Relations of radiation fluxes over natural surfaces

Radiation fluxes over surfaces of bare soil and short grass sod were measured on clear days at St. Paul, Minnesota. Widely diverse types of daily cycles describing the hourly dependence of net upon net solar radiation were found. Heating coefficients depended as much upon atmospheric radiative properties as upon surface properties. Causes for these relations are proposed and tentatively verified experimentally. The accuracy of regressions of solar on net radiation is shown to depend upon the uniform distribution of data points extending to the region of the origin. Controversies in the literature are illuminated by this analysis, both theoretically and experimentally. Two equations relating the slope of the regression of solar on net radiation to albedo are also considered. Finally, a relation between the long‐wave radiation balance and the heating coefficient proposed by Ekern (1965) is qualitatively substantiated.