To investigate the characteristics of potential temperature profiles, a field observation was continuously carried out at a residential site in Tokyo. Following results were obtained; 1) In winter the potential temperature has a maximum value around the roof top level, whereas in summer near the ground surface. The heat source moves up and down due to the seasonal and daily change of solar angle. This isa distinctive characteristic of the micrometeorology of the urban canopy contrast to vegetation canopy. 2) The maximum temperature at the roof top level implies that inversion layer is formed within the canopy. This is directly confirmed by the turbulent flux measurement.