Relationship of urban heat with building density and green spaces - a remote sensing-based study across Vietnam’s metropolitan areas

Abstract

Urban heat island effects are an increasing challenge for metropolitan areas, especially in regions where climate change increases the frequency of extreme temperatures. The consequences for human health are understood and must be addressed by urban planning. Although many studies currently exist regarding relationships of adaptation measures and urban heat amongst individual single cities, there is little general understanding of how urban development impacts temperature on a large scale. In this study we analyze the correlation between urban heat and two indicators of urban morphology: The green spaces and the density of buildings. We hypothesize that the relation between building density, urban green space and urban surface temperature can be quantified using openly available techniques of Earth observation. To grant an objective and consistent analysis over the entire country of Viet Nam, we use information from different high-resolution imaging satellites. The computation of Pearson correlations across 58 Vietnamese districts confirms the hypothesis, indicating a negative impact of urban green space (-0.217), a positive impact of building density (+0.392) and an even stronger relationship with both indicators combined (+0.435). The findings are discussed with data of three research projects involving the cities of Ho Chi Minh, Da Nang, and Hue, and interpreted regarding regional differences and implications for urban planning. As one key finding, building blocks with open architecture show statistically lower temperatures than blocks of compact structure. These differences apply for buildings of all sizes, but they are more distinct for blocks with small buildings.