bluuebunny/crossref_metadata_2025 huggingface dataset:
High resolution numerical modeling supporting the evaluation of the WaveSAX-2 power generation in the coastal area around the Civitavecchia port
Authors: Bonamano Simone , Peviani Maximo Aurelio , Burgio Calogero Giuseppe , Fersini Giorgio , Marcelli Marco
Published: February 2023

The progress and future commercial success of each wave energy device is linked to the fact that the technology, the local wave motion characteristic and environmental condition are suitable to exploit the available wave energy resources in a specific coastal area. In the last years, several wave energy converters have reached an advanced development stage, such as the WaveSAX-2, an oscillating water column device suitable for been installed in existing coastal structures. Considering that the device can be installed directly on the breakwater wall or even inside the caissons, the impact on the marine environment can be considerably reduced. The device at scale 1:5 has been already tested in the Civitavecchia port (north eastern Tyrrhenian sea, Italy) in 2018 and 2020 leading to the evaluation of the power matrix (i.e. the expected power production for each local wave condition).Thanks to the information obtained by the sea tests of the device, the wave energy potential exploited by WaveSAX-2 was evaluated, both in the offshore zone and in proximity of the Civitavecchia harbor structures, using the Mediterranean wave reanalysis product distributed as part of Copernicus Marine Service catalogue.In the area around the Civitavecchia port, the main characteristics (height, period, direction) of the wave motion and the potential energy production of the device have been computed using the SWAN model that allows to obtain a high spatial resolution in the coastal zone. The model was successfully validated with wave data collected in 2017 and 2018 using an ADP instrumentation mounted within the Barnacle structure at 20 m depth in the northern area of Civitavecchia port.The model results show that the highest energy levels are located in the northern and central part of Civitavecchia port where the breakwater structure has highly reflective features. These values resulted even greater than the energy found offshore. The southern part of the breakwater, which is protected by tetrapods with low reflective capacities, is instead characterized by lower values of wave energy. The study also highlights the improvement in the generation of the WaveSAX-2 due to the capacity of the new turbine to have a better efficiency in the exploitation of the lowest waves which are the most frequent ones in the study area.The work demonstrates that high spatial resolution numerical modeling is a fundamental tool to analyze and accurately predict the wave energy potential exploitable by wave energy converters (WEC) in coastal areas affected by the presence of port structures. It also represents  a powerful tool for the optimization of the device array design, leading to maximize the energy production and minimize the environmental impact in the area.
Surface and subsurface hydrology of a high-altitude catchment in the Trans-Himalayan region of Ladakh, India
Authors: Soheb Mohd , Bastian Peter , Nüsser Marcus , Schmidt Susanne , Singh Shaktiman , Kaushik Himanshu , Ramanathan Alagappan
Published: February 2023

In the cold-arid Trans-Himalayan region of Ladakh, cryospheric meltwater plays a critical role for irrigated agriculture and local livelihoods. Despite the vital importance of reliable water supply under conditions of ongoing climate change, the relative contributions from glaciers and seasonal snow cover melt, together with permafrost thaw to surface and subsurface discharge are largely unknown due to the lack of in-situ data and local hydrological modelling. This study attempts to improve the understanding of regional hydrology, based on the case study of Stok catchment, where snow and glacier meltwater feeds a village of more than 300 households. We quantified long-term (2003-2019) surface and subsurface flow using a distributed temperature index and coupled surface/subsurface flow models forced by daily in-situ, meteorological, satellite and reanalysis data. These models were calibrated with the measured discharge data from two summer periods (2018 and 2019) in order to better understand the characteristics of surface and subsurface hydrology of the catchment. We also investigated the specific contributions from the cryospheric components and from rainfall to the total flow, and water loss through sublimation. A decline in annual discharge with characteristic inter-annual variations was identified over the observation period with about half of the total accumulated flow through the subsurface. We found that snowmelt contribution was highest (~60%) followed by ice melt (~20%) and rainfall (~15%), whereas sublimation contributes to ~8% of the water loss in a hydrological year. The findings and approach of this study are important for applied hydrological studies and planning future water management strategies in the region of Ladakh.
Monitoring and quantifying CO2 emissions of isolated power plants from space
Authors: Lin Xiaojuan , van der A Ronald , de Laat Jos , Eskes Henk , Liu Zhu
Published: February 2023

CO2 emissions of power plants are often self-reported and calculated based on fuel consumption. The authenticity of CO2 emission data from power plants are preferable to be verified by independent measurements. Satellite observations can provide these CO2 emission observations from isolated power plants. However, there are two difficulties in the current top-down anthropogenic CO2 emission inversions, that is, (1) the anthropogenic CO2 emission signal is difficult to distinguish from the background of other emitted CO2, and (2) the temporal and spatial resolution of CO2 satellite observation data are currently limited. In this study, we focus on how to improve the accuracy of CO2 emissions using different methods and wind data estimates. We assess these emission estimates by comparison with USA EPA emission data, and identify and explore suitable cases elsewhere in the world. We have selected only isolated power plants for this study, to avoid complications because of multiple sources in close proximity. We first compare the Gaussian plume model and cross-sectional flux methods for estimating CO2 emissions of power plants. Then we examine the sensitivity of the emission estimates to possible choices for the wind field. For verification we have used power plant emissions that are reported on an hourly basis by the Environmental Protection Agency (EPA) in the United States. By using the OCO-2 and OCO-3 observations over the past four years we identified emission signals of isolated power plants and arrived at a total of 50 collocated cases involving 22 power plants. We found the wind field halfway the height of planetary boundary layer (PBL) yielded the best results. We found that the instantaneous satellite estimated emissions of these 50 cases and reported emissions display a weak correlation (R2=0.12). The correlation improves with averaging over multiple observations of the 22 power plants (R2=0.40). The method was subsequently applied to 106 power plants cases worldwide. We demonstrate that accurate estimation of power plant emissions can be achieved by monitoring from future satellite missions with more frequent observations.
Interpretability of negative latent heat fluxes from Eddy Covariance measurements during dry conditions
Authors: Paulus Sinikka Jasmin , El-Madany Tarek Sebastian , Orth Rene , Hildebrandt Anke , Reichstein Markus , Nelson Jacob A. , Carrara Arnaud , Moreno Gerardo , Mauder Matthias , Groh Jannis , Lee Sung-Ching , Migliavacca Mirco
Published: February 2023

Non-rainfall water can play a critical role in many ecosystems, but is understudied in most regions due to a lack of continuous, specialized measurements. One of the most commonly used techniques to quantify in situ ecosystem water fluxes is Eddy Covariance (EC). However, its use for the quantification of the two most famous non-rainfall water sources, dew and (radiation) fog, is limited because they often occur under humid conditions and nighttime stable stratification, making EC measurements particularly uncertain or non-valid.Here we describe how a non-rainfall water input observed under dry conditions, namely water vapor adsorption by soil particles (VWA), can be monitored using existing eddy covariance datasets, giving insight into this little-studied soil water source. Unlike dew and radiation fog, atmospheric stability is not a prerequisite for WVA. Instead, WVA is driven by a highly negative soil matric potential inducing water vapor to condensate already at relative humidity < 100 %. Therefore, EC measurements may be more suitable to detect and quantify this flux than for dew and fog.In this study, we test EC measurements for inferring WVA by comparing them to observations from large-weighing lysimeters, where the latter can be considered as a reference system for the measurement of WVA. Our aim is to explore the potential and limitations of the EC technique to detect and quantify WVA. We assess the quantitative and qualitative agreement between WVA estimated with the lysimeters and negative (downward) LE fluxes from EC. Our analysis uses four years of observations from a semi-arid tree-grass ecosystem and one year of a temperate agricultural ecosystem during the 2018 drought.Our results show that during dry conditions the water vapor gradient between the relatively humid atmosphere and the dry soil pores leads to WVA in both ecosystems. We find a decent agreement between the timing of fluxes detected as WVA with lysimeters and with EC instruments, but the magnitudes (i.e. the amount of flux) differ. Furthermore, we aim to characterize the conditions under which negative LE fluxes from EC measurements can and should be interpreted as WVA. This way, our study expands the possibilities to investigate the relevance of WVA as a non-rainfall water source and, more generally, sheds light on a mostly overlooked aspect of land-atmosphere interaction during dry conditions in different ecosystems.
The demise of Paratethys in the time of the Messinian Salinity Crisis: impact on Eurasian paleogeography and Mediterranean environments
Authors: Palcu Dan Valentin , Heida Hanneke , Sandric Ionut , Popov Sergey , Garcia Castellanos Daniel , Krijgsman Wout
Published: February 2023

During the Messinian Salinity Crisis (MSC), as the Mediterranean realm experienced partial desiccation, water levels in Paratethys, a vast waterbody in the middle of Eurasia, remained largely unaffected except in its easternmost domain, the Caspian basin, which experienced a severe partial desiccation. Still, its relation and role in the dynamics of the MSC are controversial.Here we reconstruct the paleogeographic evolution of the Paratethys region during the MSC. We  show that the Paratethys realm irreversibly fragmented into smaller basins (Dacian, Black Sea, Caspian) triggering a reorganization of the Paratethys watershed during the MSC. The Paleo-Don River, the main river flowing in Paratethys, was captured by the Black Sea basin enhancing the excess of water was spilled in the Mediterranean and affecting the hydrology of the Mediterranean during the Lago Mare phase of the MSC. The Caspian basin, isolated and deprived of major river inflows, became partially desiccated, experiencing a ~400m base level drop. Extensive canyons developed and expanded in the central-northern Caspian Basin forming a new river - the Volga, that would later capture the eastern watershed of the Paleo-Don and partially refill the Caspian basin. These findings reveal that the MSC had extensive, continental consequences: destabilizing the Paratethys realm and reorganizing the river networks of Eastern Europe. This paleogeographic reorganization and the shifts in freshwater budgets may represent a key piece of the puzzle of the water balance in the Mediterranean basin during the MSC.
Dynamic reorientation of tidally locked bodies
Authors: Patočka Vojtěch , Kihoulou Martin , Čadek Ondřej
Published: February 2023

Planets and moons reorient in space due to mass redistribution associated with various types of internal and external processes. While the equilibrium orientation of a tidally locked body is well understood, much less explored are the dynamics of the reorientation process. This is despite their importance for assessing whether enough time has passed for the equilibrium orientation to be reached, and for predicting the patterns of TPW-induced surface fractures (true polar wander, TPW, is used here for the motion of either the rotation or the tidal pole). Here we present a simple yet accurate method to compute the reorientation dynamics of a tidally locked body. The method is based on assuming that during the TPW the tidal and the rotation axes closely follow respectively the minor and the major axes of the total, time-evolving inertia tensor of the body. Motivated by the presumed reorientation of Pluto, the use of our method is illustrated in several test examples. In particular, we analyze whether reorientation paths tend to be curved or straight when the load sign and the mass of the host body are varied. When tidal forcing is relatively small, the paths of negative anomalies (e.g. basins) towards the rotation pole are highly curved, while positive loads reach the sub- or anti-host point in a straightforward manner. Our results suggest that the Sputnik Planitia basin cannot be a negative anomaly at present day, and that the remnant figure of Pluto must have formed prior to the reorientation.  The situation is different for the icy satellites of Jupiter and Saturn. When the mass of the host body is relatively large, positive loads first move toward the center of the trailing or leading hemisphere, and reach the sub- or anti-host point only later, in a subsequent stage of TPW. The reorientation dynamics may have important consequences for the present location of some of the prominent features on the surfaces of icy moons. The custom written code LIOUSHELL that was used to perform the simulations is freely available on GitHub. V.P. and M.K. acknowledge support by the Czech Science Foundation through project No. 22-20388S.
Geometry and kinematics of the active structures along the Latakia Ridge (Cyprus Arc)
Authors: Vattovaz Michelle , Bertone Nicolò , Bertoni Claudia , Bonini Lorenzo , Camerlenghi Angelo , Del Ben Anna , Walker Richard
Published: February 2023

 
The eastern Mediterranean has been the locus of catastrophic earthquakes and related tsunamis (e.g., the 365 Crete and 1222 Cyprus earthquakes). The primary sources of these seismic events are structures related to the subduction of the Nubian Plate along the Hellenic and Cyprus arcs.  A detailed identification and description of the potential tsunamigenic sources are required as part of an assessment of earthquake and tsunami hazards. Here we focus on the Cyprus Arc region, in which the oceanic crust is still subducting beneath the Anatolian Plate in the west, whereas in the eastern sector, the oceanic crust has been completely subducted, and the lower plate consists of thinned continental crust. The rates of shortening are higher in the western sector than in the east. During recent decades, new data from extensive hydrocarbon exploration have allowed us to image structures that deform the seafloor and influence the shape of the recent basins in the eastern sector. The Latakia Ridge is the most prominent tectonic structure in the area. The present-day architecture of this ridge is the result of Meso-Cenozoic convergence followed by a transpressive phase related to the northward migration of the Arabian Plate. Therefore, the present geometry of the tectonic structure results from a complex interplay between reverse and strike-slip faults. Our reinterpretation of previously published seismic reflection profiles crossing the Latakia Ridge allows us to reconstruct the geometry of the main active faults and suggests their recent kinematics. Our findings could be crucial for the reassessment of seismic and tsunami hazards in the eastern sector of the Cyprus Arc. 
Risk assessment of Marathon reservoir spillway based on water level
Authors: Bessas Nikolaos , Partida Kalliopi , Illiopoulou Theano , Dimitriadis Panayiotis , Koutsoyiannis Demetris
Published: February 2023

The Marathon Dam is the oldest one in modern Greece located close to Athens and serving its water supply. Its reservoir has a capacity of 41 hm3. Several residential areas exist downstream of the dam, the nearest of which is just one kilometer away. Therefore, in the event of high reservoir spill (let alone dam failure), downstream local communities and properties are at considerable risk. In this work, we aim to assess the risk due to spill employing stochastic simulation of the reservoir water balance based on existing data. In addition, we attempt to derive operational rules to mitigate the risk of its downstream failures due to spill.
Decadal Climate Variability and Predictability with a High-resolution Eddy-resolving Model
Authors: Zhang Wei , Kirtman Ben , Siqueira Leo , Clement Amy
Published: February 2023

Current global climate models typically fail to fully resolve mesoscale ocean features (with length scales on the order of 10 km), such as the western boundary currents, potentially limiting climate predictability over decadal timescales. This study incorporates high-resolution eddy-resolving ocean (HR: 0.1°) in a suite of CESM model experiments that capture these important mesoscale ocean features with increased fidelity. Compared with eddy-parametrized ocean (LR: 1°) experiments, HR experiments show more realistic climatology and variability of sea surface temperature (SST) over the western boundary currents and eddy-rich regions. In the North Atlantic, the inclusion of mesoscale ocean processes produces a more realistic Gulf Stream and improves both localized rainfall patterns and large-scale teleconnections. We identify enhanced decadal SST predictability in HR over the western North Atlantic, which can be explained by the strong vertical connectivity between SST and sub-surface ocean temperature. SST is better connected with slower processes deep down in HR, making SST more persistent (and predictable). Moreover, we detect a better representation of the air-sea interactions between SST and low-level atmosphere over the Gulf Stream, thus improving low-frequency rainfall variations and extremes over the Southeast US. The results further imply that high-resolution GCMs with increased ocean model resolution may be needed in future climate prediction systems.
Development of a national-scale decision support system for the water sector in Germany
Authors: Andreas Marx , Friedrich Boeing , Christian Schulz , Rebekka Lange , Thomas Schnicke , Jan Bumberger , Georg Teutsch , Sabine Attinger
Published: February 2023

The Water Resources Information System for Germany (WIS-D) project aims to significantly improve the decision-making basis for actors in water management. The target group are expert users at water suppliers, authorities or institutions of the federal or state governments as well as the institutions of public enforcement (e.g. in the allocation of water rights). The aim is to support the current water balance management as well as the adaptation to climate change.WIS-D, startet in 2021, consists of two interacting platforms. The first platform (dialogue platform) ensures the professional exchange between practice partners and research and the co-production of knowledge. Here, in the circle of the stakeholder cooperation group with eight external institutions, the goals and steps defined in the project application were first discussed bi-laterally and, in a second step, in a workshop, and the stakeholder needs were recorded. For this purpose, information on required water balance variables, indicators and time scales was also requested. Stakeholder interest in climate-hydrology simulations was very high, e.g. for the allocation of water rights. The possibility of using the resulting data sets for WIS-D was contractually agreed. Additional stakeholder requirements, such as uncertainty information, were collected in the stakeholder process.The requirements and functionalities of the second platform (technical platform) were also defined in a co-production process by the stakeholders and scientists. Based on this, the first experimental prototype was developed and made publicly available at https://webapp.ufz.de/wis-d/ in August 2022. As a change to the original schedule, the stakeholders prioritized, for example, the possibility of regional evaluability in the online portal, so that this functionality, planned for the third project year, has already been integrated into the technical platform today. WIS-D is on its way to providing an uniform database on water balance components for past, present and future across Germany. This can be used to assess the trustworthiness of existing data sets. In addition, WIS-D can help to fill water management related data and information gaps.The contribution describes the stakeholder process, shows the functionalities of the technical platform, and discusses the challenges of WIS-D development.
Investigating geomagnetic jerks with Swarm: Using the spatial gradient tensor for flow modelling
Authors: Madsen Frederik Dahl , Whaler Kathy , Hammer Magnus , Holme Richard , Brown Will , Beggan Ciarán
Published: February 2023

The ESA Swarm mission has, with along- and across-track differences of the magnetic field measurements, made it possible to generate spatial gradients data of the geomagnetic field and its secular variation (SV). Inverting the SV data for core-surface flows allows us to investigate the Earth’s outer core with higher resolution than using vector component data.We invert for core-surface flow models directly from the spatial gradient tensor SV data, without the use of stochastic or numerical models, imposing flow equatorial symmetry, quasi- or tangential geostrophy, or band-pass filtering. We develop three different types of model, all damped to minimise spatial complexity and minimise acceleration between epochs. The first set is otherwise unconstrained, and different spatial regularisations are used. In the second set, we allow for torsional oscillations by relaxing the temporal damping on certain flow coefficients. The third set has differential damping on the equatorially symmetric and asymmetric flow components, in order to investigate the extent to which asymmetric flow is required to fit the data. We predict the intradecadal variation in length-of-day (LOD) from each model, and find that only the model which allows for torsional oscillations shows a good fit to the LOD data.The azimuthal acceleration of all three model types shows evidence of fast westward low-latitude waves at the core-surface.  During the 2017 geomagnetic jerk, there is an abrupt westward shift in these wave-features in all our models. Previous literature suggests that geomagnetic jerks may originate from Alfvén wave packets emitted from the inner-outer core boundary, propagating outwards. We suggest that the observed westward shift at the jerk epoch may occur when these wave-packets interfere with the waves at the core surface.Finally, we consider the use of spatial gradients from the CHAMP mission. Spatial gradients can be derived from along-track differences of the magnetic field from CHAMP, which allows us to compare the quality of core surface flow models from the CHAMP and Swarm missions. Our analysis suggests it is unlikely that CHAMP yields data of sufficient resolution to observe this proposed wave-interaction, showcasing the success of the Swarm mission.
Multi-physical controls on gas content in sediments of lake Kinneret, Israel, evaluated by acoustic applications
Authors: Katsnelson Boris , Uzhansky Ernst , Katsman Regina , Lunkov Andrey , Ivakin Anatoliy
Published: February 2023

Gassy aquatic sediments are abundant over the world. Multiannual CH4 gas content in shallow sediments of Lake Kinneret, Israel, was evaluated by acoustic applications. Experiments were conducted mainly over the intermediate-deep parts of the lake. Low-to-moderate frequencies wideband acoustic signal was emitted, when sound speed indicating a gas content, was evaluated based on the reflection coefficient. Both frequency dependence of  reflection coefficient and backscattering were analyzed.. The effect of the following factors affecting the dynamics of CH4 bubbles in aquatic sediments in the lake Kinneret, was investigated statistically: (1) Organic matter flux to sediment controlling CH4 production; (2) Its timing relatively to the date of the acoustic measurements, controlling CH4 bubbles dissolution; (3) Water depth affecting CH4 solubility, mechanical sediment properties, and ebullition from the sediment. Multiple regression analysis indicates that the organic matter supply to the lake sediments due to the crash of phytoplankton bloom in the lake, acts as a major control on the sediment gas content over the multi-annual period. The gas content is least sensitive to water depth, explained probably by the uniform organic matter deposition flux to the medium-deep parts of the lake, from where the ebullitions is unfeasible. [the work is supported by BSF grant 2018150].
A stochastic rainfall model with intensity dependent autocorrelations.
Authors: Bárdossy András , Anwar Faizan
Published: February 2023

The space-time behaviour of precipitation is very complex. The knowledge of the dependence structures in space and time is very important for the assessment of flood risks. There are many different models available for stochastic simulations of precipitation time series. Most of the models are constructed such that the simulated time series match the autocorrelation structure of the observations in time along with the reproduction of spatial correlations. However, both auto and spatial correlations are value dependent i.e., if it is the upper or the lower tail. High and low intensity values have different dependence structures which have a significant influence on simulated extremes in space. In this presentation, first indicator correlations are introduced to show the intensity dependence of precipitation both in space and time at various resolutions. Then, a stochastic simulator based on gradual change of the correlations for the values in different parts of the distributions is introduced. The idea is that value dependent correlation is changed in such a way that the overall values remains same as that of a reference but not when considering values in different sections of the distributions alone. The model is applied to a large number of German catchments with hourly temporal resolution. The results are carefully analysed and compared to classical approaches.
Evolution of discharge and stream temperature from past to future in a large European River basin
Authors: Moatar Florentina , Seyedhashemi Hanieh , Vidal Jean-Philippe , Diamond Jacob , Thiery Dominique , Hendrickx Frédéric , Maire Anthony
Published: February 2023

Both discharge (Q) and stream temperature (Tw) are the key factors affecting water quality and the suitability of instream habitats, which are expected to experience substantial evolutions due to climate change. However, the absence of continuous and long-term data of Tw at a large scale limits our understanding of the spatio-temporal variations of Tw and their control factors, like riparian vegetation, strahler order, hydroclimate.
The present study used a physically-based thermal model (T-NET), coupled with a semi-distributed hydrological model (EROS) using SAFRAN meteorological reanalysis data provided of Météo-France to reconstruct past daily Q and Tw over the 1963-2019 period for 52 000 hydrographic reaches of the Loire basin (100 000 km²), France. Three regionalized climate projections under several future emissions scenarios (available on the DRIAS portal: www.drias-climat.fr) were used to project future daily time series of these variables over the 2005-2100 period.
The results over the 1963-2019 period showed that the increase of the Tw was higher than those air temperature (Ta) in spring, summer and autumn for the majority of the reaches of the basin. Indeed, Tw increased for almost all reaches and all seasons (average = +0.38°C/decade) with the largest increase in the spring (Mar-May) (range=+0.11 to +0.76°C per decade) and in summer (Jun-Aug) (+0.08 to +1.02°C per decade). Highest spring and summer increases were generally found in the south of the basin (Massif Central and Limousin plateau) and in higher Strahler order where a larger increase in Ta (up to 0.67 °C/decade) and a larger decrease in Q (up to -16%/decade) occurred jointly.  
Depending on climate models, scenarios and seasons,future projections showed changes in seasonal flow and water temperature. Seasonal median flow over the basin would be between -40% and +35% for the middle of the 21st century (2040-2079) compared to the 1990-2019 period. For the end of the century (2070-2099), flow change would be between -53% and +73%. A clear increase in future Tw was also found with seasonal  median increases of +0.7 to +2.7°C in the middle (2040-2079) and of +0.8°C to +5.0°C,  at the end of the century (2070-2099).
These climate-induced changes in Q and Tw could help us to explain shifts in the phenology and geographical distribution of cold-water species. Moreover, they highlight that we should take vital actions for both adaptation and mitigation strategies. In this regard, we found that some of these climate change-induced impacts on Tw can be mitigated through the restoration and maintenance of riparian shading specially in small streams.
Integrated Xylem Water Isotopic Observations and Process-based Ecohydrological Model Simulations Reveal Species-Level Plant Hydraulics
Authors: Li Kevin , Kuppel Sylvain , Knighton James
Published: February 2023

Plant water use in hydrologic, land-surface, and earth system models is frequently estimated by a series of equations reliant on unknown model parameters controlling plant hydraulic function. Estimating these plant hydraulic traits is critical for accurate simulation of terrestrial water storage, flow paths, tree resistance to drought, and ultimately, ecosystem response to climate change. Despite the prevalence of δXYLEM observations, few studies have used δXYLEM to estimate plant traits numerical ecohydrologic models We calibrated EcH2O-iso, an isotopic-enabled, fully distributed ecohydrologic model, with δXYLEM observations of 30 Eastern Hemlock (Tsuga canadensis) trees across seven months. Calibrated values for maximum stomatal conductance, canopy light interception, and rooting depths were validated with independent datasets of latent heat flux, canopy light interception, and δXYLEM from a nearby hemlock stand. Results indicate significant correlations between tree diameter (DBH), topographic position, and the calibrated values of several vegetation traits. Our results demonstrate that δXYLEM data can be used to accurately parameterize plant traits; however, the locations and sizes of the sampled trees should be considered when upscaling measured or calibrated plant-traits from individual trees into larger horizontal scales.
The effect of cloud top cooling on the evolution of the Arctic boundary layer observed by balloon-borne measurements
Authors: Lonardi Michael , Pilz Christian , Akansu Elisa F. , Ehrlich André , Shupe Matthew D. , Siebert Holger , Wehner Birgit , Wendisch Manfred
Published: February 2023

The presence of clouds significantly affects Arctic boundary layer dynamics. However, the accessibility of clouds over the Arctic sea ice for in-situ observations is challenging. Measurements from tethered balloon platforms are one option to provide high-resolution data needed for model evaluation.The tethered balloon system BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere) was deployed to profile the boundary layer at the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), and in Ny-Alesund. A set of scientific payloads for the observation of broadband radiation, turbulence, aerosol particles, and cloud microphysics properties were operated to study the interactions in the cloudy and cloud-free boundary layer.Measurements obtained under various cloud conditions, including single-layer and multi-layer clouds, are analyzed. Heating rates profiles are calculated to validate radiative transfer simulations and to study the temporal development of the cloud layers. The in-situ observations display the importance of radiation-induced cloud top cooling in maintaining stratocumulus clouds over the Arctic sea ice. Case studies also indicate how the subsequent turbulent mixing can lead to the entrainment of aerosol particles into the cloud layer.
Atmospheric nonlinearities strong contribution to the skewed ENSO amplitude and phase transition
Authors: Vialard Jérôme , Gangiredla Srinivas , Lengaigne Matthieu , Voldoire Aurore , Izumo Takeshi , Huilyardi Eric
Published: February 2023

ENSO features prominent asymmetries, in terms of amplitude, spatial pattern and phase-transition between warm and cold events. Here we examine the contribution of atmospheric nonlinearities to ENSO asymmetries through a set of forced experiments with the CNRM-CM6 AGCM and the NEMO OGCM. Control experiments can reproduce the major atmospheric and oceanic asymmetries of ENSO, with stronger signals east of the dateline for strong El Niño events, and west of it for strong La Niñas. Ensemble atmospheric experiments forced by observed ENSO SST anomalies and their opposites allow diagnosing asymmetries in air-sea heat and momentum fluxes directly attributable to atmospheric nonlinearities. They indicate that atmospheric nonlinearities are largely attributable to nonlinearities in the rainfall-SST relation and act to enhance El Niño atmospheric signals east of the dateline and those of La Niña west of it. An ocean simulation where the non-linear signature of air-sea fluxes is removed from the forcing reveals that asymmetries in the ENSO SST pattern are primarily due to atmospheric nonlinearities, and result in a doubling of eastern Pacific warming during the peak of strong El Niño events and a 33% reduction during that of strong La Niña events. Atmospheric nonlinearities also explain most of the observed prolonged eastern Pacific warming into boreal summer after the peak of strong El Niño events. Overall, these results imply that properly simulating the nonlinear relationship between SST and rainfall in CGCMs is essential to accurately simulate asymmetries in ENSO amplitude, spatial pattern and phase transition. Finally, we discuss the inherent limitations to our two-tier forced approach.
Synoptic environment of meso-scale and convective-scale rainfall extremes in global storm-resolving models 
Authors: Fildier Benjamin , Roca Rémy , Fiolleau Thomas
Published: February 2023

Traditional climate models do not well represent mesoscale convective systems (MCS) nor the mesoscale dynamics that couple convective motions with the large-scale circulation: this makes the assessment of rainfall extremes in present and future climates often approximate. Conversely, an effective adaptation to the damage caused by meteorologic extremes must be based upon a refined understanding of the synoptic conditions that favor the occurrence of episodes of heavy rainfall with various durations and intensities.

Here we propose a refined analysis of the environmental dynamic and thermodynamic con- ditions in which precipitation extremes occur in the current tropical atmosphere, for two types of extremes: events corresponding to hourly extremes on kilometric scales, called convective ex- tremes, and events corresponding to extreme rain amounts accumulated over the MCS lifetime, called mesoscale extremes. These two categories of extremes on distinct scales are analyzed in a global storm resolving model, which resolves the relevant continuum of dynamics between convective and synoptic scales. MCS are detected and followed using a Lagrangian tracking algorithm, which permits to identify the large-scale conditions at the time of their initiation. We focus on two main objectives: (1) quantifying the degree of correspondence between these categories of extremes and the populations of MCS encountered regionally over the Pacific and Atlantic ICTZ, over Sahel, India and Amazonia, and (2) compare the following large-scale controls on MCS developement: low-level and mid-level wind shear, large-scale instability and surface convergence, the occurrence of extremes over land and ocean, and their distance of land MCS to the coast relevant for the role of sea breezes in low-level moisture advection and shear. We conclude by commenting on the role of surface forcing and shear in controlling the regional differences in extreme rain events on these two spatial scales.
Mesozoic intracontinental deformations of the northern North China Block in a multi-direction convergent setting
Authors: Lin Chengfa , Liu Shaofeng
Published: February 2023

Since Late Palaeozoic, the North China Block (NCB) experienced a unique tectonic process in which sequential plate subduction and collision took place around this once stable and rigid craton. Due to this multi-direction convergent setting and its small size, the NCB was characterized with intensive intracontinental deformation and associated depositional processes and magmatism during Mesozoic. However, conflicting debates on the timing and kinematics of the intracontinental deformations are still open to the geologist community and hamper the understanding of the driving forces. Our works focus on the syn-tectonic depositions, including syn-tectonic conglomerates and growth strata, in Mesozoic sedimentary basins in the Yanshan belt of northern NCB, and the high-precision zircon U-Pb geochronological data. Previously reported stratigraphic levels of regional unconformities and isotopic ages of igneous rocks in the Yanshan belt were also compiled in this study. Our results suggest that during Middle Triassic-earliest Jurassic (ca. 240-195 Ma), the northern NCB was dominated by nearly N-S compressional regime, leading to formation of large-scale E-W-trending thrust faults and basement-cored buckles. A significant magmatic lull was also witnessed within this period (ca. 210-195 Ma). This N-S crustal shortening was believed to be related with collision between the NCB and the Songliao-Nenjiang terrane along the Solonker suture. During Middle Jurassic-Early Cretaceous (ca. 172-135 Ma), the Yanshan belt underwent strong NW-SE contraction and gave rise to NE-SW-striking thrust faults, asymmetric folds, and reactivation of previous E-W thrust faults with prominent dextral component. Both deformation, deposition, and magmatism showed a westward younging trend in the Yanshan belt during Early Jurassic-Early Cretaceous (ca. 180-140 Ma), indicating their westward migration. However, magmatism turned to migrate toward east after that. All these lines of evidences could be integrated in a tectonic model with westward flat-slab subduction of the Paleo-Pacific/Izanagi plate beneath the East Asian continent. Early Jurassic witnessed an imported and profound transition from closure of the paleo-Asian Ocean to the subduction of the Paleo-Pacific Ocean plate.
Aerosol Optical Depth over China: effects of Meteorological and Anthropogenic Contributions
Authors: de Leeuw Gerrit , Kang Hanqing , Fan Cheng , Li Zhengqiang , Fang Chenwei , Zhang Ying
Published: February 2023

The Aerosol Optical Depth (AOD) over China has been increasing from the end of the 20st century due to a multitude of anthropogenic activities contributing to emissions of aerosols and trace gases. The effect of the implementation of a series of policy measures to reduce these emissions is clearly visible in time series of satellite-retrieved AOD. A first maximum was reached in 2007, followed by strong interannual fluctuations until 2011 after which the AOD started to decrease over some provinces in China. However, over many other provinces the AOD decrease did not set in until after 2014. The AOD decrease flattened around 2017/2018 where after it varied within 10%. Clearly, the 2013-2018 Clean Air Action Plan was effective in reducing the AOD, as also shown for PM2.5, but this reduction was not continued during the Three-year Action Plan for Clean Air implemented in 2018. To investigate the reasons for the AOD variation during the last decade, the satellite data were compared with AOD model data simulating only meteorological effects on the AOD. To this end, the model runs were made with emissions fixed to those in 2010, but with actual meteorological data. The model results show that the AOD can change by +10% or -10% due to meteorological influences, the comparison with satellite-derived AOD shows the contributions of anthropogenic effects to the AOD. This study was undertaken over 5 major regions over China, for the years 2010-2022, during which the overall AOD reduction varied between 22% (over the PRD) to 40% over the SCB, with substantial meteorological contributions. The AOD peak in 2014 over part of China was entirely due to meteorological influences. It is recommended to account for meteorological effects to reach the goals of future Action Plans.       
Consequences of drying-out of Lake Neusiedl on the GHG budget of the reed belt
Authors: Baur Pamela Alessandra , Maier Andreas , Zechmeister Thomas , Glatzel Stephan
Published: February 2023

Lake Neusiedl, a shallow brackish lake of Austria and Hungary, is the westernmost steppe lake of Europe with an area of ca. 320 km² and the second largest coherent reed population in Europe. Half of Lake Neusiedl consists of a wetland ecosystem dominated by Phragmites australis, which forms a seasonally varying mosaic of water, reed and sediment patches, is highly sensitive to climate variations and which we investigated here.Little is known about the effects of climate change on reed dominated wetlands and the contribution of central European reed belts as a source of greenhouse gases (GHG). The current ongoing drought periods at Lake Neusiedl affect especially the water balance but also the carbon fluxes in the reed belt. Therefore, we investigated the drought influenced carbon and water fluxes and their drivers of the reed ecosystem of a brackish lake over the last three years.We used the eddy covariance (EC) technique to continuously quantify the vertical turbulent GHG exchange between the reed belt and atmosphere. The EC observations have been conducted near Illmitz in the natural zone of National Park Lake Neusiedl from summer 2018 to now. For taking the reed development of the studied ecosystem into account, vegetation indices data were used.The annual CO2 emissions decreased by 95 % from 200.5 g C m-2 in 2019 to 9.2 g C m-2 in 2021. Gross primary production and ecosystem respiration both increased from 2019 to 2021. The annual emissions of CH4 decreased by 59 % from 9.0±1.0 g C m-2 in 2019 to 3.7±1.9 g C m-2 in 2021. The reed belt tended from a strong to a low carbon source if only the vertical flows are taken into account. One explanation is the decreasing water level in the lake between 2019 to 2021, which was followed by a drying out of the reed belt (≙ no water above surface) in the late summer of 2020 and a longer period in 2021. The second explanation is the increasing reed growth (in area and biomass) inside the reed belt which increased the photosynthetic rate. The vegetation indices like NDVI, EVI and LAI from the reed belt support this by an increasing tendency from 2019 to 2021. The third explanation is that due to the low water levels less (or almost no) lateral exchange occurred via channels between the reed belt and the open water areas of the lake in 2021 compared to 2019.The apparent disconnection between the open water area of Lake Neusiedl and the reed belt re-directs carbon cycles and ecosystem functioning.
Development, intercomparison and analysis of city emission inventories in support of independent verification of city greenhouse gas budgets
Authors: Denier van der Gon Hugo , Dröge Rianne , Super Ingrid , Droste Arjan , Brunner Dominik , Suter Ivo , Constantin Lionel , Perrussel Olivier , Sanchez Olivier , Chen Jia , Aigner Patrick , Kühbacher Daniel
Published: February 2023

The ICOS-cities PAUL project aims to support the European Green Deal by solving specific scientific and technological problems related to the observation and verification of greenhouse gas (GHG) emissions from densely populated urban landscapes. To this end, comprehensive city observatories, applying various in situ and ground-based remote sensing GHG measurement technologies, will be developed and evaluated in a relatively large (Paris), medium (Munich) and small (Zürich) city. A critical input for the optimal design of such observatories are complete, spatially explicit, state-of-the-art city emission inventories for greenhouse gases and co-emitted species. Currently the emission data available for European cities vary considerably in source sector completeness, spatial resolution, base year and temporal disaggregation. Our target resolution in the ICOS-cities PAUL project is 100 x 100 meter, hourly resolution for a recent year like 2018 or 2019 to avoid impact of the Covid-19 pandemic. Such data would allow evaluation of the city budget and more detailed district level budgets, which can support tailored climate action plans. For Paris (3 x 3 km) and Zurich (100 x 100 m), emission inventories are developed by respectively, AIRPARIF and EMPA in collaboration with the municipality of Zurich. The emission inventory for Munich is based on the downscaling of the 1 x 1 km TNO-GHGco inventory where key source sectors are stepwise replaced by bottom-up estimates by TUM and TNO. Here we harmonize source sectors and evaluate and intercompare the emission inventories of the three cities. We identify dominant source sectors and potentially missing sources, and determine ratios between GHG and co-emitted species necessary for source sector attribution. Furthermore, we compare the results against downscaled national reported emission data in line with the official reporting to UNFCCC, and draw conclusions on consistency between national scale and city scale inventories. Lessons learned will lead to the development of a more general methodology to provide city emission data to other European cities and, as part of the overall ICOS-cities objective, robust observation-based methods for quantifying city GHG emissions and sinks to assess the impact of city climate actions.
The evolution of the global population experiencing unprecedented exposure and its age of emergence.
Authors: Grant Luke , Thiery Wim , Vanderkelen Inne , Gudmundsson Lukas , Fischer Erich , Seneviratne Sonia
Published: February 2023

In climate change attribution, unprecedented magnitudes of extreme events can be defined on the basis of thresholds in the pre-industrial distributions of event magnitudes. This notion of unprecedented levels of climate change impacts has been extended toward the lifetime exposure to extreme events by evaluating exposure frequency. Unprecedented exposure to extreme events is assessed by comparing average lifetime exposure under different climate scenarios to an upper percentile of exposure in a pre-industrial climate. Here we combine simulations of climate change impacts under different climate forcing scenarios with country-level demography datasets to estimate the fraction of the global population experiencing unprecedented exposure to extreme events. This is done for 29 global mean temperature trajectories taken from the AR6 scenario explorer and multiple extreme event categories such as heatwaves, floods and droughts. Further, we assess the age of emergence at which birth cohorts reach unprecedented levels of exposure.