PNNL

Abstract

The phase composition and microphysical structure of clouds define the manner in which they modulate atmospheric radiation and contribute to the hydrologic cycle. Issues regarding cloud phase balance and transformation come to bear directly in mixed-phase clouds, and have been difficult to address within current modeling frameworks. Groundbased, remote-sensing observations of mixed-phase clouds can contribute a significant body of knowledge with which to better understand, and thereby more accurately model, clouds and their phase-defining processes. Utilizing observational case studies from the Mixed-Phase Arctic Cloud Experiment (M-PACE), which occurred at the D.O.E. Atmospheric Radiation Measurement (ARM) Program’s atmospheric observatory in Barrow, Alaska during autumn 2004, we review the current status of ground-based observation and retrieval methods towards characterizing the macrophysical, microphysical, radiative, and dynamical properties of mixed-phase clouds. In general, cloud phase, boundaries, ice properties, liquid water path, optical depth, and vertical velocity are available from a combination of active and passive sensors. Significant deficiencies exist in our abilities to vertically characterize the liquid phase, to distinguish the ice crystal habits, and to understand the aerosol-cloud interaction in mixed-phase clouds.