Urban nocturnal cooling mediated by bluespace

Abstract

The spatiotemporal characteristics of air temperature and humidity mediated by urban bluespace are investigated using a combination of dense network of climatological observations in a medium-sized US city, computational fluid dynamics and analytical modeling approaches. Both numerical simulation and observational results show that the rate of change of hourly averaged air temperature and humidity at 3.5 m over urban areas peaks two hours after sunset, while it decreases with time monotonically over greenspace, indicating different impacts due to presence of urban lakes. The apparent temperature decreases with distance to lakes in urban area due to higher near-shore humidity. This highlights that urban lakes located near city center can deteriorate the nighttime cooling effects due to elevated humidity. Finally, two analytical models are presented to explain the connection between the surface and air temperature as well as the spatial variation of air temperature and humidity adjacent to the urban lakes. These simplified models with parameters being inferred from the network of measurements have reasonably good performance compared to the observations. Compared to other sophisticated numerical simulations, these analytical models offer an alternative means that is easily accessible for evaluating the efficacy of bluespace on urban nocturnal cooling.

Mixed Convection in an Idealized Coastal Urban Environment With Momentum and Thermal Surface Heterogeneities

“…For example, ambient cloud cover may weaken LSB circulations due to the loss of incoming solar radiation (Segal et al., 1986). The apparent temperature which is a representative of the overall thermal comfort within coastal region can be compromised by the high humidity close to the water body (Y. Cui et al., 2021). Future studies may investigate how atmospheric moisture and the direction of the mean advection impact the momentum and heat transfer in the urban coastal environment.…”

The climate adaptive characteristics of urban inside/outside water bodies based on their cooling effect in Poyang and Dongting lake regions, China

“…The cooling effect of water bodies is the most pronounced within 1 km (horizontal distance) [ 13 ], and it changes with distance [ 30 ]. Urban water bodies located near city center can deteriorate the nighttime cooling effects due to elevated humidity [ 31 ]. Additionally, the surrounding land cover has a greater influence than water bodies on the overall cooling effect [ 32 ].…”

The Regulating Effect of Urban Large Planar Water Bodies on Residential Heat Islands: A Case Study of Meijiang Lake in Tianjin

“…Water bodies, as blue patches within cities, exhibit a cool island effect during the summer due to their lower surface radiation and the cooling of surrounding air [13]. Apart from having a higher heat capacity [14] and promoting heat transfer via convective effects from evaporation [15], in regions with generally low humidity, water bodies increase local humidity, aiding heat exchange during the summer [16]. Additionally, in urban development, water bodies, as open spaces, can create wind corridors that facilitate airflow and promote urban cooling [17].…”