Sensible Heat Fluxes over an Urban Area—Vancouver, B.C.

Abstract

The use of the eddy correlation technique is demonstrated for the measurement of sensible heat transfer in an urban area. The problems of time and space sampling (in the horizontal and vertical) are investigated. Based on 27 summer days of observations from a roof-top site in the central built-up part of Vancouver, the diurnal variation of sensible heat transfer above an urban area is described. The flux of heat at 1.2, 4 and 20 m above roof level largely reflected time and magnitude changes in the net radiation field. While being in phase with net radiation, the sensible heat flow commonly exhibited unusually high values in the late afternoon. Nocturnal urban sensible heat flow was quite unlike the normal rural pattern, often being directed into the atmosphere. Also at night the existence of flux divergence is suggested.