bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Machine Learning for spatio-temporal mapping of the air temperature in Warsaw
Authors: Hassani Amirhossein , Castell Núria , Schneider Philipp
Published: March 2022

Mapping the spatio-temporal distribution of near-surface urban air temperature is crucial to our understanding of climate-sensitive epidemiology, indoor-outdoor thermal comfort, urban biodiversity, and interactive impacts of climate change and urbanity. Urban-scale decision-making in face of future climatic uncertainties requires detailed information on near-surface air temperature at high spatio-temporal resolutions. However, reaching such fine resolutions cannot be currently realised by traditional observation networks, or even by regional or global climate models (Hamdi et al. 2020). Given the complexity of the processes affecting air temperature at the urban scale to the regional scale, here we apply Machine Learning (ML) algorithms, in particular, XGBoost gradient boosting method to build predictive models of near surface air temperature (Ta at 2-meter height). These predictive models establish data-driven relations between crowd-sourced measured Ta (data produced by citizens’ sensors) and a set of spatial and spatio-temporal predictors, primarily derived from Earth Observation satellite data including Modis Aqua/Landsat 8 Land Surface Temperature (LST), Modis Terra vegetative indices, and Sentinel-2 water vapour product. We use our models to predict sub-daily (at Modis Aqua satellite passing times) variation in urban scale Ta in city of Warsaw, Poland at spatial resolution of 1 km for the months July-September and the years 2016 to 2021. A 10-fold cross-validation of the developed models shows a root mean square error between 0.97 and 1.02 °C and a coefficient of determination between 0.96 and 0.98, which are satisfactory according to the literature (Taheri-Shahraiyni and Sodoudi 2017). The resulting maps allow us to identify regions of Warsaw that are vulnerable to heat stress. The strength of the method used here is that it can be easily replicated in other EU cities to achieve high resolution maps due to the accessibility and open-sourced nature of the training and predictor data. Contingent on data availability, the predictive framework developed also can be used for monitoring and downscaling of other urban governing climatic parameters such as relative humidity in the context of future climate uncertainties.

Hamdi, R., H. Kusaka, Q.-V. Doan, P. Cai, H. He, G. Luo, W. Kuang, S. Caluwaerts, F. Duchêne, B. J. E. S. Van Schaeybroek and Environment (2020). "The state-of-the-art of urban climate change modeling and observations." 1-16.

Taheri-Shahraiyni, H. and S. J. T. S. Sodoudi (2017). "High-resolution air temperature mapping in urban areas: A review on different modelling techniques."  21(6 Part A): 2267-2286.
Climate change signal in global agriculture emerges earlier in new generation of climate and crop models
Authors: Jägermeyr Jonas , Müller Christoph ,   GGCMI Team
Published: March 2022

Potential climate-related impacts on future crop yield are a major societal concern first surveyed in a harmonized multi-model effort in 2014. We report here on new 21st-century projections using ensembles of latest-generation crop and climate models. Results suggest markedly more pessimistic yield responses for maize, soybean, and rice compared to the original ensemble. Mean end-of-century maize productivity is shifted from +5 to -6% (SSP126) and +1 to -24% (SSP585) — explained by warmer climate projections and improved crop model sensitivities. In contrast, wheat shows stronger gains (+9 shifted to +18%, SSP585), linked to higher CO2 concentrations and expanded high-latitude gains. The ‘emergence’ of climate impacts — when the change signal emerges from the noise — consistently occurs earlier in the new projections for several main producing regions before 2040. While future yield estimates remain uncertain, these results suggest that major breadbasket regions will face distinct anthropogenic climatic risks sooner than previously anticipated.
An Improved shear velocity model beneath the Iranian plateau using adjoint noise tomography
Authors: komeazi Abolfazl , Kaviani Ayoub , Yaminifard Farzam , Rümpker Georg
Published: March 2022

We perform an adjoint waveform tomography using Rayleigh-wave empirical Green‘s functions (EGFs) at periods 10-50 s to improve a pre-existing 3-D velocity model of the crust and uppermost mantle beneath the Iranian plateau. The starting model was derived from a conventional surface-wave dispersion tomography based on high-frequency ray-theory assumption to invert of a quasi-3-D shear-wave velocity model. We use the EGFs from the same study that were derived from cross correlation of continuous seismic noise. Adjoint tomography refines the initial model by iteratively minimizing the frequency-dependent travel-time misfits between synthetic and observed EGFs measured in different period bands. Our new model covers the known tectonic units such as the Central Iranian Block, Zagros fold-and-thrust belt, Sanandaj-Sirjan metamorphic zone and Urumieh-Dokhtar magmatic arc.

Overall, the adjoint tomography provides images with better lateral resolution and depth sensitivity and more realistic absolute velocity values due to the inclusion of finite-frequency waveforms. The use the numerical spectral-element solver in adjoint tomography provides accurate structural sensitivity kernels, which helps to obtain more robust images rather than those generated by ray-theory tomography. The final model adjusts the shapes of velocity anomalies at crustal depth more specifically for the eastern Zagros. The final model significantly improves the initial model at the upper mantle depths and provides a higher resolution for the shape of velocity anomalies.
Will future noctilucent clouds affect Earth's albedo?
Authors: Lübken Franz-Josef , Baumgarten Gerd , Grygalashvyly Mykhaylo , Vellalassery Ashique
Published: March 2022

Noctilucent clouds (NLC) are often cited as potential indicators of climate change in the middle atmosphere. They owe their existence to the very cold summer mesopause region (~130K) at mid and high latitudes. We analyze trends derived from the Leibniz-Institute Middle Atmosphere Model (LIMA) and the MIMAS ice particle model (Mesospheric Ice Microphysics And tranSport model). We first concentrate on the years 1871-2008 and on middle, high and arctic latitudes, respectively. Model runs with and without an increase of carbon dioxide and water vapor (from methane oxidation) concentration are performed. Trends are most prominent after ~1960 when the increase of both carbon dioxide and water vapor accelerates. Negative trends of (geometric) NLC altitudes are primarily due to cooling below NLC altitudes caused by carbon dioxide increase. Increases of ice particle radii and NLC brightness with time are mainly caused by an enhancement of water vapor caused by the oxidation of methane. Several ice layer and background parameter trends are similar at high and arctic latitudes but are substantially smaller at middle latitudes. Ice particles are present nearly all the time at high and arctic latitudes, but are much less common at middle latitudes. Ice water content and maximum backscatter are highly correlated, where the slope depends on latitude. This allows to combine data sets from satellites and lidars. Furthermore, IWC and the concentration of water vapor at the altitude of maximum backscatter are also strongly correlated. Results from LIMA/MIMAS are consistent with observations. More recently, we have expanded our model runs into the future, namely up to the 2060s. We have used IPCC scenarios regarding future concentrations of carbon dioxide and methane. We find that all NLC parameters, such as occurrence rates and backscatter coefficients increase substantially in this time period. Furthermore, we have studied the extinction of solar radiation by NLC. We will present details regarding the (wavelength-dependent) extinction and the temporal and spatial distribution of this extinction. We will also present new results on the impact of solar cycle induced radiation variability on NLC.
North Atlantic cooling is slowing down mass loss of Icelandic glaciers
Authors: Noël Brice , Aðalgeirsdóttir Guðfinna , Pálsson Finnur , Wouters Bert , Lhermitte Stef , Haacker Jan M. , van den Broeke Michiel R.
Published: March 2022

Icelandic glaciers have been losing mass since the Little Ice Age in the mid-to-late 1800s, with higher mass loss rates in the early 21st century, followed by a slowdown since 2011. As of yet, it remains unclear whether this mass loss slowdown will persist in the future. By reconstructing the contemporary (1958-2019) surface mass balance of Icelandic glaciers, we show that the post-2011 mass loss slowdown coincides with the development of the Blue Blob, an area of regional cooling in the North Atlantic Ocean to the south of Greenland. This regional cooling signal mitigates atmospheric warming in Iceland since 2011, in turn decreasing glacier mass loss through reduced meltwater runoff. In a future high-end warming scenario, North Atlantic cooling is projected to mitigate mass loss of Icelandic glaciers until the mid-2050s. High mass loss rates resume thereafter as the regional cooling signal weakens. 
Rock slope dynamics in flysch formation under cold climate (part 1) : rock cracking and failure mechanism
Authors: Gauthier Francis , Birien Tom , Meloche Francis
Published: March 2022

Rockfalls are major natural hazards for road users and infrastructures in northern Gaspésie (Eastern Canada). In the last 30 years, more than 17 500 rockfalls have reached the two major road servicing the area. Rockfalls come from 10 to 100 m high flysch rockwall conducive to differential weathering. The retreat and settlement of weak rock strata (shale, siltstone) causes the gradual cantilevering of stronger rock strata (sandstone, greywacke), contributing to the development of tension cracks. The block, separated from the cliff, will eventually slide or topple on the eroding rock strata. These dynamics have been observed, but rarely studied with the objective of 1) determining the mechanical stresses and weathering conditions that promote rock cracking and 2) identifying the geometric conditions that control the final failure mode. We use the cantilever beam theory to model critical cantilever length (block size) and rock tensile strength. A frost cracking model (Rempel et al., 2016) was then used to explain the overestimation of the critical cantilever length and to verify whether the development of microfractures caused by frost damage can explain the decrease of the rock tensile strength over time. The results show that the areas of frost damage concentration correspond to those of maximum stress in the overhanging blocks. In order to identify the type of failure of these blocks, tests using a tilting table were carried out in laboratory. 405 tests were performed on 10 blocks characterized by different roughness coefficients and geometric ratios (height / length ratio, overhang length / total length of the block). The results, validated on natural blocks in the field, were used to identify the geometric conditions for stability, sliding, and toppling failure of overhanging block on an inclined plane. Such stability criteria could support the development of rock instability detection algorithm using high resolution 3D model.
The Black Sea rifting phase in the Cretaceous and implications for the evolution of the Black Sea lithosphere
Authors: Stephenson Randell , Stovba Sergiy
Published: March 2022

The Black Sea is a deep marine basin formed by lithosphere extension and active rifting in a Tethyan back-arc tectonic setting in the Cretaceous, which by general consensus is taken to represent the main process forming the present-day basin (although significant post-rift deformation has occurred). Rifting took place within continental lithosphere that had earlier been accreted to and, by this time, formed part of the Eurasian lithospheric plate. The present-day crust is thin though the lithosphere appears to be of typical thickness. A much-debated issue about the Black Sea is whether Cretaceous rifting was intense enough to have led to oceanic or “sub-oceanic” crust formation prior to the deposition of the overlying thick Cretaceous and younger sedimentary succession. This is the focus of the present multidisciplinary study, which integrates detailed subsurface mapping in the Ukrainian sector of the northern Black Sea with regional geophysical characterisations of the lithosphere and the record of pre-Cretaceous Tethyan belt geology of the area. These allow new quantitative basin modelling that strongly suggests that Cretaceous rifting was insufficient to reveal exhumed continental mantle or to promote ocean crust formation. Legacy extensional tectonic events affecting the area in pre-Cretaceous times are inferred to be important for explaining the observed present-day crustal and lithosphere architecture of the Black Sea area. The results are likely relevant to the formation and eventual consumption of back-arc basins in the Tethyan orogenic belt generally.
The RiskChanges tool for multi-hazard risk-informed planning at local government level
Authors: van Westen Cees , Hazarika Manzul , Dahal Ashok , Kshetri Tek , Shakya Anish , Nashrrullah Syams
Published: March 2022

Local governments are faced with increasing levels of risk from extreme hydro-meteorological events such as (tropical) storms,  flooding, landslides, drought, heatwaves, wildfires, etc. The frequency and interaction of these events, also in combination with other events that do not have a direct climate driver, makes that it is likely that many areas are faced with higher impacts from compounding events. Global trends such as population growth, urbanization, increased dependency on technology also contributed to larger exposure and vulnerability. In order to plan for future developments, and for reducing the increasing levels of risk, local governments require to plan ahead and evaluate the options available for reducing the risk under future scenarios. For this task Spatial Decision Support Systems are required that allow local governments to make informed decisions, considering the current and future levels of risk. RiskChanges is a Spatial Decision Support System for the analysis of current and future multi-hazard risk at a local level, in order to analyze optimal risk reduction alternatives. The system is developed by the University of Twente in collaboration with the Asian Institute of Technology, GeoInformatics Centre. RiskChanges ( http://www.riskchanges.org/ ) is an Open-Source, web-based tool, based on a series of python scripts, which are integrated into a Graphical User Interface. The tool includes several major features: multi-hazard, multiple assets, a vulnerability curve database, multi-user approach, comparison of risk, and spatial analysis. Users can upload their own datasets (in the form of hazard maps, elements-at-risk maps, administrative unit maps, and vulnerability curves). The tool contains an open-source vulnerability curve database, allowing to sharing of physical vulnerability curves among users. Multiple users can collaborate on the same project, and provide different input data. The multi-hazard feature allows performing the risk assessment for multiple natural and manmade hazard interactions. Exposure and vulnerability are combined in a loss calculation for each combination of element-at-risk and hazard. Loss maps are integrated into a risk map, where the user indicates the interaction between the hazard types. The system allows to analyze the risk of multiple asset types with different spatial characteristics.  Users can compare the risk for the current situation and future scenarios and/or planning alternatives.  
Understanding multiscale drivers of natural hazards, cascading failures, and risk management strategies within a multisector system
Authors: Talchabhadel Rocky , Sharma Sanjib , Kumar Saurav
Published: March 2022

Deleterious impacts of rapid unplanned anthropogenic disturbances have been compounded by climate change globally. This phenomenon is particularly prominent in the high mountain regions that have suffered a string of cascading hazard-related disasters (CHDs). Recent catastrophic events (e.g., 2013 Uttarakhand Flood, 2021 Chamoli Landslide, and 2021 Melamchi Debris/Flood) have highlighted the need to better understand the complex interactions among human, natural, and engineered systems to inform the design of disaster management strategies. It is crucial to rethink disaster management as a multisystem-connected problem. In such a deeply interconnected system, it is essential to build a systematic framework to reveal linkages and identify spatially and temporally varying risk probabilities. We develop data-driven models that integrate existing hydroclimatic models (e.g., glacial lake outburst flood, landslide, and flood) and data (e.g., NASA Earth Observations) with non-traditional data streams (e.g., Citizen Science and expert knowledge) to investigate connections that lead to CHDs.

Our modeling framework synergistically integrates models and data from different systems using a Bayesian network. The framework will serve as an operational system-of-systems model for the high mountain region that can formalize how Citizen Science and expert knowledge may be utilized with existing models for managing CHDs. Here the experts refer to everyone involved in decision-making, including academic researchers, public agency researchers, policymakers, and managers on the ground. We propose that a cyberinfrastructure should be developed that integrates all data streams and model resources necessary to understand the spatially and temporally varying risks. The cyberinfrastructure will facilitate ‘what-if’ type analysis to understand system dynamics and sensitivity to perturbations that may be used to design mitigation strategies.

 

Case Study

Specifically, we choose Nepal Himalaya where natural hazards and cascading failure are a major concern. The region is characterized by extreme elevation gradient, young and fragile geology, extreme seasonal and spatial variation in rainfall, and diverse human impacts. One hazard often triggers another hazard in the region, leading to cascading disaster. Also, a seemingly non-hazardous series of average events can trigger a chain of events over a long or short time-scale with disastrous consequences. Knowledge and understanding of these connections are essential for planning mitigation measures and improving hazards predictions in the region.
Thermospheric density variation and its response to Joule heating during geomagnetic storms
Authors: Wang Xin , Liu Siqing , Miao Juan , Lu Xian , Aa Ercha , Luo Binxian
Published: March 2022

Thermospheric density is essential for the calculation of atmospheric drag, which is the main cause of the orbit decay for low-Earth-orbit (LEO) satellites. During geomagnetic storms, the Joule heating has a strong impact on neutral mass density. In this work, we statistically investigate 265 geomagnetic storms to explore the response of thermospheric density to Joule heating from 2002 to 2008. We obtain the density enhancements from Challenging Minisatellite Payload (CHAMP) and the Gravity Recovery and Climate Experiment (GRACE) satellites, and we also calculate Joule heating from the Defense Meteorological Satellite Program (DMSP) spacecraft and the Weimer electric potential model. The results show that the thermospheric density delays Joule heating during geomagnetic storms. The time lag is about 0-2 hrs during weak and moderate storms, while it is 3-5 hrs for intense storms. In addition, Joule heating can affect the density enhancement at higher latitude regions. The latitudinal difference between thermospheric density and Joule heating is about 0°-10° during weak and moderate geomagnetic storms, while it increases to 10°-15° for intense storms. Besides, we use the temporal relationship of thermospheric density with geomagnetic activity indices and Joule heating as calibration for the NRLMSISE-00 model during geomagnetic storms. The calibrated NRLMSISE-00 model results can better simulate the storm-time thermospheric density, with the Mean Relative Error (MRE) between observation and model decreasing from 40% to 10%.
A unified model for wind-blown volcanic umbrella clouds
Authors: Millward Frank , Johnson Chris
Published: March 2022

Explosive volcanic eruptions release a rising plume of ash and gas into the atmosphere. Once such a plume reaches its altitude of neutral buoyancy, it spreads into an umbrella cloud, which is then distorted by the surrounding meteorological wind. At least four processes are important in governing the complex evolution of the umbrella cloud: buoyancy-driven spreading, turbulent skin drag, inertial drag at the advancing edge of the cloud, and the momentum of the cloud. Existing models have frequently assumed that just one of these drag forces is dominant. Here we present a model for the spread of an umbrella cloud in a crosswind, which is based on time-dependent partial differential equations that include all four key processes. The model confirms that spread far downstream is driven by a balance between turbulent drag and buoyancy. By including all four processes the transient behaviour of the cloud that occurs upwind of the drag-buoyancy regime can also be investigated. Our findings illustrate the fundamental differences between wind-blown umbrella clouds and those derived from an axisymmetric umbrella cloud approximation, and the consequent importance of accurate physical descriptions of the interaction between wind and umbrella clouds in volcanic ash dispersal models.
Legacy effects and cascading impacts of climate extremes on ecosystems
Authors: Bastos Ana , Yu Xin , de Brito Mariana M.
Published: March 2022

Climate extremes impact ecosystems directly by imposing stress conditions and impairing normal functioning. Depending on its severity, recovery from a given event can take several years to decades, which results in compounding effects of recurrent extremes in time. Climate extremes can also have indirect impacts on ecosystems e.g., by increasing the hazard of concurrent disturbances, such as fires or insect outbreaks. The increased frequency or intensity of climate extremes due to anthropogenic climate change has, therefore, the potential to increase the likelihood of impact cascades.

Understanding the processes controlling ecosystem responses to and recovery from extreme events, and how temporally and/or spatially compounding events affect ecosystem dynamics is crucial to anticipate potential threats to ecosystem stability under a changing climate. Here, we will discuss challenges in quantifying direct and lagged impacts of extreme events on ecosystem functioning and present recent studies trying to overcome these challenges based on recent historical events. Finally, we will identify key needs in observations and methods to improve understanding on cascading ecological impacts from more frequent extreme events.
Surface Heterogeneity Measure and Its Application in Energy Imbalance Problem
Authors: Kadum Hawwa , Wanner Luise , Mauder Matthias
Published: March 2022

The Earth's surface continuously interacts with the atmospheric boundary layer (ABL) through turbulent fluxes.  These fluxes are responsible for the transfer of energy, momentum, and matter. In consequence, land-atmosphere feedback is controlled by the surface structure.  Assuming surface homogeneity in scientific practices causes problems like inaccuracy in atmospheric models predictions and underestimations in eddy-covariance (EC) measurements.  One challenge of accounting for surface heterogeneity in scientific practices is the lack of a practical measure of heterogeneity length scales.  We propose here a lacunarity based heterogeneity scale that is validated using experimental forest models.  For mitigating the energy imbalance problem in EC measurements, it was found that the flux underestimation can be parameterized as a function of atmospheric stability and surface heterogeneity.  We investigate the applicability of the heterogeneity scale to this parameterization for the underestimations in CO2 fluxes.
Erosional dynamics of a river driven by groundwater seepage
Authors: Vulliet Marie , Lajeunesse Eric , Neufeld Jerome A.
Published: March 2022

Seepage erosion occurs when groundwater emerges at the surface of a granular heap. A

spring forms and feeds a river which entrains sediments, thus changing the groundwater

flow.

 

We reproduce this phenomenon in the laboratory using a quasi-2D aquifer filled with glass

beads, by imposing a water level at one end of the pile. Water flows through the aquifer and

emerges at the surface of the granular bed. For large enough water levels this river erodes

its bed and the spring progressively ascends the heap. We investigate its trajectory, the

evolution of the groundwater discharge and the river depth. Intriguingly, we find that after an

initial erosive period the river attains a new equilibrium profile, with an elevated spring.

 

We model the flow in the aquifer using Darcy's law, predicting the shape of the water table,

the position of the spring and the groundwater discharge. By applying Coulomb’s frictional

law to the forces experienced by a grain we predict a threshold for the onset of erosion as a

function of reservoir height and aquifer length. This prediction provides a dynamical theory

for the erosional dynamics of the river. Our combined theoretical and experimental approach

thereby helps constrain the response of an idealized erosive river-catchment system to

steady forcing.
Integrating transpiration and xylem water stable isotopes in a process-based model to determine transpiration and discharge age distributions
Authors: Fresne Maëlle , Chun Kwok Pan , Fabiani Ginevra , Hrachowitz Markus , McGuire Kevin , Moussa Adnan , Schoppach Remy , Klaus Julian
Published: March 2022

Transpiration is an important component of the catchment water balance, and tree water uptake can significantly influence discharge dynamic and travel times. Tree usually use water of a different age than the water that generates discharge. Most hydrological models that track water age rely on discharge and stream water isotopes data for calibration. This calibrated age-tracking model enables to simulate time-variant discharge travel times. However, transpiration and related water isotopes data are rarely integrated. We currently lack understanding on the age distribution of transpiration and how discharge travel times relate to this age distribution. In this context, the objectives of this work are to 1) analyse spatio-temporal patterns of xylem water isotopes, 2) determine transpiration age distribution and investigate its temporal dynamic over two growing seasons and 3) evaluate how discharge travel times respond to changes in the transpiration age distribution. We determined the spatial controls on xylem water isotopes (δ18O and δ2H) and simulated travel times in discharge and transpiration in a forested catchment in Luxembourg. We used a lumped, process-based catchment model for water fluxes and tracer transport based on storage-age selection functions. Using discharge, transpiration, stream and xylem water δ2H measurements, the model was calibrated over a period of three years (October 2017-September 2020) by means of a Monte Carlo optimization and a multi-objectives approach. Preliminary results indicate that tree species and diameter are the main drivers of xylem water isotopes variation. Vegetation controls are especially dominant during a drier growing season while landscape variables (hillslope position, topographical position index, flow accumulation) appear to also control xylem water δ2H in wetter conditions. Investigations of transpiration and discharge age distributions will help to better understand how tree water uptake influences discharge travel times over the growing seasons. The spatial analysis of xylem water isotopes further provides a foundation for investigating the spatial variability of the transpiration age distribution. This study will also profit in assessing the value of transpiration and associated isotopes data for discharge travel times simulations and improving our current model representations of hydrological processes in forested catchments.
Tropical cyclone genesis potential in CMIP6 climate models
Authors: Cavicchia Leone , Ascenso Guido , Scoccimarro Enrico , Castelletti Andrea , Giuliani Matteo , Gualdi Silvio
Published: March 2022

Tropical cyclones (TCs) are regularly listed among the costliest natural disasters, due to the associated strong wind, heavy precipitation, and risk of storm surges. Therefore, being able to understand and predict TC activity at different time scales would lead to clear societal and economic benefits.

Several genesis potential indices (GPIs) have been introduced in the literature, linking TC activity to favourable conditions in a number of large-scale meteo-climatic variables. The advantage of using such indices lies in the ability to study TC occurrence in climate model simulations, which do not usually reproduce individual TC accurately due to the limited horizontal resolution.

Existing GPIs generally have good skill in reproducing the spatial pattern and seasonal cycle of historical TC activity. On the other hand, they commonly fail to reproduce TC interannual variability across different ocean basins. A further issue is found for climate projections where, for those climate models with high-enough resolution to allow for TC tracking, the trends of GPI and directly detected cyclones are often in disagreement.

Here we revisit the issue of TC genesis potential in reproducing TC activity by exploiting the last generation of climate model simulations, obtained from the CMIP6 model intercomparison project. Using data obtained from both the ScenarioMIP and HighResMIP simulations, we investigate the effect of horizontal resolution and other model features on the modelled GPI’s skill in reproducing TC interannual variability and trends.
Assessing physical vulnerability to wildfire: a Physical Vulnerability Index (PVI) for buildings
Authors: Papathoma-Koehle Maria , Garlichs Celine , Schlögl Matthias , Mavroulis Spyridon , Diakakis Michalis , Fuchs Sven
Published: March 2022

Recent wildfire events (e.g. Mediterranean region, USA, and Australia) showed that this hazard poses a serious threat for wildland-urban interface (WUI) areas around the globe. Furthermore, recent events in regions where wildfire does not constitute a frequent hazard (e.g. European Alps, Siberia, Scandinavia) indicated that the spatial pattern of wildfire risk might have significantly changed. To prepare for upcoming extreme events, it is critical for decision-makers not only to have a thorough understanding of fire ignition, propagation, and associated forecasting and modelling, but also of the vulnerability of the built environment to wildfire. Building quality and design standards are important not only because building loss is costly but also because robust buildings may offer shelter when evacuation is not possible. However, studies aiming at the analysis of wildfire vulnerability for the built environment are limited so far.

The present contribution focuses on the development of a Physical Vulnerability Index (PVI) for buildings subject to wildfire, that considers different building characteristics and their surroundings and uses weighting based on statistical methods. Data from a recent and systematically documented wildfire event in Greece are used to select and weigh the relevant indicators using the random-forest-based all-relevant feature selection algorithm Boruta. One of the main advantages of the method is its predictive capacity and the ability, once established, to indicate houses with great damage potential in areas susceptible to wildfires in the future. The PVI for buildings subject to wildfire may be used in other places in Europe and beyond by decision-makers giving an overview of the vulnerability of buildings at the local level, supporting in this way evacuation planning. Furthermore, it can be the basis for local adaptation measures and reinforcement of buildings that can support shelter-in-place.
Some reflections on Eric Wood’s career
Authors: Lettenmaier Dennis
Published: March 2022

I will reflect on some of Eric’s major accomplishments, and my own experiences from having worked with him for over 40 years.  This will go back to our first professional meeting, at a meeting of the AGU Committee on Network Design in the late 1970s.  It will also include early consulting work, including Love Canal in particular, his leave at the (then) UK Institute of Hydrology in 1984, and work with the late James R Wallis.  I will focus especially on development of the Variable Infiltration Capacity (VIC) model starting in the early 1990s, and its many applications by his group over the last two plus decades.  I’ll finish with reflections on his approach to hydrologic research, and some messages our younger colleagues can take away from his life and contributions.
Imaging potential geothermal resources in the Hengill volcanic area (Iceland) with active-source seismics recorded by a dense nodal array 
Authors: Gyger Lea , Sánchez-Pastor Pilar , Maurer Hansruedi , Obermann Anne , Wiemer Stefan
Published: March 2022

The Hengill area, located a few km west of Reykjavik, is situated on the triple junction of three large geological features: the onshore section of the Mid-Atlantic Ridge, called the Reykjanes Peninsula Oblique Rift, the Western Volcanic Zone and the South Iceland Seismic Zone. This area hosts two large-scale geothermal power plants, Nesjavellir and Hellisheiði. Both are producing electricity and hot water. Hengill is also one of the targets of the Iceland Deep Drilling Project that aims at finding and exploiting supercritical fluids.

In summer 2021, a nodal network of 500 5 Hz geophones was deployed in the area over a period of 2 months. It complemented seismic data from a network of broadband stations that were already deployed earlier. In July 2021, a vibroseis experiment was conducted in the area in form of two surveys performed by a fully electrical seismic vibrator truck.  The seismic waveforms were recorded by parts of the nodal network. In this study, we focus on the survey conducted along the road leading to the Nesjavellir geothermal power plant, in Mosfellsheiði. The aim of the survey in Mosfellsheiði is to obtain new insights on a low-velocity anomaly as well as on a yet poorly understood seismic cluster that has been detected in the area by previous studies.

To study the velocity and attenuation structure of the area, we computed a first arrival travel time tomography and an attenuation profile. Finally, we compared our results with an existing 3D seismic ambient noise tomography Vs model of the area as well as with known local subsurface properties, such as resistivity and mineralogy.

The final results of this vibroseis study could be useful for finding new geothermal resources in the Nesjavellir area.
The Physically-Based Extreme Value (PHEV) distribution of river discharges
Authors: Basso Stefano , Botter Gianluca , Merz Ralf , Miniussi Arianna
Published: March 2022

Reliable assessment of the flooding hazard of river basins is crucial for many social and economic activities. We present here the Physically-based Extreme Value (PHEV) distribution of river discharges. PHEV is a process-based alternative to empirical estimates and statistical methods hitherto used to characterize extremes of hydrometeorological variables. It arises from a description of key hydro-meteorological processes driving runoff production (e.g., precipitation inputs, evapotranspiration rates, soil moisture states and catchment responses) through solution of the master equation for the probability distribution of streamflow in a catchment. PHEV pairs physical understanding of the mechanisms producing extreme events and defining their chance of occurrence with an easily tractable mathematical descriptions of them, thus providing a theoretical underpinning to the study of manifold flood-related issues, such as the emergence of heavy tails in streamflow and flood distributions, flood rich and poor periods, and the reasons leading to the occurrence of extreme flood events.

In this work we benchmark capabilities of PHEV for predicting odds and magnitudes of floods against a standard distribution and the latest statistical approach for extreme estimation. The methods are first applied to an extensive dataset to compare their skills for predicting observed flood quantiles in a wide range of case studies. Synthetic time series of streamflow, generated for select river basins from contrasting hydro-climatic regions, are later used to assess performances for rare events. The analyses outline the domain of applicability of PHEV and reveal less biased capabilities to estimate flood magnitudes with return periods much longer than the sample size used for calibration. Results also show reduced prediction uncertainty of PHEV for rare floods, notably if the flood magnitude-frequency curve displays an inflection point.

Such discontinuities typically hinder estimation of high streamflow quantiles. PHEV reveals itself as a reliable tool to foresee their occurrence in a large set of case studies from the US and Germany, also when using shortened data series where the highest observations were removed. Case studies for which PHEV predicts the occurrence of an inflection point which is not visible in the empirical flood magnitude-frequency curve mostly belong to river flow regimes characterized by values weakly oscillating around their mean, which rarely exhibit extreme flow values by their nature. The limited length of the available data series might be thus constraining the possibility to observe extreme floods that shall be expected. These results indicate the possibility to reliably appraise the propensity of rivers to generate extreme floods by means of a process-based description of watershed dynamics, thus laying the foundation for a better comprehension of their physio-climatic controls.
Heat flow in the cores of Earth, Mercury and Venus from resistivity experiments on Fe-Ni-Si
Authors: berrada meryem , Secco Richard , Yong Wenjun
Published: March 2022

Recent theoretical studies have tried to constrain internal structure and composition of Earth, Mercury and Venus using thermal evolution models. In this work, the adiabatic heat flow at the top of the core was estimated using the electronic component of thermal conductivity (kel), a lower bound for thermal conductivity. Direct measurements of electrical resistivity (ρ) of Fe-10wt%Ni-wt%Si at core conditions can be related to kel using the Wiedemann-Franz law. Measurements were carried out in a 3000 ton multi-anvil press using a 4-wire method. The integrity of the samples at high pressures and temperatures was confirmed with electron-microprobe analysis of quenched samples at various conditions. Measurements of ρ at melting seem to remain constant at 135 µΩcm and 141 µΩcm on the solid and liquid sides of the melting boundary. The heat flow at the top of Earth’s CMB is greatly influenced by the light element content in the core. Interpolation of the measured thermal conductivity from this study with high pressure data from the literature suggest the addition of 10-16 wt%Ni and 3-10wt%Si in Earth core results in a heat flow of 6.8 TW at the top of the core. In Mercury, the presence of a thermally stratified layer of Fe-S at the top of an Fe-rich core has been suggested, which implies a sub-adiabatic heat flow on the core side of the CMB. The calculated adiabatic heat flux at the top of Mercury’s core suggests a sub-adiabatic from 0.09-0.21 Gyr after formation, which suggest a chemically driven magnetic field after this transition. Also, the heat flow in Mercury’s interior is estimated to increase by 67% from the inner core to outer core. It has been proposed that an Earth-like core structure for Venus is only compatible with the current lack of dynamo if Venus’ core thermal conductivity is 100 Wm−1K−1 or more. The thermal conductivity at Venus’ core conditions is estimated to range from 44-51 Wm−1K−1, in agreement with scenarios of a completely solidified core.
Simulated warm water access to the Amundsen Sea continental shelf
Authors: Silvano Alessandro , Holland Paul , Naughten Kaitlin , Dragomir Oana , Dutrieux Pierre , Jenkins Adrian , Si Yidongfang , Stewart Andrew , Peña-Molino Beatriz , Naveira Garabato Alberto
Published: March 2022

The West Antarctic Ice Sheet is losing mass at an accelerating rate, contributing to sea level rise. Ocean forcing is considered to be the main driver of this mass loss, associated with warm intrusions of Circumpolar Deep Water onto the continental shelf. Here we describe these intrusions, focussing on the role of the Amundsen Undercurrent. The Amundsen Undercurrent is an eastward, bottom-intensified current located at the shelf break/upper slope that transports warm Circumpolar Deep Water. This current enters the continental shelf through deep canyons that connect the shelf break with ice shelf cavities, bringing oceanic heat to the base of the ice shelves. We use a regional ocean model to introduce the forcing mechanisms of the Amundsen Undercurrent and the drivers of its temporal variability. We conclude by discussing how this variability ultimately influences melting of ice shelves in the Amundsen Sea.
Geomorphic change as a driver of flood risk in a tropical gravel bed river
Authors: Quick Laura , Williams Richard , Boothroyd Richard , Hoey Trevor , Tolentino Pamela , Guardian Esmael , Reyes Migo , Sabilo Catherine
Published: March 2022

River morphology results from sediment transport and deposition, which are both a consequence of water flow. Episodic variation in natural (e.g. typhoons, earthquakes, volcanoes) and anthropogenic (e.g. gravel mining, river bank protection) sediment supply drives changes in riverbed levels and planform morphology of rivers. These geomorphic changes determine channel capacity and flow routing, and thus associated flood risk to surrounding people and property.

Despite the significance of variation in riverbed levels and channel position for flood risk, geomorphological processes are commonly overlooked in flood risk mapping. Tropical gravel bed rivers, like those observed in the Philippines, are particularly dynamic; flood risks arising from sedimentation and erosion should be assessed and incorporated into flood risk management to mitigate the impact of flooding on welfare and the economy.

Here we use new high resolution (0.5 m) repeat topographic surveys from 2014, 2019 and 2020 of the Bislak River in northwest Luzon Island to quantify annual and multi-year sediment budgets (i.e. erosion and deposition) and geomorphic change over single and multiple wet seasons.

Changes in flood risk related to geomorphic change (natural and anthropogenic) is tested using repeat two-dimensional hydraulic modelling to see whether observed geomorphic changes result in altered discharge routing and flood inundation extent in the region.
On the plane wave perspective of the tropospheric Kelvin waves
Authors: Shaaban Ahmed , Roundy Paul
Published: March 2022

Two separate dynamics have been used to understand the vertical structure of the Kelvin waves. Stratospheric Kelvin waves have been interpreted in terms of plane gravity waves, where the waves pump their energy upward. On the other hand, the characteristics of the tropospheric Kelvin waves have been interpreted as a superposition between low orders (mostly the first and second) baroclinic modes, which are expected under the hypothesis that the tropopause acts as a rigid lid. We used Fourier transformation to isolate the dynamical fields of the ERA-I reanalysis field into upward and downward phase components. Then, wavelet-based indices have been used to target wavenumber four Kelvin waves centered over the Indian ocean at different phase speeds. We found that the upward-energy waves are settled in the stratosphere, while the downward-energy waves are in the troposphere indicating that the tropospheric Kelvin waves at a single wavenumber behave as plane gravity wave-like their counterpart in the stratosphere. The upward-energy waves in the troposphere were found to follow the structure of the plane Kelvin waves with the zonal wind is in phase with the geopotential height, out of phase with upward wind, and in quadrature with the temperature field.
A model set-up for future scenario simulations in the northwest European shelf
Authors: Pradhan Himansu Kesari , Daewal Ute , Grayek Sebastian , Staneva Joanna , Schrum Corinna
Published: March 2022

A coupled physical-ecosystem modelling set-up is designed in the framework of GCOAST (Geesthacht Coupled cOAstal model SysTem) to study the ecosystem in the NorthWest European shelf (NWES). Physical model NEMO (Nucleus for European Modelling of the Ocean) is coupled with ECOSMO (ECOSystem MOdel). ECOSMO is a NPDZ (Nutrients, Phytoplankton, Detritus, Zooplankton) model that simulates 3 phytoplankton groups and 3 nutrient cycles. The domain includes Baltic Sea- North Sea and northeast part of Atlantic Ocean bearing ~3.6 km resolution. Physical model forcings include temperature & salinity from WOA data, tides from OTIS and wind from ERA5 datasets, whereas for ecosystem, nutrients (from WOA), and river nutrient load. Unique characteristics to the domain are low-saline brackish water, longer water-cycle memory, and sea ice coverage in the Baltic Sea. The North Sea is relatively saline with shallower depths. This domain extends to eastern North Atlantic that encloses a broader shelf-slope region. Anthropogenic drivers like, river nutrient loads, wind turbines, trawling, shipping, etc constantly modify the coastal waters of the domain. This motivates us to study the region for hindcast and future scenario simulations. Initial experiments are conducted for studying the skill of the set-up. Model validation metrics showed that the simulation has skill in matching a large data set of in situ observations (from ICES and HELCOM datasets) for ecosystem and physical variables. Time series validation of temperature, salinity, and nutrients shows the seasonality and the general characteristics of the ecosystem. The model set-up reproduces cyanobacterial blooms in Baltic Sea; higher primary and secondary production at the shelf-slope, Norwegian trench, and coastal regions of North Sea; tidal mixing fronts in the North Sea, etc. Planned experiments are a hindcast (1992-2017) and Representative Concentration Pathway (RCP8.5) simulation (1992-2050).