Modelling the arctic convective boundary-layer with different turbulence parameterizations

Different parameterizations of subgrid-scale fluxes are utilized in a nonhydrostatic and anelastic mesoscale model to study their influence on simulated Arctic cold air outbreaks. A local closure, a profile closure and two nonlocal closure schemes are applied, including an improved scheme, which is based on other nonlocal closures. It accounts for continuous subgrid-scale fluxes at the top of the surface layer and a continuous Prandtl number with respect to stratification. In the limit of neutral stratification the improved scheme gives eddy diffusivities similar to other parameterizations, whereas for strong unstable stratifications they become much larger and thus turbulent transports are more efficient. It is shown by comparison of model results with observations that the application of simple nonlocal closure schemes results in a more realistic simulation of a convective boundary layer than that of a local or a profile closure scheme. Improvements are due to the nonlocal formulation of the eddy diffusivities and to the inclusion of heat transport, which is independent of local gradients (countergradient transport).     

Undrained capacity of surface foundations with zero-tension interface under planar V-H-M loading

Undrained capacity of strip and circular surface foundations with a zero-tension interface on a deposit with varying degrees of strength heterogeneity is investigated by finite element analyses. The method for simulating the zero-tension interface numerically is validated. Failure envelopes for strip and circular surface foundations under undrained planar V-H-M loading are presented and compared with predictions from traditional bearing capacity theory. Similar capacity is predicted with both methods in V-H and V-M loading space while the traditional bearing capacity approach under-estimates the V-H-M capacity derived from the numerical analyses due to superposition of solutions for load inclination and eccentricity not adequately capturing the true soil response. An approximating expression is proposed to describe the shape of normalised V-H-M failure envelopes for strip and circular foundations with a zero-tension interface. The unifying expression enables implementation in an automated calculation tool resulting in essentially instantaneous generation of combined loading failure envelopes and optimisation of a foundation design as a function of foundation size or material factor. In contrast, the traditional bearing capacity theory approach or direct numerical analyses for a given scenario requires ad-hoc analyses covering a range of input variables in order to obtain the ‘best’ design.     

Three-dimensional topology optimization for geotechnical foundations in granular soil

This article presents three-dimensional structural optimization in geotechnical engineering for foundations in granular soil. The general design (topology) of a shallow foundation is optimized with respect to its deformational behaviour within the service limit state. The SIMP (solid isotropic material with penalization) method is applied to optimize the distribution of foundation material. The soil is modelled as a hypoplastic material with a constitutive model suitable for optimization using finite element analysis. Two load cases are examined. The optimized topology is validated against two-dimensional optimization and 1g-model test results. The present study proves the applicability and shows the potential of topology optimization in geotechnical engineering.     

Improving deep decarbonization modelling capacity for developed and developing country contexts

Energy models are essential for the development of national or regional deep decarbonization pathways (DDPs), providing the necessary analytical framework to systematically explore the system transitions that are required. However, this is challenging due to the long time horizon, the numerous data requirements and the need for transparent, credible approaches that can provide insights into complex transitions.

This article explores how this challenge has been met to date, based on a review of the literature and the experiences of practitioners, drawing in particular on the Deep Decarbonization Pathways Project (DDPP), a collaborative effort by 16 national modelling teams. The article finds that there are a range of modelling approaches that have been used across different country contexts, chosen for different reasons, with recognized strengths and weaknesses. The key motivations for use of a given approach include being fit-for-purpose, having in-country capacity and the intertwined goals of transparency, communicability and policy credibility.

From the review, a conceptual decision framework for DDP analysis is proposed. This three step process incorporates policy priorities, national characteristics and the model-agnostic principles that drive model choices, considering the needs and capabilities of developed and developing countries, and subject to data and analytical practicalities. Finally an agenda for the further development of modelling approaches is proposed, which is vital for strengthening capacity. These include a focus on model linking, incorporating behaviour and policy impacts, the flexibility to handle distinctive energy systems, incorporating wider environmental constraints and the development of entry-level tools. The latter three are critical for application in developing countries.

Policy relevance

Following the Paris Agreement, it is essential that modelling approaches are available to enable governments to plan how to decarbonize their economies in the long term. This article takes stock of current practices, identifies the strengths and weaknesses of existing approaches and proposes how capacity can be strengthened. It also provides some practical guidance on the process of choosing modelling approaches, given national priorities and circumstances. This is particularly relevant as countries revisit their Nationally Determined Contributions to meet the global objective of remaining well below a 2°C average global temperature increase.     

Method and analysis for the upscaling of structural data

3D geological models are created to integrate a set of input measurements into a single geological model. There are many problems with this approach, as there is uncertainty in all stages of the modelling process, from initial data collection to the approach used in the modelling scheme itself to calculate the geological model. This study looks at the uncertainty inherent in geological models due to data density and introduces a novel method to upscale geological data that optimises the information in the initial dataset. This method also provides the ability for the dominant trend of a geological dataset to be determined at different scales. By using self-organizing maps (SOM's) to examine the different metrics used to quantify a geological model, we allow for a larger range of metrics to be used compared to traditional statistical methods, due to the SOM's ability to deal with incomplete datasets. The classification of the models into clusters based on the geological metrics using k-means clustering provides a useful insight into the models that are most similar and models that are statistical outliers. Our approach is guided and can be calculated on any input dataset of this type to determine the effect that data density will have on a resultant model. These models are all statistical derivations that represent simplifications and different scales of the initial dataset and can be used to interrogate the scale of observations.     

Evolution of fluid flow and heat distribution over geological time scales at the margin of unconfined and confined carbonate sequences - A numerical investigation based on the Buda Thermal Karst analogue

Hydrogeological processes acting at the margins of confined and unconfined thick carbonate sequences are particularly interesting due to a complex system evolution including partial uplift of fully confined carbonate systems and subsequent erosion of cover layers. We provide insights into this evolution by simulating coupled density-dependent fluid flow and heat transport based on the Buda Thermal Karst (BTK) system (Hungary) in a 2D vertical plane. Applying an equivalent porous medium (EPM) approach using the Heatflow-Smoker finite element model, scenario modelling of three evolutionary steps was carried out between the fully-confined carbonate stage through to partly and completely unconfined conditions over the western ridge. The numerical simulations were used to derive the main evolutionary characteristics of groundwater flow and heat transport patterns for the unconfined and confined parts of the hydrogeologic system. The initial fully-confined state led to the development of thermal convection cells due to the insulating role of the low-permeability confining layer, which facilitates buoyancy-driven flow by restricting the dissipation of heat. Over geological time, these cells were gradually overprinted by gravity-driven flow and thermal advection due to uplift of the west ridge. The limited thickness of the cover allowed sufficient water infiltration into the system, which led to increased cooling. Further uplifting led to a prevalence of gravity-driven groundwater flow. The results highlight the critical role of confining formations on flow patterns, and their effect on heat distribution and dissipation over geological time scales. The results have important implications for heat accumulation as well as for the development of a deep geothermal energy potential in confined carbonates.     

A comparative assessment of catchment runoff generation and forest productivity in a semi-arid environment

Understanding the dynamic interactions between forest ecosystems and water in the Mediterranean region is essential for increasing ecosystem services. Even if many studies were implemented to analyse the variations of water and net primary productivity (NPP) in the last decade, this is still an important research question especially for the Eastern Mediterranean, where the research attempts are limited. The main objective of this study was to carry out a comparative analysis of catchment runoff generation and forest NPP and to reveal their temporal dynamics at basin scale in a semi-arid Mediterranean environment. The methodology consisted three steps: (i) estimating catchment runoff generation by implementing process-based J2000 modelling suite, (ii) modelling NPP of the land cover/use types by adapting an ecosystem-process model (BIOME-Biogeochemical cycles) and (iii) assessing the spatio-temporal variability of NPP and runoff dynamics by incorporating the modelling results with multiple regression analysis. Model simulations showed that temperature highly contributed to NPP variations of needle-leaf forests and grasslands. The multiple regression analysis also indicated that runoff was influenced by elevation, precipitation and forest cover. This relationship showed that the inter-annual variability in forest NPP would relate to the variations in runoff distribution across a small Mediterranean subcatchment.     

Automatic near-photorealistic 3-D modelling and texture mapping for rectilinear buildings

Three-dimensional (3-D) representations of urban regions have gained much attention because of recent developments in remote sensing and computer graphics technologies. In particular, textured 3-D building reconstruction for a variety of applications has been a popular research topic in recent years. In this study, we present the reconstruction of 3-D building models along with texture selection and mapping. Extracted two-dimensional building patches and normalized digital surface model (nDSM) data are used to generate the 3-D models. To build near-photorealistic 3-D models, the acquired geo-referenced facade textures are associated with the corresponding building facades using an automated GPS-assisted approach. On the other hand, the modelling and texture mapping of the roof structures were carried out manually. The study area is composed of eight housing estates (blocks), where a total of 110 buildings were analysed. The whole study area was modelled, with facade textures, in less than 1 min of processor running time with an acceptable level of accuracy. The texture mapping was carried out using MATLAB’s Virtual Reality Toolbox?.     

相机内参数标定的评价指标研究与实验

相机内参数的标定受标定环境、标定物规格、标定相片数量等诸多难以进行理论分析的因素影响,导致在实际工程应用中,相机内参数标定的评估存在精度不确定性问题。基于数学统计量设计了相机内参数标定精度评估指标,针对标定相片数量和标定物距对相机标定精度的影响进行研究,并对两种典型相机——工业相机和数码相机,进行内参数标定实测试验及分析。结果表明,当标定参数值达到收敛时,相片收敛数量与标定物距成正比关系;与像主点标定相比,焦距的标定收敛效率更高,达到收敛所需的相片数量更少,但随着标定物距增大,两者的差异逐渐缩小。内参数标定精度的评估指标为相机内标定算法的改进及操作流程提供评估手段,为实际标定工作提供参考和借鉴。     

Rainfall-runoff modelling by using SM2RAIN-derived and state-of-the-art satellite rainfall products over Italy

Satellite rainfall products (SRPs) are becoming more accurate with ever increasing spatial and temporal resolution. This evolution can be beneficial for hydrological applications, providing new sources of information and allowing to drive models in ungauged areas. Despite the large availability of rainfall satellite data, their use in rainfall-runoff modelling is still very scarce, most likely due to measurement issues (bias, accuracy) and the hydrological community acceptability of satellite products.In this study, the real-time version (3B42-RT) of Tropical Rainfall Measurement Mission Multi-satellite Precipitation Analysis, TMPA, and a new SRP based on the application of SM2RAIN algorithm (Brocca et al., 2014) to the ASCAT (Advanced SCATterometer) soil moisture product, SM2R_ASC, are used to drive a lumped hydrologic model over four basins in Italy during the 4-year period 2010–2013.The need of the recalibration of model parameter values for each SRP is highlighted, being an important precondition for their suitable use in flood modelling. Results shows that SRPs provided, in most of the cases, performance scores only slightly lower than those obtained by using observed data with a reduction of Nash–Sutcliffe efficiency (NS) less than 30% when using SM2R_ASC product while TMPA is characterized by a significant deterioration during the validation period 2012–2013. Moreover, the integration between observed and satellite rainfall data is investigated as well. Interestingly, the simple integration procedure here applied allows obtaining more accurate rainfall input datasets with respect to the use of ground observations only, for 3 out 4 basins. Indeed, discharge simulations improve when ground rainfall observations and SM2R_ASC product are integrated, with an increase of NS between 2 and 42% for the 3 basins in Central and Northern Italy. Overall, the study highlights the feasibility of using SRPs in hydrological applications over the Mediterranean region with benefits in discharge simulations also in well gauged areas.