The most expansive and persistent clouds, reducing the net radiation balance on aannually averaged global basis by 15 W/m2, are the low-lying marine stratocumulus(MSc) which hover over the eastern subtropical oceans. Despite their climatic importance,key processes and feedbacks within the MSc regime have yet to be fully quantiedor understood. The goal of this research is to improve our understanding of MSc processesand their impact on the marine boundary layer (MBL). Specically, using in situaircraft cloud microphysical measurements, this research pays particular attention tothe process of drizzle, the sedimentation of liquid water. Data utilized in this studyprimarily come from the Artium Flight Phase Doppler Interferometer (F/PDI) and theCloud Imaging Probe (CIP) during four days of the Marine Stratus Experiment (MASE)in July 2005 in the northeastern Pacic near Monterey, California. Results presentedin this dissertation are especially unique because of the broad and continuous range inwhich the F/PDI samples (2-100 µm diameter), a size range measured by no other instrumentalone with the same resolution and accuracy. The upper portion of this sizerange, 30 to 100 µm, is of particular importance to the initiation and evolution ofdrizzle but traditionally, has been dicult to measure well.