Temporal dynamics of the urban heat island of Singapore

Abstract

The temporal variability of the canopy-level urban heat island (UHI) of Singapore is examined for different temporal scales on the basis of observations during a 1-year period. Temperature data obtained from different urban areas (commercial, Central Business District (CBD), high-rise and low-rise housing) are compared with 'rural' reference data and analysed with respect to meteorological variables and differences in land use. The results indicate that the peak UHI magnitude occurs 3-4 h (>6 h) after sunset in the commercial area, (at other urban sites). Higher UHI intensities generally occur during the southwest monsoon period of May-August, with a maximum of ∼7°C observed in the commercial area under ideal meteorological conditions. Variations in seasonal precipitation explain some of the differences in urban-rural cooling. No clear relationship between urban geometry and UHI intensity can be seen, and intra-urban variations of temperature are also shown to be influenced by other site factors, e.g. the extent of green space and anthropogenic heat. Lastly, results from the present study are compared with UHI data from other tropical and mid-latitude cities.

Evening evapotranspirative cooling in relation to vegetation and urban geometry in the city of Ouagadougou, Burkina Faso

“…The twophase cooling is also clearly seen in the data from wettropical Singapore (Chow and Roth, 2006). Two-phase cooling thus appears to be a common phenomenon of nocturnal cooling independent of the climate zone.…”

“…Later, cooling rates decreased and showed a similar, decreasing pattern at all sites throughout the night. Intraurban comparisons also showed a similar pattern with two different cooling phases (Upmanis et al, 1998;Chow and Roth, 2006;Erell and Williamson, 2007;Holmer et al, 2007). Holmer et al (2007) proposed that site-dependent differential cooling around sunset was dominated by radiative divergence and sensible heat flux cooling, which both are influenced by the geometry of the buildings that can be expressed as the SVF.…”

“…Many (sub)tropical cities show a clear seasonal difference in NUHI intensities, with 0.5-3 K lower intensity during the wet season compared to the dry season (Okoola, 1990;Jauregui et al, 1992;Jauregui, 1997;Robaa, 2003;Jonsson, 2004;Chow and Roth, 2006;Roth, 2007;Balogun et al, 2009). The lower NUHI intensities during the wet season are explained by the higher amount of cloud cover, but also by thermal admittance due to increased soil-water (Jauregui, 1997;Jonsson, 2004;Jonsson and Lindqvist, 2005;Roth, 2007).…”

Correlation or Causality between Land Cover Patterns and the Urban Heat Island Effect? Evidence from Brisbane, Australia

“…These studies, however, made no effort to draw quantitative inferences between changes in land cover types and UHI differences. Moreover, although previous researchers have identified that the seasonal/diurnal variations have a significant effect in measuring UHI [30][31][32], this critical factor has been generally overlooked within existing longitudinal studies. Therefore, studies examining a quantitative causal link between land cover patterns and the UHI effect at the surface layer are relatively scarce.…”

Intra‐urban differences in canopy layer air temperature at a mid‐latitude city

“…An UHI has also been recorded in Singapore (Goh and Chang, 1999;Chow and Roth, 2006), where high atmospheric humidity and the frequent presence of low, warm clouds result in conditions that do not favor the development of rapid nocturnal cooling associated with heat islands in other climates. The development of an UHI when a new city is founded on a greenfield site, i.e.…”