In this work, a physical model based on the radiative transfer equation is presented to estimate the global solar irradiance on top of the Earth’s atmosphere surface. A link is established among the radiative transfer through the atmosphere, the geographic coordinates of a city (longitude, latitude), time of day, and date of the year. The discrete spherical harmonics method is applied to solve the radiative transfer equation. The city of Dschang in Cameroon is taken as an example of application of the model. This city is located at latitude 5°44^′N and longitude 10°04^′E. It is assumed that the atmosphere of the city is inhomogeneous and composed of non-polarizing Haze L aerosol particles in gamma distribution, while the ground surface diffuses radiation isotropically. The predictions are compared under clear sky conditions to some existing models of irradiance such as the Bird model and Davies and Hay model for a homogeneous atmosphere. Results demonstrate that the present investigation matches well with the Bird and the Davies and Hay models and is valuable for ground solar irradiance estimation. The effects of the inhomogeneity of the atmosphere on total insolation are also studied, and our results indicate that the inhomogeneity of the atmosphere reduces local insolation. The present study shows that the radiative transfer model is an efficient technique for estimating global solar radiation at any level of the stratified atmosphere and under different atmospheric conditions.

中文翻译：

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地表辐照度估计的辐射传递模型：晴空

在这项工作中，提出了一个基于辐射传递方程的物理模型来估计地球大气表面顶部的全球太阳辐照度。通过大气的辐射传输、城市的地理坐标（经度、纬度）、一天中的时间和一年中的日期之间建立了联系。离散球谐函数用于求解辐射传递方程。以喀麦隆 Dschang 市为例说明该模型的应用。这座城市位于北纬5°44 ^′，东经10°04 ^′E. 假设城市大气是不均匀的，由伽马分布的非极化 Haze L 气溶胶粒子组成，而地表各向同性地扩散辐射。这些预测在晴朗的天空条件下与一些现有的辐照度模型进行了比较，例如用于均匀大气的 Bird 模型和 Davies and Hay 模型。结果表明，目前的调查与 Bird 和 Davies 和 Hay 模型匹配良好，对地面太阳辐照度估计很有价值。还研究了大气的不均匀性对总日照的影响，我们的结果表明，大气的不均匀性降低了局部日照。