Time Evolution of an Urban Heat Island from High-Density Observations in Kyoto City

Detailed observations of temperature evolution are required to clarify the mechanism of the nocturnal evolution of urban heat island. We conducted spatial and temporal high-density observation of temperature and longwave radiation in Kyoto City, Japan. The results suggest that the time evolution associated with temperature phase shift is one type of urban heat island evolution. Moreover, the phase shift appears to be closely related to a change in wind direction. Two phases, before and after the phase shift, are suggested to be controlled by two different mechanisms: radiative cooling and advection.