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