bluuebunny/crossref_metadata_2025 huggingface dataset:
A globally-applicable framework for compound flood risk modeling
Authors: Eilander Dirk , Couasnon Anaïs , Winsemius Hessel C. , Muis Sanne , Dullaart Job , Leijnse Tim , Ward Philip J.
Published: March 2022

Low-lying coastal deltas are prone to floods as these areas are often densely populated and face flooding from fluvial (discharge), coastal (surge and waves) and pluvial (rainfall) drivers. If these drivers co-occur, they can cause or exacerbate flooding, and are referred to as compound flood events. Most compound flood studies have either investigated the statistical dependence between drivers or used hydrodynamic models to assess the physical interactions between drivers, but few have combined both aspects to examine extreme flood levels for e.g. risk assessments. Furthermore, hydrodynamic compound flood models are often setup at a local scale, require many person hours to set up and are based on local data, making these hard to scale up. Hence, the need for globally-applicable compound flood risk modelling remains. 

We developed a globally-applicable framework for compound flood risk modelling. It consists of a local hydrodynamic SFINCS model which is automatically set up based on global datasets after several processing steps and loosely coupled to global models using HydroMT (https://deltares.github.io/hydromt_sfincs/latest/). We applied to the Sofala province of Mozambique where we validated it for two historical tropical cyclone events and used it for a compound flood risk analysis. For the validation, we compared flood extents from the global and local flood models with observed flood extents from remote sensing. Our analysis shows that the local model, while based on the same data, has a higher accuracy compared to the global model. This is due to a more complete representation of flood processes and an increased spatial resolution. We also analyzed the compound flood dynamics and show that the areas where water levels are amplified by interactions between flood drivers vary significantly between events. Finally, we also calculated the compound flood risk from fluvial, pluvial and coastal drivers based on a large stochastic event set of plausible (compound) flood conditions derived from ~40 years of reanalysis data. We find that coastal flood drivers cause the largest risk in the region despite a more widespread fluvial and pluvial flood hazard as most exposure is affected by elevated sea levels. Flood risk increases when accounting for the observed dependence between flood drivers compared to independence and this difference is mainly attributed to events with large return periods. Since the model setup and coupling is automated, reproducible, and globally-applicable, the presented framework offers a way forward towards large scale compound flood risk modelling. 
Regional Aerosol Model Intercomparison Project 
Authors: Wilcox Laura , Allen Robert , Bauer Susanne , Bollasina Massimo , Ekman Annica , Keeble James , Lewinschal Anna , Lund Marianne , Merikanto Joonas , O'Donnell Declan , Paynter David , Persad Geeta , Rumbold Steven , Samset Bjørn , Takemura Toshihiko , Tsigaridis Kostas , Undorf Sabine , Westervelt Daniel
Published: March 2022

The uncertainty in aerosol radiative forcing is currently the largest source of uncertainty in estimates of the magnitude of the total anthropogenic forcing on climate, and changes in aerosol emissions are likely important for regional climate over the next few decades. This is especially the case for Africa and Asia where large aerosol emission changes are anticipated, and where aerosol has played an important role in historical changes. Uncertainty in near-term projections due to the substantial spread in aerosol (or their precursor) emissions pathways is compounded by uncertainty in the simulated response to these emissions, so a multi-model framework is needed to identify robust changes.  

Several earlier studies have explored the climate response to regional aerosol perturbations, with interesting, but not always consistent, results. Using these studies to inform our understanding of the potential role of aerosol in near-future changes is not straightforward. Many are based around equilibrium experiments that are challenging to use to interpret transient simulations, and the effects of different experimental designs are difficult to separate from the effects of structural differences between the models. In Regional Aerosol MIP, we will perform a set of transient experiments based on emissions from the Shared Socioeconomic Pathways. Regional Aerosol MIP will better enable us to assess the potential contribution of aerosol to near-future climate change, to describe the robust features of the response to regional aerosol changes, and to identify where the key uncertainties lie. In this presentation we will introduce the experiment design, alongside some early analysis.
Do soil microbes adapt to warming?
Authors: Moinet Gabriel , Dhami Manpreet , Hunt John , Podolyan Anastasija , Liáng Liyĭn , Schipper Louis , Whitehead David , Nuñez Jonathan , Nacente Adriano , Millard Peter
Published: March 2022

Climate warming may be exacerbated if rising temperatures stimulate losses of soil carbon to the atmosphere. Despite a plethora of studies stimulated by this alarming perspective, the direction and magnitude of this so-called carbon-climate feedback remain uncertain. Part of the uncertainty is due to lack of knowledge of the thermal adaptation of the physiology and composition of soil microbial communities. Here, we tested the hypothesis that microbial communities adapt to long-term warming with a shift in their composition and their temperature response that are consistent with evolutionary theory. We used the unique combination of state-of-the-art macromolecular rate theory (MMRT) to describe the temperature response of microbial respiration and metabarcoding to characterise the microbial community composition of soils sampled along transects of increasing distance from a geothermally active zone in New Zealand. Along those transects, the mean annual temperature of the soil increased dramatically (by up to 15oC), and this concurred with shifts in microbial communities composition, with thermophile and thermotolerant genera increasing in relative abundance with increasing ambient temperature. However, the ambient temperature had no detectable influence on the MMRT parameters or the relative temperature sensitivity of decomposition (Q10). MMRT parameters were, however, strongly correlated with soil carbon concentration and carbon:nitrogen ratio. Our findings suggest that, while long-term warming selects for warm-adapted taxa, substrate quality and quantity exert a stronger influence than temperature in selecting for distinct thermal traits. The results have major implications for our understanding of the role of soil microbial processes in the long-term effects of climate warming on soil carbon dynamics and will help increase confidence carbon-climate feedback projections.
Electron cyclotron maser model of solar radio zebras
Authors: Benáček Jan , Karlický Marian
Published: March 2022

Solar radio zebras, occurring as fine structures in radiograms during Type IV bursts, are an excellent tool for plasma diagnostics during solar flares. The main model of zebras is the electron cyclotron maser instability based on double plasma resonance between electron cyclotron and plasma frequencies and an unstable wave in the presence of an unstable type of velocity distribution is necessary, e.g., a loss-cone. The radio emission occurs in the electromagnetic Z-mode along the magnetic field or at the first harmonic of the X-mode in the perpendicular direction. However, it is still unclear where and how the instability evolves and how the locally captured electrostatic waves are converted to escaping radio waves. To obtain the instability evolution, we calculated its growth rates and saturation energies as functions of cyclotron-to-plasma frequency ratio, loss-cone density, cold background  temperature, hot electron thermal velocity, and loss-cone angle by using analytical calculations and particle-in-cell simulations. We found that the growth rates and saturation energies form maxima, approximately located at the harmonic numbers of cyclotron frequency. The maxima shift to lower frequencies with increasing the plasma temperature, they broaden and decrease with increasing the harmonic number. We also estimated electromagnetic energy densities in the emission region and the conversion efficiency to the radio waves.
Extreme drought or heavy rainfall drives plant-soil feedbacks of range-shifting and congeneric native plant species
Authors: Li Keli , (G.F.) Veen Ciska , A. Harvey Jeffrey , H. van der Putten Wim
Published: March 2022

One of the consequences of climate change is the frequency of extreme weather incidences, such as extreme drought or heavy rainfall increase. At the same time, climate warming enables certain plant species to expand to higher latitudes. The question is how the frequency of extreme drought or heavy rainfall affects plant-soil interactions of range-shifting plants in the new habitat compared to native residents. We conducted an outdoor mesocosm experiment to study how an extreme drought influenced biomass production of range-shifting and co-occurring congenetic native plant communities in the next year by plant-soil feedback. We found that in soils with a history of extreme drought range-shifting plants produced more shoot biomass. To explore mechanisms in more detail, we set up a greenhouse experiment to condition soils under extreme drought and heavy rainfall. Then, we tested plant-soil feedbacks using Centaurea jacea as native and Centaurea stoebe as range expander. Our results showed during soil conditioning under extreme drought the shoot biomass was decreased, and under extreme wet conditions was increased. This applied to both range expander and native species. At the same time, soil N, P, and K and soil microbial communities had changed in a different manner. Consequently, these soil biotic and abiotic changes might be the main drivers of negative, neutral, positive plant-soil feedbacks of range expanders and natives under extreme weather events, with an impact on plant quality changes and plant-associated herbivore responses. Thus, we show that climate change may influence both plant biomass and aboveground herbivory through altering plant-soil biota interactions.
Catchment memory explains hydrological drought forecast performance
Authors: Sutanto Samuel J. , Van Lanen Henny A. J.
Published: March 2022

Skillful Drought Early Warning Systems (DEWSs) to predict drought a few months in advance are of utmost importance to reduce the impacts of the drought hazard. Previous studies on meteorological drought forecasts e.g. using the standardized precipitation index (SPI) show that drought can be sufficiently predicted up to 1-3 months ahead. The skill of hydrological drought forecasts e.g. using the standardized runoff index (SRI) and standardized ground index (SGI), on the other hand, is even 2-3 months higher than the meteorological ones. The high skill in hydrological drought forecasts is anticipated coming from the catchment storage/memory (e.g. lakes, soils, groundwater) that pools, attenuates, and lengthens the effect of the driving forces (i.e. precipitation). Yet, the importance of catchment memory in explaining hydrological drought forecast performance has not been studied. Here, we have conducted a pioneering study that investigates the importance of catchment memory on the forecast performance of streamflow drought across Europe. We identified streamflow drought using the Standardized Streamflow Index (SSI). The observed and forecasted streamflow droughts at major European rivers were derived from the streamflow data obtained from the European Flood Alert System (EFAS) driven by observed and forecasted weather data. Catchment memory was derived from the Baseflow Index (BFI) and the groundwater Recession Coefficient (gRC), which through the streamflow, give information on the catchment memory. Performance of streamflow drought forecasts was evaluated using the Brier Score (BS) for rivers across Europe. Results show that the use of higher accumulation periods in the SSI (e.g. SSI-3) forecasts improves forecast performance. The performance is even higher for catchment that has large memory. We found that BS is negatively correlated with BFI, meaning that rivers with high BFI (large memory) yield better drought prediction (low BS). A significant positive correlation between gRC and BS demonstrates that catchments slowly releasing groundwater to streams (low gRC), i.e. large memory, generates higher drought forecast performance. The higher performance of hydrological drought forecasts in catchments with relatively large memory (high BFI and low gRC) implies that Drought Early Warning Systems have more potential to be implemented there and will appear to be more useful.
Quantum navigation with multi-axis atomic interferometry and hybrid 
Authors: Zou Yueyang , Abidi Mouine , Barbey Philipp , Rajagopalan Ashwin , Schubert Christian , Gersemann Matthias , Schlippert Dennis , Abend Sven , Rasel Ernst M.
Published: March 2022

Atomic interferometers use the interference of cold or ultra-cold matter waves and are a promising tool for high-precision inertial sensors. The principle of freedom from drift of such sensors is an interesting property for autonomous navigation. In this context, a compact geometry of differential atomic interferometers to differentiate between accelerations and rotation rates is demonstrated and a concept for a compact six-axis sensor is presented [1]. It is based on our experimental studies on atom-chip-based interferometry [2] in combination with atom-chip sources for a high flux of condensed atoms [3]. Hybrid approaches that implement a fusion with classic sensors can remove the limitations of previous quantum sensors in terms of data rate and bandwidth [4].

So far, various components of quantum navigation based on laboratory systems have been demonstrated and their application tested in controlled environments. Current projects and proposals aim to qualify the first sensors for field use. They rely on either commercially available sub-systems or, in some cases, custom-made products and integrate them into laboratory environments. We hereby present our preliminary system design with Bose-Einstein condensates (BECs) of 87Rb atoms for a transportable demonstrator aiming at a multi-axis inertial sensor, for the precise measurement of accelerations and rotation.

 

We acknowledge financial support from the Deutsche Forschungs-gemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy - EXC-2123 QuantumFrontiers - 390837967 and through the CRC 1227 (DQ-mat), as well as support from DLR with funds provided by the BMWi under grant no. DLR 50RK1957 (QGyro) and DLR 50NA2106 (QGyro+).

 

[1] M. Gersemann, et al. Eur. Phys. J. D, 74 10 203, 2020

[2] S. Abend et al., Phys. Rev. Lett. 117, 203003, 2016

[3] J. Rudolph et al., New J. Phys. 17, 065001, 2015.

[4] L.L. Richardson, et al. Commun. Phys. 3, 208, 2020
Bivariate sea-ice assimilation for Global Ocean Analysis/Reanalysis
Authors: Cipollone Andrea , Banerjee Deep Sankar , Aydogdu Ali , Iovino Doroteaciro , Masina Simona
Published: March 2022

Recent intercomparison studies among ocean/sea-ice Reanalyses (such as ORA-IP) have shown large discrepancies in many sea-ice-related fields, despite a rather general agreement in the sea-ice extension. The low accuracy of sea-ice thickness measurements together with the highly non-gaussian distributions of related uncertainty, made multivariate sea-ice data assimilation (DA) strategies still at an early stage, although nearly twenty years of thickness observations are now available. In a standard multivariate scheme, the break of Gaussianity can generate un-realistic corrections due to the poor linear relationship driven by the B matrix.

One approach to solve the problem is the implementation of anamorphous transformations that modify the probability density functions of ice anomalies into Gaussian ones (Brankart et al. 2012). In this study, a 3DVar DA scheme (called OceanVar), employed in the routinely production of global/regional ocean reanalysis CGLORS (Storto et al, 2016), has been recently extended to ingest sea-ice concentration (SIC) and thickness (SIT) data. An anamorphous operator, firstly developed and made freely available within the SANGOMA project (http://www.data-assimilation.net/), has been updated and adapted for the bivariate assimilation of SIC/SIT within the OceanVar framework.

We present the comparison among several sensitivity experiments that were performed assimilating different observation datasets and using different DA configurations at 1/4 degree global resolution. Specifically, we assess the impact of ingesting different SIT products, such as SMOS and CRYOSAT-2 data or the merged product CS2SMOS.

We show that the sole assimilation of SIC improves the spatial representation of SIT with respect to a free run. The inclusion of thickness correction, determined by empirical relations, appears to improve the sea ice characteristics in the Atlantic sector and degrade them in the Siberian region; therefore a refined tuning could probably be beneficial. The spatial error reduces sharply only once CRYOSAT-2 data are assimilated jointly with SIC data. In the present set up, all the experiments generally tend to overestimate the sea-ice volume in the case SMOS data are not assimilated. However, observational errors associated with SMOS data are generally too small, leading to jumps in the volume time series at the beginning of the accretion period if not calibrated correctly.

The proposed approach is suitable to be used for covarying ocean/sea-ice variables in future coupled ocean/sea-ice DA.

Storto, A. and Masina, S. (2016), Earth Syst. Sci. Data, 8, 679, doi: 0.5194/essd-8-679-2016

Brankart, et al. (2012), Ocean Sci., 8, 121, doi: 10.5194/os-8-121-2012

 
Dynamic modelling of a screw actuator for improved locomotion control on various terrains
Authors: Remmas Walid , Gkliva Roza , Ristolainen Asko
Published: March 2022

Different types of terrains can be encountered in mining environments, varying from hard rock bottom to mud, including gravel and sand. In our research we are investigating the usage of Archimedean screw actuators for locomotion in mining environments, as they are mechanically robust and can work on various substrates. The limitations on using screw locomotion in autonomous robotics include its inherent property of slippage that varies depending on the type of terrain. Moreover, the dynamic model of an Archimedean screw depends on variables such as shear stress or sinkage, which are difficult to measure with the onboard sensors. To accurately model and later control such robots, we focus on the dynamic modelling of the screw-ground interaction based on real experiments. In this work, we approximate the dynamics of an Archimedean screw to those of different tire models available in the literature. The proposed models are used to; (1) Simulate the ground-screw interaction with several types of grounds. (2) Estimate the robot pose based on odometry. (3) Design adaptive controllers able to control the robot in grounds with varying properties. We validate the proposed dynamic models based on experimental force measurements, and we evaluate the accuracy of the derived odometry models based on visually measured ground truth data.
Quantum-cascade laser absorption spectrometer (QCLAS) for balloon-borne measurements of UTLS water vapor 
Authors: Brunamonti Simone , Graf Manuel , Emmenegger Lukas , Tuzson Béla
Published: March 2022

Water vapor (H2O) is the strongest greenhouse gas in our atmosphere, and it plays a key role in multiple processes that affect weather and climate. Particularly, H2O in the upper troposphere - lower stratosphere (UTLS) is of great importance to the Earth's radiative balance, yet accurate measurements of H2O in this region are notoriously difficult, and significant discrepancies were found in the past between different techniques (both in-situ and remote sensing). Currently, cryogenic frostpoint hygrometry (CFH) is considered as the reference method for balloon-borne measurements of UTLS H2O [1]. However, the ongoing phasing-out of the cooling agent required by CFH (freon R23) urges the need of an alternative solution to maintain the monitoring of UTLS H2O in long-term global observing networks, such as the GCOS Reference Upper Air Network (GRUAN).

As an alternative method, we developed a compact instrument based on mid-IR quantum-cascade laser absorption spectroscopy (QCLAS) [2]. The spectrometer incorporates a specially designed segmented circular multipass cell to extend the optical path length to 6 m within a small footprint [3], while meeting the stringent requirements in terms of mass, size, and temperature resilience, posed by the balloon platform and by the harsh environmental conditions of the UTLS. Two successful test flights performed in December 2019, in collaboration with the German Meteorological Service (DWD), demonstrated the instrument's outstanding capabilities under real atmospheric conditions up to 28 km altitude.

The accuracy and precision of QCLAS at UTLS-relevant conditions were validated by a dedicated laboratory campaign conducted at the Swiss Federal Institute of Metrology (METAS). Using a dynamic-gravimetric permeation method, we generated SI-traceable reference gas mixtures with H2O amount fractions as low as 2.5 ppmv and 1.5 % uncertainty in synthetic air. All measurements by QCLAS were found within ± 1.5 % of the reference value, corresponding to a maximum absolute deviation of 210 ppbv, and with an absolute precision better than 30 ppbv at 1 s resolution. This represents an unprecedented level of accuracy and precision for a balloon-borne hygrometer. Further in-flight validation campaigns from Lindenberg (Germany) are currently in preparation.

[1] Brunamonti et al., J. Geophys. Res. Atmos., 2019, 124, 13, 7053-7068.

[2] Graf et al., Atmos. Meas. Tech., 2021, 14, 1365-1378.

[3] Graf, Emmenegger and Tuzson, Opt. Lett., 2018, 43, 2434-2437.
Diffusiophoretic transport of colloids in a porous medium 
Authors: Jotkar Mamta , de Ana Pietro , Cueto-Felgueroso Luis
Published: March 2022

The ability of a colloidal particle to migrate along a local salt concentration gradient, referred to as diffusiophoresis [1, 2], has recently been explored for a variety of technological applications [3-5]. Flows containing dissolved salts and suspended particles in a porous medium can occur in a variety of natural and engineered scenarios including groundwater contamination and remediation, water infiltration in soil, geological carbon sequestration, enhanced oil recovery, to name a few. In all these scenarios, local salt gradients can induce diffusiophoretic motion of transported particles and contribute to the complexity of the overall transport problem. Aiming to unravel the coupling of the underlying physical mechanisms, we conduct pore-scale simulations to investigate the fluid, solute and particle transport in a micromodel. On one hand, we measure the time-lapsed effluent concentration of the colloidal particles close to the outlet and compute the so-called breakthrough curves to understand the influence of diffusiophoresis on the particle macroscopic transport through the whole host medium. On the other hand, we compute Lagrangian statistics from particle tracking at the microscale. Our results hint towards the fact that the microscopic interplay between salt transport, diffusiophoretic particle motion and host medium disorder can impact the macroscale particle dynamics. Lastly, while both, the flow and transport through a porous medium and the diffusiophoretic motion of colloids in a variety of microfluidic devices, are active areas of research, the novelty of our work lies in the intersection of the two.  

 

References:

[1] Derjaguin et al. (1947), “Kinetic phenomenon in boundary films of liquids”, Colloid J. USSR, 9, 335-347.

[2] Anderson (1989), “Colloid transport by interfacial forces”, Annu. Rev. Fluid Mech., 21 (1), 61-99.

[3] Kar et al. (2015), “Enhanced Transport into and out of dead-end pores”, ACS Nano, 9(1), 746-753.

[4] Shin et al. (2017), “Membraneless water filtration using CO2”, Nat. Commun., 8(1), 15181.

[5] Rasmussen et al. (2020), “Size and surface charge characterization of nanoparticles with a salt gradient”, Nat. Commun., 11(1), 2337.
Developing a parsimonious distributed land surface-subsurface hydrological model
Authors: Liu Hai , Rahman Mostaquimur
Published: March 2022

A hydrological model is a simplified representation of the water cycle. A model helps people to understand, predict, and manage water resources. The scope and complexity of the model depend on the modelling goal, availability of required inputs, and computational resources. A wide variety of different hydrologic models exist, which are from simplistic to complex.  Complex models are often computationally very expensive, hampering robust calibration, sensitivity evaluation, and uncertainty analysis. The purpose of this study was to develop a parsimonious distributed land surface-subsurface hydrological model.

The parsimonious model we are developing is a combination of the land surface model V2Karst and a groundwater model that adopts a two-dimensional representation of groundwater flow. V2Karst is a large-scale model for simulating land surface hydrological processes. . The coupled hydrological model can make the simulation steps clearer and meet the simplifying assumptions in some specific demand situations. The model will be useful for robust model calibration, sensitivity tests, and uncertainty analysis.
Is it possible to delineate aggregates in X-ray images of intact soil samples?
Authors: Koestel John , Fukumasu Jumpei , Garland Gina , Larsbo Mats , Nimblad-Svensson David
Published: March 2022

Soil structure refers to the spatial arrangement of primary soil particles, their cohesion and the pores in between them. It has a fundamental impact on a variety of soil functions including carbon sequestration and water holding capacity. Researchers in this field either approach the topic by investigating the geometry of pore networks in undisturbed soil; or they instead evaluate properties of aggregates obtained from disassembling soil clods. Which of the two approaches is chosen depends on the requirements and traditions in the respective soil science discipline. There have been surprisingly little efforts undertaken to relate both viewpoints on soil structure quantitatively. In this study, we present and evaluate methods to delineate soil aggregates in eight X-ray images of undisturbed soil samples. The approaches exploit crack formation upon shrinkage in drying soil. Comparing the image-derived aggregates to results from drop-shatter tests, we observed promising trends but overall, the results remained inconclusive. On the one hand, this was due to the very small number of studied samples. On the other hand, the presented aggregate delineation approaches have potential for improvement. We suggest to develop this line of research and apply it to larger numbers of samples, different scales and different physical aggregate isolation approaches, like dry and wet sieving. For example, it may be evaluated whether microaggregates are identifiable in still intact macroaggregates.
Water mass impacts of the main climate drivers over Australia by satellite gravimetry
Authors: Ramillien Guillaume , Seoane Lucia , Darrozes José
Published: March 2022

We propose a spatial characterization of the hydrological contributions of several climate drivers that impact continental water mass storage of Australia determined by remote sensing techniques over the period 2002 - 2021. For this purpose, the Slepian functions help for recognizing the signatures of such important changes in the varying gravity field solutions provided by GRACE and GRACE-FO satellite missions such as mascon solutions of 400-km resolution. Time series of 25 Slepian coefficients that correspond to ~99.9% of the eigenvalue spectrum are used to be analyzed and compared to the profiles of climate indexes i.e. El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and South Annular Mode (SAM). The best correlations enable to extract specific Slepian coefficients, and then reconstruct the regional hydrological structures that concern each climate driver, in particular for the southeastern basins strongly influenced by the important flooding during La Niña episode of 2010.
Utilisation of geomagnetic data and indices for GIC applications
Authors: Trichtchenko Larisa
Published: March 2022

The development of mitigation capabilities to counteract the detrimental impacts of space weather on critical ground infrastructure, such as power lines, pipelines and cables, depends on the availability of the observations of their causes as well as monitoring of the subsequent results.
Although direct monitoring of critical infrastructure response to GeoMagnetic Disturbances (GMD) has become more advanced in recent years, observations of geomagnetic variations continue to play the most important role in all aspects of development of safe and robust operational procedures and technology, from the forecast of geomagnetically induced currents (GIC) to their climatological studies.
This presentation shows how different types of geomagnetic data are utilised, from 3-hour and 1-hour geomagnetic indices to 1 sec. geomagnetic data, and from real-time to multi-year climatology in order to provide forecasts of GIC, identify the effects of different geomagnetic patterns on infrastructure response or provide “climatology” for network design considerations.  
Symmetric instability in the surface and deep components of the Atlantic Meridional Overturning Circulation close to the equator
Authors: Goldsworth Fraser , Marshall David , Johnson Helen
Published: March 2022

Models, theory and observations suggest that symmetric instability is excited in the North Brazil Current after it crosses the equator. The instability is fuelled by the advection of waters with anomalous potential vorticity from the Southern to the Northern Hemisphere. There also exists a deep western boundary current which sits below the North Brazil Current. This current advects anomalous potential vorticity across the equator too, and so also becomes symmetrically unstable upon crossing it. Numerical models and scaling arguments will be used to predict the similarities and differences between the action of symmetric instability in the surface and deep currents. We will then explore how the excitement of the instability affects the structure of the deep western boundary current, and how this impacts the development of mesoscale features further down-stream.
Influence of rock pore structure on the protective coating against weathering
Authors: Oguchi Chiaki , Ikeda Yukina
Published: March 2022

Tuff is rich in color and is used as a stone material, and it is also a rock that forms a unique landscape in Japan, a volcanic country. However, since it is generally a fragile rock, it is susceptible to weathering and deterioration. The present study conducted an experiment to confirm the effectiveness of the surface protectant using tuff with different physical characteristics. Sodium sulfate aqueous solution was used to determine the effectiveness of protective agent application for 5 types of tuff (Oya stone, Nikka stone, Ashino stone, Tatsuyama stone, Towada stone) An experiment was conducted in which the lower 3 cm of a 5 cm × 5 cm × 15 cm specimen that had been oven-dried at 110 ° C was immersed in a salt solution, and 20 ° C-40 ° C was repeated for up to 20 cycles in a 48-hour cycle. When the weight and P-wave velocity of each specimen were measured every cycle, the solution reached the surface of the uncoated stone material for comparison, salt crystals were deposited. The surface of the specimen was peeled off, and the P-wave velocity gradually decreased.  On the other hand, in the stone material coated with the protective agent, salt crystallization was not observed even when the solution reached the top surface shortly after the start of the experiment.  The P wave velocity did not decrease, despite cracks occurred as the experiment progressed. As a result, the P-wave velocity began to decrease and the surface layer fell off. In Ashino and Tatsuyama stones, the coated specimens were more severely destroyed than the uncoated specimens. In Oya stone and Towada stone, which contain clay minerals (miso) in the form of patches, crushing proceeded from the miso part. This experiment suggests that the effect of the protective agent may depend on the rock structure and the pore diameter. In other words, for rocks containing miso, the use of a protective agent is likely to increase deterioration regardless of the pore structure. For rocks with a large proportion of micropores and low durability against salt weathering, the use of a protective agent is used. Therefore, the start time of surface exfoliation can be delayed. In addition, in rocks with a large proportion of large gaps (> 10-0.5 μm), even if crystallization occurs on the surface of the specimen. The  peeling does not occur for a while, but the protective agent penetrates deep into the thick protective agent penetration area. It is considered that the crystallization of the salt occurs more internally and the deterioration is more severe than it should be. 
The influence of spectral cutoff in random wave simulations
Authors: Adock Thomas , Barratt Dylan , Tang Tianning , Bingham Harry , van den Bremer Ton
Published: March 2022

When investigating large ocean waves we frequently run simulations or experiments with random waves. For practical reasons such seastates are often initalised without the full spectral tail which would normally be present in the ocean. The change in the distribution of energy associated with this is generally very small and it impact on subsequent wave statistics presumed negligible. Here we investigate this by running firstly fully non-linear simulations of the sea-state considered in the experiments of Latheef & Swan (2013) and secondly Modified non-linear Schrödinger equation simulations of the experiments of Onorato et al. (2009). We find a consistent pattern across our simulations (which are also consistent with other results in the literature). We find that the curtailing of the spectrum in the initial conditions has a significant impact on the subsequent wave statistics—cutting off the spectrum leads to significantly more rogue waves than would otherwise be expected. We attribute this to the curtailed spectrum being far from equilibrium and this driving a strongly non-linear response. The results presented here are only for directionally spread waves—unidirectional waves are not expected to show the same physics.
Fenics_ice framework applied to three West Antarctic ice streams: Smith, Pope and Kohler Glaciers.
Authors: Recinos Beatriz , Goldberg Daniel , Maddison James , Todd Joe
Published: March 2022

Fenics_ice is a finite element model framework written in Python that quantifies the initialization uncertainty for time-dependent ice sheet models. Here, we apply for the first time this framework to real ice streams in the Amundsen basin: Smith, Pope and Kohler Glaciers. We quantify the degree to which observational uncertainty translates to parametric uncertainty (posterior uncertainty of inversions for basal drag and ice stiffness fields) and to uncertainty in projected quantities of interest (QoIs) such as sea level contribution. The framework implements the Shallow Shelf Approximation (SSA), and implements a control methods approach to invert for the basal drag and ice stiffness fields. Beginning with a cost function optimization which can allow for either gridded or point-cloud velocities, we generate a low-rank approximation to the posterior covariance of the parameters through the use of the cost function Hessian. In our work, the Hessian is calculated through algorithmic differentiation (AD) using the “complete” Hessian rather than the Gauss–Newton approximation. We then project the covariance on a linearization of the time-dependent ice sheet model (again using AD to generate the linearization) to estimate the growth of QoI uncertainty over time. We then show the model framework and capabilities when applied to these ice streams and our future plans to scale our framework into a larger domain.
Revisiting the ExTL: From tracer correlations to dynamical processes
Authors: Hoor Peter , Kaluza Thorsten , Kunkel Daniel , Lachnitt Hans-Christoph , Amelie Mayer , Bense Vera , Bozem Heiko , Joppe Philipp
Published: March 2022

The extratropical transition layer or ExTL has been recognized about 20 years ago as part of the upper troposphere / lower stratosphere (UTLS) of the extratropics. This region encompasses the tropopause and shows the chemical characteristics of both, the stratosphere and the troposphere. Tracer-tracer correlations show this ambiguous chemical character as the integral effect of numerous different processes contributing to transport and subsequent mixing. The ExTL exhibits a chemical composition which is remarkably distinct from the deeper lowermost stratosphere. The ExTL roughly extends 2 km (or 30K potential temperature) above the local (dynamical) tropopause. Notably the ExTL has been identified with only a weak seasonality (if at all) being a persistent feature at the extratropical tropopause all year round.

Various dynamical processes have been recognized to contribute to the chemical composition of the ExTL such as larger scale processes related to stirring and mixing at the jets as well as smaller scale processes such as overshooting convection, gravity wave induced turbulence and radiatively induced diabatics at the tropopause. The sum of these processes does not only affect the tropopause sharpness (i.e. the tropopause inversion layer TIL) but also contributes to the surprisingly distinct composition of the ExTL. This is a direct result of the short time scales of cross tropopause transport and mixing compared to the lowermost stratosphere beyond the ExTL where longer time scales prevail. However, a dynamical process based explanation for the upper bound of the ExTL is yet missing.

Most recent analysis of ERA5 reanalysis data provides strong indication that vertical shear is a key feature for maintaining the ExTL over the whole year. The results show that transient shear processes are a common feature of the tropopause region with a vertical extent of 2km (or 30 K in potential temperature units) around the tropopause. Here, they constitute a persistent potential cause of dynamical instability, which may lead to turbulence and mixing and thus the observed chemical distinctness and extent of the ExTL.
Do politicians’ reelection incentives affect wildfires occurrence?
Authors: Piroli Erika
Published: March 2022

Previous studies have suggested that the behaviour of policymakers can be influenced either for personal gain or for electorate pleasing. However, politicians’ role and incentives in the determination of fire regimes have been largely ignored in research advocating for the adoption of effective fire adaptation and prevention strategies. In this context, understanding the drivers of wildfires is pivotal for developing and promoting effective fire prevention strategies. This empirical analysis investigates whether there is a significant change in wildfire occurrence around the gubernatorial election years and whether the change is consistent with the incumbent candidate running for re-election. To assess the impact of electoral cycles on wildfire occurrence, I estimate a Quasi-Maximum Likelihood (QML) Poisson fixed-effects model.
Assessing the value of seasonal forecasts in informing reservoir operations in water-stressed Mediterranean basins
Authors: Crippa Nicola , Yang Guang , Grillakis Manolis , Koutroulis Aristeidis , Giuliani Matteo
Published: March 2022

Population expansion and socio-economic development have been increasing the pressure on water resources, which are often exploited in a non-renewable way. Besides, climate change can modify hydroclimatic patterns and exaggerate freshwater water stress. Flexible operation of existing water reservoirs is one of the most cost-effective ways to mitigate water-related stress, by storing water when it is abundant and releasing it when droughts persist. In this context, medium - to long-term hydroclimatic forecasts are set to cover a central role for properly informing reservoir decision-making and operation policy design. State-of-the-art hydroclimatic forecast products are indeed becoming more and more skillful at seasonal or longer lead-times, especially in regions characterized by climate teleconnections or by predictable hydrological behavior, such as baseflow- or snow-dominance. Nevertheless, the link between forecast skill and forecast value, i.e. the performance improvement obtained thanks to the use of the forecasts, is neither easily predictable nor necessarily positive. Each system indeed requires specific forecasts according to its characteristics, such as climate and hydrological regime, size of the reservoir, management objectives, and the skill of existing forecast systems do not necessarily translate into a significant gain in system performance.

In this work, we quantify the value of seasonal forecast information in informing the operations of the Faneromeni reservoir on the Crete island. The reservoir is primarily used to provide water to an important agricultural district during the dry summer season. Current operation of this reservoir is based on the available storage at the beginning of the irrigation season, which, in normal conditions, allows the supply of the irrigation demand if the reservoir is completely full; otherwise, the reservoir releases are modulated according to the storage shortage. We instead investigate alternative policies for the operations of the Faneromeni reservoir by using the Evolutionary Multi Objectives Direct Policy Search (EMODPS) method, which allows the design of flexible rules to cope with the variability of the hydrologic conditions as well as to include forecast information for conditioning operational decisions.

Preliminary results show that EMODPS policies can improve the existing operation of the Faneromeni reservoir. Moreover, these solutions also allow to mitigate the negative impacts of climate change and flexibly adapt the reservoir operations to the projected hydroclimatic conditions.

 

This work is supported by the STREAM project funded by the Prince Albert II of Monaco Foundation, grant number 2981.
Controls on projected climate extremes in two regional ensembles for the UK
Authors: Brierley Chris , Barnes Clair , Keeping Theodore , Chandler Richard
Published: March 2022

As part of the UK Climate Projections 2018, a perturbed physics ensemble of regional climate model simulations was created. Each of the 11 member was created using a variant of the Hadley Centre's global and regional models, using an RCP8.5 scenario and a Europe-wide 12km grid. Here we compare the projected climate changes of this ensemble to those projected by the EuroCORDEX multi-model ensemble over the UK. The two ensembles exhibit biases of comparable magnitudes during the historical period, but project increasingly divergent trends in future climate change. We show that for some indices, the ensembles sample the same future space, but in some cases do not even overlap - despite the wide spread in each ensemble. The effects of these diverging trends are illustrated in a case study of compound indices of extreme weather, such as the Fire Weather Index (derived from temperature, wind, humidity and precipitation variables), for which bias correction is known to be particularly problematic. Future GCM projections can be constrained by the fidelity of each ensemble member’s representation of the observed climate. We suggest how this approach might be extended to RCM ensembles, given the ability to match the spatial pattern seen in observations can be determined by the RCM whilst the magnitude of the climate change response is more related to the driving global model.
Coronal rain in randomly heated arcades
Authors: Li Xiaohong , Keppens Rony , Zhou Yuhao
Published: March 2022

Adopting the MPI-AMRVAC code, we present a 2.5-dimensional magnetohydrodynamic simulation, which includes thermal conduction and radiative cooling, to investigate the formation and evolution of the coronal rain phenomenon. We perform the simulation in initially linear force-free magnetic fields that host chromospheric, transition-region, and coronal plasma, with turbulent heating localized on their footpoints. Due to thermal instability, condensations start to occur at the loop top, and rebound shocks are generated by the siphon inflows. Condensations fragment into smaller blobs moving downwards, and as they hit the lower atmosphere, concurrent upflows are triggered. Larger clumps show us clear coronal rain showers as dark structures in synthetic EUV hot channels and as bright blobs with cool cores in the 304 Å channel, well resembling real observations. Following coronal rain dynamics for more than 10 hr, we carry out a statistical study of all coronal rain blobs to quantify their widths, lengths, areas, velocity distributions, and other properties. The coronal rain shows us continuous heating–condensation cycles, as well as cycles in EUV emissions. Compared to the previous studies adopting steady heating, the rain happens faster and in more erratic cycles. Although most blobs are falling downward, upward-moving blobs exist at basically every moment. We also track the movement of individual blobs to study their dynamics and the forces driving their movements. The blobs have a prominence-corona transition-region-like structure surrounding them, and their movements are dominated by the pressure evolution in the very dynamic loop system.
Astronomical forcing as a trigger of abrupt climate changes at the end of interglacials 
Authors: Yin Qiuzhen , Wu Zhipeng , Berger Andre , Goosse Hugues , Hodell David
Published: March 2022

Many paleoclimate records show that the end of interglacials of the late Pleistocene was marked by abrupt cooling events and increased millennial variability. Strong abrupt cooling occurring when climate was still in a warm interglacial condition is puzzling and its cause remains uncertain. In this study, we performed transient climate simulations for all the eleven interglacial (sub)stages of the past 800,000 years with the model LOVECLIM1.3 (Yin et al., 2021). Our results show that there exists a threshold in the astronomically induced insolation below which abrupt changes at the end of interglacials occur. When the summer insolation in the Northern Hemisphere (NH) high latitudes decreases to a critical value, it triggers a strong, abrupt weakening of the Atlantic meridional overturning circulation (AMOC) and a strong cooling in the NH followed by high-amplitude variability. The mechanism involves sea ice feedbacks in the Northern Nordic Sea and the Labrador Sea. Similar abrupt oscillations happen in the simulated temperature, precipitation and vegetation from low to high latitudes. Our simulated results are supported by observations from many marine and terrestrial records, including for example the planktic d18O record from the Iberian Margin, the Greenland ice core record and the Chinese speleothem records. Our study shows that the astronomically-induced slow variation of insolation could trigger abrupt climate changes. The insolation threshold occurred at the end of each interglacial of the past 800,000 years, suggesting its fundamental role in terminating the warm climate conditions of the interglacials. Our results show that the next insolation threshold will occur in 50,000 years, suggesting an exceptionally long interglacial ahead, which is in line with what has been suggested by previous modelling studies. 

Reference:  Yin Q.Z., Wu Z.P., Berger A., Goosse H., Hodell D., 2021. Insolation triggered abrupt weakening of Atlantic circulation at the end of interglacials. Science, 373, 1035-1040, DOI: 10.1126/science.abg1737