bluuebunny/crossref_metadata_2025 huggingface dataset:
The Competing Forces of Hurricane-Induced Ocean Cooling
Authors: Looney Lev , Foltz Gregory
Published: February 2023

It is known that oceanic conditions can play a crucial role in the intensification of tropical cyclones (TCs) when atmospheric conditions are conducive. However, the relative roles of ocean temperature and salinity stratification on ocean mixing and TC-induced sea surface temperature (SST) cooling are unclear. Temperature stratification has competing effects on cooling from ocean mixing: stronger stratification leads to cooler water near the surface which can enhance SST cooling (thermodynamic effect), yet it also leads to resistance to vertical mixing due to a stronger density gradient and increased static stability (mixing effect). In contrast, salinity stratification almost always acts to reduce mixing and cooling. To investigate the mechanisms that control the amount of ocean cooling under a storm, we use a one-dimensional mixed layer model, initialized with different oceanic profiles and forced with cyclones of various intensities, translation speeds, and sizes. We then compare output from the mixed layer model with observations. Results consistently show that the thermodynamic effect (changes in vertical temperature gradient with density gradient held constant) is 2-3 times that of the mixing effect (changes in density stratification with temperature stratification held constant). Furthermore, we find that translation speed and storm size are the two most important factors for SST cooling, followed by temperature stratification, maximum wind speed, and mixed layer depth, respectively. These results emphasize the importance of temperature stratification over most of the tropical cyclone basins and the often overlooked role of storm size.
Developing hybrid precipitation nowcasting model with WRF and conditional GAN-based model
Authors: Choi Suyeon , Kim Yeonjoo
Published: February 2023

Physical process-based numerical prediction models (NWPs) and radar-based probabilistic methods have been mainly used for short-term precipitation prediction. Recently, radar-based precipitation nowcasting models using advanced machine learning (ML) have been actively developed. Although the ML-based model shows outstanding performance in short-term rainfall prediction, it significantly decreases performance due to increased lead time. It has the limitation of being a black box model that does not consider the physical process of the atmosphere. To address these limitations, we aimed to develop a hybrid precipitation nowcasting model, which combines NWP and an advanced ML-based model via an ML-based ensemble method. The Weather Research and Forecasting (WRF) model was used as NWP to generate a physics-based rainfall forecast. In this study, we developed the ML-based precipitation nowcasting model with conditional Generative Adversarial Network (cGAN), which shows high performance in the image generation tasks. The radar reflectivity data, WRF hindcast meteorological outputs (e.g., temperature and wind speed), and static information of the target basin (e.g., DEM, Land cover) were used as input data of cGAN-based model to generate physics-informed rainfall prediction at the lead time up to 6 hours. The cGAN-based model was trained with the data for the summer season of 2014-2017. In addition, we proposed an ML-based blending method, i.e., XGBoost, that combines cGAN-based model results and WRF forecast results. To evaluate the hybrid model performance, we analyzed the performance of precipitation predictions on three heavy rain events in South Korea. The results confirmed that using the blending method to develop a hybrid model could provide an improved precipitation nowcasting approach. Acknowledgements This work was supported by a grant from the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (2020R1A2C2007670).
Assessment of greenhouse gas emissions and mitigation potential in global degraded wetlands
Authors: Zou Junyu , Zeng Zhenzhong
Published: February 2023

Wetland is one of the ecosystem types with the largest density of organic carbon pool. The threat of declining wetland water level to carbon pools and the resulting greenhouse gas (GHG) emissions have attracted much attention. However, an assessment of emissions from degraded wetlands containing the three major greenhouse gases is still lacking. We compiled a global GHG exchange dataset that shows the non-linear water-heat pattern of GHG emissions. Combined with the Wetland Extended Trends Index, we estimated that the total GHG emissions from global degraded wetlands are 276.4 Gt CO2eq during 1950-2020. The emissions of carbon dioxide, methane, and nitrous oxide are equivalent to 10.8%, - 0.5%, and 30.5% of anthropogenic sources, respectively. Under the historical trend of wetland degradation, the emissions may increase by 1.5 times from 2021 to 2100, reaching 408 Gt CO2eq. Accordingly, wetland restoration can reduce anthropogenic carbon dioxide emissions by 10%.
Unique insights into firn structure across western Greenland’s percolation zone from hyperspectral images of shallow firn cores
Authors: McDowell Ian , Keegan Kaitlin , Skiles McKenzie , Donahue Christopher , Osterberg Erich , Hawley Robert , Marshall Hans-Peter
Published: February 2023

The physical structure of the firn column directly influences the transport and storage of infiltrating water generated by surface melt in ice sheet accumulation zones. Firn density is relatively easy to measure in field or laboratory settings and provides porosity-based estimates of the meltwater storage capacity but does not describe meltwater movement through open pore space. Pore structure controls meltwater flow and is better characterized by microstructural parameters, such as grain size. Firn grain size is therefore a state variable that needs to be accurately modeled or measured to quantify meltwater transport and storage in the firn column. Manually or digitally measuring grain size from firn samples can be tedious, time consuming, and subjective. Here, we characterize firn structure from 14 firn cores spanning approximately 1000 km across western Greenland’s percolation zone. We scanned the top 10 m of each core with a near infrared hyperspectral imager (NIR-HSI; 900-1700 nm) mounted on a linear translation stage. Leveraging the relationship between ice grain size and near infrared absorption, we invert measured reflectance to retrieve an effective grain radius, resulting in a high-resolution (~ 0.4 mm) grain size map of the firn core. We compare the retrievals against traditional grain size measurements from 7 of the cores. Additionally, the hyperspectral firn core grain size maps allow for quickly retrieving vertical ice layer distributions within the firn column and identifying regions that have been previously wetted that are not readily apparent by visual inspection. We use our unique dataset to examine correlations between grain size, infiltration ice content, and measured firn density to determine whether microstructural information can be extracted from firn density measurements. While cores provide a snapshot of firn conditions at the time of collection, we show that hyperspectral imaging of firn cores can reveal a detailed hydrologic history of the firn column and provide validation data for modeling future meltwater percolation.
Uncertainty Quantification in Hydrological and Environmental Modeling based on Polynomial Chaos Expansion
Authors: Li Zoe , Zhou Pengxiao , Ghaith Maysara
Published: February 2023

There are significant uncertainties associated with the estimates of model parameters in hydrological and environmental modeling. Such uncertainties could propagate within a modeling framework, leading to considerable deviation of the predicted value from its real value. Quantifying the uncertainties associated with model parameters could be computationally exhaustive and is still a daunting challenge to hydrological and environmental engineers. In this study, a series of Polynomial Chaos Expansion (PCE) methods, which have a significant advantage in computational efficiency, is developed to assess the propagation of parameter uncertainty. The proposed approaches were applied to two hydrological/environmental modeling case studies. The uncertainty quantification results will be compared with those from the traditional Monte Carlo simulation technique, to demonstrate the effectiveness and efficiency of the proposed approaches. This work will provide an efficient and reliable alternative to assess the impacts of the parameter uncertainties in hydrological and environmental modeling.
Predicting the fate of coastal wetlands using a simplified domain ecogeomorphic model.
Authors: Rodriguez Jose , Saco Patricia , Breda Angelo , Sandi Steven , Saintilan Neil
Published: February 2023

Predictions of the fate of coastal wetlands under the effects of sea-level rise (SLR) vary widely due to uncertainties on environmental variables, but also due to unavoidable simplifications in the models. Here, we present a simplified domain ecogeomorphic model that includes all relevant hydrodynamic, sedimentation and vegetation dynamics mechanisms that affect wetland evolution, it does not require detailed information and it is efficient enough computationally to allow the simulation of long time periods. We test this framework and apply it in different settings typically found in coastal wetlands around the world, comprising different geomorphic configurations, vegetation types, sediment characteristics and tidal regimes. Most of the wetland settings analysed are unable to cope with the high SLR rates expected by the end of the century, in agreement with results using paleo-records during periods of high SLR rates.
Unique Tall Tower Greenhouse Gas Measurements in the Amazon Rainforest: observed patterns and daily cycles
Authors: van Asperen Hella , Komiya Shujiro , Jones Sam , Botia Santiago , Lavric Jost , Warneke Thorsten , Griffith David , Trumbore Susan
Published: February 2023

The ATTO (Amazon Tall Tower Observatory) tower is a 325m tall tower located in the middle of the pristine Amazon rainforest. Since 2022, continuous greenhouse gas concentrations at different heights (4m, 42m, 81m, 150m, 273m, 321m) are monitored by use of a Spectronus FTIR-spectrometer, measuring CO2, CH4, CO, N2O and del13CO2 hourly, compliant to WMO/GAW standards. This unique measurement system is the first set up which measures greenhouse gases continuously until 325m above a tropical rainforest, which fill an important gap in the global continous observation network. The measurements can be used for regional and global modelling, and can be used for biosphere-atmosphere exchange flux estimates. In this presentation, we will show the main observations of the first year of data collection, and will present the typical daily cycles observed for the different gases at different heights.
Lunar Vertex: A PRISM Science Investigation of the Reiner Gamma Lunar Magnetic Anomaly and Swirl
Authors: Vines Sarah , Ho George , Blewett David , Halekas Jasper , Greenhagen Benjamin , Anderson Brian , Waller Dany , Jahn Jörg-Micha , Kollmann Peter , Denevi Brett , Meyer Heather , Klima Rachel , Cahill Joshua , Hood Lon , Tikoo Sonia , Zou Xiao-Duan , Weiczorek Mark , Lemelin Myriam , Fatemi Shahab , Cloutis Edward
Published: February 2023

Lunar Vertex is a mission at the intersection of multiple science communities, from planetary geology to space plasma physics. As the first Payloads and Research Investigations on the Surface of the Moon (PRISM1) investigation, scheduled for delivery to the Reiner Gamma (RG) magnetic anomaly in 2024 aboard a commercial lunar lander, Lunar Vertex will unravel the nature of the RG anomaly, the connection to and origin of the associated lunar swirl surface feature, and the structure and impact of the “mini-magnetosphere” in this region. Lunar Vertex includes a suite of magnetometers (Vector Magnetometer – Lander; VML), a fixed-mounted set of cameras (Vertex Camera Array; VCA), and a low-energy ion and electron plasma analyzer (Magnetic Anomaly Plasma Spectrometer; MAPS) on the lander. In addition, a second suite of commercial fluxgate magnetometers (Vector Magnetometer – Rover; VMR) and a multispectral imager (Rover Multispectral Microscope; RMM) are mounted on a dedicated rover that will traverse a distance of at least 500 m from the lander, providing additional multi-point measurements. The combination of magnetic field measurements taken during cruise and descent by VML and during surface operations by both VML and VMR will characterize the surface magnetic field within a strong lunar magnetic anomaly. The combined magnetic field and plasma measurements from VML and MAPS will provide direct observations of plasma populations reaching the lunar surface and the associated local magnetic field configuration. Furthermore, the lunar regolith within the RG magnetic anomaly and over different regions of the associated lunar swirl will be characterized by RMM and VCA to reveal the surface texture, composition, and particle distribution around both the lander and rover locations and the correspondence to potential surface weathering processes.
Quantification and Evaluation of OCO-2 measured XCO2 against COCCON
Authors: Das Saswati , Kiel Matthäus , Laughner Joshua , Payne Vivienne , Osterman Gregory
Published: February 2023

Carbon dioxide (CO2) is the primary greenhouse gas emitted from anthropogenic activities. Although it is naturally present as a part of Earth’s carbon-cycle, human activities influence the ability of natural sinks to reduce CO2 from the atmosphere, thus altering the carbon-cycle and necessitating the long-term monitoring of atmospheric CO2. Precise, accurate and continuous measurements of CO2 are important to this end.The Orbiting Carbon Observatory-2 (OCO-2) was launched in 2014. It is NASA’s first Earth-orbiting satellite dedicated to making observations of CO2 in the atmosphere and measuring its column-averaged dry-air mole fraction (XCO2). The primary goal of the OCO-2 mission is to provide XCO2 measurements with sufficient precision and accuracy alongside quantifying its seasonal and interannual variability. In this study, we use the new and improved OCO-2 B11 data set.In the past, the space-based XCO2 measurements from OCO-2 data have been validated against independent data sets such as the Total Carbon Column Observing Network (TCCON). In this study, we use independent measurements from the COllaborative Carbon Column Observing Network (COCCON) to identify potential biases and errors in the B11 data version and establish its robustness for use by the science community. COCCON uses portable Fourier-Transform InfraRed (FTIR) spectrometers (EM27/SUN) to measure greenhouse gases at several global sites.  Comparison of OCO-2 measurements against COCCON sites indicate similar temporal trends in XCO2 variability, with OCO-2 typically reporting higher values. Further, we evaluate the differences between the B11 OCO-2 and COCCON data sets. Finally, we analyze how OCO-2’s B11 version compares to selected COCCON and TCCON sites’ measurements in terms of capturing the seasonal cycle and growth rate of XCO2.
The scaling properties of fault networks and their relationship with the size distribution of orogen-internal seismicity
Authors: Truttmann Sandro , Herwegh Marco , Diehl Tobias , Wiemer Stefan
Published: February 2023

Understanding orogen-internal seismic deformation in regions with diffuse spatial earthquake occurrence is challenging. To gain deeper insights into the processes driving seismic fault reactivation, it is crucial to obtain information on the ubiquitous pre-existing fracture patterns. In orogens with long tectonic histories – such as the Alps – such patterns can be complex, and information on their appearance is mainly limited to observations of faults at the surface, while the detailed patterns at depth remain mostly unknown. Moreover, the link between such surface-based fault observations and active seismicity is often ambiguous. However, it has been shown that both earthquake magnitudes (Gutenberg-Richter law) and various fault properties (e.g., length, displacement) follow power-law distributions.In this work, we aim to investigate the potential relationship between the scaling properties of faults and earthquakes, which has been little explored. To this end, we use statistical tools based on field data collected with remote sensing techniques at different scales to quantitatively characterize the length distributions of exposed fault networks at different study sites in the southwestern Swiss Alps. Due to the good outcrop conditions at high elevations, the dense seismic monitoring network, and the enhanced earthquake activity, this region provides an ideal natural laboratory for the study of orogen-internal seismicity. By combining fault trace maps from three different scales, we are able to derive power law parameters and decipher similarities in scaling exponents for the different sites studied. Assuming that the fault networks exist in a similar form at depth and form the pre-existing discontinuities along which recent earthquakes develop, we compare the derived scaling laws with the frequency-magnitude distribution of local seismicity over the past 15 years. Here we find similar scaling properties between the seismicity and fracture networks only at depths below 3 km. However, in shallower regions, the large discrepancy between the scaling laws suggests that partial seismic ruptures of individual fault segments are more common than at greater depths. Such a statistical comparison of fault and earthquake scaling laws provides interesting insights into orogen-internal seismic deformation and fault reactivation processes that also have implications for regional seismic hazard.
The first EMM/EMUS stellar occultation measurements of the Martian atmosphere in both extreme and far ultraviolet wavelengths
Authors: Jain Sonal , Deighan Justin , Chaffin Michale , Holsclaw Greg , Lillis Rob , Fillingim Matthew , England Scott , Al Mazmi Hoor , Lootah Fatma , Yelle Roger , Gupta Sumedha , Schneider Nick , Al Matroushi Hessa
Published: February 2023

The major scientific objective of the Emirates Mars Mission (EMM) is to explore the global atmospheric dynamics of the Martian atmosphere both in short term (diurnal) and long term (seasonal). The Emirates Mars Ultraviolet Spectrometer (EMUS) instrument on board the EMM makes two-dimensional images ( in extreme and far ultraviolet wavelengths: 90-170 nm) of the Martian disk and exosphere to characterize the neutral densities in the thermosphere and exosphere of Mars. In this paper, we will present the first results from the stellar occultation measurements made by the EMUS instruments in October 2022. These occultation observations were not part of the original science planning and were added as a bonus EMM science. A total of seven stellar occultations were performed during the two EMM orbits spanning between 24 to 27 October. These measurements were the first stellar occultation of Mars in the EUV wavelengths (90-110 nm). Due to the higher sensitivity of the EMUS instrument, the occultation measurements were able to probe the atmosphere with an altitude sampling of 2 km or lower. The occultation measurements by SPICAM/MEx and IUVS/MAVEN were limited to 160 km due to wavelengths limited to a longward of 110 nm.  However, the use of EUV wavelengths in the EMUS stellar occultation provided atmospheric probing up to 190 km thus enabling neutral density retrieval up to the exobase region of Mars. The CO2 densities are retrieved from 90-185 km and the temperature profiles were retrieved using the constraint of hydrostatic equilibrium to the CO2 densities. We shall discuss results from the EMUS occultation campaign specifically the observed variability in the CO2 density and temperature during the occultation campaign.
Response of global land evapotranspiration to climate change, elevated CO2, and land use change
Authors: Liu Jianyu
Published: February 2023

Climate change (CLI), elevated CO2 concentration (CO2), and land use change (LUC) have strongly altered land evapotranspiration (ET) during the recent decades. The fingerprints of these drivers in ET change, however, have not previously been detected due to the lack of these three scenarios from global climate models (GCMs). Here we applied an optimal fingerprint method to detect and attribute ET change by integrated utilization of state-of-the- art global ecosystem models and GCMs. Results indicate that CLI provides the greatest contribution to increasing ET, and its fingerprint is detectable at different timescales. CO2 reduces ET in most areas covered by forests. LUC decreases ET over the tropics, while increases ET over temperate and high-latitude regions. To further subdivide the impacts of CLI, we extend the Budyko framework to quantify the contribution of precipitation (P) and potential evapotranspiration (PET) and find that the dominant role of CLI mainly depends on the contribution of P.
Airflow and scalar transport around a single fractal tree based on large-eddy simulation
Authors: Liu Shiyun , Liu Chun-Ho
Published: February 2023

Vegetation is an important component for modulating urban air quality. It can affect scalar transport, which is one of the most concerning processes in urban environment, by organizing the airflow around. In previous urban environment studies, the morphological characteristics of vegetation were usually parameterized as porosity or leaf area index (LAI), performing a spatially uniform aerodynamic behaviour. Whereas, a vegetation element has complex multi-scale structures. Predicting the scalar transport around the vegetation accurately is challenging due to the simplified parameterization. The transport processes around multi-scale vegetation should be further studied.In this study, a fractal tree model is built to preserve the length scales of sub-branches. The large-eddy simulation (LES) is employed to investigate the scalar transport around the multi-scale tree. The spatial distribution of aerodynamic behaviour and scalar transport after and over the tree is determined. The scalar transport characteristics are compared with previous studies, demonstrating the importance of preserving sub-scales in urban air quality research.
Evaluating the applicability of transient electromagnetic (TEM) data to characterize aquifer geometry in urban areas
Authors: Flores Orozco Adrián , Aigner Lukas , Ferk Josef
Published: February 2023

Understanding subsurface properties within urban areas is critical for an adequate management of groundwater, for instance to delineate the migration of pollutants, artificial recharge systems or geothermal collectors. Information is available from extraction wells, yet the resolution of the information is limited to the locations where wells are available. Geophysical methods offer an alternative to gain subsurface information. However, asphalted roads and limited accessibility might reduce the applicability of electrical methods for investigations beyond a few meters, whereas vibrations due to traffic and railroads might hinder the application of seismic methods. In this work, we investigate the use of the transient electromagnetic (TEM) method to resolve the geometry of aquifers in urban areas. We propose the use of relative small loops to gain separation from buried structures and increase data quality in late times as required to reach a depth of investigations of ca. 40 m. Measurements were conducted in gardens located within cities deploying single-loop as well as in-loop geometries using two different instruments. Additionally, we evaluate our small loop configuration in a quasi noise-free site through comparison to larger loops and electrical methods. Analysis of the data demonstrate that relative small loops (12.5 m x 12.5 m) may be a possible solution to gain information in urban areas down to a depth of 30 m, yet a minimal separation to anthropogenic structures of ca. 5 m is required. Information at such depth can not be easily gain with refraction seismic or electrical resistivity tomographic measurements in such small areas. Moreover, our results reveal the possibility to gain similar information with smaller loops (6.25 m x 6.25 m), offering the possibility to increase the separation to sources of noise (i.e., buried infrastructure) and increase the data quality. The inversion of TEM measurements collected along a 100 m profile permitted to obtain vertical and lateral variations in aquifer geometry with a maximal depth of investigation of ca. 40 m, while DC-resistivity measurements in the same profile were limited to less than 10 m depth. Stochastic inversion of the data permitted to investigate the uncertainty in the obtained model parameters (resistivity and thickness of the resolved layers, i.e., aquifer).
Observed changes in China’s methane emissions linked to policy drivers
Authors: Zhang Yuzhong , Fang Shuangxi , Chen Jianmeng , Lin Yi , Chen Yuanyuan , Liang Ruosi , Jiang Ke , Parker Robert J. , Boesch Hartmut , Steinbacher Martin , Sheng Jian-Xiong , Lu Xiao , Song Shaojie , Peng Shushi
Published: February 2023

China is set to actively reduce its methane emissions in the coming decade. A comprehensive evaluation of the current situation can provide a reference point for tracking the country’s future progress. Here, using satellite and surface observations, we quantify China’s methane emissions during 2010–2017. Including newly available data from a surface network across China greatly improves our ability to constrain emissions at subnational and sectoral levels. Our results show that recent changes in China’s methane emissions are linked to energy, agricultural, and environmental policies. We find contrasting methane emission trends in different regions attributed to coal mining, reflecting region-dependent responses to China’s energy policy of closing small coal mines (decreases in Southwest) and consolidating large coal mines (increases in North). Coordinated production of coalbed methane and coal in southern Shanxi effectively decreases methane emissions, despite increased coal production there. We also detect unexpected increases from rice cultivation over East and Central China, which is contributed by enhanced rates of crop-residue application, a factor not accounted for in current inventories. Our work identifies policy drivers of recent changes in China’s methane emissions, providing input to formulating methane policy toward its climate goal.
Possible linkage between winter extreme low temperature over central-western China and autumn sea ice loss
Authors: Ding Shuoyi , Wu Bingyi , Chen Wen , Graf Hans-F. , Zhang Xuanwen
Published: February 2023

Based on reanalysis datasets and sea-ice sensitivity experiments, this study has pointed out that the autumn sea ice loss in East Siberian-Chukchi-Beaufort (EsCB) Seas significantly increases the frequency of winter extreme low temperature over western-central China. Autumn sea ice loss warms the troposphere and generates anticyclonic anomaly over the Arctic region one month later. Under the effects of synoptic eddy-mean flow interaction and anomalous upward propagated planetary wave 2, the Arctic anticyclonic anomaly strengthens and develops toward Greenland-Northern Europe, accompanied by a weakened stratospheric polar vortex. In winter, following intra-seasonal downward propagation of stratospheric anomalies, the Northern European positive geopotential anomalies enhance and expand downstream within 7 days, favoring Arctic cold air east of Novaya Zemlya southward (the hyperpolar path) accumulating in Siberia around Lake of Baikal. In the subsequent 2~3 days, these cold anomalies rapidly intrude western-central China and induce abrupt sharp cooling, thus more frequent extreme low temperature there.
Machine learning for accelerating process-based computation of land biogeochemical cycles
Authors: Sun Yan , Goll Daniel S. , Huang Yuanyuan , Ciais Philippe , Wang Ying-Ping , Bastrikov Vladislav , Wang Yilong
Published: February 2023

Global change ecology nowadays embraces ever-growing large observational datasets (big-data) and complex mathematical models that track hundreds of ecological processes (big-model). The rapid advancement of the big-data-big-model has reached its bottleneck: high computational requirements prevent further development of models that need to be integrated over long time scales to simulate the distribution of ecosystems carbon and nutrient pools and fluxes. Here we introduce a machine-learning acceleration (MLA) tool to tackle this grand challenge. We focus on the most resource-consuming step in terrestrial biosphere models (TBMs): the equilibration of biogeochemical cycles (spin-up), a prerequisite that can take up to 98% of the computational time. Through three members of the ORCHIDEE TBM family part of the IPSL Earth System Model, including versions that describe the complex interactions between nitrogen, phosphorus and carbon that do not have any analytical solution for the spin-up, we show that MLA reduced the computation demand by 77-80%  for global studies via interpolating the equilibrated state of biogeochemical variables for a subset of model pixels. Despite small biases in the MLA-derived equilibrium, the resulting impact on the predicted regional carbon balance over recent decades is minor. Our tool is agnostic to gridded models (beyond TBMs), compatible with existing spin-up acceleration procedures, and opens the door to a wide variety of future applications, with complex non-linear models benefit most from the computational efficiency.
The Development of a New Daily Global Mesoscale Blended Ocean Surface Currents (BOSC) Product
Authors: Eisner Shaun , Carton James , Byrne Deirdre , Grodsky Semyon , Leuliette Eric
Published: February 2023

We introduce the new satellite-derived daily global mesoscale (1/6th degree) Blended Ocean Surface Currents (BOSC) product, which will be available in quasi-realtime fromNOAA CoastWatch. Existing observation-based surface current products synthesize geostrophic currents derived from satellite altimetry with an Ekman drift componentderived from surface wind stresses. BOSC builds upon this traditional approach by including additional observation-derived effects such as Stokes Drift, mesoscale advection, and high latitude surface currents inferred from Sea Ice drift. Additionally, BOSC incorporates satellite SST imagery to derive surface motion from the advection of SST features, in a process known as “feature-tracking”. These additional observations provide further constraint of surface currents in tropical, polar, and coastal regions where satellite-derived geostrophic and Ekman currents tend to provide less accurate estimates. Additionally, we offer a comparison of BOSC to existing observation-based surface current products as well as to multiple independent in situ datasets.
Ocean-air trace gas (N2O) fluxes derived from open-path FTIR atmospheric concentration gradient measurements
Authors: Wiacek Aldona , Hellmich Martin , Flesch Thomas
Published: February 2023

Open-Path Fourier Transform Infrared (OP-FTIR) spectroscopy is a well-established technique used to measure path-average trace gas concentrations [ppbv] in the atmospheric boundary layer.  Recently, the technique has been applied to derive trace gas fluxes from soils using the flux-gradient (FG) approach. We describe the novel application of OP-FTIR-FG to derive ocean-air fluxes of N2O [kg N2O ha-1 h-1] at a coastal site in the northwest Atlantic (2018, 2020-2021).  Details of OP-FTIR system deployment across Halifax Harbour (Nova Scotia, Canada) are presented and we describe the application of co-located 3-D sonic anemometer measurements to gas flux calculations.  Finally, we present a full error characterization of N2O flux and a case study of episodic negative (into ocean) flux.  This high frequency (30 min) and spatially averaging (560 m) method is well suited to coastal monitoring of ocean-air N2O fluxes and complementary to ocean-side measurements of N2O in complex circulation and microbial environments.  The possibility of other gas flux detection by this technique will be discussed.
S-wave isotropic and radially anisotropic velocity structure around the Mariana Trench inferred from ambient noise tomography
Authors: Kim Tae-shin , Chang Sung-Joon , Witek Michael
Published: February 2023

At the Mariana Trench, the Pacific plate with increasing age to the east is subducting beneath Philippine Sea plate. This subduction zone includes a volcanic arc, back-arc spreading center and many serpentinite seamounts. The Central Mariana Trench is investigated by using seismic data from 32 OBSs and 20 stations deployed in islands. Cross-correlating ambient noise records between station pairs yields fundamental-mode Rayleigh- and Love-wave dispersion curves at periods from 3 s to 35 s and at periods from 3 s to 20 s, respectively and used a 3D reference model consisting of Crust1.0 and ak135 to obtain more accurate inversion results. In particular, we also estimate group velocities between asynchronous station pairs by using permanent stations on great circle as virtual sources. By jointly inverting Rayleigh- and Love-wave dispersion curves, we calculate an S-wave isotropic and radially anisotropic velocity model, which has resolutions down to 70 km depth for isotropic S-wave velocity model and down to 40 km depth for anisotropic model. Low velocity anomalies are imaged due to the serpentinization and volcanic arc and high velocity anomalies are caused by the stagnation of fore-arc material. On the other hand, negative radial anisotropy are observed dominantly down to 15 km depth, which may be caused by vertical dykes responsible for many seamounts in this region.
Modeling urban phosphorus export to receiving waters: magnitudes, speciation, and management implications
Authors: Shafii Mahyar , Slowinski Stephanie , Bhusal Yuba , Sabur Md Abdus , Hitch Calvin , Withers William , Rezanezhad Fereidoun , Van Cappellen Philippe
Published: February 2023

Understanding phosphorus (P) dynamics in urban landscapes is an emerging research topic as P export from urban landscapes towards aquatic ecosystems causes eutrophication-related challenges in these environments. We investigated P export and forms in four research sites in Ontario, Canada, including three urban catchments and a stormwater pond, all located within the Great Toronto Area in the drainage basin of Lake Ontario. We conducted P speciation laboratory analyses on runoff and suspended sediment samples to measure total P (TP), total dissolved P (TDP), dissolved reactive P (DRP), dissolved unreactive P (TDP–DRP), and PP (TP–TDP). Multiple linear regression (MLR) models were also developed to quantify annual loadings of these P species. Models indicated that P loadings in our sites were close to the lower limit of values reported in the literature, with the simulated range of 0.2—0.46 kg ha-1 yr-1 for TP export, 0.06—0.168 kg ha-1 yr-1 for TDP, 0.011—0.073 kg ha-1 yr-1 for DRP, 0.026—0.095 kg ha-1 yr-1 for DUP, and 0.163—0.288 kg ha-1 yr-1 for PP. In our MLR models, precipitation explained a large fraction of variability in loadings with the median of 58% across all models. Moreover, we realized that as the proportion of residential land within the drainage area increased, larger amounts of P loadings were exported at the catchment scale. Results also implied that pond served as a major P sink, with annual retention of 82, 93, 91, 94, and 77% for TP, TDP, DRP, DUP, and PP, respectively. Mass balance analyses based on sequential P extraction in the sediment core samples revealed that P retention was attributed to sedimentation in the ponds, as well as chemical precipitation of P with calcium mineral phases. In terms of P composition, most of P export in our sites (72—88%) were in particulate form. Besides, the ratio between dissolved forms and TP were the highest in the catchment with the largest amount green spaces. This study demonstrates that, as land-use characteristics impose variations in constituent loadings, urban P management options also have to be varying from a catchment to another. However, sediment removing practices such as the use of ponds will certainly be a reliable P retention approach as most of urban P could be sediment-bound. Furthermore, enhancing the formation of calcium phosphate and other redox-stable mineral phases could be explored as a best management practice in existing and new ponds for improving P retention.  
Exploring multiscale nonlinear NDTs for damage detection in concrete structures
Authors: Dominguez-Bureos Marco , Hadziioannou Celine , Epple Niklas , Sanchez Trujillo Camila , Niederleithinger Ernst
Published: February 2023

It has been shown that non-destructive tests (NDTs) based on nonlinear wave propagation are more sensitive to detecting very small damages in concrete structures than linear techniques. With the aim of exploring the nonlinear effects in civil structures as a damage indicator, we perform a 1-day multiscale vibration monitoring of a test bridge equipped with a pretension system.We used the pretension system to subject the specimen to eight compression states in its longitudinal direction (400kN at the highest, and 280kN at the lowest). At every compression state, we struck the structure in the vertical direction three times at two locations on the bridge with an impulse source. Throughout the whole experiment, we recorded seismic ambient noise at different frequency bands with a 14-IMU50-sensor array to measure the acceleration and rotation rate, a 14-geophone array with a 4.5 Hz natural frequency, a DAS system, and 4 pairs of ultrasound transducers; the internal temperature of the concrete was also recorded.At the structural scale (from 1 to 40 Hz) we were able to observe different responses of the structure to pre-tension changes, depending on where the measurement took place in relation to the vertical support pillars by estimating relative velocity changes using the Coda Wave Interferometry stretching processing technique.At the material scale (ultrasound regime) we can observe temperature-dependent slow dynamics features related to changes in the seismic velocity of the concrete as a consequence of vertical strikes, and its recovery process that returns its physical properties to a steady state after the action of the impulse source.With this work, we work towards the development of new NDTs that are increasingly sensitive to small cracks and imperfections using conventional and non-conventional seismic instruments to measure linear and nonlinear wave propagation.
Is there enough land in India for scaling up the production of energy crops for sustainable bioenergy? A theoretical analysis
Authors: Kushwaha Amit , Jaiswal Deepak
Published: February 2023

India has 192.25 million ha of arable land, of which 23.2% remains fallow. 25.49, 54.24, and 1.30 million ha are used only for Rabi, Kharib, and Zayad crops, respectively. Thus, leaving a significant portion (81.03 million ha) of agricultural land remains unutilized either throughout the year or for a considerable length of a year. Additionally, 34.53 million ha of wasteland (marginal land) can produce suitable energy crops requiring fewer inputs, such as Agave. Here, we estimate the total amount of sunlight falling over unutilized land areas over one year and the theoretical efficiencies of C3, C4, and CAM to convert solar radiation to biomass to estimate the potential availability of biomass on an annual basis. We further use industrial conversion efficiencies to produce various biofuels from biomass to perform a theoretical analysis of scaling up sustainable bioenergy without causing a conflict with crop production.
Regional decrease in hazards from ice-dammed lakes in Alaska since the 1960s
Authors: Rick Brianna , McGrath Daniel , McCoy Scott , Armstrong William
Published: February 2023

As ice thins and retreats due to climate change, glacial lakes can form and grow. Rapid lake drainage can produce devastating outburst floods leading many to propose that hazards from glacial lakes are increasing. Outburst flood compilations do show an increase in the number of events documented over time, however, recent studies attribute such trends to observational bias. This leaves large uncertainty about current and future glacial-lake hazards. Here, we focus on ice-dammed lake drainages in Alaska, as a third of documented events globally occurred in this region. Using multitemporal satellite imagery (Landsat and Sentinel-2), we documented 1150 drainages from 106 lakes over 1985–2020. Accounting for the increase in satellite imagery availability over time, we find no temporal trend in drainage frequency. Furthermore, 70% of lakes decreased in estimated volume and peak discharge since the 1960s, and nearly a third of lakes released earlier through time. These results suggest a decrease in overall regional flood hazard from ice-dammed lakes and motivates an unbiased look at other regions.
The mobility and interaction of colloidal-sized poly(ethylene glycol) in column experiments with carbonate rock
Authors: Kwarkye Nimo , Lehmann Elisabeth , Nischang Ivo , Vitz Jürgen , Schubert Ulrich , Ritschel Thomas , Totsche Kai
Published: February 2023

Soil releases a significant proportion of organic colloids such as humic substances, proteins, and polysaccharides that are mobile and reactive within subsurface fluids. The mobility of such colloids is governed by colloidal hydrodynamics and frequently features strong interactions at biogeochemical interfaces in porous media. Yet, the compositional and functional diversity of organic colloids makes it difficult to trace the mobility of specific colloidal fractions and identify the alteration of surfaces following local interactions. Additionally, conventional reactive tracers used to study solute transport in the subsurface usually fail to cover hydrodynamics of small-sized organic colloids. Hence, transport principles governing the mobility of organic colloids in the subsurface are not comprehensively explored. In this study, we applied tailor-made poly(ethylene glycol) (PEG) as a reactive tracer in column and batch experiments with naturally occurring calcium carbonate as the substrate. We demonstrate that PEG transport features strong interactions at carbonate biogeochemical interfaces as known for humic substances, proteins, and polysaccharides. Such interaction can be facilitated by electrostatic interactions between PEG and the surfaces of the carbonate substrate. With the tendency to alter mineral surfaces, scanning electron microscopy (SEM) images of substrates after transport experiments showed a characteristic modification of surface morphology. Besides sharing similar reactivity with organic colloids, PEG breakthrough was reconstructed using a continuum scale model with high accuracy. With PEG being available in similar hydrodynamic sizes as small-sized organic colloids, it can be a promising tracer to follow mobility of other organic colloids in the subsurface.
Nanomaterial Interactions with the Environment and Biological Systems: Implications for Soil, Water, Plants, and Microorganisms
Authors: Darnault Christophe
Published: February 2023

Nanoscience and nanotechnology have revolutionized many sectors of the industry with the development of novel materials and technologies. With the increasing use of nanomaterials in products and applications, the presence of nanoparticles in the environment, such as in soil, sediments, water, air, and biota, is inevitable. Understanding of the physical and chemical processes and environmental conditions that govern the fate and behavior of nanomaterials in the environment is essential to strengthen the environmental and human health security. This study discusses the role of physical and chemical processes and environmental conditions on the fate, transport, behavior, transformation, and toxicity of metal based nanoparticles and their environmental impacts, with a focus on terrestrial and aquatic systems, as well as plants and microorganisms. Research on the interactions of nanomaterials with the environment and biological systems will allow the development of models contributing to advancing knowledge on the behavior and fate of nanoparticles in the environment and assessing their potential risk in the environment.
Comparison of 300 m and 100 m uSINGV clear-day simulations for Singapore
Authors: Patel Pratiman , Chen Song , Dipankar Anurag , Roth Matthias , Lean Humphrey , Zhang Hugh , Moise Aurel
Published: February 2023

Increasing urbanization and its implication for human health, outdoor thermal comfort, air quality or energy consumption necessitate a need for high-resolution urban modelling. In this study, we evaluate uSINGV, a coupled urban-atmosphere research model used by the Singapore Meteorological Service, for four clear-day over Singapore using two different spatial resolutions of 300 and 100 m, respectively. The model is modified to incorporate urban morphology and land use/land cover datasets which are based on European Space Agency climate change initiative data (ESA CCI) at 300 and local datasets at 100 m spatial resolution. The evaluation is carried out for near-surface variables such as temperature, specific humidity, wind speed, and turbulent surface fluxes using Kling-Gupta efficiency (KGE'), root mean square error (RMSE) and mean absolute error (MAE) as model evaluation metrics. Results suggest that temperature and specific humidity are similar for 300 m and 100 m spatial resolution. On the other hand, for 100 m (300 m), the 10 m wind speed has a KGE’ of 0.45 (0.15), RMSE of 0.69 (1.42) m/s, and MAE of 0.55 (1.26) m/s, hence showing improvements from 300 to 100 m spatial resolution. In addition, sensible heat flux for 100 m resolution simulations is closer to observations, while latent heat flux is overestimated. Overall, uSINGV is able to produce reliable simulations at 100 m spatial resolution, thereby showing promise for improved understanding of detailed urban climate processes.
Increasing role of Kuroshio-Oyashio Extension variations as a conveyor of decadal ocean oscillation to seasonal air-sea heat exchange since the late 1980s
Authors: Joh Youngji , Delworth Thomas , Wittenberg Andrew , Yang Xiaosong , Rosati Anthony , Johnson Nathaniel , Jia Liwei
Published: February 2023

The Kuroshio-Oyashio Extension (KOE) is the North Pacific oceanic frontal zone where air-sea heat and moisture exchanges allow strong communication between the ocean and atmosphere. Using satellite observations and reanalysis datasets, we show that the KOE surface heat flux variability constitutes an essential component of the seasonal and decadal Pacific ocean/atmosphere variability. We first show a strong covariability between the winter air-sea heat exchange and decadal fluctuations of the Kuroshio Extension (KE) sea surface height (SSH; the SSH reflects upper-ocean heat content anomalies). Interannual to decadal variations of ocean subsurface heat content become strongly connected to the surface during early winter (i.e., November-December-January, NDJ), where they influence the strong ocean-to-atmosphere heat transfer over the KOE. During the early winter (NDJ), the enhanced Aleutian-Low-like atmospheric circulation associated with KE SSH helps to induce a substantial sea-air temperature difference through northwesterly winds over the warm ocean surface. The analysis over an extended time period (i.e., 1959-2022) exhibits that the KOE upward latent and sensible heat flux anomalies have been significantly enhanced since the late 1980s mainly due to increasing variance of the oceanic variability (e.g., KOE sea surface temperature) rather than atmospheric forcing changes (e.g., Aleutian Low). Our findings suggest that winter KOE heat flux variations can be useful climate proxies (e.g., KE SSH) as a physical indicator that links the subsurface ocean and atmosphere.