bluuebunny/crossref_metadata_2025 huggingface dataset:
Bacterial decomposition of dissolved organic matter: including the colloidal perspective
Authors: Andersson Erika , Tranvik Lars , Groeneveld Marloes , Tunlid Anders , Persson Per , Olsson Ulf
Published: March 2024

Dissolved organic matter (DOM) is a major carbon pool and considered the most bioavailable and most mobile fraction of organic matter. DOM is generally defined as the organic matter passing a filter pore size of 0.2 or 0.45 µm, and this size cut off means that DOM not only contains dissolved molecules but also colloidal objects and aggregates up to a few hundred nanometres. The properties of this colloidal DOM fraction, such as for example size, shape, and surface charge, will affect its actual bioavailability and mobility in the environment. Although previously not well studied, there has recently been a growing interest in this colloidal fraction of DOM.We have studied DOM extracted by water from a boreal spruce forest soil, filtered through a 0.2 µm pore size. By using a combination of spectroscopy techniques, such as NMR, and light (SLS, DLS), X-ray (SAXS) and neutron (SANS) scattering techniques, we can access chemical and physical information on both the molecular and colloidal fractions of DOM.Our results show that the colloidal DOM has a homogenous chemical composition, and that carbohydrates is the dominating chemical component in both the colloidal and molecular DOM. The colloids have a mass fractal structure which does not change upon dilution and they are electrostatically stabilised against aggregation. In a lab scale study, we investigated the bacterial decomposition of this DOM during a two-month incubation. The molecular fraction of DOM was quickly decomposed. However, no change was observed for the colloidal DOM, constituting ca. 50% of the carbon, indicating that it persisted bacterial decomposition.Our results suggest that colloidal properties could be an important but hitherto overlooked aspect to the central question of what dictates organic matter reactivity and persistency in different environments and across different time scales. Our current work extends from soil solution to aquatic ecosystems, to assess the ubiquity of the colloidal fraction of DOM.
SWOT Level-3 Overview algorithms and examples
Authors: Pujol Marie-Isabelle , Dibarboure Gerald , Faugere Yannice , Delepoulle Antoine , Briol Frederic , Raynal Matthias , Ubelmann Clement , Chevrier Robin , Treboutte Anaelle , Prandi Pierre
Published: March 2024

The Surface Water Ocean Topography (SWOT) mission was launched in December 2023.It is the result of cooperation between CNES, NASA and their partners from the Canadian and UK Space Agencies. SWOT carries a unique altimetric payload, including a Ku-band Jason-class nadir altimeter and a Ka-band SAR-interferometric (KaRIn) wide-swath altimeter providing 2 swaths 50-km wide. It offers new opportunity for the observation of the small mesoscale structures over the oceans, including near coast and high latitude areas. Thanks to these observation capabilities, SWOT could contribute to a better understanding of the physical processes at play at these scales, and to the applications that flow from them.Few months after its launch, Level-2 product of the KaRIn measurement were made available for the SWOT Science Team. These products however remain complex and oriented for the altimetry expert community, while many non-expert users may need the swath measurement for different applications. To answer these needs, a Level-3 product was developed in the context of the SWOT Science Team Project DESMOS. It is the result of different processing steps including the use of the state of the art of different geophysical corrections (e.g. Mean Sea Surface, ocean tide), aiming to improve the quality of the sea level measurement at small mesoscale; the multi-mission calibration, that makes the SWOT measurements consistent with other altimeters; the data selection, to identify invalid measurements; the sea surface height noise-mitigation, aiming reduce the noise level on SSHA and allowing the estimation of the geostrophic current and vorticity. We present here the SWOT KaRIn Level-3 product.
Design and Validation of a portable sampler to monitor pollens at street level in the ambient environment
Authors: Dhawan Sachin , Kumar Anand , Khare Mukesh , Mehta Dalip Singh
Published: March 2024

In the ambient environment where gases and various particles coexist, pollen is a chief biological airborne particle among atmospheric bioaerosols. Despite its significance, pollen surveillance in many countries including India is overlooked as most of the air quality monitoring, predominantly targets PM2.5, PM10, or other gaseous pollutants. Pollens are not only vital for plant reproduction but they interact with various atmospheric elements, trigger allergies, influence genetic exchange and cause environmental shifts by fostering microorganism transmission. Despite their profound impacts, the epidemiological effects of pollens remain underexplored. Majority of the pollens aggravate diseases like asthma or COPD in human beings and, therefore the investigative studies on pollens become crucial for disease management. The sampling of pollens involves multiple parameters e.g., wind speed, turbulence, and orientation of sampler, affecting their concentrations. Suction-based impaction pollen samplers offer promising pollen sampling due to their adaptable cut points and high throughput. However, if such suction-based samplers are designed to match human breathing rates of 12-16 LPM and a D50 of 2 µm, the retrieval of pollens is efficiently optimized. In this work, a rectangular slit-based pollen sampler was designed after carrying out extensive numerical modelling for creating a 3D design of the sampler. Further, the Computational Fluid Dynamic (CFD) employing Poly-Hexcore volume meshing, and a k-w turbulence model combined with the Discrete Phase Model (DPM). was used to validate the design of the sampler., The DPM includes particle sizes ranging from 2 – 100 µm with simulations carried out in two regions i.e., solid (slide) and fluid (air). The slide's boundary condition was set as ‘trap’ since it was coated with a sampling medium to capture pollens. Further, inlet and outlet boundary conditions were set as ‘escape’. The efficiency of pollen collection as observed from the simulations, ranged between 60% - 100%, gauged through particle trajectory and streamlines. Pollen collection efficiency was found to increase when staggered inlet and outlet mass flow geometry were used. Moreover, the use of a trapping sampling medium restricted particle jump-off, altering the particle cut-off point towards smaller sizes. This shift, while enhancing capture efficiency, also influenced the particle size range the sampler can effectively trap. In summary, the pollen sampler designed in this work exhibited a better collection efficiency compared to traditional samplers and was also representative of the pollen inhalation rate of human beings. Further, field testing was also done for the sampler to see the presence of pollen in ambient air.
Solar wind controls on Martian proton aurora brightening and atmospheric ion loss intensifying
Authors: He Fei , Fan Kai , Hughes Andrea , Wei Yong , Cui Jun , Schneider Nicholas , Fraenz Markus , Zhang Xiao-Xin , Meng Qingyu , Wang Xiaodong
Published: March 2024

Charge exchange between solar wind protons and local hydrogen atoms generates hydrogen energetic neutral atoms (H-ENAs) in the extended neutral hydrogen corona surrounding Mars. The following collisions between H-ENAs and atmospheric molecules generate a distinct proton aurora. How the solar wind influences the proton aurora activity in the short term is not well unknown. We found that there are synchronized proton aurora brightening and atmospheric ion loss intensifying on Mars, both controlled by solar wind dynamic pressure, using observations by the Mars Atmosphere and Volatile Evolution spacecraft. Significant erosion of the Martian ionosphere during periods of high dynamic pressure indicates at least five-to-tenfold increase in atmospheric ion loss. An empirical relationship between ion escape rate and auroral emission enhancement is established, providing a new proxy of Mars’ atmospheric ion loss with optical imaging that may be used remotely and with greater flexibility.
A systematic evaluation of high-cloud controlling factors
Authors: Wilson Kemsley Sarah , Nowack Peer , Ceppi Paulo
Published: March 2024

Clouds strongly modulate the top-of-the-atmosphere (TOA) energy budget. While most evidence indicates that changes in cloud-induced radiative anomalies at the TOA likely amplifies warming, the magnitude of this global cloud feedback remains highly uncertain. “Cloud Controlling Factor” (CCF) analysis is an approach that can be used to tackle this uncertainty, deriving relationships between large-scale meteorological drivers and cloud-radiative anomalies which can subsequently be used to constrain cloud feedback. However, the choice of meteorological controlling factors is crucial for a meaningful constraint, and while there is rich literature investigating ideal CCF setups for low-level clouds, there is a distinct lack of analogous research that explicitly targets high clouds.Here, we use ridge regression to systematically evaluate CCFs that specifically target high cloud formation and cessation using historical data. We evaluate the addition of five candidate CCFs to previously established core CCFs within large spatial domains to predict longwave high-cloud radiative anomalies: upper-tropospheric static stability (SUT), sub-cloud moist static energy, convective available potential energy, convective inhibition, and upper-tropospheric wind shear. We identify an optimal configuration including SUT, and show that the spatial distribution of the  SUT  ridge regression coefficients are congruent with the physical drivers of known high-cloud feedbacks. We further deduce that inclusion of SUT into observational constraint frameworks may reduce uncertainty associated with changes in anvil cloud amount as a function of climate change. These results highlight upper-tropospheric static stability as an important CCF for high clouds and longwave cloud feedback, which we begin to explore using modelled data under an abrupt quadrupling of CO2 (abrupt-4xCO2).
Precipitation over Madagascar: Assessment of observed datasets and CMIP6 HighResMIP models for further analysis of drought and its impact on vegetation 
Authors: Randriatsara Herijaona Hani-Roge Hundilida , Holtanova Eva
Published: March 2024

Understanding historical evolution and future projections of drought are crucial for Madagascar, which experiences drought almost every year. Not only it contributes to the economic development of the area but it also helps to mitigate direct and indirect impacts of drought on human’s lives and natural ecosystems. To begin with, it is crucial to use accurate datasets for assessing drought in order to get reliable findings. However, Madagascar lacks reliable station datasets. Here, we present the first evaluation of performance of available observed precipitation datasets over the country: gridded precipitation datasets from gauge-based, reanalysis and satellite estimates. Among the 15 analyzed datasets, CHIRPS (Climate Hazards Group Infrared Precipitation with Station data version 2) and ERA5 (European Centre for Medium-Range Weather Forecasts reanalysis fifth generation- Land dataset) the lowest biases compared to the rest. Thus, they are used as the reference for evaluating the performance of CMIP6 HighResMIP simulations. The assessment employs diverse methods, accompanied by the use of the Taylor skill score for ranking the overall performance of the models. The results show that EC-Earth3P-HR, ECMWF-IFS-HR, ECMWF-IFS-LR and HadGEM3-GC31-MM perform the best. The evaluated precipitation datasets are used in current ongoing research of recent drought evolution and its impact on vegetation over Madagascar. Preliminarily results show that the SPI (Standard Precipitation Index) exhibit decreasing trend for all chosen SPI scales (SPI3, SPI6 and SPI12). This indicates that the occurrence of drought over Madagascar has amplified within the study period of 1981 to 2022. Eventually, the evaluation of future projections of drought over the Island would be the next goal to be tackled in order to provide bases for planning appropriate measures in lessening the impact of drought, building effective adaptation strategies and structuring climate change policies.
On-disk Observation of Bidirectionally Propagating Plasma Blobs Near the Reconnection Site of a Solar Eruption
Authors: Hou Zhenyong , Tian Hui , Madjarska Maria , Chen Hechao , Samanta Tanmoy , Bai Xianyong , Li Zhentong , Su Yang , Chen Wei , Deng Yuanyong
Published: March 2024

Current sheet is a commonly observed structure involved in solar eruptions. However, the physical properties of its fine structures during a solar eruption are rarely investigated. Here, we report an on-disk observation that displays 139 compact, circular or elliptic bright structures, presumably plasma blobs, propagating bidirectionally along a plasma sheet during a period of about 24 minutes around the peak time of an eruptive flare. From extreme ultraviolet images, we distinguish a plasma sheet connecting the flare loops and the erupting filament. The average width, duration, and projected velocities of these blobs are about 1.7±0.5 Mm, 73±54 s, and 190±81 km/s, respectively. The reconnection site rises with an average velocity of about 51 km/s. We have obtained the temporal variation of the blob number during the solar eruption, which is similar to that of the GOES X-ray flux. The observational results suggest that plasmoid instability plays an important role in the energy release process of solar eruptions.
Elevation-dependent warming in the Alps estimated from MAR simulations over 1961-2
Authors: Castellanos Ian , Ménégoz Martin , Blanchet Juliette , Beaumet Julien
Published: March 2024

Regional imprints of global warming have to be investigated to predict the impact of climate change on a local scale and inform mitigation and adaptation policies. The rate of warming as a function of elevation in mountainous regions is yet to be fully characterized and understood. This study aims to identify elevation-dependent warming features in the Alps as well as its physical drivers, using MAR (Modèle Atmosphérique Régional) simulations with a 7kmx7km resolution over 1961-2100, under different climate scenarios. Different seasonal patterns have been found, most notably a maximum of warming at intermediate elevation (~1500m to 1800m) in Spring related to earlier snow melting in future projections. This maximum of warming moves towards higher elevations over the XXIst century. Elevation-dependent warming is found to be different in the free-atmosphere and along the slopes of the mountains, highlighting the major impact of surface processes, such as changes in albedo, in the drivers of climate change in the Alps.
Tracing sources of diffuse PFAS pollution: PFAS contamination in soil near a Municipal Waste-to-Energy plant
Authors: Dijkstra Joris , Brunschwiler Noemi , Griffioen Jasper
Published: March 2024

Poly- and perfluoroalkyl substances (PFAS), among which are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are common contaminants in Dutch soils, originating from fluorpolymer- factories (for PFOA), firefighting training grounds (for PFOS), or other often unknown sources. Previous research suggests that Municipal Waste-to-Energy (WtE) plants may be a source for diffuse PFAS contamination in the Netherlands, where 13 WtE plants are currently operational. Even though PFAS compounds should be eliminated at the temperatures at which WtE plants operate, the existence of “cold spots” in the oven is known and may imply that PFAS survive the combustion process. To investigate the potential contribution of WtE plants to diffuse PFAS contamination, a case study was set up in which topsoils surrounding a WtE plant in Alkmaar (Netherlands) were investigated. Ten locations were selected of which the soil profiles were undisturbed at least for 50 years and for which no other known PFAS sources are nearby. Eight locations were in the predominant wind direction (from SW to NE) and within a 5 km radius from the WtE plant. Two reference locations were located upwind. Each location was drilled to a depth of 80 cm and sampled with 10 cm intervals. Samples were analysed for 10 different PFAS and various bulk chemical and physical soil properties. In addition, PFAS was analysed in ashes from several modern WtE plants.PFAS content is generally above national threshold values in the top layer of the soil (
Analysis of correlations between the South Atlantic Convergence Zone and Climate Indices Derived from the Pacific and Atlantic Oceans for Evaluating Teleconnections
Authors: da Fonseca Aguiar Louise , Galves Vitor Luiz , Cataldi Marcio , Marcolino Nielsen David , Sancho Lívia , Passos Elisa
Published: March 2024

The South Atlantic Convergence Zone (SACZ) is one of the most important phenomena that influences the precipitation patterns in Brazil’s Southeast and Midwest regions during the spring and summer. These regions play a major role for the country’s economy, particularly in terms of agriculture and industrial production. It is estimated that the SACZ is responsible for approximately 25% of the total volume of rain in Southeast Brazil from October to April. The conditional probability of a natural disaster occurring when the SACZ is present in the region is around 24%, while, in the case of a disaster occurring in the Southeast, the conditional probability of observing the presence of SACZ is 48%. This work provides an initial understanding of how different teleconnection patterns can influence the configuration, position, and intensity of the SACZ. The goal is to investigate potential correlations between the SACZ index, the El Niño Southern Oscillation (ENSO) indexes, the Atlantic Sea surface temperatures (SST) between Central America and Africa, the Brazil-Malvinas Confluence (BMC) and the Antarctic Oscillation (AAO). For the SACZ indexes, the monthly data was derived by summing the values for each month. This process utilized data spanning from 1980 to 2010 to establish the monthly climatology. The monthly indexes and anomalies were compared with the monthly climatology values from January 1999 to December 2022. For daily indexes of BMC, Niño1+2, Niño 3, Niño 3.4, Niño 4, Atl_N, Atl_NL, Atl_C and Atl_CL sea surface temperature (SST) anomalies were referenced against a climatology spanning from 1971 to 2000. In these cases, monthly data was obtained through the average of the daily indexes. Finally, AAO indexes were already obtained monthly. In this case, the time series were normalized using the standard deviation of the monthly index, based on the 1979-2000 period. Three Pearson correlations were calculated monthly for the period from 1999 to 2022. These correlations were evaluated for the average from October to March, October to December, and from January to March. The preliminary results showed that colder anomalies of the Equatorial Pacific (La Niña), the North Equatorial Atlantic, and the CBM, in conjunction with a positive phase of the AAO and warmer waters of the Central Equatorial Atlantic, are associated with the occurrence and configuration of the SACZ (and vice versa). This signal is most pronounced in the period from October to December and during the October to March timeframe, while it weakens in the months from January to March.
Considering aftershock-induced damage accumulation in seismic loss assessments
Authors: Gouache Corentin , Allemand Adélaïde
Published: March 2024

This work outlines a methodology developed for considering aftershock-induced damage accumulation in seismic loss assessments. In particular, it adapts this methodology to the case of reinforced concrete (RC) frames in mainland France and incorporates it to an already-developed seismic loss assessment model.The methodology consists in dividing the RC buildings into sub-categories of buildings, depending on parameters influencing the vulnerability of the structures. For each category, a set of discrete damage states is defined. For each state Di, fragility functions are derived, enabling to compute the probability of transitioning to another damage state Di+1, knowing the intensity of the ground motion. Therefore, this methodology allows to estimate the final damage state reached by a structure submitted to a series of ground motions.In order to do so, the pool of French RC buildings is analysed so as to create realistic and general models of RC frames. Ground motions are selected from an open database, following some criteria. Fragility functions are then derived (for each type of building) by applying numerous ground motions to the models and assessing the probabilities of reaching each damage state. The methods for constructing those fragility functions are evaluated from the literature. The choice of relevant parameters measuring damage and measuring ground motion intensity is also scrutinized.
EU-Funded LIFE Projects Influence in Land Use/Land Cover Changes in Insular Ecosystems: The Case-Study of São Miguel Island (Azores)
Authors: Tiengo Rafaela , Merino-De-Miguel Silvia , Palacios-Orueta Alicia , Uchôa Jéssica , Gil Artur
Published: March 2024

Small oceanic islands, like São Miguel Island (Azores), show high vulnerability to climate change impacts, biological invasions, and land-use/land-cover changes that threaten their biodiversity and affect their ecosystem functions and services. Organized and long-term nature conservation actions and projects such as those funded by the EU LIFE Programme have been fundamental to mitigating biodiversity loss in the eastern part of São Miguel Island since 2003. The use of remote sensing-based approaches may constitute a cost-effective way to support the management, monitoring, and control of these LIFE projects. In this work, a land-use/land-cover change detection approach focusing on the 2003-2022 LIFE Projects intervention areas was applied by using the RAO’s Q diversity index, which holds significant potential for monitoring the proliferation of invasive plant species and alterations in land use patterns. Using the ASTER, Landsat 8, and Sentinel-2 images from the Google Earth Engine on Google Colab and Python as the programming language, the average distribution of RAO’s Q diversity index values in the intervention areas was analyzed. The Normalized Difference Vegetation Index was calculated for the different years within the LIFE projects. The Classic Rao was calculated, giving the ability of this methodology to identify and evaluate diversity, making it possible to determine areas in which changes occurred in the project areas and the period in which these areas underwent interventions. By evaluating the effectiveness of conservation initiatives on small oceanic islands and archipelagos, we can gain insights into the ecological responses and long-term sustainability of these projects. This knowledge can inform future conservation strategies, contribute to the broader field of island conservation, and enhance our understanding of the unique dynamics and challenges associated with protecting biodiversity in insular environments.
Application of air sensors to support clean cooking initiatives at education centres in low- and middle-income countries using Accra High School, Ghana as a case study.
Authors: Ablo Victor Dzidefo , Hodoli Collins Gameli , Agyeman-Rawlings Zanetor , Tsikata Kojo , Offei-Darko Lord , Schmitt Angela , Quansah Reginald , Malings Carl , Westervelt Daniel M , Mead Mohammed Iqbal
Published: March 2024

Miniaturised air sensors (otherwise known as “small sensors”, “low cost sensors” or “lower capital cost sensors”) have been used extensively for air quality campaigns globally primarily as pilot studies. To date, their usefulness for applications to generate robust evidence for social intervention programmes, especially in geographies with poor environmental and social policies (such as those encountered in many parts of the global south), is limited. This study focused on the application of air sensor data to produce evidence to support interventions such as clean cooking initiatives at education centres in low- and middle-income countries using Accra High School located in the city of Accra, Ghana as a case study. We deployed a calibrated Airnote PM2.5 air sensor at Accra High School from June 01st to July 23rd, 2023. We employed time series, calendar and diurnal variation analysis to present the reported data. We found that 24-hour PM2.5 pollution was 7 times higher than the World Health Organization Air Quality Guidelines. The calendar plots show that cooking staff, predominantly women, are routinely exposed to unhealthy, very unhealthy or hazardous levels of PM2.5, a species linked to the incidence of asthma, COPD, heart disease, cancers and increasingly poor birth outcomes and dementia. Peak levels (~140 µgm-3) were observed between 06:00 and 18:00 hrs and are linked to cooking activity with charcoal and fuelwood. Hourly PM2.5 concentration ~300 µgm-3 was also periodically observed. These preliminary results were presented to the member of Parliament, Hon Dr Zanetor Agymang-Rawlings in whose jurisdiction the study was collaboratively conducted. Per the recommendations, a clean cooking initiative was launched with the replacement of old cooking appliances. This study illustrates the usefulness and application of air sensors to support clean cooking initiatives in environments with poor energy sources for cooking and heating. This is a directly reproducible approach which is possible to implement across many areas of continental Africa. We recommend the implementation of continuous air quality measurements at and around cooking areas to understand the impacts of newer more efficient cooking appliances on local air quality. We also recommend the use of the data for air pollution and sustainability science education at the Accra High School or in similar settings with air sensor campaigns. 
Developing a land-cover-assisted spatiotemporal fusion model for producing pre-2000 MODIS-like data over the continental United States
Authors: Zhang Zhicheng , Xiong Zhenhua , Pan Xiaoyu , Xin Qinchuan
Published: March 2024

Long-term satellite-based imagery provides fundamental data support for identifying and analyzing land surface dynamics. Although moderate-spatial-resolution data, like the Moderate Resolution Imaging Spectroradiometer (MODIS), were widely used for large-scale regional studies, their limited availability before 2000 restricts their usage in long-term investigations. To reconstruct retrospective MODIS-like data, this study proposes a novel deep learning-based model, named the Land-Cover-assisted SpatioTemporal Fusion model (LCSTF). LCSTF leverages medium-grained spatial class features from Landcover300m and temporal seasonal fluctuations from the Global Inventory Modelling and Mapping Studies (GIMMS) NDVI3g time series data to generate 500-meter MODIS-like data from 1992 to 2010 over the continental United States. The model also implements the Long Short-Term Memory (LSTM) sensor-bias correction method to mitigate systematic differences between sensors. Validation against actual MODIS images confirms the model’s ability to produce accurate MODIS-like data. Additionally, when assessed with Landsat data prior to 2000, the model demonstrates excellent performance in reconstructing retrospective data. The developed model and the reconstructed biweekly MODIS-like dataset offer significant potential for extending the temporal coverage of moderate-spatial-resolution data, enabling comprehensive long-term and large-scale studies of land surface dynamics.
QBO-composite mean meridional circulation: ERA5 and MIPAS tracer-derived residual velocities 
Authors: Kerzenmacher Tobias , Grabowski Udo , von Clarmann Thomas , Stiller Gabriele
Published: March 2024

This study focuses on analyzing the Quasi-Biennial Oscillation (QBO)-composite mean meridional circulation during the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measurement period 2002 to 2012, using both ERA5 reanalysis and MIPAS tracer-derived velocities. The investigation employs the approach described in the S-RIP report: We have  deseasonalized QBO-W onsets at 20 hPa and have compared zonal-mean vertical and meridional velocities extracted from MIPAS tracer measurements with reanalysis data from ERA5.
 
To infer the effective transport velocities and mixing coefficients of the 2-D atmosphere, we employ a direct inversion technique utilizing tracer measurements from MIPAS (Clarmann and Grabowski 2016). This method involves the integration of the continuity equation over time and determines those vertical and meridional mean velocities that best reproduce the measured trace gas distributions. The advantage of the method is that it does not involve a dynamic model; instead it provides independent observation-based information on the mean meridional circulation.
 
This inversion method is applied to MIPAS monthly zonal mean tracer measurements of the years 2002 to 2012.  This study reveals QBO patterns in tracer-retrieved velocities within the mean circulation. Observed structures compare favourably with S-RIP reanalysis results. Quantitative comparisons reveal differences that have the potential to pinpoint certain processes that might not be adequately represented in the models or deficiencies in the tracer-based inversion of the continuity equation.
 
These results underscore the utility of MIPAS tracer measurements for enhancing the understanding and modeling of mean-meridional circulation in Earth's atmosphere.
 
Reference
von Clarmann, T. and Grabowski, U.: Direct inversion of circulation and mixing from tracer measurements – Part 1: Method, Atmos. Chem. Phys., 16, 14563–14584,  https://doi.org/10.5194/acp-16-14563-2016, 2016.
An ensemble reconstruction of ocean temperature, salinity, and the Atlantic Meridional Overturning Circulation 1960–202
Authors: Hermanson Leon , Dunstone Nick , Eade Rosie , Smith Doug
Published: March 2024

Ocean reanalyses covering many decades, including those with few observations, are needed to understand climate variability and to initialize and assess interannual to decadal climate predictions. The Met Office Statistical Ocean Re-Analysis (MOSORA) exploits long-range covariances to generate full-depth reanalyses of monthly ocean temperature and salinity even from sparse observations. The latest version of MOSORA presented here is for the first time an ensemble that samples uncertainties in these long-range covariances. The ensemble is created by using initial covariances from different perturbed-physics historical model runs and these are then improved with observations using an iterative process.We demonstrate that covariances are mostly improved by iteration, and that this procedure, using very sparse observations typical of the 1960s, captures many features of analyses benefiting from modern observation density. We investigate the ensemble spread and find that salinity trends in the covariances from model runs can introduce unexpected changes in the reanalyses. In the Gulf of Guinea, there are insufficient observations to constrain the model covariances, which vary due to different model representations of Antarctic Intermediate Water. If models are improved in this region, this could lead to a better analysis of temperature and salinity.We nudge the reanalyses into an ensemble of coupled climate models to produce estimates of the Atlantic Meridional Overturning Circulation (AMOC) back to 1960. At 26°N, the AMOC shows decadal variability consistent with observations at this latitude and shows signs of strengthening in recent years. The ensemble spread in AMOC reconstructions at this latitude increases with time as more observations interact with uncertain covariances. More observations should be able to better constrain these covariances.At 45°N, the amount of decadal variability in the AMOC varies between members. The uncertainty of our reconstruction at this latitude varies through time partly related to the number of observations made on the western boundary, just off the Grand Banks of Newfoundland. This shows potential for targeted and sustained observations to constrain the transport into the North Atlantic subpolar gyre.
High temporal (hourly) and spatial (250 m) resolution of surface NO2 concentrations derived from AHI and MODIS measurements leveraging chemical and physical linkages among diverse pollutants
Authors: Liu Jianjun , Meng Nan
Published: March 2024

Surface Nitrogen dioxide (NO2) is strongly associated with various detrimental impacts on human health and the environment. Most current satellite-derived surface NO2 products predominantly utilize the vertical columnar density (VCD) of NO2 retrieved from low-earth orbiting hyperspectral satellites (e.g., OMI, TROPOMI, etc.) as the major predictor, and often experience limitations in terms of coarse temporal frequencies and spatial resolution. The capability of surface NO2 products to accurately assess the temporal and spatial variability of NO2 concentration is subsequently constrained. We proposed a novel conception to generate surface NO2 concentrations with high temporal (<= hourly) and spatial (250m) resolution from multispectral satellites (e.g., AHI and MODIS) using machine learning approach, leveraging the coexistence and chemical and/or physical interconnections among various pollutants. The approach was tested in the urban agglomeration regions of China characterized by severe pollution. The model was validated against surface measurements with the high and stable accuracies and outperforms most models developed in previous similar studies using VCD of NO2 measurements. The model generated NO2 product has been effectively employed to continuously monitor the temporal and spatial evolution of NO2 pollution during the air pollution episodes and locate the sources of NO2 emission. The proposed approach broadens the applications of MODIS and AHI satellites (and potentially others) in atmospheric environment research, providing a potential alternative pathway for the advancement of ground-level pollutant products through satellite remote sensing.
Oil and gas wellbore leakage in Canada: key reporting uncertainties and measurement knowledge gaps
Authors: Seymour Scott , Xie Donglai , Kang Mary
Published: March 2024

Depleted oil and gas formations and associated wells can be exploited for use as energy or carbon dioxide storage infrastructure. However, a loss of wellbore integrity can result in the uncontrolled migration of fluids out of the well, risking groundwater contamination and releasing greenhouse gases (e.g., methane, carbon dioxide, hydrogen) into the atmosphere. In Canada, emissions specifically related to wellbore integrity and subsurface-based leakage have been monitored, measured, and reported by the oil and gas industry for more than a decade, resulting in some of the largest datasets to track such wellbore emissions. While these reporting systems were not necessarily designed to track methane emissions, both the provincial and federal governments nevertheless use these data to estimate methane emissions associated with subsurface wellbore leakage.  Moreover, incomplete reporting by the industry has resulted in highly uncertain methane emission magnitudes, and attempts by federal and provincial governments to resolve these issues yield emission estimates varying by more than a factor of two. Further, poorly understood emission mechanisms are likely to yield even more uncertainty in total emissions from wellbore leakage.In this presentation, we illustrate the highly uncertain nature of methane emissions due to subsurface wellbore leakage in Canada using industry-reported data for the provinces of Alberta and British Columbia, regions covering more than 80% of crude oil and 95% of natural gas production nationally. We illustrate the sensitivity of these methane emission estimates using a variety of assumptions employed by the different governments for incomplete data, highlighting the key knowledge gaps for this source of emission. The different assumptions result in estimates varying by a factor of 3, and more troublingly, connotate fundamentally different understandings about wellbore leakage causes, sources of fluid, and progression of emission rates over time. We make initial recommendations for wellbore leakage monitoring and measurements to improve Canada’s methane quantification but with more broad applicability for monitoring well fluid leakage more generally.
Using Chlorine-36 to understand the sources of solutes in rivers: A new use for an old tracer
Authors: Cartwright Ian , Zhou Zibo , Howcroft William , Fifield Keith , Cendon Dioni
Published: March 2024

The radioisotope 36Cl, which has a half life of 301 ka, is traditionally used to estimate groundwater residence times of deep old groundwater in large basins. However, systematic variations in R36Cl values in young shallow catchment waters permit its use in determining the sources of solutes in rivers. Elevated R36Cl values in precipitation were recorded during the 1950s to 1970s due to the atmospheric nuclear tests. Some of this bomb-pulse 36Cl is likely to still be present in shallow catchment waters. Additionally, as R36Cl values of precipitation generally increase with distance from the ocean, groundwater older that ~7 ka that was recharged during periods of low sea levels in the Holocene is likely to have higher R36Cl values than modern rainfall. Most of the water from within catchments that sustains streamflow (e.g., the shallower parts of the groundwater system, interflow, bank storage waters, riparian groundwater) is less than a few thousand years old. There is negligible decay of 36Cl over those timescales, and thus R36C values will reflect the initial R36C values of those waters.River water from the intermittent Avoca catchment in southeast Australia has R36Cl values of 32 to 67 that are generally higher than those of modern rainfall (R36Cl = 25 to 35) but similar to shallow (
Characteristics of fine particle matters at the top of Shanghai Tower
Authors: Changqin Yin , Jianming Xu , Wei Gao , Liang Pan , Yixuan Gu , Qingyan Fu , Fan Yang
Published: March 2024

To investigate the physical and chemical processes of fine particle matters at mid-upper planetary boundary layer (PBL), we conducted one-year continuous measurements of fine particle matters (PM), chemical composition of non-refractory submicron aerosol (NR-PM1) and some gas species (including sulfur dioxide, nitrogen oxides and ozone) at an opening observatory (~600 m) at the top of Shanghai Tower (SHT), which is the Chinese 1st and World’s 2nd highest building located in the typical financial central business district of Shanghai, China. This is the first report for the characteristics of fine particles based on continuous and sophisticated online measurements at the mid-upper level of urban PBL. The observed PM2.5 and PM1 mass concentrations at SHT were 25.5±17.7 and 17.3±11.7 μg m-3 respectively. Organics, nitrate (NO3) and sulfate (SO4) occupied the first three leading contributions to NR-PM1 at SHT, accounting for 35.8 %, 28.6 % and 20.8 % respectively. The lower PM2.5 concentration was observed at SHT by 16.4 % compared with that near surface during the observation period. It was attributed to the decreased nighttime PM2.5 concentrations (29.4 % lower than surface) at SHT in all seasons due to the complete isolations from both emissions and gas precursors near surface. However, daytime PM2.5 concentrations at SHT were 12.4-35.1 % higher than those near surface from June to October, resulted from unexpected larger PM2.5 levels during early to middle afternoon at SHT than surface. We suppose the significant chemical production of secondary aerosols existed in mid-upper PBL because strong solar irradiance, adequate gas precursors (e.g., NOx) and lower temperature were observed at SHT favorable for both photochemical production and gas-to-particle partitioning. This was further demonstrated by the significant increasing rate of oxygenated organic aerosols and NO3 observed at SHT during 8:00-12:00 in spring (7.4 % h-1 and 12.9 % h-1), autumn (9.3 % h-1 and 9.1 % h-1) and summer (13.0 % h-1 and 11.4 % h-1), which cannot be fully explained by vertical mixing. It was noting that extremely high NO3 was observed at SHT both in daytime and nighttime in winter, accounting for 37.2 % in NR-PM1, suggesting the efficient pathway from heterogeneous and gas oxidated formation. Therefore, we highlight the priority of NOx reduction in Shanghai for the further improvement of air quality. This study reported greater daytime PM2.5 concentrations at the height of 600 m in urban PBL compared with surface measurement, providing insight into their potential effects on local air quality, radiation forcing, and cloud/fog formations. We propose that the efficient production of secondary aerosol in mid-upper PBL should be cognized and explored more comprehensively by synergetic observations in future.
Advancing Integrated Water Vapor Estimation: Introducing an Enhanced Regional Prediction Model Utilizing Improved Least Squares Support Vector Machine for the Upper Rhine Graben Region
Authors: Wang Lingke , Kutterer Hansjörg
Published: March 2024

Integrated Water Vapor (IWV) stands as a pivotal parameter in contemporary environmental research, offering crucial insights into atmospheric dynamics. Due to the inherent challenges in direct measurement, IWV necessitates estimation through various methods. Current approaches, including Global Navigation Satellite System (GNSS), radiosondes, radiometers, and satellite remote sensing, have inherent limitations, resulting in a scarcity of high spatial resolution data. While GNSS technology, radiosondes, and radiometers provide precision, they are confined to specific locations, imposing spatial coverage constraints. On the other hand, satellite remote sensing offers expansive, high spatial resolution IWV data, yet its accuracy is hindered under cloudy conditions and limited by satellite ground tracks.This study addresses these challenges by introducing a regional IWV prediction model based on Machine Learning. Leveraging IWV data from diverse GNSS stations within a specified region, the study establishes a regional IWV prediction model utilizing an adaptive least squares support vector machine (ALSSVM). This predictive model enables accurate IWV estimation at any designated location within the region, incorporating inputs such as latitude, longitude, height, and temperature. Significantly, the model attains remarkable predictive accuracy, with an overall average root mean square error (RMSE) of 2 millimeters.The model's performance exhibits variability across different seasons and terrains, illustrating its adaptability to diverse environmental conditions. The study further evaluates the reliability of the conventional ERA5 IWV calculation method in the specified region by comparing it against the predicted results from the proposed IWV prediction model. In conclusion, the developed model is applied to conduct a climate analysis, demonstrating its practical utility in environmental research for the transnational Upper Rhine Graben region.Keywords:Global Navigation Satellite System (GNSS), Integrated Water Vapor (IWV), least squares support vector machine (LSSVM), Climate Analysis
Adhesion forces measured between colloids and nanoscale surface roughness in aqueous solution
Authors: Hwang Gukhwa , Kim Hyunjung
Published: March 2024

The importance of nanoscale roughness factors on the fate and transport of colloidal particles has been well emphasized in recent literature; however, most of the works either only used modeling tools or had limitations on unravelling the effect experimentally due to the lack of well-defined systems to solely capture the role of the nanoscale roughness. Therefore, this study aimed to “experimentally” observe the adhesion characteristics of environmental colloidal particles on a surface with nanoscale roughness (NR) factors (i.e., height and fraction) under environmentally relevant solution chemistry conditions. Prior to analyzing the effect of the NR, the solid surface was first fabricated. AFM was employed to confirm the adhesion force between the target material and the uniformly fabricated rough surface, which can influence the contact area. To the best of our knowledge, our study is the first to experimentally quantify the sole effect of the NR with well-controlled NR-surfaces via the adhesion force measurement in aqueous system. The findings are important to verify the role of NR in the interaction of particles with different shapes (i.e., sphere and plateau) and sizes (i.e., 2 μm to 15 μm in length or diameter), which the authors believe will provide new insights to the society on better understanding the role of NR in the interaction of environmental colloidal particles.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2022-00166099).
Atmospheric boundary layer sensing using ultra-wideband photonic microwave spectrometer
Authors: Ogut Mehmet , Brown Shannon , Misra Sidharth , Kittlaus Eric , Kangaslahti Pekka , Murakowski Janusz , Gehl Michael
Published: March 2024

The Atmospheric Boundary Layer (ABL) is the portion of the troposphere that is directly influenced by the Earth’s surface and responds to combined action of mechanical and thermal forcing. Most of the energy exchange with respect to solar heating and evaporation that drive the atmosphere and the ocean occur within the ABL, yet it is one of the most poorly observed and modeled regions of the atmosphere. Conventional passive microwave systems fall well short of being optimized for near surface sensing due to limited number of spectral channels and coarse spectral resolution covering only a small portion of the spectrum of interest for ABL sensing. The so called “window regions” of the microwave spectrum between and on the shoulders of the strong oxygen and water vapor absorption lines carry the information on the near surface thermodynamic structure in the boundary layer. Sampling these regions requires new spectrometers capable of resolving >50 GHz spectral regions at modest spectral resolution (~1GHz). The ultra-wideband photonic spectro-radiometer instrument is funded by NASA ESTO under ACT-20 program to combine low-noise wideband RF technology with a novel photonic integrated circuit (PIC) design for obtaining large bandwidth (>50 GHz) with enhanced channel resolution (