Landscape variability of Melbourne’s botanic gardens and visitor thermal comfort
Creators: name: Lam, Cho Kwong Charlie
Publisher: name: Figshare
Year: 2017
Subjects: subject: Atmospheric Sciences
subject: FOS: Earth and related environmental sciences

description: Outdoor thermal
comfort is important for tourism and landscape design. Many previous studies have
identified the thermal comfort range for local residents, but how it differs
for overseas visitors is unknown. Improving human thermal comfort is essential
as it enhances the quality of urban living and the use of outdoor space. Urban
green space has previously been shown to reduce the perception of thermal
discomfort under hot conditions. However, there has been limited research on
the impact of different vegetation configuration on cooling the environment at
a microscale. Moreover, cooling associated with irrigation is not well
understood in urban green space. This study demonstrates the importance of
thermal comfort in urban planning using the Royal Botanic Garden Melbourne
(RBGM) and Cranbourne (RBGC) in Australia as case studies. Climate change is expected
to increase the frequency of heatwaves in Melbourne, which will affect the
comfort of visitors to botanical gardens and parks. <br>
    <br>
   Weather station data in both RBGM and RBGC were compared
against thermal comfort survey data from visitors during the summer of
2013/2014 (<i>n</i> = 2198 at RBGM, <i>n</i> = 1122 at RBGC). Meteorological transects were
also conducted in RBGC. This study is the first to compare the results from two
large botanic gardens with different irrigation regimes and plant species in
Australia. Besides the survey and weather data, information regarding
irrigation, soil infiltration and sky view factors were obtained to determine
the effect of shading and irrigation on temperature reduction. The thermal
perception of local residents before and after the unprecedented January 2014
heatwave was also compared. <br>
    <br>
   Overseas visitors had a fundamentally different thermal
perception and preference compared with local Australian visitors. Clothing
behaviour also differed between visitors from different countries of origin.
This finding assists the tourism industry in marketing tourism destinations to
visitors from different countries. <br>
    <br>
   Local Australians’ thermal perception changed after being
exposed to the January 2014 heatwaves. There was an inter-daily variability of
thermal perception, showing that local visitors were adaptable to the thermal
environment in only a few days. Since heat acclimatization takes at least
several days to a week, psychological adaptation to heat and changes in
clothing behaviour explain the changes in people’s thermal perceptions in such
a short time. Many thermal indices assume that people’s thermal perceptions are
relatively consistent over time, at least on sub-seasonal scales. This study
suggests that psychological adaptation to extreme heat should be incorporated
by future thermal indices. <br>
    <br>
   Shading and irrigation both impacted air temperature in
summer, and more so in RBGM. Highly shaded areas were 2 – 4 °C cooler than
areas with limited shading during heatwave conditions. Nocturnal irrigation
produced up to 1.5 °C of cooling, and a residual cooling of up to 1 °C in the
early morning before 12 noon. Irrigated areas were also shown to be 1 – 2 °C
cooler than non-irrigated areas. In light of hotter and drier climate in the
future, this study helps both gardens with their landscape succession planning,
as well as urban planning in the City of Melbourne.