Development of a Building-Scale Meteorological Prediction System Including a Realistic Surface Heating

Numerical modeling of outdoor thermal comfort in 3D

Accurate inflow wind profiles are essential for computational fluid dynamics (CFD) simulations to calculate wind distributions in real urban environments. The Weather Research and Forecasting (WRF) model is widely used to provide realistic inflow wind profiles, as it captures atmospheric phenomena such as diurnal variations and sea breezes. However, WRF simulations are not sufficiently precise to predict wind profiles in built-up areas, due to the oversimplification of the complex urban morphology. Our previous study has proposed an analytical method combining WRF with a porosity model for accurately estimating urban wind profiles in the built-up areas. In this study, we further evaluated a multiscale modelling approach combining CFD simulations with inflow wind profiles estimated using the analytical method (analytical-inlet-CFD) for calculating pedestrian-level wind distributions. A public housing estate covering an area of 578 m × 560 m was selected as the target area, and field measurements were conducted at two sampling points, the landscape garden and the plaza, to collect pedestrian-level wind data in this real urban environment. The collected data then served as the benchmark for evaluating the accuracy of the analytical-inlet-CFD in outdoor wind simulations. For comparison, CFD simulations using inflow boundary conditions directly extracted from WRF (WRF-inlet-CFD) were also included. For both methods of setting the inflow boundary conditions of CFD simulations, wind profiles within the urban canopy were approximated using an exponential distribution. The results showed that analytical-inlet-CFD performed better than WRF-inlet-CFD in calculating pedestrian-level wind distributions in real urban environments.

Urban morphology plays a crucial role in affecting pedestrian level wind velocity and air temperature. Most studies use CFD to simulate these parameters, which requires substantial computational resources, detailed inputs, and modeller expertise. To assess the impact of urban morphology on these parameters, comparative analyses are often used but are highly dependent on pre-designed scenarios. The study established two XGBoost-based models to predict wind velocity and air temperature efficiently while applying SHAP to investigate the effect of urban morphology. SHAP results revealed that the horizontal and vertical distances from the array centre showed a greater influence on microclimate parameters than conventional building design variables. This study introduces efficient machine learning models predicting pedestrian-level wind and thermal environment with high temporal granularity while providing quantifiable insights into the relationships between urban morphology variables and microclimate conditions through SHAP-based analysis, offering practical design optimization support for creating more comfortable urban environments.

In multiple input multiple output (MIMO) systems the antenna array configuration in the base station (BS) and mobile station (MS) has a large influence on the available channel capacity. In this paper, we first introduce a new frequency selective (FS) MIMO framework for macro-cells in a realistic urban environment. Next, MIMO configuration characteristics are investigated in order to maximize capacity, mainly the number of antennas and inter-antenna spacing. Channel and capacity simulation results are presented for the city of Lisbon, Portugal, using different antenna configurations. Two power allocations schemes are considered, uniform distribution and FS spatial water-filling. The results suggest optimized MIMO configurations, considering the antenna array size limitations, at the MS side.

In this paper, different exposure situations for a subject standing inside a room of a building with a window facing a rooftop-mounted base-station antenna are analyzed. The study is accomplished by using a technique combining the uniform asymptotic theory of diffraction and the finite-difference time-domain method, suitable to characterize human exposure in realistic urban environments at a reasonable computational cost. The different exposure conditions examined are analyzed to highlight the problems related to compliance assessment procedures in complex exposure scenarios and to suggest some possible solutions. A comparison of the results obtained in these scenarios with those computed neglecting the presence of the room walls (free-space situations) evidences that, under certain conditions, average exposure field levels and specific absorption rates (SARs) in the realistic environments can be higher than in free space, thus demonstrating that compliance assessment carried out in free space can yield nonconservative results. As concerns implications of field nonuniformities, typical of realistic urban environments, on SAR values, the results show that the whole-body averaged SAR is related to the average field value, provided the averaging procedure is appropriately chosen to cover all the volume occupied by the subject (V/sub S/) and not only a vertical surface. Local SAR values, instead, show a more complex relation with the exposure field, such that considering only the V/sub S/-averaged field value for compliance assessment might lead to an underestimation of the real exposure level, while using the peak of the field in V/sub S/ leads to a remarkable overestimation.

This paper describes in detail the applicability of the developed ground-penetrating radar (GPR) model with a kinematic GPR and self-tracking (robotic) terrestrial positioning system (TPS) surveying setup (GPR-TPS model) for the acquisition, processing and visualisation of underground utility infrastructure (UUI) in a real urban environment. The integration of GPR with TPS can significantly improve the accuracy of UUI positioning in a real urban environment by means of efficient control of GPR trajectories. Two areas in the urban part of Celje in Slovenia were chosen. The accuracy of the kinematic GPR-TPS model was analysed by comparing the three-dimensional (3D) position of UUI given as reference values (true 3D position) from the officially consolidated cadastre of utility infrastructure in the Republic of Slovenia and those obtained by the GPR-TPS method. To determine the reference 3D position of the GPR antenna and UUI, the same positional and height geodetic network was used. Small unmanned aerial vehicles (UAV) were used for recording to provide a better spatial display of the results of UUI obtained with the GPR-TPS method. As demonstrated by the results, the kinematic GPR-TPS model for data acquisition can achieve an accuracy of fewer than 15 centimetres in a real urban environment.

Sea breezes are often modeled as a wave response to transient heating in a stratified environment. They occur, however, as density currents with well-defined fronts, the understanding of which rests primarily on experiments and theory that do not include the stratification within and above the current and the steady heat input at the land surface. These gaps are investigated here via a sequence of idealized 2D density current simulations, progressing from the simplest classical case to more realistic surface heating and stratification.In the classical situation where the entire horizontal density contrast is imposed initially, the front quickly attains a constant speed determined by traditional formulas based on the density contrast across the front and the current depth, or by the amount of heat needed to produce it from an initially barotropic fluid. However, these diagnostic and prognostic tools fail completely if the current is driven by a gradual input of heat, analogous to a real sea-breeze situation. In this case the current accelerates slowly at first, remaining much slower than would be expected based on classical formulas.The motion of a classical density current is mostly inertial, with accelerations occurring at the current head; while in the continuously heated case, the entire current accelerates, requiring interior body forces to develop slowly owing to heating of the density current itself. This explains why observed sea-breeze fronts propagate more slowly than predicted from classical formulas, and may help to explain why larger landmasses, where fronts have more time to accelerate, often experience stronger convective storms when triggered by sea-breeze effects.

Observational records and climate model projections reveal a considerable decline in the Atlantic Meridional Overturning Circulation (AMOC). Changes in the AMOC can have a significant impact on the global climate. Sustained warming due to increased greenhouse gas emissions is projected to weaken the AMOC, which in turn can lead to changes in the location of Inter-tropical convergence zone (ITCZ), oceanic and atmospheric large-scale circulation, tropical precipitation and regional monsoons. Using proxy records, observations and CMIP6 simulations of IITM Earth System Model (IITM-ESM), we investigate the changes in the AMOC and associated changes in the large-scale circulation and precipitation patterns over the South Asian monsoon region. Transient CO2 simulation and additional model sensitivity experiments with realistic surface heat and freshwater perturbation anomalies under the experimental protocol of Flux Anomaly Forcing Model Intercomparison Project (FAFMIP) performed with IITM-ESM reveal a decline in the strength of AMOC. The weakening of AMOC is associated with enhanced heat and freshwater forcing in the North Atlantic resulting in the reduction of northward oceanic heat transport and an enhanced northward atmospheric heat transport. Changes in AMOC lead to weakening of large-scale north–south temperature gradient and regional land-sea thermal gradient, which in turn weaken the regional Hadley circulation and, monsoon circulation over the South Asian region. Both the FAFMIP and transient CO2 experiments reveal consistent results of weakening South Asian Monsoon circulation with a decline of AMOC, while precipitation exhibits contrasting responses as precipitation changes are dominated by the thermodynamic response. The suite of observational and numerical analysis provides a mechanistic hypothesis for the weakening of South Asian monsoon circulation concomitant with a weakening of AMOC in a warming climate.

Comparison of uniform and non-uniform surface heating effects on in-canyon airflow and ventilation by CFD simulations and scaled outdoor experiments

<p>This work is devoted to the development of a numerical model of the transport of aerosol particles in the atmospheric boundary layer, as well as its application in idealized cases and studies with a realistic urban surface. Air quality and the distribution of pollutants is one of the major urban problems, and measurement methods can be limited in the complex geometry of the city, which motivates the development of modeling methods.</p><p>The model uses the Lagrangian approach to modeling, taking into account the size and mass of each particle, the possibility of aerosol deposition and their collision with various surfaces. The particle motion equation takes into account various parameters of the atmosphere: wind direction and speed, turbulent characteristics. The influence of turbulence on the motion of aerosols can be taken into account in the model using several parametrizations – stochastic Lagrangian models of zero and first order. It is possible to simulate a huge number of particles at the same time. The algorithm is implemented in the C++ programming language.</p><p>The model can be used as a separate tool that requires information about the state of the atmosphere as input data - these can be measurement data, results of hydrodynamic modeling, analytically given values. Numerous experiments have been carried out in this mode. The model was verified on exact analytical solutions for light and heavy particles, on the data of field measurements of the concentrations of dust and sand particles. Calculations were carried out in conditions of idealized geometry of buildings (urban canyons) and in conditions of real urban development. For this, input data from RANS and LES models were used.</p><p>The developed algorithm can also be used as a module connected to hydrodynamic models. In this mode, it is possible to use the input data on atmospheric parameters with the maximum resolution in time and space. By connecting to the LES model, high-resolution simulations of aerosol transport in realistic urban environments were performed.</p><p>The work is supported by Russian Ministry of Science and Higher Education, agreement No. 075-15-2021-574 (megagrant leaded by M.Kulmala in Moscow State University, WP4), No. 075-15-2019-1621, by RSF grant 21-17-00249, by RFBR grants 20-05-00776 and 19-05-50110.</p>

A technique combining uniform asymptotic theory of diffraction and finite-difference time-domain (UTD/FDTD), suitable to characterize human exposure in realistic urban environments at a reasonable computational cost, is presented. The technique allows an accurate evaluation of field interaction with penetrable objects (walls, windows, furniture, etc.) and of power absorption in a high-resolution model of the exposed subject. The method has been applied to analyze the exposure of a subject standing behind a window in a building situated in front of a rooftop-mounted base-station antenna. A comparison of the obtained results with those computed neglecting the presence of the building (free-space condition) evidences that a realistic modeling of field propagation in the actual scenario is essential for an accurate evaluation of absorbed power distribution inside the human body.

Air pollution in urban environments exhibits large spatial and temporal variations due to high heterogeneous air flow and emissions. To address the complexity of local air pollutant dynamics, a comprehensive large-eddy simulation using the PALM model system v6.0 was conducted. The distribution of flow and vehicle emitted aerosol particles in a realistic urban environment in Malmö, Sweden, was studied and evaluated against on-site measurements made using portable instrumentation on a spring morning in 2021. The canyon transport mechanisms were investigated, and the convective and turbulent mass-transport rates compared to clarify their role in aerosol transport. The horizontal distribution of aerosols showed acceptable evaluation metrics for both mass and number. Flow and pollutant concentrations were more complex than those in idealized street canyon networks. Vertical turbulent mass-transport rate was found to dominate the mass transport process compared with the convective transport rate, contributing more than 70% of the pollutant transport process. Our findings highlight the necessity of examining various aerosol metric due their distinct dispersion behaviour. This study introduces a comprehensive high-resolution modelling framework that accounts for dynamic meteorological and aerosol background boundary conditions, real-time traffic emission, and detailed building features, offering a robust toll for local urban air quality assessment.

Understanding the characteristics of wind at pedestrian level is important to ensure pedestrian safety and comfort in urban environments. Pedestrian-level wind characteristics are mainly affected by the average characteristics of surrounding buildings such as plan and frontal area densities and mean building height, and the shape of each building also has a big impact on the wind characteristics. In particular, the various shapes of buildings, including curved surfaces, complicate the wind environment in urban areas. Currently, various computational fluid dynamics (CFD) models are being utilized to study the complex flows in urban areas. Many CFD models use cartesian grids to simulate flows in urban space by converting the urban space made up of buildings into a set of cuboids. The OpenFOAM (Open Field Operation And Manipulation) model, an open source CFD model, has the advantage of being able to represent the curved shape of building to the greatest extent possible by generating unstructured meshes using the mesh generation utility called snappyHexMesh.In this study, we simulate the campus space of University of Seoul located in Seoul, South Korea using structured (cartesian grid) and unstructured meshes for OpenFOAM simulations, and compare the results over the two meshes. To implement realistic flow conditions, a mesoscale weather model (WRF) are used as the initial and lateral boundary conditions. In this study, we analyze the differences in the generation of turbulent eddies specially around the curved building surfaces according to the two types of meshes and compare the simulation results with observations. We expect that using the unstructured mesh will allow us to more accurately simulate flow separation, wakes around buildings, and turbulence statistics at pedestrian level. This study can be used to identify detailed features of pedestrian-level wind (e.g., gustiness), thereby providing a basis for pedestrian environmental impact assessment.

We experimentally verify the effectiveness of metasurface reflectors in expanding 5G coverage into non-line-of sight (NLoS) regions in the 28-GHz frequency band. In outdoor open space measurements, the measured beam shape is well matched with that designed with an 18-degree beamwidth. Improvements in the beam-reference-signal received power (BRSRP) and downlink (DL) throughput of approximately 15 dB and 100%, respectively, are observed over a 35-m range in a NLoS area in a real urban environment. Consequently, the effectiveness of the metasurface reflectors in expanding 5G coverage into the NLoS region are experimentally verified in a real urban environment using a 5G testbed system.

Experimental evidence sheds new light on the role of spatial geometry for wayfinding in real urban environments. Eye-tracking is used in a desktop-based experiment to study where people look during wayfinding decisions when let to look freely or asked to find a taxi rank. Gaze patterns from these two tasks are compared with a subsequent recall task and analyzed in light of the topology of the street grid. Results show that decisions strongly favor more connected streets, and that fixation patterns respond to the spatial geometry of the stimuli in both the spatial decision-making and recall tasks. Controls single out the impacts of lighting and affordances in both the behavioral responses and gaze bias patterns; the presence of people and traffic serve as particularly strong attractors. The paper highlights the role of spatial geometry for individual spatial decision-making in real urban environments.