Winston Chow & Siti Nur 'Assyakirin Ali Akbar, National University of Singapore, Kent Ridge, Singapore

Presentation Title: Influence of land cover on micro-scale outdoor human thermal comfort in a tropical city




Urbanization alters the physical environment over a multitude of spatial scales, with great implications towards human thermal comfort. Elevated temperatures arising from the urban heat island and from global climate change would likely increase thermal discomfort for urban residents. Despite this, the quantification of urban outdoor thermal comfort (OTC) presents a relatively new area of inquiry and knowledge, especially within cities located in the tropics, where research remains incipient. In this study, the influence of four land cover types on outdoor thermal comfort was examined through a combination of microclimatic sensor measurements and subjective surveys of park visitors that were obtained concurrently within a large urban park in Singapore.  These types include:

  • high-density vegetation;
  • low-density vegetation; 
  • water body/feature; and
  • urban/built up area.

The study addressed the following questions: Do land cover variations matter with respect to OTC? Are perceived & objective OTC similar?

Key Lessons Learned

  • Land cover does influence most microclimate OTC aspects significantly in terms of measured data but:
    • Subjective data do not show concordance;
    • Acclimation/acclimatization from duration of stay and other socio-cultural factors should be further investigated.
  • Influence of humidity & wind at urban microscales towards OTC should not be underplayed.
  • Existing heat indices developed under non-tropical regions may be inaccurate within tropical cities, especially when one considers subjective and perceived thermal
    comfort/discomfort by residents who may already be acclimatized to hot and humid conditions.
  • New indices may have to be developed specifically for cities located in these climates.

Knowledge Gaps and Needs

  • A lack of quantitative work exists on tropical urban thermal comfort work relative to other climates and other aspects of urban meteorology and climatology; future work in the context of this research includes:
    • Research into assessing or summarizing results from case studies would be very beneficial for a wide variety of stakeholders (academics, planners, landscape architects, etc.)
    • A future endeavor should include quantifying the complete ecosystem services provided by urban trees and vegetation for cities in these regions; this would require interdisciplinary contributions in terms of methodology and conceptual frameworks, in order for this expansion to develop. 

Policy/Practice Implications of Research

Planners and design practitioners in humid tropical cities should be cognizant of the fact that land cover may not influence subjective or perceived changes to microclimate, possibly due to acclimatization from residents, when assessing the effectiveness of this ecosystem service provided by urban vegetation in this context; in particular, building design (micro-) and precinct planning (local-) should not neglect this, or worse, have contradicting design/planning outcomes.