The Dynamics and Microphysics of Mid-level, Mixed-phase Clouds: Results & Current Research

Curtis Seaman
Colorado State University


The Cloud Layer Experiment (CLEX) is an on-going research project funded by the Department of Defense Center for Geosciences/ Atmospheric Research whose goals are to better understand the microphysical and dynamical properties of non-frontal, non-orographic, mid-level, mixed phase clouds (i.e. altocumulus and altostratus) so that we may improve forecasting of this cloud niche. Mid-level clouds of the type examined here are typically thin (< 1km in vertical extent) and mixed-phase with weak vertical velocities (< 1 m/s). They have been shown to cover ~ 22% of the earth's surface at any given time. Their role in climate is poorly understood at present given the dependence of their radiative properties on microphysical structure, however, it has been established that they interfere with military operations and pose a significant aircraft icing risk due to the presence of supercooled liquid droplets.

This presentation will highlight the results from past and current CLEX research, including:

- microphysical, radiative, and dynamical properties of observed altocumulus and altostratus

- goals and preliminary results of the combined CLEX/Canadian CloudSat/CALIPSO Validation Project (Winter 2006/2007)

- current work in the assimilation of GOES humidity-sensitive channels to improve mid-to upper tropospheric humidity in a mesoscale model (RAMS) and the forecasting of CLEX-type clouds