bluuebunny/crossref_metadata_2025 huggingface dataset:
The impact of rain on the global ocean carbon uptake
Authors: Parc Laetitia , Bellenger Hugo , Bopp Laurent , Perrot Xavier , Ho David
Published: March 2024

Precipitation alters sea surface physical and biogeochemical properties locally. However, due to its high temporal and spatial variations, it has largely been overlooked in studies assessing global ocean carbon uptake. Air-sea CO2 flux is mainly due to the interfacial exchange of CO2 molecules between the liquid and gaseous phases media. Rain may impact this interfacial air-sea CO2 flux by (i) enhancing the turbulence at the air-sea interface and (ii) diluting the CO2 concentration near the ocean surface. At the same time, rain directly injects into the ocean CO2 absorbed by the raindrops during their fall. This latter component, known as wet deposition, contributes to the CO2 flux into the ocean. This study provides the first comprehensive global estimate of these effects and their combined influence on the global ocean carbon uptake during the period 2008-2018. We use different representations of the ocean surface response to rain and different rain products with different rain rate distributions (ERA5 and IMERG) to quantify the uncertainty of the global impact of rain on CO2 sink. We show that rain increases the global ocean carbon sink by +0.14 to +0.19 PgC yr-1 over 2008-2018, representing an increase of 5 to 7% of the global carbon uptake (2.66 PgC yr-1). Both interfacial flux and wet deposition have comparable orders of magnitude. Rain mainly increases the CO2 sink in the tropics, where strong rain rates and weak winds induce noticeable dilution at the ocean surface, in the storm track regions, and in the Southern ocean.
Pairing mineralogical and multispectral satellite imagery analysis to map the hydrothermal alteration on Hasandağ Volcano (Aksaray, Türkiye)
Authors: Diker Caner , Akkaş Efe , Ulusoy İnan , Şen Erdal
Published: March 2024

The Greater and Lesser Hasandağ summits have both active and extinct fumarole vents, with evident hydrothermal alteration in their vicinity. Active fumaroles were documented on the western summit flanks of the Greater Hasandağ crater, at altitudes between 3000 and 3150 meters. Several hydrothermally altered zones are located inside the double craters of Greater Hasandağ and on the Lesser Hasandağ summit. In order to characterize the both completed and ongoing hydrothermal alteration process, a total of 27 rock samples were gathered from the hydrothermally altered rocks. The mineralogical compositions were examined by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FT-IR) from the selected parts of altered rocks. Presence of common low–grade temperature (0 – 100 °C) secondary mineralization such as alunite, natro-alunite, halloysite, and opal-AN with scarce jarosite indicate existence of a continuous alteration process in a systematic order of crystallization. Recurrent temperature measurements from the fumarole vents also confirm the mineralogical findings. FT-IR analysis is also used synchronously to identify the spectral characteristics of hydrothermally altered rocks together with other analytical methods. Spatial distributions of the alteration minerals of Hasandağ were monitored comprehensively by using ASTER and Sentinel-2 imagery, relying on the reflectance and absorbance characteristics observed in the FT-IR data obtained from the altered samples. The combined results allowed us to produce precise hydrothermal alteration maps. Significantly, the zones where the alteration is prevalent are located along the Karacaören and Hasandağ Faults, which extend in the northeast-southwest and northwest-southeast directions, respectively.
Feasibility study to estimate the ion velocity field in the F region from EISCAT_3D radar observations
Authors: Fukizawa Mizuki , Ogawa Yasunobu , Nishimura Koji , Ueno Genta , Nishiyama Takanori , Hashimoto Taishi , Tsuda Takuo
Published: March 2024

We conducted a feasibility study to estimate the horizontal ion velocity field in the ionospheric F region from ion velocities observed by the EISCAT_3D radar. We assumed a 27-beam configuration with a minimum elevation angle of 30 degrees. The ion velocity observation data from 200 km to 500 km altitude were projected to 200 km altitude, assuming ions above 200 km altitude follow the E x B drift. Then, we reconstructed ion velocity vectors for ±250 km in the east-west direction and ±500 km in the north-south direction at 200 km altitude. The resolution in north-south and east-west directions was 25 km. The reconstruction was conducted by maximizing a posterior probability based on Bayes’ theorem. The constraints were set to minimize the L2 norms of the following four vectors in the horizontal plane: (1) the first and (2) the second derivative of three components of the ion velocity vector, (3) the divergence of the ion velocity perpendicular to the magnetic field lines, and (4) the ion velocity parallel to the magnetic field lines. We investigated which combination of the four constraints would reconstruct the shear flow field most correctly and found that the best combination was (2), (3), and (4).
Concept to quantify the effects of SOM on water retention hysteresis and hydrophobicity in sandy soils and their implication for soil water modeling
Authors: Schwarze Daniel , Metzger Johanna , Spieckermann Mathias , Becker Joscha , Herion Yva , Göbel Marc-Oliver , Bachmann Jörg , Eschenbach Annette
Published: March 2024

Global warming is promoting extreme weather conditions like more frequent heavy rainfall events and longer periods of drought in central Europe. This can lead to an increase in hydrophobicity and hysteretic behavior of soils, potentially reducing its water retention capabilities and changing the soil water balance. These soil characteristics are also highly dependent on the amount and properties of soil organic matter (SOM). Climate change effects are expected to be particularly pronounced in sandy soils, which have comparatively low water retention capacities.In this study, we will quantify the effects of SOM on soil hydraulic properties and analyze their impact on the soil water balance in hydrological models in comparison to data acquired by pedotransfer functions.To cover a wide range of SOM content and properties, we sampled sandy soils (> 80% sand) from five different land use categories (arable land, heathland, grassland, deciduous and coniferous forest). The samples were taken in the Southwest of the Metropolitan region of Hamburg, near Lüchow-Dannenberg. The samples were analyzed for their total soil organic carbon and nitrogen content, and will further be analyzed for their fractions of particulate organic matter (POM) and mineral associated organic matter (MAOM). Hydrophobicity was determined using the water-drop-penetration-time test and contact angle measurements with the sessile drop method. Furthermore, the Integrative Repellency Dynamic Index (IRDI) will be determined for all topsoils to quantify the average hydrophobicity of the sample. Soil water retention is acquired using the porous plate method as well as the evaporation method (HYPROP), including wetting and drying curves. This data will serve as a starting point for simulations under different climate scenarios using HYDRUS.The aim of this study is to improve our understanding on how hydrophobicity and water retention (wetting and drying) in sandy soils are influenced by the content and properties of SOM, and how this affects the results of hydrological models under different climate scenarios. This will contribute to improve the ability to assess future soil water dynamics, which is vital for sustainable land use and climate change adaptation. The study is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany‘s Excellence Strategy – EXC 2037 'CLICCS - Climate, Climatic Change, and Society' – Project Number: 390683824, contribution to the Center for Earth System Research and Sustainability (CEN) of Universität Hamburg".
August 2023 Slovenian flood anatomy from national seismometer network data analysis
Authors: Dietze Michael , Jemec Auflič Mateja , Petan Sašo , Bezak Nejc
Published: March 2024

Excessive and sustained rainfall can trigger regional floods with a large propagation range. Their non-linear onset, rapid evolution and massive impact make prediction, mitigation and posteriour anatomy efforts difficult.The atmospheric low “Petar” that struck Europe in early August 2023 was one drastic example of such flood triggering rain events. It was able to gain abundant moisture and heat over an exceptionally warm Mediterranean Sea, before it moved to continental Europe, crossing Slovenia, Austria, and Germany. It caused severe flooding as a result of locally more than 350 mm rain within less than two days. We focus on Slovenian examples, where the event was perceived the most devastating natural hazard in the last decades.Here, we follow a seismic approach to study the spatially contrasting effects of the rain signal from available FDSN data (SL network). We study the time variant spectral signatures of reaches in steep mountain, graded upland and wide basin landscapes across northern Slovenia and exemplarily invert the seismic data for key flood parameters: water level and debris flux, and propagation velocity. We discuss the detection range of existing earthquake seismometer networks and the potential to improve those with respect to flood quantification. Our analysis highlights the compound effects of channel geometry, event magnitude and network density for flood detection and signature consistency.
Ecosystem-scale floodplain forest methane exchange
Authors: Kowalska Natalia , Jocher Georg , Bednařík Adam , Warlo Hannes , Soosaar Kaido , Macháčová Katerina
Published: March 2024

Floodplain forests play an important role in the exchange of methane (CH4) with the atmosphere. However, due to climate change and anthropogenic activities, main factors driving this exchange, such as ground water table and soil temperature, are constantly changing. The studied floodplain forest in Lanžhot, Czech Republic, represents nowadays relatively dry conditions.The main aims of our study were to quantify the CH4 emission on the floodplain forest ecosystem level using the eddy covariance (EC) method, with special emphasis on environmental conditions, turbulence development and footprint, as well as to probe all potential CH4 sinks and sources within the studied ecosystem for arriving at a complete CH4budget. The ecosystem-scale CH4 fluxes were analysed with regards to the CH4 emissions of water bodies within the EC footprint. CH4 fluxes from a stream located within the footprint of the EC tower were measured using floating chambers and bubble traps. Studies were complemented by the analysis of the contribution of trees to the CH4 exchange. For this purpose, stem chambers measured CH4 fluxes on hornbeam trees, one of the main tree species at the study site and in Central Europe. Additionally, CH4 fluxes from the soil were included in the analysis to capture all potential CH4 sources and sinks within the studied ecosystem.We initially hypothesized that ecosystem-scale CH4 exchange will be negligible. Our resultsshowed, however, that the whole ecosystem is a small but constant CH4 source as we observed an average emission flux of 11.7 mg CH4 m-2day-1 over the period June to December 2021. In addition, we observed variability of the CH4 fluxes in relation to the wind direction and to u*(friction velocity, indicator for turbulence development). Further analysis shall answer on the question if more water bodies within a particular wind sectors means higher fluxes above the canopy and if higher turbulence is correlated with higher CH4 fluxes above canopy as hotspot emissions are better mixed up. The probed stream was a substantial source of CH4 with averageCH4 fluxes of 260 ± 107 mg CH4 m-2 day-1, respectively, over the period from April to December 2021. Ebullition was the dominant pathway of CH4 release throughout the whole monitored time period. Results from the stem and soil CH4 flux measurements identified hornbeam stems and soil as net sinks for CH4 (-0.025 and -0.999 mg CH4 m-2day-1, respectively). Finally, after putting all pieces together we will arrive at a holistic view of CH4dynamics within the studied floodplain forest ecosystem with the potential of transfer of knowledge to ecosystem of similar kind elsewhere.
Future Changes in European windstorm loss and seasonal loss clustering in the EURO-CORDEX dataset
Authors: Alifdini Inovasita , Moemken Julia , Ramos Alexandre M. , Stankovic Aleksa , Caballero Rodrigo , Pinto Joaquim G.
Published: March 2024

European windstorms are among most important natural hazards for insurance companies. Quantifying with the impact of windstorms becomes more challenging due to seasonal loss clustering, characterized by numerous intense windstorms in a season, leading to exceptionally high seasonal losses. Climate change introduces another level of uncertainty regarding potential losses from European windstorm events.The EURO-CORDEX dataset is designed to enhance the representation of regional and local weather conditions consists of a set of high-resolution climate simulations at 12.5 km resolution.  In this context, this will allow the assessment of the impact of windstorms for recent and future climates in a finer resolution. To achieve this, we use daily maximum surface wind gusts of 20 global-to-regional climate model chains from EURO-CORDEX (EUR-11 domain). The investigation focuses on the extended winter season (ONDJFM) between the historical period (1976-2005) and future projections under global warming level (GWL) scenarios of +2°C and +3°C, following the Representative Concentration Pathway 8.5 (2006-2100).The evaluation of windstorm impact is carried out using the Loss Index (LI) method, focusing on the country level. For the historical period, a substantial bias is observed in the 98th percentile of daily maximum wind gusts between EURO-CORDEX and ERA5. This bias is corrected through empirical quantile mapping, resulting in corrected models that show reduced biases in wind gust extremes while maintaining consistency with the climate change signal.Under the +2°C and +3°C GWLs, the majority of models indicates a reduction in the magnitude and frequency of extreme windstorms over Western Europe and the Iberian Peninsula, leading to decreased European windstorm loss, while an increase over Eastern Europe is expected, contributing to higher loss. In the majority of countries, the occurrence of seasonal loss clustering is expected to decrease under GWL conditions compared to the current climate.Our study provides valuable insights for insurance companies and policymakers to deal with the uncertainty of the loss of windstorm under future climate conditions.
A Machine Learning application towards a better representation of Madrid’s urban climate
Authors: Bushenkova Angelina , M.M. Soares Pedro , Johannsen Frederico , C.A. Lima Daniela
Published: March 2024

Cities are considered local “hotspots” of climate change. Urban areas concentrate a large fraction of global population, wealth, and emissions, exposing their inhabitants to climate change impacts. Therefore, the improvement of urban present climate description and future projections are paramount for designing adaptation and mitigation strategies. Global Climate Models are state-of-the-art tools for projecting future climate. However, most of the simulations have coarse resolutions and do not have physical urban parametrisations to adequately represent the physical properties and processes at the urban scale.
The advantage of applying a machine learning approach –  Extreme Gradient Boosting (XGBoost) – is explored for better describing Madrid’s urban climate. Namely, the ability to reproduce present and future climates: 2-m air temperature (Tmax, Tmin); surface temperature (LST); urban heat island (UHI) and surface urban heat island (SUHI) effects. XGBoost is evaluated at monthly and daily scales for local ground temperatures and, also at hourly scale, to represent the spatial structure of land surface temperature w.r.t. remote sensing data. Firstly, for present climate, XGBoost is trained with a set of ERA5 predictors (0.25º), ground stations, and Land Surface Temperature observations. Secondly, a number of sensitivity cases are performed to assess the results dependency to predictors and their resolution. Thirdly, the learned relationships between the set of predictors and predictands is applied to Earth System Global Climate Models (ESGCM) predictors, providing historical and future climate projections for the 21st century under four emission scenarios.
Overall, XGBoost results reveal a good performance and significant added value against ERA5 and the ESGCM. XGBoost greatly improves the reproduction of the present climate Tmax, Tmin, LST, and more importantly, the UHI (-0.5ºC and +3ºC for Tmax and Tmin), and the SUHI (+1ºC and +2ºC for Tmax and Tmin). For future climate, XGBoost significantly corrects the ESGCM UHI misrepresentation but seems to underestimate the expected Madrid’s local warming (3.5ºC anomaly).
This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020-IDL. Angelina Bushenkova was supported by a grant through the project “ELABORAÇÃO DA ESTRATÉGIA REGIONAL DE ADAPTAÇÃO ÀS ALTERAÇÕES CLIMÁTICAS DO ALENTEJO – ERAACA”.Frederico Johannsen was supported by FCT with the doctoral grant UI/BD/151498/2021. Daniela C.A. Lima was supported by the Scientific Employment Stimulus 5th edition from Fundação para a Ciência e a Tecnologia (FCT, 2022.03183.CEECIND).
Study on the difference of rice-wheat rotation system greenhouse gas estimation by different simulation methods
Authors: Yuming Yang
Published: March 2024

Global warming, mainly caused by greenhouse gas (GHG) emissions, is one of the major concerns of the current society. Accurate estimation of GHG emissions in various fields can help governments and international organizations to formulate emission reduction strategies.The main objectives of this study were to estimate CH4 and N2O emissions from rice-wheat crop fields using IPCC2006 Tier2 approach and DNDC model, and to compare the performance of the two methods; and to evaluate the accuracy of GHG emissions of the DNDC model with rotational and non-rotational simulation scenarios. In this study, we conducted a rice-wheat rotational field experiment from 2015 to 2018 to determine CH4 and N2O fluxes periodically using static chamber-gas chromatography measurement and analysis system. On this basis, combined with field management and meteorological data, we simulated GHG emissions from rotational and non-rotational crop scenarios using the IPCC2006 Tier2 approach and the DNDC model. The results show that (1) the DNDC model can simulate the time series of paddy CH4 and N2O emission fluxes and winter wheat N2O emission fluxes with estimation errors of -4.8%, -11.6%, and -10.8%, respectively, and the modeling accuracy is better than that of the IPCC2006 Tier2 approach; (2) the accuracy of the DNDC model for simulating the GWP under the rotational cropping scenarios was higher than that of the IPCC2006 Tier2 approach, the relative errors of GWP simulation in the DNDC model were -5.9% and -21.7% for rice and wheat fields, respectively; (3) the relative errors of winter wheat cumulative CH4 emissions in the rotational cropping scenario in the DNDC model were higher than those in the non-rotational cropping scenario, and the relative errors of cumulative emissions of other GHGs in the rotational cropping scenario were lower than those in the non-rotational cropping scenario.This study provides some references for estimating regional agricultural GHG emissions and formulating emission reduction targets and policies.Keywords: Rice-wheat rotation; DNDC; IPCC2006 Tier2; Greenhouse gases
Statistical Properties of Long-Period Plasmapause SurfaceWaves From Van Allen Probes Observations
Authors: Feng Zi-Jian , Ren Jie , Zong Qiu-Gang , Xiang Ting-Yan , Ai Xin-Yu
Published: March 2024

Recent work revealed the existence of plasmapause surface waves (PSWs) with Van Allen Probes observations, which are characterized by the periodic modulations of both magnetic/electric fields and plasma densities, and suggested to be the driver of giant undulations (GUs). In this study, six years data from Van Allen Probes were used to investigate the spatial distributions and occurrence conditions of PSWs in the period of 5–30 min. PSWs are found to be mainly distributed at L = 3.5–7 and their occurrence rate is increasing with larger L shells. In the azimuth direction, the spatial distribution of PSWs exhibits an obvious dawn-dusk asymmetry with highest occurrence rates at MLT = 15–21, which is consistent with the spatial distribution of GUs revealed in the previous study. This further demonstrates that PSWs and GUs are connected, and indicates that PSWs differ from Ps6 waves which have a similar wave period and irregular waveform but mainly concentrate in the dawnside and connect with Ω bands. PSWs preferentially occur under the condition of high solar wind velocities (VSW > 500 km/s) and high dynamic pressures (Pdyn > 5 nPa), and their occurrence rate has a negative correlation with IMF Bz, SYMH and AL. Statistical results also reveal that PSWs preferentially occur around the peak of both magnetic storms and substorms. These findings may shed new lights on the further understanding of PSWs' generation and propagation.
Impact Analysis of Series of Groundsills on the Fluvial Stability and Geomorpholog
Authors: Lin Pohsuan , Hsieh Tsungyu , Liao Kuowei , Wei Kailun , Lin Guanyu
Published: March 2024

To mitigate riverbed erosion both longitudinally and transversely, control water flow, and stabilize riverbanks, the use of groundsills has become a widely adopted engineering method. For large conservation areas, using a series of groundsills is standard practice. However, the sediment transport in rivers is a dynamic process, and the implementation of series groundsills can cause discontinuities in the longitudinal corridor of the river, leading to damage to the ecological environment and landscape. Although there is considerable consensus on various aspects of series of groundsills, current research primarily focuses on the influence of the configuration of groundsills (such as height and width) on sediment downstream. Therefore, this project aims to estimate the trends in sediment transport through scaled experiments and numerical simulations. Results shown that according to the analysis results, neither the Q5 nor Q95 criteria are met in the proposed plan for the complete removal of the groundsills. This project believes that the complete removal of the groundsills may have a drastic impact on the environment, potentially leading to unstable conditions, and thus requires careful evaluation. The design of openings in the groundsills is an effective ecological adjustment project. Regarding the design of the opening height, this project suggests considering two factors: one is to reduce the similar damming effect caused by lowering the elevation, and the other is the gathering of water flow. It is a trade-off between these two factors. Increasing the depth of the opening may benefit the ecology but could lead to unintended erosion due to concentrated water flow, and vice versa.According to the analysis results, neither the Q5 nor Q95 criteria are met in the proposed plan for the complete removal of the fixed-bed structure. This project believes that the complete removal of the fixed-bed structure may have a drastic impact on the environment, potentially leading to unstable conditions, and thus requires careful evaluation. The design of openings in the fixed-bed structure is an effective ecological adjustment project. Regarding the design of the opening height, this project suggests considering two factors: one is to reduce the similar damming effect caused by lowering the elevation, and the other is the gathering of water flow. It is a trade-off between these two factors. Increasing the depth of the opening may benefit the ecology but could lead to unintended erosion due to concentrated water flow, and vice versa. he proposed plans can optimize benefits for both upstream and downstream water conservation, and protect downstream objectives by managing sediment transport.Keywords: series groundsill, ecology, sustainable management, sediment transport
Coseismic gravity changes of the 2008 Wenchuan earthquake in China observed by surface gravimetric data
Authors: Hao Hongtao , Hu Minzhang
Published: March 2024

Coseismic gravity changes provide significant information for the study of the mechanisms of large earthquakes and for developing fault models (Sun, 2012). In this research,  coseismic gravity changes of the 2008 Ms8.0 Wenchuan earthquake in China were studied by using gravity observation data and simulation based on a fault model.Firstly, a fine processing of relative and absolute gravity data from the Longmenshan Gravimetric Network was carried out and observed gravity change of 22 stations near this earthquake were obtained; Secondly ,simulation of coseismic gravity changes was conducted based on half-space dislocation theory using the fault model obtained by Wang et al(2008) through inversion with multiple types of geodetic survey data, including GPS, INSAR, and leveling, and the results were compared with the observations..It was found that the observed and simulated results are basically consistent, showing that the significant changes are mainly concentrated in the near-rupture zone in the hanging wall of the Yingxiu–Beichuan fault and that the changes decrease rapidly away from the rupture zone. The changes exhibit a positive to negative trend from east to west in the footwall of the Yingxiu–Beichuan fault and have a distribution characterized by alternate positive and negative changes in the hanging wall of the fault. This demonstrates the reliability of the observed results and the reasonableness of the fault model used in this paper.In the near-rupture zone on the west and east sides of the Yingxiu–Beichuan fault, there are still some differences between the observed and simulated results. The trends in the spatial distribution of these differences exhibit a deviation similar to “phase delay”; in other words, an observed result deviates from the corresponding simulated result in terms of spatial position, which is speculated to be caused by errors in the geometric parameters and in the slip distribution of the fault model. After the slip distribution of  the Pengguan fault model was modified based on the actual surface rupture distribution, the simulated result at the Hongjiawan station near the eastern boundary of the fault model showed greater consistency with the observed result. This indicates that the observed gravity change results in this paper can provide an important reference for further detailed study of the fault model.                     Fig1.Schematic of the Chengdu Gravimetric Network                        Fig2.Spatial distribution of observed gravity changes and simulated results  
Quality analysis of the low-cost GNSS receiver pseudorange data.
Authors: Sieradzki Rafal , Paziewski Jacek , Stepniak Katarzyna , Banach Jakub
Published: March 2024

The last decade has brought us rapid developments in low-cost GNSS receiver technology. The performance level of such receivers can be unexpectedly close to that offered by high-grade geodetic ones. Nevertheless, the further growth of applicability for these types of devices still needs a more detailed analysis of observations.Motivated by such developments, we focused on the quality of multi-GNSS pseudorange data acquired by three low-cost receivers: u-blox ZED-F9P, Septentrio Mosaic-X5, and Skytraq PX1122R and its comparison with reference values adopted from the geodetic receiver - Trimble Alloy. We investigated two main characteristics of code data – observation noise and correlation in the time domain. In contrast to a typical pseudorange data analysis based on a single-receiver scenario performed with multipath combinations, we extended our tests with data acquired at zero-baseline formed of homogeneous receiver pairs. Such an approach allowed us to analyze the quality of more realistic data, i.e., affected by multipath, and data with multipath removed through between-receiver differencing.The investigations revealed significant discrepancies in data quality between selected low-cost receivers and recorded signals. Generally, the pseudorange noise was the lowest for Septentrio Mosaic-X5, whereas the noisiest observations were found for Skytraq PX1122R. More interestingly, considering the deviation of code data, Septentrio Mosaic-X5 outperformed the geodetic receiver. On the other, we noted that the low-cost receivers' measurements are noticeably correlated in the time domain, even for between-receiver differences of multipath combinations. 
Orbital-scale competition of biogenic carbonate and opal production at the Del Caño Rise in the Indian sector of the Southern Ocean during the late Pleistocene 
Authors: Choi Hyuk , Civel-Mazens Matthieu , Crosta Xavier , Billy Isabelle , Irino Tomohisa , Takata Hiroyuki , Ha Sangbeom , Khim Boo-keun
Published: March 2024

The Southern Ocean is characterized by various ocean fronts that separate surface waters with different hydrographic properties. Ocean fronts’ position changed over glacial-interglacial cycles, which, consequently, affected surface water properties and productivity through time at any given location. The present study reconstructs changes in biogenic carbonate and opal burial at Del Caño Rise (DCR), Indian Ocean sector of the Southern Ocean, over the last three climate cycles. Based on Accelerator Mass Spectrometry radiocarbon dating of planktonic foraminifera as well as comparison of oxygen isotopes of planktonic foraminifera with LR04 stack, the studied core MD19-3575CQ, located today in the Subantarctic Zone, covers the last ~250,000 years. Biogenic carbonate content shows consistent low values during all glacial periods (average 32.4%) and high values during all interglacial periods (average 61.5%). In contrast, biogenic opal content increased during all glacial periods (average 12.8%), compared to interglacial periods (average 8.5%). TOC exhibited a similar pattern to the biogenic opal content, with higher values during glacial periods (average 0.38%) and lower values during interglacial periods (average 0.17%). The increased biogenic opal content during glacial periods is attributed to enhanced silica supply to surface waters due to northward migration of the Subantarctic Front, possibly shifting north of DCR during these periods. However, the relatively low biogenic opal content in the study area compared to other regions of the Polar Frontal Zone (average 55.6%) suggests insufficient silica supply to support high diatom production. The reduction in biogenic carbonate content during glacial periods is related to the decrease in coccolithophore productivity due to low ocean temperatures (~2ºC) and the competition for nutrients and light with diatoms. Despite the shallow water depth (~2400 m) at the core location, the weakened Atlantic Meridional Overturning Circulation and thickening of the corrosive Southern Ocean bottom waters during glacial times may have increased carbonate dissolution. Our study emphasizes that changes in surface water properties by ocean front’s migration impact on regional productivity, which may influence global biogeochemical  cycles.
Internal tide generation from linear theory: Supercritical slopes, directionality, and ocean mixing implications
Authors: Pollmann Friederike , Nycander Jonas , Geoffroy Gaspard , Eden Carsten , Olbers Dirk
Published: March 2024

The main forcing of the ocean’s internal gravity wave field is the interaction of the barotropic tide with the rough seafloor. This process is inherently anisotropic: the orientation of the topographic obstacles and the direction of the tidal currents determine the amount and direction of the generated internal wave of tidal frequency, the internal tide. Available global estimates of the internal tide generation, however, do not take this directionality into account. We present estimates of the global M2-tide generation into the first 10 vertical normal modes using a new method based on linear theory that resolves both magnitude and direction. Linear theory breaks down once the slope of the topographic obstacle exceeds that of the generated tidal beam. We discuss the role of such supercritical slopes at continental shelves and in the open ocean. Finally, we will use the anisotropic M2-tide generation as forcing of the internal wave model IDEMIX, the backbone of an energetically consistent parameterization of wave-induced turbulent mixing for ocean general circulation models. Both wave energy levels and turbulent kinetic energy dissipation differ substantially compared to the reference scenario with the previously used isotropic tidal forcing. This underlines the importance of resolving the directionality of the internal tide generation in parameterizations of wave-induced turbulent mixing.
Abundance of Organic and Inorganic Nitrogen in Marine Aerosols over the China Seas and the Pacific Ocean from Cruises to the Arctic and the Antarctic
Authors: Yu Xu , Yu Jian Zhen , Zhou Yang , Shi Guitao , Lai Senchao
Published: March 2024

Aerosol-bound nitrogen (N) serves as a significant external source of N nutrients for marine ecosystems. However, the measurement of aerosol N in the marine atmosphere is challenging due to difficulties in field sample collection. Specifically, the assessment of organic nitrogen (ON) abundance in marine aerosols remains largely unexplored. In this study, marine aerosols were collected from various regions, including the China Seas (Region 1), the Northwest Pacific to Southern Arctic Ocean (Region 2), and the Southwest Pacific to Antarctic (Region 3). A newly developed method enabling the simultaneous detection of inorganic N (IN) and ON in filter-based aerosol samples has been employed to determine the total quantities of IN and ON. Additionally, the concentrations of organic and elemental carbon (OC/EC) and major ions were measured.Over the China Seas, the average aerosol IN and ON levels exhibited the following rank: Bohai & Yellow Sea (3.87 and 0.61 μg N m-3) > East China Sea (1.50 and 0.27 μg N m-3) > South China Sea (0.52 and 0.18 μg N m-3). However, the average ratio of ON to total N (ON/TN) was higher in the South China Sea (27.1%) compared to the Bohai & Yellow Sea (16.1%) and East China Sea (16.0%). Notably, aerosol IN and ON showed a strong correlation with EC over the China Seas, particularly in the Bohai & Yellow Sea and East China Sea, indicating significant contributions of anthropogenic emissions to the marine aerosol N pool. In comparison, much lower aerosol N levels were observed in Region 2 and 3, with average IN concentrations of 0.064 and 0.021 μg N m-3, and average ON concentrations of 0.049 and 0.024 μg N m-3, respectively. On average, ON accounted for approximately half of the aerosol N in clean marine atmospheres, as observed in Region 2 and 3. Furthermore, the positive correlation between aerosol IN and ON with non-sea salt potassium (nss-K+) was observed in Region 2, but not in Region 3, suggesting a more prominent contribution of biomass burning emissions to marine aerosol N in the northern hemisphere compared to the southern hemisphere. Interestingly, aerosol ON exhibited a stronger correlation with secondary species such as nitrate (NO3-) and non-sea salt sulfate (nss-SO42-) than with sodium (Na+) in both Region 2 and 3, indicating that secondary formation might play a dominant role in contributing to marine aerosol ON, surpassing primary sea salt emissions. Future research efforts should focus on molecular characterizations to gain a better understanding of the sources and transformations of marine ON aerosols.
Replacement of meteorological towers with ground-based remote-remote sensing sodars: How close are we? 
Authors: Dellwik Ebba , Rodén Sten-Ove , Arnqvist Johan , Sjöholm Mikael , Möhrlen Corinna , Gräsman Andre
Published: March 2024

As wind turbines have grown in size, it has become ever more costly to make the necessary tower-based wind observations needed both for the pre-operation (siting) phase and for wind turbine operations. In response to this challenge, the wind energy scientific community has - over the last decades - focused on evaluating and improving ground-based remote-sensing technology. The development has often been done in close collaboration with the innovative companies dedicated to providing the new solutions for replacing the expensive meteorological towers to the market. The project EARS4WindEnergy, which started in March 2023, represents one such effort. The project is focused on a re-exploration of the sodar technology, which preceded the later focus on wind lidars. Here, we present a benchmarking of the AQ510 sodar equipped with new signal processing technology with tall-tower data focusing on the three “must-perform” criteria of accurate wind speed, accurate turbulence intensity and a reliable identification of erroneous data. The complementary aspects of data availability and robustness in relation to current wind lidars is also discussed. Most of the presented data are taken at the Østerild test site in Northern Denmark, where a 244m tall tower allows for accuracy quantification over most of the sodar’s measurement range.
Effects of Runoff Changes on the Climate Simulations of the Middle Miocene Climate Optimum
Authors: Wei Jilin
Published: March 2024

Maintaining global freshwater conservation in climate models is crucial for accurately simulating Earth's hydrological cycle. This property particularly deserves specific attention in the deep-time paleoclimate simulations for the different geographies that changes the river route to the ocean. Changes in the volume of runoff directly exert significant impact on the ocean circulation. Large uncertainties in paleo-topography causes the uncertainties in runoff, but the latter receives less attention in the model simulations. To investigate the effects of the uncertainties on the model simulations, climate simulations of the Pre-Industrial (PI) and the Middle Miocene Climatic Optimum (MMCO) are compared by two sets of experiments —— freshwater conservative and non-conservative experiments that with sufficient and insufficient runoff import to the ocean model, respectively. Responses of the differences between the MMCO and the PI to the runoff changes are investigated. For the mean state, large qualitive and quantitative differences appear in the North Atlantic. Compared to the non-conservative experiments, the conservative experiments show the reduced salinity in the North Atlantic and collapsed Atlantic Meridional Overturning Circulation (AMOC), in contrast to the high salinity distribution and much strong AMOC in the non-conservative experiments. These differences lead to the discrepancies in volume transport through the oceanic seaway, as well as contribute to the temperature, sea ice and surface albedo changes in different amplitude in the North Atlantic. Although the climatic variabilities are affected by the runoff changes, enhanced Atlantic Multidecadal Oscillation (AMO) and reduced El Niño–Southern Oscillation (ENSO) are simulated in the MMCO regardless of the quality of freshwater conservation. Besides, the MMCO simulations show that the intensity of the Asian monsoon is greater in the South Asia and lower in the East Asia compared to PI. The study suggests that runoff changes have great effect on the climate change in the North Atlantic and need extra attention in the paleoclimate study.
The Integrated Greenhouse gas Monitoring System (ITMS) for Germany: Update on recent progress
Authors: Gerbig Christoph , Kaiser-Weiss Andrea , Bovensmann Heinrich , Kiese Ralf , Scheer Clemens , Akinyede Rachael , Ellerhoff Beatrice , Reuter Maximilian , Imhof Hannes , Plaß-Dülmer Christian , Fix Andreas
Published: March 2024

The Integrated Greenhouse Gas Monitoring System for Germany (ITMS) is a national initiative to establish an operational service for the provision of independent estimates of GHG fluxes for Germany. The main aim is to enhance transparency in reporting of emissions and natural fluxes on the path to net zero emissions. ITMS is a highly interdisciplinary project, bringing together diverse scientific communities involved in atmospheric observations, satellite observations, biosphere and agriculture research, inventory experts, and atmospheric transport and inverse modelling. ITMS utilizes observational datastreams from research infrastructures such as ICOS and IAGOS, and tailored remote sensing products, to constrain Germany’s GHG fluxes into the atmosphere using inverse atmospheric transport modelling. Detailed a priori emissions are generated consistent with UNFCCC reported emissions, while priors for natural fluxes are based on various process based as well as diagnostic models. Inverse modelling is deployed at mesoscale resolution, using the CarboScope-Regional (CSR) inversion system operated at the MPI-BGC as a back-bone and reference system, while developing ICON-ART based data assimilation for future operational services. The presentation will give an overview of recent progress and show some research highlights achieved so far.
Optimization of Data from Local Groundwater Head Monitoring Network Using Principal Component Analysis
Authors: Raza Ahsan , Baatz Roland , Inforsato Leonardo , Nendel Claas
Published: March 2024

Ascending near-surface groundwater is an important source of water supply to crops and grasslands. Tapping this sub-surface water source, they exhibit a more stable productivity over time as compared to groundwater-distant sites. Assessing crop and grass productivity at high resolution with the help of simulation models therefore requires groundwater table distance information in an apposite spatial and temporal resolution. Groundwater level monitoring networks offer point-based data with variable observation frequency and data quality, impairing assessments of local variations in the hydrographs at each observation well. We propose an efficient and structured process for applying principal component analysis (PCA) in optimizing the groundwater level monitoring network. The PCA functions were used to determine the relative contributions of individual observation wells in determining the spatio-temporal variations in hydrographs. For each well, the Principal Components (PCs) derived from the PCA were used as predicted variables to draw reference hydrographs that describe the expected normal behavior of individual observation wells. This reference hydrograph was then compared with the observed hydrograph so that the residuals describe the local deviations from the normal behavior of the observation well. Deriving a time series of the residuals facilitates a rapid screening for idiosyncrasies unique to each well. Based on a ranking of all wells in the network according to their degree of deviation from the reference, we discarded irrelevant monitoring wells and time series. In a case study using 1300 observation wells in Brandenburg State, Germany, with mean monthly data from 2000 to 2022, we showed in preliminary results that the overall difference in groundwater level between the original observation well network and the optimized network developed with PCs is less than 5%, while the total number of observation wells in the network is reduced by 10%, which will save the time and cost to monitor groundwater levels in the area.
Long-term atmospheric radon measurements and their connection with environmental conditions
Authors: Baumann Sebastian , Gruber Valeria , Gräser Joachim , Roth Dietmar
Published: March 2024

Radon is a radioactive noble gas. Accumulated indoors it is a large source of radiation exposure. Atmospheric radon can be used as a tracer for greenhouse gases and for atmospheric modelling.We analyzed long-term (> 10 years) time series of atmospheric radon (Rn-222 and Rn-220) at 15 locations in Austria and neighboring countries. The measured concentrations are equilibrium-equivalent concentrations (EEC), where decay products of radon are measured on air filters with a PIPS-detector. Other parameters as ambient dose rate and weather data (wind, rainfall and precipitation) are measured at the same location. Additional for one year the atmospheric radon concentration was measured directly with a different measurement system (Alphaguard) at three locations.The analysis of the EEC showed that the temporal variation of atmospheric radon (Rn-222, Rn-220) depends on meteorological parameters. Seasonal and diurnal variations are linked to the stability of atmospheric layers. Under stable weather conditions higher radon concentrations occur. Correlation of the radon concentrations were found primarily with temperature and wind speed. At temperatures below 0 °C, Rn-220 shows very low concentrations and a different behavior than Rn-222. This reduction of Rn-220 availability could be associated with frozen or snow-covered soils.The additional measurements (Alphaguard) of atmospheric radon concentrations provided plausible long-term averages, although individual measurements can provide implausible values (e.g. negative values). The temporal patterns of the two measurement systems are very similar, and the atmospheric radon concentrations are predominantly higher than the EEC.A connection of the long-term average values of the atmospheric radon and the radon potential of an area was found, by comparing atmospheric radon concentrations with indoor radon measurements and predictions of the radon potential in Austria. This indicates that the radon potential determines the average level of the atmospheric radon concentrations and weather conditions temporally modulate the atmospheric radon concentrations around this level.This work is supported by the federal ministry of Austria for climate action and the project RadoNORM, which has received funding from the Euratom research and training programme 2019-2020 under grant agreement No 900009.