Evaporation from Very Shallow Pans

Abstract

Evaporation from eight 1-inch deep square pans was studied. The pans were insulated with styrofoam and built in three different sizes. The 1-ft and the 8-ft pans were executed in two colors, black and white, and the 4-ft pans in black, white, green and gray. The measured physical data are tabulated. Some aspects of the energy budget of pan evaporation are analyzed and discussed. It was found that color has no significant effect on the turbulent vapor diffusion. The value of the constant in Bowen's ratio for the different pans varied between 0.71 and 0.83, which is somewhat larger than the value of the psychrometric constant, 0.65, but which is much smaller than the value, 1.52, for the U.S. Weather Bureau Class A pan. The difference between the evaporation from the black and the white pans and the incoming solar radiation were found to be highly correlated.