The DYCOMS-II multi-investigator field program took place during July 2001 near the coast of southern California, with primarily night-time flights to better understand the dynamical and physical processes in nocturnal marine stratus. Aircraft measurements, dropsonde profiles, ocean buoy observations and satellite multispectral data are used to characterize the cloudy marine boundary layer (MBL) and to determine the accuracy of mesoscale model predictions of cloud structure, ocean-air interface processes and marine boundary layer evolution. This study offered the opportunity to examine the variability and predictability of microwave refractivity characteristics in the vicinity of the cloud-topped marine layer, which can adversely influence microwave signal propagation through wave trapping and ducting. Because these conditions are primarily determined by the magnitudes and vertical gradients of temperature and humidity, the representation of microwave refractivity can be enhanced by better knowledge of the structure of the MBL inversion height and strength. This is particularly relevant for the near-coastal ocean margin where microwave signals are used for multiple applications, and where the MBL layer often has a high degree of mesoscale structure. Progress toward improved nowcasting and forecasting of refractivity is made through the combined use of GOES and TRMM satellite data for model initialization of the boundary layer thermodynamic profiles.