bluuebunny/crossref_metadata_2025 huggingface dataset:
Can Throat Auroras Create Polar Cap Patches？
Authors: Zhang Duan , Zhang Qinghe , Oksavik Kjellmar , Xu Tong , Xing Zanyang , Lyons Larry , Han Desheng , Zhang Hongbo , Ma Yuzhang , Hu Zejun , Liu Jianjun , Wang Yong , Wang Xiangyu
Published: February 2023

Throat auroras and polar cap patches are common phenomena in the polar ionosphere. An observation campaign was organized, with all-sky imagers at Yellow River Station in Ny-Ålesund in Svalbard, the EISCAT Svalbard Radar, and coordinated low-altitude spacecraft observations. During periods of radial interplanetary magnetic field (IMF), observations showed that poleward moving throat auroras were linked to poleward moving ionization patches. Throat auroras are produced by soft-electron precipitation associated with dayside magnetic reconnection. The red line intensity of throat auroras is found to be correlated with dayside reconnection events. Dense plasma from lower latitudes was transported poleward by enhanced convection associated with the throat auroras to form electron density patches. This is potentially a new patch formation mechanism that is associated with throat auroras and magnetic reconnection for radial IMF. Moreover, the patches were found to E × B drift in the anti-sunward direction.
PEAT-FWI: Improving the Fire Weather Index for peatlands with Hydrological Modeling and L-band Microwave Observations
Authors: Mortelmans Jonas , Felsberg Anne , De Lannoy Gabriëlle , Veraverbeke Sander , Field Robert , Andela Niels , Bechtold Michel
Published: February 2023

The Fire Weather Index (FWI) is used worldwide to estimate the danger of wildfires. The FWI system integrates meteorological parameters and empirically combines them into several moisture codes, each representing a different fuel type. These moisture codes are then used in combination with wind speed to estimate a fire danger. Originally, the FWI system was developed for a standard jack pine forest, however, it is widely used by fire managers to assess the fire danger in different environments as well. Furthermore, it is often also used to assess the vulnerability of organic soils, such as peatlands, to ignition and depth of burn. The utility of which is often questioned. This research aims at improving the original FWI for northern peatlands by replacing parts of the original, purely weather-based FWI system with satellite-informed model estimates of peat moisture and water level. These come from a data assimilation output combining the NASA catchment model, including the peat modules PEATCLSM, and Soil Moisture and Ocean Salinity (SMOS) L-band brightness temperature observations. The predictive power of the new, peat-specific FWI (PEAT-FWI) is evaluated against the original FWI against fire data of the global fire atlas from 2010 through 2018 over the major northern peatlands areas. For the evaluation, the fires are split up in early and late season fires, as it is hypothesized that late fires are more hydrological driven, and the predictive power of the PEAT-FWI will thus differ between the two types of fires. Our results indeed indicate that the PEAT-FWI improves the predictive capability of estimating fire risk over northern peatlands in particular for late fires. By using a receiver operating characteristics (ROC) curve to evaluate the predictive power of the FWI against a random estimate, the area under the curve increases by up to 10% for the PEAT-FWI compared to the original FWI. The recent version 7 release of the operational Soil Moisture Active Passive (SMAP) Level-4 Soil Moisture Data Assimilation Product now includes PEATCLSM, thus, the proposed PEAT-FWI is straightforward to include in operational FWI products.
Validation of uncertainty estimates in digital soil mapping
Authors: Schmidinger Jonas , Heuvelink Gerard B.M.
Published: February 2023

There is growing interest in the field of digital soil mapping (DSM) to quantify the underlying uncertainty of point predictions through different probabilistic prediction models. Uncertainty in DSM is often described in the format of a prediction interval (PI). Yet, PIs or uncertainty estimates in general are only of value for end users if they have good quality, i.e. when they are reliable. Reliability refers to the consistency between predicted conditional probabilities and observed frequencies of independent validation data. Ideally, PIs are also sharp, which refers to the concentration of probabilistic information, i.e. the narrowness of conditional probability distributions. The prediction interval coverage probability (PICP) is currently used in DSM to assess the reliability of PIs but it is ignorant to a potential one-sided bias of its bounding quantiles. Therefore, we propose to complement the current validation procedure with new metrics suggested in the broader probabilistic literature. This includes metrics that do not only evaluate uncertainty estimates in PI format but also quantiles or full conditional probability distributions. The newly proposed metrics are the quantile coverage probability (QCP), the probability integral transform (PIT) and so-called proper scoring rules for relative comparisons. Examples of scoring rules are the continuous ranked probability score (CRPS), which can be decomposed into a reliability part (RELI) and the interval score (IS). Sharpness can be evaluated through the prediction interval width (PIW). We illustrated the use of the various metrics in a case-study using soil pH data from The Land Use and Coverage Area Frame Survey (LUCAS). Thereby, uncertainty estimates of five different models were compared: Kriging with external drift (KED), quantile regression forest (QRF), quantile regression post-processing of a random forest (QRPP RF), quantile regression neural network (QRNN) and a reference null-model (NM).  KED, NM and QRPP RF showed very good reliability according to QCP, PICP, PIT and RELI. QRF was slightly pessimistic in the centre and QRNN very overoptimistic at the edges of the conditional probability distributions. Despite this, QRF performed best according to mean CRPS and mean IS because it produced fewer outliers at the edges. As expected, NM had the lowest sharpness, i.e. the largest PIW values. Sharpness of the other models was overall similar but QRNN had sharper predictions at the edges and QRF was less sharp in the centre of the conditional probability distributions. Lastly, we also generated PIW maps to indicate the spatial uncertainty of the five prediction models. The spatial variability of PIW was larger for QRF, QRNN and QRPP RF in comparison to KED. Whereas with NM, PIW was completely uniform. 
Global evaluation of runoff simulation from climate, hydrological and land surface models
Authors: Hou Ying , Guo Hui , Yang Yuting , Liu Wenbin
Published: February 2023

Recent advances in global hydrological modeling yield many global runoff datasets that are extensively used in global hydrological analyses. Here, we provide a comprehensive evaluation of simulated runoff from 21 global models, including 12 climate models from CMIP6, six global hydrological models from the Inter-Sectoral Impact Model Inter-Comparison Project (ISMIP2a) and three land surface models from the Global Land Data Assimilation System (GLDAS), against observed streamflow in 840 unimpaired catchments globally. Our results show that (i) no model performs consistently better in estimating runoff from all aspects, and all models tend to perform better in more humid regions and non-cold areas; (ii) the interannual runoff variability is well represented in ISIMIP2a and GLDAS models, and no model performs satisfactorily in capturing the annual runoff trend; (iii) the runoff intra-annual cycle is reasonably captured by all models yet an overestimation of intra-annual variability and an early bias in peak flow timing are commonly found; and (iv) model uncertainty leads to a larger uncertainty in runoff estimates than that induced by forcing uncertainty in ISIMIP2a, and model uncertainty in GLDAS is larger than that in ISIMIP2a. Finally, we confirm that the multi-model ensemble is an effective way to reduce uncertainty in individual models except for CMIP6 regarding mean annual magnitude and annual runoff trend. Overall, our findings suggest that assessments/projections of runoff changes based on these global outputs contain great uncertainties and should be interpreted with caution, and call for more advanced, observation-guided ensemble techniques for better large-scale hydrological applications.
Fusion of satellite precipitation products and ground-based measurements using LightGBM with a focus on extreme quantiles
Authors: Tyralis Hristos , Papacharalampous Georgia , Doulamis Anastasios , Doulamis Nikolaos
Published: February 2023

Satellite precipitation products are not accurate in representing the actual precipitation measured by gauges. To improve their accuracy, machine learning algorithms are applied in regression settings with ground-based measurements as dependent variables and satellite precipitation data as predictor variables. Here we examine the case of light gradient-boosting machine (LightGBM) for correcting daily IMERG (Integrated Multi-satellitE Retrievals for GPM) and PERSIANN (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks) precipitation data using daily precipitation measurements in the contiguous US. Our demonstration especially focuses on the estimation of quantiles of the conditional probability distribution of daily precipitation at given points, with emphasis on extreme values.
Using machine learning to improve dynamical predictions in a coupled model
Authors: He Zikang , Brajard Julien , Wang Yiguo , Wang Xidong , Shen Zheqi
Published: February 2023

Dynamical models used in climate prediction often have systematic errors that can bias the predictions. In this study, we utilized machine learning to address this issue. Machine learning was applied to learn the error corrected by data assimilation and thus build a data-driven model to emulate the dynamical model error. A hybrid model was constructed by combining the dynamical and data-driven models. We tested the hybrid model using synthetic observations generated by a simplified high-resolution coupled ocean-atmosphere model (MAOOAM, De Cruz et al., 2016) and compared its performance to that of a low-resolution version of the same model used as a standalone dynamical model.To evaluate the forecast skill of the hybrid model, we produced ensemble predictions based on initial conditions determined through data assimilation. The results show that the hybrid model significantly improves the forecast skill for both atmospheric and oceanic variables compared to the dynamical model alone. To explore what affects short-term forecast skills and long-term forecast skills, we built two other hybrid models by correcting errors either only atmospheric or only oceanic variables. For short-term atmospheric forecasts, the results show that correcting only oceanic errors has no effect on atmosphere variables forecasts but correcting only atmospheric variables shows similar forecast skill to correcting both atmospheric and oceanic errors. For the long-term forecast of oceanic variables, correcting the oceanic error can improve the forecast skill, but correcting both atmospheric and oceanic errors can obtain the best forecast skill. The results indicate that for the long-term forecast of oceanic variables, bias correction of both oceanic and atmospheric components can have a significant effect.
How to deal with uncertain data for property loss assesment due to Natural Hazards ?
Authors: Lobligeois Florent , Magnan Guillaume
Published: February 2023

Natural hazards are a systemic risk for the insurance industry and the assesment of the stochastic losses covered by the underwritten policies is fundamental to ensure the insurance company solvability and the protection of its customers. AXA Group develops and operationnaly uses complex sophisticated modeling platorms to quantify the impact of natural events in terms of insured losses: from hazard physical-modeling to risk vulnerability and financial computations. Unfortunately, in practice, the loss assesments are strongly impacted by the model uncertainties (theoretically challenging and computationally expensive) and the quality of the input data.A basic framework to quantify the impact of data quality on modeled loss results has been developed within AXA Group to produce pragmatic and operational loss best-estimates taking into account low-quality or unknown input data. This Data Quality Risk (DQR) framework which relies on four pillars, (i) availibility (ii) granularity (iii) completeness and (iv) reliability, is applied on a list of predefined risk drivers (risk characteristics, geocoding ...) and then loads the model results. The DQR methodology is operationally used for a financial solvability model and serves as an essential input to natural event loss assesment and (re)insurance protection purposes.
Water and Energy budgets on short and long timescales
Authors: Petch Samantha , Haines Keith , King Rob , Dong Bo , Quaife Tristan
Published: February 2023

We have aimed to improve the understanding of regional water and energy budgets in large catchments from observations, focusing on the period 2002-2013. To do this we have utilised new available satellite data from the Gravity Recovery and Climate Experiment (GRACE).  Despite recent improvements in remote sensing capabilities, we still see inconsistencies amongst datasets. Observed surface energy fluxes from CERES and FluxCOM indicate unrealistic increases/decreases in surface energy storage over different catchments. We also see imbalances in the water budget, suggesting inaccuracies in the measurements. In order to assess these imbalances, we introduce a flux-inferred surface storage (FIS) for both water and energy, based on integrating the flux observations. This exposes mismatches in seasonal water storage as well as important interannual variability. We have produced optimised estimates for each component of the terrestrial water and energy budgets based on observations and their relative uncertainties. Our new optimisation approach ensures that flux estimates are consistent with total water storage changes from GRACE on short (monthly) and longer timescales, while also balancing a coupled long term energy budget. Flux adjustments remain small and are evaluated using a chi squared test. By using multiple data products, the optimisation reduces formal uncertainties on the budget variables. When compared with results from previous literature, our estimates show good agreement with GRACE variability and trends on account of the multiple timescale constraints imposed during the optimisation. We next aim to extend our approach to include carbon budgets alongside the water and energy budgets to produce a truly coupled Earth system cycling analysis, with applications such as testing Earth and climate circulation models.
Regional modeling of peripheral glaciers in Greenland: Implications for mass balance, freshwater runoff, and sea level rise
Authors: Shafeeque Muhammad , Malles Jan-Hendrik , Vlug Anouk , Marzeion Ben , Möller Marco , Eis Julia
Published: February 2023

Peripheral glaciers (PGs, i.e., glaciers that are dynamically decoupled from the ice sheet) play a significant role in the mass balance and freshwater runoff of Greenland's land ice. Their evolution has implications for the sea level, global climate and ocean circulation, as well as for coastal communities and ecosystems. In order to accurately model the contribution of PGs to Greenland's overall mass balance and freshwater supply, it is necessary to consider their characteristics that set them apart from the main ice sheet. In this study, we used the Open Global Glacier Model (OGGM) to conduct large-scale regional modeling of approximately 19,000 PGs and project future mass losses, freshwater runoff, and sea level contributions under different climate scenarios. Our results show that PGs are likely to experience 29 % to 52 % of mass loss compared to their 2020 levels by the end of the 21st century, resulting in 10 mm to 19 mm of sea level rise under SSP126 and SSP585, respectively. Under the high emission scenario, PGs are expected to contribute 184 Gt yr-1 of liquid freshwater and 3 Gt yr-1 of calved solid ice to the ocean during 2020-2100, affecting ocean density, circulation, and mixing. Peakwater is projected for the 2080s under SSP585, after which annual freshwater contributions are expected to decline due to reduced glacier area. Regional mass and freshwater balance differences were found to be influenced by local climate, ocean-ice interaction, proportion of marine-terminating glaciers, and initial glacier volume. The central-west, southeast, and central-east subregions will experience the largest mass losses (79 %, 69 %, and 63 % of mass in 2020), with peakwater occurring earlier than for all PGs considered together under SSP585. The northeast subregion is expected to contribute 35 % of total liquid freshwater, 73 % of solid ice calving, and 37 % of sea level rise, despite lower mass loss (wrt 2020) due to regional conditions (i.e., climate, glacier geometries, and surrounding ocean). Submarine melting is likely to impact the mass balance of marine-terminating PGs, but further research is needed to explore this effect at a regional scale. This study highlights the importance of considering the distinct behavior of PGs in modeling Greenland's freshwater balance and understanding the factors that influence their mass changes. 
How changes in ignition sources influence fire probability in the Amazon and Cerrado biomes: a perspective based on frontier age
Authors: Ribeiro Andreia F. S. , Santos Lucas , Uribe Maria R. , Silvestrini Rafaella A. , Rattis Ludmila , Macedo Marcia N. , Morton Douglas C. , Randerson James T. , Seneviratne Sonia I. , Zscheischler Jakob , Brando Paulo M.
Published: February 2023

Agricultural expansion and ongoing climate change are rapidly altering the fire regime of natural ecosystems along the Cerrado-Amazon biome boundary. While agricultural intensification has driven a decrease in fire ignitions in some regions, agricultural expansion has increased fire usage in other landscapes for deforestation and managing pasturelands. These contrasting patterns of fire activity across different land-use frontiers limits our ability to accurately predict where and when fires may occur, particularly under the context of climate change.To predict fire activity with land-use transitions, we modelled fire probability as a function of the age of different land-use transitions across the Amazon and Cerrado. We investigated annual land-use and associated burned areas based on the MapBiomas Collection 6.0 and MapBiomas Fire Collection 1.0 data, respectively, from 1986 to 2020. This allowed us to quantify how the time-since conversion of native vegetation (forest, savanna, and grassland) to pasture and farming influence fire occurrence. Additionally, we explored the joint impact of land-use change and climate extremes in fire activity in terms of estimated vapor pressure deficit (VPD) and maximum cumulative water deficit (MCWD), two common measures of flammability and drought impact. Our results confirm that transition age is a strong predictor of fire probability. They also suggest that fire probability increases (decreases) at different rates before (after) clearing in Amazon and Cerrado. The role of climate extremes in modulating burning activity associated with land-use transitions varied by biome, post-fire land use, and the size of the burned area associated with the conversion. These findings provide insight into incorporating the effect of land-use transition age on ignition probability for fire modelling in combination with climate drivers. From an operational point of view, our results aim to contribute to environmental policies capable of sustaining ecosystem integrity at the ecotone between the Amazon and Cerrado biomes.
EUMETSAT significant contribution to CMEMS
Authors: Obligis Estelle
Published: February 2023

EUMETSAT, the European Organisation for Meteorological Satellites, is expanding its scope beyond supporting meteorology, environment and climate monitoring, to oceanography. To this end, EUMETSAT operates satellites and data processing systems, to provide services which are of high value to ocean monitoring and prediction, especially to the Copernicus Marine Environment Monitoring Service (CMEMS). Key sea and sea ice parameters operated by EUMETSAT secretariat and Ocean and Sea Ice Satellite Application Facilities for different timeliness are either redistributed by CMEMS or used to improve their user services.EUMETSAT's current geostationary and polar Programmes, as well as the European Copernicus Programme of which EUMETSAT is a delegated entity, provide operational observations of the sea and sea ice.The Meteosat geostationnary Programme (MSG and soon MTG) provides sea surface temperature and radiative fluxes from the SEVIRI instrument, and in the future from the FCI and IRS instruments. It is complemented by the polar Programmes EPS, and soon EPS-SG, which provide additional parameters of sea ice, sea surface temperature, sea surface radiative fluxes and wind vectors from AVHRR, ASCAT, IASI and in the future from MetImage, SCA, MWI,IASI-NG.The Jason-CS Programme and the Copernicus Agreement with the EU have entrusted EUMETSAT with operation of the Copernicus Sentinel-3 and Jason-CS/Sentinel-6 satellites, and thus added ocean colour information and further surface topography and surface temperature products.The Copernicus Sentinel-3 mission is today flying in constellation, jointly operated by ESA and EUMETSAT. Each Sentinel-3 satellite carries OLCI, SLSTR and topography payload, providing a wide range of operational products related to ocean topography (and related parameters), sea and sea ice surface temperature and ocean colour.Sentinel-6 is a collaborative Copernicus mission implemented and co-funded by the European Commission, the European Space Agency, EUMETSAT, and the US, through NASA and NOAA.  The two successive Copernicus Sentinel-6 satellites (A and B), launched in November 2020 and to be launched 2025, will fly the same specific non-sun-synchronous low-Earth orbit as the series of European/US TOPEX/Poseidon and Jason satellites to continue the high-precision ocean altimetry mission delivered for more than 30 years.In this presentation, we will present in details EUMETSAT contributions to observations used by CMEMS, the recent innovations in the EUMETSAT stream of marine satellite data, and planned evolutions responding to CMEMS needs for ocean monitoring and prediction.
Diversity of soil biopores and their influence on soil water infiltration under various pedoclimatic conditions
Authors: Védère Charlotte , Aroui Boukbida Hanane , Capowiez Yvan , Cheik Sougueh , Coulouma Guillaume , Pham Dinh Rinh , Grellier Séraphine , Hammecker Claude , Henry des Tureaux Thierry , Harit Ajay , Janeau Jean-Louis , Jouquet Pascal , Maeght Jean-Luc , Rumpel Cornelia , Sammartino Stéphane , Silvera Norbert , Siltecho Siwaporn , Smaili Lotfi , Soulileuth Bounsamay , Bottinelli Nicolas
Published: February 2023

Despite the large contribution of macropores made by soil engineers to the soil macroporosity and water infiltration, few studies have addressed the specific contribution of soil engineer groups, dynamics of biopores and their efficiency in conducting water. Thus, we aimed to investigate the link between soil macrofauna, soil biopores and water infiltration under different pedoclimatic conditions. To do so, we conducted an experimentation in twelve study sites with a large longitudinal gradient from France to Vietnam.  The experiment consisted in the field incubation of repacked soil in cores (15 cm in height and 15 cm in diameter) and controlling the activity of soil engineers in the manner of litter bag. For each site, soil columns were: (i) covered with a mesh (200µm) or not and (ii) with or without addition of organic residues to the soil surface. After 12 months, we measured (i) the 3D organization of biopores by X-ray computed tomography and (ii) the saturated hydraulic conductivity by Beerkan method. In addition, soil macrofauna communities and the 3D organization of biopores was measured in each study field. Addition of organic residues increased up to 2-fold the volume percentage of biopores which reached similar values than those observed for each study field. The co-inertia analysis between the data matrix characterizing the shape of biopores and the data matrix of the macrofauna communities showed no statistically significant correlation. Saturated hydraulic conductivity increased with the presence of biopores by 2 to 50-fold with the lowest increased in soils presenting largest saturated hydraulic conductivity. In conclusion, these results demonstrated that biopores are rapidly regenerated regardless the pedoclimatic conditions while the efficiency of biopores in conducting water is related to soil properties.
Improving the representation of freshwater input to shelf seas in an intermediate-complexity global climate model
Authors: Sieradzan Katie , Schmittner Andreas , Wilmes Sophie-Berenice , Green Mattias , Rippeth Tom
Published: February 2023

Whilst accounting for only 7% of the global ocean surface area, shelf seas are important links between multiple environments (including terrestrial, deep marine, and atmospheric) and modulate the freshwater influx from rivers before it reaches the open ocean. This freshwater acts as a buoyancy forcing, and, together with solar heating and tidal mixing, affects the seasonal stratification of shelf seas. As stratification impacts numerous processes within the shelf seas, such as heat uptake, ocean currents and biogeochemistry which may further be of global importance, it is important that freshwater fluxes are accurately simulated within models. Despite their importance, due to coarse model resolution, shelf seas are generally poorly represented in intermediate-complexity global climate models. Here, we examine the accuracy of shelf sea representation in the intermediate-complexity UVic Earth System Climate Model, with a primary focus on the North Sea. Using observational data, we show that the river basin configuration and freshwater discharge in the control model set up has large errors. As a result, the North Sea receives almost double the expected freshwater discharge on an annual scale, impacting the flushing time, seasonal stratification and biogeochemistry of the region. Through a series of simulations rerouting freshwater through more realistic drainage basins, and removing excess freshwater, we improve simulation results, with variations in freshwater fluxes having a significant impact on shelf sea processes. Our results indicate that the over-freshening of shelf seas may not solely be restricted to the UVic model but may be an issue in other global Earth system models due to their low spatial resolution.
Casting synchrotron light on remagnetized carbonates
Authors: Bellon Ualisson , Ivan Ferreira da Trindade Ricardo , Galante Douglas , Williams Wyn
Published: February 2023

We revisit the discussion on the geological processes able to remagnetize vast extensions of intracratonic basins. The main hypotheses for these processes involve: (1) external warm fluids, (2) hydrocarbon maturation, or (3) burial diagenesis and clay minerals transformation. Here we combine classical rock magnetic properties, with micro-to-nanoscale imaging/chemical analysis performed at the Brazilian Synchrotron Light Facility (SIRIUS). Highly sensitive X-ray fluorescence (XRF) and X-ray Absorption Near Edge Structure (XANES) were performed on a Coherent X-ray Nanoprobe Beamline, scanning microscopic regions on thin sections of remagnetized Neoproterozoic carbonate rocks of the São Francisco Craton. These rocks rarely yield any primary remanent magnetization. Instead, distinct geological formations separated by hundreds of kilometers bear an undistinguishable single-polarity characteristic direction carried by both monoclinic pyrrhotite and magnetite. Unmixing of susceptibility components of distorted magnetic hysteresis (potbellies and wasp-waisted) suggests two coercivity fractions and show a strong paramagnetic contribution that surpasses both ferromagnetic and diamagnetic (from calcite/dolomite) signatures. SEM-EDS analysis reveals iron oxides/sulfides embedded in a clay mineral matrix, while XRF data shows a strong spatial correlation of these nanometric remanence-bearing minerals (500-1000 nm) within regions enriched in potassium. XANES spectra of 1000 to 1200 nm particles indicate either stoichiometric euhedral magnetite, or spherical grains with a core-shell structure with magnetite rimmed by maghemite. The identification of these remanence-bearing phases within the pseudo-single domain (PSD) size range, systematically associated to clay minerals (responsible for the important paramagnetic contribution in magnetic hysteresis), might suggest that clay transformation, namely smectite to illite, is an important phenomenon controlling remagnetization of these carbonates
Negative year-to-year agricultural yield extremes projected to occur more frequently under global warming
Authors: Borchert Leonard , Orlov Anton , Jägermeyer Jonas , Müller Christoph , Sillmann Jana
Published: February 2023

Studies on projected agricultural yields focus on end-of-century scenarios. Simulations from the Global Gridded Crop Model Intercomparison (GGCMI) Project phase 3b show conflicting results for global and regional changes of different crops by the end of the century. Here, we interrogate the same simulations, focusing on year-to-year variations of agricultural yields in the important staple crops maize, rice, soybean and wheat.An ensemble of GGCMI models shows a larger agreement on the variations of crop yields than for the long-term trend. Year-to-year variations of projected crop yields become more pronounced over time, especially so for negative crop yield anomalies. As a result, the frequency of negative global crop yield extremes increases with global warming. We show that these negative yield extremes may occur for individual or multiple crops at the same time, and may originate from individual or multiple regions. North America dominates global maize and soybean yield extremes (57% and 44% of all significant global extremes, respectively), and South East Asia and South Asia are important for rice extremes (24% and 22%, respectively), while regional results are inconclusive for wheat. Multi-crop extremes occur most commonly for the combination of maize and soybean, and are dominated by the North America region. Based on these findings, we show that depending on the region and crop, persistent spring or summer drought, cold or heat can be associated with years of global and regional negative agricultural yield extremes.Our results show how specific climatic boundary conditions can lead to year-to-year extremes in important staple crops, highlighting the potential to anticipate such events in the future.
Multiyear predictability of atmospheric angular momentum and its implications.
Authors: Scaife Adam
Published: February 2023

Initialised climate predictions demonstrate ultra long-range predictability of atmospheric angular momentum, Earth's rotation and length of day. We show how slow, poleward propagating anomalies in the atmospheric angular momentum field allow interannual 'memory', well beyond currently assumed limits of atmospheric predictability. The mechanism involves wave-mean flow interaction between transient eddies and zonal winds in the troposphere and supports the persistence and poleward migration of both positive and negative anomalies. We discuss some of the implications and opportunities this presents for multiyear prediction and show how it leads to new teleconnections that are important for interpreting the observed record of climate variability.
The Influence of Freshwater Input on the Evolution of the 1995 Benguela Niño
Authors: Costa Aroucha Leo , Lübbecke Joke , Körner Mareike , Imbol-Koungue Rodrigue
Published: February 2023

Benguela Niños are events of anomalous Sea Surface Temperature (SST) increase in the Southeastern Tropical Atlantic Ocean. In 1995, the strongest Benguela Niño observed in the satellite era took place. It had a drastic impact on the Angola-Benguela Area (ABA, 8ºS – 20ºS, 8ºE to the coast) ecosystem, including high mortality, poor recruitment, and southward shift of sardine populations, as well as reductions in the number of benthic organisms. Although low Sea Surface Salinity (SSS) values extending as far south as 18ºS have been observed during this event, the role of freshwater input for the SST increase in the 1995 Benguela Niño has not been analyzed yet. In this study, we use satellite data, CTD profiles, and reanalysis products to investigate the impact that freshwater anomalies from anomalously high Congo river discharge (CRD) and precipitation might have had on the evolution of the 1995 Benguela Niño. We find that in the onset phase of the event a freshwater plume from the north was spreading southward towards the Angola-Namibia coastal area, concomitant with signatures of positive Barrier Layer Thickness (BLT) and stratification (N2) anomalies. At the same time, a strong poleward Angola current anomaly was observed. Positive SST anomalies peaked in March when SSS values averaged over the ABA were almost 3 psu lower than normal. Our analysis suggests that the anomalous CRD combined with higher than usual precipitation in November/December 1994 generated a negative SSS plume north of ABA, which was advected into the Angola-Namibia coastal region by the poleward surface current anomaly, increasing ocean stability, and reducing the mixing. A Mixed Layer Heat Budget analysis suggests that both anomalous advection and absence of entrainment contributed to the surface warming while the net surface heat flux provided a damping effect. Thus, the high freshwater input that was advected southwards inhibited the entrainment of cool subsurface waters into the surface mixed layer in the ABA, which contributed to the SST increase in the exceptionally strong 1995 Benguela Niño event.
Objective Tracking of Tropical Cyclones and their Impact on Relevant Wind Fields in the West-Pacific for Construction of Physically Consistent Event Sets
Authors: Zhang Xiaoqi , Leckebusch Gregor C , Ng Kelvin S
Published: February 2023

Tropical cyclone activity usually negatively affects people’s lives in coastal countries, especially in East-Asia including China. In order to reduce the effect, various approaches are utilized to study tropical cyclones. The Murray and Simmonds Cyclone Tracking algorithm, which has been mainly used in tracking extratropical cyclones, is, for the first time, applied to detect and track tropical cyclones in the West-Pacific based on mean sea level pressure data. Since this algorithm only requires one variable field as input, if it would achieve similar performance as other more complex tracking algorithms, this could be a good algorithm to use for construction of large physically consistent tropical cyclone event sets.In the presentation, a preliminary evaluation on the performance of the Murray and Simmonds Cyclone Tracking algorithm on tracking tropical cyclones in West-Pacific, using ERA5 and IBTrACS, will be presented. The sensitivity of the performance of the algorithm on different parameter settings will also be discussed. Furthermore, the added value of combining the Murray and Simmonds Cyclone Tracking algorithm and an impact-based storm tracking algorithm, WiTRACK, from the disaster risk reduction and mitigation perspective will also be demonstrated.
Simulating French hydropower operations in a land surface model
Authors: Baratgin Laure , Polcher Jan , Quirion Philippe , Dumas Patrice
Published: February 2023

Climate change and water management are expected to have significant impacts on river flows. Hydropower production is therefore expected to evolve, while low carbon electricity could become more valuable in the context of the transition towards sustainable societies.Hydrological models have been used to evaluate the potential of hydropower plants based on simulated flows. Some of these studies represent dams and water management. However, dam operation is done independently for each dam or each river basin, without considering the specificities of hydroelectric reservoirs whose operation results from an optimization of the entire power system.We propose and validate a demand-based method to represent hydropower in the routing module of a land surface model at the scale of a national power grid. First, hydropower infrastructures are placed in coherence with the hydrological network and links are built between reservoir and power plants. Then, coordinated dam operation is simulated by distributing the total electric demand to be satisfied by hydropower over the different power plants.The method is developed within the routing scheme of the ORCHIDEE land surface model, so that changes in climate or land use can be considered in future studies.We calibrate and validate the model by simulating hydropower production in France over the period 2012-2018 using SAFRAN climate forcing data and comparing it to available observations of hydropower generation. Several rules for the dispatch of production between the power plants are compared and evaluated.We show that an operating rule based on climatological inflows, reservoir volumes and hydraulic heads can simulate a dispatch of production that enables the model to replicate hourly hydropower plants output throughout the period.
Ambient Stress in Subduction Forearcs Constrained by Numerical Models and Earthquake Static Stress Drop Values
Authors: Bocchini Gian Maria , Dielforder Armin , Kemna Kilian B. , Harrington Rebecca M. , Hampel Andrea , Oncken Onno
Published: February 2023

Stress in active subduction forearcs is controlled primarily by friction along the megathrust and the gravitational force. The competing deviatoric compressive and tensional stresses generated by megathrust friction and gravity, respectively, are of the same order of magnitude and result in very low deviatoric stress in the forearc. The near neutral stress state in subduction forearcs is supported by observations of stress reversal, that is a change from deviatoric compression to deviatoric tension, caused by very small megathrust shear stress drops (<10MPa) after recent large megathrust earthquakes. However, studies that quantify and compare the stress state in subduction forearcs at various stages of the seismic cycle are still limited. Here, we use two-dimensional finite-element force-balance models to quantify and constrain forearc stresses at different locations along the Chilean and Japanese subduction margins that are at different stages of the seismic cycle. The models consider forearc topography, slab geometry, crustal thickness, and water load to quantify the elastic stress in the forearc due to gravity and friction along the megathrust. The models indicate low deviatoric stress values (10s of MPa) in the subduction forearcs, which imply a weak forearc crust in areas of active seismic deformation. We validate the model results by estimating seismic stress drop values of forearc earthquakes from high-quality seismic waveform recordings. We estimate spectral corner frequency using both single-spectrum and spectral-ratio estimates and depth-dependent shear-wave velocity models. Spectral-ratio estimates provide more robust corner-frequency estimates that we employ to validate and interpret the increasing stress drop trend down to depths of ~50-60 km. The slight depth dependency of seismic stress drop values is consistent with depth dependency of deviatoric stress obtained from the finite-element models. Moreover, we find that average seismic stress drop values are systematically lower or similar to maximum deviatoric stress obtained from our models, which is consistent with a partial stress release during earthquakes in the forearc. Our results suggest a relation between seismic stress drop values and ambient stress in subduction forearcs.
Benthic foraminifera from extremely shallow-water habitats of Line Islands
Authors: Trubin Yaroslav , Langer Martin
Published: February 2023

The Line Islands rank among the most isolated in the tropical Pacific, hold a biogeographic key position for the translocation of taxa across the Pacific, and constitute the ultimate stepping stone for the dispersal of species from east to west and vice versa. Because benthic foraminifera have limited dispersal capabilities, these isolated stepping stones are crucial for ecological and biogeographic studies. Mapping large-scale biogeographic patterns is vital for setting conservation priorities by revealing biogeographic variability and enabling the identification of species richness hot- and coldspots. Here we present the first results of a comprehensive survey of modern benthic foraminiferal assemblages from the Line Islands and compare the foraminiferal assemblages to other regions in the Pacific Ocean. We also document the diversity and composition foraminiferal biotas from inhabited and uninhabited islands to assess the impact of anthropogenic activities.The large number of species identified allow us to place the Line Islands into a biogeographic context and to assess the role of these remote islands as a stepping stone for the translocation of species across the Pacific Ocean. Our study provides novel insights into underlying mechanisms that promote species richness patterns in different shallow-water habitats.The sediments analyzed includes material from the inhabited Tabuaeran Island, also known as Fanning and the uninhabited Palmyra Island. The environments of the island comprise a multitude of habitats including coral reef areas, lagoons, and algal covered shallow bays.The foraminiferal associations from coral habitats are dominated large benthic foraminifera (LBF) such as Amphistegina, Sorites, and Peneroplis and low amounts of various miliolids. The preservation of nearshore assemblages revealed predominantly abraded and broken individuals. The assemblages from nearshore beaches and reef flats are composed of miliolids, numerous perforate-hyaline, and variable amounts of diverse LBF. The foraminiferal assemblages from algal covered beaches comprise a suite of diverse smaller miliolids and rare, mainly juvenile forms of Sorites. Our survey provides novel insight into the preservation, habitat-preferences, diversity and biogeography of benthic foraminifera across the tropical Pacific.
Disentangling the drivers of future Antarctic ice loss with a historically-calibrated ice-sheet model
Authors: Coulon Violaine , Klose Ann Kristin , Kittel Christoph , Winkelmann Ricarda , Pattyn Frank
Published: February 2023

Recent observations show that the Antarctic ice sheet is currently losing mass at an accelerating rate in areas subject to high sub-shelf melt rates. The resulting thinning of the floating ice shelves reduces their ability to restrain the ice flowing from the grounded ice sheet towards the ocean, hence raising sea level by increased ice discharge. Despite a relatively good understanding of the drivers of current Antarctic mass changes, projections of the Antarctic ice sheet are associated with large uncertainties, especially under high‐emission scenarios. This uncertainty may notably be explained by unknowns in the long-term impacts of basal melting and changes in surface mass balance. Here, we use an observationally-calibrated ice-sheet model to investigate the future trajectory of the Antarctic ice sheet until the end of the millennium related to uncertainties in the future balance between sub-shelf melting and ice discharge on the one hand, and the changing surface mass balance on the other. Our large ensemble of simulations, forced by a panel of CMIP6 climate models, suggests that the ocean will be the main driver of short-term Antarctic mass loss, triggering ice loss in the West Antarctic ice sheet (WAIS) already during this century. Under high-emission pathways, ice-ocean interactions will result in a complete WAIS collapse, likely completed before the year 2500 CE, as well as significant grounding-line retreat in the East Antarctic ice sheet (EAIS). Under a more sustainable socio-economic scenario, both the EAIS and WAIS may be preserved, though the retreat of Thwaites glacier appears to be already committed under present-day conditions. We show that with a regional near-surface warming higher than +7.5°C, which may occur by the end of this century under unabated emission scenarios, major ice loss is expected as the increase in surface runoff outweighs the increase in snow accumulation, leading to a decrease in the mitigating role of the ice sheet surface mass balance.
ROPEWALK (Rescuing Old data with People's Efforts: Weather and climate Archives from LogbooK records) - a digitization project for three centuries of weather observations on board of Danish ships
Authors: Stendel Martin , Kronegh Adam Jon
Published: February 2023

The project ROPEWALK, funded by the AP Møller Mærsk Fund, is a joint initiative of the Danish National Archive and the Danish Meteorological Institute over the period 2023-2026. The aim of the project is to digitize and transcribe all weather observations in ship journals and logbooks stored in the Danish National Archive.The collection in the archive is remarkable for several reasons. A huge amount of data (more than 750 shelf metres) is stored, beginning as early as the 1680s. With the exception of the Napoleonic wars and the Danish state bankruptcy in 1814, the data is complete. In particular, there were no losses during the Second World War.In the archive, logbooks from Danish ships over large parts of Northern Hemisphere are found. Of particular interest are observations from two regions, the Øresund and Greenland.In connection with the Sound duties which every ship passing the sound or belts had to pay between 1426 and 1857, weather observations were made on board of war ships placed at strategic locations near Copenhagen, Helsingør and Nyborg. These ships had to ensure that no one passed without paying the duties. Probably for practical reasons, weather observations were tabulated as early as the first half of the 18th century. In several cases, observations were conducted every time the ship bell was struck, resulting in 48 observations in the course of one day. The early part of the logbook collection is from the Little Ice Age, and numerous ice observations in the Danish waters have been preserved.The other group of logbooks which are of particular interest are from voyages to the colonies, in particular to (western) Greenland. The Greenlandic Trade Company had a monopoly for commerce with Greenland for nearly 200 years, and foreign ships would not be allowed to call a port. These "Greenland Voyages" were conducted several times per year. In many cases, detailed sea ice observations have been made.The original logbooks are being scanned by the National Archive in highest possible resolution. The scans will then be transcribed by means of machine learning. This is possible, since the political system in Denmark was absolutistic between 1660 and 1848, and logbooks from different periods resemble each other much more than is the case for the nautical heritage in other seafaring nations. Where this is not possible, the data will be transcribed with the help of volunteers. For the oldest logbooks, which are in free text rather than in tabular form, we could locate older transcriptions which are much easier to read tahn the original data, either by machine or manually.All transcribed data will be made publicly available. They can be used for future research or as input for reanalysis projects. We will present first results of our analysis.