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<br />by Stommel's (1947) empirical (0.2/R) relationshi.p, where R is the updraft <br /> <br />radius in meters. The radii used were: 0.5, 1.0, 1.5, 2.0, 3.0, and <br /> <br />10.0 km. The larger radii, 2.0, 3.0, and 10.0 km, were assumed to simulate <br /> <br />larger cumulus congestus and cumulonimbus cloud systems; whereas, the <br /> <br />1 <br />I <br /> <br />smaller radii, 0.5 to 1.5 km, simulated smaller convective clouds with <br /> <br />larger amounts of entrainment which reduced cloud development. The <br />dynamics of a steady-state entraining jet also limit the model by not <br />explicitly simulating the effects of cloud-top mixing (Scorer, 1958; <br />Levine, 1959). The explicit effects of vertical wind shear and interac- <br /> <br />tions between adjacent cells as in mesoscale lines are not simulated. <br /> <br />The model objectively determines the buoyancy of a parcel, then adds, in <br />a parameterized form, the effect of precipitation drag and cooling effects <br />of mixing to determine the highest level to which a parcel of given radius <br />may be expected to rise under the initial conditions imposed by an observed <br />rawinsonde, cloud-base height, and updraft radius. Simpson and Wiggert <br />(1971) in Florida, Dennis et al. (1975) in South Dakota, and Matthews <br /> <br />and Henz (1975) in Colorado used aircraft and radar observations to <br /> <br />confirm the reliability of these models for diagnosing the potential for <br /> <br />convective development. However, caution should be used in extrapolating <br />results to other areas and periodS because model results are highly <br />dependent on the rawinsonde input data. <br /> <br />c. Predicted vs. Observed Cloud Occurrences <br /> <br />, <br />The model results were compared with cloud observations, as indicated from <br /> <br />satellite imagery, to determine how often the model over- and under- <br />predicted the presence of convective cl~uds. Previous studies (Weinstein, <br />1975a) failed to check the existence of clouds. <br /> <br />10 <br />