Angular dependence of forward scattering induced by condensate on greenhouse cladding materials

The forward scattering properties of four cladding materials, namely low-density polyethylene (LDPE), anti-drop condensation polyethylene (ADCPE), diffusive polyethylene (DPE), and single glass (SG) were measured in the dry state and when covered with condensate at three different incidence angles, namely 0, 15, and 30°. In the dry state, single glass behaved as a quasi non-diffusive material in contrast to the three plastic films which scattered the radiation due to their surface roughness, bulk heterogeneities or the addition of diffusive agents. With the exception of the anti-drop condensation polyethylene, the forward scattering of the materials was broadened by the presence of condensate. For these materials, the scattering pattern shifted towards the normal to the cladding with increasing incidence angle. This meant that less radiation was scattered to the opposite side of the directly transmitted, unscattered beam. At an incidence angle of 30°, a distinct shoulder in the scattering pattern, situated between the direct beam and the normal, was found on wet single glass in contrast to the plastic films.