bluuebunny/crossref_metadata_2025 huggingface dataset:
Can instabilities work in a turbulent plasma and if so, what conditions are needed for instabilities to act?
Authors: Opie Simon , Verscharen Daniel , Chen Chris , Owen Christopher
Published: March 2022

The solar wind is a continuous outflow of plasma from the Sun, which expands into the space between the planets in our solar system and forms the heliosphere. The solar wind is inherently turbulent and characterised by kinetic micro-instabilities on a range of scales.  Large-scale compressions (ubiquitous in solar-wind turbulence) create conditions for proton, alpha-particle and electron micro-instabilities, which transfer energy to small-scale fluctuations. These instabilities are driven by various sources of free energy (e.g. particle beams, differential flows, heat fluxes, temperature anisotropies) and make a significant contribution to the fluctuation spectrum at kinetic scales, where energy dissipation occurs. This presentation investigates the occurrence and the behaviour of kinetic instabilities in turbulent space plasmas with particular emphasis on the conditions necessary for instabilities to act.

We consider instabilities driven by proton temperature anisotropy in the turbulent solar wind by using statistical methods to analyse the Solar Orbiter data and characterise the turbulence at the relevant scales and amplitude. We compare theoretical calculations with the high-resolution data available from the Solar Orbiter MAG and SWA instruments. From this analysis we infer conditions that are necessary for instabilities to act in a turbulent plasma and demonstrate how these conditions relate to the assumptions that underpin theoretical analyses at kinetic scales. We will also introduce the next steps in this research, including the modelling and quantification of energy transfer processes at kinetic scales with particular reference to scaling law behaviours in the turbulent solar wind.   

 
Land subsidence correlated with flooding during Hurricane Harvey and the assessment of future flood hazards for Houston & Galveston Texas
Authors: Miller Megan M. , Shirzaei Manoochehr
Published: March 2022

In August 2017, Hurricane Harvey brought record rainfall, elevated storm tide, flooding and socioeconomic devastation to southeastern Texas. Using the radar backscattering difference between Sentinel-1A/B satellite acquisitions, a snapshot of standing water at the time of the satellite acquisition is provided and compared with designated flood hazard zones.

Next, Vertical land motion (VLM) is found by combining GNSS with multitemporal interferometric processing of SAR datasets acquired by ALOS and Sentinel-1A/B satellites. Land subsidence is observed up to 49 mm/yr during the ALOS acquisition period (Jul-2007–Jan-2011) and 34 mm/yr for the Sentinel-1A/B (Dec-2015 to Aug-2017) acquisition periods. Of the flooded area, 85% subsided at a rate > 5 mm/yr supported by the Chi-square test of independence.

Hurricane Harvey and other recent storms highlight potential vulnerabilities of flood resilience plans in coastal Texas that will degrade with climate change and rising seas. Combining VLM with sea-level rise (SLR) projections and storm surge scenarios for the years 2030, 2050, and 2100, we quantify the extent of flooding hazards for the Houston and Galveston areas. VLM is resampled and projected on LIDAR high-resolution topographic grids, then multiple inundation and flooding scenarios are modeled. By the year 2100, over 76 km2 are projected to subside below sea level from VLM. Holding other variables constant, subsidence increases the area of inundation over SLR alone by up to 39%. Under the worst-case composite scenario of an 8-m storm surge, subsidence, and the SLR RCP8.5, the total affected area is 1,156 km2. These composite scenarios produce model maps which can improve flood resiliency plans.
The effects of incorporating agricultural conservation practices at the farm- and management-scales in the Czech landscape
Authors: Noreika Nina , Winterova Julie , Li Tailin , Krasa Josef , Dostal Tomas
Published: March 2022

SWAT (Soil and Water Assessment Tool) is an open-access hydrologic, basin-scale model; it is the most popular hydrologic model in modern literature. SWAT contains hundreds of editable parameters making it a flexible option for nearly any basin.

There is a significant precedent for incorporating agricultural conservation practices into SWAT.  Contour farming results in a reduction of surface runoff by impounding water in small depressions as well as a reduction of sheet and rill erosion by reducing the erosive power of surface runoff and preventing or minimizing the development of rills. This practice is represented by adjusting the SCS curve number in SWAT. Residues are meant to slow down surface and peak runoff by increasing surface roughness. They also increase infiltration and reduce surface runoff by decreasing surface sealing and slowing down overland flow. Finally, residues reduce sheet and rill erosion by reducing surface flow volume. Conservation tillage and residue management are represented by adjusting the curve number and manning’s roughness coefficient for overland flow, respectively. Filter strips can be placed per HRU (so can be place only along a stream or between fields) & their trap efficiency is based on width of the strip. The equation is derived from the 1978 USDA Agricultural Handbook, but many studies have pointed out issues with this method- as the filter strip width approaches 30m, the sediment trap efficiency approaches 1. A sediment trap efficiency close to 1 is only seen in plot-scale, shallow slope, field experiments during which uniform flow (not concentrated flow) is achieved. We instead assigned a filter strip width back calculated from typical filter strip trap efficiencies calculated in field experiments locally.  

In addition to the filter strip, contour farming, reduced tillage, and residue management scenarios, we also ran field size reduction scenarios at the farm- and subbasin-scale in two Czech basins, Nučice and Vrchlice. We were able to utilize SWAT to determine the effects of various agricultural management practices on the small water cycle in two Czech basins ranging from 0.5 to 100 km2.

Acknowledgment: The presented research has been performed within project H2020 No. 773903 Shui, focused on water scarcity in European and Chinese cropping systems and the Grant Agency of Czech Technical University in Prague, No. SGS20/156/OHK1/3T/11.
Investigation of the effect of tropospheric mapping functions for different station heights and latitudes on PPP
Authors: Durmus Faruk Can , Dogan Ali Hasan , Erdogan Bahattin
Published: March 2022

Global Navigation Satellite Systems (GNSS) are used for different geodetic applications such as monitoring deformations and determining plate velocities. Precise positions of stations are needed for such studies. GNSS error sources should be modelled or eliminated to achieve precise coordinates. Some error sources (e.g., receiver and satellite clock errors) can be eliminated by differencing techniques in relative point positioning. However, in precise point positioning (PPP) these errors should be modelled since the technique uses un-differenced and ionosphere-free combinations. Tropospheric signal delay, one of the atmospheric error sources of GNSS, does not depend on the signal frequency; hence, it should be modelled. This delay is modelled in zenith direction, although it occurs along the signal path. This relation is provided with tropospheric mapping functions (MFs). In this study, the effects of MFs for different station heights and latitudes have been investigated. The datasets of 294 continuously operating reference stations were processed with Jet Propulsion Laboratory’s GipsyX v1.2 software. Moreover, the datasets were subdivided into non-overlapping periods between 2 and 24 h to examine the effects of MFs on different session durations.

 

Keywords: GPS, PPP, Troposphere, Mapping Functions, GipsyX v1.2
 A regional (land – ocean) comparison of the seasonal to decadal variability of the Northern Hemisphere jet stream 1871-2011
Authors: Hallam Samantha , Josey Simon , McCarthy Gerard , Hirschi Joel
Published: March 2022

Seasonal to decadal variations in Northern Hemisphere jet stream latitude and speed over land (Eurasia, North America) and oceanic (North Atlantic, North Pacific) regions are presented for the period 1871 – 2011 from the Twentieth Century Reanalysis dataset

Significant regional differences are seen on seasonal to decadal timescales. Seasonally, the  jet latitude range is lower over the oceans compared to land, reduced from 20° over Eurasia to 10° over the North Atlantic where the ocean meridional heat transport is greatest. The mean jet latitude range is at a minimum in winter (DJF), particularly along the western boundary of the North Pacific and North Atlantic, where the land-sea contrast and SST gradients are strongest.

The 141-year trends in jet latitude and speed show differences on a regional basis. The largest increasing trends in jet latitude and jet speed are observed in the North Atlantic, with increases in winter of 3° and 4.5ms-1, respectively. There are no trends in jet latitude or speed over the North Pacific.

Long term trends are overlaid by multi decadal variability. In the North Pacific, 20-year variability in jet latitude and jet speed are seen, associated with the Pacific Decadal Oscillation which explains 50% of the winter variance in jet latitude since 1940.

In addition, current work on a lead/lag analysis of western boundary currents/ocean variability in the North Atlantic and North Pacific and links to the northern hemisphere jet stream will be presented.

Hallam et al., A regional (land-ocean) comparison of the seasonal to decadal variability of the northern hemisphere jet stream. Climate Dynamics (2022 in revision).https://doi.org/10.21203/rs.3.rs-607067/v1

 
Reconstructing deformable continental blocks and crustal thicknesses back through time within the North Atlantic Ocean
Authors: King Michael , Welford J. Kim
Published: March 2022

        The tectonic evolution of the North Atlantic Ocean has been extensively studied using a variety of geological, geophysical, and plate reconstruction techniques. Recently, deformable plate tectonic reconstructions, built using the GPlates software, have become an increasingly used method for studying the plate kinematics, deformation, and subsequent crustal thickness evolution of tectonic regimes. For the North Atlantic Ocean in particular, deformable plate models have proven to be useful for studying the kinematic evolution of continental blocks (e.g. Flemish Cap and Galicia Bank) and the partitioning of strain within sedimentary basins (e.g. Orphan Basin). However, despite these advancements, previously published deformable plate models have included limitations that can be geologically unsatisfying. Some notable examples include, but are not limited to, uniform crustal thickness assumptions at model start times, and the rigid nature of continental blocks and model boundaries that define the limits of where deformation takes place.  

        Using the interplay of GPlates and its python programming module, pyGPlates, we present a new deformable plate modelling strategy and application within the North Atlantic Ocean. In contrast to previous studies, this approach considers deformation within continental blocks and the reconstruction of present day crustal thickness estimates calculated via gravity inversion. In addition, we also demonstrate the minimized impact of rigid landward model boundaries using this approach and the resultant ability to reconstruct rift domain boundaries a priori. The results of this study provide insight into the pre-rift (200 Ma) crustal thickness template of the North Atlantic and the evolution of relevant continental blocks during rift-related deformation. Furthermore, this work also highlights the potential impact of Appalachian and Caledonian terrane boundaries on the distribution and extent of rifting experienced along the Newfoundland, Ireland, and West Iberian offshore rifted margins.  
The significance of Atlantic Water routing in the Nordic Seas during the present interglacial
Authors: Telesiński Maciej M. , Łącka Magdalena , Kujawa Agnieszka , Zajączkowski Marek
Published: March 2022

The Nordic Seas are a key region for global ocean circulation, crucial in water mass exchange between the North Atlantic and the Arctic oceans, and deepwater formation. The advection of Atlantic Water (AW) to the Nordic Seas is decisive for the oceanography and climate of the region and beyond. Here, we present a set of sedimentary records, including two new cores from the western Nordic Seas to reconstruct the history of AW routing in the Nordic Seas over the Holocene. Our results show that the early Holocene (11.7 - 8 ka BP) thermal maximum, caused by an “overshoot” of overturning circulation and high insolation, was limited to the eastern Nordic Seas, while the western part remained cold due to the meltwater blocking the spreading of AW. After 8 ka BP, the retreat of the freshwater lid allowed AW to reach the central Greenland Sea, where deep convection developed. The weakening of the overturning circulation during the 8.2 ka BP event could have played an important role in this circulation shift. After 5 ka BP, the increase in sea-ice export from the Arctic strengthened deep convection, which intensified the westward AW flow. A disruption of convectional activity around 2.7 ka BP, triggered by a minimum in solar activity, caused cooling and expansion of sea ice in the Nordic Seas and might have contributed to a global climatic deterioration. The overturning circulation in the Nordic Seas did not recover to its previous state until the present. We demonstrate that the rate of AW advection into the Nordic Seas alone is not enough to understand the oceanographic evolution of this area and its influence on regional or even global ocean and climate changes. The shifts in AW routing within the Nordic Seas and the rate of deep convection are also important.
How do we identify flash droughts? Analysis tool and Central European Croplands analysis
Authors: Lima Alencar Pedro Henrique , Paton Eva Nora
Published: March 2022

Flash droughts are often characterized as events of rapid and unusually large depletion of root-zone soil moisture, in comparison to average conditions, caused by climatic compound conditions over short periods (weeks). We compared six flash drought identification methods and analysed their functioning using measured data from FLUXNET2015 stations across Central Europe. All methods were implemented in an R package and are available as a Shiny app for the public, where the user can visualise the different results of flash drought identification for each method. An in-depth analysis and cross-comparison of methods for co- and misidentification for cropland sites showed a large degree of synchronicity among them, although some divergence was detected, related to four intrinsic differences in the underlying flash drought definitions associated to each identification method: (1) type of critical variable, (2) velocity of drought intensification, (3) pre-set threshold values for final depletion, and/or (4) minimum length of the duration of flash droughts. To balance strengths and weaknesses of the individual methods, we suggest the use of an ensemble approach for each event identification. To balance such strengths and weaknesses of the individual methods we propose an ensemble approach for event identification, allowing the detection of the current unclearly defined sub-types of flash droughts, related to the different combinations of compound drivers and differences in intensification dynamics.
Using measurements uncertainties in climate applications
Authors: Madonna Fabio , Marra Fabrizio , Rosoldi Marco
Published: March 2022

Measurement uncertainties are a dispersion indicator which must be quantified when the estimation of a geophysical quantity is provided. Measurement uncertainty is defined as a "parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand’' (GUM, 2018). Therefore, measurement uncertainties can discriminate more and less certain data with confidence. Observations form the basis for any evidence of climate change. However, observations themselves possess uncertainties originating from many sources including measurement error and errors imposed by the algorithms generating derived products (Matthews et al., 2013). Nevertheless, traditional approach to climate data records, either obtained from observations or from data assimilation systems, offers datasets where uncertainty information is generic, misleading or missing. 

In particular, measurement uncertainties have been often neglected adducing their self-compensation when these are propagated from raw data to geophysical products or derived products. This is also because the metadata available and the collected observations do not allow their appropriate estimation. Moreover, other sources of uncertainty (e.g. due to interpolation, representativeness, residual of homogenization algorithms, etc.) must be quantified to provide a  proper uncertainty estimation in the derived products.

 

More recently an increasing number of datasets are provided with measurement uncertainties; few satellite retrievals are generated with a quite detailed uncertainty quantification; atmospheric renalysis is provided with an uncertainty estimation, although systematic model errors not taken into account and uncertainties are assumed uncorrelated; finally, the most recent homogenized datasets are provided with an estimation of uncertainties also for the historical data.

 

The uncertainties in climate observations pose a set of methodological and practical challenges for both the analysis of long-term trends and the comparison among datasets or with theoretical thresholds. 

 

In this work examples will be provided showing the importance of quantifying uncertainties of climate data records. The aim is also to encourage the community to develop other use cases for showing the impact of using uncertainties in climate applications. 
Attenuation of gravity waves and kinetic viscosity in the ionosphere
Authors: Chum Jaroslav , Fagre Mariano , Podolska Katerina , Rusz Jan
Published: March 2022

     Gravity waves (GW) couple various atmospheric layers and influence dynamics of the region in which they dissipate their energy. Attenuation of GW is in this contribution calculated from the ratio of GW kinetic energies observed at different heights by multi-frequency and multi-point continuous Doppler sounding that allows three-dimensional (3D) analysis of GW propagation in the ionosphere. It is shown that the attenuation of GWs increases with height, which is consistent with the hypothesis that mainly viscous damping and losses due to thermal conductivity are responsible for the wave attenuation in the thermosphere/ionosphere. The kinematic viscosity of the highly rarefied air at the height of observation is estimated from the observed attenuation with altitude and complex dispersion relation for GWs that includes viscosity and thermal conductivity, which is linked with the viscosity via Prandtl number. The intrinsic (wind rest frame) characteristics of GW that enter the dispersion relation are obtained after subtracting the neutral wind velocities from the observed phase velocities using HWM-14 wind model. A more detailed modelling of GW attenuation will be done in the future. 
MultiPAC: A novel approach to quantify the clogging degree of a riverbed
Authors: Haun Stefan , Negreiros Beatriz , Kunz Maximilian , Schwindt Sebastian , Aybar Galdos Alcides , Noack Markus , Wieprecht Silke
Published: March 2022

Riverbed clogging, also referred to as colmation, describes the infiltration of fine sediment in gravel bed rivers. The infiltrated fine sediment leads to a reduction of the pore space and, in the worst case, to a sealing of the riverbed. As a result of severe colmation, negative effects on the environment may occur, such as a limited oxygen supply for fish eggs or for macrozoobenthos.

The quantification of the degree of colmation and its impact on the ecological status of a river is often based on an expert assessment or only on a single parameter, such as the amount of fine sediment. However, depending on the sediment matrix of the riverbed, the packing arrangement of particles, or the organic material in the riverbed, a single parameter may not be sufficient to evaluate the degree of colmation. In addition, most expert-based assessments, such as mapping of inner and outer colmation, are on the one hand biased due to subjectiveness and on the other hand, only investigate the surface layer of the riverbed. Knowledge on possible occurring colmation layers in deeper regions of the interstitial will not be gained by using these methods.

In this study, a novel MultiParameter Approach to assess Colmation (MultiPAC), is presented, which measures several physical parameters, and provides insights into the status of colmation conditions in the interstitial. These are:

measurements of the sediment composition for identifying surface and subsurface grain size distributions and for assessing fine sediment fractions,

measurements of porosity by using Structure-from-Motion in combination with freeze-core sampling, and

measurements of oxygen concentration and hydraulic conductivity by using a newly developed double-packer system, called VertiCo.

The VertiCo (Vertical profiles of hydraulic Conductivity and dissolved Oxygen) enables measurements with a high spatial resolution over the vertical axis of the riverbed to enable the quantification of possible colmation layers or changes of the conditions in the interstitial over depth.

With the MultiPAC it is feasible for the first time to holistically assess the influence of oxygen and hydraulic conductivity in the interstitial. By taking also into account the properties of the sediment matrix and the porosity, the degree of colmation of a riverbed can be identified. In addition, these findings may provide important information to support the classification of the ecological state of river sections.
Assessing the geometry of the Main Himalayan thrust in central Nepal: Insights from thermokinematic modelling
Authors: Ghoshal Suryodoy , McQuarrie Nadine , Robinson Delores M. , Huntington Katherine , Ehlers Todd A.
Published: March 2022

The 2015 Gorkha earthquake reignited an existing debate about whether geometric barriers on faults play a role in containing the propagation of ruptures. Models suggest that the extent of the Gorkha earthquake rupture, and of other historical earthquakes were controlled by the locations of ramps in the Main Himalayan thrust (MHT), notably on the western edge of the rupture. The existence of such a pronounced lateral boundary to the west of the Gorkha epicenter is supported by an offset in the surface trace of the Main Central thrust (MCT), closely followed by an offset in the distribution of young (<5 Ma) muscovite 40Ar/39Ar (MAr) ages. However, the zircon (U-Th)/He (ZHe) and apatite fission track ages show more linear east-west distributions over the same region, as does Physiographic Transition 2 (PT2). We explore the formation of these relationships by combining forward-modeled balanced cross-sections through the Marsyangdi, Daraundi, and Budhi Gandaki valleys in central Nepal, and investigate the continuity of active structures across the western portion of the Gorkha rupture. The sequential kinematics of each of these sections are combined with a thermokinematic model (PECUBE) to evaluate the exhumation and cooling histories of the rocks exposed at the surface. We gauge the validity of these models by comparing their predicted cooling ages to measured ages, discarding those that do not match the measured distribution of cooling ages.

Our 3D models show that the offset in the surface geology along the Daraundi is due to a shorter (by 1/3) Trishuli thrust sheet, that has been completely translated to the south of the modern ramp and folded by the Lesser Himalayan duplex. Similarly, the southern extent of the reset MAr ages is also controlled by these relationships requiring observed surface offsets to be the result of changes in the hanging wall rocks translated over the ramp, rather than changes in the geometry of the modern ramp. Notably, the continuity and location of the modern MHT ramp is evidenced by the linear distribution of the youngest ZHe and AFT ages, which are most sensitive to the location of the active ramp. Additionally, the out-of-sequence thrust responsible for PT2 soles directly into the modern ramp during its proposed period of activity at ~1.2 Ma, resulting in the highly linear trace of PT2, running parallel to the location of the ramp. These linear relationships and their reproducibility in thermo-kinematic models argue strongly against any geometric offsets in the modern MHT ramp that have been proposed to limit rupture propagation in central Nepal.
Insights of multiple sensors remote sensing techniques for the mapping of subglacial valleys beneath glaciers and ice shelves 
Authors: Millan Romain , Mouginot Jeremie , Morlighem Mathieu , Rabatel Antoine , Gimenes Lucille , Champollion Nicolas , Rignot Eric , An Lu , Bjørk Anders
Published: March 2022

Accurate mapping of subglacial bedrock topography is of prime importance to correctly simulate the past and future evolution of glaciers and ice sheets. As ocean warming is a major driver of recent changes in Greenland and Antarctica, mapping the bathymetry of the ocean seafloor in fjords and underneath ice shelves is crucial to accurately model warm water pathways up to the ice margins and grounding lines. A good knowledge of this bedrock topography also allows to better understand the past extent of the ice sheets and identify vulnerable regions that are sitting on retrograde bed slopes, hence that might be prone to the marine ice sheet instability. For mountain glaciers, accurately mapping the bedrock topography is mandatory to estimate ice thicknesses, which are used to simulate the contribution of glaciers to sea level rise, but also to quantify the amount of freshwater resources stored in glaciers. Because of their large number, remote locations, and difficult access conditions, only scarce in-situ data exists for bedrock topography. Hence, while being a fundamental variable for glacier modeling, it remains poorly constrained at the time. Here, we present how the use of multiple sensors remote sensing techniques has helped us to unravel the hidden relief beneath glaciers and ice sheets. In Greenland and Antarctica, we use airborne gravimetry measurements along with multibeam and radar echoe sounder to map the bathymetry in fjords and below ice shelves. We show that the use of these new bathymetric products help us to understand the retreat history of glaciers, revealing pathways for warm water, and contributes to better modeling ocean circulation up to the grounding lines of glaciers. For mountain glaciers, we mapped the ice velocity worldwide at an enhanced sampling resolution of 50 m, using massive cross correlation techniques on image pairs from both optical (ESA’s Sentinel-2; USGS/NASA’s Landsat-7/8) and radar imagery (ESA’s Sentinel-1a/b). Finally, we combine this mapping with airborne and ground penetrating radar to recover the ice thickness of all glaciers on Earth. These estimations reveal a different picture of the bedrock topography beneath glaciers, with a modified ice thickness distribution. Using these new estimations as initial state in the Open Global Glacier Model, we show the important impact on the evolution of freshwater resources, and specifically on the timing of the peak water.
Assessment of water resources conservation and sustainable management strategies in the Lower Mekong River Basin
Authors: Mohammed Ibrahim , Bolten John , Souter Nicholas , Shaad Kashif , Vollmer Derek
Published: March 2022

Uncertainties and indeterminate scope, divergent social values and stakeholder interests, and changing hydroclimatology in transboundary river basins are all factors that may complicate sustainable water resource management. To address such complex socio hydrological issues, we present an example of an integrated approach to assessing future sustainability challenges in their social, hydrological, and ecological dimensions using a case study from the Lower Mekong basin. Our study area here is the combined basin of the Se Kong, Se San, and Sre Pok (3S) rivers which deliver approximately 20% of flow to the Mekong River system. We used a mixed methods approach to analyze potential impacts of climate change on regional hydrology, the ability of dam operation rules to keep downstream flow within acceptable limits, and the present state of water governance in Laos, Vietnam, and Cambodia. Our results suggest that future river flows in the 3S river system could move closer to natural (i.e. pre-development) conditions during the dry season and experience increased floods during the wet season. This anticipated new flow regime in the 3S region would require a shift in the current dam operations, from maintaining minimum flows to reducing flood hazards. Moreover, our Governance and Stakeholders survey assessment results revealed that existing water governance systems in Laos, Vietnam, and Cambodia are ill-prepared to address such anticipated future water resource management problems. Our results indicate that the solution space for addressing these complex issues in the 3S river basins will be highly constrained unless major deficiencies in transboundary water governance, strategic planning, financial capacity, information sharing, and law enforcement are remedied in the next decade. This work is part of an ongoing research partnership between the National Aeronautical and Space Agency (NASA) and the Conservation International (CI) dedicated to improving natural resources assessment for conservation and sustainable management.
Stochastic mechanical analysis of the stress field in a 3D thrust fold
Authors: Adwan Anthony , Maillot Bertrand , Souloumiac Pauline , Barnes Christophe , Leturmy Pascale
Published: March 2022

Knowledge of the in-situ stress state is a key factor for any subsurface site characterization and for safe underground geotechnical exploitations. Despite the huge progress in estimating the stress field, understanding the state of stress is still a tedious and challenging endeavor due to incomplete data and sparse information. Moreover, the cost of performing stress measurements is quite elevated while the procedure is delicate and time consuming. Thus, the importance of utilizing geomechanical models for a wider stress evaluation.

We conduct a sensitivity analysis of the stress field with respect to rheological parameters in a kilometric scale thrust fold using a 3D numerical implementation of the theory of Limit Analysis (LA). LA searches for the exact loading force at the onset of failure by bounding it through optimization using a kinematic (upper bound) and a static (lower bound) approach. Elastic parameters are not required, and we only adopt the Coulomb failure criterion characterized by a friction angle and a cohesion.

The 3D geological prototype created, is inspired from the north eastern Jura setting, northern Switzerland, and corresponds to the lateral termination of a partially buried fault cored anticline. It is formed by five material layers with different Coulomb parameters and two different décollement levels. We perform a parametric study by varying the friction angle of the bulk materials, the faults and the shallow décollement.

Our simulations, show various stress distribution patterns depending on the uncertainties related to fault and decollement friction angles. This implies different model behaviors and distinct rupture geometries. However, we identify in particular a stress shielded layer presenting low stress values independently of the parametric variations. Comparing our results with a 2D approach consolidates our findings and highlights the importance of 3D modeling. Finally, we perform a stress analysis of several boreholes taken at various locations. We represent each borehole by an average stress profile with its respective standard deviation. In doing so, we are transforming the parametric variations into stress logs reflecting our uncertainties. This process reveals in particular a counter-intuitive vertical stress decrease with depth near activated blind faults. We argue that this observation is related to material uplift in a compression regime and is only possible for a restricted blind fault.

The aim of this study is to evaluate the possibility of performing real stress data inversion in order to both predict stresses away from the measurements, and determine ranges of compatible rock parameters.
Widespread changes in surface temperature persistence under climate change
Authors: Thompson David WJ , Li Jingyuan
Published: March 2022

The effects of extreme temperature events on ecosystems and society depend critically on the persistence of the event. But to-date relatively little work has systematically explored the response of such persistence to climate change. In this talk, I will explore the evidence for changes in surface temperature persistence in output from a range of numerical simulations, including large-ensembles of climate change simulations run on Earth system models and simplified models with varying representations of radiative processes and large-scale dynamics. Together, the results indicate that climate change is expected to be accompanied by widespread changes in surface temperature persistence. The changes are generally most robust over ocean areas and arise due to a seemingly broad range of physical processes. The findings point to both the robustness of widespread changes in persistence under climate change, and the critical need to better understand, simulate and constrain such changes.
Times associated with source-to-sink propagation of environmental signals during landscape transience
Authors: Tofelde Stefanie , Bernhardt Anne , Guerit Laure , Romans Brian
Published: March 2022

Sediment archives in the terrestrial and marine realm are regularly analyzed to infer past changes in climate and tectonic boundary conditions. However, contradictory observations have been made regarding whether short period events are faithfully preserved in stratigraphic record. For example, short period events were hypothesized to be non-detectable in terrestrially derived sediments offshore large river system due to buffering during sediment transport. Other studies, however, have detected signals of short period events in sediments that were transported along large river systems. We think that this apparent discrepancy is related to the lack of a differentiation between different types of signals and the lack of distinction between river response times and times related to signal propagation.

To overcome these issues, we propose to define environmental signals more generally as “a measurable change in any sedimentary parameter of interest through time that can be linked to an environmental change” and to further group signals in sub-categories related to hydraulic grain-size characteristics. Also, we review the different types of ‘times’ and suggest a precise and consistent terminology for future use to clearly distinguish times of landscape response from times of signal transfer. We compile and discuss factors influencing the times of signal transfer along sediment-routing systems, how those times vary with hydraulic grain-size characteristics, as well as consequences regarding signal preservation in stratigraphy.

Unravelling different types of signals and distinctive time periods related to signal propagation addresses the discrepancies mentioned above and allows a more comprehensive exploration of event preservation in stratigraphy – a prerequisite for reliable environmental reconstructions from terrestrially derived sedimentary records.
Towards a land surface model based on optimality principles
Authors: Mengoli Giulia , Harrison Sandy P. , Prentice Iain Colin
Published: March 2022

Plants take up water from the soil via roots and release it into the atmosphere through stomata; uptake of CO2 from the atmosphere also proceeds through the stomata, implying tight coupling of transpiration and photosynthesis. We distinguish leaf-level (biochemical and stomatal) responses to external stimuli on different timescales: fast responses taking place over seconds to hours, and longer-term (acclimation) responses taking place over weeks to months. Typically, land-surface models (LSMs) have focused on the fast responses, and have not accounted for acclimation responses, although these can be different in magnitude and even in sign. We have developed a method that explicitly separates these two timescales in order to implement an existing optimality-based model, the P model, with a sub-daily timestep; and, thereby, to include acclimated responses within an LSM framework. The resulting model, compared to flux-tower gross primary production (GPP) data in five “well-watered” biomes from boreal to tropical, correctly reproduces diurnal cycles of GPP throughout the growing season. No changes of parameters are required between biomes, because optimality ensures that current parameter values are always adapted to the local environment. This is a clear practical advantage because it eliminates the need to specify different parameter values for different plant functional types. However, in areas with large seasonal variations in moisture variability, the model does not perform well. Here we address the issue of soil-moisture controls on GPP, which is a challenging issue for LSMs in general. We note two problems: an error in magnitude, and an error in shape. The model tends to overestimate GPP in dry areas because it does not consider the effect of low soil moisture (as opposed to atmospheric dryness) on photosynthesis; and it does not simulate the ‘midday depression’ that is observed under very high vapour pressure deficits. Moving beyond commonly used (empirical) water-stress formulations, we have incorporated soil moisture limitation on photosynthesis in the sub-daily P model. The main idea is to control GPP via hydraulic limitation. The revised model firstly assesses the “demand”—the transpiration that would take place under well-watered conditions—then constrains the actual transpiration at a rate that does not exceed the canopy’s estimated hydraulic capacity. This transpiration rate is then used to obtain revised rates of stomatal conductance and GPP, “corrected” for water stress. Preliminary results evaluating the revised model’s performances against flux tower measurements at dry sites are encouraging, suggesting a route towards a parameter-sparse and globally applicable LSM.
Modernizing Canadian Geodetic Survey’s precise GNSS orbit and clock system
Authors: Goudarzi Mohammad Ali
Published: March 2022

To enable the new CSRS-PPP processing engine and online service to work in full multi-GNSS mode, and to provide high quality precise GNSS orbit and clock (POD) products to IGS and international geodetic community, Canadian Geodetic Survey (known as EMR) is modernizing his POD system. The new system is based on GipsyX and in-house software development and is replacing the current POD system. When becomes fully operational, the new POD system will produce multi-GNSS precise orbit and clock corrections with ambiguity resolution along with wide-lane and phase biases using zero-differenced, dual-frequency, ionosphere-free phase and code observations in RINEX 2 and 3 formats estimated in combined solution. The new system also benefits from advanced features such as removing observations and ground stations affected by ionospheric scintillations and earthquake, respectively, as well as real-time monitoring of estimated position time-series of ground stations, among others.
Asymptotic convergence of sampling uncertainty in a 100,000 member ensemble using an idealised model of convection
Authors: Tempest Kirsten , Craig George C. , Brehmer Jonas R.
Published: March 2022

The ensembles used to produce probabilistic weather forecasts are limited by the availability of computational resources. This can lead to large sampling error and poorly resolved ensemble distributions. Furthermore, the expense of large ensembles makes it difficult to determine how many members would be needed to achieve a desired level of sampling uncertainty. A 100,000 member ensemble from a 1-dimensional idealised prediction system which replicates the key processes of convection is developed to examine how sampling error of random variables converges with ensemble size. Distributions of the three prognostic variables, evolving over 24 hours of a free-run, are found to correspond to the three categories of distribution that were identified in a study of a 1000-member NWP ensemble, indicating that the idealised model can represent key aspects of the forecast uncertainty. Bootstrap samples from the 100,000-member distributions are used to obtain widths of the 95% Confidence Interval of various sampling distributions, as function of ensemble size n. For sufficiently large ensemble size, the confidence intervals were found to decrease proportional to n-1/2. This scaling is universal for the mean, variance, skewness, kurtosis and several quantile random variables. The sampling error depends on distribution shape and the random variable. Techniques using parameterisation and multiple small ensemble computations are also investigated as methods to allow convergence to be estimated using smaller ensembles.
A comparative analysis of approaches to expanding Canada’s Earthquake Scenario Catalogue
Authors: Rimando Jeremy , Hobbs Tiegan , Peace Alexander , Goda Katsuichiro
Published: March 2022

Canada’s earthquake scenario catalogue is a nation-wide collection of possible earthquake rupture scenarios that allows us to understand which populations and assets will be impacted by the rupture of particular faults (or their segments). In the past, scenarios were often generated on an ad hoc basis, when they were needed by practitioners. As new information from geologic, geomorphic, geophysical, and geodetic studies become available, it is possible to model additional earthquake rupture scenarios for inclusion in Canada’s earthquake scenario catalogue, which will be crucial to providing relevant seismic hazard and risk estimates to end users such as community planners and emergency managers. This is especially valuable in the seismically active intraplate regions of eastern Canada, where the seismic risk awareness, perception and, consequently, preparedness, is relatively low. In updating this catalogue, we employed different approaches to modelling earthquake hazard and risk scenarios using the Global Earthquake Model Foundation’s (GEM) OpenQuake Engine. We conducted a ‘known events’ approach, which involved modelling representative events for historical earthquakes and potentially active faults. We also implemented a ‘systematic risk-based’ approach, which involved disaggregating the seismic risk at certain locations into the relative contributions from different seismic source zones, and ranking the seismic risk for each census subdivision (approximately aligned with municipalities) across Canada. The goal of the ‘systematic risk-based’ approach was to mitigate the irregular coverage of the existing catalogue. We compare the nature of the two catalogues for one community, taking into account the ways these kinds of catalogues are used in Canada and elsewhere. Finally, we described the overall spatial variations in seismic risk, focusing on regions where seismic zones are close to densely-populated areas, such as the offshore BC region and Cascadia subduction zone in western Canada; and the Western Quebec, Charlevoix, lower St. Lawrence, and southern Great Lakes seismic zones in eastern Canada. 
Long-term trends of precipitation in Europe: a comparison across multiple datasets
Authors: Huth Radan , Vít Václav
Published: March 2022

Different types of climate datasets (station, gridded, reanalyses) and even individual datasets have been shown to differ in how they capture statistical properties of climate variables. Here we compare trends in precipitation totals in Europe between station data (taken from the ECA&D database), gridded data (E-OBS and CRU TS), and reanalyses (20CR, JRA-55, and NCEP/NCAR) for period 1961-2011, both annually and for individual seasons. Theil-Sen non-parametric trend estimator is used for the quantification of the trend magnitude; Mann-Kendall test is used to evaluate the significance of trends.

On the annual basis, station data indicate precipitation increases in northern Europe and decreases in southern and southeastern Europe. Whereas trends in the gridded datasets roughly agree with station data, although tend to overestimate them, reanalyses provide much more negative trends with a different geographical distribution. There is a tendency for reanalyses to overestimate precipitation in the beginning of the period at some places, whereas they underestimate precipitation near the end of the period elsewhere. Particularly notable is an excessive, and likely unrealistic, drying trend in central, southwestern, and southeastern Europe in NCEP/NCAR in most seasons. Reanalyses thus do not appear to be suitable data sources for estimation of precipitation trends.  

Reasons for the disagreement are identified by a detailed examination of local or regional time series. The reasons are varied and depend on the specific type of dataset: Station series may suffer from inhomogeneities; gridded data may be affected by different sets of stations entering the interpolation procedure at different times; while reanalyses may be affected by different kinds of data being assimilated into them in different periods.
ENSO Atmospheric Feedbacks under Global Warming
Authors: Bayr Tobias , Latif Mojib
Published: March 2022

Two atmospheric feedbacks play an important role in the dynamics of the El Niño/Southern Oscillation (ENSO), the amplifying zonal wind feedback and the damping heat flux feedback. Here we investigate how and why both feedbacks change under global warming in climate models of 5th and 6th phase of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively) under a “business-as-usual” scenario (RCP8.5 and SSP5-8.5, respectively). The amplifying wind feedback over the western equatorial Pacific (WEP) becomes stronger in most climate models (on average by 8 ± 8%) as well as the damping heat flux feedback over the eastern and central equatorial Pacific (EEP and CEP, respectively) (on average by 18 ± 11%). The simultaneous strengthening of both feedbacks can be explained by the stronger warming in the EEP relative to the WEP and the off-equatorial regions, which shifts the rising branch of the Pacific Walker Circulation to the east and increases mean convection and precipitation over the CEP. This in turn leads to a stronger vertical wind response during ENSO events over the CEP that strengthens both atmospheric feedbacks. Further, we separate the climate models into sub-ensembles with STRONG and WEAK ENSO atmospheric feedbacks, as 2/3 of the models underestimate both feedbacks under present day conditions by more than 40%, causing an error compensation. Despite both sub-ensembles show similar changes in the mean state and ENSO atmospheric feedbacks, the ENSO dynamics in WEAK remain weaker relative to STRONG under global warming. Due to the more realistic ENSO dynamics, we postulate that the ENSO predictions of the models in STRONG should be more reliable. Finally, we analyze the relation between changes in ENSO amplitude and ENSO atmospheric feedbacks. We find that models tending to simulate an eastward shift of the wind feedback and increasing precipitation response over the EEP during Eastern Pacific El Niño events also exhibit an increasing ENSO amplitude.