scholarly journals Thermal Effects of Urban Canyon Structure on the Nocturnal Heat Island: Numerical Experiment Using a Mesoscale Model Coupled with an Urban Canopy Model

2004 ◽  
Vol 43 (12) ◽  
pp. 1899-1910 ◽  
Author(s):  
Hiroyuki Kusaka ◽  
Fujio Kimura
Keyword(s):  
Heat Capacity ◽  
Urban Canopy ◽  
Urban Canyon ◽  
View Factor ◽  
Heat Island ◽  
Urban Canopy Model ◽  
Maximum Increase ◽  
Sky View Factor ◽  
The Difference ◽  
Canopy Model

Abstract A single-layer urban canopy model is incorporated into a simple two-dimensional atmospheric model in order to examine the individual impacts of anthropogenic heating, a large heat capacity, and a small sky-view factor on mesoscale heat island formation. It is confirmed that a nocturnal heat island on a clear, calm summer day results from the difference in atmospheric stability between a city and its surroundings. The difference is caused by anthropogenic heating and the following two effects of urban canyon structure: (i) a larger heat capacity due to the walls and (ii) a smaller sky-view factor. Sensitivity experiments show that the anthropogenic heating increases the surface air temperature though the day. (This factor strongly affects the nocturnal temperature, and the maximum increase of 0.67°C occurs at 0500 LST.) The larger heat capacity due to the walls decreases the daytime temperature and increases the nocturnal temperature. (The maximum increase of 0.39°C occurs at 0600 LST.) The smaller sky-view factor increases the temperature though the day, particularly during the first several hours after sunset. (The maximum increase of 0.52°C occurs at midnight.) In urban areas, this factor results in uniform cooling that occurs at a constant rate. The impact of the canyon structure is shown to be as significant as anthropogenic heating.

scholarly journals Explore the Accuracy of the Pedestrian Level Temperature Estimated by the Combination of LCZ with WRF Urban Canopy Model through the Microclimate Measurement Network

2021 ◽  
Vol 8 (1) ◽  
pp. 14
Author(s):  
Yu-Cheng Chen ◽  
Fang-Yi Cheng ◽  
Cheng-Pei Yang ◽  
Tzu-Ping Lin
Keyword(s):  
Heat Capacity ◽  
Urban Development ◽  
Urban Climate ◽  
Urban Canopy ◽  
Subtropical Climate ◽  
Heat Island ◽  
Urban Canopy Model ◽  
Urban Heat ◽  
The City ◽  
Canopy Model

Due to the urban heat island effect becoming more evident in the cities in Taiwan, the urban climate has become an essential factor in urban development. Taiwan is located on the border of tropical and subtropical climate zones, the climate condition is hot and humid, and the city shows high-density development. The dense urban development has increased the heat storage capacity of the ground and buildings. However, if only the climate stations set by the Central Meteorological Bureau to observe the climate data are applied, the predicted results differ from the actual urban climate conditions due to the small number of these stations and the too far distance between them. Therefore, this study employs the local climate zone (LCZ), which can classify the land features by considering both land use and land cover, and can be freely generated from satellite images. The LCZ classification method can view the type of the city through the height and density of obstacles. This study also combines the urban canopy model (UCM) of the mesoscale climate prediction model and weather research and forecasts (WRF). This approach can calculate vertical and horizontal planes of the city, such as building volume, road width, the influence of streets and roofs, roof heat capacity, building wall heat capacity, etc., to predict the climatic conditions in different lands in the study area. Simultaneously, to understand the actual distribution of urban climate more accurately, this study used the microclimate measurement network built in the research area to produce pedestrian-level temperature distribution and compared the estimated results with the actual measured values for urban climate assessment. This study can understand the cause of urban heat islands and assist urban planners more appropriately formulate heat island mitigation strategies in different regions.

scholarly journals Modified RAMS-Urban Canopy Model for Heat Island Simulation in Chongqing, China

2008 ◽  
Vol 47 (2) ◽  
pp. 509-524 ◽  
Author(s):  
Hongbin Zhang ◽  
Naoki Sato ◽  
Takeki Izumi ◽  
Keisuke Hanaki ◽  
Toshiya Aramaki
Keyword(s):  
Urban Canopy ◽  
Heat Emission ◽  
Atmospheric Modeling ◽  
Anthropogenic Heat ◽  
Urban Region ◽  
Infinite Length ◽  
Heat Island ◽  
Urban Canopy Model ◽  
Canopy Model ◽  
Anthropogenic Heat Emission

Abstract A single-layer urban canopy model was integrated into a nonhydrostatic meteorological model, the Regional Atmospheric Modeling System (RAMS). In the new model, called RAMS-Urban Canopy (RAMS-UC), anthropogenic heat emission was also considered. The model can be used to calculate radiation, heat, and water fluxes in an urban area, considering the geometric structure and thermodynamic characteristics of the urban canopy. The urban canopy was represented by normalized street canyons of infinite length, which were bordered by buildings on both sides. The urban region was covered by three types of surfaces: roof, wall, and road. Anthropogenic heat was emitted from these surfaces. Sensitivity tests between the original RAMS and the modified one were carried out by simulating the urban heat island (UHI) of Chongqing, located in an inland mountainous region in China. The results of the model were also compared with the observational data. It was found that the original model could not accurately simulate the UHI, in particular at night, whereas the accuracy was significantly improved in the RAMS-UC. The improvement is substantial even when anthropogenic heat emission is set to zero.

scholarly journals Proposing the Simplification of the Multilayer Urban Canopy Model: Intercomparison Study of Four Models

2010 ◽  
Vol 49 (5) ◽  
pp. 902-919 ◽  
Author(s):  
Ryosaku Ikeda ◽  
Hiroyuki Kusaka
Keyword(s):  
Urban Canopy ◽  
View Factor ◽  
Model Intercomparison ◽  
Urban Canopy Model ◽  
Vertical Layer ◽  
Level 3 ◽  
Level 1 ◽  
Intercomparison Study ◽  
Canopy Model ◽  
Level 2

Abstract The study proposes the simplification of the multilayer urban canopy model. Four types of multilayer urban canopy models—level 4, level 3, level 2, and level 1—are developed to reduce the computational load of the heat budget calculations at the wall surface. The level 4 model, which accounts for the wall directions and the vertical layer, is simplified in three ways: the level 3 model only accounts for the vertical layers, the level 2 model accounts for the wall directions, and the level 1 model accounts for neither the wall directions nor the vertical layer. From the simplification, compared to the level 4 model, the memory is reduced by 57%, 65%, and 72% for the level 3–level 1 models, respectively, when the vertical canopy layer is seven. At the same time, the CPU time is reduced by 67%, 70%, and 78% for the level 3–level 1 models. Then, each canopy model is compared with observations in Tokyo. The results show that the simulations from the four models are close to the observed ones, and the differences among the four models are very small. An additional model intercomparison study based on idealized simulations indicates that the level 3 model can be used instead of the level 4 model in any condition, whereas the level 2 and level 1 models are proposed to be used under conditions with a large sky view factor.

A New Modeling Approach to Forecast Building Energy Demands During Extreme Heat Events in Complex Cities

2011 ◽  
Author(s):  
Estatio Gutie´rrez ◽  
Jorge E. Gonza´lez ◽  
Robert Bornstein ◽  
Mark Arend ◽  
Alberto Martilli
Keyword(s):  
Urban Heat Island ◽  
Heat Wave ◽  
Extreme Event ◽  
Large City ◽  
Urban Canopy ◽  
Anthropogenic Heat ◽  
Heat Island ◽  
Urban Canopy Model ◽  
Urban Heat ◽  
Canopy Model

The thermal response of a large city including the energy production aspects of it are explored for a large and complex city using urbanized atmospheric mesoscale modeling. The Weather Research and Forecasting (WRF) mesocale model is coupled to a multi-layer urban canopy model that considers thermal and mechanical effects of the urban environment including a building scale energy model to account for anthropogenic heat contributions due to indoor-outdoor temperature differences. This new urban parameterization is used to evaluate the evolution and the resulting urban heat island formation associated to a 3-day heat wave in New York City (NYC) during the summer of 2010. High resolution (250 m.) urban canopy parameters (UCPs) from the National Urban Database were employed to initialize the multi-layer urban parameterization. The precision of the numerical simulations is evaluated using a range of observations. Data from a dense network of surface weather stations, wind profilers and Lidar measurements are compared to model outputs over Manhattan and its surroundings during the 3-days event. The thermal and drag effects of buildings represented in the multilayer urban canopy model improves simulations over urban regions giving better estimates of the surface temperature and wind speed. An accurate representation of the nocturnal urban heat island registered over NYC in the event was obtained from the improved model. The accuracy of the simulation is further assessed against more simplified urban parameterizations models with positive results with new approach. Results are further used to quantify the energy consumption of the buildings during the heat wave, and to explore alternatives to mitigate the intensity of the UHI during the extreme event.

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