Monte Carlo Simulation of 3D Cloud Radiance Distributions Affected by Ground‐Based Lighting

Abstract Satellite observations of artificial light sources at night are increasing. Clouds, as the most important radiative modulators in the Earth‐atmosphere system, significantly influence the observed values and spatial distribution of the artificial light coming from the ground. However, the mechanisms by which clouds affect the radiative transmission of ground‐based light sources remain poorly understood. Consequently, many quantitative remote sensing applications at night are restricted to cloud‐free conditions. Conversely, ground‐based light can cause anomalous radiation distributions in clouds, hindering studies on their characteristics. In this study, we employed Monte Carlo radiative transfer simulations to investigate nighttime light radiation through complex three‐dimensional cloud structures. The simulations incorporated clouds modeled using large eddy simulation (LES) and custom cloud configurations with varying radii, thickness, base heights, and relative positions between clouds and lighting to elucidate the underlying physical mechanisms. The results indicate that cloud layers exhibit dual effects on radiance distribution: They reduce nadir radiance through absorption and scattering while amplifying surrounding brightness via scattering. Additionally, increasing cloud thickness attenuates overhead radiance, whereas it enhances pronounced peaks at cloud boundaries. Low clouds intercept and modulate upward radiance more effectively than high clouds due to geometric constraints. Source displacement breaks radiance symmetry, enhancing cloud edge brightness. Multiple scattering within clouds redistributes ground‐based light signals, expanding compact point sources into extended radiance patterns observable by satellites.