MODELING CLOUD FRACTION AND HORIZONTAL VARIABILITY IN MARINE BOUNDARY-LAYER CLOUDS

Boundary layer clouds play an important role in the global energy budg et. The radiative properties of these clouds depend upon the cloud fra ction and the horizontal variability of liquid water path within patch es of unbroken cloud. A simple statistical model for describing the pr obability distributions of liquid water path and cloud fraction in low clouds has been developed. The model is shown to reproduce realistica lly the diurnal cycle in the cloud fraction and horizontal inhomogenei ty of marine stratocumulus. Further, the model produces realistic stat istics for the horizontal variability of liquid water path within boun dary layer clouds. The modeled distributions of cloud liquid water pat h depend upon the cloud fraction, similar to Landsat retrievals. The r esults are discussed in the context of improving the representation of boundary layer clouds in large-scale models.