Boundary layer clouds are a key element in Earth's climate system. Their response and feedback to climate change is a leading source of uncertainty in projecting Earth's radiation budget and climate. This session provides a platform for observational, theoretical, and modeling work on warm, supercooled, and mixed-phase boundary layer clouds from the microscale to the global scale. Topics include mechanisms by which boundary layer clouds interact with climate in the course of trends and variations in atmospheric circulation, temperature, humidity, radiation, and composition. Interactions between natural and anthropogenic aerosol and clouds, mechanisms that link clouds with biological activity, vegetation, and surface processes, and consequences for radiation, precipitation, and climate are of equal interest.