Sensitivity of Convective Cloud Growth to Mesoscale Lifting: A Numerical Analysis of Mesoscale Convective Triggering

David A. Matthews Office of Atmospheric Resources Management, Water and Power Resources Service, Denver, CO 80225

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Bernard A. Silverman Office of Atmospheric Resources Management, Water and Power Resources Service, Denver, CO 80225

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Abstract

Numerical model simulation of mesoscale lifting of the convective environment indicates that the ability of the environment to develop deep moist convection increases as mesoscale lifting increases. Mesoscale lifting produces increases in modeled cloud development (cloud depth, cloud-top height, number of clouds, etc.) in most of the samples of 232 summer soundings observed in the High Plains as part of HIPLEX (High Plains Cooperative Program). These increases were statistically significant at the P = 0.001 level in most cases. The effect of lifting was found to vary geographically from north to south over the High plains.

On days when convective cloud lines and clusters were observed in satellite imagery, model simulations produced deep convection only when mesoscale released the conditional instability. On days when isolated convective clouds or clear skies prevailed, model simulations produced less intense convective development; however, lifting was often required to supplement surface heating to produce clouds on these days. These results suggest that the model may be used to determine a convective potential index of the effects of lifting on cloud development, provided there is a means for determining the magnitude of mesoscale velocities.

Abstract

Numerical model simulation of mesoscale lifting of the convective environment indicates that the ability of the environment to develop deep moist convection increases as mesoscale lifting increases. Mesoscale lifting produces increases in modeled cloud development (cloud depth, cloud-top height, number of clouds, etc.) in most of the samples of 232 summer soundings observed in the High Plains as part of HIPLEX (High Plains Cooperative Program). These increases were statistically significant at the P = 0.001 level in most cases. The effect of lifting was found to vary geographically from north to south over the High plains.

On days when convective cloud lines and clusters were observed in satellite imagery, model simulations produced deep convection only when mesoscale released the conditional instability. On days when isolated convective clouds or clear skies prevailed, model simulations produced less intense convective development; however, lifting was often required to supplement surface heating to produce clouds on these days. These results suggest that the model may be used to determine a convective potential index of the effects of lifting on cloud development, provided there is a means for determining the magnitude of mesoscale velocities.

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