Numerical Study of the Daytime Planetary Boundary Layer over an Idealized Urban Area: Influence of Surface Properties, Anthropogenic Heat Flux, and Geostrophic Wind Intensity

Falasca, Serena; Catalano, Franco; Moroni, Monica

doi:10.1175/jamc-d-15-0135.1

Cited by 20 publications

(10 citation statements)

References 40 publications

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“…Our results indicate that parameterizing albedo in urban climate modeling using generalized values for different LULC classes can result in considerable error given the wide range of albedo values measured between classes. The net change in albedo in the most intensively urbanized areas may be considerably smaller and more varied over space than has been assumed in some numerical modeling approaches for urban climate (e.g., Falasca et al, 2016). Analysis of trends between albedo and other land cover metrics in the study area show that on a regional basis (several kilometer scale) albedo gradients across an urban-rural gradient may be broadly predicted, opening the potential for further study on the implications for surface energy balance of urban land expansion (Reinmann et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

“…Studies of the UHI using remote sensing data at <3 m resolution is becoming increasingly possible (Zhang et al, ) and retrieval of urban albedo is possible at similar resolution (Kaplan et al, ). Incorporation of high‐resolution albedo and other land cover data, such as vegetated and impervious fractional coverage, into urban surface energy exchange models has been shown to improve agreement with observed surface temperature and evapotranspiration flux (Vahmani & Hogue, ), and current large‐eddy models rely on land cover parameters, including albedo, specified at high spatial resolution (Falasca et al, ). Recent work has used very high‐resolution remote sensing data to characterize albedo variation among different roof styles to improve urban climate model accuracy (Ban‐Weiss et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Albedo, Land Cover, and Daytime Surface Temperature Variation Across an Urbanized Landscape

et al. 2017

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Land surface albedo is a key parameter controlling the local energy budget, and altering the albedo of built surfaces has been proposed as a tool to mitigate high near‐surface temperatures in the urban heat island. However, most research on albedo in urban landscapes has used coarse‐resolution data, and few studies have attempted to relate albedo to other urban land cover characteristics. This study provides an empirical description of urban summertime albedo using 30 m remote sensing measurements in the metropolitan area around Boston, Massachusetts, relating albedo to metrics of impervious cover fraction, tree canopy coverage, population density, and land surface temperature (LST). At 30 m spatial resolution, median albedo over the study area (excluding open water) was 0.152 (0.112–0.187). Trends of lower albedo with increasing urbanization metrics and temperature emerged only after aggregating data to 500 m or the boundaries of individual towns, at which scale a −0.01 change in albedo was associated with a 29 (25–35)% decrease in canopy cover, a 27 (24–30)% increase in impervious cover, and an increase in population from 11 to 386 km−2. The most intensively urbanized towns in the region showed albedo up to 0.035 lower than the least urbanized towns, and mean mid‐morning LST 12.6°C higher. Trends in albedo derived from 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) measurements were comparable, but indicated a strong contribution of open water at this coarser resolution. These results reveal linkages between albedo and urban land cover character, and offer empirical context for climate resilient planning and future landscape functional changes with urbanization.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Albedo, Land Cover, and Daytime Surface Temperature Variation Across an Urbanized Landscape

et al. 2017

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“…Since this phenomenon influences the climate data employed by EnergyPlus for the calculation of the energy performance of buildings, the WRF model was used for the creation of an input climate file taking into account the built environment of the city. Previous works demonstrated the ability of the WRF model to simulate idealized and real urban heat islands [56,57].…”

Section: The Case Studymentioning

confidence: 99%

Influence of Input Climatic Data on Simulations of Annual Energy Needs of a Building: EnergyPlus and WRF Modeling for a Case Study in Rome (Italy)

et al. 2018

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The simulation of the energy consumptions in an hourly regime is necessary in order to perform calculations on residential buildings of particular relevance for volume or for architectural features. In such cases, the simplified methodology provided by the regulations may be inadequate, and the use of software like EnergyPlus is needed. To obtain reliable results, usually, significant time is spent on the meticulous insertion of the geometrical inputs of the building, together with the properties of the envelope materials and systems. Less attention is paid to the climate database. The databases available on the EnergyPlus website refer to airports located in rural areas near major cities. If the building to be simulated is located in a metropolitan area, it may be affected by the local heat island, and the database used as input to the software should take this phenomenon into account. To this end, it is useful to use a meteorological model such as the Weather Research and Forecasting (WRF) model to construct an appropriate input climate file. A case study based on a building located in the city center of Rome (Italy) shows that, if the climatic forcing linked to the heat island is not considered, the estimated consumption due to the cooling is underestimated by 35–50%. In particular, the analysis and the seasonal comparison between the energy needs of the building simulated by EnergyPlus, with the climatic inputs related to two airports in the rural area of Rome and with the inputs provided by the WRF model related to the center of Rome, show discrepancies of about (i) WRF vs. Fiumicino (FCO): Δ = −3.48% for heating, Δ = 49.25% for cooling; (ii) WRF vs. Ciampino (CIA): Δ = −7.38% for heating, Δ = +35.52% for cooling.

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“…UHIs produce changes in the structure of the atmospheric boundary layer [4,5] and in the local atmospheric dynamic, showing a typical circulation characterized by a convergent flow towards the urban area near the ground and a diverging flow at upper levels [5,6]. This, together with the alteration of the thermal field, significantly influences the formation and the dispersion of pollutants [7,8].…”

Section: Introductionmentioning

confidence: 99%

Impact of Highly Reflective Materials on Meteorology, PM10 and Ozone in Urban Areas: A Modeling Study with WRF-CHIMERE at High Resolution over Milan (Italy)

Falasca

Curci

2018

Urban Science

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Abstract:The Urban Heat Island (UHI) is a well-known phenomenon concerning an increasing percentage of the world's population due to the growth rates of metropolitan areas. Given the health and economic implications of UHIs, several mitigation techniques are being evaluated and tested. In this study, we consider the use of highly reflective materials for urban surfaces, and we carried out numerical experiments using the Weather Research and Forecasting model coupled with the CHIMERE model in order to investigate the effects of these materials on the meteorology and air quality in the urban area of Milan (Italy). Results show that an increase in albedo from 0.2 to 0.7 for urban roofs, walls and streets leads to a decrease in UHI intensity by up to 2-3 • C and of the planetary boundary layer (PBL) height of about 500 m. However, the difference of PM10 and ozone between urban and surrounding areas increases by a factor of about 2, attributable to the reduction of PBL height and wind speed and to the increased reflected solar radiation that may enhance photochemical production during the daytime. Therefore, if anthropogenic emissions are held at the same levels, the potential benefit to the UHI in terms of thermal discomfort may have negative repercussions on air quality.

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Numerical Study of the Daytime Planetary Boundary Layer over an Idealized Urban Area: Influence of Surface Properties, Anthropogenic Heat Flux, and Geostrophic Wind Intensity

Cited by 20 publications

References 40 publications

Albedo, Land Cover, and Daytime Surface Temperature Variation Across an Urbanized Landscape

Albedo, Land Cover, and Daytime Surface Temperature Variation Across an Urbanized Landscape

Influence of Input Climatic Data on Simulations of Annual Energy Needs of a Building: EnergyPlus and WRF Modeling for a Case Study in Rome (Italy)

Impact of Highly Reflective Materials on Meteorology, PM10 and Ozone in Urban Areas: A Modeling Study with WRF-CHIMERE at High Resolution over Milan (Italy)

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