Observing mixed-phase cloud microphysical-dynamical processes at Barrow

Poster PDF

Description

Low-level Arctic clouds are subject to a complex array of microphysical and dynamical processes that often result in layers of cloud liquid water that can persist for long periods of time, at temperatures well below freezing, even in the presence of cloud ice. These microphysical-dynamical processes, which operate at cloud scales, play a key role in determining the overall partitioning of condensate between liquid and ice phases, and thereby determine the cloud microphysical composition. Phase partitioning and microphysical composition ultimately define the impact that clouds have on climatically significant processes such as the atmospheric radiation and hydrologic budgets. A suite of retrieval methods based on cloud radar, lidar, microwave radiometer, infrared spectrometer, and radiosondes have been applied to observations at the North Slope of Alaska site in Barrow to characterize important microphysical and dynamical properties of stratiform mixed-phase clouds. Signatures in derived vertical velocity and turbulence fields reveal important information about the forcing mechanisms that generate buoyancy-driven motions within the clouds. It is found that the characteristic scales-of-motion and the microphysical properties in these clouds are dependent upon the forcing mechanisms. Moreover, relationships between the liquid and ice microphysical properties and the vertical velocity suggest that ice formation within these clouds occurs through droplet-size-dependent mechanisms.