WCs for specific times of day and the urban heat island (UHI) have not been analysed heretofore.
Diurnal rhythms also present perspectives on anthropogenic influences.
This rural warming can lead to an early morning urban 'cool island' in some cities due to the atmospheric boundary layer being deeper over the urban area, reducing the apparent early morning heating compared to the rural environment (Oke 1982, Theeuwes 2015).
However other factors including shading in urban canyons, leading to a smaller surface area of accessible insolation, greater total urban surface area (compared to flat surface) and enhanced early morning absorption of radiation by urban materials (e.g. This means that the urban heat island (UHI) intensity undergoes a marked diurnal variation with the largest difference typically 3–5 h after sunset and smallest, which may sometimes be negative, from early morning to mid-afternoon.
Regular diurnal and weekly cycles (WCs) of meteorological parameters provide valuable insights into the consequences of human activities (e.g.
industrial activity, generating electricity, biomass burning and powering motor vehicles, which commonly change at weekends), particularly in urban areas.