Solar Radiation and Urban Heat Islands

Terjung, Werner H.; Louie, Stella S‐F.

doi:10.1111/j.1467-8306.1973.tb00918.x

Cited by 79 publications

(26 citation statements)

References 1 publication

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“…However, evidence indicating the importance of urban geometry to the creation and the magnitude of the UHI phenomenon began to accumulate in the 1970s. Terjung & Louie (1973) were among the first to suggest that the urban-rural daytime temperature anomaly is largely attributable to the aspect of vertical surfaces to the sun.…”

Section: Urban Morphology and Climatementioning

confidence: 99%

Influence of urban morphology and sea breeze on hot humid microclimate: the case of Colombo, Sri Lanka

Emmanuel¹,

Johansson

2006

Clim. Res.

149

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Urbanisation leads to increased thermal stress in hot-humid climates due to increased surface and air temperatures and reduced wind speed. We examined the influence of urban morphology and sea breeze on the microclimate of Colombo, Sri Lanka. Air and surface temperatures, humidity and wind speed were measured at 1 rural and 5 urban sites during the warmest season. The urban sites differed in their height to width (H/W) ratio, ground cover and distance to the sea. Intra-urban air temperature differences were greatest during the daytime. A maximum intra-urban difference of 7 K was recorded on clear days. Maximum temperatures tended to decrease with increasing H/W ratio and proximity to the sea. All urban sites experienced a nocturnal urban heat island (UHI) when the sky was clear or partly cloudy. The temperature differences between sunlit and shaded urban surfaces reached 20 K, which shows the importance of shade in urban canyons (reducing long-wave radiation from surfaces). Within the urban areas, the vapour pressure was high (> 30 hPa) and showed little diurnal variation. Wind speeds were low (< 2 m s -1) and tended to decrease with increasing H/W ratio. Shading is proposed as the main strategy for lowering air and radiant temperatures; this can be achieved by deeper canyons, covered walkways and shade trees. It is also suggested to open up wind corridors perpendicular to the sea to facilitate deeper sea breeze penetration.KEY WORDS: Urban geometry · Tropical climate · Climate-sensitive urban design · Urban heat island · Coastal city structure Resale or republication not permitted without written consent of the publisher

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Section: Urban Morphology and Climatementioning

confidence: 99%

Influence of urban morphology and sea breeze on hot humid microclimate: the case of Colombo, Sri Lanka

Emmanuel¹,

Johansson

2006

Clim. Res.

149

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“…The latter strongly correlates spatially with absorbed solar radiation. Such a 'doughnut effect' has previously been reported by Ludwig (1970) and Terjung and Louie (1973). This does not predict a complete maximum heating ring, but distinctive areas of strong convection occur along most margins of downtown.…”

Section: Of the City's Energy Budgetmentioning

confidence: 66%

Simulating the causal elements of urban heat islands

Terjung

O’Rourke

1980

Boundary-Layer Meteorol

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A comparison was made between the resultant surface temperatures and sensible heat fluxes of building interfaces calculated by steady-state and transient (implicit) methods. Both procedures used identical environmental (summer and winter) input. For exterior conditions, the results indicated that the correlation between the two methods is sufficiently large, enabling them to be used interchangeably for the spatial analysis of urban canopy layers of entire cities. Using a steady-state approach as a surrogate for unsteady conditions, computer resources can be saved up to a factor of ten. An urban energy budget model (URBAN 3) has been used to demonstrate that the distribution of sensible heat flux and net longwave radiation -the prime causes of urban heat-island generation -was far from the homogeneity assumed in many macroscopic models or even some street-level studies. The individual emanations of reradiation and sensible heat flux showed different diurnal and spatial patterns. Under the input scenarios used, daytime heat islands assumed a 'doughnut' shape in the inner city. It is believed that many of the lower boundary conditions used in macroscopic numerical models are inadequate in light of this study.

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“…It has been shown that the ratio between solar radiation absorbed by threedimensional building systems and two-dimensional horizontal surfaces under cloudless conditions varies considerably with latitude and season [ 17]. Fig.…”

Section: Concrete Plain Versus Canopy Plainmentioning

confidence: 99%

Urban parks, energy budgets, and surface temperatures

O’Rourke

Terjung

1981

Arch. Met. Geoph. Biocl., Ser. B

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SummaryThis paper deals with the results of the combination of two deterministic models: a multi-layered canopy leaf energy budget model CANOPY and a complex street canyon energy budget model URBAN 3. Both models were validated previously. In comparing the effect of street parks and roof gardens in contrast to non-vegetated city blocks, four typical urban morphologies were created, ranging from high-rise structures to low buildings and combinations thereof. These building systems were exposed to typical summer and winter scenarios for three latitudes. The simulations indicated a variety of increases in absorbed shortwave radiation and net radiation, and decreases in sensible heat flux and system reradiation compared to non-vegetated environments. It is believed that the discussed features represent generalized limits of the possible effect of adding vegetatived surface covers to non-vegetated city blocks. Zusammenfassung Stadtparks, Energiebudgets und OberflfichentemperaturenIn dieser Arbeit werden die Ergebnisse der Kombination yon zwei Modellen mitgeteilt: eines Energiebudgetmodells CANOPY f0r eine mehrschichtige Vegetationsdecke und eines Energiebudgetmodells URBAN 3 f0r einen komplexen Strafienzug. FOr den Vergleich des Einflusses yon bewachsenen Stra~en und Dachg~irten im Gegensatz zu nicht bewachsenen H~userblocks werden vier typische Stadtformen, reichend yon HochhausStrukturen his zu niedrigen GeNiuden und deren Kombination zugrdnde gelegt. Diese Gebfiudesysteme werden typischen Sommer-und Winterverh~ltnissen in drei geographischen Breiten ansgesetzt. Diese Simulationen zeigten im Vergleich mit unbewachsener Umgebung eine Verschiedenheit in der Zunahme yon absorbierter kurzwelliger Strahlung und Strahlungsbilanz und in einer Abnahme des sensiblen W~irmeflusses und der Riickstrah]ung. Es wird angenommen, daft die besprochenen Merkmale verallgemeinerte Grenzen for die m6gliche Wirkung der Anlage yon Vegetationsfl~ichen zu nicht bewachsenen HSuserblocks anzeigen.

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Solar Radiation and Urban Heat Islands

Cited by 79 publications

References 1 publication

Influence of urban morphology and sea breeze on hot humid microclimate: the case of Colombo, Sri Lanka

Influence of urban morphology and sea breeze on hot humid microclimate: the case of Colombo, Sri Lanka

Simulating the causal elements of urban heat islands

Urban parks, energy budgets, and surface temperatures

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