bluuebunny/crossref_metadata_2025 huggingface dataset:
Drivers of sustained drought over the Arabian Peninsula in recent decades
Authors: Saharwardi Md Saquib , Dasari Hari Prasad , Ashok Karumuri , Hoteit Ibrahim
Published: February 2023

The predominantly desert region of the Arabian Peninsula (AP), comprising seven nations, is characterized by high temperatures and meager rainfall. Temperature, and dust activity, are exacerbating over the AP. In the current study, we found that drought frequency and severity have increased in the AP over the last two decades compared to the previous five decades. This recent drought intensification is characterized by dominant decadal variability in addition to what appears to be a long-term trend. The current droughts intensification appears to be driven by increased warming over the AP than by a decrease in local precipitation. The Atlantic Multidecadal Oscillation (AMO) cycle is strongly related to decadal drought variability, and the current unprecedented multiyear drought is associated with current positive phase of AMO. We developed a statistical model for future projections that indicates that the frequency and intensity of droughts over the AP are expected to decrease significantly in the coming year.
Insignificant but overlooked: Evaporative losses from small reservoirs in southern Europe
Authors: Aminzadeh Milad , Friedrich Noemi , Madani Kaveh , Shokri Nima
Published: February 2023

The application of agricultural ponds and small engineered impoundments (often < 0.1 km2 area) is growing globally to support livestock, irrigation, and local municipal and industrial demands during dry spells. However, evaporation diminishes the storage efficiency of these popular but often un-inventoried resources. This study provides a reliable framework for estimating global abundance of small reservoirs and associated evaporative hotspots under different climate change scenarios serving as a basis for future water management and planning. To show the applicability of the proposed method and the utility of the insights it provides, we use satellite data to identify spatio-temporal distribution of small reservoirs (~0.001 to 0.1 km2 area) in southern Europe (Italy, Spain, and Portugal) where irrigation heavily depends on water storage in agricultural ponds. While current estimates of evaporative water losses from small reservoirs often rely on pan measurements or Penman-type approaches with locally calibrated heat and mass transfer coefficients, we employ a physically-based model [Aminzadeh et al., 2018] that accounts for inherent reservoir characteristics (e.g., depth and light attenuation), and radiative energy storage within the water body to quantify energy balance and evaporation dynamics from small water reservoirs. Our preliminary results indicate that cumulative area of small reservoirs in the study area has increased from 518 km2 in 2000 to 614 km2 in 2020 (18.5% increase) with cumulative evaporative losses that may exceed 400 Mm3 during warm months (April to September). Although the estimated evaporative water loss looks negligible relative to the annual agricultural water use (< 2%), its significance could be gauged by societal impacts in these regions with chronic water stress problems or the cost of alternate water sources (e.g., desalinated water).ReferenceAminzadeh, M., Lehmann, P., Or, D. (2018). Evaporation suppression and energy balance of water reservoirs covered with self-assembling floating elements. Hydrol. Earth Syst. Sci., 22, 4015–4032.
Using self-organization to build climate-resilient ecosystems
Authors: Van de Koppel Johan , Cornacchia Loreta , Van de Vijsel Roeland , Van der Wal Daphne
Published: February 2023

Whether current-day ecosystems, often heavily modified by humans, can adapt to climate change is one of the most pressing scientific questions. Coastal ecosystems are at the forefront of climate impact, as salt marshes and intertidal flats may drown if these systems cannot follow sea level rise.
We developed a model to investigate how the emergence of complex creek networks during early salt marsh development affects the ability of marsh ecosystems to accumulate sediment, thereby compensating for sea level rise. This model is based on a scale-dependent feedback relation between vegetation growth and sedimentation, as plants locally block water flow, which then diverts to their surroundings. The model revealed that this self-organization process drives the emergence of a complex creek network of ever smaller creeks nested in between larger ones.
We used the model to analyze the importance of creek network complexity for the rate at which marshes accumulate sediment. The model highlights that in salt marshes, plant traits have a defining effect on the development of creek network complexity. Yet, it is the emergent effect of creek network complexity on sedimentation, rather than plant traits directly, that controlled sedimentation rates, determining the adaptive capacity of the marsh to sea level rise. Self-organized creek complexity proved a defining characteristic determining the resilience of this ecosystem to climate change.
We used our model to study whether restored coastal wetlands can be designed in such a way as to improve the adaptive capacity to sea level rise. We explored 14 realigned coastal wetlands and related the established, real-world creek network, being either entirely artificial dug-out channels or naturally formed creeks, to their potential, model-predicted sedimentation rate.
We observed that the developing channel networks in restored wetlands had much lower creek development and channel branching than natural systems, resulting in less efficient channel networks. Model simulations showed that if artificial creek networks deviated more from the creek pattern observed in natural ecosystems, or from the ones predicted from our model, they had lower sediment transport efficiency. Our findings suggest that if a more natural organization is followed when designing climate-proof coastal ecosystems, they are more resilient to climate change.
Tropical Cyclones in High-Resolution Global Climate Simulations with the IPSL Model
Authors: Bourdin Stella , Fromang Sébastien , Caubel Arnaud , Ghattas Josefine , Meurdesoif Yann , Dubos Thomas
Published: February 2023

The availability of a new icosahedral dynamical core (DYNAMICO) for the IPSL model was the opportunity to participate in the HighResMIP protocol. We present the results of four historical 1950-2015 atmosphere-only (forced SST) simulations at horizontal resolutions equal to 200, 100, 50, and 25 km. We compare them with two simulations that use the same configuration but were performed with the previous longitude-latitude dynamical core at 250 and 75km horizontal resolutions.
We use these simulations to perform the first assessment of Tropical Cyclones (TC) in the IPSL model. This evaluation is done across four resolutions, gathering methodologies from recent literature (Roberts et al., 2020 a&b; Moon et al., 2020; Chavas et al., 2017; Camargo et al., 2020; Bourdin et al., 2022).We first show that the results obtained with DYNAMICO compare favorably with the previous dynamical core of the IPSL model.Then, we analyze how increasing horizontal resolution from 200km to 50km improves the TC climatology. Our results align with the current expectation that frequency and geographical distribution get closer to the observation but that the intensity is still significantly under-resolved.In the highest-resolution simulation TC activity in the North Atlantic basin is well represented in terms of geographical distribution and inter-annual variability. However, regional biases remain, especially in the Western North Pacific, where there is a significant deficit in TC number and a shift of activity towards the east of the basin. These regional biases are robust with resolution but are not associated with any obvious climatological bias in the simulations.Finally, we study composites, TC size, and life cycles to document the physics of the model's TCs. They show that the model simulates realistic TC structures with primary and secondary circulations, an eyewall, and a warm core. TC size diminishes with resolution and less so with intensity.
We conclude that the IPSL model is able to simulate a realistic climatology of Tropical Cyclones at 25 km horizontal resolution, with maximum intensities limited by the current maximum resolution.
Evaluation of GRACE-derived Groundwater Signal Accuracy using Developed Statistical Framework
Authors: Akl Mohamed , Thomas Brian , Clarke Peter
Published: February 2023

The Gravity Recovery and Climate Experiment (GRACE) satellite has been widely used to monitor changes in terrestrial water storage anomalies (TWSA), which vertically integrate water storage changes from the land surface to the deepest aquifers. Isolation of groundwater storage anomalies (GWA) from TWSA requires information of other water budget components from auxiliary datasets, e.g., Land Surface Model (LSM) output, or in-situ/remotely sensed based data. Using auxiliary datasets to account for water budget components have revealed large biases and uncertainties, especially over regions with complicated hydrological processes, leading to accumulating errors in GRACE-GWA estimates. Comparisons of GRACE-GWA with in-situ observations permit evaluating how accurately we can isolate groundwater storage signals from TWSA. Goodness-of-fit (GOF) indices e.g., Spearman correlation, Nash-Sutcliffe Efficiency (NSE), and the Kling-Gupta Efficiency (KGE), are commonly applied hydrologic fit metrics that express similarity of time series. Such metrics are used in our study to compare GRACE-GWA estimations and in-situ observations. Our results showed that GOF indices failed to capture the different characteristics of GRACE-GWA timeseries. Spearman correlation requires a monotonic relationship, an assumption violated given the seasonal amplitudes of GRACE-GWA. Using a Pearson correlation is ill-advised given serial correlation and non-normality. NSE is biased and influenced by skewness and periodicity, which is given since the data is seasonal in nature. KGE is based on the assumptions of data linearity and data normality. Non-normality in GRACE-GW time series violates the implicit assumptions underlying KGE. The goal of this work is to improve interpretation and use of GOF metrics to validate GRACE-GWA estimates, highlighting the importance of assessing multiple GOF criteria beyond simply correlation often applied in GRACE studies. We show that a rigorous assessment of GOF enhances our ability to interpret GRACE-GWA.Acknowledgement:The researcher, Mohamed Akl, is funded by a full PhD scholarship from the Ministry of Higher Education of the Arab Republic of Egypt.
Evolution of shallow volcanic seismicity in the hydrothermal system of La Soufrière de Guadeloupe following the April 2018 Mlv 4.1 earthquake
Authors: Pantobe Laetitia , Burtin Arnaud , Chanard Kristel , Komorowski Jean-Christophe
Published: February 2023

La Soufrière volcano in Guadeloupe presents a seismo-volcanic (VT) activity associated with an active hydrothermal system. This microseismicity is principally shallow, produced by repeating earthquakes and triggered in swarms. Four recurrent families of VT repeaters are detected, including a main family accounting for more than 80% of the catalog since at least 2014.By stacking seismic waveforms of repeaters and using a temporary dense seismic network, we build a MASTER event with a high Signal-to-Noise Ratio (SNR) and we better constrain the absolute location of the main MASTER event. We report positive residuals between observed and predicted P-wave arrival times at nearly all stations, suggesting that the velocity model of the shallow part of the dome could be improved. We significantly lower these residuals by raising the P-wave velocity from 2 to 2.7 km/s and reducing the Vp/Vs ratio from 1.8 to 1.69, leading to an improved local velocity model.We then locate each VT event relatively to is own MASTER hypocenter and image the hydrothermal seismic activity along a sub-vertical conduit, beneath the Tarissan crater acid lake found at the summit of Soufrière.We also define a linear relationship between the peak amplitude of seismic events and their duration to obtain a pseudo local magnitude. The approach allows us to automatically and accurately estimate the magnitude of each event at the detection stage.The April 2018 earthquake (MLv 4.1), the largest since the last phreatic eruption in 1976-77, occurred 2 km northwest of the summit and generated an increase in the number of events and seismic energy released. This event also resulted in the emergence of a secondary significant VT family during the summer 2018, located above the first one. We show that the increase of shallow microseismicity, following the April 2018, is likely explained by dynamic damage of the hostrock below the dome, thanks to the analysis of the associated distribution of Coulomb stress variation and relative velocity variations.Finally, using a statistical approach, we detect periodicities in the number of events and the released seismic moment at La Soufrière. A dominant peak of seismic activity is observed in October-November and a second lower peak is detected in April.
Estimating the effect of past century global warming on agricultural topsoil carbon stocks
Authors: Poeplau Christopher , Dechow Rene
Published: February 2023

Estimating the effect of past century global warming on agricultural soil carbon stocks Christopher Poeplau, Rene Dechow Climate change is likely to affect soil organic carbon (SOC) stocks across the globe. Therefore, modelling efforts are undertaken to estimate the effect of future climate change on SOC stocks at different spatial scales and for various climate change scenarios. However, global average air temperature already increased by more than 1°C, which most likely already affected and affects global SOC stocks. Agricultural soils were observed to lose SOC in many parts of the world, which is partly interpreted as climate-driven. For deconfounding management and climate change effects, the latter needs to be estimated comprehensively. In this study, an established FAO framework, including the global SOC map as well as the RothC and MIAMI models, was used to model global agricultural topsoil SOC stock dynamics from 1919 to 2018 as attributable to climate change.On average, global agricultural topsoils lost 2.5±2.3 Mg C ha-1 with constant net primary production (NPP) or 1.6±3.4 Mg C ha-1 when NPP was modified by temperature and precipitation. These loss rates per °C were comparable to those observed in long-term geothermal warming experiments, which are also presented as a source of validation. Regional variability in SOC stock changes was explained by the complex patterns of alterations in temperature and moisture, as well as initial SOC stocks as major drivers of mineralisation and partly also C inputs in the models. On average, SOC losses have been a persistent feature of climate change in all climatic zones during the past century. This needs to be taken into consideration in reporting or accounting frameworks and halted in order to mitigate climate change and secure soil health. At the same time, the estimated climate-driven loss rates were partly much smaller than observed SOC losses from agricultural soils, indicating that other management-related drivers have been more important. 
Toward a realistic spatio-temporal description of GNSS station position time series
Authors: Gobron Kevin , Rebischung Paul , Barnéoud Julien , Chanard Kristel , Altamimi Zuheir
Published: February 2023

Today, Global Navigation Satellite Systems (GNSS) are widely used to study the kinematics of the Earth's surface and provide a fundamental contribution to the establishment of terrestrial reference frames. GNSS station position time series are derived by different analysis centres, which have achieved tremendous progress over the years. Nevertheless, GNSS station position time series remain polluted by stochastic variations – often called "noise" – which hinder their geophysical interpretation and contribution to terrestrial reference frames.Many studies have evidenced that these stochastic variations exhibit both temporal and spatial correlations. On the one hand, temporal correlations have been analyzed in detail and are known to be well approximated by a combination of white noise and flicker noise. The presence of flicker noise, whose origin remains unknown, is a major source of uncertainty in the estimation of long-term station positions and velocities. Consequently, most geodetic studies now routinely take these temporal correlations into account to avoid inferring unrealistically optimistic uncertainties. On the other hand, the stochastic variations in GNSS station position time series are also spatially correlated up to distances reaching a few thousand kilometres. The origins of these large-scale correlations, whether non or poorly-modelled ground deformation, positioning errors, or a combination of both, remain to be understood. Although this spatially correlated noise is known to obscure geophysical signals and affect the estimation of parameters of interest, it is hardly ever modelled or accounted for.This presentation introduces a realistic spatio-temporal correlation model for the stochastic variations in GNSS station position time series. Based on the analysis of position time series from the IGS repro3 campaign (over 1,300 stations) and the Nevada Geodetic Laboratory analyzes (over 11,000 stations), we first provide a diagnosis of the spatial correlations of the white and flicker noise processes separately. We then introduce three-dimensional spatial correlation models for each process. Finally, we discuss the implications of these spatio-temporal correlations on the uncertainty of long-term station positions and velocities.
GloFAS v4.0: towards hyper-resolution hydrological modelling at global scale
Authors: Grimaldi Stefania , Salamon Peter , Russo Carlo , Disperati Juliana , Zsoster Ervin , Carton De Wiart Corentin , Mazzetti Cinzia , Choulga Margarita , Moschini Francesca , Harrigan Shaun , Gomes Goncalo , Jesus Casado-Rodríguez , Ramos Arthur , Barnard Christopher , Hansford Eleanor , Prudhomme Christel
Published: February 2023

The Global Flood Awareness System (GloFAS, https://www.globalfloods.eu/) is a freely available flood forecasting service that is running fully operational as part of the Copernicus Emergency Management Service since April 2018. GloFAS offers a number of products, which are tailored to give an overview of the current and future hydro-meteorological situation. The GloFAS dataset includes medium-range and seasonal discharge forecasts, as well as storages (e.g. soil moisture, snow cover, lakes volumes) and main fluxes (e.g. surface and sub-surface runoff, actual evapotranspiration).The GloFAS dataset is generated using the open source hydrological model OS LISFLOOD (https://ec-jrc.github.io/lisflood/). OS LISFLOOD is a distributed, physically based rainfall-runoff model, which has been designed for the modelling of rainfall-runoff processes in large and transnational catchments for a variety of applications including flood simulation and forecasting; water resources assessment (drought forecast); analysis of the impacts of land use changes, river regulation measures, and other water management plans; or climate change analysis. The recent high-resolution global implementation of OS LISFLOOD allowed the delivery of the newest GloFAS set-up, namely GloFAS v4.0 which is foreseen to become operational in Q2 2023. This latest set-up has a 0.05 degrees resolution (~5km), 4 times higher than the previous version. Moreover, a crucial feature of the high-resolution implementation is the use of the latest research findings and remote sensing datasets to prepare the set of high-resolution input maps for the hydrological model. These maps allow to account more accurately for the morphological, physical, and land use characteristics of the catchments and thus enable an improved representation of the rainfall-runoff processes in different climates and socio-economic contexts at global scale.This presentation provides an overview (i) of the GloFAS v4.0 OS-LISFLOOD high-resolution implementation, (ii) of the model calibration incorporating almost 2000 gauging stations and a pragmatic regionalization approach, and (iii) of the technological solutions adopted to limit the computational time of global high-resolution simulations.OS-LISFLOOD, the high-resolution implementation maps, and GloFAS v4.0 are publicly available and they disclose opportunities for further analysis of the terrestrial water cycle fluxes and storages, and of the current and future state of global water resources.
Deformation and healing processes in the damage zone of a lower-crustal seismogenic fault
Authors: Michalchuk Stephen Paul , Dunkel Kristina , Ohl Markus , Menegon Luca
Published: February 2023

Coseismic fracturing of the lower crust is an effective mechanism for creating permeable pathways for fluids to infiltrate and interact with the host rock, thus effectively altering the rheology of otherwise anhydrous and strong lower-crustal rocks. Most of the fracturing and fragmentation that facilitate fluid infiltration occurs in the damage zone of seismogenic faults. In this study, we have focused on characterizing the damage zone adjacent to a lower-crustal pseudotachylyte (solidified frictional melt produced during seismic slip) to understand the fracture generating and healing processes during a seismic event.The Nusfjord East shear zone network (Lofoten, Norway) contains coeval pseudotachylytes and mylonitized pseudotachylytes that formed at lower-crustal conditions within anhydrous anorthosites. We present a micro- and nanostructural analysis of plagioclase grains in the damage zone of a natural pseudotachylyte using focused ion beam (FIB) prepared scanning transmission electron microscopy (S/TEM), electron backscatter diffraction (EBSD) analysis, electron microprobe analysis (EMPA), and SEM-cathodoluminescence (CL) imaging.The damage zone of the host anorthosite is characterized by a network of fractures with minimal offset, consistent with a pulverization-style fragmentation process. CL intensities differentiate primary plagioclase (plagioclase1), from secondary plagioclase neoblasts (plagioclase2) filling some of the fractures. Plagioclase1 grains often exhibit a diffuse CL intensity zonation from bright grain cores to a dark grey in healed cracks, while plagioclase2 have a uniform mid-tone grey CL intensity with dark grain boundaries. CL zonation in the plagioclase1 does not correlate with EMPA major element maps nor EBSD misorientation maps. TEM foils targeted key microstructure domains characterized by CL: (1) bright CL plagioclase1 core, (2) dark CL plagioclase1 in healed cracks, (3) transitional CL from bright to dark across a healed crack, and (4) plagioclase2 neoblast. Results from S/TEM show that the dark CL spanning the healed cracks is associated with a high concentration of crystalline nanoparticles. In contrast, bright CL is associated with a few scattered dislocations, no nanoparticles, and numerous dispersed Ba-Ti-oxide nanograins. The mid-tone grey CL plagioclase2 neoblast have the lowest dislocation density. Follow-up Transmission Kikuchi Diffraction (TKD) and NanoSIMS analyses on the nanoparticles in the healed cracks and the plagioclase1 grains immediately next to these cracks will help further elucidate the origins of the nanoparticles and the CL intensity zonation.
Using SOLA for investigating regional dynamics of flow at the top of the outer core
Authors: Rogers Hannah , Gillet Nicolas , Hammer Magnus , Finlay Chris , Mandea Mioara
Published: February 2023

Investigating the dynamics of liquid iron at the top of the core requires a difficult inversion process from magnetic field measurements, where traditional techniques do not allow for regional investigations or studies of Secular Variation (first time derivative of magnetic field, SV) on short-time periods. Improved data coverage and quality from satellite missions (particularly Swarm) have provided insight into short-period dynamics (such as jerks and waves), and improved understanding of localised features (such as jets near the tangent cylinder). However, there continues to be a need for new techniques for better spatio-temporal models of flow motions at the top of the core, especially for regional investigations.The aim of this work is to investigate regional dynamics at the core-mantle boundary (CMB) using the SOLA (Subtractive Optimally Localised Averages) methodology. This method allows us to create point estimates of radial field SV at the CMB by considering global satellite measurements. A time window is selected that allows a suitable trade-off between the desired spatial and temporal resolution of the local estimate.  The output is a localised average of radial field SV at a particular location on the CMB, along with an error estimate and a spatial resolution kernel. The SOLA methodology allows for a local estimate at any desired location directly at the CMB, which opens the way to investigations of regional dynamics, waves, and jerks. Producing localised-average estimates at the CMB bypasses many of the problems encountered when using only a subset of magnetic satellite data, downward continuing data, and models based on spherical harmonics.Finally, we discuss how the SOLA methodology can be incorporated into the PyGeodyn code to produce stochastic core flow models. This approach can provide additional information on wave-like flow motions at the top of the Earth’s core where these are most prominent, and permits new investigations of shorter period phenomenon. We present our on-going work and highlight considerations of the SOLA method for investigating SV and core surface flow modelling.
Multidecadal variation of Northern Hemisphere summer monsoonforced by the SST inter-hemispheric dipole
Authors: Li Jianping , Xue Jiaqing , Wang Bingchao , Yu Yongkui , Sun Cheng , Mao Jiangyu
Published: February 2023

The sea surface temperature inter-hemispheric dipole (SSTID) is an important variability mode of global SST anomalies, characterized by an anti-phase variation of SST between the two hemispheres. In this study, the decadal variation of the Northern Hemisphere summer monsoon (NHSM) is found to be strongly regulated by the SSTID, with positive (negative) phases of the SSTID corresponding to the strengthening (weakening) of NHSM. Both observation and SST-forced atmospheric model simulations suggest that the SSTID related thermal forcing modulates the NHSM by causing planetary-scale atmospheric circulation adjustments. Positive SSTID events lead to coherent increase (decrease) of surface air temperature over the entire Northern (Southern) Hemisphere, increasing the inter-hemispheric thermal contrast (ITC). As sea level pressure changes are just opposite to air temperature, the increase of ITC enhances the inter-hemispheric pressure gradient (Southern Hemisphere minus Northern Hemisphere), leading to the strengthening of summer monsoonal circulation and the increase of monsoon rainfall in the Northern Hemisphere.
Testing the self-healing capacity of sealant materials for subsurface storage applications.
Authors: van Noort Reinier , Yarushina Viktoriya
Published: February 2023

The secure subsurface storage of fluids, whether energy carriers such as hydrogen or wastes such as CO2 or nuclear waste, requires sealants that can ensure wellbore seal integrity over timescales of decades to millennia. Currently used sealants are typically based on Ordinary Portland Cement (OPC) technology, which results in brittle seals that may have limited ability to withstand aggressive chemical environments. These properties make it difficult to ascertain that such sealants will maintain seal integrity over the long lifetime of a subsurface storage reservoir, as temperature and/or pressure variations during operations; chemical attack; or geomechanical effects may induce leakage pathways through the seal, as well as along the interfaces between seal and wallrock, or between seal and steel, resulting in a loss of wellbore sealing integrity.Self-healing sealant materials can be a key technology for ensuring long-term seal integrity in underground storage applications. Such sealants should interact with leaking fluids so that when leakage pathways do form, these pathways are sealed rather than widened. We present experiments in which we aim to test the self-healing capacity of different sealants, particularly for CCS applications, by exposing a reproducible simulated leakage pathway to a flow of CO2(-bearing fluid) under in-situ conditions. Our simulated leakage pathway consists of a sawcut through a hardened sealant sample, propped with crushed, hardened sealant (though other materials can also be used). Until now, we have focused on OPC-based sealants with various mineral additives (such as olivine and brucite) that result in an increase in solid during carbonation; but other sealants not based on OPC, such as geopolymers, may also be tested. During flow exposure, the pressure drop across the sample is monitored to assess permeability changes. After the experiments, SEM is used to study microstructures and identify reaction products. The results of this experimental work are then used as input for numerical modeling studies that seek to simulate the observed interactions and can extrapolate obtained results beyond laboratory time and length scales. In our model, chemical alteration of the cement is coupled to mechanical deformation and fluid flow to capture the cement system's volume changes that will help mitigate leakages.
Aircraft observations of gravity wave activity and turbulence in the tropical tropopause layer: prevalence, influence on cirrus and comparison with global-storm resolving models
Authors: Atlas Rachel , Bretherton Christopher
Published: February 2023

The tropical tropopause layer (TTL) is a sea of vertical motions. Convectively-generated gravity waves create vertical winds on scales of a few to 1000s of kilometers as they propagate in a stable atmosphere. Turbulence from gravity wave breaking, radiatively-driven convection and Kelvin-Helmholtz instabilities stirs up the TTL on the kilometer scale. TTL cirrus, which moderate the water vapor concentration in the TTL and stratosphere, form in the cold phases of large-scale (> 100 km) wave activity. It has been proposed in several modelling studies that small-scale (< 100 km) vertical motions control the ice crystal number concentration (NI) and the dehydration efficiency of TTL cirrus. Here, we present the first observational evidence for this.We use 20 Hz data from the National Aeronautics and Space Administration (NASA) Airborne Tropical TRopopause Experiment (ATTREX) campaign to quantify small-scale vertical wind variability in the TTL and examine its influence on TTL cirrus microphysics. We develop an algorithm to classify turbulence, and long wavelength (5 km < λ < 100 km) and short wavelength (λ < 5 km) gravity wave activity, during level flight legs of at least 100 km. The most commonly sampled conditions are: 1) a quiescent atmosphere with negligible small-scale vertical wind variability, 2) long wavelength gravity wave activity (LWGWA), and 3) LWGWA with turbulence. Turbulence rarely occurs in the absence of gravity wave activity. Cirrus with NI exceeding 10 per liter are rare in a quiescent atmosphere, but about 25 times more likely when there is gravity wave activity and 50 times more likely when there is also turbulence, confirming the results of the aforementioned modeling studies.Our observational analysis shows that small-scale gravity waves strongly influence NI within TTL cirrus. Global storm-resolving models have recently been run with horizontal grid spacings between 1 and 10 km, sufficient to resolve some small-scale gravity wave activity. We use ATTREX observations to evaluate simulated small-scale (10-100 km) vertical wind power spectra from four global-storm resolving simulations from DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains (DYAMOND) that have horizontal grid spacings of 3–5 km. We find that all four models have too little resolved vertical wind at horizontal wavelengths less than 100 km, although the bias is much less pronounced in global SAM than in the other models. We expect that deficient small-scale gravity wave activity significantly limits the realism of simulated ice microphysics in these models.
IDS evaluation of the DORIS versions of the DGFI and IGN TRF2020 solutions
Authors: Moreaux Guilhem , Capdeville Hugues
Published: February 2023

In the context of the 2020 realization of the International Terrestrial Reference Frame, the three IERS Production Centers (DGFI, IGN and JPL) delivered three independent solutions from the contributions of the four space geodetic techniques (DORIS, GNSS, SLR and VLBI). Even if these three ITRF2020 realizations are based on the same input, they differ on several points such as the space geodetic techniques weighting, the coordinate time series discontinuities and on the modelling of the station displacements.In this study, we use the coordinate time series of the two hundred DORIS stations from 1993.0 to 2022.5 as benchmark to investigate the characteristics of the ITRF2020 and DTRF2020 realizations.After presentation of the overall performance of these two TRF realizations in terms of geocenter, scale and mean velocities, we assess the quality of the weekly restitution of the DORIS station positions by the DTRF2020, and ITRF2020 solutions. Then, we make benefit of the one and a half year since the ending of the ITRF2020 time period to evaluate these two 2020 TRF solutions in terms of prediction of the DORIS station positions. Finally, we will estimate the impact of the DTRF2020 and ITRF2020 solutions on DORIS precise orbit determination.
Evaluating Vegetation Modelling in Earth System Models with Machine Learning Approaches
Authors: Swaminathan Ranjini , Quaife Tristan , Allan Richard
Published: February 2023

The presence and amount of vegetation in any given region controls Gross Primary Production (GPP) or  the flux of carbon into the land driven by the process of photosynthesis. Earth System Models (ESMs) give us the ability to simulate GPP through modelling the various interactions between the atmosphere and biosphere including under different climate change scenarios in the future. GPP is the largest flux of the global carbon cycle and plays an important role including in carbon budget calculations.  However, GPP estimates from ESMs not only vary widely but also have much uncertainty in the underpinning attributors for this variability.  

We use data from pre-industrial Control (pi-Control) simulations to avail of the longer time period to sample data from as well as to exclude the influence of anthropogenic forcing in GPP estimation thereby leaving GPP to be largely attributable to two factor - (a) input atmospheric forcings and (b) the processes using those input climate variables to diagnose GPP. 

We explore the processes determining GPP with a physically-guided Machine Learning framework applied to a set of Earth System Models (ESMs) from the Sixth Coupled Model Intercomparison Project (CMIP6). We use this framework to examine whether differences in GPP across models are caused by differences in atmospheric state or process representations. 

Results from our analysis show that models with similar regional atmospheric forcing do not always have similar GPP distributions. While there are regions where climate models largely agree on what atmospheric variables are most relevant for GPP, there are regions such as the tropics where there is more uncertainty.  Our analysis highlights the potential of ML to identify differences in atmospheric forcing and carbon cycle process modelling across current state-of-the-art ESMs. It also allows us to extend the analysis with observational estimates of forcings as well as GPP for model improvement. 
How to collectively engage in reducing the carbon footprint of a research lab?
Authors: Vidal Jean-Philippe , Berni Céline , Coquery Marina , Devers Alexandre , Gauthier Leslie , Lauvernet Claire , Masson Matthieu , Mimeau Louise , Turlan Martin ,   RiverLy Downstream team
Published: February 2023

This communication aims at testifying how individual commitments of researchers can be combined to engage a whole research lab – in this case INRAE RiverLy – in a carbon transition path. INRAE RiverLy is an interdsciplinary research unit for the management and restoration of river systems and their catchments. In 2020, a group of RiverLy people started questioning the downstream impacts of their research practices. An official internal action called RiverLy Downstream was thus launched to address these issues. A first lab-scale carbon accounting for the year 2019 was performed thanks to the GES 1point5 tool (https://apps.labos1point5.org/ges-1point5). It showed a large contribution of air travel to the total carbon footprint. Further carbon accounting for 2020 and 2021 however highlighted the even larger impact of purchases (equipment, consumables, etc.) thanks to newly implemented features in GES 1point5. An open “climate day” was organized in the lab in September 2022 for (1) raising awareness through a general-public-oriented tool, (2) provide live feedback from other research labs engaged in a carbon transition, and (3) collectively identify propositions of local actions on different themes: purchases, travels, premises, computing, food, and research activities. These propositions fed a lab-wide survey that will help defining a few carbon footprint reduction scenarios based on their social acceptability. These scenarios will then be submitted to the lab board for implementation. The whole process benefited from rich interactions with INRAE national to regional strategy for reducing its environmental footprint (https://www.inrae.fr/en/corporate-social-responsibility-inrae), and with the French national initiative Labos1point5 (https://labos1point5.org/).
Coastal marine X-band radar bathymetry and current mapping
Authors: Lund Bjoern , Curcic Milan , Graber Hans , Haus Brian , Horstmann Jochen , Williams Neil
Published: February 2023

This presentation studies coastal marine X-band radar (MR) bathymetry and current measurements made in Monterey Bay, California, during the Coastal Land–Air–Sea Interaction (CLASI) experiment from Jul-Aug 2021. Numerous past studies have shown coastal MR bathymetry and, to a lesser extent, current measurements, but only a few of them have investigated their environmental limitations. Widely cited thresholds for MR ocean measurements are a minimum wind speed of 3 m/s and significant wave height of 0.5 m. Monterey Bay has a strong year-long diurnal sea breeze which also influences the wave height. As a result, wind and wave conditions fluctuated from favorable to unfavorable for MR ocean measurements on a quasi-daily basis. Here, we examine the limitations of MR bathymetry and current measurements as a function of wind and wave conditions, which were measured by an Air–Sea Interaction Spar (ASIS) buoy within the radar field of view. Unlike the popular cBathy algorithm, which adjusts its bathymetry results to the mean water level using ancillary tide gauge measurements and applies a Kalman filter that ingests several days of data per bathymetry estimate, we measure the bathymetry with a temporal resolution of 4 min albeit at a relatively low spatial resolution of 360 m. This allows MR-based measurements of tidal elevation, which we validate using data from the CO-OPS tide gauge in Monterey. The MR current measurements are validated using an ADCP that was mounted on the ASIS buoy. The novelty of this study lies in the comprehensive evaluation of the MR bathymetry and current measurements' environmental limitations. We show how their maximum range decreases for wind speeds under 4 m/s with a success rate of <20% for winds <2 m/s and <10% for winds <1 m/s. These findings can guide investigators who plan to include MR ocean measurements in their coastal field studies.
Effects of heat and drought stress and their co-occurrence on winter wheat yields in Germany under climate change
Authors: Becker Rike , Schauberger Bernhard , Merz Ralf , Schulz Stephan , Gornott Christoph
Published: February 2023

In our changing climate, heatwaves and droughts and their spatio-temporal co-occurrences are likely to intensify. This will inevitably challenge future agricultural production and calls for adaptation strategies to protect future yields. To find suitable climate adaptation strategies for Germany’s major staple crop - winter wheat - it is important to know how heat stress, drought stress or their compound effects drive wheat yield failures. The principal aim of this study is, therefore, to quantify the impacts of heat, drought, and their compound effects on winter wheat yields in Germany, in a spatially and temporally discrete manner.To address our aim, we develop a statistical crop-climate model for the time period 1991-2019 at the county level. We first create agroclimatic proxies for heat stress, drought stress and their compound effects and use these to construct a separate time series model with the addition of time-dependent interaction terms. Our approach constructs separate regression models for each county, based on common elements that allow for comparing and jointly interpreting individual models.Preliminary results show that more than 50% of Germany’s wheat yield variability can be explained by climate effects. Compound effects of heat and drought stresses are responsible for approx. 42% of the variability in Germany’s winter wheat yields. Drought stress alone explains approx. 7%, with higher impacts in the east of the country, and heat stress alone explains approx. 3% of the year-to-year yield variability, with higher impacts in the north-west of Germany. The results confirm the importance of compound effects and underline their dominating impacts on winter wheat yields, when compared to individual heat and water stress impacts – a finding which should guide future adaptation strategies. Furthermore, our study shows that heat stress is becoming increasingly important for wheat yield failure in Germany – alone and in conjunction with moisture stress.In conclusion, we suggest that climate change adaptation strategies for winter wheat in Germany should focus on combined measures against drought and heat extremes. While the increase of multi-stress resilience should be the main goal for entire Germany, north-western areas should prioritize strategies to increase heat resilience and eastern areas should prioritize strategies to increase drought resilience.
Boreal forests on fire - Decadal wildfire impacts on boreal forest microclimate
Authors: Helbig Manuel , Daw Lilly
Published: February 2023

Wildfire is the most important disturbance agent in boreal forests. These disturbances play a major role in the boreal forest carbon cycle. They lead to direct CO2 and CH4 emissions during the active fire phase and to long-lasting post-fire impacts on net CO2 and CH4 fluxes through changes in forest structure and in microclimatic conditions. For example, a forest’s ability to minimise differences between land surface and air temperature can preserve permafrost and can lower soil temperatures and thus soil respiration. Fire and post-fire succession are linked to diverse changes in ecosystem function and structure shaping land-atmosphere interactions and, thus, forest microclimate for decades after the disturbance event. However, the mechanisms behind changes in boreal forest microclimate remain uncertain hampering our understanding of carbon cycle impacts of wildfires. Here, we analyse surface energy balance observations from 17 eddy covariance flux tower sites across fire disturbance chronosequences in the North American boreal biome to identify the main drivers of post-fire changes in land surface-air temperature gradients. We use 102 years of observations to quantify winter and summer changes in important ecosystem properties such as evaporative fraction, aerodynamic conductance, and albedo following stand-replacing fire disturbances. Then, we link changes in ecosystem properties to decadal changes in surface-air temperature gradients.We find that the summer daytime surface-air temperature gradient increases after the fire disturbance indicating reduced ability to cool the land surface during the warm summer months. However, in the winter, the daytime temperature gradient becomes smaller. Decreased aerodynamic conductance contributes mainly to the post-fire surface heating in the summer while increasing albedo mainly explains winter cooling. Evaporative fraction increases initially in the first few decades after the post-fire disturbance. However, during drought years, the evaporative fraction declines rapidly. Our results provide important insights into fire impacts on microclimatic conditions and ground thermal regimes in boreal forests and highlight the reduced capacity of post-fire forests to reduce land surface temperatures during heatwave events. The findings have the potential to contribute to a better mechanistic understanding of post-fire permafrost thaw and soil respiration changes.
Crustal context of the Fagradalsfjall eruption: shear-wave velocity structure of the Reykjanes Peninsular from receiver function analysis
Authors: Jenkins Jennifer , Greenfield Tim , Rawlinson Nicholas , Agustdottir Thorbjorg , Hersir Gylfi Páll , Gudnason Egill Árni , Horálek Josef , Obermann Anne , Dahm Torsten , Milkerei Claus
Published: February 2023

Detailed investigation into local seismicity and geochemical analysis of erupted products from the 2021-22 Fagradalsfjall eruption has already provided new insights into the deep magma plumbing system beneath the Reykjanes Peninsular. Here we focus on producing a detailed regional-scale shear wave velocity model of the Reykjanes to provide wider scale crustal context for these results. Utilising seismic data from 105 stations operated by numerous groups on the peninsular from 2013 to present day, we use recordings of distant teleseismic earthquakes to observe P to s converted phases that provide insight into crustal structure through receiver function (RF) analysis. The total data set of nearly 3000 RFs is computed in several frequency bands. Small subsets of RFs from common backazimuths and epicentral distances displaying high waveform similarity are jointly inverted with surface wave dispersion measurements to produce approximately 300 individual velocity models across the area. These are migrated to depth within a 3D volume to define a single regional velocity model. Major interfaces such as the Moho and base of the upper crust are extracted to produce maps of peninsular wide variation. Computed velocity model inversion results are compared to  RF waveforms combined in multi-phase common conversion point stacks. We compare the velocity structure and interface depths extracted beneath Fagradalsfjall to magma depth estimates from geochemistry and potential structural changes hypothesised from local seismicity linked to the 2021-22 eruption.