Design and Testing of a Fiber Optic Radiometer to Study the Horizontal Convergence of Solar Fluxes in Clouds

对从顶部进入云层并从底部离开的太阳辐射的观测表明，吸收的能量比根据组成云层的水滴和气体的光学特性预测的要多。 已经提出了几种假设来解释这种所谓的“反常吸收”，但没有一种被普遍接受。 解决这种明显差异的部分困难在于，目前可用的测量数据只能说明部分情况。 最好的情况下，所测量的是云顶向下的总能量通量（辐照度）和云底的相同量。 辐照度的差异不仅是由于辐射在太阳方向上沿着线的吸收和散射，而且还由于在所有其他方向上流动的散射辐射的消光。 辐射能量或辐射率的方向依赖性的信息，是需要得到的异常云吸收问题的核心。 这项拨款支持开发和测试一种设计新颖的辐射计，以测量向上或向下半球大约50个不同方向的辐射率。 将采用光纤和CCD技术的最新发展。 对该仪器的评价将包括与太阳辐照度的标准测量进行比较。 该仪器的最终应用将是在空中测量云中的辐射。

Observations of solar radiation entering clouds at the top and exiting at the bottom indicate that more energy is absorbed than predicted from the optical properties of the drops and gases of which the clouds are composed. Several hypotheses have been proposed to explain this so-called "anomalous absorption" but none is generally accepted. Part of the difficulty in resolving the apparent discrepancy is that the measurements available to now only tell part of the story. At best, what is measured is the total downwards flux of energy (the irradiance) at cloud top and the same quantity simultaneously at cloud base. The difference in irradiance is accounted for not only by the absorption and scattering of radiation along the line in the direction of the sun but also by the extinction of scattered radiation flowing in all other directions. Information on the directional dependence of the radiant energy, or the radiance, is needed to get at the heart of the problem of anomalous cloud absorption. This grant supports the development and testing of a radiometer of novel design to measure the radiance in approximately 50 different directions in the upwards or downwards hemisphere. Recent developments in fiber optics and CCD technology will be employed. Evaluation of the instrument will include comparisons with standard measurements of solar irradiance. The ultimate application of the instrument will be the airborne measurement of radiances in clouds.