THE ENERGY BALANCE CLIMATOLOGY OF A CITY-MAN SYSTEM

Abstract

ABSTRACT The urban energy balance climatology of the city and man in the Los Angeles basin was examined during a cloudy day (“Catalina eddy”) in September, 1968, from about sunrise to sunset, by measuring or estimating solar radiation, net radiation, ground heat flux, actual surface temperature, terrain radiant temperature, radiant sky temperature, and dry and wet-bulb temperature for the physical urban interface. An analogous theoretical model attempted to define the input of energy to the human interface via the solar heat load, and the disposal of human net radiation was shown via the channels of latent, sensible, and body heat flux. In spite of an apparent uniform cloud cover, the energy parameters had considerable areal variation in intensity and trend. During the daylight hours seventy percent of the solar radiation was absorbed. An additional thirty-two percent was removed by longwave radiation. Of the net radiation received on the dry surface (forty-seven percent of solar radiation), about eighty percent was disposed via sensible heat flux, and the remainder entered the pavement as storage. Air temperatures taken at shelter height were out of phase with the ongoing energy regime and were deemed of dubious value in urban climatic studies. Urban man received only thirty-seven percent and seventy percent of the values available at the horizontal pavement for solar radiation and net radiation, respectively. A series of empirical and theoretical models show high correlations with the observations. It appeared that solar radiation and net radiation (physical and human) could have been estimated via the solar constant and appropriate transmissivities.