Abstract
Mitigating high air temperatures and heat waves is vital for decreasing air pollution and protecting public health. To improve understanding of microscale urban air temperature variation, this paper performed measurements of air temperature and relative humidity in a field of Wuhan City in the afternoon of hot summer days, and used path analysis and genetic support vector regression (SVR) to quantify the independent influences of land cover and humidity on air temperature variation. The path analysis shows that most effect of the land cover is mediated through relative humidity difference, more than four times as much as the direct effect, and that the direct effect of relative humidity difference is nearly six times that of land cover, even larger than the total effect of the land cover. The SVR simulation illustrates that land cover and relative humidity independently contribute 16.3% and 83.7%, on average, to the rise of the air temperature over the land without vegetation in the study site. An alternative strategy of increasing the humidity artificially is proposed to reduce high air temperatures in urban areas. The study would provide scientific support for the regulation of the microclimate and the mitigation of the high air temperature in urban areas.
Highlights
High air temperatures and heat waves, which alter the air physicochemical process and increase air pollution [1,2], exert severe impacts on both the environment and public health.Many studies have reported that high air temperatures and heat waves are associated with mortality risks and substantial illnesses around the world [3,4,5,6,7,8,9,10]
Given the adverse influences posed by high air temperatures and heat waves and in the light of the views that land cover changes impact on local climate, this study performed the field measurements of air temperature and relative humidity
Thereafter, the study used path analysis to examine the direct and indirect effects of land cover and humidity differences on air temperature differences, and employed an support vector regression (SVR) simulation to quantify the independent contributions of the two factors to it
Summary
High air temperatures and heat waves, which alter the air physicochemical process and increase air pollution [1,2], exert severe impacts on both the environment and public health.Many studies have reported that high air temperatures and heat waves are associated with mortality risks and substantial illnesses around the world [3,4,5,6,7,8,9,10]. As urbanization continues, mitigating high air temperatures and heat risks is a vital challenge for the sustainable development of cities [17], as well as for sustainable development of human society as a whole It has gradually become a common view that the increase in concentrations of greenhouse gases, which trap outgoing long-wave radiation from the Earth to space, is an influential factor leading to the increase in global air temperature [12,18,19], there is a growing consensus that land cover variation exhibits more local effects on air temperature rather than the global effects produced by greenhouse gas emissions [20,21]. The change of land cover directly modifies the energy budget and Atmosphere 2020, 11, 1377; doi:10.3390/atmos11121377 www.mdpi.com/journal/atmosphere
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