EXAMINATION OF COUPLING BETWEEN AN UPPER-TROPOSPHERIC CLOUD SYSTEM AND SYNOPTIC-SCALE DYNAMICS DIAGNOSED FROM WIND PROFILER AND RADIOSONDE DATA

The evolution of synoptic-scale dynamics associated with a middle and upper tropospheric cloud event that occurred on 26 November 1991 is ex amined. The case under consideration occurred during the FIRE Cirrus-I I Intensive Field Observing Period held in Coffeyville, Kansas, during November-December 1991. Using data from the wind profiler demonstrati on network and a temporally and spatially augmented radiosonde array, emphasis is given to explaining the evolution of the kinematically der ived ageostrophic vertical circulations and correlating the circulatio n with the forcing of an extensively sampled cloud field. This is faci litated by decomposing the horizontal divergence into its component pa rts through a natural coordinate representation of the flow. Ageostrop hic vertical circulations are inferred and compared to the circulation forcing arising from geostrophic confluence and shearing deformation derived from the Sawyer-Eliassen equation. It is found that a thermody namically indirect vertical circulation existed in association with a jet streak exit region. The circulation was displaced to the cyclonic side of the jet axis due to the orientation of the jet exit between a deepening diffluent trough and a building ridge. The cloud line formed in the ascending branch of the vertical circulation, with the most co ncentrated cloud development occurring in conjunction with the maximum large-scale vertical motion. The relationship between the large-scale dynamics and the parameterization of middle and upper tropospheric cl ouds in large-scale models is discussed, and an example of ice water c ontents derived from a parameterization forced by the diagnosed vertic al motions and observed water vapor contents is presented.