Angular variation of the infrared emissivity of ice and water surfaces

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Abstract
An experimental investigation of the emissivity of water and ice surfaces in ihe thermal infrared (8-14 μm) band is described. The experimental technique is a particularly simple one, suited for rapid determination of emissivity in the laboratory, yet it yields an accuracy of ±001 for relative emissivity over a wide range of viewing angles. The results show that the emissivity of an ice surface is significantly lower than that of a water surface for angles up to at least 65° from the surface normal and thai both are in approximate agreement with the Fresnel formula for a plane interface between homogeneous media. The implications of the numerical results for airborne and spaceborne remote sensing of freezing water are discussed.