Downward shortwave radiation (DSR) is the main energy source for the Earth's system and a dominant component of the radiation budget. Although many algorithms have been proposed for estimating DSR, most models only consider either the radiative effects of terrain or atmosphere, and no research has considered the conditions of clouds on the mountainside. In this paper, a high-resolution Mountain Radiative Transfer model with Clouds (MRTC) is proposed to characterize the cloud-terrain coupling effects on DSR under different surface positions relative to the clouds. To operate the MRTC, a look-up table is employed to obtain initial radiative parameters. The comparison with Monte-Carlo based radiative transfer indicates that MRTC can be applied to conditions of clouds on the mountainside. And the reliability of MRTC under conditions when clouds are above mountains is also validated against in-situ measurements, with an RMSE of 149.9 , a bias of 28.3 , and an of 0.74. By using more accurate cloud cover data extracted from All-Sky images, the accuracy of MRTC has improved, with the RMSE decreasing to 115.8 , and the increasing to 0.8. This suggests that the uncertainty in satellite cloud products significantly contributes to errors in DSR estimations. MRTC is expected to more accurately represent cloud-terrain coupling effects on DSR, and improve the accuracy of DSR estimation over rugged terrain under cloudy skies.

中文翻译：

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崎岖地形和云层上的下行短波辐射建模


下行短波辐射（DSR）是地球系统的主要能源，也是辐射预算的主要组成部分。尽管已经提出了许多估计DSR的算法，但大多数模型仅考虑地形或大气的辐射影响，并且没有研究考虑山腰云的情况。本文提出了一种高分辨率山地辐射传输云模型（MRTC）来表征相对于云的不同表面位置下云地耦合对 DSR 的影响。为了操作 MRTC，使用查找表来获取初始辐射参数。与基于蒙特卡罗的辐射传输的比较表明MRTC可以应用于山腰云的条件。山上云层条件下 MRTC 的可靠性也通过现场测量进行了验证，RMSE 为 149.9，偏差为 28.3，an 为 0.74。通过使用从全天图像中提取的更准确的云量数据，MRTC的精度得到了提高，RMSE下降到115.8，并增加到0.8。这表明卫星云产品的不确定性极大地导致了 DSR 估计的错误。 MRTC有望更准确地表征云地耦合对DSR的影响，并提高多云天空下崎岖地形的DSR估计精度。