Spatial variability of diurnal temperature range and its associations with local climate zone, neighborhood environment and mortality in Los Angeles

Abstract

Urbanization alters the Earth’s emissivity and leads to intraurban differences in temperature variations, including diurnal temperature range (DTR). Despite DTR as a factor of thermal discomfort and mortality risk worldwide, its spatial variability and intraurban associations with local climate zone (LCZ), neighborhood environment and mortality risk have not been investigated. This study first applied the LCZ framework to evaluate associations between climate-sensitive urban design and long-term DTR exposure in Los Angeles, a megacity with the largest DTR in the United States. Using fine-scale daytime and nighttime Landsat thermal imagery to quantify DTR, we found that compact low-rise areas had high DTR, high-rise areas with moderate DTR, and natural areas with the lowest. Young-age, non-white and low-income populations were vulnerable and exposed to high DTR. A spatial Bayesian Poisson regression confirmed that neighborhoods with higher DTR exhibited higher mortality risk after controlling for socioeconomic factors (relative risk: 1.047, 95% credibility interval 1.013–1.082). We did not observe a significant association between mean temperature and mortality in our study. As spatial variability of DTR induces heterogeneous exposure and the evidence that long-term DTR exposure is positively associated with mortality across neighborhoods, planners and policymakers should consider urban landscaping to mitigate large DTR for risk reduction.