any significant trends, reinforcing the hypothesis that the dimming was caused by cloud-free radiative processes in the atmosphere. The water vapour time series also does not show any significant trend which could justify the negative trends in SSR. However, the monthly interannual variability show that the dimming is stronger between July and September, months with higher emission of biomass burning aerosols in that region. This might also indicate an anthropogenic related cause of the dimming observed in southern Africa. This study intends to contribute to the understanding of the global dimming and brightening phenomena in southern Africa, but also to highlight the importance of studies focusing in underrepresented regions of the world.
Observations and multiple scales in convection permitting data assimilation
Authors: Dance Sarah L.
Published: March 2022

Convection-permitting (km-scale) data assimilation systems have been used in research and operational numerical weather prediction for more than fifteen years. These systems have been proven to provide improved short-term (0-36 hour) nowcasts, particularly for hazardous weather such as convective storms and fog.  However, there are still many challenges to be addressed in these high-resolution systems.  We will briefly review these broad challenges including multiscaling, spin-up, nonlinearity and model error.

For the main focus of the presentation, we will consider the challenge of providing detailed observation information on appropriate scales in the analysis. We will discuss the treatment of observation and background error covariances and show how they influence the scales in the analysis in idealized studies.  We find that dense observations are most beneficial when they provide a more accurate estimate of the state at smaller scales than the prior estimate. In our idealized experiments, this is achieved when the length-scales of the observation-error correlations are greater than those of the prior estimate and the observations are direct measurements of the state variables. We further test these ideas in an operational system, by assimilating Doppler radar wind observations taking account of their spatially correlated observation errors.  The approach taken gives results for the scales represented in the analysis increments that are consistent with the findings from the idealized studies. In particular, we find that using the correlated observation-error statistics with denser observations produces increments with shorter length-scales than the control. Furthermore, the use of dense Doppler radar wind observations with spatially correlated errors provides improvements in forecast skill, particularly for forecasts of intense convective rainfall, without increasing the wall-clock time for the assimilation.  

Finally, we will discuss the potential of novel observation types such as opportunistic data and those obtained from crowdsourcing to fill some of the gaps in the observation network. We take vehicle-based temperature observations as an example. We discuss the instrument and representation uncertainties associated with vehicle-based observations and present some results from a proof-of  concept trial.  Despite the low precision of the trial data, our results show the potential of vehicle-based observations as a useful source of spatially-dense and temporally-frequent observations for numerical weather prediction.  
A new approach to transfer the discharge recession behavior from gauged to ungauged catchments
Authors: Margreth Michael , Zappa Massimiliano , Wanner Christoph , Hug-Peter Dorothea , Lustenberger Florian , Schlunegger Fritz
Published: March 2022

Many streams in the Swiss Plateau experienced in 2003, 2011, 2015 and 2018 extremely low streamflow conditions. In 2018, on several stream and groundwater gauging stations the lowest values since the start of observations were registered. Climate and hydrological impact models project that by the end of the century in the future summer half such dry periods with similar duration and intensity might occur more frequently. According to the models, extreme dry periods will last even longer as the drought in summer 2018.

To be prepared on that, the public authorities want to know and to get an overview on how streams react in case of such scenarios predicting dryer conditions. A requirement for that is to understand the relevant factors controlling the available storages for low-flow generation and the drainage behavior of small to mesoscale catchments during low flow under recent climate conditions.

Analysis of flow duration curves of over 200 gauged catchments in Swiss Plateau with information of mean annual precipitation and evapotranspiration, geological maps and some topographic properties allowed to identify factors reducing and increasing the low flow q95 percentile and controlling low flow behavior. With analysis of the resulting spatial pattern of specific discharges (l s-1 km-2) of more than 200 additional singular discharge measurements on selected sites during low flow periods, the effects of the relevant factors could be isolated more precisely. The relevant factors essentially consist of:

Lithological construction of bedrock

Infiltration and exfiltration of stream water in and from sediments of river bed

Extend and permeability of quaternary deposits like morains, rubbly deposits, talus or sagging.

Water withdrawal for water supply, irrigation and power plants.

The spatial low flow pattern all over the Swiss Plateau will be presented with maps and the effects of the mentioned factors will be shown on expressive examples.

A new automatic method is developped to calculate so-called master recession curves from the 200 available long-term discharge data series. With the intention to transfer the recession behavior from gauged to ungauged catchments, further analysis are planned in gauged catchments to identify the correlation between the recession curves and the effect of the above mentioned factors.
Assessment of a low-cost Handheld Vector Network Analyzer to Measure the Broadband Complex Permittivity of Soils
Authors: González-Teruel Juan D. , Jones Scott B. , Robinson David A. , Giménez-Gallego Jaime , Zornoza Raúl , Torres-Sánchez Roque
Published: March 2022

Soil moisture is of major relevance in agricultural and environmental monitoring, having a direct impact in crop growth and yield, and playing an important role in soil conservation and landscape management. Several well-known techniques are widely used to determine soil moisture, but dielectric methods are notable for their automation potential and integration in monitoring and irrigation control systems. Measurement of dielectric properties in moist porous substances, such as soils, has been shown to provide reliable estimation of water content. However, frequency domain dielectric spectroscopy seems to reveal information about other useful physicochemical properties of soils. Dielectric spectroscopy measurements are normally restricted to laboratory setups and limited for low budgets due to the high cost, bulk and weight of the equipment. We evaluated the performance of a low-cost, handheld, open-source VNA (Vector Network Analyzer) for the measurement of the complex permittivity of soils in the 1 MHz to 900 MHz frequency range. The tested device was compared with a commercial model using a low-cost, self-manufactured, open-ended coaxial probe to measure the broadband dielectric properties of organic liquids. An empirical method based on known dielectric properties of standard fluids was used to calibrate the probe. The tested low-cost VNA paired with the experimental probe was found to provide accurate and reliable measurements of the broadband complex permittivity from 50 to 700 MHz. The broadband complex permittivity of mineral soils of varied textures was obtained for a range of bulk densities and water contents from dry to water-saturated conditions.
Global warming potentially enhanced both the viral production and decay in a tropical ocean
Authors: Wei Wei , Xie Le , Jiao Nianzhi , Luo Yawei , Zhang Rui
Published: March 2022

Investigating responses of marine viruses to the variation of climate change factors are essential to understanding the effect of global climate change on viral dynamics in the marine microbial food web and virus-mediated biogeochemical cycle. However, there are few studies on the effect of global warming on in situ viral communities in the tropical ocean. Therefore, we performed an experiment to explore the effect of warming on the dynamics of in situ viral community in South China Sea. Interestingly, as a tropical marine viral community, the production and decay rates were still increased by warming, and the balance between production and decay seemed to be broken, resulting in more accumulation of viral particles. As two subpopulations of marine viruses, low-fluorescence viruses may be more sensitive to warming than high-fluorescence viruses. In general, our study indicated for the first time that warming will accelerate the turnover of viruses in surface water of the tropical ocean, which may have positive effects on the efficiency of the BP and MCP.
Assessment of GPM- IMERG precipitation products over Catalonia at different time resolutions
Authors: Peinó Eric , Bech Joan , Udina Mireia
Published: March 2022

Quantitative Precipitation Estimates (QPE) from the Integrated Multisatellite Retrievals for GPM (IMERG) provide crucial information about the spatio-temporal distribution of precipitation in areas with complex orography such as Catalonia (NE Spain). The network of automatic weather stations of the Meteorological Service of Catalonia (XEMA) is used to assess the performance of three IMERG products (Early, Late and Final). The analysis at different time scales, considered three terrain features (valley, flat and ridgetop) and five different categories related to rainfall intensity (light, moderate, intense, very intense, and torrential). During the period 2015-2020, IMERG derived-estimates reproduce well the spatial variability of the precipitation field in the region, although it shows some discrepancies, which become more evident with the reduction of the time scale. Except at sub-daily scales, all three products tend to overestimate by more than 20% records of rain-gauges located in flat areas. The correlation coefficient (r) reflects the improvement of IMERG with increasing time scale with values above 0.7 at annual scale and values just above 0.35 at sub-daily scale. On this scale, rainfall classified as very heavy and torrential showed the poorest results, with significant underestimates higher than 80 %. This weakness of IMERG products is most evident in the IMERG Final, which although providing a reliable reproduction within the interquartile range of the distribution, is not able to detect extremes at different scales. This is related to the inadequate number of Global Precipitation Climatology Centre (GPCC) stations used for calibration. Despite the shortcomings, it can be concluded that IMERG is a valuable tool for the analysis of hydrometeorological processes and useful to complement research in the branches of weather and climate in Catalonia. This research was partly funded by the project “Analysis of Precipitation Processes in the Eastern Ebro Subbasin” (WISE-PreP, RTI2018-098693-B-C32, MINECO/FEDER) and the Water Research Institute (IdRA) of the University of Barcelona.
Constraints on Fracture Distribution in Geothermal Fields Using Seismic Noise Beamforming
Authors: Kennedy Heather , Gilligan Amy , Löer Katrin
Published: March 2022

Faults and fractures are crucial parameters for geothermal systems as they provide secondary permeability allowing fluids to circulate and heat up in the subsurface. In this study, we use an ambient seismic noise technique referred to as the three-component (3C) beamforming to detect and monitor faults and fractures at a geothermal field in Mexico.

Three-component (3C) beamforming extracts the polarizations, azimuths, and phase velocities of coherent waves as a function of frequency, providing a detailed characterisation of the seismic wavefield. In this study, 3C beamforming of ambient seismic noise is used to determine surface wave velocities as a function of depth and propagation direction. Anisotropic velocities are assumed to relate to the presence of faults giving an indication of the maximum depth of permeability, a vital parameter for fluid circulation and heat flow throughout a geothermal field.

We perform 3C beamforming on ambient noise data collected at the Los Humeros Geothermal Field (LHGF) in Mexico. The LHGF is situated in a complicated geological area, being part of a volcanic complex with an active tectonic fault system. Although the LHGF has been exploited for geothermal resources for over three decades, the field has yet to be explored at depths greater than 3 km. Thus, it is currently unknown how deep faults and fractures permeate and the LHGF has yet to be exploited to its full capacity.

3C beamforming was used to determine if the complex surface fracture system permeates deeper than is currently known. Our results show that anisotropy of seismic velocities does not decline significantly with depth, suggesting that faults and fractures, and hence permeability, persist below 3 km. Moreover, estimates of fast and slow directions, with respect to surface wave velocities, indicate the orientation of faults with increasing depth. The North-East and North-West orientation of the fast direction corresponds to the orientation of the Arroyo Grande and Los Humeros faults respectively. Various other orientations of anisotropy align with other major faults within the LHGF at depths permeating to 6 km.
Sitting in the dark- The impact of shading on evapotranspiration in complex urban landscapes 
Authors: Tams Laura , Paton Eva Nora , Kluge Björn
Published: March 2022

Evapotranspiration (ET) is a key parameter in the water exchange of atmosphere, plant and soil and was studied on many different scales. In urban environments, the estimation of evaporation is particularly difficult, as it is effected by complex patterns of shading, which varies on a very small scale as a function of street canyon layout and orientation. Moreover, shading varies not only in space but also in time due to the seasonal orientation and altitude of the sun. Therefore, for a correct ET assessment, the diurnal variations as well as the annual variations of shading must be taken into account. For this purpose, radiation is divided into direct and diffuse radiation; in case of complete shading only the diffuse radiation was used for ET estimation, reducing the direct radiation to zero. The diffuse radiation is further influenced by the amount of visible sky in a street canyon as a function of street widths, which can be derived using the sky view factor.
To reduce the uncertainty of ET estimation in the built environment, a process-based model was developed with an hourly resolution that takes into account the particularly heterogeneous spatial variability of urban surfaces. To assess the impact of shading on ET, six different shadow scenarios as well as two typical urban soil sealing scenarios for a wide and a narrow street canyon were analysed regarding differences and similarities of radiation and resulting actual and potential ET of a street tree as well as soil water dynamics.
The model scenarios showed that ET is highly influenced by shading. Furthermore, shadow scenarios affect actual ET (ETA) differently during the vegetation period: whereas in April the ETA is higher for fully exposed sites, this changes by June when less exposed sites periodically have higher ETA rates. This difference is directly connected to alteration of soil moisture dynamics, for a fully sun exposed site a soil moisture of 10 Vol% is already reached by June. For a shaded site the decrease to 10 Vol% takes two months longer.

In conclusion, the results highlight that it is essential to include the effects of shading in the quantification of vertical water fluxes in urban environments. Moreover, this new model approach will help to identify water shortage periods and critical locations for street trees.
How does anisotropy control rock slope deformation? A discrete element modelling investigation
Authors: Huber Marius L. , Scholtès Luc , Lavé Jérôme
Published: March 2022

Deep-seated failures of rock slopes are partly controlled by structural, lithological and topographical factors. Among structural factors, layering, schistosity and foliation in rock material, which could be described as inherent anisotropy of the material, affect initiation and evolution of deep-seated rock slope deformation, especially in slow moving landslides.

In order to document such an influence of material anisotropy on slope stability, we carry out a parametric study using discrete element modelling (DEM). After a validation exercise for fully isotropic material, where we compare our numerical approach to an analytical slope stability solution, we introduce anisotropy (transverse isotropy) in our DEM model by inserting preferentially oriented and weakened bonds between discrete elements (weakness plane) to simulate two typical transverse isotropic lithologies, claystone and gneiss respectively. Considering these two lithologies, we then explore the influence of the weakness plane’s orientation with respect to the slope angle for both ridge and valley geometries.

We show that certain orientations of the weakness plane relative to the topographic slope favour deep-seated deformation. We also observe significant disparities in failure initiation, failure surface localisation, and mobilized volume depending on the weakness plane orientation. For instance, most unstable slopes occur when the weakness plane rises 10° to 30° less than the hillslope angle. These instabilities are associated with well-localized deformation at depth that when intersecting the surface mimic some of the morphological features (such as counter-slope scarps) that are commonly described along mountain ridges in association with slow-moving and deep-seated rock slope failures.

Our results help explain the appearance or absence of deep-seated failure in mountainous areas and allow to better assess slope failure hazard induced by anisotropic rock strength.
Hotspot identification using high-resolution floating population.
Authors: Hong Je-Woo , Park Jin Han
Published: March 2022

Using high-resolution floating population (50 m) data, heatwave hotspots in a city (Gimhae, Gyeongsangnam-do Province) in Korea are identified. So far many assessment tools (ex., VESTAP for vulnerability and MOTIVE for potential impact in Korea) show only low-resolution results (>1 km, or one result for administrative district). Therefore, most stakeholders for adaptation have difficulty making a decision such as a location decision for a new cooling center and/or shelter for citizens. Simply, we overlap GIS data including a daytime (11:00-16:00) floating population (50 m) based on mobile communication volume, vegetated area and in-land water with 100 m of effective radius, and location of cooling centers with 300 m effective radius. As a result, we find 20 priority locations for heatwave hotspots in a city. This study is supported by “Basic Study on Improving Climate Resilience” (2021-001-03), conducted by the Korea Environment Institute (KEI) upon the request of the Korea Ministry of Environment.
Prototype of a deep learning workflow to map dunes in the Kalahari
Authors: Nowatzki Maike , Bailey Richard , Thomas David
Published: March 2022

Linear dunes show a wide variety of morphometrical patterns; their sizes, spacing, defect density, and orientations differ not only between but also within dunefields (Thomas 1986; Bullard et al. 1995; Hesse 2011; Hugenholtz et al. 2012). The first step towards characterising dune patterning is to accurately and precisely map dunefields, which is challenging, especially when dunefields are too large to be mapped manually. Thus, (semi-)automatic approaches have been brought forward (Telfer et al. 2015; Shumack et al. 2020; Bryant & Baddock 2021). Here, we are presenting the prototype of a deep learning workflow that allows for the automated mapping of large linear dunefields through semantic segmentation.

The algorithm includes the following components: 1) the download of satellite imagery; 2) pre-processing of training and prediction data; 3) training of a Neural Network; and 4) applying the trained Neural Network to classify satellite imagery into dune and non-dune pixels. The workflow is python-based and uses the deep learning API keras as well as a variety of spatial analysis libraries such as earthengine and rasterio.

A case study to apply and test the algorithm’s performance was conducted on Sentinel-2 satellite imagery (10 m spatial resolution) of the southwest Kalahari Desert. The resulting predictions are promising, despite the small amount of data the model was trained on.

The presented prototype is work in progress. Further developments will include parameter optimisation, exploring ways to improve the objectiveness of training data, and the conduction of case studies applying the algorithm to digital elevation rasters.
Effects of climate change on the nitrogen balance of a grassland ecosystem
Authors: Puetz Thomas , Giraud Mona , Groh Jannis , Gerke Horst , Brueggemann Nicolas
Published: March 2022

Grassland is one of the most abundant biomes in the world and important for a variety of ecosystem services. Global climate change is causing a significant increase in temperature and a change in the seasonal distribution of precipitation. The resulting variation in nitrogen turnover is site-specific and long-term experiments are needed to study these changes.
The objective of this study was to investigate changing environmental variables on nitrogen cycling and water use efficiency of an extensively managed grassland site in a low mountain range. Data from the TERENO-SOILCan lysimeter network at the Rollesbroich and Selhausen sites were used. In a "time for space" approach, a total of nine lysimeters were filled at the initial Rollesbroich site and three of these lysimeters were moved to the Selhausen site. Compared to the initial site, the climate in Selhausen is warmer and drier, according to climate predictions.
The results show that climate change may increase the risk of gaseous nitrogen emissions, but that low nitrogen inputs from an extensively used grassland result in only low nitrogen discharges via leachate. In addition, water use efficiency and nitrogen nutrition index will decrease if the crop suffers from water stress, making the grassland more sensitive to drought.
Precise calculations of Nickel content in pyropes
Authors: Ivanov Alexandr
Published: March 2022

The nickel content in pyropes interested researchers due to the possibility to create an algorithm for calculating the temperature boundaries of its joint crystallization with diamonds. Griffin proposed such a calculation algorithm, which was named the diamond-bearing corridor with his name [1]. Determination of nickel content in pyropes on microanalysts is difficult for several reasons. The first reason is the limit of detection of nickel in pyropes, which is very high for the determination of this element on electron microscopes (at least 15 ppm). And then, such an analysis is possible at a quantitative level with a probe beam current of 300nA and an analysis time of 3 minutes. The study of the correlation ratios of nickel with other elements in pyropes allowed us to determine two elements that have a significant correlation with the nickel content in pyropes - these are titanium and manganese and their content in pyropes is acceptable for quantitative determination. On the ion microanalyzer, more than two hundred analyses were performed for pyropes from the kimberlite pipes Botuobinskaya and Nyurbinskaya, the remaining determinations were made from kimberlites tr. Jubilee and tr. Victory with the use of a new technique for the determination of nickel in pyropes in the microanalyzer JXA-8230. In total, 443 definitions of nickel in pyropes were performed at the quantitative level. Such definitions made it possible to calculate the functional dependence of nickel contents on titanium and manganese contents. The STATISTICS program is used for such calculations (Fig. 1).

Fig. 1. Map of level lines (nickel manganese titanium for 443 definitions) with the calculation of functional dependence

The calculation of nickel contents in pyropes makes it possible to fully use the Griffin geothermometer to determine the number of pyrope grains from the diamond-bearing corridor area.

Griffin W.L., Ryan C.G. Trace elements in indicator minerals: Area selection and target evaluation in diamond exploration. J. Geochem. Explor., 1995. Vol. 53., pp, 311-357
The fate of nanoparticles in soils and saturated systems 
Authors: Klitzke Sondra
Published: March 2022

Nanoparticles (NP) enter soils through various pathways. In soils, they undergo different interactions with the liquid and the solid phase. These interactions may govern the chemical and colloidal stability of the NP and hence affect their prospective fate.  Understanding NP fate in saturated systems is of relevance in order to assess any potential risks for the contamination of groundwater, which often serves as a drinking water resource.

In the literature, a fair body of knowledge has been established on the individual impacts of dissolved organic matter (DOM), multivalent ions, and intrinsic particle size on NP colloidal stability. However, little is known about the interactive effects of these parameters as well as the impact of the type of soilborne DOM. In batch studies, using different types of soil solutions, we investigated some of these interactions as well as the effect of DOM characteristics on NP stability.

Further, the potential risk for a breakthrough of both environmentally ‘aged’ NP and synthetically coated NP in an artificial riverbank filtration system was studied. In addition, factors leading to the remobilization of initially immobilized particles were identified.

The presented work provides an overview on how environmentally-induced changes in NP’ surface characteristic control their fate in soils and water resources.