  This paper studies heat fluxes from contributors and mitigators of urban heat
islands using thermal images and weather data. Thermal images were collected
from an observatory operating on the rooftop of a building between November
2021 and April 2022. Over the same period, an automatic weather station network
was used to measure weather conditions at several locations on a university
campus in Singapore. From data collected by the observatory and the automatic
weather station network, a method was developed to estimate the heat emitted by
building facades, vegetation, and traffic. Before performing the analysis of
urban heat fluxes, it was observed that the surface temperature collected from
the observatory is sensitive to some variables. After the sensitivity analysis,
thermal images were calibrated against measurements of the surface temperature
in an outdoor environment. Finally, several contributors and mitigators of
urban heat islands were analyzed from heat fluxes assessed with thermal images
and weather data. According to thermal images collected by the rooftop
observatory, concrete walls are an important contributor to urban heat islands
due to the longwave radiation they emit at night. Vegetation, on the other
hand, seems to be an effective mitigator because of latent heat fluxes
generated by evapotranspiration. Traffic looks to be a negligible source of
heat if considered over a small portion of a road. In the future, more efforts
can be made to estimate the magnitude of the heat released by an
air-conditioning system from thermal images.
