bluuebunny/crossref_metadata_2025 huggingface dataset:
Flooding Under Climate Change in Small Island Developing States
Authors: Archer Leanne , Neal Jeffrey , Bates Paul , Lord Natalie , Hawker Laurence
Published: March 2024

Small Island Developing States are a group of 57 island nations and territories which are some of the most at-risk places to the impacts of climate change globally, particularly from changes in hydrometeorological hazards such as flooding. Despite this, little research has quantified present day flood hazard and population exposure in small islands, let alone how this may change as global temperatures continue to rise. Until now, this was due to the insufficient data to produce high-resolution flood hazard and population exposure estimates for a wide range of possible scenarios at such a large scale. Following the release of Fathom’s Global Flood Model 3.0, in this work we combine global flood hazard estimates for coastal, fluvial, and pluvial flood hazard at ~30m flood model resolution to estimate present day population exposure to flooding across all 57 small islands. We also investigate how flood hazard and population exposure changes under three climate scenarios: two plausible climate change scenarios (SSP1-2.6 and SSP2-4.5), and a plausible worst-case climate scenario (SSP5-8.5). We assess how present day flood hazard and exposure differs across the island typologies, and how these are projected to change under the different climate change scenarios. We also compare population exposure with vulnerability metrics to explore how population exposure to flooding and vulnerability interact. The results of this analysis aim to improve understanding regarding the range of plausible estimates of current and future population exposure to flooding in Small Island Developing States. These results will help inform adaptation to more extreme flood risk in Small Island Developing States under current and future climate change.
Comparing TROPOMI and GEMS Observations for the Same Sun-Satellite Geometry 
Authors: Veefkind Pepijn , Leune Benjamin , van Geffen Jos , Hong Hyunkee
Published: March 2024

Together with the geostationary imagers over Southeast Asia (GEMS), North America (TEMPO) and Europe (Sentinel 4), TROPOMI and its follow-on low Earth orbit missions will establish the global air quality satellite constellation. The role of the low Earth orbit sensors in this constellation is twofold: firstly to provide the global coverage, including regions that cannot or will not be covered by the geostationary imagers, and secondly to facilitate cross-comparisons of the geostationary imagers, thereby serving as a travelling standard.With the availability of the GEMS data and the expected release of the TEMPO data, the development of novel methods to intercompare the geostationary and low Earth orbit data is timely. When comparing data from geostationary and low Earth orbit data, one important aspect to overcome is the difference in the Sun-satellite geometry of the observations for an area on Earth. When comparing measured radiances under different geometries, complex corrections are required, for example to deal with the directionality of the surface reflectance. The uncertainties of such corrections may be larger than the expected difference in the radiance between the geostationary and low Earth orbit observations.As the GEMS field of view includes the sub-satellite point at the equator, there is the unique opportunity for direct comparison when the TROPOMI nadir observations cover this point. In this case, observations of GEMS and TROPOMI with the same the same viewing geometry are available within maximum 30 minutes of each other. The time difference can be accounted for by interpolation, and/or by including a larger geographic area on the Earth in the intercomparison. As the orbital repeat cycle of TROPOMI is 227 orbits, there is an opportunity for direct comparisons approximately every 16 days. Such comparisons can include comparisons of the Level 1B radiances, reflectances, or fitted quantities such as slant column densities for different gases.In this contribution we will demonstrate the method using case studies of direct comparisons of radiance, reflectances and NO2 slant columns, as well as comparisons for different seasons.
Magnetosheath jets: an interdisciplinary perspective
Authors: Plaschke Ferdinand
Published: March 2024

Earth’s magnetosheath, particularly its region downstream of the quasi-parallel bow shock, is permeated by plasma jets. These are local enhancements in the dynamic pressure, bubbles of plasma that are typically faster and denser in comparison to the ambient plasma. While jets emanate from the patchy and rippled quasi-parallel bow shock or upstream foreshock region, they are able to cross the entire magnetosheath and impact on the magnetopause. There, they may trigger magnetic reconnection and magnetopause surface waves, thereby coupling into large-scale magnetospheric dynamics. Consequently, the effects of jets can be observed inside the magnetosphere and also from ground. Jets are conceptually highly interesting phenomena as they can be interpreted as coupling elements between different regions and vastly different scales. Interdisciplinary research has led to significant advances in our understanding of jets over the past decade. However, despite all the efforts, many basic and fundamental questions remain unanswered. We review some latest results and open questions in jet research, emphasizing the benefit of interdisciplinary approaches.
The Impacts of Hydrogen on Tropospheric Ozone and their Modulation by Background NOx
Authors: Bryant Hannah , Stevenson David , Heal Mathew , Sand Maria
Published: March 2024

A shift in our energy production is crucial to the control of global warming. This will occur as fossil fuels are phased out, following legislation created to reach the targets set out in the Paris Agreement. One of the possible sources for a low carbon energy landscape is renewable hydrogen. Whilst hydrogen represents an alternative energy store, it can leak from the system. Understanding the fate of leaked hydrogen is vital to quantify the implications of this energy transition. This study uses the atmospheric version of the United Kingdom Earth System Model to analyse the impact of hydrogen on the atmosphere. The model indicates that increased atmospheric hydrogen leads to an increase in tropospheric ozone concentrations. Ozone is a greenhouse gas and therefore there is an indirect atmospheric warming due to hydrogen emission through ozone. Understanding the relationship between hydrogen and the chemical ozone budget is therefore required to dissect how this warming occurs. We find that hydrogen increases ozone production, governed by the increased flux through the reaction of HO2 with NO. Future atmospheric nitrogen oxide concentrations are expected to decrease in the coming decades, under most climate scenarios. Understanding the relationship between hydrogen and background NOx concentrations is therefore crucial in determining the mechanisms of how hydrogen is expected to impact future atmospheres. We use the model to calculate the tropospheric global warming potential of hydrogen and how this is altered by changing background NOx. We find that this tropospheric GWP will stay relatively constant alongside decreases in ground level anthropogenic NOx.
Landscape properties, habitat dynamics, and the carbon storage potential of seagrass meadows in the Wadden Sea
Authors: Reents Svenja , Hommes Laura , Schildt Nele , Camillini Nicola , Sander Lasse
Published: March 2024

Vegetated coastal ecosystems of the Wadden Sea, such as salt marshes and seagrass meadows, are important habitats and provide various ecosystem services. Efforts to protect and restore these valuable coastal systems are currently paralleled with an interest to better understand and quantify their carbon sequestration potential. Intertidal seagrass meadows comprise an area of more than 20,000 ha in the Wadden Sea, which might lead to the assumption that significant amounts of carbon are stored in these ecosystems. At present, however, very little data exists on carbon storage and dynamics in seagrass environments in the German Wadden Sea. Seagrasses declined massively about a century ago, but over the last decades underwent a process of unassisted recovery in the Wadden Sea of Schleswig-Holstein (northern Germany). Nevertheless, the two seagrass species, Zostera marina and Zostera noltii, are still mostly absent in similar coastal environments in western Germany and in The Netherlands – providing an example for the potential to enhance both ecosystem quality and carbon storage capacity.In an ongoing study, we investigate characteristics of the tidal landscapes (e.g., surface elevation and geomorphology, adjacent landscape elements, and anthropogenic structures) and specific habitat properties (biomass productivity, sediment characteristics, hydrodynamic conditions, pore-water nutrients) at seven seagrass sites, located on tidal flats along dike-forelands of the North Sea coast of Schleswig-Holstein, northern Germany.The aims are to (A) deliver a first assessment of the current carbon stocks, (B) quantify intra-site differences in realized seagrass habitats, and (C) understand differences in parameters that locally drive or inhibit the long-term build-up of carbon in seagrass meadows and their associated sedimentary systems. In this presentation, we will show and discuss our first preliminary results and interpretations.
Jupiter's atmosphere through Juno's radio occultation experiments
Authors: Caruso Andrea , Gomez Casajus Luis , Buccino Dustin , Gramigna Edoardo , Parisi Marzia , Coffin Drew , Withers Paul , Zannoni Marco , Smirnova Maria , Galanti Eli , Kaspi Yohai , Tortora Paolo , Park Ryan S. , Steffes Paul , Bolton Scott
Published: March 2024

On July 31st, 2023 and September 9th, 2023, Juno performed the first studies of Jupiter’s atmosphere through radio occultation experiments since the Voyager and Galileo missions. These remote sensing experiments were conducted in a coherent two-way mode, where an uplink signal frequency was used as a reference for the downlink signals, at X and Ka band, transmitted back to the Earth.During these experiments, the geometry of Juno's trajectory was such that the spacecraft was occulted by Jupiter as seen from Earth, therefore the radio signal, transmitted by the probe towards the DSN station, travelled through both Jupiter’s atmosphere and ionosphere. As a result, the radio signal underwent a phase shift due to the effect of refraction. Therefore, the Earth's antenna recorded a signal with a frequency different from what would have been observed if the signal had propagated through a vacuum. This difference, called Doppler residual frequency, has been used to infer the density, pressure, and temperature profiles of Jupiter’s neutral atmosphere and the electron number density of its ionosphere.In the analysis of Jupiter’s atmosphere and ionosphere, where the assumption of spherical symmetry does not hold, the effect of oblateness cannot be neglected. Consequently, the radio data analysis cannot be performed by resorting to the traditional application of the Abel transform. Instead, a more suitable approach involves employing the ray-tracing technique.  This technique, based on the geometrical optics approximation, can also take into account the effects of zonal winds in retrieving the properties of Jupiter's atmosphere. Additionally, the use of multi-frequency link techniques allowed us to disentangle the contributions from dispersive and neutral media in the frequency shift.This study presents an analysis of the data collected during the inaugural Juno radio occultation experiments of Jupiter. Specialized software has been developed to analyse the data acquired from these Juno-Jupiter two-way radio occultation experiments. Preliminary results of this analysis are given in terms of ionospheric electron density and atmospheric pressure-temperature profiles.
Influence of polymer age and soil aggregation on microplastic transport in soil erosion events
Authors: Severe Emilee , Phan Le Quynh Nhu , Maqbool Ahsan , Surridge Benjamin , Halsall Crispin , Gómez José A. , Quinton John
Published: March 2024

The transport of microplastics within and across terrestrial ecosystems is a critical factor controlling plastic pollution in the environment. However, our understanding of these transport processes remains extremely limited. Particular uncertainty surrounds how the changes driven by aging of plastics, for example in surface roughness or hydrophobicity, affect polymer transport.  In this study we compare the rate of transportation of pristine and aged polystyrene microplastics in a simulated rainfall event providing the first empirical data describing these processes. Additionally, we quantified the proportion of both aged and pristine microplastics incorporated into soil aggregates after several wet-dry cycles and the influence wet-dry cycles had on microplastic mobilization. The results from this study will provide critical insights into the influence of polymer age on microplastic mobility and retention in terrestrial environments.  
Progresses in assessing the quality of the Copernicus Marine near real time Northeast Atlantic and Shelf Seas models application.
Authors: Ciliberti Stefania Angela , Alonso Axel , Amo-Baladron Arancha , Castrillo Lluis , Garcia Manuel , Escudier Romain , Levier Bruno , Gutknecht Elodie , Reffray Guillaume , Aouf Lotfi , Dalphinet Alice , Louise Louna , Aznar Roland , Sotillo Marcos , Cailleau Sylvain
Published: March 2024

Qualification and validation of operational ocean products are fundamental processes and vital part of the Copernicus Marine Service for evaluating added value of any new or upgraded release and for monitoring forecasting systems skills in operations. These have an important impact on both users and model developers, in providing a comprehensive understanding of forecasting systems reliability. As cross-cutting activity at production units’ level, and as providers of analysis and forecast ocean products for the Iberia-Biscay-Ireland (IBI) and Northwest Shelf (NWS) regions in the frame of the Copernicus Marine Service, we are continuing to incrementally evolve evaluation methods of forecasting products by improving our capacity in analysing ocean model data using newly available in-situ and satellite observations.In this presentation, an overview of today capacity in assessing operational ocean model products derived from the Northeast Atlantic and Shelf Seas regions model is presented, including evaluation of ongoing numerical experiments, with an outlook on future product quality evolution. Starting from the NARVAL tool, currently used by the IBI Monitoring and Forecasting Centre for assessing daily operational production of physical and biogeochemical variables, we show how new digital tools can support regional fit-for-purpose assessment and perform multi-model/multi-parameter/multi-frequency verification (with a particular focus on biogeochemical variables) by accessing, using, and interoperating operational products available in the target regions through the Copernicus Marine Data Store.This work presents the operational daily evaluation and monitoring of the IBI and NWS Blue and Green Ocean products, with a focus on recent systems upgrades and on forecast performances. Evolutions of product quality tools will include integration of new product types - like interim and multi-year regional datasets - with implementation of new metrics, and development of a new digital validation service where users (e.g., end users and intermediate users, including operational teams) will have access to NWS operational systems skills.
Constraining global mantle circulation models with global seismic observations
Authors: Sturgeon William , Ferreira Ana M.G. , Panton James , Davies J. Huw
Published: March 2024

In order to improve our understanding of mantle flow, we require a joint collaboration between all fields of Earth Sciences. Seismic tomography provides key information on the current state of the mantle and therefore can constrain mantle circulation models. We present high-resolution (degree-60) global models of frequency-dependent phase and group velocity measurements from huge a huge dataset of ~47 million Rayleigh and Love waves. These include fundamental mode measurements, which are sensitive to the uppermost mantle and up to 6th overtone, adding sensitivity to the transition zone, covering a period range of 16-375 s. We also present global models of mantle attenuation (degree-20), made from ~10 million Rayleigh wave amplitude measurements, including fundamental and up to 4th overtone measurements (35-275 s). All seismic maps presented also have associated uncertainty maps, which are essential for robust interpretation but also for multidisciplinary interpretations of mantle circulation models.We constrain 3D mantle circulation models, known as TERRA models, at the present day. In order to do this, we construct 1D profiles of velocities and density from a suite of TERRA models on a 2x2 degree grid. Forward modelling of each 1D profile using MINEOS provides global predictions of seismic observables at all seismic wave periods, including phase velocity and group velocity. A misfit can then be calculated between the seismic models and predictions from the suite of TERRA models. This provides constraints on which TERRA models are most Earth-like, which will improve our understanding of mantle flow.
Numerical implementation of ESMs: an additional source of uncertainty in climate prediction?
Authors: de Melo Viríssimo Francisco , Stainforth David
Published: March 2024

Modern research in climate science relies heavily on Earth System Models (ESMs), which are highly complex and nonlinear mathematical representations of the planet Earth. Because ESMs are too complicated to be tractable analytically, one must resort to computers in order to extract useful information from them. Numerically solving these models is, however, a non-trivial task, with two key practical consequences.
First, being complex and nonlinear, ESMs require the use of several numerical schemes and involve different computational strategies to accommodate for the multiplicity of scales and components present in such models. These numerical choices vary from model to model and are also dependent on the user needs, as well as the computing resources available to them.
Second, being chaotic means that its initial value problem is sensitive to the finest details in the model (e.g. initial condition), and so any future state can only be characterised as a distribution, requiring an ensemble of simulations instead of a single one. Hence, different numerical approximations could in principle lead to differences in the resulting distributions, particularly in shape and extreme values. This is important, as such numerical scheme dependence can cause ambiguity in our interpretation of future climate within a model. Despite that, this issue has been largely neglected in both climate and mathematical literature.
In this presentation, we will briefly review and discuss the use of numerical schemes in ESMs and individual components. Using a conceptual but low-dimensional representation of the climate system [1,2], we will then present a systematic study of how different numerical methods can indeed change the resulting climate distribution. In addition to the uncertainties from initial condition, parameter and model formulation, our results suggest a fourth level of “structural” uncertainty in climate modelling – in the numerical (or computational) implementation. This has implications to the design and interpretation of climate ensembles, suggesting that the computational formulation must be accounted as a source of uncertainty when producing climate distributions, particularly for high-end stakeholders such as decision makers.
 
References:
[1] de Melo Viríssimo, F. and Stainforth, D.: A low-dimensional dynamical systems approach to climate ensemble design and interpretation, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14755, https://doi.org/10.5194/egusphere-egu23-14755, 2023.
[2] de Melo Viríssimo, F., Stainforth, D. A. and Bröcker, J.: The evolution of a non-autonomous chaotic system under non-periodic forcing: a climate change example, Chaos, 34, 2024, http://doi.org/10.1063/5.0180870, 2024
On the use of standardized drought indices (SPI and SPEI) for assessing future climate change impacts on drought: introducing a dynamic approach  
Authors: Peres David J. , Bonaccorso Brunella , Palazzolo Nunziarita , Cancelliere Antonino , Mendicino Giuseppe , Senatore Alfonso
Published: March 2024

Drought is frequently monitored using standardized indices, such as the Standardized Precipitation Index (SPI) and the Standardized Precipitation-Evapotranspiration Index (SPEI). The latter was specifically designed to incorporate climate variability in terms of temperature. Consequently, by definition, it is more suitable for assessing variations in drought frequency and magnitude induced by climate change across various potential future scenarios. 

However, standardization presents a challenge when employing indices to evaluate the potential impacts of future climate change on drought. This is because, by definition, these indices are drawn from a standard normal random variable (null average and unit variance). The assessment of these impacts involves comparing occurrences in a future period and scenario with those in a historical control period. If the indices are separately calibrated for each period (one calibration for the future period and one for the control period), any differences observed may result solely from the sampling variability of a series drawn from a standard normal random variable. Numerous studies have assessed climate change impacts on droughts using this imperfect approach. Conversely, an alternative approach involves computing future indices using parameters from the control period. This represents a "worst-case scenario" as it overlooks potential climate change adaptation measures that could mitigate the impacts. To address this issue, our study introduces a dynamic approach wherein future changes are evaluated by computing climate normals using moving time windows. This approach enables an understanding of how impacts change with the timing of the implementation of adaptation measures. We apply this approach to Sicily and Calabria in Southern Italy, considering various climate change scenarios (Representative Concentration Scenarios). The results suggest that the region is likely to experience an increase in drought events due to climate change. These findings underscore the necessity for revised drought identification strategies that consider the non-stationarity in climate. 
Temporal and spatial analysis of mortality associated with landslides on São Miguel Island (Portugal) from 1900 to 202
Authors: Silva Rui Fagundes , Marques Rui , Zêzere José Luís
Published: March 2024

The São Miguel Island covers an area of 744.6 km² and has a total population of 133,390, distributed across six municipalities: Ponta Delgada, Ribeira Grande, Vila Franca do Campo, Povoação, Lagoa, and Nordeste. The island features two extinct volcanic systems and three active central volcanoes with calderas connected by two fissure volcanic systems. Two distinct seasons can be identified based on rainfall patterns: from October to March (wet season) and from April to September (dry season). Since the settlement of the island in the mid-15th century, there have been records of landslides, some with significant socio-economic impact. The analysis of the spatial distribution and temporal patterns of mortality associated to landslides was carried out using the NATHA (Natural Hazards in Azores) database for the period 1900–2020. Data collection involved the analysis of more than 55,500 newspaper specimens. A total of 236 landslides events were catalogued on São Miguel Island, which caused 82 fatalities. The municipality of Povoação accounted for 48 fatalities, approximately 59% of the total. Ponta Delgada reported 14 fatalities, Ribeira Grande eight, Vila Franca do Campo seven, Nordeste three, and Lagoa two. On São Miguel Island, an average of 0.7 fatalities per year were recorded, resulting in a landslide mortality rate of 0.35 (calculated as the ratio between deaths and total events). The events with the highest number of fatalities occurred on October 31, 1997 (29 fatalities) and on October 14, 1942 (7 fatalities). The annual mortality rate per decade reveals two distinct periods with higher values: 1930-1949 and 1990-1999. No fatalities were recorded from 1900 to 1929. The landslide mortality rate has a first increase in the 1930s and 1940s (≈0.1 fatalities/10,000 inhabitants). From 1950 to 1989, there was a decrease (≈0.02 fatalities/10,000 inhabitants), with a slight increase in the 1960s. The period from 1990 to 1999 has the highest mortality rate (≈0.26 fatalities/10,000 inhabitants). However, excluding the extreme event of October 31, 1997 from the analysis reveals that the 1990s had a mortality rate in line with the previous four decades (0.02 fatalities/10,000 inhabitants). Along the two first decades of the 21st century, the mortality rate increased again, maintaining a stable trend (≈0.05 fatalities/10,000 inhabitants). The data also indicates that males had a higher frequency of fatalities. The circumstances surrounding the incidents varied, with most fatalities occurring outdoors when individuals were on foot in rural areas. However, it is noteworthy that there were also fatalities inside houses in urban areas, emphasizing the diverse contexts in which these tragic events took place. This information provides valuable insights to temporal patterns and spatial distribution of landslide-induced fatalities on São Miguel Island.
Observation of Oxygen-18 in Ocean Waters in the Vicinity of Iceland 
Authors: Sveinbjornsdottir Arny , Olafsson Jon , Olafsdottir Solveig
Published: March 2024

The goal of the present project is to use oxygen-18 to map water masses North of Iceland. Here we report on findings from field campaigns carried out over the period from 1988 to 2019. The samples were collected on Icelandic vessel cruises from waters that currents bring from the south and from the north and are found west and north of Iceland.  An emphasis was placed on low salinity waters that characterize the Polar Water of the East Greenland Current. The data cover all seasons and a salinity range from 29.1 to 35.3.  The observations generally also include biogeochemical constituents: dissolved oxygen and the nutrients phosphate, nitrate, and silicate (Olafsson, Olafsdottir et al. 2010).   Oxygen isotope measurements were carried out at the Science Institute, University of Iceland. Prior to 2007 we used a Finngan MAT 251 Mass-spectrometer and extracted oxygen from the water by equilibrating degassed water with a small amount of CO2 gas (Epstein and Mayeda, 1953). After 2007 the measurements were performed on a continuous flow Delta V Advantage mass-spectrometer, with a Gas bench device. The accuracy of the measurements is better than 0.05‰. We examine the δ18O -S relationships for variations with seasons and time. The surface waters of the observed regions are seasonally productive but with different winter nutrient concentrations to support phytoplankton spring blooms. We examine variations in the seasonal δ18O-nutrient relationships. Epstein, S. and Mayeda, T.K. (1953). Variation in O18 content of waters from natural sources. Geochim Cosmochim. Acta 4:213-224. Olafsson, J., S. R. Olafsdottir, A. Benoit-Cattin and T. Takahashi (2010). "The Irminger Sea and the Iceland Sea time series measurements of sea water carbon and nutrient chemistry 1983–2008." Earth Syst. Sci. Data 2(1): 99-104.
Deriving NOx emissions of cities in Africa using the space-based TROPOMI instrument
Authors: Wei Nana , Marais Eloise A. , Lu Gongda
Published: March 2024

Surface concentrations of nitrogen oxides (NOx) are increasing at rates of up 10% per year in cities in Africa, as inferred with trends in long-term satellite observations of tropospheric columns of nitrogen dioxide (NO2). This is being driven by rapid population growth and urbanization in the absence of air quality policies. Models needed to inform air quality policies use out-of-date inventories for cities in Africa due to absence of detailed temporal and spatial information about emission and activity factors of sources unique to African cities. Here we apply a recently improved method of deriving city NOx emissions from satellite observations of NO2 that builds on the well-established rotation of each city NO2 plume along a consistent direction and selecting a single sampling area around the city centre to fit a modified Gaussian to calculate emissions. The improved method uses a more efficient fit routine and multiple sampling areas to eliminate subjective area selection and increase the success of deriving annual emissions from ~50% to 100%. Such an approach is ideal for African cities that have wide-ranging sizes due to the different development stages of countries and urban centres in Africa. Work is underway to quantify NOx emissions for more cities in Africa than has been achieved with global studies using 2019 observations of NO2 from the TROPOspheric Monitoring Instrument (TROPOMI). The resultant NOx emissions will then be compared to emissions estimates from widely used global (EDGAR, CEDS, HTAP) and regional (DACCIWA, DICE-Africa) inventories to assess shortcomings in inventories and the influence of these on designing evidence-based air quality policies and regulations.
Global vegetation dynamics using multiple satellite observations throughout the past four decades
Authors: Li Shaopeng , Wunderle Stefan
Published: March 2024

Terrestrial vegetation is a key component of the biosphere, which regulates global carbon, water and energy cycles. Meanwhile, global environmental change is rapidly altering the dynamics of terrestrial vegetation by functioning the Earth system and providing ecosystem services. Therefore, systematically monitoring global vegetation dynamics is critical to understand the basic biogeochemical processes, and their possible feedbacks to the climate system. Besides, characterizing spatial heterogeneity and temporal variation of surface albedo is also great importance to monitor land cover change and to determine energy exchange between ground and atmosphere. Remote sensing offers the only effective method for measuring and monitoring the vegetation dynamics, heterogeneity of albedo and its directional signature on regional and global scales. In this study, 4 km × 4 km GAC AVHRR data from extensive satellite data archive collected by the Remote Sensing Research Group at the University of Bern (RSGB) from 1981 to 2022 was applied to analyze albedo coupling with vegetation dynamics over global. The Simplified Method for Atmospheric Correction (SMAC) radiative transfer code was employed to do the atmospheric correction, and Ross-Thick/Li-Sparse-Reciprocal (RTLSR) kernel-driven model was applied using all contemporaneous NOAA and MetOp satellites data for removing anisotropic effects by means of the Bidirectional Reflectance Distribution Function (BRDF). Therefore, it is expected that the new generation of global Normalized Difference Vegetation Index (NDVI) and Albedo products could be produced from 1981 until 2022, which could potentially provide a long-term dataset for global climate change studies. Some preliminary evaluations showed that the new generation of NDVI product follows a generally similar trend to other products such as SPOT VGT, AVH13C1 NDVI, and Terra MODIS NDVI on selected validated sites. 
Future changes in tropical vertical velocity variance and precipitation variability
Authors: Xuan Zhenghe , Kroll Clarissa , Jnglin Wills Robert
Published: March 2024

Understanding precipitation variability on subseasonal-to-decadal timescales is important because of its influence on regional water resources and hydrological extremes. The response of precipitation to global warming can be understood in terms of a superposition of thermodynamic and dynamic effects. The former has been studied on a range of timescales, including ENSO variability and precipitation extremes, and is strongly constrained by Clausius-Clapeyron scaling. Changes in dynamics, however, modulate the overall change significantly and represent an important source of uncertainty in projected changes of hydrological cycle variability.Here, we investigate changes in the variance of vertical velocity in the tropics based on monthly outputs from the Community Earth System Model 2 Large Ensemble. We find a robust decrease in the tropical vertical velocity variance under the SSP3-7.0 scenario, even in periods where the underlying ENSO-related SST variance increases. This reduction in vertical velocity variance can be explained by the deepening of the troposphere, which increases the gross moist stability and thus the energetic demands for vertical motion. Finally, we investigate the influence of reduced vertical velocity variance on precipitation probability distribution and intensity.
Assessing heterogeneity of preferential soil water fluxes in situ with zero-tension microlysimeters in a temperate forest
Authors: Metzger Johanna Clara , Kleinschmidt Volker , Oldridge Truxton , Beyer Matthias , Eschenbach Annette
Published: March 2024

Macropore flow in structured soils constitutes an important component of soil water fluxes. This is especially true for unmanaged ecosystems. Preferential flow substantially affects ecohydrological separation, the partitioning of precipitation water into green (soil matrix, vegetation) and blue (recharge) water. Event characteristics, which are affected by changing climate, impact preferential flow; this, in turn, has an impact on ecohydrological separation and water resource availability. Though its importance is widely acknowledged since decades, it remains a challenge to measure preferential flow in soils. Additionally, small-scale heterogeneity of soil and environmental properties triggers spatial heterogeneity of preferential flow. In this study, we test the potential of zero-tension microlysimeters to measure preferential flow in a high spatial resolution. Zero-tension lysimeters have been used to sample soil water solution for chemical analysis. Methodical studies have shown that soil matric fluxes flow around zero-tension lysimeters and only gravity-driven water fluxes are captured. Using this to our advantage, we aim to develop a low-cost and simple method to sample preferential (gravity-driven) soil water fluxes in point measurements. This enables the implementation of a statistical design due to a high possible number of repetitions and the comparison with standard soil water status sensors due to similar scales. We are testing our lysimeters in a temperate mixed deciduous forest at Apelern, Lower Saxony, Central Germany. The soils are shallow and consist of weathered limestone intermingled with loess. By implementing transects starting from tree stems, we aim to cover a range of input fluxes and soil properties. We are combining lysimeters with measurements of soil water content, stand precipitation and soil properties. With our setup, we will be able to gain insight into the heterogeneity of preferential fluxes in situ and compare soil, stand and event impact factors to get a better understanding of the role of macropore flow in ecohydrological separation.
Tectonic advection controls drainage divide asymmetry patterns in the Longmenshan, SE Tibet, China
Authors: Gelwick Katrina , Wang Yanyan , Metzger Sabrina , Huppert Kimberly , Yang Rong , Willett Sean
Published: March 2024

The lateral movement of Earth’s crust through tectonic advection plays an important role in shaping topography in many active orogens worldwide. Numerical modelling and select field studies have shown that tectonic advection can alter topography and thereby create asymmetric drainage divides. Divide migration typically occurs opposite to the direction of tectonic advection, however, in many mountain belts, the wedge-tip propagation towards the foreland outpaces the rate of convergence, in which case the direction of topographic asymmetry should be reversed. We combine geomorphic and geodetic analyses with numerical models to test whether topographic asymmetry in the Longmenshan region of Southeast Tibet is dominated by advection of the crust from the ongoing India-Eurasia collision, movement of river base-level with the propagation of the thrust front into the Sichuan Basin, or other tectonic and climatic factors. We measure the magnitude and direction of drainage divide asymmetry using geomorphic metrics and compare these to horizontal GNSS velocities, which measure tectonic advection and shortening relative to the stable Sichuan Basin block. Geologic studies estimate that wedge-tip propagation toward the Sichuan Basin has been negligible since ~5-10 Ma.Our results show that drainage divide asymmetries in the Longmenshan and Bayankala tectonic blocks indicate a dominantly northwest divide migration direction relative to the underlying rock. This is opposite to the dominantly southeast-pointing GNSS rates and suggests that within-wedge shortening and southward surface advection are more important than wedge-tip propagation. These findings also indicate that topography in the Longmenshan and Bayankala blocks has already adjusted to the current kinematics. Inconsistencies in the signal can be explained by localized deformation and uplift from faulting and other small-scale transient adjustments in the river network, such as those caused by stream captures. We compare these results to a series of numerical model scenarios with varying advection and wedge-tip propagation velocities to discern the relative influence of tectonic advection and thrust-front dynamics on the region’s topography. Our study highlights the critical role tectonic advection plays in shaping topography on the Southeast Tibetan Plateau and it provides a comparative framework for distinguishing the relative rates of advection and wedge-tip propagation.
Climate Tipping Points and Optimal Emissions 
Authors: Titton Andrea
Published: March 2024

As the world temperature rises, due to carbon dioxide (CO2) emissions from human economic activities, the risk of tipping points in the climate system becomes more concrete. This risk affects the social cost of carbon, that is, the marginal damage of increasing carbon emissions. In this paper, I study the relationship between the risk of tipping, optimal emissions, and the social cost of carbon. To do so, I solve a social-planner integrated model (Hambel et al., 2021), with a stylised ice-albedo feedback in the climate dynamics (Ashwin & Von Der Heydt, 2020). I model a tipping point induced by the ice–albedo feedback and study how this affects optimal abatement. The tipping point affect temperature dynamics, and as a consequence optimal emissions, in three ways. First, it introduces a non-linear increase in temperature. Second, it makes positive temperature shocks more persistent than negative ones. Third, it introduces a jump in the abatement necessary to revert temperatures to the pre-tipping-point level. I show that, in this context, it is crucial not only to quickly reachnet-zero emissions, but to also flatten the emission curve to reduce the risk of tipping 
High obliquity favours centennial-scale variations in the carbon cycle
Authors: Legrain Etienne , Capron Emilie , Menviel Laurie , Wohleber Axel , Parrenin Frédéric , Teste Grégory , Landais Amaëlle , Bouchet Marie , Grilli Roberto , Nehrbass-Ahles Christoph , Silva Lucas , Fischer Hubertus , Stocker Thomas F.
Published: March 2024

Antarctic ice cores are a preferred climate archive to study global carbon cycle changes at multi-centennial timescales as they provide the only direct reconstructions of past atmospheric CO2 changes. Here we present a new atmospheric CO2 record from the EPICA Dome C ice core spanning Termination III (TIII) and Marine Isotope Stage 7 (MIS 7) (~260-190 ka). 203 ice samples were measured using a ball mill dry extraction system and gas chromatography at IGE. With a temporal resolution of about 300 years on average, our new record improves by a factor of three the existing CO2 record that had been measured on the Vostok ice core over this time interval. Based on our new record, we identified seven centennial-scale releases of atmospheric CO2, also referred as Carbon Dioxide Jumps (CDJ). Combining these new results with previously published ones, we evidenced that 18 of the 22 CDJs identified over the past 500 thousand years occurred under a context of high obliquity. New simulations performed with the LOVECLIM model, an Earth system model of intermediate complexity, point toward both the continental biosphere and the Southern Ocean as the two main carbon sources during CDJs connected to Heinrich events. Notably, the continental biosphere appears to be the obliquity-dependent CO2 source for these rapid events. For the first time, we demonstrate that the long-term external forcing directly impacts past abrupt atmospheric CO2 variations.
Modelling surface water and energy transfer in karstic mediterranean forests
Authors: Raynaud--Schell Brune , Demarty Jérôme , Etchanchu Jordi , Ollivier Chloé , Collet Léna , Kempf Jean , Limousin Jean-Marc , Marloie Olivier , Olioso Albert , Ourcival Jean-Marc , Simioni Guillaume , Leonardi Véronique
Published: March 2024

Droughts are a major factor in the vulnerability of Mediterranean ecosystems, particularly forest ecosystems, which are mainly located in karstic environments. Under the effects of global change, these environments are exposed to increasingly frequent and intense droughts. Recent ecophysiological and isotopic studies have shown that tree roots are able to feed deep enough in the epikarst to support transpiration during periods of water stress. However, the quantification of stocks and temporal dynamics are not yet fully established. This calls for the development of models adapted to the complexity of the environment, with the aim of improving our knowledge of both aquifer recharge and the hydric functioning of forests. The work carried out in this study goes in this direction. It aims to suggest, implement and test a SVAT-type model of energy and water exchanges at the soil-vegetation-atmosphere interface, adapted to Mediterranean forest environments in karstic zones. The modelling objective is dual: i) to jointly simulate the processes of diffuse infiltration into the soil (i.e. the superficial part of the root zone) and rapid infiltration into the network of karstic fractures (i.e. the deep part of the root zone); ii) to simulate the transpiratory and water extraction processes throughout the root zone. To do this, an adaptation of the SiSPAT model was developed and then deployed for the first time on two sites in the ICOS network, namely the forest sites of Font-Blanche (Bouches-du-Rhône, P.I. URFM) and Puéchabon (Hérault, P.I. CEFE). The results highlight the importance to represent both diffuse and preferential flows in SVAT modelling for karstic areas. It particularly shows that preferential infiltration builds up deep water reserves throughout the year. It helps to reproduce better observed transpiration by the plant canopy during periods of water stress. It also significantly affects the different hydrological components of the surface, e.g. runoff and drainage to the aquifers.
Simulating normal fault interactions during complex seismic sequences in the southern Apennines
Authors: Rodriguez Piceda Constanza , Mildon Zoë K. , Yin Yifan , Andrews Billy J. , Sgambato Claudia , van den Ende Martijn , Ampuero Jean Paul
Published: March 2024

Active faults with low extension rates can generate large magnitude earthquakes with severe damages, as exemplified in the southern Apennines (Italy) by the Irpinia earthquake (Mw 6.8) in 1980 and the Val D’Agri earthquake (Mw 7.1) in 1857. These earthquakes occur within a network of faults, and geological evidence (e.g. paleoseismic trenching) suggest that earthquake activity varies from decennial to millennial time scales on such fault systems. Therefore, improving our understanding and forecasting capabilities of seismic sequences in these areas is crucial. However, studying fault behaviour in slowly deforming regions can often prove challenging due to the long recurrence intervals and low slip rates of these faults, which results in limited instrumental, historical and paleoseismological records.To address this issue, we use physics-based numerical models, since they allow for controlled experiments that can span thousands of years with relatively low computational costs, thus they are valuable tools to investigate the causal dynamics between seismic events. Here, we model a system of NW-SE oriented normal faults in the southern Apennines, accounting for the variable slip rates and geometry of the faults. The study region is characterized by areas with variable number of across-strike faults, thus it is suitable to study the effects of fault network geometry (across-and along-strike interaction) on the seismic cycle and earthquake statistics (e.g. recurrence time, coefficient of variation) of a geologically realistic fault network. We use the boundary-element code QDYN which incorporates rate-and-state friction and elastic interactions to examine relevant inputs for seismic hazard assessment, including inter-event time within and between faults, magnitude-frequency distribution, and nucleation location. We are able to simulate spontaneous ruptures following power-law relationships of frequency-magnitude distribution. Differences in the recurrence time (periodic vs. aperiodic cycles) and rupture extent (characteristic vs. non-characteristic seismicity) in the fault planes seem to correlate with the number of faults that exist across strike. Our simulations demonstrate how quasi-dynamic earthquake simulators can provide insights into how fault network geometry impacts earthquake occurrence and seismic hazard assessment.
Transverse energy injection scales at the base of the solar corona
Authors: Morton Richard , Sharma Rahul
Published: March 2024

Alfvén wave turbulence models are the foundation of many investigations into the winds and EUV/X-ray emission from cool, solar-like stars. The models are used to estimate mass loss rates, magnetic spin down and exoplanet habitability. However, the models currently rely on ad-hoc estimates of critical parameters. One such parameter is the perpendicular correlation length, L⊥ (the energy injection length scale), whose value has significant influence over the turbulent heating and mass loss rates. Using the Coronal Multi-channel Polarimeter, a ground based corona-graph, we provide the first measurements of the correlation length of Alfvénic waves at the base of the corona. Our analysis shows the values are broadly homogeneous through the corona and have a distribution sharply peaked around 7.6 - 9.3 Mm. The measured correlation length is comparable to the expected scales associated with supergranulation. The results also suggest a discrepancy between the coronal values of L⊥, theoretical transport models for the evolution of L⊥ with distance from the Sun, and previous estimates of L⊥ beyond the Alfvén critical zone. We suggest a thesis as to the missing physics.