Measurements made by NCAR C-130 in May, 1998 during FIRE Arctic Cloud Experiment focused on the structure and evolution of liquid-ice mixed phase clouds system. The observations made in Flight 4 on May 15 showed a very well defined the low-level mixed-phase cloud. The boundary-layer has lay-ered structures, the clouds occurred in the first layer (0-300 m), and the second layer (400-750 m); each of these layers appeared to be relatively well-mixed in both potential temperature and total water mixing ratio. The maximum liquid water is about 0.2 g/kg and ice water about 0.2g/kg. The turbulence in the surface-based layer is relatively strong and clouds there are quite solid. This observation offers a good case to study the mixed-phase clouds and the layered struc-ture, as well as to test the ability of large-scale models to capture these layered structures. In this work, we present the measurements and use two turbulence-cloud models to study the physical processes involved in the observed cloud system. The basic questions we are asking are: how did the layered structure form, and how the radiation in the mixed-phase clouds affect the dynamic processes ?
The two models are a turbulence-closure coupled with mixed-phase cloud model and a large-eddy simulation model with bulk cloud parameterization. Both models include the radiation parameterization that treats liquid and ice cloud separately. This work is in progress and we will report results in the meeting.
(I am sorry for this very incomplete abstract, because I will be out of country from June 15 - Jul 3, 1998. But I am sure I will modify much better extended abstract in October. Thanks.)