This study theoretically investigates the transport of broadband solar radiation in the Earth's cloudy atmosphere (extended and broken) by considering three plane parallel layers: i) thin bottom layer adjacent to the Earth's surface; ii) intermediate layer where clouds are most embedded; and iii) upper layer that is essentially cloud-free with possible occurrence of only thin clouds. These three layers are coupled by upwelling and downwelling radiation exchanges, including multiple retro-diffusion, and both direct beam and diffuse components are considered. The interrelation and relative magnitude of the solar radiation flux cascade across the atmosphere - α_P, R_a, R_c, R_g and G/H – was established and explored as a tool for the present simulations. Two distinct radiation transport regimes through the inter-cloud gaps are identified, with the regime transition occurring when (AR*TAN(θ)+1)*CF = 1 where AR, θ and CF are the cloud aspect ratio, solar zenith angle, and cloud fraction, respectively. The variation of the solar radiation fluxes with CF and θ exhibit the transition between the two radiation transport regimes, as evidenced in the flux absorbed in the cloudy layer. The effect of AR upon the solar fluxes also exhibits the two radiation transport regimes, with one regime having linear dependence of the various fluxes on AR and the other one having fluxes stay at constant levels independent of AR. The shape factor SF of cloud top and bottom boundary “surfaces” is introduced to account for the self-irradiation effect for different cloud types. It is found that increased roughness of one or both boundaries increases the cloud absorptance in all cases whereas transmittance and reflectance for upwelling and downwelling can either be diminished or enhanced.

With the proposed model the estimated impact of clouds on the enhancement of the shortwave radiation absorption in the atmospheric column was improved leading to results closer to the cloudy-sky absorptance observations reported in the literature. The ratio of the cloud radiative forcing at the surface to the cloud radiative forcing at the top of the atmosphere (R_net), obtained by means of the present model, lead to R_net = 1.3, closer to the estimate of 1.5 by Cess et al. than the values reported by other cloud radiative transfer models.

该研究从理论上通过考虑三个平面平行层来研究宽带太阳辐射在地球阴天大气层（扩展和破裂）中的传输：i）与地球表面相邻的薄底层；ii）云层最深的中间层；iii）上层基本无云，仅可能出现薄云。这三层是通过向上和向下辐射交换进行耦合的，包括多次逆向扩散，并考虑了直接光束和漫射分量。跨越大气中的太阳辐射通量级联的相互关系和相对幅度- α _P，R_一个，R _Ç，R_克和G / H–已建立并作为当前模拟的工具进行了探索。确定了通过云间间隙的两种不同的辐射传输方式，当（AR * TAN（θ +1）* CF  = 1时发生状态转变，其中AR，θ和CF是云的纵横比，太阳天顶角，和云分数。太阳辐射通量随CF和θ的变化表现出两种辐射传输方式之间的过渡，这在阴天层吸收的通量中得到了证明。AR的效果太阳通量还表现出两种辐射传输方式，一种方式具有各种通量对AR的线性依赖性，另一种方式具有与AR无关的通量保持恒定的水平。引入云顶部和底部边界“表面”的形状因子SF来说明不同云类型的自辐照效果。已经发现，在所有情况下，一个或两个边界的粗糙度增加会增加云的吸收率，而上升或下降的透射率和反射率可以减小或提高。

利用所提出的模型，估计了云对大气柱中短波辐射吸收增强的影响得到了改善，从而使结果更接近文献中报道的多云天空吸收率观测值。通过本模型获得的表面的云辐射强迫与大气顶部的云辐射强迫之比（R _net）导致R _net  = 1.3，更接近于Cess等人的估计值1.5。 al。而不是其他云辐射传输模型报告的值。