bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of effectiveness of the water management strategies with the focus on agricultural water use: A case study on Upper-Sakarya River Basin in Turkey
Authors: Özel Beyza , Demir Yasemin , Başkan Oğuz , Alp Emre
Published: March 2020

Water, energy and food nexus is an integrated framework suggests that the security of one resource is inevitably linked to another’s. Water availability assures healthy food production whereas agriculture is the dominant user of global freshwater. Water stress due to population growth, climate change or malpractices threatens food security. Within the scope of water for food governance, the water efficiency of agricultural irrigation has to be improved to aid sustainable water and agricultural management. The study investigates water availability and withdrawals, evaluates water resources management scenarios in the agricultural sector in the Sakarya River Basin, Turkey’s third-largest river basin. Demand-oriented management scenarios propose a variety of technical measures which include improvements in irrigation technology, shifts in the cropping pattern and water-saving irrigation strategies. The effectiveness of scenarios was evaluated using the Water Evaluation and Planning (WEAP) system developed for the upper sub-basin where significant agricultural activities are held with approximately 1 million ha of total effective arable land. WEAP is an integrated water resources system modeling that operates based on the principle of water balance accounting. A climate data set of precipitation, temperature, relative humidity, and wind speed were applied across each sub-basin, partitioned into land-use classes. A one dimensional, two-bucket model for each land-use class transmits water as surface runoff, interflow, percolation, baseflow and evapotranspiration components. The model was calibrated and validated for observed streamflow, reservoir volume, and irrigation water amount. The mean annual precipitation and evapotranspiration in the upper sub-basin are 387 mm/a and 245 mm/a respectively. Agriculture is the dominant user of both surface water and groundwater resources and accounts for the %88 of total water withdrawals in the upper sub-basin. Impacts of agricultural management on irrigation water supply and flow dynamics of streamflow gauges were evaluated upon each measure. When compared to a historic baseline scenario, efficient management measures can save irrigation water up to %10 by shifting crop patterns from sunflower to safflower, %6 by establishing drip irrigation instead of sprinkler, %4 by applying deficient irrigation on cereal cultivated areas. Furthermore, mean streamflow increases by %8 in June where deficient irrigation strategy is practiced on cereals, by %9 in October where cropping pattern is shifted from sunflower to safflower. After a review of various technical measures related to the efficient management of water resources, the study concluded that sustainable agricultural development is possible by adapting conservative agricultural practices that assure water and food security.
Reflection on communicating atmospheric composition and its impacts
Authors: Volosciuk Claudia
Published: March 2020

The Global Atmosphere Watch (GAW) Programme of the World Meteorological Organization (WMO) is driven by the need to understand the variability and trends in the composition of the global atmosphere and the related physical parameters, and to assess the consequences thereof. GAW provides reliable scientific information for a broad spectrum of users, including policymakers, on topics related to atmospheric chemical composition. The programme supports international environmental and climate agreements and improves our understanding of climate change and long-range transboundary air pollution through its work on greenhouse gases, aerosols, reactive gases, atmospheric deposition, stratospheric ozone, and ultraviolet radiation. GAW provides information based on combinations of observations, data analysis and modelling activities, and supports a number of applications at the global, regional and urban scale. This implies a variety of target groups and communication vectors.

To sustain the credibility and increase the visibility of GAW within the WMO community and other national/international bodies, the broader scientific and policy communities, as well as the general public, communication efforts are required. Several activities during the EGU General Assembly 2019 have been carried out to celebrate the 30th anniversary of GAW.

For instance, a Union Symposium explored the 30 year journey from fundamental Atmospheric Composition Research to Societal Services. It showcased the importance of atmospheric composition research to climate, weather forecasting, human health, agricultural productivity and food security. The session highlighted the progress made in translating research into services, but stressed that much more needs to be done. A mentimeter survey during this Union Symposium revealed that among the scientific community GAW is valued for its coordination, observations, capacity building, outreach and its global focus.

Reflections on communication of atmospheric composition and outcomes from the 30th anniversary celebration of GAW will be presented.
Estimating emissions of methane and carbon dioxide sources using analytical Bayesian inversion system based on WRF-GHG tagged tracer simulations
Authors: Gałkowski Michał , Marshall Julia , Koch Frank-Thomas , Chen Jinxuan , Fiehn Alina , Roiger Anke , Eckl Maximilian , Kostinek Julian , Swolkień Justyna , Gerbig Christoph
Published: March 2020

During May and June 2018, the intensive campaign CoMet (Carbon dioxide and Methane mission) made atmospheric measurements of greenhouse gases over Europe, with the upper Silesian coal basin (USCB) in southern Poland as a specific focus area. CoMet aimed at characterising the distribution of CH4 and CO2 over significant regional sources with the use of a fleet of research aircraft, as well as to validate remote sensing measurements from state-of-the-art instrumentation installed on-board against a set of independent in-situ observations.

In order to link atmospheric mixing ratios to source emission rates, high-resolution simulations with WRF-GHG v 3.9.1.1. (10 km x10 km Europe + nested 2 km x 2 km domain over the USCB), driven by short-term meteorological forecasts from the ECMWF IFS model and forecasts from CAMS (Copernicus Atmospheric Monitoring Service) for initial and lateral tracer boundary conditions were performed. Biogenic fluxes of CO2 were calculated online using the VPRM model driven by MODIS indices. Anthropogenic emissions over Europe were taken from the database of TNO, Department of Climate, Air and Sustainability (7 km x 7 km), augmented with an internal emissions database developed within CoMet that uses coal mine ventilation shaft emission measurements in combination with recent updates of the E-PRTR (European Pollutant Release and Transfer Register).

Tagged tracers were used to simulate a robust set of over 100 distinct anthropogenic sources of CH4 and CO2 from the study area, and these forward simulations were then used as the transport operator in an analytical Bayesian inversion system. Here we discuss the results of an analysis performed with the use of selected in-situ data measured over the course of the three-week campaign, including results and sensitivity tests.
Towards a consistent retrieval of cloud/aerosol single scattering properties and surface reflectance
Authors: Luffarelli Marta , Govaerts Yves , Sotiriadis Sotiris , Brockmann Carsten , Kirches Grit , Storm Thomas , Pinnock Simon
Published: March 2020

The CISAR (Combined Inversion of Surface and AeRosols) algorithm is exploited in the framework of the ESA-SEOM CIRCAS (ConsIstent Retrieval of Cloud Aerosol Surface) project, aiming at providing a set of atmospheric (cloud and aerosol) and surface reflectance products derived from S3A/SLSTR observations using the same radiative transfer physics and assumptions. CISAR is an advance algorithm developed by Rayference originally designed for the retrieval of aerosol single scattering properties and surface reflectance from both geostationary and polar orbiting satellite observations.  It is based on the inversion of a fast radiative transfer model (FASTRE). The retrieval mechanism allows a continuous variation of the aerosol and cloud single scattering properties in the solution space.

Traditionally, different approaches are exploited to retrieve the different Earth system components, which could lead to inconsistent data sets. The simultaneous retrieval of different atmospheric and surface variables over any type of surface (including bright surfaces and water bodies) with the same forward model and inversion scheme ensures the consistency among the retrieved Earth system components. Additionally, pixels located in the transition zone between pure clouds and pure aerosols are often discarded from both cloud and aerosol algorithms. This “twilight zone” can cover up to 30% of the globe. A consistent retrieval of both cloud and aerosol single scattering properties with the same algorithm could help filling this gap.

The CIRCAS project ultimately aims at overcoming the need of an external cloud mask, letting the CISAR algorithm discriminate between aerosol and cloud properties. This would also help reducing the overestimation of aerosol optical thickness in cloud contaminated pixels. The surface reflectance product is delivered both for cloud-free and cloudy observations.

Results from the processing of S3A/SLSTR observations will be shown and evaluated against independent datasets.
Towards global hybrid hydrological modeling by fusing deep learning and a conceptual model
Authors: Kraft Basil , Jung Martin , Körner Marco , Reichstein Markus
Published: March 2020

Deep (recurrent) neural networks have proven very useful to model multivariate sequential data streams of complex dynamic natural systems and have already been successfully applied to model hydrological processes. Compared to physically based models, however, the internal representation of a neural network is not directly interpretable and model predictions often lack physical consistency. Hybrid modeling is a promising approach that synergizes the advantage of process-based modeling (interpretability, theoretical foundations) and deep learning (data adaptivity, less prior knowledge required): By combining these two approaches, flexible and partially interpretable models can be created that have the potential to advance the understanding and predictability of environmental systems.

Here, we implement such a hybrid hydrological model on a global scale. The model consists of three main blocks: 1) A Long-Short-Term Memory (LSTM) model, which extracts temporal features from the meteorological forcing time-series. 2) A multi-branch neural network comprising of independent, fully connected layers, taking the LSTM state as input and yielding a set of latent, interpretable variables (e.g. soil moisture recharge). 3) A conceptual model block that implements hydrological balance equations, driven by the above interpretable variables. The model is trained simultaneously on global observation-based products of total water storage, snow water equivalent, evapotranspiration and runoff. To combine the different loss terms, we use self-paced task uncertainty weighing as done in state-of-the-art multi-task learning.

Preliminary results suggest that the hybrid modeling approach captures global patterns of the hydrological cycle’s variability that are consistent with observations and our process understanding. The approach opens doors to novel data-driven simulations, attribution and diagnostic assessments of water cycle variations globally. The presented approach is—to our knowledge—the first application of the hybrid approach to model environmental systems.
A new conceptual framework for the use of hydrogen isotopes in tree rings
Authors: Lehmann Marco M. , Vitali Velentina , Schuler Philipp , Saurer Matthias
Published: March 2020

Carbon and oxygen stable isotopes in tree-rings are successfully used in climate and environmental research, for instance for the reconstruction of past climatic conditions and corresponding physiological responses of trees to local climate. In contrast, hydrogen isotope ratios (δ2H), available also in the cellulose molecule of tree-rings, have been largely neglected. Mostly due to methodological reasons, but also because various studies found a rather poor climate information in the δ2H of tree rings. Recent studies show that the latter might be caused by isotope fractionation mechanisms that are related to plant physiological and biochemical processes rather than to climate or hydrological changes. These results also suggest that a relative use of carbon reserves and photosynthetic assimilates may explain δ2H variations in tree-rings. We therefore investigated the literature and observed strong relationships between δ2H and tree growth chronologies across various species in Switzerland, Germany, Norway, China, and India. The relationships between tree-ring growth and δ2H show a dependence to site-specific factors, climatic conditions (e.g. temperature, precipitation), and competition/light effects. Based on our findings we set up a novel conceptual framework that may allow the reconstruction of physiological responses such as carbon use strategies under varying environmental conditions. This new tool may find widespread application to identify and date, with high resolution, stressful conditions or stress-release phases that a tree or a forest ecosystem has experienced in the past.
The Importance of Vegetation Build Up for Burnt Area Seasonality
Authors: Kuhn-Regnier Alexander , Voulgarakis Apostolos , Harrison Sandy , Prentice Colin
Published: March 2020

Vegetation build up is a major controlling factor for wildfires globally. The exact nature of the dependency of wildfire activity on past vegetation productivity is still under debate, however. Given the potential future rise in conditions conducive to extremely damaging fires in many regions of the world, controlling factors like this need to be investigated urgently to better understand and manage especially extreme wildfire events.
To improve our understanding of wildfires and the advice given to policy makers, a comprehensive understanding of all contributing factors is required. Changes to land management can be controversial and thus concrete evidence is required to assess and modify longstanding management practices and regulations if needed.
We therefore used global satellite datasets extending from 2005 to 2011 to assess the relationship between burnt area and various biophysical variables. Vegetation proxy data included vegetation optical depth and the fraction of absorbed photosynthetically activate radiation. Different regions and time periods were analysed separately to isolate regional and temporal effects respectively. The relationship between pre-season vegetation productivity and burnt area was modelled as a regionally and temporally varying weighted sum of past monthly productivity proxies.
As expected, significant differences in fire regimes were found across biomes, signified for example by significant shifts in the seasonality of burnt area. Understanding these shifts in the seasonality of both burnt area and the accompanying temporal dependence on past vegetation growth is key to reproducing observed wildfire regimes in fire models. As these relationships were found to vary both temporally and regionally, judicious inclusion of biophysical variables in fire models coupled with algorithms able to capture these relationships is necessary. 
However, remotely sensed observations were of different quality in different areas due to inhomogeneous cloud cover patterns, making assessments for much-affected regions like South America and South East Asia especially difficult. Likewise, the found correlation between decreasing cloud cover and increasing burnt area biased our results. Due also to the short time span of the data available in this investigation, these factors warrant further investigation to more fully quantify the temporal and regional relationships at work.
Coupled Mg/Ca and clumped isotope measurements at IODP Site U1488 confirm absence of Plio-Pleistocene sea surface temperature cooling in the Western Pacific Warm Pool
Authors: Meinicke Niklas , Reimi Maria , Ravelo Christina , Meckler Nele
Published: March 2020

The Western Pacific Warm Pool (WPWP) as a major source of heat and water vapor has a crucial influence on climate dynamics both in the tropics and globally. Yet, there is conflicting proxy evidence regarding the evolution of WPWP temperatures since the Miocene. On the one hand TEX86 data suggest a gradual cooling by ~2℃ (O’Brian et al., 2014, Zhang et al., 2014) from the Pliocene to today, while faunal (planktonic foraminifera) sea surface temperature estimates (Dowsett, 2007) and Mg/Ca data measured in planktonic foraminifera (Wara et al., 2005) on the other hand indicate the absence of any long-term temperature trends. It has been suggested that Mg/Ca temperatures could on these time scales be biased by long-term changes of the Mg/Ca ratio of seawater (Evans et al., 2016). To test the influence of the proposed seawater changes on Mg/Ca we combined data from two independent temperature proxies, Mg/Ca and clumped isotopes, measured on two species of planktonic foraminifera from IODP Site U1488 in the central WPWP. Our study finds good agreement between both proxies thereby verifying the validity of Mg/Ca records from the WPWP and confirming the absence of a Plio-Pleistocene cooling trend for the WPWP. This finding suggests that the persistent disagreement between foraminifer-based proxies such as Mg/Ca and biomarker data might be caused by different environmental parameters being recorded in the two archives.

 

References:

O’Brien CL, Foster GL, Martínez-Botí MA, Abell R, Rae JWB, Pancost RD. High sea surface temperatures in tropical warm pools during the Pliocene. Nature Geoscience. 2014;7(8):606-11.

Zhang YG, Pagani M, Liu Z. A 12-million-year temperature history of the tropical Pacific Ocean. Science. 2014;344(6179):84-7.

Dowsett H. Faunal re-evaluation of Mid-Pliocene conditions in the western equatorial Pacific. Micropaleontology. 2007;53(6):447-56.

Wara MW, Ravelo AC, Delaney ML. Permanent El Nino-like conditions during the Pliocene warm period. Science. 2005;309(5735):758-61.

Evans D, Brierley C, Raymo ME, Erez J, Müller W. Planktic foraminifera shell chemistry response to seawater chemistry: Pliocene–Pleistocene seawater Mg/Ca, temperature and sea level change. Earth and Planetary Science Letters. 2016;438:139-48.
Update on IAGOS greenhouse gas observations from commercial airliners
Authors: Gerbig Christoph , Franke Harald , Stosius Ralf , Obersteiner Florian , Gehrlein Torsten , Zahn Andreas
Published: March 2020

Within the framework of the research infrastructure IAGOS (In-service Aircraft for a Global Observing System), a cavity ring-down spectroscopy (CRDS)-based measurement system for the autonomous measurement of the greenhouse gases (GHGs) CO2 and CH2, as well as CO and water vapour is deployed on a Lufthansa Airbus A330 since September 2018. This IAGOS-CORE system is equipped with a two-standard in-flight calibration system, allowing for trace gas measurements to be fully traceable to WMO calibration scales. Various lessons have been learned during the first deployment periods related to the autonomous operation of the system over periods of several months, enabling the future extension of the GHG measurements to aircraft from further airlines. Apart from the presentation of the observations, the presentation will discuss the data quality and uncertainty estimation.

A further CRDS system for autonomous measurement CO2 and CH4 is integrated within the instrumented IAGOS-CARIBIC container deployed on board an Airbus A340 on a bi-monthly schedule since July 2018. By now this system has provided data from more than 30 flights. Data will be presented, and the potential of the observations for research applications will be introduced. Also the availability of IAGOS GHG data to the research community will be discussed.
High-energy radiation from natural lightning observed in coincidence with a VHF Lightning Interferometer
Authors: Urbani Michele , Montanyà Joan , Van der Velde Oscar , López Jesús Alberto
Published: March 2020

In the last two decades, it has been discovered that lightning strikes can emit high-energy radiation.
In particular, a phenomenon has been observed from space called "Terrestrial Gamma-ray Flash'' (TGF), which consists of an intense burst of gamma radiation that can be produced during thunderstorms. This phenomenon has met with considerable interest in the scientific community and its mechanism is still not fully understood. Nowadays several satellites for astrophysics like AGILE and FERMI are able to detect and map TGFs and specific instruments like the ASIM detector on the ISS are studying this phenomenon from space.
In the atmosphere, the high-energy radiation undergoes a strong absorption exponentially proportional to the air density which makes it more difficult to detect TGFs on the ground. Nonetheless, ground measurements were conducted and observed that even in cloud-to-ground lightning high-energy radiation were produced. In particular, the works of Moore et al. [2001] and Dwyer et al. [2005] highlight two lightning processes in which the X-ray emission could be produced: downward negative stepped leader and dart leader. Currently, it is not clear if the emissions revealed on the ground and the TGFs observed in space are essentially the same phenomenon or how these phenomena are related. For these reasons, it is particularly interesting to study high-energy emissions also from ground instruments because, despite the strong absorption of the high-energy radiation, ground observations can reach a better accuracy in time and space and provide crucial information to investigate the origin and conditions under which these emissions occur.
A privileged instrument for this research is the VHF Lightning Interferometer, a system of antennas that allows you to map lightning through the very high frequency (VHF) emission. Due to the high resolution of this instrument, should be possible to locate the origin of the high-energy emissions and hopefully provide a better understanding of the radiation mechanism.
The aim of this research is, therefore, to develop a 3D interferometry system to identify as accurately as possible the origin and the conditions in which the X-ray emission occurs in cloud-to-ground lightning and investigate the relation of the VHF emissions with the TGFs.
Recently an observation campaign was conducted in Colombia with two VHF Lightning Interferometers and two X-rays detectors. This interferometry system was installed in the coverage area of a Lightning Mapping Array (LMA) and LINET to take advantage of the complementary information that these lightning location networks could provide. At the moment, about 15 lightning events with X-ray emissions were observed, including five X-ray bursts from downward negative leaders and two emissions from dart leaders. Further studies and analysis of the collected data are still ongoing.
Towards understanding the roll-back subduction of narrow oceanic domains: inferences from the modelling of Carpathians subduction zone
Authors: Bozsó István , van Dinther Ylona , Matenco Liviu , Kovács István
Published: March 2020

Numerous subduction systems in the Meditteranean realm are derived from the subduction of narrow oceanic domains, which are too narrow to generate the means of a fully coupled two-dimensional thermo-mechanical numerical model that takes into account the visco-elasto-plastic properties of different lithospheric domains. The results show that the narrow extent of the Ceahlau-Severin Ocean commonly assumed by paleogeographic reconstruction cannot generate roll-back upon subduction, in particular for models that must assume that slabs do not penetrate the 660 km discontinuity. Therefore, we propose that the subduction of the Carpathians system must have an inherited component from a previous orogenic evolution, which will ensure sufficient slab-pull to generate roll-back in the Carpathians realm. The model is constrained by recent results in terms of mantle structure and geodynamic reconstructions, while multiple compositional, thermal distribution and geometrical scenarios are tested in successive models. In all of our models, roll-back is achieved, which indicates that the proposed inherited component can sufficiently explain the roll-back subduction of the aforementioned narrow oceans. The subducting oceanic slab does not penetrate the 660 km discontinuity, this is in agreement with seismic tomographic results from various Mediterranean subduction zones. The exact onset and dynamics of the roll-back are mostly controlled by the thermic age of the ocean and the convergence kinematics of the continental slabs. An outlook on possible future improvements to the model, such as taking into account pre-existing rheological weakness zones in the lithosphere, is discussed and the opportunity of a seismo-thermo-mechanical modelling to investigate the seismic cycle in the Vrancea-zone is highlighted.
Evaluation of two automated inundation-mapping methods
Authors: Hocini Nabil , Gaume Eric , Payrastre Olivier , Bourgin François , Davy Philippe , Lague Dimitri , Pons Frédéric , Poinsignon Léa
Published: March 2020

Flash Floods cause significant material and human damage worldwide. In France, they frequently hit small rivers of the Mediterranean area, often inducing catastrophic consequences.

Considering the large number of possibly affected small watercourses, the use of automated flood-mapping methods may be of great help for the identification of the possibly affected areas and the prediction of the potential consequences of this type of floods.

In 2019, a first evaluation of three automated inundation-mapping methods, directly implemented on high-resolution Digital Terrain Models (DTM) was presented (https://meetingorganizer.copernicus.org/EGU2019/EGU2019-15710-1.pdf). The automatically retrieved flood extent maps were compared with simulated reference maps from local expert studies.        

As a continuation of this work, an application of the two best performing of these methods (1D caRtino approach and 2D Floodos approach), is presented here for the simulation of  three recent flash flood events:

The 15th of June 2010 flood on the Argens watershed: 25 deaths, more than 1 billion € of economic damage, 585 km of affected and simulated rivers.

The 3rd – 4th, of october 2015 floods in the French Riviera: 20 deaths, and 600 million € of economic damage, 131 km of affected and simulated rivers.

The 15th - 16th of October 2018 flood on the Aude watershed: 15 deaths, approximatively 300 million € of economic damage, 569 km of affected and simulated rivers.

At first, the peak discharges for each reach of the stream network are estimated with a hydrological model (CINECAR), calibrated against discharge values based on extensive post-event surveys. The hydraulic simulations with the two methods are then run for each reach separately in steady-state regime, based on estimated peak discharges, to obtain simulated flood maps at the reach scale that are then combined to obtain a flood extent map for the simulated event. The computation times are calculated for the two methods and compared.

The simulation results are compared with observed flood extent maps and high water marks. The flood extent maps are compared based on a critical success index criterion (CSI), showing an overall very good correspondence. The simulated water levels show a difference of less than 50 cm with high water marks in most cases.

Finally, a sensitivity analysis to the quality of DTM input information and roughness coefficients is presented.
High-resolution combined global gravity field modelling – The d/o 5,400 XGM2020 model
Authors: Zingerle Philipp , Pail Roland , Gruber Thomas
Published: March 2020

Within this contribution we present the new experimental combined global gravity field model XGM2020. Key feature of this model is the rigorous combination of the latest GOCO06s satellite-only model with global terrestrial gravity anomalies on normal equation level, up to d/o 2159, using individual observation weights. To provide a maximum resolution, the model is further extended to d/o 5400 by applying block diagonal techniques.

To attain the high resolution, the incorporated terrestrial dataset is composed of three different data sources: Over land 15´ gravity anomalies (by courtesy of NGA) are augmented with topographic information, and over the oceans gravity anomalies derived from altimetry are used.  Corresponding normal equations are computed from these data sets either as full or as block diagonal systems.

Special emphasis is given to the novel processing techniques needed for very high-resolution gravity field modelling. As such the spheroidal harmonics play a central role, as well as the stable calculation of associated Legendre polynomials up to very high d/o. Also, a new technique for the optimal low-pass filtering of terrestrial gravity datasets is presented.

On the computational side, solving dense normal equation systems up to d/o 2159 means dealing with matrices of the size of about 158TB. Handling with matrices of such a size is very demanding, even for today’s largest supercomputers. Thus, sophisticated parallelized algorithms with focus on load balancing are crucial for a successful and efficient calculation.
Mars’ ionopause: A game of pressures
Authors: Sanchez-Cano Beatriz , Narvaez Clara , Lester Mark , Mendillo Michael , Mayyasi Majd , Holmstrom Mats
Published: March 2020

The ionopause is a tangential discontinuity in the ionospheric thermal plasma density profile that marks the upper boundary of the ionosphere for unmagnetized planets. This interface is formed by a balance of pressures, as the ionopause is the region where the total pressure of the ionosphere (ionospheric thermal pressure plus magnetic pressure) balances the solar wind ram pressure. Since only Venus and Mars have no global “dipole” magnetic fields, ionopauses are unique to those planets. For Venus, the ionopause formation is well characterized because the thermal pressure of the ionosphere is usually larger than the solar wind dynamic pressure. For Mars, however, the maximum thermal pressure of the ionosphere is usually insufficient to balance the total pressure in the overlying magnetic pileup boundary. Therefore, the Martian ionopause is not always formed, and when it does, it is located at a large range of altitudes, varies rapidly and is highly structured. In this study, we characterise the Martian ionopause formation from the point of view of the thermal, magnetic and dynamic pressure balance. The objective of this paper is to assess under which circumstances the Martian ionopause is formed, both over and far from crustal magnetic fields. We focus on three MAVEN deep dip campaigns that occurred on the dayside of Mars, and we utilize several multi-plasma and magnetic field in-situ observations from the MAVEN mission, as well as solar wind plasma observations from the Mars Express mission.
Modelling the role of selection and complementarity in ecosystem function under climate change
Authors: Millington Rebecca , Cox Peter M. , García Francisca C. , Yvon-Durocher Gabriel
Published: March 2020

Understanding how ecosystem function depends on temperature is important in understanding ecosystem resilience to climate change. The response to warming at a species level is relatively well understood, through the metabolic theory of ecology, which captures the temperature dependence of biological processes. However, when multiple species are present, interactions between the species are important too. Therefore, to understand community function, we must understand the response of the individual species, and the interactions between them. These interactions may depend on temperature, and can be split into two main mechanisms: selection and complementarity. Both of these processes are likely to depend on the number of species present; the biodiversity of the ecosystem. Currently, the response of communities to temperature change, and how changes in diversity may increase or buffer impacts, is poorly understood.

 

Our understanding of ecosystem function can be improved by using mathematical models to constrain the mechanisms underlying key processes. Using data from laboratory experiments, we model communities of heterotrophs responding to temperature change. To model selection, we use a simple model of a community sharing a resource, with parameters measured empirically. Without complementarity, the model underestimates community function. Complementarity is included through a single parameter, which determines to what extent different taxa share the same resource pool. This parameter is difficult to measure directly, so must be fitted using empirical community function data. Through our model, we show that the strength of complementarity within a community depends on both diversity and temperature. Interestingly, we also find that complementarity is strongest at higher and lower temperatures, and more dependent on diversity at medium temperatures.
Surface mass balance and melting projections over the Amundsen coastal region, West Antarctica
Authors: Jourdain Nicolas , Donat-Magnin Marion , Kittel Christoph , Agosta Cécile , Amory Charles , Gallée Hubert , Krinner Gerhard , Chekki Mondher
Published: March 2020

We present Surface Mass Balance (SMB) and surface melt rates projections in West Antarctica for the end of the 21st century using the MAR regional atmosphere and firn model (Gallée 1994; Agosta et al. 2019) forced by a CMIP5-rcp85 multi-model-mean seasonal anomaly added to the ERA-Interim 6-hourly reanalysis.

 

First of all, we assess the validity of our projection method, following a perfect-model approach, with MAR constrained by the ACCESS-1.3 present-day and future climates. Changes in large-scale variables are well captured by our anomaly-based projection method, and errors on surface melting and SMB projections are typically 10%.

 

Based on the CMIP5-rcp85 multi-model mean, SMB over the grounded ice sheet in the Amundsen sector is projected to increase by 35% over the 21st century. This corresponds to a SMB sensitivity to near-surface warming of 8.3%.°C-1. Increased humidity, resulting from both higher water vapour saturation in warmer conditions and decreased sea-ice concentrations, are shown to favour increased SMB in the future scenario.

 

Ice-shelf surface melt rates at the end of the 21st century are projected to become 6 to 15 times larger than presently, depending on the ice shelf under consideration. This is due to enhanced downward longwave radiative fluxes related to increased humidity, and to an albedo feedback leading to more absorption of shortwave radiation. Interestingly, only three ice shelves produce runoff (Abbot, Cosgrove and Pine Island) in the future climate. For the other ice shelves (Thwaites, Crosson, Dotson, Getz), the future melt-to-snowfall ratio remains too low to produce firn air depletion and subsequent runoff.

 
Free soil colloids and colloidal building units of soil aggregates
Authors: Tang Ni , Siebers Nina , Klumpp Erwin
Published: March 2020

Nanosized mineral particles and organic matter (<100 nm) ,as well as their associations, belong to the most important ingredients for the formation of the soil aggregate structure being a hierarchically organized system. Colloids (< 220 nm) including nanoparticles can be occluded as primary building units of soil aggregates. Nevertheless, a large proportion of these colloids is mobile and presents in the solution phase (as “free”) within the soil matrix. However, the differences between “free” and occluded colloids remain unclear.

Here, both occluded and free colloids were isolated from soil samples of an arable field with different clay contents (19% and 34%) using wet sieving and centrifugation. The release of occluded colloids from soil macroaggregates (>250 µm) was carried out with ultrasonic treatment at 1000 J mL-1. The free and occluded colloidal fractions were then characterized for their size-resolved elemental composition using flow field-flow fractionation inductively coupled plasma mass spectrometry and organic carbon detector (FFF-ICP-MS/OCD). In addition, selected samples were also subjected to transmission electron microscopy as well as pyrolysis field ionization mass spectrometry (Py-FIMS).

Both, free and occluded colloids were composed of three size fractions: nanoparticles <20 nm, medium-sized nanoparticles (20 nm–60 nm), and, fine colloids (60 nm–220 nm). The fine colloid fraction was the dominant size fraction in both free and occluded colloids, which mainly consist of organic carbon, Al, Si, and Fe, probably present as phyllosilicates and associations of Fe- and Al- (hydr)oxides and organic matter. However, the organic matter contents for all three size fractions were higher for the occluded colloids than for the free ones. The role of OM concentration and composition in these colloids will be discussed in the paper.
Effects of the observed Earth’s oblateness variation on precession-nutation: A first assessment
Authors: Ferrándiz José M. , Escapa Alberto , Baenas Tomás , Belda Santiago , Vigo M. Isabel
Published: March 2020

The current IAU2000 nutation theory considers the Earth’s dynamical ellipticity as a constant, whereas the IAU2006 precession theory uses a linear model for it. Apart from the problems of consistency between the two theories, whose full solution was proposed recently, the fundamental issue, namely whether the observed time variation of the Earth’s gravity field can affect the Earth’s rotation to a non-negligible extent or not, remains untreated.

This presentation is intended to share some preliminary results concerning precession and nutation. The variation of the Earth’s dynamical ellipticity is modelled from one of the time series providing the time-varying Stokes coefficients, and its effects on the longitude are computed following a new method introduced by the authors to that purpose. The found variations are above the accuracy goals of GGOS, the Global Geodetic Observing System of the International Association of Geodesy, adopted by its Joint Working Group on Improving theories and models of the Earth rotation (JWG ITMER).
A new multidisciplinary observatory in the Eastern Ligurian Sea (NW Mediterranean Sea): a combination of deep-sea and coastal measurements
Authors: Ciuffardi Tiziana , Berta Maristella , Bordone Andrea , Borghini Mireno , Celentano Paolo , Cocchi Luca , De Fabritiis Letizia , Delbono Ivana , Delfanti Roberta , Demarte Maurizio , Ivaldi Roberta , Kokkini Zoi , Locritani Marina , Marini Davide , Marini Simone , Muccini Filippo , Pannacciulli Federica , Peirano Andrea , Raiteri Giancarlo , Vetrano Anna
Published: March 2020

Climate change investigation, protection of marine ecosystems and mitigation of natural risks are the main research objectives of the Levante Canyon Mooring (LCM), a deep submarine multidisciplinary observatory, installed in September 2019 in the Eastern Ligurian Sea (Lat 44°05.443'N, Long 009°29.900'E at 608 m depth), inside the Pelagos Sanctuary. The observatory consists of a stand-alone station, with an instrumented mooring line ending with a submerged buoy. It operates in delayed-mode and is equipped with sensors that measure physical and biogeochemical parameters continuously and it is expected to provide data in the long-term. Temperature and salinity monitoring is carried out at three depth levels (about 80, 335 and 580 m depth), while turbidity is recorded at 580 m depth. LCM is also equipped with a sediment trap and two acoustic current profilers, able to measure direction and speed of currents in nearly the entire water column.

Data will be used to measure flux of sediments, nutrients and organic matter and to better understand the hydrodynamic and physical conditions of the Levante Canyon, which hosts valuable and vulnerable ecosystems, such as the deep-living cold-water corals, identified by IIM and ENEA in 2014, near the LCM mooring site. The LCM site is also located in an area where surface currents are monitored in near-real time by the CNR’s High Frequency Radar network, allowing data integration from multiplatform observations.

The project, co-financed by the Liguria Region, is coordinated by the DLTM in strict collaboration, in terms of human resources, infrastructures and instruments with the associated public research bodies (CNR, ENEA, INGV) and with the IIM. The project also includes the next deployment of a cabled station in the Gulf of La Spezia (10 m depth, less than 100 m far from the coast) that will monitor the gravimetric field, temperature and marine current. The main objective of the coastal station is to provide a test site for new instruments and sensors.
Tectonically-dominated Quaternary landscape evolution of the Ventura basin, southern California, quantified using cosmogenic isotopes and topographic analyses
Authors: Rood Dylan , Hughes Alex , Whittaker Alex , Bell Rebecca , Wilcken Klaus , Corbett Ashley , Bierman Paul , DeVecchio Duane , Rockwell Thomas
Published: March 2020

Spatial and temporal variations in fault activity informs models of seismic hazards and can affect local patterns of relief generation and channel morphology. Therefore, the quantification of rates of fault activity has important applications for understanding natural hazards and landscape evolution. Here, we quantify the complex interplay among tectonic uplift, topographic development, and channel erosion recorded in the hanging walls of several seismically-active reverse faults in the Ventura basin, southern California, USA. We use cosmogenic 26Al/10Be isochron burial dating to construct a basin-wide geochronology for the Saugus Formation: an important, but poorly dated, regional Quaternary strain marker. Our geochronology of the Saugus Formation is used to calculate tectonically-driven rock uplift rates and reduce uncertainties in fault-slip rates. In addition, we calculate 10Be catchment-averaged erosion rates, characterise patterns of catchment relief and channel steepness indices, and analyse river long-profiles in fault hanging walls to compare with patterns of fault displacement rates averaged over various temporal scales.

 

The results of the burial dating confirm that the Saugus Formation is time-transgressive with ages for the top of the exposed Saugus Formation of ~0.4 Ma in the western Ventura basin and ~2.5 Ma in the eastern Ventura basin. The burial ages for the base of shallow marine sands, which underlie the Saugus Formation throughout the basin, are ~0.6 Ma in the western Ventura basin and ~3.3 Ma in the eastern Ventura basin. The results of the landscape analysis indicate that relief, channel steepness, and erosion rates are still adjusting to tectonic boundary conditions imposed by different tectonic perturbations that have occurred at various times since ~1.5 Ma, which include fault initiation and fault linkage. The data presented here suggest that, for transient landscapes in sedimentary basins up to 2500 km2, where climate can be considered uniform, fault activity is the primary control on patterns of relief generation and channel morphology over periods of 104 to 106 years.
A Catalogue of Coronal Mass Ejections Observed by the Heliospheric Imagers throughout the STEREO Mission
Authors: Barnes David , Davies Jackie , Harrison Richard
Published: March 2020

Understanding the evolution of the solar wind is fundamental to advancing our knowledge of energy and mass transport in the solar system, rendering it crucial to space weather and its prediction. The advent of truly wide-angle heliospheric imaging has revolutionised the study of Coronal Mass Ejections (CMEs) by enabling their direct and continuous observation out to 1 AU and beyond. A catalogue of CMEs has been compiled using data from the Heliospheric Imagers (HIs) on board the two STEREO spacecraft, which began as part of the FP7 HELCATS project. The mission was launched in 2006 and continues to provide data, therefore spanning 13 years, over which more than two-thousand CMEs have been observed using HI. To these CMEs, we apply geometric models that make use of both single-spacecraft and stereoscopic observations in order to determine their kinematic properties. These include CME speed, acceleration, propagation direction and launch time. The resulting kinematic properties and their statistics are discussed in the context of existing CME catalogues produced from coronagraph observations. This is done with emphasis on how the different models we apply influence our results and how these differences evolve over the solar cycle and as the angular separation of the STEREO spacecraft increases throughout the mission.
Quantification of flood hazard for the megacity of Lagos, Nigeria, by hydrodynamic simulation
Authors: Pilz Tobias
Published: March 2020

Climate change leads to rising temperatures and therefore stimulates the water cycle. As a consequence, extreme events in rainfall and associated flooding are projected to increase in frequency and severity in many regions of the world. Especially in developing countries with high population growth and often unregulated settlement, flood risk may increase due to both increased flood hazard and enhanced exposure. One such example is the megacity of Lagos, Nigeria, belonging to the largest cities in Africa. Floods within the city are recurrent and caused by storm surges from the Atlantic, heavy precipitation, and river floods. Flood risk is an issue and even expected to increase due to enhanced extreme precipitation, sea level rise, enhances storm surges, as well as illegal settlement, poor management, insufficient or blocking of drainage channels, missing early warning systems, and insufficient data.

The aim of this study is to deliver a first quantification of flood hazard for the city of Lagos based on hydrodynamic simulation with the model TELEMAC-2D. A focus is put on the use of freely available data sources and the design of reproducible workflows in order to enable local decision-makers to individually apply and refine the established workflows. The biggest challenge is the generation of the model mesh as the basis for subsequent hydrodynamic modelling due to limited data availability and the size of the model domain (about 1000 km²).
CO2 ice grain size retrievals from SPICAM IR/MEX spectra
Authors: Lomakin Alexander , Fedorova Anna , Berdis Jodi , Korablev Oleg , Montmessin Franck
Published: March 2020

CO2 cycle on Mars defines fundamental processes both on the surface and in the atmosphere. On poles condensation of a large part of the atmosphere (up to 30%) results seasonal growth and retreat of polar caps, changing reflectance and emissivity of the surface, that has dramatic consequences for energy budget and changes local and global climate on the planet. SPICAM-IR is an AOTF-based infrared spectrometer onboard Mars Express mission operating in range 1-1.7 μm with middle resolving power about 2000. SPICAM provides continuous monitoring of the Martian surface in near IR since 2004 during already 8 Martian Years. Still, the surface albedo that can be derived from this dataset was never analyzed. In this work, we will focus on the retrieval of the CO2 ice properties (like grain size) from the SPICAM dataset based on the Hapke model. We will present the retrieval algorithm and results for a number of selected orbits over the South pole.