18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Wednesday, 1 August 2001: 11:14 AM
The influence of moist convection on the predictability of large scales
Fuqing Zhang, NCAR, Boulder, CO; and C. Snyder and R. Rotunno
Since the work of Lorenz, it has been acknowledged that even very small errors at very small scales in initial conditions would, at sufficient lead times, limit the skill of forecasts. We examine this problem explicitly in a limited-area atmospheric model that resolves both moist convection (in specific areas) and meso- and synoptic scales. For a case of significant synoptic scale cyclogenesis, initial perturbations of small scale and small amplitude first alter the timing and position of individual convective cells. These changes later influence the development of the cyclone in both its mesoscale aspects as well as the precipitation differences that arise from small-scale initial perturbations are comparable to those produced by using a different large-scale analysis or by changing the convective parameterization.

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