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Ryu, Young-Hee, Jong-Jin Baik, and Sang-Hyun Lee. "A New Single-Layer Urban Canopy Model for Use in Mesoscale Atmospheric Models." Journal of Applied Meteorology and Climatology 50, no. 9 (September 2011): 1773–94. http://dx.doi.org/10.1175/2011jamc2665.1.
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AbstractA new single-layer urban canopy model for use in mesoscale atmospheric models is developed and validated. The urban canopy model represents a built-up area as a street canyon, two facing buildings, and a road. In this model, the two facing walls are divided into sunlit and shaded walls on the basis of solar azimuth angle and canyon orientation, and individual surface temperature and energy budget are calculated for each wall. In addition, for better estimation of turbulent energy exchange within the canyon, a computational fluid dynamics model is employed to incorporate the effects of canyon aspect ratio (height-to-width ratio) and reference wind direction on canyon wind speed. The model contains the essential physical processes occurring in an urban canopy: absorption and reflection of shortwave and longwave radiation, exchanges of turbulent energy and water between surfaces (roof, two facing walls, and road) and adjacent air, and heat transfer by conduction through substrates. The developed urban canopy model is validated using datasets obtained at two urban sites: Marseille, France, and Basel, Switzerland. The model satisfactorily reproduces canyon air temperatures, surface temperatures, net radiation, sensible heat fluxes, latent heat fluxes, and storage heat fluxes for both sites. Extensive experiments are conducted to examine the sensitivities of the urban surface energy balance to meteorological factors and urban surface parameters. The reference wind speed is found to be a more crucial meteorological factor than the reference air temperature in altering urban surface energy balance, especially for weak winds. The urban surface energy balance is most sensitive to the roof albedo among urban surface parameters. The roof fraction, canyon aspect ratio, and ratio of roughness length for momentum to that for heat for the roof play important roles in altering urban surface energy balance.
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Flagg, D. D., and P. A. Taylor. "Sensitivity of mesoscale model urban boundary layer meteorology to urban morphology." Atmospheric Chemistry and Physics Discussions 10, no. 11 (November 3, 2010): 25909–58. http://dx.doi.org/10.5194/acpd-10-25909-2010.
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Abstract. Mesoscale modeling of the urban boundary layer requires careful parameterization of the surface due to its heterogeneous morphology. Model estimated meteorological quantities, including the surface energy budget and canopy layer variables, will respond accordingly to the scale of representation. This study examines the sensitivity of the surface energy balance, canopy layer and boundary layer meteorology to the scale of urban surface representation in a real urban area (Detroit-Windsor (USA-Canada)) during several dry, cloud-free summer periods. The model used is the Weather Research and Forecasting (WRF) model with its coupled single-layer urban canopy model. Some model verification is presented using measurements from the Border Air Quality and Meteorology Study (BAQS-Met) 2007 field campaign and additional sources. Case studies span from "neighborhood" (10 s ~ 30 m) to very coarse (120 s ~ 3.7 km) resolution. Small changes in scale can affect the classification of the surface, affecting both the local and grid-average meteorology. Results indicate high sensitivity in turbulent latent heat flux from the natural surface and sensible heat flux from the urban canopy. Small scale change is also shown to delay timing of a lake-breeze front passage and can affect the timing of local transition in static stability.
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Flagg, D. D., and P. A. Taylor. "Sensitivity of mesoscale model urban boundary layer meteorology to the scale of urban representation." Atmospheric Chemistry and Physics 11, no. 6 (March 30, 2011): 2951–72. http://dx.doi.org/10.5194/acp-11-2951-2011.
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Abstract. Mesoscale modeling of the urban boundary layer requires careful parameterization of the surface due to its heterogeneous morphology. Model estimated meteorological quantities, including the surface energy budget and canopy layer variables, will respond accordingly to the scale of representation. This study examines the sensitivity of the surface energy balance, canopy layer and boundary layer meteorology to the scale of urban surface representation in a real urban area (Detroit-Windsor (USA-Canada)) during several dry, cloud-free summer periods. The model used is the Weather Research and Forecasting (WRF) model with its coupled single-layer urban canopy model. Some model verification is presented using measurements from the Border Air Quality and Meteorology Study (BAQS-Met) 2007 field campaign and additional sources. Case studies span from "neighborhood" (10 s ~308 m) to very coarse (120 s ~3.7 km) resolution. Small changes in scale can affect the classification of the surface, affecting both the local and grid-average meteorology. Results indicate high sensitivity in turbulent latent heat flux from the natural surface and sensible heat flux from the urban canopy. Small scale change is also shown to delay timing of a lake-breeze front passage and can affect the timing of local transition in static stability.
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Li, Peiyuan, and Zhi-Hua Wang. "Modeling carbon dioxide exchange in a single-layer urban canopy model." Building and Environment 184 (October 2020): 107243. http://dx.doi.org/10.1016/j.buildenv.2020.107243.
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Kusaka, Hiroyuki, Hiroaki Kondo, Yokihiro Kikegawa, and Fujio Kimura. "A Simple Single-Layer Urban Canopy Model For Atmospheric Models: Comparison With Multi-Layer And Slab Models." Boundary-Layer Meteorology 101, no. 3 (December 2001): 329–58. http://dx.doi.org/10.1023/a:1019207923078.
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Zhang, Hongbin, Naoki Sato, Takeki Izumi, Keisuke Hanaki, and Toshiya Aramaki. "Modified RAMS-Urban Canopy Model for Heat Island Simulation in Chongqing, China." Journal of Applied Meteorology and Climatology 47, no. 2 (February 1, 2008): 509–24. http://dx.doi.org/10.1175/2007jamc1397.1.
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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.
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Vogel, Julian, and Afshin Afshari. "Comparison of Urban Heat Island Intensity Estimation Methods Using Urbanized WRF in Berlin, Germany." Atmosphere 11, no. 12 (December 9, 2020): 1338. http://dx.doi.org/10.3390/atmos11121338.
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In this study, we present a meso-scale simulation of the urban microclimate in Berlin, Germany, using the Weather Research and Forecasting (WRF) numerical weather prediction platform. The objective of the study is to derive an accurate estimate of the near-surface urban heat island (UHI) intensity. The simulation is conducted over a two-week summer period. We compare different physical schemes, different urban canopy schemes and different methods for estimating the UHI intensity. The urban fraction of each urban category is derived using the Copernicus Impervious Density data and the Corine Land Cover data. High-resolution City Geography Markup Language (CityGML) data is used to estimate the building height densities required by the multi-layer urban canopy model (UCM). Within the single-layer UCM, we implement an anthropogenic heat profile based on the large scale urban consumption of energy (LUCY) model. The optimal model configuration combines the WRF Single Moment Five-Class (WSM5) microphysics scheme, the Bougeault–Lacarrère planetary boundary layer scheme, the eta similarity (Mellor–Yamada–Janjic) surface layer scheme, the Noah Multi-Parameterization land surface model, the Dudhia and Rapid Radiative Transfer Model (RRTM) radiation schemes, and the multi-layer UCM (including the building energy model). Our simulated UHI intensity results agree well with measurements with a root mean squared error of 0.86K and a mean bias error of 0.20K. After model validation, we proceed to compare several UHI intensity calculation methods, including the ‘ring rural reference’ (RRR) method and the ‘virtual rural reference’ (VRR) method. The VRR mthod is also known as the ‘urban increment’ method. We suggest and argument that the VRR approach is superior.
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Demuzere, M., A. M. Coutts, M. Göhler, A. M. Broadbent, H. Wouters, N. P. M. van Lipzig, and L. Gebert. "The implementation of biofiltration systems, rainwater tanks and urban irrigation in a single-layer urban canopy model." Urban Climate 10 (December 2014): 148–70. http://dx.doi.org/10.1016/j.uclim.2014.10.012.
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Wang, Chenghao, Zhi-Hua Wang, and Young-Hee Ryu. "A single-layer urban canopy model with transmissive radiation exchange between trees and street canyons." Building and Environment 191 (March 2021): 107593. http://dx.doi.org/10.1016/j.buildenv.2021.107593.
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Simón‐Moral, Andrés, Anurag Dipankar, Matthias Roth, Claudio Sánchez, Erik Velasco, and Xiang‐Yu Huang. "Application of MORUSES single‐layer urban canopy model in a tropical city: Results from Singapore." Quarterly Journal of the Royal Meteorological Society 146, no. 727 (December 17, 2019): 576–97. http://dx.doi.org/10.1002/qj.3694.
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Miao, Shiguang, Fei Chen, Margaret A. LeMone, Mukul Tewari, Qingchun Li, and Yingchun Wang. "An Observational and Modeling Study of Characteristics of Urban Heat Island and Boundary Layer Structures in Beijing." Journal of Applied Meteorology and Climatology 48, no. 3 (March 1, 2009): 484–501. http://dx.doi.org/10.1175/2008jamc1909.1.
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Abstract In this paper, the characteristics of urban heat island (UHI) and boundary layer structures in the Beijing area, China, are analyzed using conventional and Moderate Resolution Imaging Spectroradiometer (MODIS) observations. The Weather Research and Forecasting (WRF) model coupled with a single-layer urban canopy model (UCM) is used to simulate these urban weather features for comparison with observations. WRF is also used to test the sensitivity of model simulations to different urban land use scenarios and urban building structures to investigate the impacts of urbanization on surface weather and boundary layer structures. Results show that the coupled WRF/Noah/UCM modeling system seems to be able to reproduce the following observed features reasonably well: 1) the diurnal variation of UHI intensity; 2) the spatial distribution of UHI in Beijing; 3) the diurnal variation of wind speed and direction, and interactions between mountain–valley circulations and UHI; 4) small-scale boundary layer convective rolls and cells; and 5) the nocturnal boundary layer lower-level jet. The statistical analyses reveal that urban canopy variables (e.g., temperature, wind speed) from WRF/Noah/UCM compare better with surface observations than the conventional variables (e.g., 2-m temperature, 10-m wind speed). Both observations and the model show that the airflow over Beijing is dominated by mountain–valley flows that are modified by urban–rural circulations. Sensitivity tests imply that the presence or absence of urban surfaces significantly impacts the formation of horizontal convective rolls (HCRs), and the details in urban structures seem to have less pronounced but not negligible effects on HCRs.
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Miao, ShiGuang, and Fei Chen. "Enhanced modeling of latent heat flux from urban surfaces in the Noah/single-layer urban canopy coupled model." Science China Earth Sciences 57, no. 10 (August 8, 2014): 2408–16. http://dx.doi.org/10.1007/s11430-014-4829-0.
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Salamanca, Francisco, Alberto Martilli, Mukul Tewari, and Fei Chen. "A Study of the Urban Boundary Layer Using Different Urban Parameterizations and High-Resolution Urban Canopy Parameters with WRF." Journal of Applied Meteorology and Climatology 50, no. 5 (May 2011): 1107–28. http://dx.doi.org/10.1175/2010jamc2538.1.
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AbstractIn the last two decades, mesoscale models (MMs) with urban canopy parameterizations have been widely used to study urban boundary layer processes. Different studies show that such parameterizations are sensitive to the urban canopy parameters (UCPs) that define the urban morphology. At the same time, high-resolution UCP databases are becoming available for several cities. Studies are then needed to determine, for a specific application of an MM, the optimum degree of complexity of the urban canopy parameterizations and the resolution and details necessary in the UCP datasets. In this work, and in an attempt to answer the previous issues, four urban canopy schemes, with different degrees of complexity, have been used with the Weather Research and Forecasting (WRF) model to simulate the planetary boundary layer over the city of Houston, Texas, for two days in August 2000. For the UCP two approaches have been considered: one based on three urban classes derived from the National Land Cover Data of the U.S. Geological Survey and one based on the highly detailed National Urban Database and Access Portal Tool (NUDAPT) dataset with a spatial resolution of 1 km2. Two-meter air temperature and surface wind speed have been used in the evaluation. The statistical analysis shows a tendency to overestimate the air temperatures by the simple bulk scheme and underestimate the air temperatures by the more detailed urban canopy parameterizations. Similarly, the bulk and single-layer schemes tend to overestimate the wind speed while the multilayer schemes underestimate it. The three-dimensional analysis of the meteorological fields revealed a possible impact (to be verified against measurements) of both the urban schemes and the UCP on cloud prediction. Moreover, the impact of air conditioning systems on the air temperature and their energy consumption has been evaluated with the most developed urban scheme for the two simulated days. During the night, this anthropogenic heat was responsible for an increase in the air temperature of up to 2°C in the densest urban areas, and the estimated energy consumption was of the same magnitude as energy consumption obtained with different methods when the most detailed UCP database was used. On the basis of the results for the present case study, one can conclude that if the purpose of the simulation requires only an estimate of the 2-m temperature a simple bulk scheme is sufficient but if the purpose of the simulation is an evaluation of an urban heat island mitigation strategy or the evaluation of the energy consumption due to air conditioning at city scale, it is necessary to use a complex urban canopy scheme and a detailed UCP.
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Wang, Zhi-Hua, Elie Bou-Zeid, Siu Kui Au, and James A. Smith. "Analyzing the Sensitivity of WRF’s Single-Layer Urban Canopy Model to Parameter Uncertainty Using Advanced Monte Carlo Simulation." Journal of Applied Meteorology and Climatology 50, no. 9 (September 2011): 1795–814. http://dx.doi.org/10.1175/2011jamc2685.1.
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AbstractSingle-layer physically based urban canopy models (UCM) have gained popularity for modeling urban–atmosphere interactions, especially the energy transport component. For a UCM to capture the physics of conductive, radiative, and turbulent advective transport of energy, it is important to provide it with an accurate parameter space, including both mesoscale meteorological forcing and microscale surface inputs. While field measurement of all input parameters to a UCM is rarely possible, understanding the model sensitivity to individual parameters is essential to determine the relative importance of parameter uncertainty for model performance. In this paper, an advanced Monte Carlo approach—namely, subset simulation—is used to quantify the impact of the uncertainty of surface input parameters on the output of an offline modified version of the Weather Research and Forecasting (WRF)-UCM. On the basis of the conditional sampling technique, the importance of surface parameters is determined in terms of their impact on critical model responses. It is found that model outputs (both critical energy fluxes and surface temperatures) are highly sensitive to uncertainties in urban geometry, whereas variations in emissivities and building interior temperatures are relatively insignificant. In addition, the sensitivity of the model to input surface parameters is also shown to be very weakly dependent on meteorological parameters. The statistical quantification of the model’s sensitivity to input parameters has practical implications, such as surface parameter calibrations in UCM and guidance for urban heat island mitigation strategies.
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Ao, Xiangyu, and Ning Zhang. "Parameter Sensitivity Analysis and Optimization of the Single-Layer Urban Canopy Model in the Megacity of Shanghai." Advances in Meteorology 2022 (April 11, 2022): 1–15. http://dx.doi.org/10.1155/2022/7351150.
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In order to meet the demand of more refined urban weather forecast, it is of great practical significance to improve and optimize the single-layer urban canopy model (SLUCM) suitable for the megacity of Shanghai. In this paper, based on the offline SLUCM model driven by a whole-year surface flux observation data in the Shanghai central business district, a series of parameter sensitivity tests are carried out by using the one at a time (OAT) method, the relative importance and a set of optimized parameters of the SLUCM suitable for high-density urban area are established, and the improvement of simulation is evaluated. The results show that SLUCM well reproduces the seasonal mean diurnal patterns of the net all-wave radiation flux ( Q ∗ ) and sensible heat flux (QH) but underestimates their magnitudes. Both Q ∗ and QH are linearly sensitive to the albedo, and most sensitive to the roof albedo, the second to the wall albedo, but relatively insensitive to the road albedo. The sensitivity of Q ∗ and QH to emissivity is not as strong as that of albedo, and the variation trend is also linear. Similar to albedo, Q ∗ and QH are most sensitive to roof emissivity. The effect of thermal parameters (heat capacity and conductivity) on fluxes is logarithmic. The sensitivity of surface fluxes to geometric parameters has no specific variation pattern. After parameter optimization, RMSE of Q ∗ decreases by about 3.4–18.7 Wm−2 in four seasons. RMSE of the longwave radiation (L↑) decreases by about 1.2–7.87 Wm−2. RMSE of QH decreases by about 2–5 Wm−2. This study provides guidance for future development of the urban canopy model parameterizations and urban climate risk response.
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Schoetter, Robert, Yu Ting Kwok, Cécile de Munck, Kevin Ka Lun Lau, Wai Kin Wong, and Valéry Masson. "Multi-layer coupling between SURFEX-TEB-v9.0 and Meso-NH-v5.3 for modelling the urban climate of high-rise cities." Geoscientific Model Development 13, no. 11 (November 18, 2020): 5609–43. http://dx.doi.org/10.5194/gmd-13-5609-2020.
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Abstract. Urban canopy models (UCMs) represent the exchange of momentum, heat, and moisture between cities and the atmosphere. Single-layer UCMs interact with the lowest atmospheric model level and are suited for low- to mid-rise cities, whereas multi-layer UCMs interact with multiple levels and can also be employed for high-rise cities. The present study describes the multi-layer coupling between the Town Energy Balance (TEB) UCM included in the Surface Externalisée (SURFEX) land surface model and the Meso-NH mesoscale atmospheric model. This is a step towards better high-resolution weather prediction for urban areas in the future and studies quantifying the impact of climate change adaptation measures in high-rise cities. The effect of the buildings on the wind is considered using a drag force and a production term in the prognostic equation for turbulent kinetic energy. The heat and moisture fluxes from the walls and the roofs to the atmosphere are released at the model levels intersecting these urban facets. No variety of building height at grid-point scale is considered to remain the consistency between the modification of the Meso-NH equations and the geometric assumptions of TEB. The multi-layer coupling is evaluated for the heterogeneous high-rise, high-density city of Hong Kong. It leads to a strong improvement of model results for near-surface air temperature and relative humidity, which is due to better consideration of the process of horizontal advection in the urban canopy layer. For wind speed, model results are improved on average by the multi-layer coupling but not for all stations. Future developments of the multi-layer SURFEX-TEB will focus on improving the calculation of radiative exchanges, which will allow a variety of building heights at grid-point scale to be taken into account.
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Reames, Larissa J., and David J. Stensrud. "Sensitivity of Simulated Urban–Atmosphere Interactions in Oklahoma City to Urban Parameterization." Journal of Applied Meteorology and Climatology 56, no. 5 (May 2017): 1405–30. http://dx.doi.org/10.1175/jamc-d-16-0223.1.
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AbstractThe world’s population is increasingly concentrated in large urban areas. Many observational and modeling studies have explored how these large, population-dense cities modify local and mesoscale atmospheric phenomena. These modeling studies often use an urban canopy model to parameterize urban surfaces. However, it is unclear whether this approach is appropriate for more suburban cities, such as those found in the Great Plains. Thus, the Weather Research and Forecasting Model was run for a week over Oklahoma City, Oklahoma, and results were compared with observations. Overall, four configurations were examined. Two simulations used the Noah LSM, one with all urban areas removed (CTRL), and the other with urban areas parameterized by a modified Noah land surface model with three urban categories (LSMMOD). Additional simulations utilized a single-layer urban canopy model (SLUCM) either with default urban fraction values (SLUCM1) or with urban fractions taken from the National Land Cover Database (SLUCM2). Results from the three urban runs compared favorably to high-density temperature observations of the urban heat island. The SLUCM1 run was the most realistic, although the urban fractions applied were the least representative of Oklahoma City. All urban runs also produced a drier and deeper planetary boundary layer over the city. The prediction of near-surface winds was most problematic, with the two SLUCM runs unable to correctly reproduce reduced wind speeds over the city. The modified Noah LSM provided best overall agreement with observations and represents a reasonable option for simulating the urban effects of more-suburban cities.
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Wang, Jian, Jingbo Mao, Yan Zhang, Tiantao Cheng, Qi Yu, Jiani Tan, and Weichun Ma. "Simulating the Effects of Urban Parameterizations on the Passage of a Cold Front During a Pollution Episode in Megacity Shanghai." Atmosphere 10, no. 2 (February 15, 2019): 79. http://dx.doi.org/10.3390/atmos10020079.
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Urbanization significantly influences meteorological conditions and air quality. Statistically, air pollution in the megacity of Shanghai usually occurs with cold weather fronts. An air pollution episode during a cold front was simulated using weather research and forecasting and the Community Multi-scale Air Quality model system. In this study, we used two urban schemes, a simple bulk scheme (denoted BULK) and the single-layer urban canopy model (SLUCM), to check the effects of urban parameterization. Our results showed that SLUCM better predicted the arrival time and cooling process of the cold front and more realistically simulated the moving process of the cold front. The improvement in the temperature and relative humidity simulation achieved using SLUCM was more effective under higher urbanization levels, whereas the wind speed simulation was better in rural areas. The simulated concentrations at sites with high urbanization were obviously improved by urban parameterization. The barrier role of the urban canopy during a cold front was better represented and was shown to cause a wider polluted area and higher pollutant concentration using SLUCM than with BULK. Overall, accurate meteorological simulations in the atmospheric boundary layer using SLUCM are expected to provide good prediction of urban air quality.
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Tsiringakis, Aristofanis, Gert‐Jan Steeneveld, Albert A. M. Holtslag, Simone Kotthaus, and Sue Grimmond. "On‐ and off‐line evaluation of the single‐layer urban canopy model in London summertime conditions." Quarterly Journal of the Royal Meteorological Society 145, no. 721 (March 21, 2019): 1474–89. http://dx.doi.org/10.1002/qj.3505.
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Holt, Teddy, and Julie Pullen. "Urban Canopy Modeling of the New York City Metropolitan Area: A Comparison and Validation of Single- and Multilayer Parameterizations." Monthly Weather Review 135, no. 5 (May 1, 2007): 1906–30. http://dx.doi.org/10.1175/mwr3372.1.
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Abstract High-resolution numerical simulations are conducted using the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS)1 with two different urban canopy parameterizations for a 23-day period in August 2005 for the New York City (NYC) metropolitan area. The control COAMPS simulations use the single-layer Weather Research and Forecasting (WRF) Urban Canopy Model (W-UCM) and sensitivity simulations use a multilayer urban parameterization based on Brown and Williams (BW-UCM). Both simulations use surface forcing from the WRF land surface model, Noah, and hourly sea surface temperature fields from the New York Harbor and Ocean Prediction System model hindcast. Mean statistics are computed for the 23-day period from 5 to 27 August (540-hourly observations) at five Meteorological Aviation Report stations for a nested 0.444-km horizontal resolution grid centered over the NYC metropolitan area. Both simulations show a cold mean urban canopy air temperature bias primarily due to an underestimation of nighttime temperatures. The mean bias is significantly reduced using the W-UCM (−0.10°C for W-UCM versus −0.82°C for BW-UCM) due to the development of a stronger nocturnal urban heat island (UHI; mean value of 2.2°C for the W-UCM versus 1.9°C for the BW-UCM). Results from a 24-h case study (12 August 2005) indicate that the W-UCM parameterization better maintains the UHI through increased nocturnal warming due to wall and road effects. The ground heat flux for the W-UCM is much larger during the daytime than for the BW-UCM (peak ∼300 versus 100 W m−2), effectively shifting the period of positive sensible flux later into the early evening. This helps to maintain the near-surface mixed layer at night in the W-UCM simulation and sustains the nocturnal UHI. In contrast, the BW-UCM simulation develops a strong nocturnal stable surface layer extending to approximately 50–75-m depth. Subsequently, the nocturnal BW-UCM wind speeds are a factor of 3–4 less than W-UCM with reduced nighttime turbulent kinetic energy (average < 0.1 m2 s−2). For the densely urbanized area of Manhattan, BW-UCM winds show more dependence on urbanization than W-UCM. The decrease in urban wind speed is most prominent for BW-UCM both in the day- and nighttime over lower Manhattan, with the daytime decrease generally over the region of tallest building heights while the nighttime decrease is influenced by both building height as well as urban fraction. In contrast, the W-UCM winds show less horizontal variation over Manhattan, particularly during the daytime. These results stress the importance of properly characterizing the urban morphology in urban parameterizations at high resolutions to improve the model’s predictive capability.
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Masson, Valéry, and Yann Seity. "Including Atmospheric Layers in Vegetation and Urban Offline Surface Schemes." Journal of Applied Meteorology and Climatology 48, no. 7 (July 1, 2009): 1377–97. http://dx.doi.org/10.1175/2009jamc1866.1.
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Abstract A formulation to include prognostic atmospheric layers in offline surface schemes is derived from atmospheric equations. Whereas multilayer schemes developed previously need a complex coupling between atmospheric-model levels and surface-scheme levels, the coupling proposed here remains simple. This is possible because the atmospheric layers interacting with the surface scheme are independent of the atmospheric model that could be coupled above. The surface boundary layer (SBL; both inside and just above the canopy) is resolved prognostically, taking into account large-scale forcing, turbulence, and, if any, drag and canopy forces and surface fluxes. This formulation allows one to retrieve the logarithmic law in neutral conditions, and it has been validated when coupled to a 3D atmospheric model. Systematic comparisons with 2-m observations and 10-m wind have been made for 2 months. The SBL scheme is able to model the 2-m temperature accurately, as well as the 10-m wind, without any use of analytical interpolation. The largest improvement takes place during stable conditions (i.e., by night), during which analytical laws and interpolation methods are known to be less accurate, and in mountainous areas, in which nocturnal low-level flow is strongly influenced by surface cooling. The prognostic SBL scheme is shown to solve the nighttime physical disconnection problem between surface and atmosphere models. The inclusion of the SBL into the urban Town Energy Balance scheme is presented in a paper by Hamdi and Masson in which the ability of the method to simulate the profiles of both mean and turbulent quantities from above the building down to the road surface is shown using data from the Basel Urban Boundary Layer Experiment (BUBBLE). The proposed method will allow the inclusion of the detailed physics of the multilayer schemes (e.g., the interactions of the SBL flow with forest or urban canopy) into a single-layer scheme that is easily coupled with atmospheric models.
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Huszar, P., T. Halenka, M. Belda, M. Zak, K. Sindelarova, and J. Miksovsky. "Regional climate model assessment of the urban land-surface forcing over central Europe." Atmospheric Chemistry and Physics Discussions 14, no. 12 (July 14, 2014): 18541–89. http://dx.doi.org/10.5194/acpd-14-18541-2014.
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Abstract. For the purpose of qualifying and quantifying the climate impact of cities and urban surfaces in general on climate of central Europe, the surface parameterization in regional climate model RegCM4 has been extended with the Single Layer Urban Canopy Model (SLUCM). A set of experiments was performed over the period of 2005–2009 for central Europe, either without considering urban surfaces or with the SLUCM treatment. Results show a statistically significant impact of urbanized surfaces on temperature (up to 1.5 K increase in summer) as well as on the boundary layer height (increases up to 50 m). Urbanization further influences surface wind with a winter decrease up to −0.6 m s−1, though both increases and decreases were detected in summer depending on the location relative to the cities and daytime (changes up to 0.3 m s−1). Urban surfaces significantly reduce evaporation and thus the humidity over the surface. This impacts the simulated summer precipitation rate, showing decrease over cities up to −2 mm day−1. Significant temperature increases are simulated over higher elevations as well, not only within the urban canopy layer. With the urban parameterization, the climate model better describes the diurnal temperature variation, reducing the cold afternoon and evening bias of RegCM4. Sensitivity experiments were carried out to quantify the response of the meteorological conditions to changes in the parameters specific to the urban environment such as street width, building height, albedo of the roofs and anthropogenic heat release. The results proved to be rather robust and the choice of the key SLUCM parameters impacts them only slightly (mainly temperature, boundary layer height and wind velocity). Statistically significant impacts are modeled not only over large urbanized areas, but the influence of the cities is also evident over rural areas without major urban surfaces. It is shown that this is the result of the combined effect of the distant influence of the cities and the influence of the minor local urban surface coverage.
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Huszar, P., T. Halenka, M. Belda, M. Zak, K. Sindelarova, and J. Miksovsky. "Regional climate model assessment of the urban land-surface forcing over central Europe." Atmospheric Chemistry and Physics 14, no. 22 (November 26, 2014): 12393–413. http://dx.doi.org/10.5194/acp-14-12393-2014.
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Abstract. For the purpose of qualifying and quantifying the climate impact of cities and urban surfaces in general on climate of central Europe, the surface parameterization in regional climate model RegCM4 has been extended with the Single-layer Urban Canopy Model (SLUCM). A set of experiments was performed over the period of 2005–2009 for central Europe, either without considering urban surfaces or with the SLUCM treatment. Results show a statistically significant impact of urbanized surfaces on temperature (up to 1.5 K increase in summer) as well as on the boundary layer height (increases up to 50 m). Urbanization further influences surface wind with a winter decrease up to −0.6 m s−1, though both increases and decreases were detected in summer depending on the location relative to the cities and daytime (changes up to 0.3 m s−1). Urban surfaces significantly reduce the humidity over the surface. This impacts the simulated summer precipitation rate, showing a decrease over cities of up to −2 mm day−1. Significant temperature increases are simulated over higher altitudes as well, not only within the urban canopy layer. With the urban parameterization, the climate model better describes the diurnal temperature variation, reducing the cold afternoon and evening bias of RegCM4. Sensitivity experiments were carried out to quantify the response of the meteorological conditions to changes in the parameters specific to the urban environment, such as street width, building height, albedo of the roofs and anthropogenic heat release. The results proved to be rather robust and the choice of the key SLUCM parameters impacts them only slightly (mainly temperature, boundary layer height and wind velocity). Statistically significant impacts are modelled not only over large urbanized areas, but the influence of the cities is also evident over rural areas without major urban surfaces. It is shown that this is the result of the combined effect of the distant influence of the cities and the influence of the minor local urban surface coverage.
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Salim, Mohamed H., Sebastian Schubert, Jaroslav Resler, Pavel Krč, Björn Maronga, Farah Kanani-Sühring, Matthias Sühring, and Christoph Schneider. "Importance of radiative transfer processes in urban climate models: a study based on the PALM 6.0 model system." Geoscientific Model Development 15, no. 1 (January 10, 2022): 145–71. http://dx.doi.org/10.5194/gmd-15-145-2022.
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Abstract. Including radiative transfer processes within the urban canopy layer into microscale urban climate models (UCMs) is essential to obtain realistic model results. These processes include the interaction of buildings and vegetation with shortwave and longwave radiation, thermal emission, and radiation reflections. They contribute differently to the radiation budget of urban surfaces. Each process requires different computational resources and physical data for the urban elements. This study investigates how much detail modellers should include to parameterize radiative transfer in microscale building-resolving UCMs. To that end, we introduce a stepwise parameterization method to the Parallelized Large-eddy Simulation Model (PALM) system 6.0 to quantify individually the effects of the main radiative transfer processes on the radiation budget and on the flow field. We quantify numerical simulations of both simple and realistic urban configurations to identify the major and the minor effects of radiative transfer processes on the radiation budget. The study shows that processes such as surface and vegetation interaction with shortwave and longwave radiation will have major effects, while a process such as multiple reflections will have minor effects. The study also shows that radiative transfer processes within the canopy layer implicitly affect the incoming radiation since the radiative transfer model is coupled to the radiation model. The flow field changes considerably in response to the radiative transfer processes included in the model. The study identified those processes which are essentially needed to assure acceptable quality of the flow field. These processes are receiving radiation from atmosphere based on the sky-view factors, interaction of urban vegetation with radiation, radiative transfer among urban surfaces, and considering at least single reflection of radiation. Omitting any of these processes may lead to high uncertainties in the model results.
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KUSAKA, Hiroyuki, and Fujio KIMURA. "Coupling a Single-Layer Urban Canopy Model with a Simple Atmospheric Model: Impact on Urban Heat Island Simulation for an Idealized Case." Journal of the Meteorological Society of Japan 82, no. 1 (2004): 67–80. http://dx.doi.org/10.2151/jmsj.82.67.
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Dong, Long Xiang, Hong Chao Zuo, and Wen Cheng Dong. "Validation of CALPUFF Applicability within Urban Area." Advanced Materials Research 726-731 (August 2013): 1813–16. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.1813.
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An atmospheric tracer dispersion study known as Urban Meteorological and Tracer Experiment was carried out in Yuzhong County, Gansu province in northwest of China, during October of 2011. By using the observational data, the applicability of CALPUFF model based on Gaussian formula was verified within urban area. The results show that (i) CALPUFF model can reasonably reflect the actual observations on the whole, and the high value centers of tracer concentration was changed with wind direction over the urban canopy layer. (ii) The simulated plume central axis has a bias of 10-15° with observations, and the simulation error is very much big at the single point, especially at the ground.
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Vahmani, Pouya, and Terri S. Hogue. "Incorporating an Urban Irrigation Module into the Noah Land Surface Model Coupled with an Urban Canopy Model." Journal of Hydrometeorology 15, no. 4 (July 30, 2014): 1440–56. http://dx.doi.org/10.1175/jhm-d-13-0121.1.
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Abstract The current research examines the influence of irrigation on urban hydrological cycles through the development of an irrigation scheme within the Noah land surface model (LSM)–Single Layer Urban Canopy Model (SLUCM) system. The model is run at a 30-m resolution for a 2-yr period over a 49 km2 urban domain in the Los Angeles metropolitan area. A sensitivity analysis indicates significant sensitivity relative to both the amount and timing of irrigation on diurnal and monthly energy budgets, hydrological fluxes, and state variables. Monthly residential water use data and three estimates of outdoor water consumption are used to calibrate the developed irrigation scheme. Model performance is evaluated using a previously developed MODIS–Landsat evapotranspiration (ET) and Landsat land surface temperature (LST) products as well as hourly ET observations through the California Irrigation Management Information System (CIMIS). Results show that the Noah LSM–SLUCM realistically simulates the diurnal and seasonal variations of ET when the irrigation module is incorporated. However, without irrigation, the model produces large biases in ET simulations. The ET errors for the nonirrigation simulations are −56 and −90 mm month−1 for July 2003 and 2004, respectively, while these values decline to −6 and −11 mm month−1 over the same 2 months when the proposed irrigation scheme is adopted. Results show that the irrigation-induced increase in latent heat flux leads to a decrease in LST of about 2°C in urban parks. The developed modeling framework can be utilized for a number of applications, ranging from outdoor water use estimation to climate change impact assessments.
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Bhavana, M., K. Gupta, and P. K. Pal. "URBAN MICRO CLIMATE MODELLING USING DIFFERENT URBAN PHYISCS SCHEMES AND HIGH RESOLUTION LULC WITH WRF MODEL." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-5 (November 19, 2018): 491–98. http://dx.doi.org/10.5194/isprs-archives-xlii-5-491-2018.
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<p><strong>Abstract.</strong> Urban areas are treated as a single entity by mesoscale urban canopy models (UCM) for assessing the influence of urban morphology on climate. Weather Research and Forecasting Model (WRF) coupled with UCM along with urban physics options to describe the urban features such as Single Layer Urban Canopy Model (SLUCM), Building Energy Parameterization (BEP) and Building Energy Model (BEM) which enumerates the influence of urban features on the local scale other than the bulk parameterization (no urban physics option), which is generally used in most of the operational forecasting models. Besides, WRF model also enables to integrate multi-class Urban Land Use Land Cover (LULC) whereas most of the globally available LULC depict urban area as single urban built-up class. This study aims to analyze performance of high resolution urban LULC and urban physics options for Chandigarh area by downscaling climatic variables up to 1km and its validation with the ground observation data. The inner domain (1<span class="thinspace"></span>km resolution) was configured with default LULC for one set of simulations and multi-class urban LULC for other set of simulations. All the simulations were carried out for 3 days (August 19&ndash;21, 2017) due to computational restrictions by employing all the four urban physics options. It has been found that multi-class urban LULC yielded better results than single class urban built –up simulation when validated with respect to ground observation. The RMSE values for multi-class urban LULC provided less RMSE than single class urban LULC, those are in terms of temperature at 2<span class="thinspace"></span>m, relative humidity and wind speed are 0.91<span class="thinspace"></span>&deg;C, 2.63% and 1.82<span class="thinspace"></span>m/s respectively. Similarly, BEP+BEM urban physics option provided reduced RMSE values than the SLUCM and BEP scheme. The RMSE values in terms of temperature at 2<span class="thinspace"></span>m, relative humidity and wind speed are 1.11<span class="thinspace"></span>&deg;C, 4.39% and 2.62<span class="thinspace"></span>m/s respectively.</p>
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Brownlee, James, Pallav Ray, Mukul Tewari, and Haochen Tan. "Relative Role of Turbulent and Radiative Flux on the Near-Surface Temperature in a Single-Layer Urban Canopy Model over Houston." Journal of Applied Meteorology and Climatology 56, no. 8 (August 2017): 2173–87. http://dx.doi.org/10.1175/jamc-d-17-0088.1.
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AbstractNumerical simulations without hydrological processes tend to overestimate the near-surface temperatures over urban areas. This is presumably due to underestimation of surface latent heat flux. To test this hypothesis, the existing single-layer urban canopy model (SLUCM) within the Weather Research and Forecasting Model is evaluated over Houston, Texas. Three simulations were conducted during 24–26 August 2000. The simulations include the use of the default “BULK” urban scheme, the SLUCM without hydrological processes, and the SLUCM with hydrological processes. The results show that the BULK scheme was least accurate, and it overestimated the near-surface temperatures and winds over the urban regions. In the presence of urban hydrological processes, the SLUCM underestimates these parameters. An analysis of the surface heat fluxes suggests that the error in the BULK scheme is due to a lack of moisture at the urban surface, whereas the error in the SLUCM with hydrological processes is due to increases in moisture at the urban surface. These results confirm earlier studies in which changes in near-surface temperature were primarily due to the changes in the turbulent (latent and sensible heat) fluxes in the presence of hydrological processes. The contribution from radiative flux was about one-third of that from turbulent flux. In the absence of hydrological processes, however, the results indicate that the changes in radiative flux contribute more to the near-surface temperature changes than the turbulent heat flux. The implications of these results are discussed.
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Chen, Yan, Ning Zhang, and Yan Zhu. "High-Resolution Simulations of the Urban Thermal Climate in Suzhou City, China." Atmosphere 10, no. 3 (March 4, 2019): 118. http://dx.doi.org/10.3390/atmos10030118.
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City thermal discomfort conditions have been exacerbated by the rapid urbanization processes in China. High-resolution urban thermal climate simulations can help us to understand urban climate features and produce better urban designs. In this paper, a single-layer urban canopy model (UCM) combined with Landsat satellite data and high-resolution meteorological forcing data was used to simulate very-high-resolution characteristics of temperature and humidity at the urban canopy level, and the heat index at the pedestrian level was also estimated. The research shows that the National center of environmental forecasting, Oregon state university, Air force and Hydrological research lab (NOAH)-UCM model can simulate the distribution of meteorological elements for different land uses in a fine and effective manner, making it an effective approach to obtaining the fundamental data for urban climate analysis. The spatial distribution pattern of urban heat islands in Suzhou is highly consistent with urban land cover fraction. High-density and medium-density urban areas are centers of urban heat islands, and the annual number of high-temperature days and heat indices over the high-density and medium-density urban areas are markedly higher than those in low-density cities and suburbs, indicating that urban development has a significant impact on the urban thermal environment.
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Zhao, Wenjing, Ning Zhang, Jianning Sun, and Jun Zou. "Evaluation and Parameter-Sensitivity Study of a Single-Layer Urban Canopy Model (SLUCM) with Measurements in Nanjing, China." Journal of Hydrometeorology 15, no. 3 (June 1, 2014): 1078–90. http://dx.doi.org/10.1175/jhm-d-13-0129.1.
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Abstract An offline single-layer urban canopy model (SLUCM) was driven by the surface energy balance observations in winter in Nanjing, China, to evaluate the capability of the model to simulate the urban surface energy balance. The results of the evaluation suggest that the simulated daytime net radiation is approximately 20% lower than the observed and display relatively high systematic error, which is due to the relatively poor capacity of the model to simulate the daytime longwave radiation (which is underestimated by approximately 35%). By contrast, the simulated sensible heat flux shows mainly unsystematic error. Moreover, the one-at-a-time method is used to conduct a sensitivity analysis of the model parameters. The sensitivity analysis demonstrates that the major factors affecting the surface energy balance are the albedo, the thermal conductivity, and the roof and wall volumetric heat capacity. The influences of the shape of the street canyon and the average height of buildings are relatively weaker. The effects of the albedo on the fluxes are nearly linear. The effects of the thermal parameters are approximately logarithmic. Furthermore, the simulated sensible heat flux in the SLUCM is insensitive to the morphological parameters of the buildings.
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Aoyagi, Toshinori, and Naoko Seino. "A Square Prism Urban Canopy Scheme for the NHM and Its Evaluation on Summer Conditions in the Tokyo Metropolitan Area, Japan." Journal of Applied Meteorology and Climatology 50, no. 7 (July 2011): 1476–96. http://dx.doi.org/10.1175/2011jamc2489.1.
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AbstractA single-layered square prism urban canopy (SPUC) scheme for the Japan Meteorological Agency nonhydrostatic model (NHM) was developed. This scheme considers the urban canopy layer with square prism–shaped buildings. The basic concept of this scheme is similar to those of the conventional energy balance models for an urban canyon structure. The scheme presented here differs slightly from them in its representation of the bulk resistance circuit and some treatments of radiation processes, however, as well as by considering the water reservoir on building surfaces. A comparison between the SPUC scheme and the existing slab scheme of the NHM was made on summer days in the Tokyo metropolitan area. The SPUC run more accurately reproduced the expected behavior of the urban canopy effect than did the slab run. The effective albedo was smaller in the SPUC run than in the slab run (the upward shortwave radiation of the SPUC run was smaller than that of the slab run). The forecast heat fluxes in the SPUC run, however, showed worse performances. Adequate parameter settings (especially concerning latent heat fluxes) are needed in the SPUC run. The mean bias errors of the surface air temperature during nighttime were less negative and slightly improved in the SPUC run than in the slab run.
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Silva, Rui, Ana Cristina Carvalho, David Carvalho, and Alfredo Rocha. "Study of Urban Heat Islands Using Different Urban Canopy Models and Identification Methods." Atmosphere 12, no. 4 (April 20, 2021): 521. http://dx.doi.org/10.3390/atmos12040521.
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This work aims to compare the performance of the single‑(SLUCM) and multilayer (BEP-Building effect parameterization) urban canopy models (UCMs) coupled with the Weather Research and Forecasting model (WRF), along with the application of two urban heat island (UHI) identification methods. The identification methods are: (1) the “classic method”, based on the temperature difference between urban and rural areas; (2) the “local method” based on the temperature difference at each urban location when the model land use is considered urban, and when it is replaced by the dominant rural land use category of the urban surroundings. The study is performed as a case study for the city of Lisbon, Portugal, during the record-breaking August 2003 heatwave event. Two main differences were found in the UHI intensity (UHII) and spatial distribution between the identification methods: a reduction by half in the UHII during nighttime when using the local method; and a dipole signal in the daytime and nighttime UHI spatial pattern when using the classic method, associated with the sheltering effect provided by the high topography in the northern part of the city, that reduces the advective cooling in the lower areas under prevalent northern wind conditions. These results highlight the importance of using the local method in UHI modeling studies to fully isolate urban canopy and regional geographic contributions to the UHII and distribution. Considerable improvements were obtained in the near‑surface temperature representation by coupling WRF with the UCMs but better with SLUCM. The nighttime UHII over the most densely urbanized areas is lower in BEP, which can be linked to its larger nocturnal turbulent kinetic energy (TKE) near the surface and negative sensible heat (SH) fluxes. The latter may be associated with the lower surface skin temperature found in BEP, possibly owing to larger turbulent SH fluxes near the surface. Due to its higher urban TKE, BEP significantly overestimates the planetary boundary layer height compared with SLUCM and observations from soundings. The comparison with a previous study for the city of Lisbon shows that BEP model simulation results heavily rely on the number and distribution of vertical levels within the urban canopy.
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Lee, S. H., S. W. Kim, W. M. Angevine, L. Bianco, S. A. McKeen, C. J. Senff, M. Trainer, S. C. Tucker, and R. J. Zamora. "Evaluation of urban surface parameterizations in the WRF model using measurements during the Texas Air Quality Study 2006 field campaign." Atmospheric Chemistry and Physics Discussions 10, no. 10 (October 26, 2010): 25033–80. http://dx.doi.org/10.5194/acpd-10-25033-2010.
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Abstract. The impact of urban surface parameterizations in the WRF (Weather Research and Forecasting) model on the simulation of local meteorological fields is investigated. The Noah land surface model (LSM), a modified LSM, and a single-layer urban canopy model (UCM) have been compared, focusing on urban patches. The model simulations were performed for 6 days from 12 August to 17 August during the Texas Air Quality Study 2006 field campaign. Analysis was focused on the Houston-Galveston metropolitan area. The model simulated temperature, wind, and atmospheric boundary layer (ABL) height were compared with observations from surface meteorological stations (Continuous Ambient Monitoring Stations, CAMS), wind profilers, the NOAA Twin Otter aircraft, and the NOAA Research Vessel Ronald H. Brown. The UCM simulation showed better results in the comparison of ABL height and surface temperature than the LSM simulations, whereas the original LSM overestimated both the surface temperature and ABL height significantly in urban areas. The modified LSM, which activates hydrological processes associated with urban vegetation mainly through transpiration, slightly reduced warm and high biases in surface temperature and ABL height. A comparison of surface energy balance fluxes in an urban area indicated the UCM reproduces a realistic partitioning of sensible heat and latent heat fluxes, consequently improving the simulation of urban boundary layer. However, the LSMs have a higher Bowen ratio than the observation due to significant suppression of latent heat flux. The comparison results suggest that the subgrid heterogeneity by urban vegetation and urban morphological characteristics should be taken into account along with the associated physical parameterizations for accurate simulation of urban boundary layer if the region of interest has a large fraction of vegetation within the urban patch. Model showed significant discrepancies in the specific meteorological conditions when nocturnal low-level jets exist and a thermal internal boundary layer over water forms.
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Yang, Jiachuan, Zhi-Hua Wang, Matei Georgescu, Fei Chen, and Mukul Tewari. "Assessing the Impact of Enhanced Hydrological Processes on Urban Hydrometeorology with Application to Two Cities in Contrasting Climates." Journal of Hydrometeorology 17, no. 4 (March 11, 2016): 1031–47. http://dx.doi.org/10.1175/jhm-d-15-0112.1.
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Abstract To enhance the capability of models in better characterizing the urban water cycle, physical parameterizations of urban hydrological processes have been implemented into the single-layer urban canopy model in the widely used Weather Research and Forecasting (WRF) Model. While the new model has been evaluated offline against field measurements at various cities, its performance in online settings via coupling to atmospheric dynamics requires further examination. In this study, the impact of urban hydrological processes on regional hydrometeorology of the fully integrated WRF–urban modeling system for two major cities in the United States, namely, Phoenix and Houston, is assessed. Results show that including hydrological processes improves prediction of the 2-m dewpoint temperature, an indicative measure of coupled thermal and hydrological processes. The implementation of green roof systems as an urban mitigation strategy is then tested at the annual scale. The reduction of environmental temperature and increase of humidity by green roofs indicate strong diurnal and seasonal variations and are significantly affected by geographical and climatic conditions. Comparison with offline studies reveals that land–atmosphere interactions play a crucial role in determining the effect of green roofs.
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Nemunaitis-Berry, Kodi L., Petra M. Klein, Jeffrey B. Basara, and Evgeni Fedorovich. "Sensitivity of Predictions of the Urban Surface Energy Balance and Heat Island to Variations of Urban Canopy Parameters in Simulations with the WRF Model." Journal of Applied Meteorology and Climatology 56, no. 3 (March 2017): 573–95. http://dx.doi.org/10.1175/jamc-d-16-0157.1.
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AbstractAs NWP and climate models continue to evolve toward finer grid spacing, efforts have been undertaken to better represent urban effects. For this study, the single-layer urban canopy model (SLUCM) of the High-Resolution Land Data Assimilation System (HRLDAS) and WRF Model was used to investigate the sensitivity of near-surface air temperatures and energy fluxes to SLUCM parameters in uncoupled (land) and coupled (land–atmosphere) predictions. Output from HRLDAS and WRF was compared with observations from the Oklahoma Mesonet and Joint Urban 2003 experiment. Variations in roof albedo (0.04–0.4) produced 40–135 W m−2 changes in net radiation and sensible heat fluxes. Sensible and ground heat fluxes varied by 40–100 W m−2 with changes in roof thermal conductivity (0.05–1.4). The urban fraction was found to be the only SLUCM parameter to significantly impact latent heat fluxes. Near-surface air temperatures, particularly during the daytime, did not show significant variations with SLUCM parameters (remaining within the 0.5-K range). Differences in urban air temperatures due to the change in boundary layer scheme were greater than the temperature changes due to SLUCM parameter variations. The sensitivity of near-surface air temperatures to SLUCM parameters depended on the method used to calculate the skin temperature of the impervious surface. For all simulations, predicted 2-m urban air temperatures were consistently higher than observations, with deviations approaching 8 K during the day and below 3 K at night. These large errors affected the model’s skill in reproducing the diurnal cycle of UHI intensity.
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Kusaka, Hiroyuki, and Fujio Kimura. "Thermal Effects of Urban Canyon Structure on the Nocturnal Heat Island: Numerical Experiment Using a Mesoscale Model Coupled with an Urban Canopy Model." Journal of Applied Meteorology 43, no. 12 (December 1, 2004): 1899–910. http://dx.doi.org/10.1175/jam2169.1.
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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.
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Hamdi, R., Daan Degrauwe, and P. Termonia. "Coupling the Town Energy Balance (TEB) Scheme to an Operational Limited-Area NWP Model: Evaluation for a Highly Urbanized Area in Belgium." Weather and Forecasting 27, no. 2 (April 1, 2012): 323–44. http://dx.doi.org/10.1175/waf-d-11-00064.1.
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Abstract The Town Energy Balance (TEB) single-layer scheme is implemented in a numerical weather prediction model running operationally at ~4-km resolution. The primary question addressed is the ability of TEB to function at this relatively coarse resolution and, thus, assessing its potential use in an operational configuration to improve sensible weather performance over Belgium. For this effort, simulations with and without TEB are first evaluated against 2-m observations and wind above the urban canopy for two months (January and July 2010). The results show that promising improvements are achieved by introducing TEB. The 2-m temperature and 2-m relative humidity improve compared to measurements in urban areas. The comparison of wind speed and wind direction above the urban canopy indicates that the structure of the flow in urban areas is better reproduced with TEB. It was found that the implementation of TEB results in an increase in winter precipitation over urban areas and downwind from urban areas, but during the summer TEB tended to cause rainfall to be locally concentrated and the total accumulated precipitation decreased obviously. Results from a 36-h case study during a high heat day with inland sea-breeze penetration (8 July 2010) indicate that the model satisfactorily captured the penetration of the sea breeze. In particular during the day, the TEB run shows a delay in the sea-breeze evolution compared to the operational run. During the night the results indicate that even at this coarse resolution, TEB is able to correctly reproduce the intensity of the observed urban heat island (UHI) of Brussels.
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Tan, Haochen, Pallav Ray, Mukul Tewari, James Brownlee, and Ajaya Ravindran. "Response of Near-Surface Meteorological Conditions to Advection under Impact of the Green Roof." Atmosphere 10, no. 12 (November 29, 2019): 759. http://dx.doi.org/10.3390/atmos10120759.
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Due to rapid urbanization, the near-surface meteorological conditions over urban areas are greatly modulated. To capture such modulations, sophisticated urban parameterizations with enhanced hydrological processes have been developed. In this study, we use the single-layer urban canopy model (SLUCM) available within the Weather Research and Forecasting (WRF) model to assess the response of near-surface temperature, wind, and moisture to advection under the impact of the green roof. An ensemble of simulations with different planetary boundary layer (PBL) schemes is conducted in the presence (green roof (GR)) and absence (control (CTL)) of green roof systems. Our results indicate that the near-surface temperature is found to be driven primarily by the surface heat flux with a minor influence from the zonal advection of temperature. The momentum budget analysis shows that both zonal and meridional momentum advection during the evening and early nighttime plays an important role in modulating winds over urban areas. The near-surface humidity remains nearly unchanged in GR compared to CTL, although the physical processes that determine the changes in humidity were different, in particular during the evening when the GR tends to have less moisture advection due to the reduced temperature gradient between the urban areas and the surroundings. Implications of our results are discussed.
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Tao, Sulin, and Yuhong Li. "Modeling Thermal Environment Responses to Terrain and Urbanization of Metropolis." Journal of Physics: Conference Series 2173, no. 1 (January 1, 2022): 012023. http://dx.doi.org/10.1088/1742-6596/2173/1/012023.
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Abstract Thermal environment responses to terrain and urbanization of Beijing, a metropolis of China, were simulated by the Weather Research and Forecasting model (WRF) with the single-layer Urban Canopy model (UCM). Four numerical experiments were designed: (1) the control experiment (Control exp), (2) no-terrain sensitive experiment (No-Terrain exp), (3) no-urban surface sensitive experiment (No-Urban exp), and (4) real land surface sensitive experiment (LU exp). Results indicate that better near-surface air temperature simulations were obtained after using MODIS land surface type product data MCD12Q1. The foehn effect due to northwestern mountains in Beijing were simulated to intensify the high temperature intensity in the plain area. Urban heat island effect existed in this area day and night, and the heat island intensity in the nighttime was obviously greater than that in the daytime. As a result of urbanization, the nighttime temperature had risen by 1.5∼3.5 °C and the expansion range of nighttime high temperature areas was basically consistent with the urban expansion range.
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Zhang, Ning, Yan Chen, Ling Luo, and Yongwei Wang. "Effectiveness of Different Urban Heat Island Mitigation Methods and Their Regional Impacts." Journal of Hydrometeorology 18, no. 11 (November 1, 2017): 2991–3012. http://dx.doi.org/10.1175/jhm-d-17-0049.1.
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Abstract Cool roofs and green roofs are two popular methods to mitigate the urban heat island and improve urban climates. The effectiveness of different urban heat island mitigation strategies in the summer of 2013 in the Yangtze River delta, China, is investigated using the Weather Research and Forecasting (WRF) Model coupled with a physically based single-layer urban canopy model. The modifications to the roof surface changed the urban surface radiation balance and then modified the local surface energy budget. Both cool roofs and green roofs led to a lower surface skin temperature and near-surface air temperature. Increasing the roof albedo to 0.5 caused a similar effectiveness as covering 25% of urban roofs with vegetation; increasing the roof albedo to 0.7 caused a similar near-surface air temperature decrease as 50% green roof coverage. The near-surface relative humidity increased in both cool roof and green roof experiments because of the combination of the impacts of increases in specific humidity and decreases in air temperature. The regional impacts of cool roofs and green roofs were evaluated using a regional effect index. A regional impact was found for near-surface air temperature and specific/relative humidity when the percentage of roofs covered with high-albedo materials or green roofs reached a higher fraction (greater than 50%). The changes in the vertical profiles of temperature cause a more stable atmospheric boundary layer over the urban area; at the same time, the crossover phenomena occurred above the boundary layer due to the decrease in vertical wind speed.
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Zhang, Hengyue, Menglin Jin, and Martin Leach. "A Study of the Oklahoma City Urban Heat Island Effect Using a WRF/Single-Layer Urban Canopy Model, a Joint Urban 2003 Field Campaign, and MODIS Satellite Observations." Climate 5, no. 3 (September 7, 2017): 72. http://dx.doi.org/10.3390/cli5030072.
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Lee, S. H., S. W. Kim, W. M. Angevine, L. Bianco, S. A. McKeen, C. J. Senff, M. Trainer, S. C. Tucker, and R. J. Zamora. "Evaluation of urban surface parameterizations in the WRF model using measurements during the Texas Air Quality Study 2006 field campaign." Atmospheric Chemistry and Physics 11, no. 5 (March 9, 2011): 2127–43. http://dx.doi.org/10.5194/acp-11-2127-2011.
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Abstract. The performance of different urban surface parameterizations in the WRF (Weather Research and Forecasting) in simulating urban boundary layer (UBL) was investigated using extensive measurements during the Texas Air Quality Study 2006 field campaign. The extensive field measurements collected on surface (meteorological, wind profiler, energy balance flux) sites, a research aircraft, and a research vessel characterized 3-dimensional atmospheric boundary layer structures over the Houston-Galveston Bay area, providing a unique opportunity for the evaluation of the physical parameterizations. The model simulations were performed over the Houston metropolitan area for a summertime period (12–17 August) using a bulk urban parameterization in the Noah land surface model (original LSM), a modified LSM, and a single-layer urban canopy model (UCM). The UCM simulation compared quite well with the observations over the Houston urban areas, reducing the systematic model biases in the original LSM simulation by 1–2 °C in near-surface air temperature and by 200–400 m in UBL height, on average. A more realistic turbulent (sensible and latent heat) energy partitioning contributed to the improvements in the UCM simulation. The original LSM significantly overestimated the sensible heat flux (~200 W m−2) over the urban areas, resulting in warmer and higher UBL. The modified LSM slightly reduced warm and high biases in near-surface air temperature (0.5–1 °C) and UBL height (~100 m) as a result of the effects of urban vegetation. The relatively strong thermal contrast between the Houston area and the water bodies (Galveston Bay and the Gulf of Mexico) in the LSM simulations enhanced the sea/bay breezes, but the model performance in predicting local wind fields was similar among the simulations in terms of statistical evaluations. These results suggest that a proper surface representation (e.g. urban vegetation, surface morphology) and explicit parameterizations of urban physical processes are required for accurate urban atmospheric numerical modeling.
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Hamdi, R., and V. Masson. "Inclusion of a Drag Approach in the Town Energy Balance (TEB) Scheme: Offline 1D Evaluation in a Street Canyon." Journal of Applied Meteorology and Climatology 47, no. 10 (October 1, 2008): 2627–44. http://dx.doi.org/10.1175/2008jamc1865.1.
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Abstract The Town Energy Balance module bridges the micro- and mesoscale and simulates local-scale urban surface energy balance for use in mesoscale meteorological models. Previous offline evaluations show that this urban module is able to simulate in good behavior road, wall, and roof temperatures and to correctly partition radiation forcing into turbulent and storage heat fluxes. However, to improve prediction of the meteorological fields inside the street canyon, a new version has been developed, following the methodology described in a companion paper by Masson and Seity. It resolves the surface boundary layer inside and above urban canopy by introducing a drag force approach to account for the vertical effects of buildings. This new version is tested offline, with one-dimensional simulation, in a street canyon using atmospheric and radiation data recorded at the top of a 30-m-high tower as the upper boundary conditions. Results are compared with simulations using the original single-layer version of the Town Energy Balance module on one hand and with measurements within and above a street canyon on the other hand. Measurements were obtained during the intensive observation period of the Basel Urban Boundary Layer Experiment. Results show that this new version produces profiles of wind speed, friction velocity, turbulent kinetic energy, turbulent heat flux, and potential temperature that are more consistent with observations than with the single-layer version. Furthermore, this new version can still be easily coupled to mesoscale meteorological models.
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Yang, Long, James A. Smith, Mary Lynn Baeck, Elie Bou-Zeid, Stephen M. Jessup, Fuqiang Tian, and Heping Hu. "Impact of Urbanization on Heavy Convective Precipitation under Strong Large-Scale Forcing: A Case Study over the Milwaukee–Lake Michigan Region." Journal of Hydrometeorology 15, no. 1 (February 1, 2014): 261–78. http://dx.doi.org/10.1175/jhm-d-13-020.1.
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Abstract In this study, observational and numerical modeling analyses based on the Weather Research and Forecasting Model (WRF) are used to investigate the impact of urbanization on heavy rainfall over the Milwaukee–Lake Michigan region. The authors examine urban modification of rainfall for a storm system with continental-scale moisture transport, strong large-scale forcing, and extreme rainfall over a large area of the upper Midwest of the United States. WRF simulations were carried out to examine the sensitivity of the rainfall distribution in and around the urban area to different urban land surface model representations and urban land-use scenarios. Simulation results suggest that urbanization plays an important role in precipitation distribution, even in settings characterized by strong large-scale forcing. For the Milwaukee–Lake Michigan region, the thermodynamic perturbations produced by urbanization on the temperature and surface pressure fields enhance the intrusion of the lake breeze and facilitate the formation of a convergence zone, which create favorable conditions for deep convection over the city. Analyses of model and observed vertical profiles of reflectivity using contoured frequency by altitude displays (CFADs) suggest that cloud dynamics over the city do not change significantly with urbanization. Simulation results also suggest that the large-scale rainfall pattern is not sensitive to different urban representations in the model. Both urban representations, the Noah land surface model with urban land categories and the single-layer urban canopy model, adequately capture the dominant features of this storm over the urban region.
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Liu, Chao, Qian Shu, Sen Huang, and Jingwei Guo. "Modeling the Impacts of City-Scale “Ventilation Corridor” Plans on Human Exposure to Intra-Urban PM2.5 Concentrations." Atmosphere 12, no. 10 (September 29, 2021): 1269. http://dx.doi.org/10.3390/atmos12101269.
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Increasingly, Chinese cities are proposing city-scale ventilation corridors (VCs) to strengthen wind velocities and decrease pollution concentrations, although their influences are ambiguous. To assess VC impacts, an effort has been made to predict the impact of VC solutions in the high density and diverse land use of the coastal city of Shanghai, China, in this paper. One base scenario and three VC scenarios, with various VC widths, locations, and densities, were first created. Then, the combination of the Weather Research and Forecasting/Single-Layer Urban Canopy Model (WRFv.3.4/UCM) and Community Multiscale Air Quality (CMAQv.5.0.1) numerical simulation models were employed to comprehensively evaluate the impacts of urban spatial form and VC plans on PM2.5 concentrations. The modeling results indicated that concentrations increased within the VCs in both summer and winter, and the upwind concentration decreased in winter. These counter-intuitive results could be explained by decreased planetary boundary layer (PBL), roughness height, deposition rate, and wind speeds induced by land use and urban height modifications. PM2.5 deposition flux decreased by 15–20% in the VCs, which was attributed to the roughness height decrease for it weakens aerodynamic resistance (Ra). PBL heights within the VCs decreased 15–100 m, and the entire Shanghai’s PBL heights also decreased in general. The modeling results suggest that VCs may not be as functional as certain urban planners have presumed.
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Kuik, Friderike, Axel Lauer, Galina Churkina, Hugo A. C. Denier van der Gon, Daniel Fenner, Kathleen A. Mar, and Tim M. Butler. "Air quality modelling in the Berlin–Brandenburg region using WRF-Chem v3.7.1: sensitivity to resolution of model grid and input data." Geoscientific Model Development 9, no. 12 (December 5, 2016): 4339–63. http://dx.doi.org/10.5194/gmd-9-4339-2016.
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Abstract. Air pollution is the number one environmental cause of premature deaths in Europe. Despite extensive regulations, air pollution remains a challenge, especially in urban areas. For studying summertime air quality in the Berlin–Brandenburg region of Germany, the Weather Research and Forecasting Model with Chemistry (WRF-Chem) is set up and evaluated against meteorological and air quality observations from monitoring stations as well as from a field campaign conducted in 2014. The objective is to assess which resolution and level of detail in the input data is needed for simulating urban background air pollutant concentrations and their spatial distribution in the Berlin–Brandenburg area. The model setup includes three nested domains with horizontal resolutions of 15, 3 and 1 km and anthropogenic emissions from the TNO-MACC III inventory. We use RADM2 chemistry and the MADE/SORGAM aerosol scheme. Three sensitivity simulations are conducted updating input parameters to the single-layer urban canopy model based on structural data for Berlin, specifying land use classes on a sub-grid scale (mosaic option) and downscaling the original emissions to a resolution of ca. 1 km × 1 km for Berlin based on proxy data including traffic density and population density. The results show that the model simulates meteorology well, though urban 2 m temperature and urban wind speeds are biased high and nighttime mixing layer height is biased low in the base run with the settings described above. We show that the simulation of urban meteorology can be improved when specifying the input parameters to the urban model, and to a lesser extent when using the mosaic option. On average, ozone is simulated reasonably well, but maximum daily 8 h mean concentrations are underestimated, which is consistent with the results from previous modelling studies using the RADM2 chemical mechanism. Particulate matter is underestimated, which is partly due to an underestimation of secondary organic aerosols. NOx (NO + NO2) concentrations are simulated reasonably well on average, but nighttime concentrations are overestimated due to the model's underestimation of the mixing layer height, and urban daytime concentrations are underestimated. The daytime underestimation is improved when using downscaled, and thus locally higher emissions, suggesting that part of this bias is due to deficiencies in the emission input data and their resolution. The results further demonstrate that a horizontal resolution of 3 km improves the results and spatial representativeness of the model compared to a horizontal resolution of 15 km. With the input data (land use classes, emissions) at the level of detail of the base run of this study, we find that a horizontal resolution of 1 km does not improve the results compared to a resolution of 3 km. However, our results suggest that a 1 km horizontal model resolution could enable a detailed simulation of local pollution patterns in the Berlin–Brandenburg region if the urban land use classes, together with the respective input parameters to the urban canopy model, are specified with a higher level of detail and if urban emissions of higher spatial resolution are used.
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Ryu, Young-Hee, and Jong-Jin Baik. "Quantitative Analysis of Factors Contributing to Urban Heat Island Intensity." Journal of Applied Meteorology and Climatology 51, no. 5 (May 2012): 842–54. http://dx.doi.org/10.1175/jamc-d-11-098.1.
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AbstractThis study identifies causative factors of the urban heat island (UHI) and quantifies their relative contributions to the daytime and nighttime UHI intensities using a mesoscale atmospheric model that includes a single-layer urban canopy model. A midlatitude city and summertime conditions are considered. Three main causative factors are identified: anthropogenic heat, impervious surfaces, and three-dimensional (3D) urban geometry. Furthermore, the 3D urban geometry factor is subdivided into three subfactors: additional heat stored in vertical walls, radiation trapping, and wind speed reduction. To separate the contributions of the factors and interactions between the factors, a factor separation analysis is performed. In the daytime, the impervious surfaces contribute most to the UHI intensity. The anthropogenic heat contributes positively to the UHI intensity, whereas the 3D urban geometry contributes negatively. In the nighttime, the anthropogenic heat itself contributes most to the UHI intensity, although it interacts strongly with other factors. The factor that contributes the second most is the impervious-surfaces factor. The 3D urban geometry contributes positively to the nighttime UHI intensity. Among the 3D urban geometry subfactors, the additional heat stored in vertical walls contributes most to both the daytime and nighttime UHI intensities. Extensive sensitivity experiments to anthropogenic heat intensity and urban surface parameters show that the relative importance and ranking order of the contributions are similar to those in the control experiment.
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Adachi, Sachiho A., Fujio Kimura, Hiroyuki Kusaka, Michael G. Duda, Yoshiki Yamagata, Hajime Seya, Kumiko Nakamichi, and Toshinori Aoyagi. "Moderation of Summertime Heat Island Phenomena via Modification of the Urban Form in the Tokyo Metropolitan Area." Journal of Applied Meteorology and Climatology 53, no. 8 (August 2014): 1886–900. http://dx.doi.org/10.1175/jamc-d-13-0194.1.
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AbstractThis study investigated the moderation of the urban heat island via changes in the urban form in the Tokyo metropolitan area (TMA). Two urban scenarios with the same population as that of the current urban form were used for sensitivity experiments: the dispersed-city and compact-city scenarios. Numerical experiments using the two urban scenarios as well as an experiment using the current urban form were conducted using a regional climate model coupled with a single-layer urban canopy model. The averaged nighttime surface air temperature in TMA increased by ~0.34°C in the dispersed-city scenario and decreased by ~0.1°C in the compact-city scenario. Therefore, the compact-city scenario had significant potential for moderating the mean areal heat-island effect in the entire TMA. Alternatively, in the central part of the TMA, these two urban-form scenarios produced opposite effects on the surface air temperature; that is, severe thermal conditions worsened further in the compact-city scenario because of the denser population. This result suggests that the compact-city form is not always appropriate for moderation of the urban-heat-island effect. This scenario would need to combine with other mitigation strategies, such as the additional greening of urban areas, especially in the central area. This study suggests that it is important to design a plan to adapt to higher urban temperatures, which are likely to ensue from future global warming and the urban heat island, from several perspectives; that is, designs should take into account not only climatological aspects but also impacts on urban inhabitants.
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Miao, Shiguang, Fei Chen, Qingchun Li, and Shuiyong Fan. "Impacts of Urban Processes and Urbanization on Summer Precipitation: A Case Study of Heavy Rainfall in Beijing on 1 August 2006." Journal of Applied Meteorology and Climatology 50, no. 4 (April 2011): 806–25. http://dx.doi.org/10.1175/2010jamc2513.1.
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AbstractFinescale simulations (with 500-m grid spacing) using the Weather Research and Forecasting Model (WRF) were used to investigate impacts of urban processes and urbanization on a localized, summer, heavy rainfall in Beijing. Evaluation using radar and gauge data shows that this configuration of WRF with three-dimensional variational data assimilation of local weather and GPS precipitable water data can simulate this event generally well. Additional WRF simulations were conducted to test the sensitivity of simulation of this storm to different urban processes and urban land-use scenarios. The results confirm that the city does play an important role in determining storm movement and rainfall amount. Comparison of cases with and without the presence of the city of Beijing with respect to the approaching storm shows that the urban effect seems to lead to the breaking of the squall line into convective cells over the urban area. The change of precipitation amount depends on the degree of urbanization (i.e., the change over time in the extent of Beijing city). Model results show that an early urbanization prior to 1980 decreases the maximum rainfall, whereas further urbanization in Beijing is conducive to bifurcating the path of rainfall. According to sensitivity results with a single-layer urban canopy model, the thermal transport (sensible and latent heating) induced by the presence of an urban area apparently is more important than associated momentum transport, with latent and sensible heating apparently having equally important roles in the modification of simulated precipitation. Urban surfaces tend to cause the rainfall to be more locally concentrated. High-rise urban cores may bifurcate the path of rainfall as well as increase the area percentage of heavy rainfall.