A k - *epsiv Turbulence Closure Model For The Atmospheric Boundary Layer Including Urban Canopy

Ca, Vu Thanh; Ashie, Yasunobu; Asaeda, Takashi

doi:10.1023/a:1013878907309

Cited by 47 publications

(10 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, in a city buildings can occupy a significant fraction of the total volume, which typically results in a reduction of the outdoor air volume with depth. In a city, the changes of the fractional volume with height must be taken into account (Ca et al 2002). This is reflected in Eq.…”

Section: The Horizontally-averaged Tke Budgetmentioning

confidence: 99%

The Budget of Turbulent Kinetic Energy in the Urban Roughness Sublayer

Christen

Rotach

Vogt

2009

Boundary-Layer Meteorol

View full text Add to dashboard Cite

Full-scale observations from two urban sites in Basel, Switzerland were analysed to identify the magnitude of different processes that create, relocate, and dissipate turbulent kinetic energy (TKE) in the urban atmosphere. Two towers equipped with a profile of six ultrasonic anemometers each sampled the flow in the urban roughness sublayer, i.e. from street canyon base up to roughly 2.5 times the mean building height. This observational study suggests a conceptual division of the urban roughness sublayer into three layers: (1) the layer above the highest roofs, where local buoyancy production and local shear production of TKE are counterbalanced by local viscous dissipation rate and scaled turbulence statistics are close to to surface-layer values; (2) the layer around mean building height with a distinct inflexional mean wind profile, a strong shear and wake production of TKE, a more efficient turbulent exchange of momentum, and a notable export of TKE by transport processes; (3) the lower street canyon with imported TKE by transport processes and negligible local production. Averaged integral velocity variances vary significantly with height in the urban roughness sublayer and reflect the driving processes that create or relocate TKE at a particular height. The observed profiles of the terms of the TKE budget and the velocity variances show many similarities to observations within and above vegetation canopies.

show abstract

Section: The Horizontally-averaged Tke Budgetmentioning

confidence: 99%

The Budget of Turbulent Kinetic Energy in the Urban Roughness Sublayer

Christen

Rotach

Vogt

2009

Boundary-Layer Meteorol

View full text Add to dashboard Cite

show abstract

“…The second one is to use a single-layer urban canopy formulation Johnson et al 1991;Mills 1993;Masson 2000;Kusaka et al 2001) based on a single vegetation model (Deardorff 1978;Dickinson et al 1986;Sellers et al 1986;Lee and Pielke 1992;Sellers et al 1996;Dickinson et al 1998;Walko et al 2000). The third one is to use a multi-layer urban canopy model with a mesoscale meteorological model (Brown 2000;Ca et al 2002;Martilli et al 2002;Otte et al 2004;Dupont et al 2004).…”

Section: Introductionmentioning

confidence: 99%

A Vegetated Urban Canopy Model for Meteorological and Environmental Modelling

Lee

Park

2007

Boundary-Layer Meteorol

149

158

View full text Add to dashboard Cite

An urban canopy model is developed for use in mesoscale meteorological and environmental modelling. The urban geometry is composed of simple homogeneous buildings characterized by the canyon aspect ratio (h/w) as well as the canyon vegetation characterized by the leaf aspect ratio (σ l ) and leaf area density profile. Five energy exchanging surfaces (roof, wall, road, leaf, soil) are considered in the model, and energy conservation relations are applied to each component. In addition, the temperature and specific humidity of canopy air are predicted without the assumption of thermal equilibrium. For radiative transfer within the canyon, multiple reflections for shortwave radiation and one reflection for longwave radiation are considered, while the shadowing and absorption of radiation due to the canyon vegetation are computed by using the transmissivity and the leaf area density profile function. The model is evaluated using field measurements in Vancouver, British Columbia and Marseille, France. Results show that the model quite well simulates the observations of surface temperatures, canopy air temperature and specific humidity, momentum flux, net radiation, and energy partitioning into turbulent fluxes and storage heat flux. Sensitivity tests show that the canyon vegetation has a large influence not only on surface temperatures but also on the partitioning of sensible and latent heat fluxes. In addition, the surface energy balance can be affected by soil moisture content and leaf area index as well as the fraction of vegetation. These results suggest that a proper parameterization of the canyon vegetation is prerequisite for urban modelling.

show abstract

“…These models have been shown to accurately predict surface fluxes, temperatures, and net radiation for case studies of UHIs (Kusaka et al 2001). Multilayer schemes include Brown and Williams (1998), Vu et al (1999), Ca et al (2002), Martilli et al (2002), and Chin et al (2005). These schemes can be as simple as modifications to predictive equations to include urban effects (i.e., Brown and Williams 1998;Chin et al 2005) or more detailed to include predictive equations for roof and wall values, incorporating complex radiative effects such as shadowing and reflection at multiple levels within the urban canopy (i.e., Kusaka et al 2001;Martilli et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Urban Canopy Modeling of the New York City Metropolitan Area: A Comparison and Validation of Single- and Multilayer Parameterizations

Holt¹,

Pullen²

2007

Monthly Weather Review

110

View full text Add to dashboard Cite

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 (Ϫ0.10°C for W-UCM versus Ϫ0.82°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 ϳ300 versus 100 W m Ϫ2 ), 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 Ͻ 0.1 m 2 s Ϫ2 ). 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.

show abstract

A k - *epsiv Turbulence Closure Model For The Atmospheric Boundary Layer Including Urban Canopy

Cited by 47 publications

References 65 publications

The Budget of Turbulent Kinetic Energy in the Urban Roughness Sublayer

The Budget of Turbulent Kinetic Energy in the Urban Roughness Sublayer

A Vegetated Urban Canopy Model for Meteorological and Environmental Modelling

Urban Canopy Modeling of the New York City Metropolitan Area: A Comparison and Validation of Single- and Multilayer Parameterizations

Contact Info

Product

Resources

About