Aerosol semi-direct effect is the adjustment of the radiative budget due to the cloud response to radiation absorption. Although dust accounts for about a third of aerosols’ shortwave absorption, our understanding of its semi-direct effect often relies on traditional shortwave-focused mechanisms previously established for biomass-burning aerosols, and implications of dust longwave absorption on clouds have not yet been fully explored. In this presentation, I will highlight how low-level cloud cover responds to changes in the properties and characteristics of free-tropospheric dust layers over the North Atlantic Ocean. I will show that while low-level cloud cover generally increases beneath Saharan dust layers—consistent with the mechanism of aerosol semi-direct effect—this cloud enhancement weakens with variations in dust-layer properties, including dust optical depth, geometric thickness, base height, size distribution, and refractive indices. I will argue that the weakened cloud response is primarily driven by increased dust-induced longwave-dominated warming at cloud top, which counteracts the typical cloud-top radiative cooling. Overall, our results expand the traditional mechanism of aerosol semi-direct effects by emphasizing the important role of dust longwave effects in modulating marine cloud cover, thereby deepening our understanding of dust–cloud–radiation interactions in Earth’s climate system.