Marine boundary layer (MBL) stratocumulus clouds play a crucial role in the climate system, radiatively cooling the Earth through strong reflectance of incoming shortwave radiation compared to the underlying ocean, with comparatively little impact in the longwave portion of the spectrum due to cloud top temperatures that are not significantly different than the surface. These important cloud types are maintained by turbulence driven by cloud top radiative cooling that generates mixing between the oceanic source of water vapor and the cloudy layer (Hartmann et al., 1992;Klein & Hartmann, 1993;Wood, 2012). When the MBL is shallow (below around 1 km), the boundary layer is generally well-mixed, capped by a strong temperature inversion, and the MBL cloud fractions are greatest (Albrecht et al., 1995). Cloud top evaporative cooling and entrainment of free-tropospheric air into the MBL, among other mechanisms, leads to a deepening of the MBL beyond 1 km, and the longwave cooling at the cloud tops cannot mix the negatively buoyant entrained air through the full depth of the MBL. The cloudy layer can thus become decoupled from the oceanic moisture source, reducing or eliminating mixing through the full depth of the MBL, and reducing cloud fractions (Bretherton & Blossey, 2014;Bretherton & Wyant, 1997). The MBL can also become decoupled through radiative heating of the cloud layer and evaporative cooling in the sub-cloud layer, both processes further stabilizing the MBL and suppressing vertical mixing (Ghate et al., 2013;Nicholls, 1984;Xiao et al., 2011). The details of this decoupling process and how it impacts water vapor transport within the MBL and the exchanges of water vapor between the subcloud layer (SCL), the cloudy layer, and the