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

对太阳辐射从云顶进入云层和从云底离开的观测表明，从组成云层的水滴和气体的光学性质中吸收的能量比预测的要多。人们提出了几种假说来解释这种所谓的“反常吸收”，但没有一种假说被普遍接受。解决这一明显差异的部分困难在于，到目前为止可用的衡量标准只说明了故事的一部分。在最好的情况下，测量的是云顶能量向下的总通量(辐照度)，同时在云底也是相同的量。辐照度的差异不仅是由于沿太阳方向的辐射的吸收和散射，而且也是由于沿所有其他方向流动的散射辐射的消光。要了解异常云吸收问题的核心，需要了解辐射能量或辐射度的方向相关性信息。这笔赠款支持开发和测试设计新颖的辐射计，以测量向上或向下半球约50个不同方向的辐射度。课程将采用光纤光学和ccd技术的最新发展。对该仪器的评估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对云中辐射的航空测量。

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.