bluuebunny/crossref_metadata_2025 huggingface dataset:
Tree vitality and forest health: any better indicators?
Authors: Cherubini Paolo , Battipaglia Giovanna , Innes John L.
Published: March 2021

Forest health, although not yet unanimously defined, has been monitored in the past forty years assessing tree vitality, trying to estimate tree photosynthesis rates and productivity. Used in monitoring forest decline in Central Europe since the 1980s, crown foliage transparency has been commonly believed to be the best indicator of tree condition in relation to air pollution, although annual variations appear more closely related to water stress. Although crown transparency is not a good indicator of tree photosynthesis rates, defoliation is still one of the most used indicators of tree vitality. Tree rings have been often used as indicators of past productivity. However, long-term tree-growth trends are difficult to interpret because of sampling bias, and ring-width patterns do not provide any information about tree physiological processes. In the past two decades, tree-ring carbon and oxygen stable isotopes have been used  to reconstruct the impact of past climatic events, such as drought. They have proven to be useful tools for retrospectively understanding physiological processes and tree response to  stress factors. Tree-ring stable isotopes integrate crown transpiration rates and photosynthesis rates and may enhance our understanding of tree vitality. They are promising indicators of tree vitality. We call for the use of tree-ring stable isotopes in future monitoring programmes.
The Range of Jupiter's Flow Structures that Fit the Juno Asymmetric Gravity Measurements
Authors: Duer Keren , Galanti Eli , Kaspi Yohai
Published: March 2021

The asymmetric gravity field measured by the Juno spacecraft has allowed the estimation of the depth of Jupiter's zonal jets, showing that the winds extend approximately 3,000 km beneath the cloud level. This estimate was based on an analysis using a combination of all measured odd gravity harmonics, J3, J5, J7, and J9, but the wind profile's dependence on each of them separately has yet to be investigated. Furthermore, these calculations assumed the meridional profile of the cloud‐level wind extends to depth. However, it is possible that the interior jet profile varies somewhat from that of the cloud level. Here we analyze in detail the possible meridional and vertical structure of Jupiter's deep jet streams that can match the gravity measurements. We find that each odd gravity harmonic constrains the flow at a different depth, with J3 the most dominant at depths below 3,000 km, J5 the most restrictive overall, whereas J9 does not add any constraint on the flow if the other odd harmonics are considered. Interior flow profiles constructed from perturbations to the cloud‐level winds allow a more extensive range of vertical wind profiles, yet when the meridional profiles differ substantially from the cloud level, the ability to match the gravity data significantly diminishes. Overall, we find that while interior wind profiles that do not resemble the cloud level are possible, they are statistically unlikely. Finally, inspired by the Juno microwave radiometer measurements, assuming the brightness temperature is dominated by the ammonia abundance, we find that depth‐dependent flow profiles are still compatible with the gravity measurements.
Environmental effects of silver iodide emitted by hail suppression systems in Aragón (Spain)
Authors: Orellana-Macías José María , Causapé Jesús , Pey Jorge , Valero-Garcés Blas , Reyes Jesús , Vázquez Iciar
Published: March 2021

Weather modification by means of cloud seeding techniques is widely implemented across the world. In areas where hail suppression systems are installed, silver iodide (AgI) particles are used.

Silver particles fall back to the surface thank to atmospheric deposition. In this research we follow a holistic approach to analyse silver accumulation in water, soils and sediments of Aragón (North-East Spain), where AgI emissions have been released for the last fifty years. We have also assessed silver bioaccumulation in plants and biota, and we have tested its effects in plant growth.

Our results show that silver concentrations in water and soils of areas covered by hail suppression networks are higher than in further areas, although concentrations are below legal thresholds. We have also observed that silver seems to be absorbed by plants and biota, which would act as a silver outflow and it may help to remove silver from the ecosystems.

Acknowledgements

This work was funded by Spanish State Research Agency and FEDER Funds via AgroSOS project (PID2019-108057RB-I00) and DONAIRE project (CGL2015-68993-R), and thanks to a pre-doctoral grant awarded by the Government of Aragon to J. M. Orellana-Macías (BOA 20/ 07/2017).
Electrical resistivity contrast between active layer and frozen ground: why is it similar for different sites over many order of magnitudes ?
Authors: Hauck Christian
Published: March 2021

Geophysical techniques are widely used to detect and characterise permafrost. Among them, electrical methods such as Electrical Resistivity Tomography (ERT) or Vertical Electrical Soundings (VES) , which measure the electrical resistivity of the ground, have a very long and successful tradition in all kind of permafrost applications in polar, mountain and subsea terrain. Similarly, electromagnetic methods, which measure the inverse of resistivity, the electrical conductivity, are more and more used for permafrost applications.

The reason for the good applicability lies in the fact that the electrical resistivity of most materials increases sharply at the freezing point. The nature of this increase is due to several processes such as the reduction of the electrically conducting liquid water content during phase change and the reduced mobility of the ions in the liquid phase. How much the resistivity increases upon freezing depends therefore on the specific physical properties of the material (e.g. porosity, pore water resistivity), which can be completely different for the different permafrost environments and lithospheric materials.

On the other hand, when plotting the resistivity of the active layer against the resistivity of the frozen layer for a multitude of data sets, most permafrost occurrences follow a similar quantitative relationship, although their lithopsheric and geomorphological characteristics are very different. In this contribution we will analyse the reasons for this relationship using theoretical considerations and verify it with a newly compiled resistivity data set of more than 100 permafrost occurrences.
Changes in cyclone circulation and storm tracks under different future climate scenarios
Authors: Priestley Matthew , Catto Jennifer
Published: March 2021

Extratropical cyclones have the potential to cause large damages across the mid-latitudes. Future climate change is projected to have a large impact on the location of the storm tracks, and the frequency of these cyclones, however the sign and magnitude of these responses has been uncertain for regions near the end of the storm tracks in previous coupled and idealized modelling studies.

 

Through the use of a Lagrangian cyclone tracking method we quantify changes in the storm tracks for both summer and winter seasons in both hemispheres for four future climate scenarios using a number of CMIP6 models. A cyclone compositing technique is employed to identify changes in cyclone circulation for the strongest cyclones in the lower, middle, and upper troposphere. We identify an intensification of the cyclone circulation in all seasons, apart from NH summer, where a weakening is detected. Cyclone size is also projected to increase, with a widening of the pressure and wind fields.

 

These results have significant implications from a socio-economic perspective. Despite a projected decrease in cyclone numbers, an increase in severity may lead to more drastic windstorms and larger impacts across heavily populated regions of the mid-latitudes.
Elusive active faults in a low strain rate region (Sicily, Italy): hints from a multidisciplinary land-to-sea approach 
Authors: Parrino Nicolò , Pepe Fabrizio , Burrato Pierfrancesco , Dardanelli Gino , Di Maggio Cipriano , Corradino Marta , Pipitone Claudia
Published: March 2021

Low Strain Rate regions (LSRr), i.e., areas deforming at a 1 mm/yr rate or less, represent the most globally widespread areas that host important cities and high-vulnerable anthropogenic assets. The occurrence of infrequent but high-magnitude earthquakes suggests that identifying active structures in the LSRr is one of the primary challenges for both the scientific community and modern societies.

In such regions, one of the main issues in identifying active faults is the lack of useful outcrop data due to the anthropogenic and climate overprinting of the faults morphological signature. In this work, we propose a multidisciplinary approach designed to detect active geological structures and their related deformation. To test this approach, we selected as a natural laboratory an LSRr located between two major cities of Sicily (southern Italy).  This area lies into the northern sector of the Apennine-Maghrebian fold and thrust belt and its offshore prolongation.

Our approach consists of quantitative morphotectonic, offshore and onshore tectonostratigraphic and GNSS joint analyses. The main achieved results are 1) the first evidence of active, shallow-sited, NNW-trending transpressive blind faults that extends partially offshore for about 30 km, which décollement levels located at about 3 and 1 km depth, respectively and their 3D model, 2) a morphotectonic evolution model, that represents where and how these geologic structures drove the landscape evolution of the study area. Finally, we highlight that only a multidisciplinary approach could be useful for detecting and parametrising active faults in slow deforming areas that cross the coastline physical limit.
Unprecedented climate extremes in Sub-Saharan Africa and implications for maize production
Authors: Bradshaw Catherine , Pope Edward , Kay Gillian , Davie Jemma , Cottrell Andrew , Bacon James , Jennings Stewart , Challinor Andrew , Chapman Sarah , Birch Cathryn , Sallu Susannah
Published: March 2021

Sub-Saharan Africa is one of the most food-insecure regions in the world, and is particularly vulnerable to the impacts of extreme climate events and climate change.  To gain a better understanding of the present-day likelihood of extreme seasonal temperature and rainfall events, and their joint occurrence, we apply the UNprecedented Simulated Extremes using ENsembles (UNSEEN) approach  to a large ensemble of high-resolution initialised climate simulations in three countries of Sub-Saharan Africa: Tanzania, Zambia and South Africa. We assess the annual likelihood of unprecedented seasonal temperature and precipitation extremes during the maize growing season (October-April), as key variables for maize productivity , and investigate the large-scale dynamics of the climate system that govern their occurrence. We estimate that there is a 3-4% chance per year of exceeding the present-day seasonal temperature records in the maize growing regions of these countries, and a 1-3.5% chance per year of exceeding the present-day seasonal precipitation records.  Conversely, whilst we find a 2% and 5% chance per year of subceeding the present-day seasonal precipitation records in Zambia and Tanzania respectively, we find a very low chance (0-1% per year) of subceeding the present-day seasonal precipitation records in South Africa.  We also use the large ensemble to investigate the large-scale dynamics of the climate extremes, finding that high temperature extremes tend to be associated with El Niño and positive IOD/SIOD events and low temperature extremes with La Niña and negative IOD/SIOD events. The drivers of precipitation extremes, however, differ between the countries. In South Africa, high (low) precipitation extremes are associated with La Niña (El Niño) events but otherwise the influence on extremes of ENSO, and even more so the IOD/SIOD, is weak or not seen in the ensemble, which invites further investigation. To explore implications for growing maize in these regions, we convert our unprecedented seasonal temperature estimates to daily maximum temperatures and our seasonal precipitation estimates to monthly precipitation indices and compare to climatic thresholds for maize. Combined with projected changes to crop suitability in much of sub-Saharan Africa, our analysis suggests the need for significant adaptation strategies that build food system resilience in the near and longer term.
Tropical Cyclone Characteristics Associated with Extreme Precipitation in the Northern Philippines
Authors: Racoma Bernard Alan , Klingaman Nicholas , Holloway Christopher , Schiemann Reinhard , Bagtasa Gerry
Published: March 2021

The Philippines is exposed to Tropical Cyclones (TCs) throughout the year due to its location in the western North Pacific. While these TCs provide much-needed precipitation for the country’s hydrological cycle, extreme precipitation from TCs may also cause damaging hazards such as floods and landslides. This study examines the relationship between TC extreme precipitation and TC characteristics, including movement speed, intensity, and season, for westward-moving TCs crossing Luzon, northern Philippines. We measure extreme precipitation by the Weighted Precipitation Exceedance (WPE), calculated against a 95th percentile threshold, which considers both the magnitude and spatial extent of TC-related extreme precipitation.

WPE has a significant, moderate positive relationship with TC intensity and a significant, weak negative relationship with TC movement speed. When TCs are classified by pre-landfall intensity, Typhoons (1-minute maximum sustained wind speed > 64 knots) tend to yield higher WPE than non-Typhoons (< 64 knots). On the other hand, when TCs are classified by pre-landfall speed, Slow TCs (movement speed < 11.38 knots) tend to yield higher WPE than Fast TCs (movement speed > 11.38 knots). However, while distributions of WPE are similar between the Southwest Monsoon (June-September) and Northeast Monsoon (October-December) seasons, the relationship between pre-landfall TC intensity and WPE is more pronounced during June-September. These results suggest that it is important to consider the pre-landfall cyclone movement speed, intensity, and season to anticipate extreme precipitation of incoming TCs. A decision table considering these factors is devised to aid in TC extreme precipitation forecasting.
Development and Evaluation of In-Flight Icing Index Forecast for Aviation
Authors: Morcrette Cyril , Bennett Katie , Bowyer Rebecca , Gill Philip , Suri Dan
Published: March 2021

Hindcasts from the United Kingdom Met Office weather model are used as inputs to an in-flight icing index from the literature. This index uses information about model-predicted temperature, relative humidity, vertical velocity and cloud liquid water content. Parts of the icing index formulation are then modified slightly, in the light of comparisons between hindcast model data and ground-based remote sensing observations. Firstly, the link to relative humidity is replaced with a link to model-predicted cloud cover. Secondly, although super-cooled liquid water icing is due to cloud condensate in the liquid phase, the model may not always correctly partition its condensate into the correct phase. So the second modification is to consider all condensate irrespective of phase when calculating the icing index. The skill of the original and new index are then assessed quantitatively against satellite-derived icing potential. We show that the new indices have substantially better reliability than the operational index used up until recently. Finally, we present a case study, when icing was reported, and discuss ways of presenting the likelihood and severity information.
A long-term geophysical and astronomical dataset: sunspot counting from 1610 to 2021
Authors: Vaquero José M.
Published: March 2021

Solar activity is an essential factor for the study of many aspects of the geophysical and astronomical sciences. A very simple measure of solar activity is counting sunspots using telescopes. This task can be done even with small telescopes since the Sun is apparently a very large and luminous star. For this reason, it is possible to rescue the ancient observations of sunspots made in the past centuries to obtain an image of the evolution of solar activity during the last four centuries.

The first attempt to reconstruct solar activity from these records was made by Rudolf Wolf, who defined the Sunspot Number index in the 19th century. The Zurich Observatory (and later the Brussels Observatory) was in charge of continuing Wolf's work to the present day. In 1998, Hoyt and Schatten presented a new reconstruction of solar activity that was very different from Wolf's reconstruction (Vaquero and Vázquez, 2009). Many of these differences were solved by Clette et al. (2014).

Currently, research to improve the Sunspot Number is focused on (i) improving the database by reviewing old observations, and (ii) improving the methodologies to convert raw data into the Sunspot Number index. In this work, we try to present the latest advances in this task (Muñoz-Jaramillo and Vaquero, 2019; Arlt and Vaquero, 2020).

 

References

Arlt, R., Vaquero, J.M. (2020) Living Reviews in Solar Physics 17, 1.

Clette, F. et al. (2014) Space Science Reviews 186, 35.

Muñoz-Jaramillo, A., Vaquero, J.M. (2019) Nature Astronomy 3, 205.

Vaquero, J.M. and Vázquez, M. (2009) The Sun recorded through history (Springer).
The magnetospheric interactions of predicted ULF wave power
Authors: Bentley Sarah , Thompson Rhys , Watt Clare , Stout Jennifer , Bloch Teo
Published: March 2021

We present and analyse a freely-available model of the power found in ultra-low frequency waves (ULF, 1-15 mHz) throughout Earth’s magnetosphere. Predictions can be used to test our understanding of magnetospheric dynamics, while accurate models of these waves are required to characterise the energisation and transport of radiation belt electrons in space weather.

This model is constructed using decision tree ensembles, which iteratively partition the given parameter space into variable size bins. Wave power is determined by physical driving parameters (e.g. solar wind properties) and spatial parameters of interest (magnetic local time MLT, magnetic latitude and frequency). As a parameterised model, there is no guarantee that individual physical processes can be extracted and analysed. However, by iteratively considering smaller scale driving processes, we identify predominant wave drivers and find that solar wind driving of ULF waves are moderated by internal magnetospheric conditions. Significant remaining uncertainty occurs with mild solar wind driving, suggesting that the internal state of the magnetosphere should be included in future.

Models such as this may be used to create global magnetospheric “maps” of predicted wave power which may then be used to create radial diffusion coefficients determining the effect of ULF waves on radiation belt electrons.
Establishment of a network of soil moisture and cosmic ray neutron sensors for data assimilation and optimization of high-resolution, real-time predictions
Authors: Ney Patrizia , Belleflamme Alexandre , Iakunin Maksim , Wagner Niklas , Bathiany Sebastian , Pfeifer Susanne , El Zohbi Juliane , Rechid Diana , Görgen Klaus , Bogena Heye
Published: March 2021

Climate change and its impacts at local scales, such as the more frequent occurrence of extreme weather events like droughts or floods, pose an increasing problem for agriculture. Our aim is to support farmers with soil condition and weather forecasting products that provide the basis for optimal adaptation to short-term weather variability and extremes as well as to long-term, regional climate change.

For this purpose, a prototypical monitoring and real-time forecasting system was established. The monitoring networks consist of a novel cosmic ray neutron sensor (Styx Neutronica), soil moisture and temperature sensors in four depths between 5 and 60 cm (SoilNet) and an all-in-one weather station (ATMOS-41, METER Environment) to measure the atmospheric conditions including air temperature, humidity, pressure, solar irradiance, wind speed and precipitation at 2 meter height above ground. The observation data are transmitted in real time to a cloud server via the cellular solution NBIoT (Narrow Band Internet of Things). After data post-processing the meteorological and hydrological parameters measured on site are directly assimilated into the fully coupled multi-physical numerical model system TSMP (Terrestrial Systems Modeling Platform, www.terrsysmp.org) at Forschungszentrum Jülich. ParFlow hydrologic model (www.parflow.org) is used in combination with the Community Land Model (CLM) to predict hourly, high-resolution (near plot level) information on soil moisture or other soil and meteorological parameters for the next 10 days. A special feature here is the prediction on the temporal development of plant-available water between 0-60cm depth for the sites of our monitoring network partners.

Observation data as well as the forecasting products are published in near real time on the digital product platform www.adapter-projekt.de. Users thus have direct access to relevant information that support them in planning agricultural management, e.g. irrigation and fertilization requirements, trafficability or workability.
Links between interannual climate variability and marine ecosystems in the Tropical Atlantic
Authors: Sanchez Emilia , Martin Rey Marta , Seferian Roland , Santana-Falcon Yeray
Published: March 2021

The interannual climate variability in the Tropical Atlantic is mainly controlled by two air-sea coupled modes denoted as Meridional Mode (MM) and Equatorial Mode (EM). The MM, peaking in boreal spring, is characterized by an anomalous Sea Surface Temperature (SST) interhemispheric gradient associated with anomalous surface cross-equatorial winds blowing to the warmer hemisphere.  On the other hand, the positive phase of the EM exhibits an anomalous warming in the equatorial band and along the African coast, related to a weakening of the climatological trade winds. Both interannual modes illustrate significant SST and surface wind changes in the eastern boundary upwelling systems (EBUS) of the tropical Atlantic: the Senegal-Mauritanian and Angola-Benguela. The EBUS are characterized by wind-induced coastal upwelling of deep cold waters rich in nutrients supporting high primary productivity and an abundance of food resources. Hence, the physical or climate characteristics associated with the MM and EM may have a potential effect on marine organisms and ecosystems. The goal of this study is to understand the links between the main modes of tropical Atlantic variability and biogeochemical (BGC) variables such as oxygen, net primary production and ph. These are known to be the main drivers for marine ecosystems. Firstly we study the influence of MM and AM on the EBUS and how these links are represented by the coupled ESM CNRM-ESM2.1 against observations. Second, we use the ESM to investigate the links between the SST anomalies associated to MM and EM and the main BGC stressors mentioned above. For this purpose, a set of numerical experiments performed with CMIP6 climate models are used. This work is supported by the H2020 TRIATLAS project, whose main goal is to understand and evaluate the future evolution of living marine resources in the Atlantic Ocean.
Ranking Icelandic volcanoes by threat and prioritizing their monitoring requirements 
Authors: Barsotti Sara , Parks Michelle , Melissa Pfeffer , Jónsdóttir Kristín , Vogfjorð Kristín , Ófeigsson Benedikt
Published: March 2021

How well are our volcanoes monitored? When and why should we review and enhance the monitoring setup for volcano surveillance? These questions are often raised at Volcano Observatories or at those Institutions in charge of monitoring volcanoes and their associated hazards. The Icelandic Meteorological Office (IMO) is responsible for monitoring natural hazards in Iceland, including volcanoes and volcanic eruptions. IMO operates an extended multidisciplinary monitoring network which comprises seismometers, cGPS, gas sensors, MultiGAS and DOASes, hydrological stations, strainmeters and tiltmeters, infrasound networks and webcams, with the aim of detecting in a timely manner potential unrest at any of the 32 active volcanoes in the country. Limited resources and funding opportunities often pose limitations on how extensive (in terms of number of sensors and their variety) a volcano monitoring network can be. Therefore, the Volcano Observatories are often required to decide how to prioritize the monitoring needs and find a balance in sensitivity, reliability, and efficacy of the network.  

In this contribution, we will present the results of the analysis performed at the IMO to rank the Icelandic active volcanoes by their threat and, consequently, to prioritize their monitoring needs. Some criteria (based on eruption frequency, potential hazards, infrastructure exposure and current status) are defined as guidelines and they are used to drive decisions regarding when and how to alter the monitoring setup. The specific case of Hekla volcano is used here to evaluate the validity of such criteria and to perform an analysis of the current capability of issuing a timely warning for one of the most dangerous volcanoes in Iceland. 
First data for abundance diagnostics with SPICE, the EUV spectrometer on-board Solar Orbiter
Authors: Zambrana Prado Natalia , Buchlin Éric , Peter Hardi ,   SPICE consortium team
Published: March 2021

Linking solar activity on the surface and in the corona to the heliosphere is one of Solar Orbiter’s main goals. Its EUV spectrometer SPICE (SPectral Imaging of the Coronal Environment) will provide relative abundance measurements which will be key in this quest, as different structures on the Sun have different abundances as a consequence of the FIP (First Ionization Potential) effect. From the 16th to the 22nd of November 2020,  the Solar Orbiter remote sensing checkout window STP-122 was carried out. During this period of observations, SPICE was lucky to catch a small AR in its field of view. We carried out abundance specific observations in order to provide relative FIP bias measurements with SPICE. Furthermore, data from other types of observations carried out during that same week allow us to identify the spectral lines that could be used for abundance diagnostics. We take the SPICE instrument characteristics into account to give recommendations regarding the types of studies to carry out to obtain such abundance measurements.
Recent surge of the South Rimo Glacier, Karakoram: Dynamics Characterization using SAR data
Authors: Li Shiyi , Bernhard Philipp , Hajnsek Irena , Leinss Silvan
Published: March 2021

Glacier surging is an unique dynamic pattern that involves a long term quiescent phase and a sudden surge phase. The surge causes abnormal glacier movement, such as high flow velocity, transportation of large amount of ice mass, and dramatic thickening and advancing of the glacier terminus. Glacier surge not only confound the understanding of regional glacier dynamics, but also pose threats to local residents by invoking glacier lake outburst floods. 

In this work, we reported the recent surge event of the South Rimo Glacier, one of the largest glaciers in Karakorum. The surge happened between 2018-2020 with very little terminus advancement, and thus it is difficult to interpret the dynamics of the event simply by visual inspections of satellite images. We studied both the topography evolution and the surface velocity change of the glacier before and during the surge. By differencing a series of digital elevation models (DEMs) produced from the TanDEM-x CoSSC data acquired between 2011 and 2017, we found that the South Rimo glacier started accumulating height in the middle stream since 2013. A bulge was built in the reservoir region since 2014 and reached its maximum height (27.51m higher than 2011) before the surge activation in 2017. Velocity maps between 2016-2020 were obtained from SAR offset tracking using Sentinel-1 images. It was shown that the surface velocity greatly increased in 2017 at areas around the bulge. The peak velocity was found in the mid of 2019 at about 10 m/day, which is of three magnitude higher than the velocity during the quiescent phase. Our work characterized the development of the recent surge of the South Rimo Glacier, and highlighted the value of high resolution DEM products and velocity maps in pre-identifying glacier surge and mitigating related hazards.
Geophysical response to dissolution of undisturbed and fractured evaporite rock during brine flow
Authors: Dale Michael Stanley , Falcon-Suarez Ismael , Marín-Moreno Hector
Published: March 2021

Dissolution of halite rock can significantly impact underground constructions (e.g., caverns for energy storage and abandoned caverns) and above ground constructions (e.g., highways and buildings) potentially causing a threat to human life from land subsidence and sinkhole hazards, instability to underground construction and pollutant release. In this work, we explore and quantify changes in elastic and hydromechanical properties during dissolution of halite rock by migration of water.

We evaluated the impact of dissolution on the geophysical properties of pristine (non-fractured) and fractured halite samples (with ~2.7% dolomite), using a synthetic (seawater-like) brine solution (3.5wt% NaCl). The dissolution test commenced by setting an initial effective pressure of 15 MPa (with minimum pore pressure of 0.1 MPa), equivalent to a depth of ~720 m below ground level. This confining pressure of 14.9 MPa ensured the adequate contact between sample and the ultrasonic instrumentation (P- and S-wave sensors), and the set of electrodes for electrical resistivity. The test procedure was set to investigate the effect of increasing pore pressure from 0.1 to 14 MPa on dissolution. This procedure was only successful for the non-fractured sample, as dissolution rapidly occurred in the fractured sample during the initial stage of the test.

The non-fractured halite shows that P-wave velocity increases with increasing inlet pore pressure initially, followed by a lower pore fluid sensitivity stage. After this stage, the P-wave and the Vp/Vs ratio reduce and then ultrasonic velocities tend to their original values when effective pressure tends to zero. These results suggest that capillary pressure effects are initially increasing the bulk properties of the rock by filling the micro-pores, while dissolution is occurring locally, nearby the inlet-flow port, and therefore invisible to our geophysical tools. The small porosity fraction of 1.1% allows the saturating fluid to rapidly equilibrate with the surrounding halite within the pores, slowing down the dissolution process. In a close halite system with a local and continuous brine supply source, local dissolution may allow pressure increase up to the overburden stress and affect the geomechanical integrity of the reservoir by a combined fracturing-dissolution process.
Visualization of uncertainty in air quality ensemble forecasts
Authors: Heil Angelika , Colette Augustin
Published: March 2021

Air quality forecasts help decision-makers to respond to air pollution episodes and to improve air quality management. In recent years, the public increasingly uses mobile apps to check forecasted air pollution levels and then adjusts outdoor activities accordingly. For Europe, state-of-the-art daily air quality forecasts are provided by the regional Copernicus Atmosphere Monitoring System (CAMS). The system integrates forecasts from 9 individual models. This ensemble approach not only achieves better predictive performance compared to a single model, but also allows a better quantification of forecast uncertainty. How to best communicate this uncertainty to a broad audience is by no means a trivial task, but yet essential to maintain trust in the forecasts.

We developed innovative visualizations to convey CAMS forecast uncertainties in time series and maps. The development is strongly user-driven and involves iterative consultation with a wide range of expert and non-expert users. We investigate the feasibility of different bivariate techniques to communicate the ensemble's best estimate and its uncertainty in a single map. We explore user preferences for a variety of time-series graphs, including boxplots, violinplots, and fancharts. Whilst preferences are largely driven by the data and visualization literacy of the users, we identify some generally valid best practices in terms of graph types, choices of colors and labels, and accompanying textual explanations. Finally, we present our candidate designs for the public display of air quality forecasts on the regional CAMS webpage.
The Digital Earth Viewer: A new visualization approach for geospatial time series data
Authors: Buck Valentin , Stäbler Flemming , Gonzalez Everardo , Greinert Jens
Published: March 2021

The study of the earth’s systems depends on a large amount of observations from homogeneous sources, which are usually scattered around time and space and are tightly intercorrelated to each other. The understanding of said systems depends on the ability to access diverse data types and contextualize them in a global setting suitable for their exploration. While the collection of environmental data has seen an enormous increase over the last couple of decades, the development of software solutions necessary to integrate observations across disciplines seems to be lagging behind. To deal with this issue, we developed the Digital Earth Viewer: a new program to access, combine, and display geospatial data from multiple sources over time.

Choosing a new approach, the software displays space in true 3D and treats time and time ranges as true dimensions. This allows users to navigate observations across spatio-temporal scales and combine data sources with each other as well as with meta-properties such as quality flags. In this way, the Digital Earth Viewer supports the generation of insight from data and the identification of observational gaps across compartments.

Developed as a hybrid application, it may be used both in-situ as a local installation to explore and contextualize new data, as well as in a hosted context to present curated data to a wider audience.

In this work, we present this software to the community, show its strengths and weaknesses, give insight into the development process and talk about extending and adapting the software to custom usecases.
Reaction kinetics of OH radicals with glutaric acid and adipic acid in the aqueous phase
Authors: Wen Liang , Schaefer Thomas , Herrmann Hartmut
Published: March 2021

Dicarboxylic acids (DCAs) are widely distributed in atmospheric aerosols and cloud droplets and are mainly formed by the oxidation of volatile organic compounds (VOCs). For example, glutaric acid and adipic acid are two kinds of the DCAs that can be oxidized by hydroxyl radical (‧OH) reactions in the aqueous phase of aerosols and droplets. In the present study, the temperature- and pH-dependent rate constants of the aqueous OH radical reactions of the two DCAs were investigated by a laser flash photolysis-long path absorption setup using the competition kinetics method. Based on speciation calculations, the OH radical reaction rate constants of the fully protonated (H2A), deprotonated (HA-) and fully deprotonated (A2-) forms of the two DCAs were determined. The following Arrhenius expressions for the T-dependency of the OH radical reaction of glutaric acid, k(T, H2A) = (3.9 ± 0.1) × 1010 × exp[(-1270 ± 200 K)/T], k(T, HA-) = (2.3 ± 0.1) × 1011 × exp[(-1660 ± 190 K)/T], k(T, A2-) = (1.4 ± 0.1) × 1011 × exp[(-1400 ± 170 K)/T] and adipic acid, k(T, H2A) = (7.5 ± 0.2) × 1010 × exp[(-1210 ± 170 K)/T], k(T, HA-) = (9.5 ± 0.3) × 1010 × exp[(-1200 ± 200 K)/T], k(T, A2-) = (8.7 ± 0.2) × 1010 × exp[(-1100 ± 170 K)/T] (in unit of L mol-1 s-1) were derived.

The energy barriers of the H-atom abstractions were simulated by the Density Functional Theory calculations run with the GAUSSIAN package using the M06-2X method and the basis set m062x/6-311++g(3df,2p). The results showed that the energy barriers were lower at the Cβ-atoms and are higher at the Cα-atoms of the two DCAs, clearly suggesting that the H-atom abstractions occurred predominately at the Cβ-atoms. In addition, the ionizations can enhance the electrostatic effects of the carboxyl groups, significantly reducing the energy barriers, leading to the order of OH radical reactivity as  <  < . This study intends to better characterize the losing processes of glutaric acid and adipic acid in atmospheres.
Drivers of midlatitude extreme heat waves revealed by analogues and machine learning
Authors: Miloshevich George , Lucente Dario , Herbert Corentin , Bouchet Freddy
Published: March 2021

One of the big challenges today is to appropriately describe heat waves, which are relevant due to their impact on human society. Common characteristics in mid-latitudes involve meanders of the westerly flow and concomitant large anticyclonic anomalies of the geopotential field. These anomalies form the so-called teleconnection patterns, and thus it is natural to ask how robust such structures are in various models and how much data we require to make statistically significant inferences. In addition, it is natural to ask what are the precursor phenomena that would improve forecasting capabilities of the heat waves. In particular, what kind of long term effect does the soil moisture have and how it compares to the respective quantitative contribution to the predictability of the teleconnection patterns.

 

In order to answer these questions we perform various types of regression on a climate model. We construct the composite maps of the geopotential height at 500 hPa and estimate return times of heatwaves of different severity. Of particular interest to us is a committor function, which is essentially a probability a heat wave occurs given the current state of the system. Committor functions can be efficiently computed using the analogue method, which involves learning a Markov chain that produces synthetic trajectories from the real trajectories. Alternatively they can be estimated using machine learning approach. Finally we compare the composite maps in real dynamics to the ones generated by the Markov chain and observe how well the rare events are sampled, for instance to allow extending the return time plots.
Integration of operational Multi-Hazard Early Warning Systems and COVID-19 data for the humanitarian community
Authors: Proietti Chiara , Annunziato Alessandro , Probst Pamela , Paris Stefano , Peter Thomas
Published: March 2021

To improve preparedness and response in case of large-scale disasters, the international humanitarian community needs to understand the anticipated impact of an event as soon as possible in order to take informed operational decisions. The European Commission’s Joint Research Centre (JRC), DG ECHO, and the United Nations’ OCHA and UNOSAT launched the Global Disaster Alert and Coordination System (www.GDACS.org) in 2002-03 as cooperation platform to provide early disaster warning and coordination services to humanitarian actors. After more than 15 years, GDACS has around 30k registered users among humanitarian organisations at global level.

At the beginning, one of GDACS’s main tasks was the dissemination of automatic alerts for earthquakes, tsunamis and tropical cyclones; today, the system has been augmented to include also floods, droughts and volcanoes, and it will soon include forest fires.  Alerts are sent to the international humanitarian community to ensure timely warning in severe events that are expected to require international assistance. Alert levels are determined by automated algorithms without, or with very limited, human intervention, using automatic real-time data-feeds from various scientific institutes or the JRC’s own systems.

From 2020, because of the potential impact of the COVID-19 emergency on international preparedness and response activities, the COVID-19 situation in affected countries is now also monitored by the system, providing real time information updates on the website. This new feature allows to consider in the planning of the emergency response, the severity of the outbreak in the affected countries.

This contribution presents the challenges and outcomes of combining science-based information from different independent systems into a single Multi-Hazard Early Warning System and introduces new functionalities that were recently developed to address the new challenges related to the COVID-19 emergency.
Rule-based modelling for adaptive complex infrastructure planning
Authors: Erfani Tohid , Harou Julien J.
Published: March 2021

Dealing with uncertainty in infrastructure planning is a challenge. Planning decisions need to be made in face of unknown future condition, and, in the meantime, it is essential that they are flexible enough to be adapted as new information unfolds. This indeed is important for multi-sector decision making where the complexity of the interconnected system and the uncertainty thereof hinders the modelling and analysis. Multistage stochastic optimisation provides a mechanism to incorporate these two attributes into planning decisions. However, its expensive computation as well as the appropriateness of its sequential decisions beyond the first few stages reduce its implementability. We introduce `Decision Rule' as a way to approximate the multistage problem, where the decisions at each stage are functions of the system complexity and the future uncertainty. We introduce a family of linear, polynomial, conditional if-then based rules and show how they approximate the multistage stochastic problem. We investigate their implications for urban water demand and supply network planning problem. Further we discuss some state-of-the-art and emerging tools for increasing the accuracy of the rules.
Dynamical and thermodynamical contributions to the mid-latitude atmospheric response to Arctic sea ice decline
Authors: Chripko Svenya , Msadek Rym , Sanchez-Gomez Emilia , Terray Laurent , Bessières Laurent , Moine Marie-Pierre
Published: March 2021

Previous climate model studies have shown that Arctic sea ice decline can solely affect weather and climate at lower latitudes during the cold season. However, the mechanisms beneath this linkage are poorly understood. Whether sea ice loss have had an influence on the lower latitudes climate over the past decades is also uncertain (Barnes and Screen 2015). The goal of this work is to better understand the relative contributions of dyncamical and thermodynamical changes in the atmospheric response to Arctic sea ice loss, which have been suggested to oppose each other (Screen 2017). We conducted two sets of sensitivity transient experiments that allow to isolate the effect of Arctic sea ice decline on the mid-latitudes from other climate forcings, using the climate model CNRM-CM6 (Voldoire et al. 2019) in a coupled configuration or with an atmosphere-only. The first set of experiments, that is part of the European H2020 PRIMAVERA project, consists of a 100-member ensemble in which sea ice albedo is reduced to the ocean value (PERT) in the fully coupled CNRM-CM6, and which is compared to a 1950 control run (CTL) (Haarsma et al. 2016). This yields idealised ice-free conditions in summer and a more moderate sea ice reduction during the following months. The second set of experiments, that is part of the CMIP6 Polar Amplification Model Intercomparison Project (PAMIP, Smith et al. 2019), consists of a 300-member ensemble in which the atmospheric component of CNRM-CM6 is forced by sea ice anomalies associated with a future 2°C warming (FUT) and present day sea surface temperatures (SSTs). These are compared to experiments in which the atmosphere is forced by present-day sea ice conditions (PD) and the same SSTs. To extract the dynamical component of the response in the two sets of experiments, we use a dynamical adjustment method (Deser et al. 2016) based on a regional reconstruction of circulation analogs. We focus on three mid-latitudes regions in which a significant near-surface temperature response has been identified, namely North America, Europe and central Asia. We show that the cooling occurring over central Asia in both sets of experiments is dynamically-induced through an intensification of the Siberian High, and that opposed temperature responses over North America between the two sets of experiments could be explained by opposed dynamical components occurring in response to the imposed Arctic sea ice decline. Finally, we discuss whether different dynamical and thermodynamical contributions in the PAMIP multi-model experiments could explain the multi-model differences in the atmospheric response to sea ice loss.
Response of the surface climate to different land surface models: WRF sensitivity to surface model options
Authors: Lima Daniela C.A. , Cardoso Rita M. , Soares Pedro M.M.
Published: March 2021

The Weather Research and Forecasting (WRF) model version 4.2 includes different land surface schemes, allowing a better representation of the land surface processes. Four simulations with the WRF model differing in land surface models and options were investigated as a sensitivity study over the European domain. These experiments span from 2004-2006 with a one-month spin-up and were performed at 0.11o horizontal resolution with 50 vertical levels, following the CORDEX guidelines. The lateral boundary conditions were driven by ERA5 reanalysis from European Centre for Medium-Range Weather Forecasts. For the first experiment, the Noah land surface model was used. For the remaining simulations, the Noah-MP (multi-physics) land surface model was used with different runoff and groundwater options: (1) original surface and subsurface runoff (free drainage), (2) TOPMODEL with groundwater and (3) Miguez-Macho & Fan groundwater scheme. The physical parameterizations options are the same for all simulations. These experiments allow the analysis of the sensitivity of different land surface options and to understand how the representation of land surface processes impacts on the atmosphere properties. This study focusses on the investigation of land-atmosphere feedbacks trough the analysis of the soil moisture – temperature and soil moisture – precipitation interactions, latent and sensible heat fluxes, and moisture fluxes. The influence of different surface model options on atmospheric boundary layer is also explored.

Acknowledgements. The authors wish to acknowledge the LEADING (PTDC/CTA-MET/28914/2017) project funded by FCT. The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – Instituto Dom Luiz.
K indices and K-derived magnetic activity indices:  context’s reminder
Authors: Chambodut Aude
Published: March 2021

The K index was devised by Bartels et al. (1939) to provide an objective monitoring of irregular geomagnetic activity at subauroral latitudes. K indices are based upon geomagnetic disturbances, measured in horizontal geomagnetic components at magnetic observatories, after « eliminating » the regular daily variation. An individual K index is an integer in the range 0 to 9 corresponding to a class that contains the largest range of geomagnetic disturbances (in either of the two horizontal components) during a 3-hour UT interval. Limits of range vary from one observatory to another since they depend on the corrected geomagnetic latitude of the observatory.

A great number of Space Weather applications rely on K-derived magnetic activity indices at subauroral latitudes. These historical indices; endorsed by IAGA such as Kp, aa and am; represent unprecedented homogeneous time series, up to more than 150 years, highly valuable for all studies related to long-term geomagnetic activity.

However, one has to keep in mind that local K indices and subauroral related ones (K-derived) were developed during other time, under specific societal and technological conditions.

We recall the local K indices derivation processes and characteristics to enlight possible nowadays drawbacks and their simple mitigations.