Improved Atmospheric Solar Radiation Budget Pyranometry

Abstract

The solar radiation budget is investigated with seven pyranometers. Three of these instruments have horizontally aligned sensors. The sensors of the remaining four instruments are vertically aligned in such a way that their normals point to the north, south, east, and west. With this system, the authors are able to detect all properties of interest for radiation budget considerations. These are the flux densities of direct solar, diffuse-sky, global, and reflected radiation; the vector of the solar net flux density; and the solar radiation supply (for atmospheric absorption and/or photochemical processes). Equations for the vector of the net flux density and the radiation supply in terms of the pyranometer readings are derived and discussed. Whenever the solar radiation supply and the mean solar absorption coefficient of the atmosphere or of specific atmospheric species are known, the relevant solar volume absorption rate and the appertaining solar heating rate of the atmosphere can be calculated without any assumptions. This method is applicable during any weather situation throughout the entire atmosphere. Simple parameterizations of the radiation supply and the total atmospheric heating during the daylight period due to absorption of solar radiation by particles are discussed.