Determining conditions for stratocumulus clouds at the Azores

 

Authors

Simon Paul de Szoeke — Oregon State University
Sandra Yuter — North Carolina State University
David B. Mechem — University of Kansas

Category

Cloud Properties

Description

High-albedo stratocumulus clouds cover a wide region of the world’s oceans. Despite observations and models that have improved our understanding of marine stratocumulus, numerical weather prediction models rarely predict cloud occurrence better than diagnosis based on lower tropospheric stability (LTS, Klein and Hartmann 1993).

Using marine-cloud observations from the two June–August seasons from the DOE ARM Mobile Facility deployment at the Azores, we diagnose cloud-emergent properties (e.g., fraction, height, and liquid water path) and their internal states (cloud drop number concentration, turbulence, and decoupling) as a function of external forcing parameters. A pair of closely related parameters is LTS and subsidence. We diagnose which of these is a better predictor of cloud fraction and how these large-scale forcings are related to cloud-top turbulence. Controlling for variability explained by the lower-tropospheric soundings, we explore whether observed changes in aerosol concentration measurably affect cloud amount, liquid water path, and cloud optical properties.