Gerber/Abstract The objectives of this research are two-fold; (1) to analyze existing observations of cloud liquid water using a new optical device (PVM-100A) capable of high frequency sampling (2KHz), including the direct measurement of effective radius (volume divided by surface area). The high frequency measurements of liquid water (in Cumulus and stratorcumulus clouds) should illuminate the physics of entrainment; the effective radius seems to be a useful variable for radiative transfer and remote sensing applications; (2) to participate in a field experiment (SHEBA) devoted to the cloud physics of (summer) Arctic stratus, a cooperative program