Determination of the decoupling degree and cloud-base updrafts of marine stratocumulus using satellite and the MAGIC campaign data
Authors
Zhanqing Li — University of Maryland
Youtong Zheng — Geophysical Fluid Dynamics Laboratory/Princeton University
Daniel Rosenfeld — The Hebrew University of Jerusalem
Category
Warm low clouds, including aerosol interactions
Description
To what extent the surface-originated aerosols impact boundary layer warm clouds is influenced by the degree of cloud-surface coupling and the cloud-base updrafts. Neither of these two variables, however, is retrievable from satellite. This study concerns itself with developing satellite-based methods of inferring the decoupling degree and the cloud-base updrafts for marine stratocumulus (Sc) over subtropical oceans. The estimation concept of the coupling state is that decoupled Sc clouds under cold-advection conditions, which are typical in subtropical oceans, are fed by spreading of the tops of cumulus clouds that are coupled. The cumulus clouds constitute a much larger liquid water path (LWP) over small areas, which is identified by a positive skewness of the LWP, a quantity measurable from high-resolution satellite data. We estimate the cloud-base updrafts by quantifying the cloud-top radiative cooling rate that, in combination with the decoupling degree, determines the turbulence level at the cloud bases. These concepts and the satellite-based estimations are supported by ship measurements over the northeast Pacific during the Marine Atmospheric Radiation Measurement (ARM) Global Energy and Water Cycle Experiment-Cloud System Study-Pacific Cross-section Intercomparison Investigation of Clouds (MAGIC) field campaign. Preliminary results of applying these new techniques to studying the aerosol-cloud interactions will be shown.
