Reflection coefficients, heating coefficients and net radiation at Simcoe, southern Ontario

Abstract

Point measurements of incoming and reflected solar radiation and net radiation were made over several crop surfaces at the Simcoe Horticultural Experiment Station in southern Ontario. Crop albedo values were calculated and net radiation related to solar radiation by regression analysis. These show that: (1) albedo is close to the value of 0.25 postulated by Monteith (1959a) for crops which completely covered the ground; (2) the albedo of leaves stripped from the plant and mounted on a horizontal board is larger than crop values; (3) crop albedo increases markedly at low solar elevations but the increase is of little importance in terms of absorbed solar radiation because of the low level of the solar intensity; (4) heating coefficient values are consistently positive but show no relationship with surface cover and season; (5) there is no advantage to incorporating albedo in the linear relationship between net and net short-wave radiation; and (6) one equation fits the data satisfactorily and is similar to other proposed equations relating net and solar radiation.