scholarly journals A Study on Estimation of Inflow Wind Speeds in a CFD Model Domain for an Urban Area

Atmosphere ◽  
2017 ◽  
Vol 27 (1) ◽  
pp. 67-77 ◽  
Author(s):  
Geon Kang ◽  
Jae-Jin Kim
Keyword(s):  
Urban Area ◽  
Cfd Model ◽  
Wind Speeds ◽  
Model Domain

scholarly journals Prediction of Near-Surface Variables at Independent Locations from a Bias-Corrected Ensemble Forecasting System

2006 ◽  
Vol 134 (11) ◽  
pp. 3415-3424 ◽  
Author(s):  
Nusrat Yussouf ◽  
David J. Stensrud
Keyword(s):  
New England ◽  
Near Surface ◽  
Wind Speeds ◽  
Dewpoint Temperature ◽  
Model Domain ◽  
Oklahoma Mesonet ◽  
Independent Observations ◽  
Forecasting System ◽  
Surface Station ◽  
Forecast Time

Abstract The ability of a multimodel short-range bias-corrected ensemble (BCE) forecasting system, created as part of NOAA’s New England High Resolution Temperature Program during the summer of 2004, to obtain accurate predictions of near-surface variables at independent locations within the model domain is explored. The original BCE approach produces bias-corrected forecasts only at National Weather Service (NWS) observing surface station locations. To extend this approach to obtain bias-corrected forecasts at any given location, an extended BCE technique is developed and applied to the independent observations provided by the Oklahoma Mesonet. First, a Cressman weighting scheme is used to interpolate the bias values of 2-m temperature, 2-m dewpoint temperature, and 10-m wind speeds calculated from the original BCE approach at the NWS observation station locations to the Oklahoma Mesonet locations. These bias values are then added to the raw numerical model forecasts bilinearly interpolated to this same specified location. This process is done for each forecast member within the ensemble and at each forecast time. It is found that the performance of the extended BCE is very competitive with the original BCE approach across the state of Oklahoma. Therefore, a simple postprocessing scheme like the extended BCE system can be used as part of an operational forecasting system to provide reasonably accurate predictions of near-surface variables at any location within the model domain.

Estimation of Wind Speeds in Urban Areas Using Look-up Tables for Wind-speed Change Rate Simulated by a CFD Model

2020 ◽  
Author(s):  
Jang-Woon Wang ◽  
Jae-Jin Kim ◽  
Ho-Jin Yang
Keyword(s):  
Wind Speed ◽  
Urban Areas ◽  
Urban Morphology ◽  
Average Height ◽  
Target Area ◽  
Cfd Model ◽  
Parameterization Method ◽  
Wind Speeds ◽  
Speed Change ◽  
Morphology Parameters

<p>In this study, we developed a new urban parameterization method of wind speeds. The parameterization method uses building morphology parameters (the volumetric fraction, the plane area fraction, and the average height of buildings) for three different areas. For this, we investigated the relationships between the wind speed change rates by buildings and the urban parameters in three target areas. Each target area includes an automated weather station (AWS) at its center. We conducted the multiple regression analysis to make look-up tables for the relationships between the wind speed change rates and the urban morphology parameters for 32 inflow directions in the target areas. For validation, we simulated the wind speeds at the AWSs using a CFD model coupled to the local data assimilation and prediction system (LDAPS), one of the operational numerical prediction systems of the Korean Meteorological Administration. The results showed that the estimated wind speeds at the AWSs in the three target areas were very similar to those simulated by the LDAPS-CFD coupled model as well as those observed at the AWSs.</p>

Effects of Trees on Pedestrian Wind Comfort in an Urban Area Using a CFD model

2020 ◽  
Author(s):  
Geon Kang ◽  
Jae-Jin Kim
Keyword(s):  
Prediction Models ◽  
Weather Prediction ◽  
Successful Implementation ◽  
Cfd Model ◽  
Local Data ◽  
Wind Speeds ◽  
National University ◽  
Computational Fluid Dynamics Cfd ◽  
Wind Comfort ◽  
Comfort Criteria

<p>This study investigated the effects of trees on the pedestrian wind comfort in the Pukyong National University (PKNU) campus. For this, we implemented the tree’s drag parameterization scheme to a computational fluid dynamics (CFD) model and validated the simulated results against a field measurement. The CFD model well reproduced the measured wind speeds and TKEs in the downwind region of the trees, indicating successful implementation of the tree drag parameterization schemes. Besides, we compared the wind speeds, wind directions, and temperatures simulated by the CFD model coupled to the local data assimilation and prediction system (LDAPS), one of the numerical weather prediction models operated by the Korean Meteorological Administration (KMA) to those observed at the automated weather station (AWS). We performed the simulations for one week (00 UTC 2 – 23 UTC 9 August 2015). The LDAPS overestimated the observed wind speeds (RMSE = 1.81 m s<sup>–1</sup>), and the CFD model markedly improved the wind speed RMSE (1.16 m s<sup>–1</sup>). We applied the CFD model to the simulations of the trees' effects on pedestrian wind comfort in the PKNU campus in views of wind comfort criteria based on the Beaufort wind force scale (BWS). We will present the trees' effects on pedestrian wind comfort in the PKNU campus in detail.</p>

scholarly journals Variabilidad temporal de la isla de calor urbana de la ciudad de Zaragoza (España)

2021 ◽  
Author(s):  
José M. Cuadrat ◽  
Roberto Serrano-Notivoli ◽  
Samuel Barrao ◽  
Miguel Ángel Saz ◽  
Ernesto Tejedor
Keyword(s):  
Urban Heat Island ◽  
Urban Area ◽  
City Centre ◽  
Heat Island ◽  
Time Data ◽  
Wind Speeds ◽  
Urban Heat ◽  
The City ◽  
Temporal Intensity

We analyse the temporal intensity and variability of the urban heat island (UHI) in the city of Zaragoza (Spain), and assess the role of wind as an important atmospheric conditioning factor. Based on the time data provided by the city’s urban mesoscale meteorological network, the temperature difference between two observatories, one urban (Plaza Santa Marta) and one located on the outskirts of the urban area (Ciudad Deportiva), was calculated for the 2015-2020 period. The results indicate that the temperature in the city centre is very frequently 1º or 2ºC higher than in the surroundings, sometimes even more than 8ºC higher. The UHI is more intense in summer (an average of 2.5ºC per hour) than in winter (an average of 2.2ºC per hour) and more intense during the night than during the day. The maximum UHI value is reached in calm atmospheric situations; however, this value is very limited with winds over 10 km/h and it practically disappears with wind speeds over 50 km/h.

scholarly journals Influence of a Great Plains Urban Environment on a Simulated Supercell

2018 ◽  
Vol 146 (5) ◽  
pp. 1437-1462 ◽  
Author(s):  
Larissa J. Reames ◽  
David J. Stensrud
Keyword(s):  
Land Use ◽  
Urban Area ◽  
Great Plains ◽  
Urban Areas ◽  
City Center ◽  
Land Use Pattern ◽  
Near Surface ◽  
Wind Speeds ◽  
The North ◽  
The City

Abstract The effect of urban areas on weakly forced precipitation systems has been studied extensively. However, interactions between urban areas and strongly forced convection, such as supercells, remain relatively unexamined. The present study uses simulations of a supercell to quantify the impacts of a large plains urban area on the evolution and strength of a supercell. An initial ensemble of simulations (CTRLE) of a supercell over homogeneous land use is performed using the WRF-ARW Model. Additionally, 108 simulations are conducted in which the land-use pattern of Dallas–Ft. Worth, Texas, is placed inside the model domain, with the city center shifted to be in or near the path of the supercell. Simulations with urban areas are compared to CTRLE, with the aid of hierarchical clustering analysis to form statistically similar groups of simulations. Clustering analyses identify groups of ensemble members with closely located urban areas that have similar patterns of 0–1-km updraft helicity and near-surface minimum temperature and maximum wind speeds. Comparison of these groups of ensemble members to CTRLE suggests the urban area has a significant impact on storm characteristics, particularly on low-level rotation and mesocyclone track. Simulations where the storm passes to the north of or directly over the city center late in its life cycle deviate most significantly from CTRLE. In these members, low-and midlevel mesocyclone strength increases, and the mesocyclone tracks farther south when compared to CTRLE.

scholarly journals Remote sensing of atmospheric nitrogen dioxide in an urban area in central northern Mexico

2021 ◽  
Author(s):  
Julio César Hernández ◽  
Clara Rosalía Ávila ◽  
Luis Felipe Lastras ◽  
Alfonso Lastras ◽  
David Enrique Flores ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Urban Area ◽  
Meteorological Data ◽  
Ground Level ◽  
Optical Absorption Spectroscopy ◽  
Weather Research And Forecasting ◽  
Atmospheric Nitrogen ◽  
Northern Mexico ◽  
Wind Speeds ◽  
Measurement Period

Nitrogen dioxide (NO2) was remotely measured in the urban area of San Luis Potosí (México) using the differential optical absorption spectroscopy (DOAS) technique. Measurements were taken from July to August 2015. In this technique, light scattered by the sun through the atmosphere is focused by a telescope onto a linear array-based spectrometer at ground level. During the measurement period, the maximum NO2 levels (2.3 x 1016 molecules/cm2) were found at around 11:00 h, whereas NO2 levels fell on days with wind speeds lower than 1.5 m/s. The NO2 levels were compared and explained with the behavior of meteorological data such as wind speed, relative humidity, and surface temperature obtained from the Weather Research and Forecasting Model (WRF).

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

Atmosphere ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 67 ◽  
Author(s):  
Dong-Jin Kim ◽  
Doo-Il Lee ◽  
Jae-Jin Kim ◽  
Moon-Soo Park ◽  
Sang-Hyun Lee
Keyword(s):  
Urban Area ◽  
Urban Morphology ◽  
Urban Environments ◽  
Surface Heating ◽  
Urban Surface ◽  
Prediction System ◽  
Cfd Model ◽  
Thermal Forcing ◽  
Thermal Environments ◽  
Urban Flow

Microscale urban meteorological models have been widely used in interpreting atmospheric flow and thermal discomfort in urban environments, but most previous studies examined the urban flow and thermal environments for an idealized urban morphology with imposing neutral or homogeneous thermal forcing. This study has developed a new building-scale meteorological prediction system that extends the ability to predict microscale meteorological fields in real urban environments. A computational fluid dynamics (CFD) model has been developed based on the non-hydrostatic incompressible Reynolds-averaged Navier-Stokes (RANS) equations with a standard k-ε turbulence model, and the microscale urban surface energy (MUSE) model was coupled with the CFD model to provide realistic surface thermal boundary conditions in real urban environments. It is driven by the large scale wind and temperature fields predicted by the Korean operational weather prediction model. The validation results of the new building-scale meteorological prediction system were presented against wind tunnel data and field measurements, showing its ability to predict in-canyon flows and thermal environments in association with spatiotemporal variations of surface temperatures in real urban environments. The effects of realistic surface heating on pedestrian level wind and thermal environments have been investigated through sensitivity simulations of different surface heating conditions in the highly built-up urban area. The results implied that the inclusion of surface thermal forcing is important in interpreting urban flow and thermal environment of the urban area, highlighting a realistic urban surface heating that should be considered in predicting building-scale meteorology over real urban environments.

A Study on the Effects of the Anthropogenic Heat Fluxes on the Temperature Distribution in an Urban Area

2020 ◽  
Author(s):  
Da-Som Mun ◽  
Jae-Jin Kim
Keyword(s):  
Urban Area ◽  
Thermal Environment ◽  
Heat Fluxes ◽  
Anthropogenic Heat ◽  
Target Area ◽  
Cfd Model ◽  
Residential Areas ◽  
Energy Usage ◽  
Night Time ◽  
Cfd Simulations

<p>In this study, we investigated the effects of the anthropogenic heat caused by the energy usage on the air temperature distributions in an urban area using a CFD model. We calculated the anthropogenic heat fluxes using a top-down method with monthly and hourly allocation coefficients and the total amount of the yearly electrical energy usage of buildings. To construct the buildings and to estimate the anthropogenic heat fluxes in the CFD model for the target area, we used the land use and GIS data. We conducted the CFD simulations for the heatwave period (2018.08.02 ~ 2018.08.08) in a building-congested district around the Seoul ASOS (ASOS 108) to see how the anthropogenic heat fluxes affected the thermal environment in the target area. The target area is mostly composed of commercial and residential areas. The temperature increased near the roads and buildings. At the night time, the temperature increase near the buildings with high anthropogenic heat fluxes was more significant than the daytime. The comparison with the ASOS-observed temperatures showed that the inclusion of the anthropogenic heat fluxes improved the CFD simulations of temperatures.</p>

Assessment of Observational Environments of the Automated Synoptic Observing Systems in Korea Using a CFD Model

2020 ◽  
Author(s):  
Jung-Eun Kang ◽  
Jae-Jin Kim
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Computational Domain ◽  
Cfd Model ◽  
Meteorological Observation ◽  
Wind Speeds ◽  
Air Temperatures ◽  
Computational Fluid Dynamics Cfd ◽  
Meteorological Observations ◽  
Observing Systems

<p>  In this study, we analyzed the observation environments of the automated synoptic observing systems (ASOSs) using a computational fluid dynamics (CFD) model, focusing on the observational environments of air temperatures, wind speeds, and wind directions. The computational domain sizes are 2000 m × 2000 m × 750 m, and the grid sizes are 10 m × 10 m × 5 m in the x-, y-, and z- directions, respectively. We conducted the simulations for eight inflow directions (northerly, northeasterly, easterly, southeasterly, southerly, southwesterly, westerly, northwesterly) using the ASOS-observation wind speeds and air temperatures averaged in August from 2010 to 2019. We analyzed the effects of the surrounding buildings and terrains on the meteorological observations of the ASOSs, by comparing the wind speeds, wind directions, and air temperatures simulated at the ASOSs with those of inflows. The results showed that the meteorological observation environments were quite dependent on whether there existed the obstacles and surface heating on their surfaces at the observation altitude of the ASOSs.</p>

scholarly journals Determination of Wind Pattern Inside an Urban Area Through a Mesoscale-Microscale Approach

2020 ◽  
Vol 7 (4) ◽  
pp. 515-519
Author(s):  
Nicola Germano ◽  
Camilla Lops ◽  
Sergio Montelpare ◽  
Guido Camata ◽  
Renato Ricci
Keyword(s):  
Urban Area ◽  
Mesoscale Model ◽  
Weather Forecast ◽  
Numerical Approach ◽  
Wind Speeds ◽  
Cylindrical Domains ◽  
Microscale Simulations ◽  
Error Bias ◽  
The City

The present paper aims to expose the Mesoscale-Microscale numerical approach adopted for studying the air fluxes inside an urban area located in the city of Pescara (Italy). The data, recorded by a real anemometer, are compared with three Mesoscale models (Pleim-Xiu, Blackadar and MRF-LSM), each of them presents five nested domains. On the bases of the monthly values of Root Mean Square Error, BIAS and Standard Deviation, the most accurate mesoscale model is identified and evaluated. On the Microscale side, instead, two cylindrical domains are studied. The first model considers only the topography of the terrain, whereas the other also adds the buildings present inside the investigated area. The domains, with a diameter of 6 [km] and a height equal to 0.5 [km], are studied by assuming the incoming wind from four different directions. Comparisons are then made among wind speeds and directional inflows obtained from the two models. Mesoscale analyses are carried out with the weather forecast software MM5, and Microscale simulations are performed with the commercial software STAR-CCM+.

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