bluuebunny/crossref_metadata_2025 huggingface dataset:
Mesospheric ionization rates due to Medium Energy Electron Precipitation – an overview
Authors: Nesse Tyssøy Hilde , Sinnhuber Miriam , Asikainen Timo , van de Kamp Max , Pettit Joshua , Randall Cora , Smith-Johnsen Christine , Verronen Pekka T. , Wissing Jan Maik , Yakovchuk Olesya
Published: March 2020

Quantifying the ionization rates due to medium energy electron (MEE) precipitation into the mesosphere has long been an outstanding question. It is the key to understand the total effect of particle precipitation on the atmosphere. The first MEE ionization rate was provided by the Atmospheric Ionization Module Osnabrück (AIMOS) in 2009. It applies electron measurements by the 0o electron detector on the MEPED instrument on board the NOAA/POES satellites together with geomagnetic indices. Since then several other efforts to estimate the MEE precipitation and associated ionization rates has been made taking account e.g. of cross contamination by low-energy protons; Full Range Energy Electron Spectra (FRES) and ISSI-19. Recently, a parameterization based on the same electron data, scaled by the geomagnetic index Ap, has been included in the solar-driven particle forcing in the recommendation for Coupled Model Intercomparison Project 6 (CMIP6). Another parameterization aiming to resolve substorm activity applies the SML index, AISstorm. Further, three different methods to construct the total bounce loss cone fluxes based on both MEPED detectors has been suggested by the University of Colorado, University of Oulo, and the University of Bergen. In total, the space physics community offers a wide range of mesospheric ionization rates to be used in studies of the subsequent chemical-dynamical impact of the atmosphere, which are all based on the MEPED electron measurement.

Here we present a review of eight different estimates of energetic electron fluxes and the ionization rates during an event in April 2010. The objective of this comparison is to understand the potential uncertainty related to the MEE energy input in order to assess its subsequent impact on the atmosphere. We find that although the different parameterizations agree well in terms of the temporal variability, they differ by orders of magnitude in ionization strength both during geomagnetic quiet and disturbed periods and show some inconsistency in terms of latitudinal coverage.
Oak trees are elemental carbon sinks in urban ecosystems: patterns and drivers
Authors: Ponette-Gonzalez Alexandra , Rindy Jenna , Barrett Tate , Chen Dongmei , Elderbrock Evan , Ko Yekang , Lee Jun-Hak , Sheesley Rebecca , Weathers Kathleen
Published: March 2020

Cities represent a significant source of atmospheric elemental carbon (EC), a minor constituent of particulate matter (PM) but a major climate-forcing agent and air pollutant. Urban trees scavenge PM and regulate material fluxes to the ground. As such, urban trees represent potentially important sinks—not only for PM but also for EC—in urban landscapes. Here we assess the magnitude and spatiotemporal drivers of EC removal by trees in urban atmospheres. We quantified foliar EC accumulation by, as well as throughfall EC flux under, the canopy of two oak species (Quercus stellata: post oak; Quercus virginiana: live oak), which are widespread across the southern United States. Sampling was conducted from March 2017 to March 2018 across the City of Denton, a city at the northern edge of the Dallas-Forth Worth metropolitan area in Texas. Over the year-long study period, we found that post oak tree canopies accumulated two times more EC (0.53 mg EC m-2 leaf d-1) than live oak trees (0.22 mg EC m-2 leaf d-1), with 95% of EC depositing to leaf surfaces as opposed to leaf waxes. Throughfall EC fluxes were also greater under post oak (0.15 mg EC m-2 d-1) compared to live oak (0.12 mg EC m-2 d-1) canopies, but these differences between post oak and live oak were far less pronounced than for foliar EC accumulation. These results suggest that considerable amounts of dry-deposited EC are retained in post oak canopies, reducing species differences in throughfall EC fluxes. Our findings also revealed strong, albeit, contrasting seasonal patterns for foliar EC accumulation and throughfall EC fluxes. For both tree species, EC accumulation on canopy surfaces increased, whereas throughfall EC fluxes decreased from spring to fall, providing additional evidence that EC retention on canopy surfaces results in decreased EC fluxes to the ground. In summary, our findings show that urban oak trees scavenge considerable amounts of EC from the atmosphere and that the magnitude of accumulation and delivery to soil vary by species and season. This research highlights the potential for urban trees and forests to contribute to climate and air quality mitigation.
Neogene and active brittle deformation on Amorgos Island (Greece)
Authors: Behrmann Jan , Schneider Jakob , Zitzow Benjamin
Published: March 2020

Amorgos is the south-eastern outpost of the Cyclades Islands in the Aegean Sea, which forms part of the Neogene-Quaternary zone of crustal and lithospheric N-S upper plate extension northward of the Hellenic subduction zone and deep sea trench. Apart from subduction-related earthquakes further south, the southern Aegean is affected by frequent earthquakes sourced in the upper plate. The twin earthquakes of 9 July 1956, followed by a strong tsunami, were the strongest events of this kind in the past Century. Hypocenters are related to a NE-SW oriented normal fault bounding the Amorgos-Santorini Graben System. There are questions in the literature regarding the seismic source and fault plane solutions, especially the contribution of a transcurrent faulting component.

We have analyzed the kinematics of brittle faults exposed on Amorgos Island itself that could be related to Neogene and active extensional and/or transcurrent deformation. Seismic slip often occurs on previously existing faults. Thus, their orientations and kinematics may help shed light on the structure of seismic sources at depth. We present evidence for a complex history of faulting. Early normal detachment faults and shear zones overprint older (rare) reverse faults, and are themselves overprinted by several sets of dominantly dextral NE and SE trending strike slip faults. Youngest is a conjugate set of NE trending high-angle normal faults. These are especially frequent along the SE coast of the island, suggesting a clear spatial relationship with the 1956 rupture. They can be fitted to a moment tensor solution similar to the published solutions for the 1956 Amorgos earthquake. The kinematic solution for the population of early normal faults suggests that the whole of Amorgos Island may have experienced a 15° NNW tilt during later extension, which lets us suspect that the island could be a tilted block of a much larger fault system. Regarding long-term late Neogene to Quaternary kinematics, dextrally transtensive fault slip is required to fit the regional pattern of extensional deformation in the Aegean, and this is reflected by small-scale brittle faulting on Amorgos.
Revisiting Carbon Storage in Northern Peatlands: Ground-Based Estimates and Top-Down Constraints from Holocene Global Carbon Budget Reconstructions
Authors: Yu Zicheng , Joos Fortunat , Bauska Thomas , Stocker Benjamin , Fischer Hubertus , Loisel Julie , Brovkin Victor , Hugelius Gustaf , Nehrbass-Ahles Christoph , Kleinen Thomas , Schmitt3 Jochen
Published: March 2020

Northern peatlands store large amounts of carbon (C) and have played an important role in the global carbon cycle since the Last Glacial Maximum. Most northern peatlands have established since the end of the deglaciation and accumulated C over the Holocene, leading to a total present-day stock of 500 ± 100 GtC. This is a consolidated estimate, emerging from a diversity of methods using observational data. Recently, Nichols and Peteet (2019 Nature Geoscience 12: 917-921) presented an estimate of the northern peat C stock of 1055 GtC—exceeding previous estimates by a factor of two. Here, we will review various approaches and estimates of northern peatlands C storage in the literature and consider peat C storage in the context of the Holocene global C budget. We argue that the estimate by Nichols and Peteet is an overestimate, caused by systematic bias introduced by their inclusion of data that are representative for the major peatland regions and of records that lack direct measurements of C density. In particular, some “peatland” sites and data that were included in their synthesis were likely from lacustrine sediments prior to the onset of peat deposits. Furthermore, we argue that their estimate cannot be reconciled within the constraints offered by ice-core and marine records of stable C isotopes and estimated contributions from other processes that affected the terrestrial C storage during the Holocene.
Lifetime of Channel Electron Multipliers dedicated to Plasma Instruments for Solar Orbiter and JUICE ESA missions
Authors: Fedorov Andrey , Baruah Rituparna , Rubiella Romeo Jean
Published: March 2020

Both Solar Orbiter and Jupiter Icy moon Explorer (JUICE) are long-life ESA missions, which should work in extremely difficult space environment. A very high thermal load up to 13 Solar constants will affect Solar Orbiter, and JUICE will experience a high penetration radiation influence in the Jupiter magnetosphere. The plasma packages of these missions, dedicated mostly for detection of low energy (between 1eV and 50 keV) ions and electrons shall accept a very high dynamic range of the incident charged particle flow. All these circumstances motivate us to use the Channel Electron
Multiplier (CEM) as detectors in both missions. CEMs are a conventional low energy charged particle and X-ray detectors that have been used fore many early space missions. Later, they were forced out by Micro-Channel Plates (MCP), which
allow to provide an image of the particle distribution. But for such challenge missions as Solar Orbiter and JUICE we have to come back to CEMs because they 1) less sensible to the penetrating radiation 2) have much wide dynamical
range, 3) have much longer lifetime than MCPs. 
The detector lifetime is, actually, the maximum particles number accumulated by detector until its efficiency becomes too low. And this detector feature is critical for Solar Orbiter and JUICE missions.
To check the lifetime of CEMs, for different thermal conditions also, we have made a dedicated experimental setup. We irradiated several CEM samples by a strong electron flux, continuously measuring the CEM gain and keeping 80°C on
the sample. The final total number of events, detected by each CEM was equivalent to two Solar Orbiter nominal mission duration.
The detailed analysis of the experimental data show that the visible degradation of CEMs gain is a function of the vacuum level in the vicinity of the CEM and its outgassing efficiency. If we normalize the CEM gain to the vacuum, expected in the flight, we will see that the pure, completely outgassed CEM can accumulate ten Coulombs of charge without any gain degradation. But in the beginning of the flight, we have to expect very fast gain degradation because of the CEM self-cleaning.
Elastic Impact Consequences for High-Frequency Earthquake Ground Motions
Authors: Tsai Victor , Hirth Greg
Published: March 2020

A fundamental question of earthquake science is what produces damaging high-frequency ground motion, with the classic Brune-Haskell model postulating that abrupt initiation of fault slip causes it. However, even when amended with heterogeneous rupture, frictional slip models fail to explain observations of different sized repeating earthquakes, and have challenges explaining high-frequency radiation patterns as well as the dependence of stress drops on fault maturity and depth. We propose an additional cause for high-frequency earthquake spectra from elastic collisions of structures within a rupturing fault zone. The collision spectrum is set by an impact contact time that is proportional to the size of colliding structures, so that spectra depend on fundamentally different physical parameters compared with slip models. When added to standard frictional models, the collision model can reconcile the discrepant observations, since the size, shape and orientation of structures vary between different fault zones but remain constant within a given fault segment. High-frequency earthquake ground motions and damage may therefore be an outgrowth of fault-zone structure rather than sudden initiation of slip.
Geochronologic constraints on the Shuram excursion in Oman
Authors: Cantine Marjorie , Rooney Alan , Linneman Ulf , Hofmann Mandy , Albert Richard , Gomez Perez Irene , Baloushi Badar , Gerdes Axel , Bergmann Kristin
Published: March 2020

            The rise of animals occurred during an interval of Earth history that witnessed highly dynamic atmosphere-ocean redox conditions; regional, transient glaciations; extraordinarily low magnetic field intensities potentially related to inner core formation; and perturbations to the global carbon cycle of a size not seen before or since. The largest of these, the Shuram carbon isotope excursion, has been invoked as a driving mechanism for, or consequence of, various biological and geological events during the Ediacaran Period. However, there are a number of major controversies regarding the Shuram, including its timing. Without age constraints on its onset or duration, it is impossible to confidently connect the Shuram Event with any biological or geological upheavals.

Here, we apply multiple methods, including Re-Os on black shales and U-Pb LA-ICP-MS dating on carbonates, to well-preserved Ediacaran stratigraphy from Oman, deriving new age controls in previously undated parts of the stratigraphy. Our new data show that paired Re-Os shale and U-Pb carbonate analyses constrain the onset and duration of the Shuram excursion in Oman. The results—which are consistent with recent age constraints on Shuram-bearing stratigraphy from Northwest Canada (Rooney et al. 2019, Goldschmidt)—demonstrate the utility of leveraging multiple geochronological techniques within a single basin to constrain deposition in deep to shallow depositional environments. The results also provide key absolute age constraints on the onset of the Shuram excursion in the stratigraphy where it was first defined, critical for testing global correlation schemes, constructing a temporal framework for the Ediacaran period, and identifying causal mechanisms during this interval of geobiological and geodynamic dynamism.

 
High Resolution Attenuation Images From Active Seismic Data: The Case Study of Solfatara Volcano (Southern Italy)
Authors: Russo Guido , Serlenga Vincenzo , De Landro Grazia , Amoroso Ortensia , Festa Gaetano , Zollo Aldo
Published: March 2020

The anelastic attenuation of rocks strongly depends on the contained fluid physical state and saturation. Furthermore, it is more sensitive than elastic parameters to changes in the physical state of materials. In a geologically complex  volcanic context, where fluids play a very important role, anelastic imaging of the subsoil is therefore a very powerful tool for a better understanding of its dynamics.

In this study we present a robust workflow aimed at retrieve accurate 1-D and 3-D anelastic models from the processing of active seismic data, in terms of lateral and depth variations of P-wave quality factors QP. This methodology has been applied to data collected during a high resolution active seismic experiment in a very small-scale volcanic volume, the Solfatara crater, within Campi Flegri caldera, Southern Italy. The presented methodology is developed in three distinct steps: 1) the active seismic data have been properly processed and analyzed for measuring the t* attenuation parameter for all possible source-receivers couples. First, the source contribution has been removed by cross-correlating the recorded signal with the sweep function of the Vibroseis, which was the adopted active seismic source. Then, the spectral decay method has been applied in order to compute the t* values. 2) A reference 1-D attenuation model has been retrieved by means of a grid search procedure aiming at finding the 1-D Qp structure that minimizes the residual between the average observed t* and the theoretical t* distributions. The obtained starting reference model allowed to build a preliminary map of t* residuals through which the retrieved t* dataset has been validated. 3) The 15,296 t* measurements have been inverted by means of a linearized, perturbative approach, in a 160 x 160 x 45 m3 tomographic grid.

The retrieved 3-D attenuation model describes the first 30 m depths of Solfatara volcano as composed of very high attenuating materials, with Qp values ranging between 5 and 40. The very low Qp values, correlated with low Vp values retrieved by a previous tomographic work carried out in the area, indicate the low consolidation degree of very superficial volcanic materials of Solfatara volcano. Finally, in the NE part of the crater, lower attenuating bodies have been imaged: it is a further hint for characterizing this area of the volcano as the shallow release of the CO2 plume through the main fumaroles of the crater.
United in Variety: The EarthServer Datacube Federation
Authors: Baumann Peter
Published: March 2020

Datacubes form an accepted cornerstone for analysis (and visualization) ready spatio-temporal data offerings. Beyond the multi-dimensional data structure, the paradigm also suggests rich services, abstracting away from the untractable zillions of files and products - actionable datacubes as established by Array Databases enable users to ask "any query, any time" without programming. The principle of location-transparent federations establishes a single, coherent information space.

The EarthServer federation is a large, growing data center network offering Petabytes of a critical variety, such as radar and optical satellite data, atmospheric data, elevation data, and thematic cubes like global sea ice. Around CODE-DE and DIASs an ecosystem of data has been established that is available to users as a single pool, in particular for efficient distributed data fusion irrespective of data location.

In our talk we present technology, services, and governance of this unique intercontinental line-up of data centers. A live demo will show dist
ributed datacube fusion.

 
Stochastic Spatiotemporal Patterns of Metapopulation Occupancy in Dynamic Wetlandscapes
Authors: Bertassello Leonardo Enrico , Jawtiz James , Bertuzzo Enrico , Botter Gianluca , Hoverman Jason , Rao Suresh
Published: March 2020

Dynamic internal feedbacks and stochastic external shocks drive the spatial organization and heterogeneity of patchy habitats, and thus the temporal variability of patch suitability and accessibility. Such spatiotemporal shifts impact species dispersal among patches and metapopulation persistence. Here, we extended the widely recognized concepts of patch-occupancy and metapopulation capacity from static to dynamic patchy habitats, with isolated wetlands embedded in uplands as the case study. We present a new metapopulation modeling approach by linking a hydrological model for wetland variability with a dynamic stochastic patch-occupancy model. In two case study wetlandscapes, we evaluate (1) spatiotemporal dynamics of wetland hydrologic regimes, and patch suitability and connectivity driven by stochastic hydroclimatic forcing, and (2) spatiotemporal patterns of patch occupancy and metapopulation dispersal dynamics. Our modeling results reveal the importance of specific connected patches that serve as persistent hubs and form the backbone of dispersal corridors to support species dispersal in fragmented dynamic landscapes. Our analyses reveal that the interplay between stochastic hydroclimatic forcing and patchy habitat structure could drive species to extinction when specific thresholds are crossed.
Recurrence of extreme temperatures in Switzerland from 1965 to 2018
Authors: Gubler Stefanie , Fukutome Sophie , Frei Christoph
Published: March 2020

Extreme high temperatures have a strong impact on human well-being. In Switzerland, for instance, mortality has been shown to increase during strong heat waves (e.g., Ragettli et al., 2017) such as those that occurred in 2003, 2015, or 2018. Knowledge on the recurrence of such heat waves is therefore important, but conventional analysis of observational series is challenged by their rare occurrence (limited sampling), long-term trends, and strong seasonality (non-stationarity). This work presents a methodology, to derive reliable recurrence estimates of extreme maximum and minimum temperature events, taking account of gradual trends and seasonality in the data.

Temperature in Switzerland undergoes pronounced seasonal fluctuations, both in mean value and variance. In addition, a significant warming occurred over the last decades. To derive robust estimates on the rarity of a given extreme temperature event, it is important that these non-stationarities are formally modelled. Our modelling assumes that observed daily temperatures at stations are a superposition of a gradual, non-linear trend and residuals from a skewed T-distribution. The parameters of that distribution are assumed to vary over the year as second order harmonic functions. The model parameters are estimated using maximum likelihood. Thanks to this modelling, the existing daily temperature data can be transformed into a standard normal distribution, and the probability of an event can thus be assessed with respect to the climate at the time of measurement (year, calendar day).

With this methodology in hand, we analyze heat waves of the past, focusing on extreme temperatures at the beginning of summer when mortality risks are higher (Ragettli et al, 2017). We show how the risk of extreme heat has changed in the past, and how very rare events have become much more frequent in the present climate.

 

Ragettli, M., Vicedo-Cabrero, A. M., Schindler, C., and M. Röösli (2017): Exploring the association between heat and mortality in Switzerland between 1995 and 2013, Environmental Research, 158, 703-709, https://doi.org/10.1016/j.envres.2017.07.021.
The first Women's Networking Events at the IUGG General Assembly (2019) and the IAGA EM Induction Workshop (2018)
Authors: Schnepf Neesha
Published: March 2020

This presentation reflects on the first Women’s Networking Events at the International Union of Geodesy and Geophysics’s General Assembly (2019) and the International Association of Geomagnetism and Aeronomy’s Electromagnetic Induction Workshop (2018). These meetings are historically extremely male-dominated events and the Women’s Networking Events provided a first-of-its-kind space for women to network with one another, creating solidarity and community for participants to rely on through the meeting and beyond. Both events were well attended, especially by early career women, with ~40 participants in each case. Women’s Networking Events have been present at the American Geophysical Union’s Fall Meeting for many years now, and these inaugural IUGG/IAGA Women’s Networking Events will hopefully lead to many more (indeed, the local organizing committee for the 2020 Electromagnetic Induction Workshop has already included the Women’s Networking Event in the workshop schedule and budget). This presentation will discuss the motivation behind the events, lessons learned, and ideas for the future.
The Impact of Predator-Prey Processes in Bulk Microphysics Schemes on Simulated Aerosol-Cloud Interaction
Authors: Grell Evelyn , Bao Jian-Wen , Michelson Sara
Published: March 2020

In bulk microphysics schemes, the behavior of the multiple processes that compete for cloud water and ice can be likened to the predator-prey relationship seen in the natural world. These processes provide compensatory feedback between production processes of precipitating hydrometeors.

In this presentation, we demonstrate the sensitivity of the predator-prey processes in two commonly-used microphysics schemes of the Weather Research and Forecasting Model (WRF) to perturbations in aerosol loading, using the simulations of an idealized 2-D squall line and idealized shallow convection in the marine boundary layer. Diagnoses of the parameterized pathways for hydrometeor production microphysics budget analysis reveal that the compensatory feedback associated with the predator-prey processes are quite similar between the schemes. Overall, the compensatory feedback makes the response of a scheme to perturbations in aerosol loading smaller than the differences between the two schemes with the same aerosol loading. This indicates that there remains great uncertainty in modeling the aerosol-cloud interaction in weather and climate models. Alleviating this uncertainty requires better microphysics parameterizations as well as better observations of cloud microphysical properties.
Biogenic VOC emissions under drought and temperature stress
Authors: Blomdahl Daniel , Meredith Laura , Werner Christiane , Ladd Nemiah , Langford Ben , Nemitz Eiko , van Haren Joost , Bamburger Ines , Purser Gemma , Byron Joseph , Misztal Pawel
Published: March 2020

As climate change brings warmer temperatures and reduced precipitation to forests globally, it is vital to understand how plants adapt to drought and temperature stress. Plant activity emits biogenic volatile organic compounds (BVOC), and stress-induced changes in BVOC concentrations have important implications on secondary VOC and aerosols formation due to atmospheric reactions with ozone and other oxidants. Measurements of BVOC emissions were made at the Biosphere 2 rainforest facility near Oracle, AZ, USA from September to December 2019. Time resolved BVOC vertical concentration gradients were measured continuously using  a proton transfer reaction time-of-flight mass spectrometer (PTR-QiToF-MS, Ionicon) sampling sequentially from five levels of a vertical tower positioned at 1 m, 3 m, 7 m, 14 m and 20 m above the forest floor. Emissions of a full range of primary BVOCs are estimated from concentrations and air exchange rates. The changes in ecosystem BVOC emission are evaluated under normal precipitation conditions, then throughout a controlled 2-month drought period, and finally through a re-wet period where rain was re-introduced to the rainforest. Analysis aims to show the vertical gradient of BVOC emissions from the forest plants, as well as how BVOC concentrations changed throughout the different stress periods. BVOCs that are important for plant physiology and atmospheric science, such as isoprene and higher terpenoids, as well as other compound classes such as volatile short chain and medium chain fatty acids, will be investigated in detail. These results will give insight into how plant emissions are affected under stress, either as protective mechanisms or due to desiccation-induced responses.
Tropopause folds in North America studied from partial columns of trace gases measured at two ground-based sites
Authors: Pavia-Hernandez Ruben , Grutter Michel , Stremme Wolfgang , Strong Kimberly , Yamanouchi Shoma
Published: March 2020

Tropopause folds can change the composition of the Upper Troposphere (UT) by bringing down stratospheric parcels with different gas abundances. In this work, partial columns of gases with strong vertical gradients near the tropopause are studied during such events. Partial columns were retrieved from high-resolution infrared spectra measured at subtropical and mid-latitude locations. These stations, contributing to the Network for the Detection of Atmospheric Composition Change (NDACC), are the Altzomoni High-altitude Observatory (19.11°N, 98.66°W) in central Mexico, and the University of Toronto Atmospheric Observatory (43.66°N, 79.40°W) in southern Canada. These datasets constitute a valuable tool for studying the effects of folding on UT composition because of their time resolution (~ 1-hourly, during daylight) and the time periods they span (2012–2019 and 2002–2019, respectively). Our study shows that when tropopause folds occur, partial columns below the tropopause are correlated (anti-correlated) for species whose vertical gradients have the same (different) signs. It is also shown that tropospheric carbon monoxide (CO) in layers closest to the tropopause contributes less to the CO tropospheric partial column during folds because the UT receives low-CO air from the stratosphere.
Role of grain boundary diffusion in H-D exchange in mantle xenoliths
Authors: Thomaidis Konstantinos , Ingrin Jannick
Published: March 2020

Water concentration in pyroxenes from mantle xenoliths is frequently used to trace water content in the lithospheric mantle. We do not understand yet how these pyroxenes can preserve a memory of their deep equilibrium during their transport to the surface. In an attempt to evaluate the role of grain boundaries in the exchange of hydrogen between the pyroxenes of the xenoliths and the host magma, we have launched a program of experiments of H exchange in blocks of mantle xenoliths of centimetre size. The blocks, all from the same xenolith, contain clinopyroxenes, orthopyroxenes and olivine of mm to sub-millimetre size. We present here the results of a series of H-D exchange performed at 600, 700 and 900 oC at room pressure in a deuterium enriched gas. OH-OD profiles recorded by micro-infrared spectroscopy in pyroxenes at the edge of the block are only slightly different from the ones recorded in pyroxenes at the centre of the block. These results show that the diffusion/solubility of hydrogen in grain boundaries is fast enough to equilibrate rapidly the grains at the center of the xenoliths. It proves that in nature the δD signature of xenoliths is very likely controlled by the equilibrium with the host magma even in the case of xenoliths with large grain size.

We will also present preliminary results on the role of grain boundary diffusion in the control of hydrogen exchange involving reactions activated at a higher temperature such as the oxidation-reduction of iron (1/2H2 + Fe3+  =  Hi+ + Fe2+) and the formation/destruction of cation vacancies.
Analysis of temperature trends and urban heat island in Madrid
Authors: Maqueda Gregorio , Yagüe Carlos , Román-Cascón Carlos , Serrano Encarna , Arrillaga Jon Ander
Published: March 2020

The temperature in the cities is affected by both global climate change and local changes due to human activities and the different land use compared to rural surroundings. These local changes, which modify the surface energy budget in urban areas, include the replacement of the natural surfaces by buildings and pavements and the heat of anthropogenic origin (heating, air conditioning, traffic). Madrid city (Spain) has a current population of near 3.3 million people and a larger metropolitan area reaching around 6.5 million people. Hence, it is affected by the phenomenon called urban heat island (UHI), which indicates that a higher temperature is found in the city compared with the surrounding rural areas. UHI is defined as the temperature difference between the urban observatory and the rural one and especially affects the minimum temperatures since urban areas cool down to a lesser extent than the neighbouring rural sites. Moreover, the intensity of the UHI is modulated by the meteorological conditions (wind, cloudiness, surface pressure, precipitation), highly associated with different synoptic situations. In this work, we use the Madrid-Retiro meteorological station as the urban one, which has regular and homogeneous data from the beginning of XX century; and the station at Barajas airport (12 km from the city centre) as well as other stations out of Madrid city (but within a range of 20 km from the city centre) as the rural stations. They all have a common measuring period from 1961 until present. The main objectives of the work are: 1) to identify temperature trends in the meteorological stations (both urban and rural); 2) to evaluate the intensity of the UHI for the different rural stations; 3) to apply a systematic and objective algorithm to classify each day in different categories (related to synoptic situation) that produce a different degree of UHI intensity; and, 4) to evaluate possible trends in the UHI intensity.
Constraints on D″ beneath the North Atlantic region from P and S traveltimes and amplitudes
Authors: durand stephanie , Thomas Christine , Jackson Jennifer
Published: March 2020

In this study, we discuss possible origins of the D″ reflector beneath the North Atlantic region based on a combined analysis of P and S wave data. We use over 700 USArray station recordings of the Mw 6.3 earthquake that occurred in April 2010 in Spain. In order to investigate the D″ layer we look for waves reflected off the top of it, namely PdP and SdS waves, and compare them to the core–mantle boundary (CMB) reflections used as reference phases. The differences in traveltimes and amplitudes are sensitive to D″ properties. Because the USArray installation generates a dense array, we are able to provide an almost continuous map of the detection or absence of PdP and SdS waves in the North Atlantic region. We use a Bayesian inversion for traveltimes, together with synthetic seismogram calculations, to find the best-fitting D″ properties, (Vp, Vs) jumps across the D″ interface and D″ thickness. We find that the best-fitting models are for a D″ layer of about 300 km thick, with or without a velocity gradient of about 30 km at the top of it. Regardless of the model type, positive and similar velocity increases in both P and S velocities at the D″ interface, ranging from 2.7 to 3.8  per cent, are required to fit the data well. Our data rule out velocity decreases in P and S waves at the D″ interface as well as no velocity reduction above the CMB. There are also regions where we do not observe PdP and SdS waves. Collectively, these observations suggest lateral variations in both chemistry and temperature, combined with phase transitions. For instance, ancient oceanic basalt debris from the Farallon slab could be modulating the detection of the D″ reflector in this region. We then combine these results with ambient seismic noise data in order to extend the coverage over the same region. We will discuss some preliminary results.
Reservoirs in world’s water towers: Need for appropriate governance processes to reach Sustainable Development Goals
Authors: Kellner Elke , Brunner Manuela I.
Published: March 2020

Mountains play an essential role in storing water and providing it to downstream regions and are therefore commonly referred to as ‘water towers of the world’. In particular, they provide runoff in the lowlands’ low flow season by contributing snow- and glacier melt. Mountain runoff thus plays an important role in achieving the UN Sustainable Development Goals (SDGs), in particular regarding water, food, and energy. However, the mountains’ water provision service is strongly challenged by climate change leading to the retreat and volume loss of glaciers, rising snow lines, and changes in precipitation amount and variability. One potential strategy for addressing these changes is the construction of new water reservoirs or the adjustment of current reservoir management strategies. These strategies need to take account of various, eventually competing water uses rooted in different sectors relevant at different scales and governments with different economic interests.

We investigate the governance process related to the planning of a future reservoir in one of the most important water towers of the world, the European Alps. We ask why and how governance processes can lead to a coordination gap between upstream reservoir planning and the development of strategies allowing for the alleviation of downstream water shortage. We show on a case study in the Swiss Alps, that downstream water deficits could potentially be covered through a newly constructed upstream reservoir if management strategies were flexible enough. However, additional water uses than hydropower were not taken into account in the governance processes leading to the provision of a concession for the new reservoir. Instead, the decision-making within a participative process was influenced by (a) a lack of knowledge and data, (b) an interest to increase renewable energy production, (c) a focus on environmental agreements, and (d) economic interests. We conclude that upstream and downstream water demands need to be balanced in governance processes. Such balancing can be achieved by clarifying process design and by evaluating who can lead such complex processes with actors from different governments and sectors under the umbrella of non-uniform and incoherent institutions.
14 years of OMI HCHO observations reveal VOC emission trends over large cities worldwide
Authors: Bauwens Maite , Stavrakou Jenny , Müller Jean-François , De Smedt Isabelle , Elguindi Nellie
Published: March 2020

Formaldehyde (HCHO) observations from satellites have been widely used to constrain volatile organic compound (VOC) emission estimates. The oxidation of anthropogenic organic compounds accounts for only a small fraction(~7%) of the total HCHO column on global average (Stavrakou et al., 2009). Therefore, the use of satellite observations to infer information about anthropogenic VOC emissions is generally very challenging . However, the relative contribution of anthropogenic VOCs in and around metropolitan centers is expected to be significant. In this study, we use HCHO column data retrieved from the OMI sensor between 2005 and 2018, and calculate monthly averages for every city of more than 500,000 inhabitants based on data within 20 km of the city centers. Because of the dependence of the background and especially of the biogenic VOC source on temperature and solar radiation, and because these contributions might be significant even around large cities, it is not possible to directly infer the anthropogenic contribution to the long-term observed HCHO trends based on HCHO data. To remove these non-anthropogenic contributions, we first regress the monthly averaged columns either onto the monthly maximum surface temperature, obtained by ECMWF reanalysis data, or onto the monthly isoprene flux, calculated with the MEGAN-MOHYCAN model (Guenther et al., 2012, Stavrakou et al. 2018). Only cities for which anthropogenic emissions are estimated to exceed biogenic emission by more than a factor of 3 are considered. In this way, positive trends of up to 3% yr-1 are found over many Asian cities, especially in China and in the Indo-gangetic Plain, whereas over European cities, South Africa and South America negative trends up to -2% yr-1 are derived. The deduced trends are compared to the corresponding trends of global bottom-up anthropogenic VOC emission inventories and are found to be in good overall agreement. Model simulations are further needed to quantify the relationship between anthropogenic emission trends and HCHO columns, accounting for the effect of non-anthropogenic emissions and potential changes in the oxidizing capacity.
Global Landslide Hazard Assessment for Situational Awareness (LHASA) Version 2: New Activities and Future Plans
Authors: Kirschbaum Dalia , Stanley Thomas , Emberson Robert , Amatya Pukar , Khan Sana , Tanyas Hakan
Published: March 2020

A remote sensing-based system has been developed to characterize the potential for rainfall-triggered landslides across the globe in near real-time. The Landslide Hazard Assessment for Situational Awareness (LHASA) model uses a decision tree framework to combine a static susceptibility map derived from information on slope, rock characteristics, forest loss, distance to fault zones and distance to road networks with satellite precipitation estimates from the Global Precipitation Measurement (GPM) mission. Since 2016, the LHASA model has been providing near real-time and retrospective estimates of potential landslide activity. Results of this work are available at https://landslides.nasa.gov.

In order to advance LHASA’s capabilities to characterize landslide hazards and impacts dynamically, we have implemented a new approach that leverages machine learning, new parameters, and new inventories. LHASA 2.0 uses the XGBoost machine learning model to bring in dynamic variables as well as additional static variables to better represent landslide hazard globally. Global rainfall forecasts are also being evaluated to provide a 1-3 day forecast of potential landslide activity. Additional factors such as recent seismicity and burned areas are also being considered to represent the preconditioning or changing interactions with subsequent rainfall over affected areas. A series of parameters are being tested within this structure using NASA’s Global Landslide Catalog as well as many other event-based and multi-temporal inventories mapped by the project team or provided by project partners.

In addition to estimates of landslide hazard, LHASA Version 2 will incorporate dynamic estimates of exposure including population, roads and infrastructure to highlight the potential impacts that rainfall-triggered landslides. The ultimate goal of LHASA Version 2.0 is to approximate the relative probabilities of landslide hazard and exposure across different space and time scales to inform hazard assessment retrospectively over the past 20 years, in near real-time, and in the future. In addition to the hazard. This presentation will outline the new activities for LHASA Version 2.0 and present some next steps for this system.
Using Dynamic Adaptive Policy Pathways and hydrological modelling to co-create water resource adaptation policies for climate change: a practical example for southern Portugal
Authors: Nunes João Pedro , Dias Luís Filipe , Aparício Bruno A. , Morais Inês , Fonseca Ana Lúcia , Pastor Amandine Valérie , Santos Filipe Duarte
Published: March 2020

Mediterranean agricultural systems often rely on irrigation, which can cause conflicts with domestic water demand due to limited water resources. Climate change could enhance these conflicts by bringing a drier climate, lowering water availability, while increasing irrigation demands, therefore creating a need for timely adaptation actions. However, the creation of adaptation plans requires the integration of local policy-makers and stakeholders, both to ensure that the plans are adjusted to local physical and social conditions, and to secure investment in the implementation phase. As many are not technical experts in water resources, this integration requires innovative methodologies to ensure that knowledge gained from advanced hydrological methods can be effectively transmitted for use.

These issues were addressed in the climate change adaptation plan for water resources in the Algarve region (southern Portugal), which was co-created between hydrologists and local stakeholders and policy-makers under project CLIMAAA, by using the Dynamic Adaptive Policy Pathways (DAAP) approach to synthetize the results from hydrological modelling of future scenarios.

Future scenarios were simulated from the present until 2100 using a hydrological model, with multiple realizations of climate scenarios RCP4.5and RCP8.5. The results show an increase in water stress conditions, mainly in the RCP8.5 scenario. Future scenarios and potential adaptation measures were discussed with the local policy-makers (regional and municipal water managers) and water users (water utilities, farmer associations). An agreed-upon set of measures was then simulated with the model to assess their effectiveness for adaptation. These results were used to design a DAAP specifically for the water sector in the Algarve.

Policy-makers were then presented with the DAPP, combined with a cost assessment, and selected the most suitable and politically reliable adaptation pathway until 2100. They did not consider socially desirable to decrease irrigation use, and showed a strong preference for measures such as promoting efficient water use and water retention landscapes, which are distributed and incremental, to measures such as wastewater recycling which require a large investment. However, they did consider desalination as a last resort despite the high investment, to be applied in case other measures fail to maintain water stress below an acceptable threshold. In the end, an adaptation plan for water resources was co-created between policy-makers and researchers which strongly reflected local desires and preferences, while ensuring that its effectiveness was assessed with the best available tools; this plan is now in in the review and implementation stage.
RAHU Project: Assessing water security and climate change adaptation strategies in the glaciated Vilcanota-Urubamba river basin
Authors: Rau Pedro , Buytaert Wouter , Drenkhan Fabian , Lavado Waldo , Jimenez Juan , Montoya Nilton , Bonnesoeur Vivien , Valdivia Gustavo , Cachay Walescka , Goyburo Andres , Risco Eber , Abad Jorge , Mackay Jon , Hannah David , Barrand Nicholas , Siegert Martin , Macera Briggitte , Bueno Marcelo , Baca Carlos , Gianella Cecilia
Published: March 2020

The Peruvian Andes are a hotspot of vulnerabilities to impacts in water resources due to the propensity for water stress, the highly unpredictable weather, the sensitivity of glaciers, and the socio-economic vulnerability of its population. In this context, we selected the Vilcanota-Urubamba catchment in Southern Peru for addressing these challenges aiming at our objectives within a particular hydrological high-mountain context in the tropical Andes: a) Develop a fully-distributed, physically-based glacier surface energy balance model that allows for a realistic representation of glacier dynamics in glacier melt projections; b) Design and implement a glacio-hydrological monitoring and data collection approach to quantify non-glacial contributions to water resources and the impact of catchments interventions; c) Mapping of human water use at high spatiotemporal resolution and determining current and future levels of water (in)security; and d) Integrate last objectives in a glacier - water security assessment model and evaluate the tool's capacity to support locally embedded climate change adaptation strategies. 

The RAHU project intends to transform the scientific understanding of the impact of glacier shrinkage on water security and, at the same time, to connect to and inform policy practices in Peru. It follows a "source to tap" paradigm, in which is planned to deliver a comprehensive and fully integrated water resources vulnerability assessment framework for glacier-fed basins, comprising state-of-the-art glaciology, hydrology, water demand characterisation, and water security assessment. It includes glacio-hydrological and water resources monitoring campaigns, to complement existing monitoring efforts of our project partners and collaborators, and new remotely sensed data sets. Those campaigns will be implemented using the principles and tools of participatory monitoring and knowledge co-creation that our team has pioneered in the tropical Andes. The datasets produced by this approach, combined with existing monitoring implemented by our team and collaborators, will allow us to build an integrated water supply-demand-vulnerability assessment model for glacierized basins, and to use this to evaluate adaptation strategies at the local scale. 

This research is part of the multidisciplinary collaboration between British and Peruvian scientists (Newton Fund, Newton-Paulet).