How 'hot' is too hot? Evaluating acceptable outdoor thermal comfort ranges in an equatorial urban park.

Urban green spaces offer vital ecosystem services such as regulating elevated temperatures in cities. Less information exists, however, on how urban green spaces influence outdoor thermal comfort (OTC), which is dependent on people's perceptions of the complex interactions amongst ambient humidity, wind and both air and radiant temperatures. In this study, we analysed an existing OTC dataset compiled within a large Singapore urban park and calibrated OTC thresholds for physiological equivalent temperatures (PET) by analysing PET against thermal perception survey responses from the park visitors (n = 1508). We examined OTC according to (i) neutral, (ii) acceptable and (iii) preferred temperatures, where respondents felt 'comfortable' outdoors in the park. We estimated that neutral temperature, when all respondents experience neither heat nor cold stress, is 26.2 °C; acceptable temperatures, when only slight heat or cold stress is experienced, range between 21.6 and 31.6 °C; and preferred ('ideal') temperature for all respondents is 24.2 °C. Respondents residing for more than 6 months in Singapore achieved thermal neutrality, suggesting that a greater degree of thermal adaptation likely developed during acclimatisation to local climate through a combination of physiological, behavioural and psychological circumstances. Comparisons with other OTC studies showed differences in synoptic climates are linked to variations in the magnitude and ranges of perceived PET. Lastly, respondents in this study perceived lower neutral and preferred temperatures compared to respondents surveyed over a variety of urban land use categories in another local study. The differences in neutral and preferred temperatures between studies suggest that lower park temperatures and different environmental attitudes influence perceived OTC.

Patterns of land change and their potential impacts on land surface temperature change in Yangon, Myanmar.

This study used remote sensing imagery to characterize land use/cover patterns and to derive land surface temperature (LST) of Greater Yangon, the largest urban agglomeration in Myanmar, to provide insights into the association between land use/cover and seasonal, daytime, and nighttime LST change. Analysis of Landsat images from 1987 to 2015 showed urban expansion radiating from the city center and along prominent rivers, with major increases in built-up land (6.4%) and grassland (10.1%) and consequent decline in agricultural land (17%). Examination of MODIS LST showed that agricultural land was warmer than the city core during daytime in hot seasons, while in cold seasons, the city core was warmer than its rural surroundings during both daytime and nighttime. Correlation analysis revealed stronger association between built-up land and nighttime LST from 2000 to 2015, suggesting an increased surface urban heat island effect. Furthermore, this study highlighted two main differences from prior work on the influences of land use/cover on LST. First, the predominant land use/cover type that had great overall impact on LST was agricultural land, marked by its statistically significant correlation coefficients across all time periods of analysis. Such finding emphasized the influence of agriculture and related practices on the atmosphere and climate system. Second, the temporal analysis of LST highlighted a stronger and more complicated role water played because of its negative correlations with daytime LST and positive correlations with nighttime LST. The findings of this study underscored more complex effects of land use/cover on the spatial and temporal variations of LST in Yangon, compared to prior work that generally reported high LST in the urban areas. These insights improve the understanding of the land change consequences on the temporal dynamics of LST and can support sustainable land use planning for the better well-being of the inhabitants in Greater Yangon.