Chapter 6 – Microclimatology of Radiation: (i) Radiative Properties of Natural Materials

This chapter describes how radiant energy reaching a surface is absorbed, reflected (scattered), and transmitted. These processes depend on wavelength and on the angle of incidence of direct radiation. Radiative properties of water, soil, leaves, vegetation canopies, and animal coats are reviewed. Still water is an effective reflector of the solar beam at low angles of elevation, but only reflects about 5% of solar radiation when the sun is high. Water absorbs least in the blue-green portion of the spectrum. In the infra-red region water absorbs strongly in several wavebands. Reflection of solar radiation by soil depends on soil structure and water content. Leaves and canopies absorb least (reflect most) around green wavelengths and transmit near-infra-red radiation very effectively.