bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of socioeconomic variables in predicting global wildfire ignition occurrence
Authors: Mukunga Tichaona , Forkel Matthias , Forrest Matthew , Zotta Ruxandra-Maria , Schlaffer Stefan , Dorigo Wouter
Published: February 2023

Wildfires are a pervasive feature of the terrestrial biosphere and contribute large carbon emissions within the Earth system. Humans are responsible for the majority of wildfire ignitions. Physical and empirical models are used to estimate the effects of fires on vegetation dynamics and the Earth system. However, there is no consensus on how human-caused fire ignitions should be represented in such models. 

 We aim to identify which globally available predictors of human activity explain global fire ignitions as observed by satellites. We apply a random forest machine learning framework to state-of-the-art global climate, vegetation, and land cover datasets to predict global fire ignition density remote sensing data. We establish a baseline against which influences of socioeconomic data (cropland fraction, gross domestic product (GDP), road density, livestock density, and grazed lands) are evaluated to determine their effects on fire ignition occurrence predictions. Our results show that a baseline random forest without human predictors captures the spatial patterns of fire ignitions globally but overestimates ignition occurrence, with the highest predictions over Sub-Saharan Africa and South East Asia. Adding human predictors one by one to the baseline model reveals that human variables vary in their effects on fire ignitions, and GDP is the most vital driver of fire ignitions. We also find that high road density leads to decreased ignitions globally despite improved environmental access, mainly because these regions are primarily human settlements and will have fewer fires. A combined model with all human predictors shows that the human variables improve the ignition predictions in most areas of the world; still, some regions, e.g., East Africa, have worse predictions than the baseline model.  

We conclude that an ensemble of human predictors can add value to physical and empirical models. There are complex relationships between the variables, as evidenced by the improvement in bias in the combined model compared to the individual models. 

Furthermore, the variables tested have complex relationships that random forests may struggle to disentangle.  Further work is needed to reach concrete conclusions at a global scale, but rather introduce the need for additional work to detangle the complex regional relationships between these variables, particularly across Central and Eastern Africa, where the full model performs poorly despite the high availability of fire ignition data. 
Increasing of oxygen minimum events in a temperate estuary caused by warming and reduced discharge
Authors: Sanders Tina , Heineke Martina , Götz Flöser , Russnak Vanessa , Husmann Eva , Dähnke Kirstin , Schöl Andreas , Große Fabian , Voynova Yoana G.
Published: February 2023

The Elbe Estuary is strongly impacted by anthropogenic activities such as dredging and eutrophication. Together, these cause oxygen minimum zones (OMZ) regularly during summer in the Hamburg Port area, within the tidal freshwater region of the estuary. Over the last years, this OMZ has expanded spatially and temporally. We present an analysis of an extraordinary oxygen minimum event in June 2022, when an all-time lowest oxygen concentration was observed upstream of the Hamburg Port.We combine data from six transect cruises (early May -late June, 2022) and monitoring stations (2016-2022), to show the decrease of oxygen, and the increasing number of oxygen minimum events. In June 2022, the OMZ moved upstream due to the collapse of a phytoplankton bloom upstream of the tidal weir. This was accompanied by particularly warm temperatures and low river discharge, providing a glimpse into the potential future changes of central European estuaries under climate change.
Adaptation portfolio to combat future climate change impacts in the water sector of the Chao Phraya River Basin, Thailand
Authors: Padiyedath Gopalan Saritha , Hanasaki Naota , Oki Taikan
Published: February 2023

Climate change will increase the intensity and frequency of flood and drought events and the global population exposed to these extreme events, thereby enhancing economic damage. Therefore, adaptation measures should be taken to combat the inevitable consequences of climate change, particularly flooding and water scarcity. However, quantitative and concrete views on what adaptation measures should be taken have yet to be explored, especially in developing countries. Hence, in this study, the effect of several combinations of adaptation measures was examined to address both the future extremes in the Chao Phraya River in Thailand. The selected adaptation measures were (i) structural measures, which include dam construction, dam capacity enhancement, use of water-efficient irrigation equipment, and diversion channels, and (ii) non-structural measures, which include reforestation, changing the reservoir operation rules, and retention area enhancement. Future climate scenarios were constructed from the bias-corrected outputs of three general circulation models from 2080 to 2099 under RCP4.5 and RCP8.5.Future flood and drought risk were analyzed using the number of flooding days and cumulative abstraction to demand (CAD) index, respectively. The major findings that can be drawn from this study are as follows: (i) the structural measures are capable of reducing the number of flooding days and increasing the CAD index; however, this pattern varies from region to region within the basin. (ii) the non-structural measures reduced both flooding days and CAD index, significantly impacting the basin’s water availability during the dry season. The reduction of the CAD index was mainly due to the increased evapotranspiration from the reforested land use that resulted in a decreased runoff. (iii) the adaptation portfolio (combination of structural and non-structural measures) exhibited a reduced number of flooding days and increased CAD index similar to the structural measures. The results revealed that the adaptation measures for flood or drought risk reduction could negatively impact the risk of the other hazard (i.e., reforestation reduces the flood risk but increases the drought risk). Therefore, different combinations of adaptation measures and basin-wide actions would allow us to better address the tradeoffs between these extremes and measures taken at different temporal and spatial scales.
Effect of 3D Topography on Physics-Based Earthquake Ground Motion characteristics.
Authors: Vats Vishal , Joshi Lav , Narayan Jay Prakash
Published: February 2023

This paper presents the effects of 3D conical topography on the pseudo-dynamically simulated ground motion characteristics. The simulation of pseudo-dynamic ground motion has been carried out using a fourth-order accurate staggered-grid time-domain 3D finite-difference method. In the case of numerical simulations, the radiation of seismic energy from the rupture plane as per Brune’s model as well as avoiding the coherency effects is a challenging job for the simulators. The randomization of slip, rise-time, and peak-time of the source time function and the rupture arrival time, as well as the incorporation of fault-roughness and damage zone, play important roles in seismic energy release from the rupture plane as well as in the reduction of currency effects on the high-frequency seismic radiations. Firstly, the ground motions have been simulated for a hypothetical strike-slip Mw 6.0 earthquake. The efficacy of the presented code has been validated with a good match of the computed average pseudo-spectral acceleration (PSA) using the simulated ground motion with that obtained using NGA-West2 GMPEs in the frequency range 0.1–5.0 Hz. The code has been able to correctly incorporate the rupture directivity effect. Further, the effect of 3D conical topography has been estimated with azimuthal coverage of receivers. The effect of the direction of the source on the topographic amplification has also been estimated. It has been observed that topography plays an important role in the amplification of earthquake ground motion. Also, the direction of the source plays an important role in estimating the pattern of topographic amplification.
The vulnerability of tropical peatlands to oil and gas exploration and production
Authors: Lawson Ian , Honorio Euridice , Andueza Luis , Cole Lydia , Dargie Greta , Davies Althea , Laurie Nina , Okafor-Yarwood Ifesinachi , Roucoux Katherine , Simpson Michael , Schulz Christopher
Published: February 2023

The oil and gas industry has a long history of operating in peat-forming regions in the tropics, but the extent to which peatland ecosystems are vulnerable to those operations is not well understood. This knowledge gap is concerning given the continuing drive to explore peatland areas for hydrocarbons. Here we present an analysis of the exposure of tropical peatlands to the oil and gas industry and review what is known of the peatlands’ sensitivity to that exposure. We show that across the tropics, oil and gas infrastructure is more concentrated in peat-forming regions than we would expect by chance alone, which we suggest is likely due to the persistence over geological timescales of basins which can be suitable both for forming oil and gas source rocks, and for encouraging the poorly-drained conditions that support peat accumulation. Focusing on a case study from Peru, we discuss the extent to which peatlands as ecosystems are known to be sensitive to oil industry activities. These sensitivities may include deforestation and habitat degradation/disturbance during survey and exploration work, and contamination by produced water and by oil spills. Drawing on interdisciplinary research, we also explore the socio-economic and cultural consequences of the oil industry on local communities over the past fifty years. In some cases, enhanced immigration and cultural change (e.g. integration into markets) appear to have had profound effects not just on the members of those communities, but also on the extent to which they have used and altered the surrounding peatland ecosystems. We go on to explore the development of environmental safeguards, which have tended to become more stringent over time but which have not yet succeeded in preventing (e.g.) oil spills. We conclude by identifying key areas where further research is needed, notably in exploring the direct effects of oil and gas industry activities on the carbon storage function of peatlands.
Assessment of the impact of expected changes in the frequency of weather patterns on extreme flows in the Upper Danube basin
Authors: Valent Peter , Komma Jürgen , Breinl Korbinian , Bertola Miriam , Haslinger Klaus , Lexer Annemarie , Thanheiser Selina , Homann Markus , Blöschl Günter
Published: February 2023

Several major flood events of recent years have encouraged research focused on a better understanding of climatological and hydrological causes of floods. In practice, these findings can be used in flood risk management, and in the light of ongoing climate change, also in preparing effective adaptation strategies. This study builds on the results of the Wetrax+ research project which combined a stochastic weather generator and a high-resolution fully-distributed rainfall-runoff model to produce a unique dataset of 10 000 years of hourly simulations of air temperatures, precipitations and river discharges in the Upper Danube River basin. As the generated dataset accounted for the expected changes in the frequencies and persistence of the identified weather patterns, it was used to assess the possible changes in the very extreme flows in the study basin. The length of the dataset maintained that numerous flood events that were larger than the most extreme observed floods occurred in the dataset and were available for analysis. The results indicated that on average the floods should occur sooner in the year in most of the Upper Danube sub-basins. Moreover, the frequency of floods associated with weather patterns related to heavy precipitation also increased. Despite the predictions about the future, changes in weather pattern frequencies cannot be taken for granted the results of the study can be useful in identifying the sources and causes of the most extreme floods helping those responsible to focus their mitigation efforts on certain sub-basins.
Statistical-topographical mapping of rainfall over mountainous terrain with the β-IDW approach
Authors: Wienhöfer Jan , Alcamo Lucas , Bondy Jan , Zehe Erwin
Published: February 2023

We present a robust approach for quantitative precipitation estimation (QPE) for water resources management in mountainous catchments, where rainfall sums and variability are correlated with orographic elevation, but density of rain gauges does not allow for advanced geostatistical interpolation of rainfall fields. Key of the method is modelling rainfall at unobserved locations by their elevation-dependent expected daily mean, and a daily fluctuation which is determined by spatial interpolation of the residuals of neighbouring rain gauges, which are scaled according to the elevation difference. The scaling factor is defined as the ratio of covariance and variance, in analogy to the "beta" used in economics.The approach is illustrated for the Chirilu catchments (Chillón, Rímac, Lurín) in the Andes near Lima, Peru. The results are compared to conventional IDW interpolation and a merged national rainfall product. The method results in QPE that are better matching with observed discharges. The β-IDW approach thus provides a robust and flexible means to estimate rainfall input to mesoscale mountainous catchments. 
Driving Mechanisms of an Extreme Winter Sea Ice Breakup Event in the Beaufort Sea
Authors: Davy Richard , Rheinlaender Jonathon , Rampal Pierre , Spensburger Clemens , Korosov Anton , Williams Timothy , Spengler Thomas
Published: February 2023

The loss of thick multiyear sea ice in the Arctic leads to weaker sea ice that is more easily broken up by strong winds. As a consequence, extreme sea ice breakup events may become more frequent, even during the middle of winter when the sea ice cover is frozen solid. This can lead to an earlier onset of the melt season and potentially accelerate Arctic sea ice loss. Such extreme breakup events are generally not captured by climate models, potentially limiting our confidence in projections of Arctic sea ice. We investigated the driving forces behind sea ice breakup events during winter and how they change in a future climate. Our sea ice model is the first to reproduce such breakup events and reveals that the combination of strong winds and thin sea ice is a key factor for these breakups. We found that winter breakups have a large effect on local heat and moisture transfer and cause enhanced sea ice production, but also increase the overall movement of the sea ice cover, making it more vulnerable. Finally, we show that if the Arctic sea ice continues to thin, these extreme breakup events could become even more frequent.
Quantifying changes in stream-landscape connectivity: combining high-resolution data of non-perennial streams and environmental tracers
Authors: von Freyberg Jana , Bujak Izabela , Rinaldo Andrea , van Meerveld Ilja
Published: February 2023

Changes in hydrologic connectivity between streams and the surrounding landscape are among the most important factors that control the temporal variation in streamwater chemistry. In most headwater catchments, the dynamic expansion and contraction of the non-perennial stream network affects and reflects this hydrologic connectivity. Until now, however, the spatiotemporal variations of non-perennial stream networks have been mapped only sporadically and environmental tracer data to explore the dynamic connectivity for these streams are lacking.Within the TempAqua project, we have monitored the temporal variation in environmental tracers (solutes, stable water isotopes) in precipitation, soil- and groundwater, as well as in stream water during rainfall events in the pre-Alpine Erlenbach catchment. We combine these measurements with novel, sub-hourly data on stream network expansion and contraction.Our data show that the total flowing stream length increased rapidly, up to 10-fold, during individual rainfall events. Changes in solute concentrations in streamwater indicate that different water stores become dynamically connected to the stream and disconnect again during subsequent dry periods: at the beginning of an event, the dilution of sulphate and calcium suggest a surface runoff contribution of rainwater at the time of rapid expansion of the network and increasing discharge. As rainfall continues, the stream network expands further due to rising groundwater tables, which is indicated by increased nitrate and sulphate concentrations in the stream. The magnitude and importance of these processes depends more on antecedent wetness conditions than event magnitude.Our observations shed light onto the short-term mechanisms by which non-perennial streams start to flow during rainfall events, and provide new knowledge to address emerging questions on the functional relationships between stream-landscape connectivity, hydrological responses and water quality in headwater catchments, and their vulnerability to global climate change.
Nutrient dynamics along the forest floor – mineral soil continuum
Authors: Schilling Lexie , Vesterdal Lars , Prietzel Jörg , Schack-Kirchner Helmer , Lang Friederike
Published: February 2023

Slow turnover of the forest floor (FF) is often assumed to be related to immobilization of nutrients within the organic matter. However, the FF is also assumed to be an important nutrient source at sites with low nutrient concentrations of the mineral soil. Climate change could threaten FF mediated tree nutrition due to higher turnover rates of the FF. Yet, little is known about on the (de)coupling of nutrient and FF mass turnover and their controls, nor about future responses to a changing climate.Within the research unit FOREST FLOOR (FOR 5315) we aim to identify processes that control the relevance of the FF for tree nutrition as compared to the mineral topsoil. We test the hypotheses that (1) at nutrient poor sites the turnover of C is lower than the turnover of P and N, (2) admixture of minerals to FF material and subsequent biotic formation of mineral-organic associations decreases the pool of organically bound P+N and of easily mobilizable P+N, and (3) that in Norway spruce (Picea abies), FF will contribute more to N and P uptake than in maple (Acer pseudoplatanus), while beech (Fagus sylvatica) will take an intermediate position.Within a natural P and temperature gradient (12 sites), we will test our hypotheses by studying availability to plants and mobilization kinetics of the macronutrients from FF and A horizons using ion exchange resins and membranes. Preliminary tests showed a good suitability of exchanger-resin application to assess P – availability. Moreover, we will benefit from litter bag experiments, and analyze the mobilization of N from labeled litter in a mesocosm approach. Our results will reveal the role of FF for the nutrition of beech, maple and spruce depending on the nutrient status of the mineral soil as well as how climate change is impacting tree nutrition services of the FF.
Spatial and temporal screening of slope motion patterns in alpine environment via unsupervised analysis of large InSAR datasets
Authors: Festa Davide , Novellino Alessandro , Hussain Ekbal , Bateson Luke , Casagli Nicola , Confuorto Pierluigi , Del Soldato Matteo , Raspini Federico
Published: February 2023

The use of SAR interferometry is globally regarded as a powerful tool able to evaluate spatial and temporal patterns of slope motion in alpine areas. Accordingly, the availability of large multi-temporal interferometric datasets compels the scientific community to find efficient value-adding tools to boost the interpretation and management of radar-based information via automated routines in the framework of multi-hazard mapping and analysis. Here it is presented an unsupervised and automated approach based on Principal Component Analysis (PCA) and K-means clustering to detect patterns of natural or human-induced ground deformation from InSAR Time Series. For our proof-of-concept, the focus is placed on Valle d’Aosta region (Northwest Italy) where different landslide types, deep-seated gravitational slope deformations and permafrost creep interact with human activities and infrastructures. The large volumes of Sentinel-1 data produced allows for retrieving horizontal and vertical Time Series from multi-geometry data fusion of LOS InSAR measurements. Therefore, the added benefit of combining ascending/descending InSAR data and interpolating displacements in time at different time steps is here explored prior to data dimensionality reduction and feature extraction through PCA. The retrieved principal components serve as a continuous solution for cluster membership indicators in the K-means clustering method, allowing to define spatially and temporally coherent displacement phenomena. The signal of the ground deformation clusters is deconstructed into the underlying trend and seasonality components to enhance the interpretability of the classified satellite InSAR features. Using InSAR Time series data spanning 2014-2020, the proposed framework detects several mass wasting processes and anthropogenic deformations with both linear and seasonal displacement behaviours. The results demonstrate the potential applicability of the proposed transferable approach to the development of automated ground motion analysis systems.
Experimental comparison between the turbidity and density currents
Authors: Kyoi Minori , Nomura Shun , Oshima Ippei , Nishiura Daisuke , Furuichi Mikito , Tani Kazuo
Published: February 2023

Understanding the mechanism of turbidity currents is important for siting submarine cables and pipelines. It is because the turbidity currents can transport a large amount of sediment in long distance that causes severe damages to these buried linear structures. It is not clear why turbidity currents can gain and sustain such a large amount of kinetic energy. One of possibilities to explain this process is a drag reduction which reduces the turbulent energy due to the inclusion of fine particles as previous studies reports. However, the influence of fine particles to their flow characteristics has not been fully elucidated. Thus, in this study, a series of model tests were conducted to compare the horizontal steady flows of silica suspension and NaCl solution in a flume. The test results show that the flow characteristics of silica suspension were different from that of NaCl solution. These differences are considered to be caused by silica particles, and it is suggested that drag reduction by fine particles would be taken place in turbidity currents.
Influence of Tiber River plume on phytoplankton primary production
Authors: Madonia Alice , Amore Eleonora , Cerino Federica , Cibic Tamara , Coppini Giovanni , Fersini Giorgio , Fornasaro Daniela , Kralj Martina , Piermattei Viviana , Marcelli Marco
Published: February 2023

River plumes have a significant impact on phytoplankton primary production by carrying high nutrient loads, suspended particles and dissolved organic matter into the seawater.Dynamic processes mainly modulate nutrient availability as well as light attenuation along the water column thus influencing marine phytoplankton distribution along the plume gradient, also according to the seasonal variability of the river flow.A series of oceanographic cruises have been conducted since 2020 to examine how physical processes influence phytoplankton dynamics within the entire physiographic unit, which extends between Capo d'Anzio and Capo Linaro. A high phytoplankton abundance was observed both at the surface and bottom depths up to a bathymetry of 40-60 meters. At the surface, it was directly related to the Tiber River plume, while at the bottom it seemed to be linked to sediment resuspension phenomena. Going offshore, the distribution of phytoplankton along the water column assumed the Typical Tropical Structure (TTS) trend with a well-formed Deep Chlorophyll Maximum (DCM) around 60 to 90 meters depth.In light of these findings, to deepen our understanding of these phenomena, a detailed campaign along the river mouth was carried out in May 2022 in collaboration with the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS to collect hydrological (temperature, conductivity - salinity, density-, dissolved oxygen) and biogeochemical (PAR, downwelling and upwelling irradiance, nutrients, phytoplankton photosynthetic efficiency, composition and biomass, TSM, CDOM) data. 
Achievements of the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC)
Authors: Śliwińska Justyna , Kur Tomasz , Nastula Jolanta , Wińska Małgorzata , Dobslaw Henryk , Partyka Aleksander ,   2nd EOP PCC Participants
Published: February 2023

The accurate determination of Earth Orientation Parameters (EOP) requires post-processing of observational data collected from various space geodetic techniques, which causes delays in providing EOP solutions. However, receiving instantaneous information about EOP in real time is crucial in precise positioning and navigation. Therefore, EOP prediction (particularly short-term) has become a subject of increased attention within the international geodetic community.In the light of the developments of advanced geodetic data processing, modelling effective angular momentum functions, and developing new prediction methods, a re-assessment of the various EOP predictions was pursued in the frame of the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC). The campaign was run by Centrum Badań Kosmicznych Polskiej Akademii Nauk (CBK PAN), in cooperation with GeoForschungsZentrum (GFZ) and under the auspices of the International Earth Rotation and Reference Systems Service (IERS). The campaign started on 1st September 2021 and finished on 28th December 2022, giving 7327 submitted predictions within 82 weeks. The campaign was a great success of the geodetic community thanks to international cooperation.The presentation provides the summary of the 2nd EOP PCC. We focus on the recap of the statistics on the involved participants, i.e., the number of prediction methods and input data. Then we will present the accuracy of EOP predictions based on the mean absolute error computed for IERS 14 C04 solution as a reference. Additionally, we present the quality of predictions in clusters created from the campaign participants (IDs) based on their modern prediction methods combined with input data (EOP observations and data on the Earth’s surficial fluids) We conclude the presentations with plans for the prediction assessment, also in terms of the possible continuation of the campaign involving new release of IERS C04 20.
Attributing runoff changes to present and future climate projections across Europe
Authors: Clemenzi Ilaria , Du Yiheng , Pechlivanidis Ilias
Published: February 2023

Weather and climate strongly influence the hydrology of natural and managed river basins. Changes in these forcings affect the water resources and hydrological extremes, i.e., floods and droughts, in time and space. Attributing the effect of climatic drivers on present and future runoff allows to understand the hydrological response of river basin to changing climate at the local and regional scale. Here, we investigated the runoff changes, including hydrological extremes, across Europe in the early (2010-2040), mid (2041-2070) and late (2070-2099) century. We used runoff simulations from the E-HYPE hydrological model and the bias-adjusted EURO-CORDEX climate model projections. The sensitivity of runoff changes to the climatic factors (precipitation and evapotranspiration) compared to the reference period (1981-2000) was evaluated with the climatic elasticity method through a Budyko approach. In addition, to address lack of robustness in our insights, we assessed the spatial consistency and uncertainty of the runoff changes due to the ensemble variability. Results showed that the sensitivity of runoff changes to climate change varies depending on the climatic gradient and basin physiographic properties. These results are a step towards enhanced hydro-climate services that allow attribution of (extreme) events to climate change.
Automatic and Open-Source Model with Forecasts for Climate Policy and Economics
Authors: Schwarz Moritz , Kurle Jonas , Pretis Felix , Martinez Andrew
Published: February 2023

Economic forecasts of the effects of climate policy are frequently based on static economic theory and are not regularly updated. Moreover, their source code is often not public, making replication and critical evaluation difficult. The predominant models used for climate policy narratives, so called Integrated Assessment Models, are rarely estimated using empirical data and are hence highly affected by the modeller’s assumptions. To improve the estimation of likely effects of climate policy, we present the “Aggregate Model”, a data-based model for dozens of countries that flexibly estimates and forecasts economic time series and allows for the simulation of different climate policy options. Data-based models need to incorporate long-term trends and account for both structural breaks and outliers that otherwise distort the model estimates and may lead to systematic forecast error. Our model uses various techniques from the time series literature, such as indicator saturation, model selection, and testing for co-integration. These techniques are automated to a high degree, simplifying the model estimation procedure.  The Aggregate Model is distributed as an open-source R package, allowing for simple replication and modification by users through its modular structure.
Assessment and Validation of Daily Enlil and EUHFORIA Simulations During 2019-2022
Authors: Barnes David
Published: February 2023

The Heliospheric Expert Service Centre (H-ESC), part of ESA’s space weather service network, serves to provide existing heliophysics models for the provision of alerts and forecasts of space weather conditions at Earth and throughout the heliosphere. This is achieved by means of remote sensing and in-situ measurements of space weather transients, including Coronal Mass Ejections and high-speed solar wind streams, combined with advanced MHD modelling to predict their arrival times at points of interest in the heliosphere. Two such models include the European Heliospheric Forecasting Information Asset (EUHFORIA) and the ENLIL model operated by the UK Met Office, both of which are currently federated through the H-ESC portal. As a means to test both models, we perform daily runs of the EUHFORIA model using the same inputs (GONG magnetograms and CME cone-files) as the Met Office ENLIL simulations since the beginning of 2019, which are compared to real solar wind observations near Earth. We employ well-established model validation methodology by deriving contingency tables and the associated skill scores for both models as a means to assess their ability to make accurate space weather forecasts during this period of parallel operation.
Abrupt Change in the Lower Thermospheric Mean Meridional Circulation during Sudden Stratospheric Warmings and its Impact on Trace Species
Authors: Orsolini Yvan , Zhang Jiarong , Limpasuvan Varavut
Published: February 2023

Based on the hourly output from the 2000–2014 simulations of the National Center for Atmospheric Research’s vertically extended version of the Whole Atmosphere Community Climate Model in specified dynamics configuration, we examine the roles of planetary waves, gravity waves and atmospheric tides in driving the mean meridional circulation in the lower thermosphere and its response to the sudden stratospheric warming phenomenon with an elevated stratopause in the northern hemisphere. Sandwiched between the two summer-to-winter overturning circulations in the mesosphere and the upper thermosphere, the climatological lower thermosphere mean meridional circulation is a narrow gyre that is characterized by upwelling in the middle winter latitudes, equatorward flow near 120 km, and downwelling in the middle and high summer latitudes. Following the onset of the sudden stratospheric warmings, this gyre reverses its climatological direction, resulting in a “chimney-like” feature of un-interrupted polar descent from the altitude of 150 km down to the upper mesosphere. This reversal is driven by the westward-propagating planetary waves, which exert a brief but significant westward forcing between 70 and 125 km, exceeding gravity wave and tidal forcings in that altitude range. The attendant polar descent potentially leads to a short-lived enhanced transport of nitric oxide into the mesosphere (with excess in the order of 1. parts per million), while carbon dioxide is decreased.
Estimating the rupture directivity and source parameters of moderate to small earthquakes using the second seismic moment
Authors: Cuius Arianna , Meng Haoran , Saraò Angela , Costa Giovanni
Published: February 2023

Rupture processes of large earthquakes have been studied by seismic waveform analysis and directivity effects have also been observed in moderate and small earthquakes. This effect leads to azimuthal and spectral variations in ground motion that can be used to estimate the fault plane orientation or a predominant rupture propagation direction in a particular region or during a seismic sequence. For moderate-to-strong events, directivity at low frequencies can result in potentially destructive pulses with large ground motions, while at high frequencies and for small-to-moderate events, the most pronounced effect is the shift in corner frequencies that results in high-frequency energy arriving in short time intervals. It is therefore of the utmost importance to estimate the directivity effects in engineering applications and seismological studies of earthquake sources. While some methods appear to work well for high magnitude earthquakes, determining directivity and source parameters for small to moderate magnitude earthquakes remains a challenge. One of the most common methods to estimate the directivity from moderate to small earthquakes relies on measuring the duration of the source pulse (the apparent source time function) at each location and then modeling it using a line source. Some approaches rely on the deconvolution of waveforms by an empirical Green’s function (eGf), to overcome the problems associated with the presence of path and site effects.A promising approach for estimating the rupture directivity effect and associated source properties is based on the calculation of the second seismic moments. In this study we apply the method based on the calculation of the second seismic moments to estimate the rupture process and source parameters to study a Mw 4.7 earthquake that occurred in central Italy during the 2016 - 2017 seismic sequence recorded by the RAN (Rete Accelerometrica Nazionale) and RSN (Rete Sismica Nazionale) italian networks.We first used synthetic apparent source time functions calculated from a geometric source model obtained from a real event to test the robustness of the method. Then, we applied the second-seismic moment method and the approach based on high-frequency S wave amplitude variations versus source azimuths analysis with an empirical Green's function deconvolution approach and compare the results. 
First results from ModE-Sim - A medium size AGCM ensemble to study climate variability during the past 600 years
Authors: Hand Ralf , Hövel Laura , Samakinwa Eric , Brönnimann Stefan
Published: February 2023

ModE-Sim is a medium size ensemble that can be used to study climate variability of the past 600 years. It was created using the atmospheric general circulation model ECHAM6 in its LR version (T63L47). With 60 ensemble members between 1420 and 1850 and 36 ensemble members from 1850 to 2009 ModE-Sim consists of 31620 simulated years in total. The dataset was designed as an input for a data assimilation procedure that combines historical climate informations with additional constraints from a climate model to produce a novel gridded 3-dimensional dataset of the modern era. Additionally, ModE-Sim on its own is also suitable for many other applications as its various subsets can be used as initial condition ensemble to study climate variability. We show that the ensemble has a realistic response to external forcings and that it is capable of capturing internal variability on monthly to annual time scales. At the example of heat waves we show that ModE-Sim can even be useful to study extreme events.
Assessing the spatial representativeness of water storage variations from superconducting gravimeter residuals by regional CG-6 surveys
Authors: Reich Marvin , Novak Adam , Thoss Heiko , Wöhnke Viviana , Eicker Annette , Weigelt Matthias , Güntner Andreas
Published: February 2023

Regularly updated information about states, trends and dynamics of water storage in different spatio-temporal scales has gained increasing importance, especially with a perspective on hydrological extreme events as well as water management issues. Monitoring these storage dynamics is challenging due to the spatial heterogeneity and the contribution of different storage compartments (e.g., near-surface soil moisture, deep unsaturated zone, groundwater). A promising monitoring technique is gravimetry, well suited for the integral observation of different storage compartments. While satellite gravimetry (GRACE, GRACE-FO) provides information on storage variations at a spatially large scale with low spatial and temporal resolution, the opposite is true for terrestrial gravimetry. Ways to combine both satellite and terrestrial gravimetry are addressed and evaluated within the German Collaborative Research Centre TerraQ. For the terrestrial approach, several gravimeters were deployed for continuous monitoring at different locations within Germany. The work presented here takes as an example a forest site within the TERENO observatory of north-eastern Germany, with continuous observations  of a superconducting gravimeter (iGrav 033) since 2017.The signal footprint of such a gravimeter typically covers a radius of 0.5 to 2 km, depending on local topography, although most of the signal originates from the direct vicinity of the instrument. Also, the device can sense mass changes beyond this distance, depending on their magnitude (e.g., tides, atmosphere or global hydrological effects). In hydro-gravimetric studies, all non-desired signals are typically removed, resulting in residuals that are representative for the local hydrological effects only. Towards comparing and combining these terrestrial measurements with satellite products, one open question is how representative the terrestrial gravity residuals are in a regional context. With the goal to assess this spatial representativeness, we conducted seasonal relative gravity surveys with 2 CG-6 gravimeters in an extent of roughly 25 by 30 km around the iGrav installation. The survey data were combined with spatial information about topography and land-use. Water storage changes could thus be attributed to each survey point. A joint analysis with the continuous measurements of the superconducting gravimeter at the permanent installation site allowed for mapping the spatial patterns and similarities among all sites.This study is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 434617780 – SFB 1464
The characteristics and effects of tides on the general circulation of the Mediterranean Sea
Authors: McDonagh Bethany , Clementi Emanuela , Pinardi Nadia
Published: February 2023

Tidal forcing was not included in a large proportion of numerical models of the ocean from the past but is known to be necessary to forecast the ocean accurately, since tides dissipate around 3.5TW of energy in the global ocean, and are an important driver of mixing. The inclusion of tides in models affects not only the near-field dynamics such as local temperature and salinity, but also large-scale circulations that influence the entire global ocean. In the Mediterranean Sea, amplitudes of tides are typically low, but are known to have effects both at local scales where tidal amplitude is larger, and across the entire basin. However, their impact on processes such as circulation, vertical mixing, and internal tides at the basin scale are not well known. In this work, the characteristics of tides in the Mediterranean Sea were investigated using the hydrodynamic model NEMO (Nucleus for European Modelling of the Ocean) version 3.6, corresponding to the Copernicus Monitoring Environment Marine Service (CMEMS) system, a baroclinic forecasting model for the Mediterranean Sea, integrated over five years. Analysis of potential and kinetic energy due to tides showed that tides have impacts across a wide variety of spatial and temporal scales in the basin, both at the surface and at deeper levels. Increased kinetic energy at depth in the basin led to an exploration of internal tides, which have not been previously studied at the scale of the Mediterranean Sea using a numerical approach. Additionally, the effects of tides on salt transport through the Gibraltar Strait were analysed, and numerical results were compared to a two-layer box model of the Gibraltar Strait and Mediterranean Sea. This demonstrated the utility of simple theoretical frameworks to understand dynamics in the region, while highlighting the impact of increased vertical mixing in the Gibraltar Strait due to internal tides.Our improved understanding of the impacts of tides across temporal and spatial scales lays out an argument for the inclusion of tides in ocean models ranging from local to global, and from short timescales to long term climate modelling. Our analysis also provides a novel understanding of dynamics such as internal tides and transport of salinity in the Mediterranean region.
Can we model forest demography globally? Benchmarking of state-of-the-art Demographic DGVMs
Authors: Eckes-Shephard Annemarie , Argles Arthur , Brzeziecki Bogdan , Cox Peter , De Kauwe Martin G. , Esquivel Muelbert Adriane , Fisher Rosie A. , Knauer Jürgen , Koven Charles D. , Lehtonen Aleksi , Longo Marcos , Luyssaert Sebastiaan , Marqués Laura , Moore Jon , Needham Jessica F. , Olin Stefan , Peltoniemi Mikko , Sitch Steven , Stocker Benjamin , Weng Ensheng , Zuleta Daniel , Pugh Thomas
Published: February 2023

Forests in Dynamic Global Vegetation Models (DGVMs) have historically been simulated as area-averaged plant functional types in each gridcell instead of representing communities of trees of different sizes and ages (demography). Just as the behaviour of a tree differs according to its ontogeny, so the behaviour of forests is known to differ depending on their demography. Accurately simulating demography is therefore key in order to address questions on afforestation and management strategies, as well as assessments of resilience of forests to disturbances such as drought and fire or diversity changes after a disturbance. Ultimately, demography determines the overall forest biomass in natural forests and is a key arbiter of growth and mortality rates. DGVMs are now able to simulate size and age structure of the trees in forests. However, these models have so far not been benchmarked alongside each other.We evaluate 6 DGVMs (BiomeE, CABLE-POP, FATES, LPJ-GUESS, JULES-RED, ORCHIDEE) against observations on regrowth dynamics as well as natural forests at boreal, temperate and tropical sites. We examine whether the models capture observed regrowth dynamics after disturbance, well-known stand size structure and well-established processes such as self-thinning. We outline the planned route forward towards a standardised international benchmarking framework for demographic DGVMs.
Assessment of Continental Scale Water Balance for Indian Land Data Assimilation System (ILDAS)
Authors: Saharia Manabendra , Magotra Bhanu , Prakash Ved , Getirana Augusto
Published: February 2023

A land data assimilation system plays a pivotal role in effective water resources management by providing reliable estimates of various land surface states and fluxes including water balance components. An Indian Land Data Assimilation System (ILDAS) has been setup that aims to provide spatially consistent, high resolution and reliable estimates of land surface states, water balance and energy fluxes over the Indian mainland. The ILDAS is built on NASA’s Land Information System Framework (LISF), which is an open-source framework that enables a multi-model, multi-data approach to terrestrial modeling. In this study, we evaluated the water balance components simulated using ILDAS while driven by three reanalysis meteorological forcing datasets: Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), and Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) and ECMWF's ERA5. The multi-site autocalibration is performed on multiple catchments to further improve the performance of ILDAS. We have used Kling-Gupta Efficiency (KGE) and its components to evaluate the major components of the terrestrial water balance: surface runoff, soil moisture, terrestrial water storage anomalies, evapotranspiration, and monthly mean streamflow, against a combination of satellite and in-situ observation datasets. We also assessed the uncertainty and bias due to spatio-temporal heterogeneity in the forcing precipitation by validating against gauge-based gridded precipitation provided by Indian Meteorological Department (IMD). Overall, considering nationwide median KGE scores, CHIRPS showed the highest performance for surface runoff and streamflow. However, MERRA-2 performed the highest in soil moisture simulation whereas ERA5 showed best results in total evapotranspiration. 
Seasonal and regional sensitivity of Arctic sea ice
Authors: Ritschel Markus , Notz Dirk
Published: February 2023

We examine the seasonal and regional evolution of sea-ice coverage in the Arctic in response to changes in the forcing. Using satellite and reanalysis data in combination with CMIP6 model simulations, we build on previous studies that have found a strong linear relationship between the September sea-ice area of the northern hemisphere and global atmospheric air temperature (TAS) as well as anthropogenic CO2 emissions. Instead of focusing on the whole Arctic and September sea ice only, we perform sensitivity analyses on higher-resolved regional and seasonal scales, aiming to identify the atmospheric and oceanic drivers that govern the evolution of sea-ice coverage on these scales and to derive simple empirical relationships that describe the impact of these processes. We find clear linkages also on these higher-resolved scales, with different regions and different seasons showing diverse sensitivities of sea-ice area evolution with respect to TAS and anthropogenic CO2. Furthermore, we use a multivariate metric to quantify the "quality" of a single simulation matching the observations, thereby considering the different sensitivities of all seasons of the year. Building the combined covariance matrix of observations and simulations as a measure of the joint uncertainties, we can determine how "close" to the observations every single member of the simulations is. This allows us to separate models whose sensitivities are in overall good agreement with the observations from those that are apparently not capable of properly simulating the response of the sea ice to the forcing throughout all months. Based on our findings we can infer the dominant drivers that force Arctic sea-ice evolution on a regional and seasonal scale and also derive projections for the future evolution of Arctic sea ice for different climate scenarios based on simple empirical relationships that can directly be estimated from observational records.