Integration of Remote Sensing and GIS for heat island mapping: a case study of Singapore
Janet E. Nichol
Department of Geography
National University of Singapore, Singapore 0511
Abstract
Ground Surface Temperatures for Singapore derived from LANDSAT Thematic Mapper thermal band are seen to be related to differences in generalized categories of land cover. The relationship was examined for two contrasting types of environment: primary and secondary rain forest in Singapore’s central water catchment area, and high density municipal housing estates, using the spatial analysis capabilities of a GIS. Implications for possible landscaping policy in housing areas are apparent from the intimate spatial relationship between temperature and biomass.
Background
Studies of Singapore’s climate indicate significant temperature differences corresponding with land cover type (Singapore Meteorological Service, 1981) and heat island which reaches its greatest intensity around 10pm to midnight. However, satellite-derived thermal data record surface temperature, for whch rural-urban differences are said to be greatest during the daytime (Roth & Oke, 1989).
Although satellite derived radiance values can readily be converted to equivalent black body temperatures, using Planck’s constant (0), this usually underestimates Surface Temperature in warm humid atmospheres, and a correction using atmospheric data should be made if available. A further correction for emissivity is required, to obtain actual Surface Temperature.
The main factors prompting this study was the potential offered by the high resolution of the LANDSAT TM thermal band for evaluating temperature differences in Singapore’s urban, thus heterogeneous landscape, due to differential emissivities of land cover types. This has implications for landscaping policy in controlling the having environment.
The objectives of thThe objectives of the study are to examine the nature of the relationship between temperature and land cover for two specific land cover tpes in singapore. These are :-
STUDY AREA 1. The Rain Forest Nature Reserves.
STUDY AREA 2. Singapore’s high rise municipal housing estates.
The Study Areas
Study areas I comprises the central portion of Singapore island containing the Central Catchment Area Nature Reserves (Figure 1) and bounded on all sides by major trunk roads. This area totals 60 sq km of forest, reservoirs, and some urban and suburban development. Within the forested area, but separated from it by an expressway, is Bukit Timah Nature Reserve. Concern has been expressed about the future regeneration status of this reserve due to its small size and isolated state.
Study area 2 is fragmented in nature, as it represented nine of Singapore high density municipal housing estates, located to the east of the Central Catchment Area. The estates are spatially adjacent but are of varying size, age and proportion of built-up area. Population density averages 37,5000 per square kilometer, in a combined area of 17 sq. km.
