Multi-angular thermal infrared emission characteristics of Bohai Sea ice based on in situ measurements

We report on the radiative transfer process and optical properties of sea ice in the thermal infrared (TIR) band, presenting two new linear kernel driver models (Relative Emissivity Distribution Function, REDF) that describe TIR emission characteristics of smooth and rough ice. In order to test the models and determine the necessary coefficients, in situ measurements from the Bohai Sea were carried out during the 2011/12 and 2012/13 boreal winters. The results show that the relative emissivity of smooth sea ice decreases along with increasing viewing zenith angle, and the shape of the relative emissivity curve is similar to that of an ideal plane. Affected by parameters such as roughness and surface temperature distribution, the anisotropy of relative emissivity of sea ice with a high degree of roughness is stronger relative to the cosine emitter. The model coefficients were also obtained using a robust regression method based on the measured data. The presented models are more practical than the numerical radiative transfer model and can be used for multi-angular TIR remote sensing.

A Langmuir probe technique for measuring temperatures in a flame plasma

A simple method of measuring the temperature of a flame is presented. It is based on the use of a Langmuir probe and the assumption that the flame exhibits local thermal equilibrium so that the Saha equation can be applied. The method has been compared to measurements of temperature based on the relative emissivity of the Na D line at 5896 Å and shows good agreement except in regions where the flame is greatly perturbed or steep temperature gradients exist.

A spectro-photometric comparison of the emissivity of solid and liquid gold at high temperatures with that of a full radiator

It is well known that copper and gold emit greenish or bluish light at high temperatures. Kirchhoff's radiation law obviously suggests a connection between this selective emissivity and the selective reflectivity of these metals at ordinary temperatures, which gives rise to their colour. According to that law the emissivity E' of a surface at a temperature T is connected with its absorptivity A, by the relation E'/E = A, where E is the emissivity of a full radiator or “black body” at the same temperature T. This relation holds for each particular wave-length. The ratio E'/E may be conveniently called, and will be referred to hereafter in this paper as, the “relative emissivity” of the surface. The above law then states that the relative emissivity of a body is equal to its absorptivity for the same wave-length and temperature. For opaque bodies, such as metals, the reflectivity R is equal to 1 — A: and hence the relative emissivity E'/E = A = 1 — R. This relation holds strictly only if emission and reflection take place at the same temperature; but if, as stated by several investigators, the reflectivity of metals for visible rays does not vary with the temperature, a heated metallic surface should emit well those rays for which it is when cold a poor reflector, and vice versâ . This has actually been observed qualitatively for gold and copper by Schaum and Wüstenfeld in a recent photographic comparison of the emission spectra of these metals with that of an approximate “black body.” They also draw attention to the “green-glow” which first makes its appearance when these metals are heated, instead of the usual "red-glow."