Meso-Synoptic Scale Interactions during AVE/SESAME II and a Comparison with AVE/SESAME I

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  • 1 Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907
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Abstract

A diagnosis of the scale interactions between areas of organized convective activity and their larger scale environment is presented for AVE/SESAME II, 19–20 April 1979. Two distinct areas of deep convection occurred during the period, one associated with frontal thunderstorms over the Great Plains and Southwest (referred to as CB1) and the other associated with a persistent region of airmass thunderstorms over the Texas–Louisiana Gulf Coast (referred to as CB2). It is found that a significant source of kinetic energy in both areas was the generation of energy due to the interaction between different scales of mass and motion. Furthermore, most of the scale-interaction generation occurred in the upper troposphere during the period of most active convection. In CB1, nearly all of the energy enhancement appears to be due to large-scale flow interesting with mesoscale (thunderstorm-produced) height gradients (referred to as GLD). In CB2, two processes appear to be equally important: GLD and the generation due to mesoscale flow interacting with large-scale height gradients (GDL). In CB1, a comparison is made with previously derived results from AVE/SESAME I which were obtained using the same methodology. Although the SESAME I case was characterized by much stronger dynamical forcing than the present case, the primary physical mechanism involving enhancement of kinetic energy due to scale interactions (i.e., large-scale flow down the mesoscale height gradient), was a common feature in both cases The results from SESAME I and II strongly suggest that a moderate increase in upper air sounding data can help quantify important physical processes in areas of active convection.

Abstract

A diagnosis of the scale interactions between areas of organized convective activity and their larger scale environment is presented for AVE/SESAME II, 19–20 April 1979. Two distinct areas of deep convection occurred during the period, one associated with frontal thunderstorms over the Great Plains and Southwest (referred to as CB1) and the other associated with a persistent region of airmass thunderstorms over the Texas–Louisiana Gulf Coast (referred to as CB2). It is found that a significant source of kinetic energy in both areas was the generation of energy due to the interaction between different scales of mass and motion. Furthermore, most of the scale-interaction generation occurred in the upper troposphere during the period of most active convection. In CB1, nearly all of the energy enhancement appears to be due to large-scale flow interesting with mesoscale (thunderstorm-produced) height gradients (referred to as GLD). In CB2, two processes appear to be equally important: GLD and the generation due to mesoscale flow interacting with large-scale height gradients (GDL). In CB1, a comparison is made with previously derived results from AVE/SESAME I which were obtained using the same methodology. Although the SESAME I case was characterized by much stronger dynamical forcing than the present case, the primary physical mechanism involving enhancement of kinetic energy due to scale interactions (i.e., large-scale flow down the mesoscale height gradient), was a common feature in both cases The results from SESAME I and II strongly suggest that a moderate increase in upper air sounding data can help quantify important physical processes in areas of active convection.

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