bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of anisotropy in sediment mechanical properties on CH4 bubble growth topology and migration pattern in muddy aquatic sediments
Authors: Painuly Abhishek , Katsman Regina
Published: March 2021

Gas-charged sediments of shallow water bodies are significant sources of atmospheric methane, an important greenhouse gas. Past accounts of gas bubbles developed in shallow aquatic sediments (and in their surrogates) have reported a controversial occurrence of vertical as well as horizontal bubbles topologies. Within the framework of tensile fracturing of muddy sediment produced by the growing bubbles, the vertical orientation of bubbles is well understood, however factors controlling horizontal bubble growth are largely unclear. This study is conducted by employing a mechanical/reaction–transport numerical model, which couples diffusion-led expansion of gas bubble and elastic-fracture mechanical response of sediment to its growth. Muddy sediment is assumed to exhibit a transverse anisotropy in fracture toughness (a property describing an easiness of breaking the inter particle bonds), attributed to partial or full alignment of plate-like clay particles. Our results demonstrate that bubbles growing in isotropic sediment develop a vertically oriented topology and start their ascent once reaching their mature sizes. Under an increasing measure of anisotropy, the bubbles grow horizontally at the initial stages, however at later stages they start evolving in vertical direction as well, under influence of gravity, and eventually initiate their vertical ascent as well. Our results suggest an explanation of apparent conundrum about preferred orientations of bubbles in muddy sediments. Laterally growing bubbles produced in anisotropic sediment are able to coalesce with neighboring ones and form interconnected permeable horizontal gas networks, as observed in some lab experiments. For the first time, our results reveal that anisotropy-led initial lateral bubble growth can also play a crucial role in accumulating gas reserve from long distances around large and small scale seeps and outlets, at continental margins and inland water bodies sediments. Additionally, horizontal bubbles tend to be stationary (in contrast to the vertical bubbles) thus being responsible for high gas storage (or retention) capability of aquatic sediments.
Estimating river water-quality trends under different flow conditions
Authors: Zhang Qian , Webber James , Moyer Douglas , Chanat Jeffrey
Published: March 2021

A number of statistical approaches have been developed to quantify the overall trend in river water quality, but most approaches are not intended for reporting separate trends for different flow conditions. We propose an approach called FN2Q, which is an extension of the flow-normalization (FN) procedure of the well-established WRTDS (“Weighted Regressions on Time, Discharge, and Season”) method. The FN2Q approach provides a daily time series of low-flow and high-flow FN flux estimates that represent the lower and upper half of daily riverflow observations that occurred on each calendar day across the period of record. These daily estimates can be summarized into any time period of interest (e.g., monthly, seasonal, or annual) for quantifying trends. The proposed approach is illustrated with an application to a record of total nitrogen concentration (632 samples) collected between 1985 and 2018 from the South Fork Shenandoah River at Front Royal, Virginia (USA). Results show that the overall FN flux of total nitrogen has declined in the period of 1985–2018, which is mainly attributable to FN flux decline in the low-flow class. Furthermore, the decline in the low-flow class was highly correlated with wastewater effluent loads, indicating that the upgrades of treatment technology at wastewater treatment facilities have likely led to water-quality improvement under low-flow conditions. The high-flow FN flux showed a spike around 2007, which was likely caused by increased delivery of particulate nitrogen associated with sediment transport. The case study demonstrates the utility of the FN2Q approach toward not only characterizing the changes in river water quality but also guiding the direction of additional analysis for capturing the underlying drivers. The FN2Q approach (and the published code) can easily be applied to widely available river monitoring records to quantify water-quality trends under different flow conditions to enhance understanding of river water-quality dynamics. (Journal article: https://doi.org/10.1016/j.scitotenv.2020.143562; R code and data release: https://doi.org/10.5066/P9LBJEY1).
Reduction of cadmium contaminated groundwater pollution by using mineral adsorbents and industrial sorbents   
Authors: Sotoodeh Nia Saeid , Taheri Seyedeh Mohaddeseh , Mahdavi Mazdeh Ali , Wohnlich Stefan
Published: March 2021

    Iron nanoparticles are capable of removing heavy metals due to their significant specific surface relative to their weight. Iron nano powders with an average particle size of 50 nm and very high reactivity are suitable for groundwater purification and industrial wastewater treatment. In fact, the very high ability of iron nanoparticles of zero valences in its reduction and high reactivity makes this material a good choice in achieving the above goals. Due to its small size, after injection, these particles can be spaced and transferred easily. On the other hand, natural zeolites are important aluminosilicates in adsorption processes due to their low cost. In this research activity, a comparison was made between the adsorption percentage of zero iron nanoparticles as an industrial adsorbent with the minerals, calcite, and zeolite. By adding 1 gram of adsorbent powder to a solution of 10 ppm cadmium, decreased cadmium concentrations at different time intervals in three experiments with two replications was measured by an atomic absorption spectrometer. The results showed that 38.4% of cadmium was adsorbed by nanoparticles after 3 hours, which was 8.53% and 5.5%, respectively for the usage of calcite and zeolite mineral adsorbents. This indicates an increase of 29.86 and 32.9% in adsorption of nanoparticle adsorbent compared to calcite and zeolite. To investigate the effect of adsorption percentage in a saturated porous medium, 100 ml of 10 ppm cadmium solution in the presence of 50 g of soil with an average diameter of 1.11 mm saturated with 50 ml of cadmium solution with the same concentration in reaction with 1 g of adsorbent powder was used 22 hours after the start of the experiment, 51.55% of the total cadmium was removed from the environment by soil and industrial adsorbent, and the adsorption percentages for calcite and zeolite in the porous medium were 17.5% and 7.75%, respectively.

Keywords: Cadmium, Zero iron nanoparticles, Calcite, Zeolite.
A 220,000-year-long continuous large earthquake record from the central Dead Sea Fault
Authors: Lu Yin , Wetzler Nadav , Waldmann Nicolas , Agnon Amotz , Biasi Glenn , Marco Shmuel
Published: March 2021

Large earthquakes (magnitude ≥ 7.0) are rare, especially along slow-slipping plate boundaries. Lack of large earthquakes in the instrumental record enlarges uncertainty of the recurrence time; the recurrence of large earthquakes is generally determined by extrapolation according to a magnitude-frequency relation. We enhance the seismological catalog of the Dead Sea Fault Zone by including a 220,000-year-long continuous large earthquake record based on seismites from the Dead Sea center (ICDP Core 5017-1). We constrain seismic shaking intensities via computational fluid dynamics modeling and invert them for earthquake magnitude. Our analysis shows that the recurrence time of large earthquakes follows a power-law distribution, with a mean of ≤ 1400±160 years. This mean recurrence is significantly shorter than the previous estimate of 11,000 years for the past 40,000 years. Our unique record confirms a clustered earthquake recurrence pattern and a group-fault temporal clustering model, and reveals an unexpectedly high seismicity rate on a slow-slipping plate boundary.

Our results suggest that researchers may underestimate the seismic hazard potential of similar slow-slipping faults with irregular rupture. Our study highlights the potential of in situ deformed sediment layers in a subaqueous environment as a strong-motion paleo-seismometer to record long seismic sequences covering multiple recurrence intervals of large earthquakes. Long records are vital for accurate hazard assessment. Our quantitative method of seismic record reconstruction, with paleo-earthquake intensity (ground acceleration) and magnitude estimation, may also prove suitable for similar subaqueous environments along other faults.
The use of environmental data in detailing the hydroregime of a temporary pond
Authors: Campbell Gavin , Hyslop Eric
Published: March 2021

Temporary waters span both terrestrial and aquatic environments, though the terrestrial phase is typically understudied. A key component in the ecology of these water bodies is the length of the hydroperiod. To date, hydroperiod length in temporary waters is determined largely by site visits and camera traps. These methods of determination however, are taxing on resources at fine temporal resolutions (daily). While water level loggers are able to determine hydroperiod length, they are relatively expensive and peak at 50°C, preventing the collection of terrestrial data, particularly within the tropics.

Here we propose an alternative low-cost method for the determination of a temporary pond’s hydroperiod length using anchored HOBO pendant dataloggers of temperature and light intensity. By analysing the environmental data collected at fine temporal resolution across dry and wet seasons - corroborated by daily rainfall collection and frequent site visits - the determination of phase, whether aquatic or terrestrial, using this method was possible. This then extended to the determination of the length of the hydroperiod.

In addition to determining hydroperiod length, this method also provided data on the diurnal temperature dynamics, photoperiod and irradiation intensity of the aquatic and terrestrial phases. Trends in pond drying were also detectable using these data. In the terrestrial phase, the method provided data on soil surface temperatures, which was particularly lacking for the Caribbean. These data are important in understanding environmental stress regimes among aquatic and terrestrial ecosystems, with applications in agriculture, conservation and infrastructure.
The volume conjugate in progressive metamorphism
Authors: Chapman Timothy , Clarke Geoffrey , Milan Luke , Vry Julie
Published: March 2021

Volume changes during metamorphic reactions are key contributors to the physical changes of crystalline rocks. Assessing dehydration or hydration reactions in terms of conjugate V–T pseudosections provides indicators of transient departures in hydrostatic pressure and their impact on observed mineral equilibria. The expansion in volume of major dehydration events such as the breakdown of lawsonite or chlorite delineate zones of fluid overpressure that generate connectivity via fracturing. Net compressional reactions represent sinks for fluid consumption and the focussing of strain. The capacity of metamorphic rocks to generate or consume fluid along portions of the P–T–V path exerts a fundamental control on the distribution of stresses in the crust and the observed mineral assemblages. Coupling a phase equilibria approach to mechanical modelling provides a quantitative framework to assess these changes in fluid pressure that can be compared to prominent case studies in rocks from New Caledonia and New Zealand.
Mapping the global magnetic field in the solar corona through magnetoseismology
Authors: Yang Zihao , Bethge Christian , Tian Hui , Tomczyk Steven , Morton Richard , Del Zanna Giulio , McIntosh Scott , Binay Karak Bidya , Gibson Sarah , Samanta Tanmoy , He Jiansen , Chen Yajie , Wang Linghua , Bai Xianyong
Published: March 2021

Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
Shorter cyclone clusters modulate changes in European wintertime precipitation extremes
Authors: Bevacqua Emanuele , Zappa Giuseppe , Shepherd Theodore G
Published: March 2021

Wintertime extreme precipitation from cyclone clusters, i.e. consecutive cyclones moving across the same region, can lead to flooding and devastating socio-economic impacts in Europe. Previous studies have suggested that the future direction of the changes in these events are uncertain across climate models. By employing an impact-based metric of accumulated precipitation extremes, we show that projections of cyclone clusters are instead broadly robust, i.e. consistent in sign, across models. A novel physical diagnostic shows that accumulated precipitation extremes are projected to grow by only +1.0 %/K on average across Europe, although the mean precipitation per cyclone increases by +4.7 %/K. This results from a decreased number of clustered cyclones, associated with decreased wintertime storminess, the extent of which varies from northern to southern Europe and depends on the future storyline of atmospheric circulation change. Neglecting the changes in the number of clustered cyclones, i.e. assuming that accumulated precipitation extremes would change as the mean precipitation per cyclone, would lead to overestimating the population affected by increased accumulated wintertime precipitation extremes by 130–490 million across Europe.
A comparison of moderate and extreme ERA-5 daily precipitation with two observational data sets
Authors: Rivoire Pauline , Martius Olivia , Naveau Philippe
Published: March 2021

Both mean and extreme precipitation are highly relevant and a probability distribution that models the entire precipitation distribution therefore provides important information. Gamma distributions are often used to model low and moderate precipitation amounts and extreme value theory allows to model the upper tail of the distribution. We apply the Extended Generalized Pareto Distribution (EGPD). Thanks to a transition function, this method overcomes the problem of finding a threshold between upper and lower tails. The transition cumulative distribution function of the EGPD is constrained on the upper tail and lower tail to enable a GPD behavior for both small and large extremes.

EGPD is used here to characterize ERA-5 precipitation. ERA-5 is a new ECMWF climate re-analysis dataset that provides a numerical description of the recent climate by combining a numerical weather model with observations. The data set is global with a spatial resolution of 0.25° and currently covers the period from 1979 to present. ERA-5 precipitation is computed from model forecasts and therefore needs validation against observational datasets. ERA-5 daily precipitation is compared to EOBS precipitation, a gridded dataset spatially interpolated from observations over Europe, and to CMORPH precipitation, a global satellite-based dataset. Simultaneous occurrence of extreme events is assessed with a hit rate. An intensity comparison is conducted with quantiles confidence intervals and a Kullback Leibler divergence test, both derived from the EGPD.

Overall, good agreements but also strong mismatches between ERA-5 and the observational datasets can be found, depending on the feature of interest in precipitation data. This work highlights both. For example, extreme event occurrences between ERA5 and the observational datasets appear to agree. The overlap between 95% confidence intervals on quantiles depends on the season and the probability of occurrence. Over Europe, the best agreement results are generally reached in regions with high station density in EOBS. The global intensity comparison between ERA5 and CMORPH shows a good agreement for moderate quantiles, except for some mountainous regions, but presents a large signal of disagreement in the tropics for large quantiles.
Cooling artificial turf through evaporation from a subsurface water storage unit
Authors: van Huijgevoort Marjolein , Cirkel Gijsbert
Published: March 2021

The increase in population in cities has led to increased pressure on available sport facilities. As a result, natural grass fields are converted to artificial turf, because fields with artificial turf can be used more frequently. Downsides of these artificial turf fields are the increase in surface temperature and the decrease in infiltration of precipitation resulting in faster discharge. Artificial turf can reach very high surface temperatures leading to unplayable fields and health risks, but also contributing to the urban heat island effect. To counteract these high temperatures, irrigation of the fields is needed, which leads to high water demands. In this study, a system to store precipitation below the fields and to enable evaporation to cool the artificial turf was tested. The system consists of water-storing units below the field, a capillary shockpad that enables water transport to the artificial turf and a natural infill from where water can evaporate. To quantify the effects on temperature and evaporation of the system, four test sites were created with natural grass, conventional artificial turf and two versions of the cooled artificial turf (non-infill and standard). All sites were equipped to measure evaporation, surface temperature, net radiation and water levels below the fields. A separate weather station was installed to measure other meteorological variables (e.g. precipitation, air temperature, wind). During the summer of 2020 on days with a maximum air temperature around 30°C, surface temperature reached 37°C at the cooled standard artificial grass, whereas it reached 62.5°C at the conventional artificial turf. The measured surface temperature for the cooled turf was less than 2°C warmer than the surface temperature at the natural grass site (35.3°C). Evaporation from the cooled artificial turf reached maximum values around 4 mm/d during the summer and was about half of the evaporation from natural grass, whereas evaporation from conventional artificial turf was close to zero. These results show that the system is successful in lowering the surface temperature by evaporation. This reduction in surface temperature is important to maintain playable conditions, but also helps to mitigate the heat island effect. In addition, the water storage below the fields reduces peak discharges during high-intensity precipitation. By combining these functions, the cooled artifical turf fields can help cities adapt to climate change.
Application of SIGMA model for landslide forecasting in Darjeeling Himalayas
Authors: Segoni Samuele , Abraham Minu Treesa , Satyam Neelima , Rosi Ascanio , Pradhan Biswajeet
Published: March 2021

SIGMA (Sistema Integrato Gestione Monitoraggio Allerta – integrated system for management, monitoring and alerting) is a landslide forecasting model at regional scale which is operational in Emilia Romagna (Italy) for more than 20 years. It was conceived to be operated with a sparse rain gauge network with coarse (daily) temporal resolution and to account for both shallow landslides (typically triggered by short and intense rainstorms) and deep seated landslides (typically triggered by long and less intense rainfalls). SIGMA model is based on the statistical distribution of cumulative rainfall values (calculated over varying time windows), and rainfall thresholds are defined as the multiples of standard deviation of the same, to identify anomalous rainfalls with the potential of triggering landslides.

In this study, SIGMA model is applied for the first time in a geographical location outside of Italy, i.e. Kalimpong town in India. The SIGMA algorithm is customized using the historical rainfall and landslide data of Kalimpong from 2010 to 2015 and has been validated using the data from 2016 to 2017. The model was validated by building a confusion matrix and calculating statistical skill scores, which were compared with those of the state-of-the-art intensity-duration rainfall thresholds derived for the region.

Results of the comparison clearly show that SIGMA performs much better than the other models in forecasting landslides: all instances of the validation confusion matrix are improved, and all skill scores are higher than I-D thresholds, with an efficiency of 92% and a likelihood ratio of 11.28. We explain this outcome mainly with technical characteristics of the site: when only daily rainfall measurements from a spare gauge network are available, SIGMA outperforms other approaches based on peak measurements, like intensity – duration thresholds, which cannot be captured adequately by daily measurements. SIGMA model thus showed a good potential to be used as a part of the local Landslide Early Warning System (LEWS).
Numerical investigation of inertia gravity-wave activity in the differentially heated rotating annulus: The impact of boundary conditions
Authors: Jochum Felix , Schmid Fabienne , Achatz Ulrich , Rodda Costanza , Harlander Uwe
Published: March 2021

The differentially heated rotating annulus is a classic experiment used for the examination of circulation patterns and waves in the atmosphere. In particular, by choosing an atmosphere-like experimental setup that allows the buoyancy frequency to become larger than the Coriolis parameter, it provides a useful tool to study the generation mechanism of spontaneous gravity wave (GW) emission in jet-front systems. Recently, with the aim to gain better understanding about the conditions for the spontaneous generation of GWs, Rodda et al. (2020) compared experimental data with results from numerical simulations and found differences in the GW signal most likely due to the model's treatment of boundary conditions. The aim of the present study is to improve the consistency between the model and experiment and to investigate the effect of the lateral and upper boundary conditions on GW generation and propagation in an atmosphere-like configuration of the annulus. More precisely, we implement the corresponding lateral and surface heat fluxes, air-temperature variations, as well as evaporation at the upper boundary condition into the numerical model and examine the characteristics of the observed GW signals, which are identified by the horizontal divergence field. Our systematic analysis may serve as a basis for subsequent research on the spontaneous GW generation mechanism, following the overarching objective to develop a parameterization scheme for GWs emitted from jets and front.

 

References:

Rodda, C., S. Hien, U. Achatz, and U. Harlander, 2020: A new atmospheric-like differentially heated rotating annulus configuration to study gravity wave emission from jets and fronts. Exp. Fluids 61, 2. https://doi.org/10.1007/s00348-019-2825-z
Geosciences and the Art of Children's book.
Authors: Silva Daniele Ingredy
Published: March 2021

Given the current environmental crises locally and globally, it became more evident that the level of understanding on the part of most citizens, about the importance of preserving the environment, and even the importance of science and professionals who study the functioning of planet Earth, such as Geosciences and more specifically Geology, is still very precarious and little known in Brazil. It is clear the importance of introducing geosciences since primary education so that with the development of students and the training of these citizens, we can have a better-educated society, not only at the academic level but also with a better environmental awareness directed towards conservation and preservation of the planet. In order to improve this understanding and create children's interest, through a more accessible language about complex processes, a book with artistic illustrations was produced, called “The grand story of a Grain of sand”. The book aimed at children from 6 to 10 years old, describes and illustrates the journey of a grain of sand, from the formation of magma, through the volcanic eruption, rock formation, transport processes, and weathering. The book uses informal language and the association of such processes with everyday situations and experiences commonly lived by children regardless of the socioeconomic situation. The story is fully illustrated and comes with a glossary with more scientific explanations of the terms described in the narrative, to assist parents and teachers who read the book with the children. The illustrations in the book follow in the same direction, both with the literal illustration of the text and with the complementation of the narrative. The character that accompanies the journey narrated by the grain of sand was also created to represent and include the children who read the book in the text. The use of support tools such as the book object of this work has great importance in the dissemination and popularization of geosciences and extension actions such as the one exemplified in this abstract, has to be increasingly worked on by the scientific community so that we can communicate with each other and in a more effective way with the population outside the academic environment.
Eastern Mediterranean Drying: Projected Changes in Dynamics and Thermodynamics and Their Relation to Large-Scale Processes
Authors: Elbaum Eilat , Garfinkel Chaim I. , Adam Ori , Morin Efrat
Published: March 2021

Observations from the past century and projections for the end of this century show a decrease in precipitation over the eastern Mediterranean Sea and surrounding land areas. Changes in precipitation are controlled by both thermodynamic and dynamic processes, but the relative contributions of these processes, in particular on regional scales, is not well understood. Models included in the fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6) exhibit a wide spread in the magnitude of expected drying in the eastern Mediterranean region, as well as in other meteorological variables. By decomposing projected changes in the moisture budget in 48 models into mean dynamic and mean thermodynamic components, we explore the contribution of each of these components to the model spread in regional drying. In the eastern Mediterranean, the dynamic component explains 64% and the thermodynamic component explains 9% of the variance in net precipitation change. We further examine the relation of the regional components to changes in five large-scale mechanisms: tropical vertical stratification, global near-surface temperature, latitude of the eddy-driven jet, stratospheric polar vortex, and arctic amplification. Of these, we find that a decrease in the dynamical contribution in the eastern Mediterranean, causing regional drying, is most strongly related to a northward shift of the eddy-driven jet and a rise in global near-surface temperature.
Communicating uncertainties in spatial predictions of grain micronutrient concentration
Authors: Chagumaira Christopher , Chimungu Joseph G , Gashu Dawd , Nalivata Patson C , Broadley Martin R , Milne Alice E , Lark R Murray
Published: March 2021

The concentration of micronutrients in staple crops varies spatially. Quantitative information about this can help in designing efficient interventions to address micronutrient deficiency. The concentration of a micronutrient in a staple crop can be mapped from limited samples, but the resulting statistical predictions are uncertain. Decision-makers must understand this uncertainty to make robust use of spatial information, but this is a challenge due to the difficulties of communicating quantitative concepts to a general audience. We proposed strategies to communicate uncertain information and present a systematic evaluation and comparison in the form of maps. We proposed to test five methods to communicate the uncertainty about the conditional mean grain concentration of an essential micronutrient, selenium (Se). Evaluation of the communication methods was done through questionnaire by eliciting stakeholder opinions about the usefulness of the methods of communicating uncertainty. We found significant differences in how participants responded to the different methods. In particular, there was a preference for methods based on the probability that concentrations are below or above a nutritionally-significant threshold compared with general measures of uncertainty such as the confidence interval of a prediction.  There was no evidence that methods which used pictographs or calibrated verbal phrases to support the interpretation of probabilities made a different impression than probability alone, as judged from the responses to interpretative questions, although these approaches were ranked most highly when participants were asked to put the methods in order of preference.
How does leaf functional diversity affect the light environment in forest canopies? An in-silico biodiversity experiment
Authors: Plekhanova Elena , Niklaus Pascal A. , Gastellu-Etchegorry Jean-Philippe , Schaepman-Strub Gabriela
Published: March 2021

Global change is affecting biodiversity, with consequences on carbon, water, and energy fluxes between the atmosphere, vegetation, and soil. The interaction of shortwave radiation with vegetation drives basic processes of the biosphere, such as primary productivity or species interactions through light competition.

In our study, we aim to understand the effects of biodiversity on canopy light absorption. We focus on the diversity of three key functional traits that influence the light-canopy interaction: leaf area index, leaf angle distribution and leaf optical properties. Our study is based on the in-silico combination of process-based modelling of radiation (3D radiative transfer model DART) with the well-established design of biodiversity experiments. We used this novel method to study the effects of leaf functional diversity on a light proxy for productivity (the fraction of absorbed photosynthetically active radiation (FAPAR)) and net radiation (shortwave albedo). We found that diverse canopies had lower albedo and higher FAPAR than the average of the corresponding monoculture values. In mixtures, FAPAR was unequally re-distributed between trees with distinct leaf traits and the net biodiversity effect on absorptance was greater when combining plant functional types with more distinct traits. Our results support the mechanistic understanding of overyielding effects in functionally diverse canopies and may partially explain some of the growth-promoting mechanisms in biodiversity-ecosystem functioning experiments. They can further help to account for biodiversity effects in dynamic vegetation and climate models.

We would like to present this study in the BG3.22 session, because it 1) contributes to the understanding of fundamental ecosystem functions related to light interaction 2) describes a novel in-silico combination of process-based modelling of radiation with the well-established design of biodiversity experiments.
The Mediterranean viticulture in response to global climate change drivers, the lesson of the past
Authors: Guiot Joel , Bernigaud Nicolas , Bondeau Alberte , Bouby Laurent
Published: March 2021

Using a statistical emulator of a coupled climate-ecosystem model, this paper proposes a method to link the vine potential productivity and the viticulture extension in the Mediterranean area to global climate drivers, such as orbital parameters, solar and volcan activities and greenhouse gas concentrations. The emulator was calibrated on several tens of simulations of earth system models in various situations from the PMIP3 past (Last Glacial Maximum, Mid-Holocene, last millennium) and the CMIP5 future simulation up to 2100 under several RCP scenarios. The key climate variables produced by these simulations were introduced in an ecosystem model (BIOME4), so the ecosystem variables can be directly estimated from the global drivers. The large variation of situations used for calibration produces a robust emulator able to extrapolate to a large range of past and future climate states. Applied to the Mediterranean and European area, the emulator has been validated on several key periods of the past where the climate is known to have much changed. Finally, it was used to simulate the viticulture extension not only for these key past periods but also for different scenarios of the future, related to a global warming of 1.5°C, 2°C, 3°C and 5°C. Even if human groups are mainly responsible of viticulture extension, climate is a driver in the way that bad climate conditions may be a limit to extension or even a driver of regression.

The main findings are: (i) If the climate change projected for the future can be attributed to greenhouse gases increase as expected, the variations of the last millennia in the Mediterranean Basin can be attributed to the volcanic activity, the solar activity effect being negligeable; (ii) the effects of these volcanic forcing on the climate are not necessarily uniform across the basin and had a large impact on the viticulture as they were sufficiently important to be responsible of extension of viticulture on the whole Gaul during the Roman Climate Optimum; (iii) for the future, it is projected large difficulties for viticulture in Spain and North Africa. They will be particular important for a global warming of +3°C and more; (iv) there is little hope that an intense volcanic activity could slow down this regression.
Providing future UK heavy precipitation guidance for water management stakeholders using a convection-permitting climate model ensemble and a spatial extreme statistical model
Authors: Chan Steven , Kendon Elizabeth , Youngman Benjamin , Fosser Giorgia , Short Christopher , Fowler Hayley , Tucker Simon , Dale Murray
Published: March 2021

The UK Climate Projections (UKCP) provide the latest information on future climate change expected in the UK. The latest UKCP products include the first UK national climate scenarios at a resolution consistent with weather forecasting. In particular, they include projections from a 12-member 2.2km convection permitting climate model (CPM) ensemble, called UKCP Local (2.2km), released by the UK Met Office in September 2019. A key added value of CPMs is their improved representation of precipitation extremes, and as such the UKCP Local ensemble is particularly useful for water management stakeholders (water utilities and flood risk management professionals) for future adaptation in waste water and flood risk management. A key metric of interest is future increases (“uplifts”) of precipitation return levels. However, diagnosing precipitation return levels for such high-resolution model simulations is difficult due to their spatial-temporal variability and correlation. Here, we adapt an Exeter University-developed spatial extreme statistical model which incorporates the spatial-temporal variability and correlation of precipitation extreme, and apply it to daily and hourly precipitation data from the UKCP Local Ensemble for both the present-day and future RCP8.5 simulations. This allows us to provide robust estimates of uplifts for high return levels across all of the UK for months and seasons of interest.
Leveraging non-traditional evidence for glacial isostatic adjustment to constrain past ice sheets
Authors: Pico Tamara
Published: March 2021

Although understanding the response of ice sheets to a changing climate is a pressing issue of this century, our current knowledge of past ice-sheet changes remains limited by data sparsity. I explore approaches that leverage non-traditional datasets to constrain past ice sheet and sea-level change over the last glacial cycle. For example, I consider the potential to use past landscapes to infer crustal deformation induced by ice sheet loading. Over the ice-age, glacial isostatic adjustment produces rates of uplift comparable to some of the fastest tectonic uplift rates (~10 mm/yr) in regions hundreds of kilometers away from the maximum ice sheet extent. Additionally, I show it is possible to gain insight into longer-term continental scale ice sheet deglacial histories using small-scale ice stream dynamics. Using records for a rapid retreat of the Amundsen Gulf Ice Stream, located on the northwest Laurentide Ice Sheet, along with observations of the Bering Strait flooding as sea-level indicators, I fingerprint the timing and location of North American saddle deglaciation.
A robust seismic structure along the North Anatolian Fault beneath the Central Marmara Sea, and its implication for seismogenesis
Authors: Yamamoto Yojiro , Kalafat Dogan , Pinar Ali , Takahashi Narumi , Polat Remzi , Kaneda Yoshiyuki , Ozener Haluk
Published: March 2021

The offshore part of the North Anatolian Fault (NAF) beneath the Marmara Sea is a well-known seismic gap for future M > 7 earthquakes in the sense that more than 250 years have passed since the last major earthquake in the Central Marmara region. Here, an assessment on the location of possible asperities to host the expected next large earthquake is done based on the heterogeneities on the seismic velocity structure. Using long-term ocean bottom seismograph (OBS) observation data, seismic tomography and precise hypocenter estimations have been conducted. As a result, about five times more microearthquakes than the events in a land-based catalog has been detected. A comparison with previously published results suggests that the seismicity pattern has not changed during the three years period between Sep. 2014 and Jun. 2017. The obtained velocity model shows strong lateral contrast whose changing points locate at 28.10°E and 28.50°E. The western corner of the area (28.10°E) corresponds to a segmentation boundary where the dip angle of the NAF segments changed. The high velocity zones in the tomographic images are characterized by low seismicity eastward from the segment boundary at 28.10°E. Eastern 28.50°E, the high velocity zone becomes thicker in the depth direction. These zones are interpreted as asperities to be ruptured by the next large earthquake which are possibly accumulating strain since the mainshock rupture associated with the May 1766 Ms7.3 earthquake.
General considerations for modeling water table dynamics in peatlands
Authors: Cobb Alex , Harvey Charles
Published: March 2021

A basic and universal characteristic of peatlands is that the water table frequently rises near the surface of the soil profile. Surface peat is naturally loose and open-structured, and often has microtopographic features; the water table frequently rises above the level of local depressions. Therefore, water table fluctuations in peatlands cause rapid changes in the permeability and effective porosity of the medium through which flow occurs. We use a simple model based on Boussinesq's equation to explore the challenges that arise from these basic and universal physical aspects of peatland hydrology. We show that simulation of water table fluctuations in peatlands requires precipitation data with a high temporal resolution, and careful attention to the time derivative for accuracy of the mean water tables and correct water balance for two reasons. First, large vertical gradients in specific yield can result in large mass balance errors analogous to errors from naive discretization of the Richards equation; a change of variables from water table elevation to water storage can eliminate these errors and also speed up calculations by allowing larger time steps. Second, large vertical gradients in permeability near the peat surface cause a strongly nonlinear response to precipitation, so that time-averaged precipitation data or neglect of diurnal cycles of evapotranspiration results in erroneously high water levels, and careful time stepping is required around rain storms.  Consideration of these features of peatland hydrology results in efficient hydrologic models that can be used to predict spatial and temporal patterns in greenhouse gas uptake and emissions in peatlands.
Changes in Yangtze Precipitation Extremes and the association with thermodynamic, dynamic, and local drivers  
Authors: Li Xin
Published: March 2021

Spatioteporal variability of precipitation extremes is increasingly the focus of attention in both the climate and hydrology communites, especailly in the context of global climate change. Indicated by the Clausius-Clapeyron equation under the constant relative humudity assumption, it is expected, from the thermodynamic perspective, that extreme precipitation would increase as globe warms. However, when it comes to the regional response of precipitation to global warming, the resutls could be highly uncertain due to the influences of dynamic factors such as large-scale circlation patterns and local effects. Here, we investigate trends in a set of extreme precipitation indices (EPIs) over the Yangtze River Basin (YRB) during the period of 1960-2019. Also, we explore the possible associations between spatiotemporal variability of the EPIs and global warming, ENSO, and local effects. Our resutls show marked rising trends in frequency and intensity of Yangtze precipitation extremes. Global warming tends to enhance the frequency and intensity of preciptation extremes over the YRB. The La Niña phase of ENSO could lead to an increase of precipitation extremes in the current year, but a decrease of precipitation extremes in the coming year. Local warming mainly exerts a reducing effect on precipitation extremes, which is likely associated with the significant decrease of relative humidity in the YRB. Our findings highlight the need for a systematic approach to investigate changes in precipitation extremes over the YRB.
Empirical inner boundary conditions and rotation rates for solar wind models
Authors: Morgan Huw
Published: March 2021

To date, the inner boundary conditions for solar wind models are either directly or indirectly based on magnetic field extrapolation models of the photosphere. Furthermore, between the photosphere and Earth, there are no other direct empirical constraints on models. New breakthroughs in coronal rotation tomography, applied to coronagraph observations, allow maps of the coronal electron density to be made in the heliocentric height range 4-12 solar radii (Rs). We show that these maps (i) give a new empirical boundary condition for solar wind structure at a height where the coronal magnetic field has become radial, thus avoiding the need to model the complex inner coronal magnetic field, and (ii) give accurate rotation rates for the corona, of crucial importance to the accuracy of solar wind models and forecasts.
Self-validating deep learning of continental hydrology through satellite gravimetry and altimetry
Authors: Irrgang Christopher , Saynisch-Wagner Jan , Dill Robert , Boergens Eva , Thomas Maik
Published: March 2021

Space-borne observations of terrestrial water storage (TWS) are an essential ingredient for understanding the Earth's global water cycle, its susceptibility to climate change, and for risk assessments of ecosystems, agriculture, and water management. However, the complex distribution of water masses in rivers, lakes, or groundwater basins remains elusive in coarse-resolution gravimetry observations. We combine machine learning, numerical modeling, and satellite altimetry to build and train a downscaling neural network that recovers simulated TWS from synthetic space-borne gravity observations. The neural network is designed to adapt and validate its training progress by considering independent satellite altimetry records. We show that the neural network can accurately derive TWS anomalies in 2019 after being trained over the years 2003 to 2018. Specifically for validated regions in the Amazonas, we highlight that the neural network can outperform the numerical hydrology model used in the network training.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL089258
Seasonal and local time variations of auroral electrojet: CHAMP observation
Authors: Zhong Yunfang , Wang Hui , Zheng Zhichao , He Yangfan , Sun Luyuan , Gao Jie , Zhang Kedeng
Published: March 2021

The auroral electrojet is an important element of the polar current system and an essential subject in space weather research. Based on the scalar magnetic field data from CHAMP satellite, we studied the influences of solar illumination and the dipole tilt angle (DTA) on the auroral electrojet as well as its seasonal variations. Furthermore, the auroral electrojet measured by satellite was compared with the auroral electrojet indices derived from the ground stations. It is shown that on the dayside, the auroral electrojet is more intense at a smaller solar zenith angle (SZA), whereas it’s more intense on the nightside when the SZA is larger. The daytime current is mainly controlled by the solar illumination, while the nighttime current is affected by the substorm. Compared with the solar illumination, the dipole tilt angle plays a minor role. The auroral electrojet shows an obvious annual and semiannual variation. The eastward electrojet and the dayside westward electrojet are more intense in summer than in winter, while the nightside westward electrojet is more intense in winter than in summer. The daytime westward electrojet is more intense at solstices, whereas the nighttime westward electrojet is more intense at equinoxes. The westward electrojet shows a good correlation with AL and SML indices. The eastward electrojet correlates well with the SMU index, but shows obvious difference with the AU index. The discrepancy can be attributed to the fact that the peak eastward electrojet is located outside the detection range of the auroral electrojet stations.