scholarly journals Super Sites for Advancing Understanding of the Oceanic and Atmospheric Boundary Layers

2021 ◽  
Vol 55 (3) ◽  
pp. 144-145
Author(s):  
Carol Anne Clayson ◽  
Luca Centurioni ◽  
Meghan F. Cronin ◽  
James Edson ◽  
Sarah Gille ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Autonomous Vehicles ◽  
Large Scale ◽  
Coupled System ◽  
Atmospheric Boundary Layers ◽  
Remote Sensors ◽  
Floating Platforms ◽  
Atmospheric Heat

Abstract Air‐sea interactions are critical to large-scale weather and climate predictions because of the ocean's ability to absorb excess atmospheric heat and carbon and regulate exchanges of momentum, water vapor, and other greenhouse gases. These exchanges are controlled by molecular, turbulent, and wave-driven processes in the atmospheric and oceanic boundary layers. Improved understanding and representation of these processes in models are key for increasing Earth system prediction skill, particularly for subseasonal to decadal time scales. Our understanding and ability to model these processes within this coupled system is presently inadequate due in large part to a lack of data: contemporaneous long-term observations from the top of the marine atmospheric boundary layer (MABL) to the base of the oceanic mixing layer.We propose the concept of “Super Sites” to provide multi-year suites of measurements at specific locations to simultaneously characterize physical and biogeochemical processes within the coupled boundary layers at high spatial and temporal resolution. Measurements will be made from floating platforms, buoys, towers, and autonomous vehicles, utilizing both in-situ and remote sensors. The engineering challenges and level of coordination, integration, and interoperability required to develop these coupled ocean‐atmosphere Super Sites place them in an “Ocean Shot” class.

scholarly journals Global soil moisture data derived through machine learning trained with in-situ measurements

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Sungmin O. ◽  
Rene Orth
Keyword(s):  
Machine Learning ◽  
Soil Moisture ◽  
Large Scale ◽  
Short Term Memory ◽  
Temporal Dynamics ◽  
Soil Moisture Data ◽  
Wide Range ◽  
Global Soil

AbstractWhile soil moisture information is essential for a wide range of hydrologic and climate applications, spatially-continuous soil moisture data is only available from satellite observations or model simulations. Here we present a global, long-term dataset of soil moisture derived through machine learning trained with in-situ measurements, SoMo.ml. We train a Long Short-Term Memory (LSTM) model to extrapolate daily soil moisture dynamics in space and in time, based on in-situ data collected from more than 1,000 stations across the globe. SoMo.ml provides multi-layer soil moisture data (0–10 cm, 10–30 cm, and 30–50 cm) at 0.25° spatial and daily temporal resolution over the period 2000–2019. The performance of the resulting dataset is evaluated through cross validation and inter-comparison with existing soil moisture datasets. SoMo.ml performs especially well in terms of temporal dynamics, making it particularly useful for applications requiring time-varying soil moisture, such as anomaly detection and memory analyses. SoMo.ml complements the existing suite of modelled and satellite-based datasets given its distinct derivation, to support large-scale hydrological, meteorological, and ecological analyses.

In Situ Tests on Creep Behavior of Rock Mass with Joint or Shearing Zone in Foundation of Large-Scale Hydroelectric Projects

2004 ◽  
Vol 261-263 ◽  
pp. 1097-1102 ◽  
Author(s):  
Jian Liu ◽  
Xia Ting Feng ◽  
Xiu Li Ding ◽  
Huo Ming Zhou
Keyword(s):  
Rock Mass ◽  
Creep Behavior ◽  
Large Scale ◽  
Time Dependent ◽  
Three Gorges Project ◽  
Three Gorges ◽  
The Three Gorges ◽  
The Three Gorges Project

The time-dependent behavior of rock mass, which is generally governed by joints and shearing zones, is of great significance for engineering design and prediction of long-term deformation and stability. In situ creep test is a more effective method than laboratory test in characterizing the creep behavior of rock mass with joint or shearing zone due to the complexity of field conditions. A series of in situ creep tests on granite with joint at the shiplock area of the Three-Gorges Project and basalt with shearing zone at the right abutment of the Xiluodu Project were performed in this study. Based on the test results, the stress-displacement-time responses of the joints and basalt are analyzed, and their time-dependent constitutive model and model coefficients are given, which is crucial for the design to prevent the creep deformations of rock masses from causing the failure of the operation of the shiplock gate at the Three-Gorges Project and long-term stability of the Xiluodu arc dam.

scholarly journals Evaluating Machine Learning and Geostatistical Methods for Spatial Gap-filling of Monthly ESA CCI Soil Moisture in China

2021 ◽  
Vol 13 (14) ◽  
pp. 2848
Author(s):  
Hao Sun ◽  
Qian Xu
Keyword(s):  
Machine Learning ◽  
Soil Moisture ◽  
Water Resource Management ◽  
Large Scale ◽  
Gap Filling ◽  
Spatial Continuity ◽  
Study Results ◽  
Data Gaps

Obtaining large-scale, long-term, and spatial continuous soil moisture (SM) data is crucial for climate change, hydrology, and water resource management, etc. ESA CCI SM is such a large-scale and long-term SM (longer than 40 years until now). However, there exist data gaps, especially for the area of China, due to the limitations in remote sensing of SM such as complex topography, human-induced radio frequency interference (RFI), and vegetation disturbances, etc. The data gaps make the CCI SM data cannot achieve spatial continuity, which entails the study of gap-filling methods. In order to develop suitable methods to fill the gaps of CCI SM in the whole area of China, we compared typical Machine Learning (ML) methods, including Random Forest method (RF), Feedforward Neural Network method (FNN), and Generalized Linear Model (GLM) with a geostatistical method, i.e., Ordinary Kriging (OK) in this study. More than 30 years of passive–active combined CCI SM from 1982 to 2018 and other biophysical variables such as Normalized Difference Vegetation Index (NDVI), precipitation, air temperature, Digital Elevation Model (DEM), soil type, and in situ SM from International Soil Moisture Network (ISMN) were utilized in this study. Results indicated that: 1) the data gap of CCI SM is frequent in China, which is found not only in cold seasons and areas but also in warm seasons and areas. The ratio of gap pixel numbers to the whole pixel numbers can be greater than 80%, and its average is around 40%. 2) ML methods can fill the gaps of CCI SM all up. Among the ML methods, RF had the best performance in fitting the relationship between CCI SM and biophysical variables. 3) Over simulated gap areas, RF had a comparable performance with OK, and they outperformed the FNN and GLM methods greatly. 4) Over in situ SM networks, RF achieved better performance than the OK method. 5) We also explored various strategies for gap-filling CCI SM. Results demonstrated that the strategy of constructing a monthly model with one RF for simulating monthly average SM and another RF for simulating monthly SM disturbance achieved the best performance. Such strategy combining with the ML method such as the RF is suggested in this study for filling the gaps of CCI SM in China.

scholarly journals ENVIRONMENTAL POLLUTION BY WASTEWATER FROM BROWN COAL PROCESSING ¬ A REMEDIATION CASE STUDY IN GERMANY

2014 ◽  
Vol 22 (1) ◽  
pp. 71-83 ◽  
Author(s):  
Arndt Wiessner ◽  
Jochen A. Müller ◽  
Peter Kuschk ◽  
Uwe Kappelmeyer ◽  
Matthias Kästner ◽  
...  
Keyword(s):  
Environmental Pollution ◽  
Large Scale ◽  
Pilot Scale ◽  
Wastewater Disposal ◽  
Interdisciplinary Approaches ◽  
Phenolic Wastewater ◽  
Term Monitoring

The large scale of the contamination by the former carbo-chemical industry in Germany requires new and often interdisciplinary approaches for performing an economically sustainable remediation. For example, a highly toxic and dark-colored phenolic wastewater from a lignite pyrolysis factory was filled into a former open-cast pit, forming a large wastewater disposal pond. This caused an extensive environmental pollution, calling for an ecologically and economically acceptable strategy for remediation. Laboratory-scale investigations and pilot-scale tests were carried out. The result was the development of a strategy for an implementation of full-scale enhanced in situ natural attenuation on the basis of separate habitats in a meromictic pond. Long-term monitoring of the chemical and biological dynamics of the pond demonstrates the metamorphosis of a former highly polluted industrial waste deposition into a nature-integrated ecosystem with reduced danger for the environment, and confirmed the strategy for the chosen remediation management.

scholarly journals The decline and conservation management of the threatened endemic palms of the Mascarene Islands

Oryx ◽  
2002 ◽  
Vol 36 (1) ◽  
pp. 56-65 ◽  
Author(s):  
Mike Maunder ◽  
Wayne Page ◽  
John Mauremootoo ◽  
Richard Payendee ◽  
Yousoof Mungroo ◽  
...  
Keyword(s):  
Large Scale ◽  
Conservation Management ◽  
Conservation Status ◽  
Iucn Red List ◽  
Ex Situ ◽  
Population Fragmentation ◽  
Wild Populations ◽  
Mascarene Islands

Abstract The conservation status of the five genera and 11 species of palm endemic to the Mascarene Islands (Mauritius, La Réunion and Rodriques) are reviewed. All species are threatened with extinction; nine taxa are classified as Critically Endangered and four as Endangered on the 2000 IUCN Red List. Two taxa survive as single wild specimens (Hyophorbe amaricaulis and Dictyosperma album var. conjugatum); an additional seven taxa have wild populations of 100 or fewer. Although the historical phase of large-scale forest clearance has passed, the remaining palm populations in the Mascarenes are under threat from the effects of population fragmentation, invasive plants and animals, and high levels of seed predation that prevent natural regeneration. The advantages of in situ management for the recovery of these palm populations are discussed. Without a long-term conservation programme, utilising both in situ and ex situ management, extinction of wild populations will occur.

Dynamics of Bottom Boundary Layers in the Yellow River Subaqueous Delta Based on Long-Term In-Situ Observations

2017 ◽  
Vol 91 (1) ◽  
pp. 369-370 ◽  
Author(s):  
Chaoqi ZHU ◽  
Yonggang JIA ◽  
Zhenhao WANG ◽  
Lei GUO ◽  
Hongxian SHAN ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Yellow River ◽  
The Yellow River ◽  
Bottom Boundary ◽  
Bottom Boundary Layers ◽  
In Situ Observations

scholarly journals Thermal–hydraulic–mechanical (THM) behaviour of a large-scale in situ heating experiment during cooling and dismantling

2012 ◽  
Vol 49 (10) ◽  
pp. 1169-1195 ◽  
Author(s):  
M. Sánchez ◽  
A. Gens ◽  
L. Guimarães
Keyword(s):  
Large Scale ◽  
Element Formulation ◽  
Model Predictions ◽  
Engineered Barriers ◽  
Heating Test ◽  
High Level ◽  
Fully Coupled ◽  
Clay Barrier

A geological disposal facility for high-level radioactive waste (HLW) encompasses both natural (host rock) and (generally clay-based) engineered barriers. Many processes can influence, either positively or negatively, the effectiveness of the safety functions of isolation and retardation. This paper focuses on the analysis of a large-scale heating test when subjected to cooling and subsequent partial dismantling. The experiment reproduces the conditions of an HLW repository at full scale under realistic conditions. Key thermal, hydraulic, and mechanical (THM) variables, such as temperature, relative humidity, stresses, and fluid pressures, were measured in the clay barrier and surrounding rock. The experimental observations recorded during the cooling down and clay barrier excavation are analyzed in light of a fully coupled THM finite element formulation. This analysis has provided the opportunity to explore the behaviour of the clay and natural barriers under conditions very relevant for the repository performance but not analyzed previously. Overall, the model predictions are quite satisfactory when compared against experimental observations. Furthermore, model predictions for a period of 20 years, including the transient phase induced by the partial dismantling, are also presented. This additional analysis has allowed a better understanding of the effect of thermal gradient on long-term clay hydration.

scholarly journals Use of expanding polyurethane resin to remediate expansive soil foundations

2010 ◽  
Vol 47 (6) ◽  
pp. 623-634 ◽  
Author(s):  
Olivier Buzzi ◽  
Stephen Fityus ◽  
Scott W. Sloan
Keyword(s):  
Large Scale ◽  
Composite Resin ◽  
Expansive Soil ◽  
Soil Mass ◽  
Clay Material ◽  
Polyurethane Resin ◽  
Long Term Performance ◽  
Term Performance

Injection of expansive polyurethane resin can be used to remediate differential settlement issues. The resin is injected incrementally under a structure to achieve a desired foundation level, forming a composite resin–clay material. This solution is not well documented in the literature and some questions arise on the long-term performance of this solution. As injection is usually carried out in a settled soil mass that is dry and dessicated, rehydration of the soil after injection may lead to swelling of the leveled foundation and overlifting of the structure. Experimental research undertaken to investigate this rehydration issue and determine if there is a risk of overlifting in the long term is presented here. In situ and laboratory testing was performed to investigate the most fundamental aspects of the problems. This included the in situ injection of resin, study of resin propagation in the soil mass, influence of resin on the hydraulic conductivity of the soil mass, and large-scale swelling tests. The results suggest that, even though the resin cannot prevent the rehydration of the soil mass, the risk of overlifting in the long term is limited.

scholarly journals Large-Eddy Simulations of Stratified Atmospheric Boundary Layers: Comparison of Different Subgrid Models

2020 ◽  
Author(s):  
Srinidhi N. Gadde ◽  
Anja Stieren ◽  
Richard J. A. M. Stevens
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Large Scale ◽  
Wind Farm ◽  
Research Area ◽  
Large Eddy Simulations ◽  
Turbulence Energy ◽  
Atmospheric Boundary Layers ◽  
Smagorinsky Model ◽  
Large Eddy

Abstract The development and assessment of subgrid-scale (SGS) models for large-eddy simulations of the atmospheric boundary layer is an active research area. In this study, we compare the performance of the classical Smagorinsky model, the Lagrangian-averaged scale-dependent (LASD) model, and the anisotropic minimum dissipation (AMD) model. The LASD model has been widely used in the literature for 15 years, while the AMD model was recently developed. Both the AMD and the LASD models allow three-dimensional variation of SGS coefficients and are therefore suitable to model heterogeneous flows over complex terrain or around a wind farm. We perform a one-to-one comparison of these SGS models for neutral, stable, and unstable atmospheric boundary layers. We find that the LASD and the AMD models capture the logarithmic velocity profile and the turbulence energy spectra better than the Smagorinsky model. In stable and unstable boundary-layer simulations, the AMD and LASD model results agree equally well with results from a high-resolution reference simulation. The performance analysis of the models reveals that the computational overhead of the AMD model and the LASD model compared to the Smagorinsky model is approximately 10% and 30% respectively. The LASD model has a higher computational and memory overhead because of the global filtering operations and Lagrangian tracking procedure, which can result in bottlenecks when the model is used in extensive simulations. These bottlenecks are absent in the AMD model, which makes it an attractive SGS model for large-scale simulations of turbulent boundary layers.

scholarly journals Spatiotemporal Evolution of Evapotranspiration in China after 1998

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3250
Author(s):  
Qi Guo ◽  
Jiening Liang ◽  
Xianjie Cao ◽  
Zhida Zhang ◽  
Lei Zhang
Keyword(s):  
Control Region ◽  
Large Scale ◽  
Water Cycle ◽  
East Asian Monsoon ◽  
Water Control ◽  
Energy Control ◽  
The Difference ◽  
Local Weather

Changes in water circulation and uneven distributions of water resources caused by global warming are prominent problems facing the world at present. It is important to understand the influencing factors, and evapotranspiration (ET) is a key parameter for measuring the water cycle. However, understanding of spatiotemporal changes in actual evapotranspiration and its mechanism is still limited by a lack of long-term and large-scale in situ datasets. Here, the evolution of evapotranspiration in typical East Asian monsoon areas in China from 1989 to 2005 was analyzed with global land ET synthesis products. Evapotranspiration in China showed evident interdecadal variations around 1998; it decreased before 1998 and subsequently increased, which is inversely related to global ET changes. We further divided China into water-control and energy-control regions to discuss the factors influencing ET changes in each region. The interdecadal variations in increasing ET after 1998 in China were dominated by increasing potential evaporation in the energy-control region. An analysis using the empirical orthogonal function (EOF) method found that this occurred because ET is mainly manifested as decadal changes controlled by climate warming in the energy-control region and as interannual variations in the water-control region. The different feedbacks of ET on climate change in the two regions were also reflected in the difference in energy partition. The change in the Bowen rate (BR) did not increase climatic differences between energy- and water-control zones, but increases in the BR in arid summers significantly affected local weather and climate.

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