Geoscience Reference
In-Depth Information
1 Background
The urban heat island (UHI) phenomenon can be found in many major cities
throughout the world. UHI occurs when air and surface temperatures are hotter
than their rural surrounding (Gartland
2008
). Rapid urbanization causes reduction
of vegetated areas and increases the built-up surfaces. The built-up surfaces trap
the incoming solar radiation during the day and then re-radiate it at night (Solecki
et al.
2004
). Several studies have been carried out to investigate the UHI impacts
(Mallick and Rahman
2012
; Choi et al.
2012
; Yan et al.
2012
; Omar
2009
;
Shahmohamadi et al.
2009
). Thus, the seriousness of UHI phenomena cannot be
denied and the mitigation strategy should be applied to combat the UHI effects at
the macro and micro levels.
The Landsat 5 TM and Landsat 7 ETM+ are widely used to monitor the land
use changes and derive land surface temperature of an area. Example on the use of
these satellite images in Malaysia in UHI studies can be found in (Wan Mohd et al.
2004
) and (Takeuchi et al.
2010
). Previous studies clearly demonstrated that the
implication of rapid urban growth is the decrease in vegetated areas, increased
surface temperature and hence, modified urban microclimate. However, the veg-
etated area helps to keep the temperature of the surroundings lower than the
developed area (Buyadi et al.
2013
). Additionally, maturity of trees and vegetation
is considered as a vital parameter to ensure lower temperature in an urban area
through shadow and transpiration.
2 Study Area and Data Acquisition
The study area is located within the District of Petaling (i.e. City of Shah Alam,
Petaling Jaya and Subang Jaya). These cities are selected due to rapid urban
development activities. The climate of the cities is categorized as a hot and humid
tropical climate which is warm and sunny, along with abundant rainfall, especially
during the Northeast Monsoon seasons from October to March. Temperatures tend
to remain constant with maximum values of between 31 and 33 C, while the
minimum between 22 and 23.5 C. Relative humidity is around 72-78 %, and the
annual rainfall is about 3300 mm. The geographical location of the study area is
shown in Fig.
1
. The data (i.e. temperature and water vapor content) of nearby
weather station (Subang Meteorological Station) are obtained from the Malaysian
Meteorological Department (MMD). The data obtained coincide with the time and
date of the Landsat TM satellite pass. Landsat TM images dated 21st February
1991 and 21st January 2009 are used. For a more detailed study on the effects of
vegetation on the surrounding areas, three study areas are selected i.e. Shah Alam
Lake Garden, Kelana Jaya Recreational Park and Subang Ria Recreational Park
located in Subang Jaya.
