bluuebunny/crossref_metadata_2025 huggingface dataset:
Global inversion and parametrization for building tomographic velocity models
Authors: Kakhkhorov Umedzhon , Arntsen Børge , Weibull Wiktor Waldemar , Raknes Espen Birger
Published: February 2023

Traveltime tomography is applied to investigate seismic structures of the Earth's subsurface. An accurate tomographic velocity model is important for a high-resolution waveform velocity building and its availability is one of the main components to mitigate the nonlinear inverse problem. We present a new methodology of obtaining velocity models for traveltime tomography studies. We found a way to get a highly accurate first-arrival traveltime tomography in combination with global optimization. The role of global optimization is twofold: to find initial solutions that are close to ‘truth’, and to guide tomographic inversion towards a geologically consistent model that explains the data. The main advantage of our workflow is a data-driven approach avoiding the use of a conventional layer-based parameterization and incorporation of manual interpretations into the velocity model. To date, a few geophysical studies have been focused on developing data-driven and a labour non-intensive regional tomographic velocity model building workflow. In our study, we present the tomographic velocity model building workflow as a combination of first-arrival traveltime tomography and global optimization. Global optimization allows to search for velocity parameters and depth to interfaces in the larger search area with a higher chance of convergence. After defining the geometry of main layers and general velocity trends, traveltime tomography with a bi-cubic B-spline model parameterization can be fitted to further update the velocity model. Our approach allows obtaining a highly accurate velocity model which can be used for seismic depth migration and as a starting model for a FWI seismic imaging. The workflow is developed and applied to synthetic and field regional seismic datasets. The developed methodology is applied for a shallow seismic engineering data and regional Ocean Bottom Seismic data. We identify four key components that lead to building an accurate tomographic velocity model: (i) understanding prominent horizons and possible velocity distribution of a layer within the study area. (ii) Performing ray penetration test to define offset ranges which carry the velocity information for the defined layers. (iii) Determining inversion schema to a perform global search for the velocity trends and major boundaries, and a local search to update lateral velocity variation. (iv) Iteratively update a set of defined layers (i.e., sediment, igneous crust and basement) in a top-down manner. 
Simulation of future extreme rainfall events over Belgium with a focus on the Vesdre valley using the regional climate model MAR.
Authors: Brajkovic Josip , Van De Vyver Hans , Doutreloup Sébastien , Ghilain Nicolas , Fettweis Xavier
Published: February 2023

The rainfall in July 2021 that hit West Germany, Netherlands and Belgium was of unprecedented intensity. To assess the probability of such events ocuring in a near and far future (until 2100), the regional climate model MAR has been used to make simulations at a resolution of 7,5 km. To this end, the regional climate model MAR is linked to a set of Earth System models (ESMs) with 4 IPCC SSP scenarios over a domain that includes Belgium and Luxemburg. The analysis focused on the valley of the Vesdre which in Belgium was the most impacted by flooding in terms of damage to human infrastructures.For some specific climatic conditions, MAR simulates events of similar intensity to those of the 2021-floods over the next 5 decades. To assess the statistic significance of the results, a Peaks Over Threshold analysis (POT) has been applied to MAR outputs for precipitation events of 1,2,3,4 and 5-days. Quantiles associated with high return periods have been calculated for the historical period of simulation (1980-2010) and for the 2011-2040, 2041-2070 an 2071-2100 periods. This shows that the frequency of such events in the periods 2011-2040 and 2041-2070 is likely to increase if climatic conditions are wet enough. For global warming levels above 3 to 4 °C, conditions appear too dry for such events to occur.
Assessing the impact of large-scale afforestation on the atmospheric water cycle of the Loess Plateau in China
Authors: Tian Lei , Chen Shuoyu , Zhang Baoqing , Pan Baotian
Published: February 2023

Afforestation has been regarded as an appropriate way to mitigate climate change and enhance ecosystem services. How afforestation affects the availability of water resources is a hot topic in the science community. Most current studies investigate the impact of afforestation on water resources through offline modeling or observation on a small spatial scale. However, the atmospheric water cycle (AWC) is also an important aspect that can alter the availability of water resources, especially on a large spatial scale. With an investment of about US$54.57 billion, the Chinese government implemented the world’s largest afforestation project, the Grain for Green Program (GFGP), to curb the severe soil erosion over the Loess Plateau (LP) since 1999. Here we focused on this ideal platform, the LP, to explore the impact of large-scale afforestation on the processes related to the atmospheric water cycle. We adopted two different approaches to discern the hydroclimatic effect of the GFGP. This first approach used the reanalysis dataset to compare the hydroclimatic states before (1982–1998) and after (1999–2018) the GFGP. Since the reanalysis dataset cannot separate the impact of climate change and afforestation, this study also applied a regional climate model (the Weather Research & Forecasting Model, WRF) to isolate the net hydroclimatic effect of the GFGP by controlled experiments. In particular, the WRF model was driven by two land surface conditions with/without the implementation of the GFGP. We found both approaches reached similar conclusions. Results show the vegetation coverage fraction over the LP increased by 3.15% decade−1 induced by the GFGP. The climatological precipitation and evapotranspiration (ET) increased by 54.62 and 22.56 mm, respectively, after starting the GFGP in 1999. The large-scale afforestation intensifies the atmospheric water cycle over the LP. In addition, based on the dynamic precipitation recycling model, we also found the precipitation recycling ratio approximately increased by 1%. The GFGP alters the regional circulation by influencing diabatic heating, and moisture convergence, resulting in more moisture being advected from the south boundary, thus more atmospheric moisture was retained in the LP. Additionally, the internal branch of the AWC contributes to about 15% of the increased precipitation, while the contribution of the external branch is about 85%. Moreover, the GFGP remotely affects the water vapor budget in the downwind areas. Our work enriched the current understanding of how afforestation affects the water cycle from a precipitation recycling perspective and can help policy-makers to make science-informed afforestation strategies.
Evaluating Western North Pacific Tropical Cyclone Forecast in the Subseasonal to Seasonal Prediction Project Database
Authors: Wang Xiaochun , Waliser Duane , Vitart Frederic , Jiang Xianan , Asharaf Shakeel
Published: February 2023

The Daily Tropical Cyclone Probability (DTCP), defined as the probability of tropical cyclone occurrence within 500 km of a location in one day, is proposed and used in evaluating subseasonal to seasonal (S2S) predictions from the S2S Prediction Project Database, from May 1 to Oct. 31, 1999, to 2010. The ensemble reforecasts are collected from eleven operational centers, the BoM, CMA, ECCC, ECMWF, HMCR, ISAC, JMA, KMA, METFR, NCEP, and UKMO.  In both observation and these eleven forecast models, the DTCP is modulated by the Boreal Summer Intraseasonal Oscillation (BSISO), depicted by the two indices, BSISO1 and BSISO2. During BSISO1 phases 1, 5, 6, 7, and 8, the DTCP in the northwestern Pacific region is ~3.5 times higher. Similarly, during phases 1, 2, 3, 4, and 8 of BSISO2, the DTCP is  ~2.5 times higher.  Among the eleven models, the ECMWF model best reproduces the climatological DTCP and its modulation by the BSISO in the western North  Pacific region, followed by NCEP, KMA, JMA  models. Using the DTCP metric, the highest debiased Brier Skill Score of the eleven models is from ECMWF, which has a slightly less skillful prediction than the reference climatological forecast with lead time 11 to 30 days. The skill of the eleven models is higher during the non-active phases of tropical cyclone activity than their skill during the active phases.  The updated results based on the real-time tropical cyclone forecasts of the S2S Prediction Project Database  from these eleven systems will also be discussed.
The influence of magnetic topology on ionospheric structure at Mars: Observations of localized “magnetic depletions”
Authors: Fowler Christopher , Ortiz Zack , Xu Shaosui , Mitchell David , Hanley Kathleen , Espley Jared , Andersson Laila , McFadden James , Luhmann Janet , Curry Shannon
Published: February 2023

The interaction between Mars' crustal magnetic fields and the solar wind produces a variety of magnetic topologies whose characteristics depend upon the plasma regions that the magnetic field is embedded in. We utilize in-situ Mars Atmosphere And Volatile EvolutioN (MAVEN) measurements to identify localized ionospheric structures, observed as the spacecraft flies through this patchwork of different magnetic topologies. Events are characterized by sharp ‘drop outs’ in magnetic field strength that we term ‘magnetic depletions’. The plasma pressure dominates within magnetic depletions, while the magnetic pressure typically dominates outside of them. Abrupt changes in magnetic topology are coincident with the depletion boundaries. A preliminary statistical study spanning 3 months shows that events occur on ∼4% of MAVEN orbits, between altitudes of 170–360 km. Ionospheric electrons are collisionless and thus magnetized at these altitudes, and combined with the fact that magnetic diffusion timescales range from minutes to an hour, these characteristics suggest that such structures can be observed sporadically by MAVEN on its ∼4.5 hour orbit before being smeared out by magnetic diffusion. At lower altitudes high collision rates lead to diffusion timescales of seconds, while at higher altitudes electromagnetic waves, instabilities and other transport processes driven by the Mars-solar wind interaction can distort the magnetic field, making magnetic depletion events difficult to identify. Magnetic depletions highlight the ability of magnetic topology to drive localized ionospheric structure at Mars, a result that stems from the unique interaction between the solar wind, Mars' crustal magnetic fields, and it's ionosphere.
Effectiveness of mangroves as nature-based coastal defences in the Pearl River Delta
Authors: De Dominicis Michela , Wolf Judith , van Hespen Rosanna , Zheng Peng , Hu Zhan
Published: February 2023

Coastal vegetation can reduce extreme water levels during storm events, but the controlling factors and processes in complex estuary or delta systems are still unclear. This limits an effective implementation of nature-based coastal defences in delta mega-cities in low-lying coastal areas.To explore the effects of vegetation on storm surge dynamics and currents, we used a Finite Volume Community Ocean Model implementation for the South China Sea and the Pearl River Delta. We numerically modelled how mangroves can offer coastal protection to the large coastal cities located in the delta, such as Guangzhou and Shenzhen, during strong typhoons, like Hato (2017).Additionally, we analyzed how the effectiveness of mangroves changes under different sea level rise scenarios.Water level attenuation by mangroves is effective during extreme water level conditions and differences in mangrove forests' properties drive their coastal protection function. The local (within-wetland) attenuation of extreme water levels is more effective with wide vegetation patches and higher vegetation drag. Narrower vegetation patches can still provide non-local (upstream) water level attenuation if located in the upper estuary channels, but their design needs to avoid amplification of water levels in other delta areas.
A further explore the source features of the 2016 Mw 5.9 Menyuan earthquake by empirical Green's functions and dynamic simulations
Authors: Xu Duyuan , Gong Wenzheng , Zhang Zhenguo , Yu Houyun , Chen Xiaofei
Published: February 2023

A quantitative understanding of the factors that control earthquake rupture propagation is critical because it is helpful to estimate the eventual magnitude of an earthquake, which has significant implications for seismic hazard assessment. Previous studies suggest that the complex fault geometry and the heterogeneous material properties of the fault zone can slow and/or stop the rupture propagation. The 2016 Mw 5.9 Menyuan earthquake occurred near the Haiyuan fault system on the northeastern Tibetan plateau. Although some of the kinematic rupture properties of this earthquake have been known, the rupture process and some in-depth source properties remain to be understood. In this study, we first use the empirical Green's functions approach to reveal that the apparent source time functions (ASTFs) of this event display an approximately equal bell shape and have a total duration of about 3 s, which suggests that the rupture process of this earthquake is simple and exhibits no rupture directivity. Moreover, the spectra of ASTFs are very smooth and have no spectral holes. Then, we conduct two end-member spontaneous rupture models, namely the runaway rupture and the self-arresting rupture, to further explain the observed features of the ASTFs. We use the curved grid finite difference method (CG-FDM) to simulate the spontaneous rupture process with a linear slip-weakening friction law. Our results show that the synthetic data from the dynamic source fits well with the InSAR observations and strong ground motions, which indicates that the dynamic source captures the main features of this event. Significantly, the observed smooth spectra of ASTFs can be well explained by the self-arresting rupture process, which implies that this earthquake might be a self-arresting event. In other words, this earthquake may spontaneously stop before reaching the barriers. This finding suggests that some earthquake rupture processes may be deterministic by the initial stress state in which they nucleated. This work increases our understanding of what controls earthquake rupture propagation.  
Evaluating the Global Internal Wave Model IDEMIX with observations of both stratification and horizontal velocity
Authors: Garcia Santacruz Dinora , Mertens Christian , Pollmann Friederike , Olbers Dirk
Published: February 2023

The model ‘Internal Wave Dissipation, Energy and Mixing’ (IDEMIX) provides an energetically consistent representation for the diapycnal diffusivity induced by breaking of internal gravity waves in ocean and atmosphere circulation models. IDEMIX predicts the internal wave energy, dissipation rates, and diapycnal diffusivities. Such small-scale processes cannot be resolved but have to be parameterized due to their relevance for the large-scale circulation. The basic version of the model has been shown to be generally successful in ocean and atmosphere applications. However, in regions of strong forcing deviations from observational estimates were found. To evaluate the local performance of the model we analyzed the agreement with observational estimates of full-depth profiles of both stratification and horizontal velocity collected by several cruises around 47°N and 16°N in the Atlantic. The hydrographic profiles come from two dynamically different regions: the subpolar North Atlantic with energetic wind-induced near-inertial waves and the western subtropical Atlantic where the strong Deep Western Boundary Current interacts with the continental slope producing lee waves. Internal wave energy, dissipation rates and diapycnal diffusivities estimates are obtained using the finestructure method. These estimates can be calculated using shear and strain or strain only in lack of velocity data. In this study, both formulations have been calculated and contrasted between each other to evaluate the importance of shear information for a realistic energy budget. The results when comparing IDEMIX with observations show that the higher differences are close to the surface and over the rough topography where internal gravity waves are more predominant. The analysis of the observational data will increase our understanding of the spatiotemporal variability of the ocean’s internal gravity wavefield and will complement the model-based investigation of the responsible processes.
About the possibility of monitoring groundwater fluxes variations through active-DTS measurements
Authors: Bour Olivier , Simon Nataline , Lavenant Nicolas , Porel Gilles , Nauleau Benoît , Klepikova Maria
Published: February 2023

The monitoring of temporal variabilities of groundwater flows is a critical point in many hydrogeological contexts, especially for the characterization of coastal aquifers, sub-surface heterogeneities or else groundwater/stream interactions. Considering the lack of available methods, we investigate the possibility of monitoring and quantifying groundwater fluxes variations over time through active-Distributed Temperature Sensing (DTS) measurements. Active-DTS, consisting in heating a fiber optic cable, performs very well for investigating the spatial distribution of groundwater fluxes but the method has never been tested to continuously monitor groundwater fluxes changes. In this context, both numerical simulations and sandbox experiments were performed in order to assess the sensitivity of temperature elevation to variable flow conditions. Results first demonstrate that when a flow change is followed by a long-enough steady-state flow stage the temperature elevation stabilizes independently of previous fluxes conditions. Thus, the stabilization temperature can easily be interpreted to estimate groundwater fluxes using the analytical model commonly used under steady flow conditions to interpret active-DTS measurements. Under certain flow conditions, depending on the nature of flow variations, the approach also allows the continuous monitoring of fluxes variations over time. If instantaneous flow changes occur, the superposition principle can even be used to reproduce the temperature signal over time. In summary, we demonstrated through these preliminary results the possibility of for monitoring and/or quantifying the temporal dynamic of groundwater fluxes at different temporal scales including diurnal and periodic fluxes variations, which open very interesting perspectives for the quantification of subsurface processes.
Upper tropospheric convective outflow in ICON convection-permitting and parameterised set-up
Authors: Groot Edward , Kuntze Patrick , Miltenberger Annette , Tost Holger
Published: February 2023

The representation of upper tropospheric deep convective divergent outflow (UTDCDO) is compared between ICON-simulations with convection-permitting and convection parameterised set-ups (1 and 13 km resolution) for a convective event over Germany and the Alps on June 10th-11th 2019. Three hypotheses on those UTDCDO have been formulated using idealised Large Eddy Simulations and are now tested on ICON in a convection-permitting set-up: 1. Dimensionality affects the magnitude of UTDCDO in ICON; 2. Convective aggregation and organisation affects the magnitude of those convective outflows in ICON and 3. Convective momentum transport does not affect the magnitude of UTDCDO. A moving box is used to integrate mesoscale divergence, precipitation rate and convective momentum transport. Additionally, ellipse fitting is used to make estimates of convective organisation (dimensionality, area of convective precipitation, etc.).Variability in UTDCDO at a given net latent heating rate is reduced in ICON with parameterised deep convection, compared to the convection-permitting set-up. Hints, but no conclusive results are found on the effect of dimensionality on the magnitude of UT divergent deep convective outflows. An impact of convective organisation and aggregation on UTDCDO is significant in the dataset: as a consequence of outflow collisions, UTDCDO increases sub-linearly with net latent heating. We also found a statistical relation between normalised UTDCDO and normalised convective momentum transport.  
Validating radiation pressure force models for GRACE with SLR
Authors: Vielberg Kristin , Löcher Anno , Kusche Jürgen
Published: February 2023

Precise non-gravitational force models are crucial for satellite gravimetry, thermospheric neutral density estimation, and precise orbit estimation (POD). Besides the dominating aerodynamic acceleration acting on low Earth orbit satellites, radiation pressure accelerations impact their motion. The acceleration due to the Earth radiation pressure (ERP) decreases with increasing satellite altitude, whereas the effects of the Solar radiation pressure (SRP) and thermal reradiation pressure (TRP) vary mainly with the satellite’s orientation towards the Sun.In previous investigations, we extended the existing radiation pressure force models with a focus on a GRACE-like satellite. However, validating the non-gravitational force modelling remained difficult. For GRACE and GRACE-FO, a comparison to measured accelerometer data is possible. However, it is obviously difficult to separate residual effects of the necessary accelerometer calibration procedure from errors in the radiation pressure models.To overcome these disadvantages, here we perform a validation of modelled non-gravitational accelerations using independent satellite laser ranging (SLR) measurements, which do not require such calibration. This approach is twofold. In a first step, a POD is performed, where kinematic GNSS-orbits and modelled non-gravitational accelerations serve as input together with gravitational state-of-the-art background models. Second, the residuals between the SLR measurements and the derived orbit are computed. Since we assume the SLR observations as the truth, small residuals indicate that the modelled non-gravitational accelerations represent reality well. A comparison against GNSS orbit solutions is not performed here, since kinematic orbits are already part of the first step and the comparison would not be independent.We choose the year 2008 for our experiments, where the radiation pressure signal is at the same order of magnitude as the aerodynamic signal. Our two-fold approach is performed several times, where we vary the parametrization of the radiation pressure force model, e.g., the consideration of the Earth’s radiation data sets or the satellite’s thermal reradiation. The aerodynamic model is kept fixed during these experiments and a scale factor for this force is co-estimated to account for its mismodelling. Our preliminary results indicate that the smallest residuals occur when considering non-instantaneous TRP acceleration with modified material (diffusion) parameters in addition to our extended ERP and SRP force models. In this case, the annual RMS per pass of the residuals is 2.72cm, which is 2.4cm below the results obtained with standard models and still nearly 4mm less than without modifying the TRP parameters.
Cloud parameters from reanalysis datasets – a comparison with satellite data
Authors: Lauer Axel , Bock Lisa , Hassler Birgit
Published: February 2023

Clouds are a key component of the hydrological cycle and play an important role in weather and climate. Feedbacks between clouds and climate have important implications for climate sensitivity and thus on amplitude and pace of future climate change. In this study, as part of the SPARC Reanalysis Intercomparison Project (S-RIP) phase 2, we compare the cloud parameters from different reanalysis datasets, including the most widely used reanalyses ERA5, MERRA2 and JRA-55, with satellite observations. The study focuses on tropospheric clouds on monthly to seasonal and multi-year time scales. Means and variability of cloud parameters from the reanalyses such as cloud fraction, cloud liquid and ice water content as well as cloud radiative effects are compared to satellite observations for specific cloud regimes and regions. In addition to evaluating the performance of the different reanalysis products, we investigate whether the multi-reanalysis mean is in closer agreement with the observations than the individual reanalyses.The analyses are performed with the Earth System Model Evaluation Tool (ESMValTool), a community developed open-source software tool. The tool provides common operations such as interpolating data on the same grid, calculating multi-reanalysis means, common data masking, area extraction, and basic statistics such as seasonal means, annual means, area means, etc. which facilitates a fair comparison with observations. Uncertainties are estimated using multi-product observational reference datasets.
A detailed analysis of ion-acoustic waves observed in the solar wind by the Solar Orbiter
Authors: Pisa David , Soucek Jan , Santolik Ondrej , Formanek Tomas , Maksimovic Milan , Chust Thomas , Khotyaintsev Yuri , Kretzschmar Matthieu , Owen Christopher , Louarn Philippe , Fedorov Andrei
Published: February 2023

Ion-acoustic waves are often observed in the solar wind along the Solar Orbiter’s orbit. These electrostatic waves are generated via ion-ion or current-driven instabilities below the local proton plasma frequency. Due to the Doppler shift, they are typically observed in the frequency range between the local electron and proton plasma frequency in the spacecraft frame. Ion-acoustic waves often accompany large-scale solar wind structures and play a role in the energy dissipation in the propagating solar wind. Time Domain Sampler (TDS) receiver, a part of the Radio and Plasma Waves (RPW) instrument, is sampling wave emissions at frequencies below 200 kHz almost continuously from the beginning of the mission. Almost three years of observations allow us to perform a detailed study of ion-acoustic waves in the solar wind under variable plasma conditions. The emission tends to be observed when proton density and temperature are highly perturbed. A detailed analysis of the proton velocity distribution and wave generation using solar wind data from a Proton and Alpha particle Sensor (PAS) of the Solar Wind Analyzer (SWA) is shown.
Earthquake swarm September/October 2022 on Disko Island, West Greenland
Authors: Dahl-Jensen Trine , Voss Peter H. , Larsen Tine B.
Published: February 2023

During 25 days in September and August 2022, the island of Disko in central west Greenland experienced a swarm of around 200 small earthquakes, ranging from ML 1.0 to ML 3.1. The majority of the earthquakes were concentrated on a small peninsula measuring 15 x 25 km. We have not received any felt reports, with  the closest inhabited area is approximately 20 km away. The island of Disko is part of the Palaeogene North Atlantic province. Swarms has been observed on and around Disko Island earlier, but not in the same place as the September/October 2022 swarm. In 2010, 27 earthquakes were detected in an area  around 20 km to the east [1], and in 2016 a swarm of over 250 earthquakes occurred following three mb 4.5+ earthquakes. These earthquakes occurred offshore and south of Disko Island, 60 km to the SSE [2]. The coverage with seismic stations is Greenland is sparse, with distances between stations in hundreds of km, but since 2019 three additional stations have been in operation in central west Greenland due to monitoring for landslide events, enabling better locations. The closest station to the swarm is GDH, at 60 km distance. The largest earthquakes in the swarm could be observed at a distance of more than 1600 km.Larsen, T.B., et al., Earthquake swarms in Greenland. Geological Survey of Denmark and Greenland (GEUS) Bulletin, 2014. 31: p. 75-78.
Dahl-Jensen, T., P.H. Voss, and T.B. Larsen, [S01-4-01] Recent earthquakes at Disko Island, Greenland, with focal mechanisms in IAG-IASPEI Joint Scientific Assembly. 2017: Kobe, Japan.
Water Uptake Rates Estimation from Sentinel-1 C-band Synthetic Aperture Radar over Olive Orchards
Authors: El Hajj Marcel M. , Johansen Kasper , Almashharawi Samir K. , McCabe Matthew F.
Published: February 2023

Monitoring the water-uptake rate (WUR) in olive orchards is a key parameter for improving irrigation efficiency and represents an indicator of tree health and yield. Commercial olive orchards extend over large areas and therefore, the use of in-situ sensors to monitor tree WUR, such as the installation of sap flow meters, which are costly and time-consuming to install, are not feasible. The aim of this study is to investigate the potential of C-band Synthetic Aperture Radar (SAR) data acquired by Sentinel-1 with 6-days revisit time to estimate the WUR in very high-density olive orchards in the hot and arid desert climate of Saudi Arabia. A random forest regression (RFR) model was used to calibrate the SAR-derived metrics against WUR measurements recorded by sap flow meters in six plots in 2019, 2020, and 2021. Later, SAR-derived metrics and the coincident WUR measurements were used for RFR optimization and validation. A SAR-derived metric to predict the WUR in a plot at a given Sentinel-1 acquisition date was the difference between the SAR backscattering at that image date and the average SAR backscattering in the second-half of January, when WUR was negligible (around 0.1 L.h-1). The optimized RFR approach provided an accurate estimate of WUR (R2 = 0.86, RMSE = 0.13 [L.h-1]). The optimized RFR was used to operationally map the WUR at the plot level between 2019 and 2021 with a revisit time of 6 days. Results showed that the average WUR over the mapped area co-varied with the average daily air temperature (R2 = 0.82) and inversely co-varied with the average daily air humidity (R2 = 0.58), both recorded by a weather station installed at the study site. These observations support the operational mapping results as they are consistent with the principle of soil-plant-atmosphere interactions, where the WUR generally increases with air temperature and decreases with air humidity. Future work should focus on the assimilation of SAR-derived WUR into water-use models to evaluate the added value of SAR-derived WUR for water resource management in olive orchards.
Extreme precipitation in South Sulawesi triggered by equatorial waves and its representation in MetUM forecasts
Authors: Senior Natasha , Matthews Adrian , Webber Ben , Latos Beata , Baranowski Dariusz
Published: February 2023

The Indonesian island of Sulawesi lies at the heart of the Maritime Continent, a region prone to extreme rainfall. On seasonal timescales, rainfall frequency and intensity increases during the monsoon season (Nov-March). On subseasonal scales, rainfall is modulated by the Madden-Julian Oscillation (MJO) which increases moisture and moisture convergence in its active phase. Higher frequency modes include convectively coupled equatorial waves which influence rainfall variability on daily timescales. On 22nd January 2019, these large-scale meteorological drivers coincided resulting in the South Sulawesi region experiencing its largest flood on record. Specifically, the extreme rainfall event was linked to a convectively coupled Kelvin wave (CCKW) and a convectively coupled equatorial Rossby wave (CCERW) embedded within an active MJO envelope, as well as a cross equatorial cold surge (Latos et al, 2021). Interactions between these modes resulted in increased moisture transport and convergence that lead to the development of a mesoscale convective system (MCS) over Java and the Java Sea on 21st January 2019. This MCS traversed towards Sulawesi bringing extreme rainfall to the region in the evening and overnight on the 22nd reaching its peak mid-afternoon. Cases like this present a unique challenge for forecasters, to not only to accurately represent the individual equatorial modes but their interactions. In the present work we study the MCS in reanalysis and satellite data and discuss how the various equatorial modes contributed to its development. Then we examine its representation in different convection permitting Met Office Unified Model (MetUM) configurations. We find that the MetUM performed well in capturing the trajectories of the equatorial modes, however the representation of the MCS itself varies between ensemble members and model configurations. We further examine how well the RAL1T+ configuration represents the equatorial modes through comparing filtered fields of daily model data at fixed lead times to those in observations.
Reduction of ocean tide aliasing errors in GRACE, GRACE-FO, and future mission gravity field recovery
Authors: Wilms Josefine , Panafidina Natalia , Hauk Markus , Dahle Christoph , Sulzbach Roman , Flechtner Frank
Published: February 2023

The GRACE and GRACE-FO missions have been fundamental in establishing a near-continuous time series of global mass transport since 2002. However, monthly gravity field recovery using these mission data includes errors limiting the spatial and temporal resolution of the estimated gravity field solutions. Besides the noise of the accelerometer instruments, the primary error contributions arise from temporal aliasing errors due to undersampling of signals to be recovered (e.g., hydrology), uncertainties in the de-aliasing models (e.g., non-tidal atmosphere and ocean), and imperfect ocean tide models. Especially the latter will also remain one of the most limiting factors in determining high-resolution temporal gravity fields from Next-Generation Gravity Missions (NGGM).In this context, recent further developments have been made within the research unit, NEROGRAV (New Refined Observations of Climate Change from Spaceborne Gravity Missions), funded by the German Research Foundation (DFG). One of the NEROGRAV projects deals with stochastic modeling of ocean tide background models utilizing covariance information for eight major tidal constituents. The repeatable pattern of the tidal signal enables the extraction of uncertainty information by an ensemble of different ocean tide models. This information can be introduced into the gravity field recovery process as a covariance matrix while expanding the parameter space by additional tidal parameters to be estimated.This presentation provides an overview of the recovered monthly gravity fields from GRACE/GRACE-FO when applying covariance information of ocean tide errors. In addition, realistic simulations have been performed to assess the pure effect of the covariance information on ocean tide errors and the potential of co-estimating ocean tides over a longer period while considering tidal covariance information is addressed. It is shown that the application of ocean tide covariance information contributes to the reduction of temporal aliasing caused by the mismodeling of ocean tide background models.
New constraints on Middle-Late Pleistocene large-magnitude eruptions from Campi Flegrei
Authors: Fernandez Giada , Giaccio Biagio , Costa Antonio , Monaco Lorenzo , Albert Paul , Nomade Sebastien , Pereira Alison , Leicher Niklas , Lucchi Federico , Petrosino Paola , Milia Alfonsa , Insinga Donatella , Wulf Sabine , Kearney Rebecca , Veres Daniel , Jordanova Diana , Sottili Gianluca
Published: February 2023

Assessing the history, dynamics and magnitude of pre-historic explosive volcanic eruptions relies heavily on the completeness of the stratigraphic records, the spatial distribution, and the sedimentological features of the pyroclastic deposits. Near-vent volcanic successions provide fundamental but often patchy information, both in terms of record completeness (e.g., scarce accessibility to the older deposits) and of the spatial variability of the sedimentological features. Hence, medial to distal sections increasingly represent essential integrative records.Campi Flegrei (CF) is among the most productive volcanoes of the Mediterranean area, with a volcanic history comprised of well-known caldera-forming eruptions (e.g., Campanian Ignimbrite, CI, ~40 ka; Neapolitan Yellow Tuff, NYT, ~14 ka). Furthermore, recent studies correlated a well-known widespread distal ash layer, the so-called Y-3, with a poorly exposed proximal CF pyroclastic unit (Masseria del Monte Tuff, 29ka), allowing a re-assessment of the magnitude of this eruption, now recognized as a third large-magnitude (VEI 6) eruption at CF. The discovery of this large eruption reduces drastically the recurrence intervals of large-magnitude events at CF and has major implications for volcanic hazard assessment.While the most powerful Late Pleistocene (e.g., post-NYT and partially post-CI) eruptions at CF have been the subject of extensive investigations, less is known about its earliest activity. Motivated by this knowledge gap, we have reviewed the research on Middle-Late Pleistocene eruptions from the CF (~160-90 ka) in light of new compositional (EMPA + LA-ICP-MS), grain-size distribution (dry/wet sieving and laser) and morphoscopy (SEM) data of tephra layers from proximal and distal settings, including inland and offshore records. Our study provides a long-term overview and cornerstone that will help provide future eruptive scenarios, essential for the quantification of recurrence times of explosive activity and in volcanic hazard assessment in the Neapolitan area. This overview sets the basis for modelling dispersion as well as eruptive dynamics parameters of pre-CI large-magnitude eruptions, needed to better understand the behavior of the CF caldera with a long-term perspective.
COST-G models of time-variable gravity for precise orbit determination
Authors: Meyer Ulrich , Peter Heike , Geisser Linda , Calero Emilio , Dach Rolf , Jäggi Adrian
Published: February 2023

The Combination Service for Time-variable Gravity fields (COST-G) provides models of the time-variable Earth gravity field that may be used for precise orbit determination (POD). While the monthly snapshot solutions based on GRACE or GRACE-FO GPS and microwave ranging interferometer data are the best available information on the time-variable gravity field, their latency of about 2-3 months prevents their use in operational POD. COST-G also provides a signal model fitted to the monthly GRACE-FO gravity fields that is updated quarterly and allows for the prediction of time-variable gravity, e.g. for use in applications that rely on short latency like operational POD.We present POD results for LEO and MEO satellites based on the COST-G fitted signal model (FSM), where we put special attention on the impact of the C20 gravity field coefficient, which is poorly defined from the GRACE/GRACE-FO observations, but may be replaced by SLR-only or SLR+GRACE/GRACE-FO combined solutions. We moreover present an extension of the COST-G FSM, also covering the GRACE-period and therefore suited for reprocessing campaigns that rely on a consistent model of time-variable gravity.
Diffuse CO2 emission from NERZ and NWRZ Tenerife volcanic systems, Canary Islands
Authors: Pitti Lía , Melián Gladys V. , Rodríguez Fátima , Padrón Eleazar , Pérez Nemesio M. , Asensio-Ramos María , Martín Alba , Di Nardo Daniel , Santana León José Manuel , Ortega-Ramos Víctor , García-Hernández Rubén , Martínez van Dorth David , Hernández Pedro A.
Published: February 2023

Tenerife (2,034 km2), the largest island of the Canarian archipelago, is characterized by three volcanic rifts NW-SE, NE-SW and N-S oriented, with a central volcanic structure, Las Cañadas caldera, hosting Teide-Pico Viejo volcanic complex. The North-West volcanic Rift Zone (NWRZ, 72 km2) is one of the youngest and most active volcanic systems of the island, where three historical eruptions (Boca Cangrejo in the 16th Century, Arenas Negras in 1706 and Chinyero in 1909) have occurred. The North-East volcanic Rift Zone (NERZ, 210 km2) has showed one historical eruptive activity during 1704 and 1705 across 13 km of fissuraleruption (Siete Fuentes-Arafo-Fasnia eruption). As part of the volcano monitoring program of NWRZ and NERZ, diffuse CO2 degassing surveys have been carried out yearly since 2000 at the NWRZ and since 2001 at the NERZ. In-situ measurements of CO2 efflux from the surface environment were performed according to the accumulation chamber method using a portable non-dispersive infrared (NDIR) sensor. Soil CO2 efflux contour maps were constructed to identify spatial-temporal anomalies and to quantify the total CO2 emission using the sequential Gaussian simulation (sGs) interpolation method. Previous studies in the NWRZ has shown a temporal correlation between long-term variations in the diffuse CO2 output with the occurrence of a seismic unrest in 2004 and the 2016 seismic swarm (Hernández et al., 2017). The last diffuse CO2 emission survey performed in the survey in the NWRZ in 2022 showed values between non-detectable ones and 32.1 g·m-2·d-1, with an average value of 5.6 g·m-2·d-1 for NWRZ. In the case of the NERZ, the last diffuse CO2 emission survey performed in 2022 showed values ranging between non-detectable values and 59.1 g·m2·d-1, with an average value of 6.7 g·m-2·d-1. Diffuse CO2 emission rate were estimated in 360 ± 15 t·d-1 for NWRZ and 1,444 ± 42 t·d-1 NERZ were obtained in the 2022 surveys. The normalized CO2 emission value by area was estimated in 5 t·d-1·km-2 for NWRZ and in 6.9 t·d-1·km-2 for NERZ. Temporal evolution of diffuse CO2 emission at both NWRZ and NERZ of Tenerife shows a clear relationship with the volcano seismic activity in and around Tenerife Island. These geochemical observations are clear evidence of changes of processes operating deep in the hydrothermal-magmatic system of Tenerife.Hernández et al. (2017). Bull Volcanol, 79:30, DOI 10.1007/s00445-017-1109-9.
In-situ tidal marsh erodibility under high flow velocities
Authors: van den Berg Mario , Stoorvogel Marte , Schoutens Ken , van den Hoven Kim , Rikkert Stephan J.H. , Herman Peter M.J. , Aarninkhof Stefan G.J.
Published: February 2023

Coastal defences such as dikes are increasingly pressured by climate change. Increasing storm surge, extreme rainfall and periods of draught requires evermore strengthening of dikes to maintain flood risk standards. Conventional dike strengthening (i.e., heightening and/or widening) will be either structurally or financially unfeasible. Therefor, engineers are exploring other, more sustainable, methods to ensure future flood safety. A promising method is incorporating tidal marshes in the coastal defence system. Tidal marshes reduce dike loads by wave attenuation, increase bio diversity and ecology and under the right circumstances are able to grow with sea level rise. Moreover, in case of dike failure, resulting in a dike breach and inundation of the hinterland, tidal marshes have been shown to reduce breach erosion rates. This reduction positively affects flood risk. However, in order to quantitatively estimate the effect, dike breach models need to also model tidal marsh erosion. In this study we tested a mature tidal marsh, in-situ, in winter conditions under high flow velocities (up to 2.5 m/s) to measure the erosion and estimate erodibility. We measured little erosion, order millimeters after a cumulative 2-2.5 hours. Small-scale experiments, such as the Jet Erosion Test, showed high resistance to erosion (85-140 Pa) and large varying erodibility (6.5-45 cm3/N·s). By estimating the shear stresses acting on the soil during the experiment we compare the data with the small-scale results. The comparison gives insight in whether the small-scale experiment results can be accurately translated to full-scale erosion. Also, the experiment showed which (erosion) mechanisms are important for tidal marshes during a dike breach.
Holocene deformation on a transform fault: Insights from paleoseismology on the Húsavík-Flatey Fault in North Iceland
Authors: Matrau Rémi , Klinger Yann , Harrington Jonathan , Thórdarson Thorvaldur , Höskuldsson Ármann , Gudmundsdöttir Esther , Parisi Laura , Fittipaldi Margherita , Avsar Ulas , Jónsson Sigurjón
Published: February 2023

Studies of Oceanic Transform Faults (OTFs) usually rely on geophysical data because of the OTF inaccessibility on the seafloor. The Húsavík-Flatey Fault (HFF) in northern Iceland is an OTF connecting the onshore rift in Iceland to an offshore rift segment of the Mid-Atlantic Ridge, accommodating 30% to 50% of the relative plate motion at this latitude between North America and Eurasia. The HFF is unique because its easternmost 25 km-long segment is exposed on land, allowing to study the long-term deformation of the fault. Two historical earthquakes of estimated magnitudes M6.5 - M7 have been reported on the eastern HFF in the last 270 years. However, almost no information exists from prior to the 18th century.To study the Holocene deformation of the HFF and to build a catalogue of past earthquakes, we excavated 11 paleoseismology trenches at two locations, six on an alluvial fan and five in a pull-apart basin. We also excavated and tracked buried river channels to estimate long-term slip rates and to assess the coseismic displacement of single events. We used radiocarbon dating of birch wood samples together with major element compositions of volcanic ashes (tephras) to constrain the timing of events on the fault.Trenches at both locations show clear evidence of deformation and surface rupturing events. From offset measurements of glacial morphologies and buried river channels, we calculate a Holocene slip rate of 4 - 6 mm/yr, slightly lower than the estimated present-day geodetic slip rate, suggesting that some of the deformation may be distributed. Based on upward terminations of cracks and faults, we identified eight events in the last ~6000 years, yielding fewer major earthquakes than expected from the 270-year record. We thus suggest that large earthquakes of magnitude ~M7 on the HFF, producing significant surface ruptures, are rare, with a return time of 500 to 600 years. We also propose that the short recurrence times often observed on OTFs may therefore not be representative of the full seismic cycle.
Comparing the loss of polycyclic hydrocarbons (PAHs) in soil and the atmosphere
Authors: Bourhane Zeina , Amato Pierre , Ervens Barbara
Published: February 2023

Gases can partition between soil and the atmosphere, depending on their physicochemical properties. They can be degraded in both compartments by chemical or microbial processes. Polycyclic aromatic hydrocarbons (PAHs) are among such gases that are ubiquitous in the atmosphere and soils. They result mainly from the incomplete combustion or pyrolysis of organic matter; they are of concern due to their toxic, mutagenic and carcinogenic properties. PAHs are semivolatile, highly lipophilic and persistent organic pollutants.
The biodegradation of PAHs and other semivolatile compounds in soil has been extensively studied. Their chemical processing in the atmosphere has also been addressed by means of many model studies. However, even though the existence of bacteria in the atmosphere is well known, the role of atmospheric biodegradation has not been extensively studied.
We present a new model that includes explicit chemical processes in the atmospheric gas and aqueous phases, as well as by biodegradation in fog droplets, coupled to a soil module by volatilization and deposition processes. PAHs in soil are transported between three aerobic layers where they can be degraded by chemical and bacterial processes.
Even though PAH lifetimes in soil and the atmosphere might be similar, our initial model results suggest that degradation in soil represents the major sink for PAHs. While biodegradation in soil is predicted to be the main loss process of PAHs, oxidation processes in the atmospheric gas phase also contribute significantly to overall PAH loss.
Our model represents a new tool to assess the relative and absolute sink strengths of pollutants and other compounds in soil and the atmosphere. We will give an outlook on planned model studies for other compounds and discuss reasons for their choice.