Predictive Capabilities of a One-Dimensional Convective Cloud Model with Forced Lifting and a New Entrainment Formulation

Mladjen Curić Institute of Meteorology, University of Belgrade, Belgrade, Yugoslavia

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Dejan Janc Institute of Meteorology, University of Belgrade, Belgrade, Yugoslavia

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Abstract

A one-dimensional time-dependent nonhydrostatic convective cloud model, with an entrainment formulation that includes the combined effects of turbulent and organized dynamic processes and forced lifting, is used to improve the forecasting of maximum cloud-top heights for application in the hail suppression program of the Hydrometeorological Service of Serbia. The model is focused on the comparison between simulated and observed cloud-top heights for 50 nocturnal thunderstorms, using four different entrainment rates.

It is shown that the model results are highly dependent on the entrainment formulation used. The correlation coefficient r between predicted cloud-top heights and radar echo tops varies from 0.48 to 0.90 depending on the entrainment rate. The most acceptable model results are obtained for the entrainment rate that dominates the dynamic process (r = 0.89). The forced lifting slightly increases the correlation coefficient (r = 0.90) since it tends to improve predicted cloud tops with heights between 8.5 and 11 km.

Abstract

A one-dimensional time-dependent nonhydrostatic convective cloud model, with an entrainment formulation that includes the combined effects of turbulent and organized dynamic processes and forced lifting, is used to improve the forecasting of maximum cloud-top heights for application in the hail suppression program of the Hydrometeorological Service of Serbia. The model is focused on the comparison between simulated and observed cloud-top heights for 50 nocturnal thunderstorms, using four different entrainment rates.

It is shown that the model results are highly dependent on the entrainment formulation used. The correlation coefficient r between predicted cloud-top heights and radar echo tops varies from 0.48 to 0.90 depending on the entrainment rate. The most acceptable model results are obtained for the entrainment rate that dominates the dynamic process (r = 0.89). The forced lifting slightly increases the correlation coefficient (r = 0.90) since it tends to improve predicted cloud tops with heights between 8.5 and 11 km.

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