THE INFLUENCE OF DEEP CUMULUS CONVECTION ON LARGER-SCALE FLOW DURING AVE/SESAME I, 10-11 APRIL 1979 (ATMOSPHERIC VARIABILITY EXPERIMENT - SEVERE ENVIRONMENTAL STORMS MESOSCALE)

THOMAS QUENTIN CARNEY, Purdue University

Abstract

A new formulation of the Eulerian kinetic energy budget equation which contains terms representing interactions between features on different scales of motion is developed and applied to a high-resolution upper air data set. The data were observed in the central United States over a 24-h period during the Atmospheric Variability Experiment-Severe Environmental Storms and Mesoscale Experiment (AVE/SESAME) on 10-11 April 1979. Three-hourly soundings were taken. Two data sets were produced using Barnes' (1964, 1973) objective analysis scheme: one based on observations from 39 stations (SES), which included 23 NWS and 16 supplementary stations, and the other based on observations only at the NWS stations. Kinetic energy budget results are examined for five regions: the total analysis area; the whole convection area which is fixed and contains most of the convective activity during the 24-h period; and three sub-areas, one containing the most intense convection (CB1), one containing weaker convection downwind of CB1 (CB2), and one containing no convection downwind of CB2 (NC). Results are produced for the total (SES) and large-scale (NWS) fields, and for the interacting scale between these two ((delta)-scale). The most energetically-active regions are those containing convective systems. In most cases, large-scale processes dominate; however, scale-interaction processes are important in the generation and dissipation terms throughout the period and in the horizontal transport term after intense convection is occurring. Furthermore, the significant scale-interaction effects generally occur in the upper troposphere (400-100 mb). Results show that scale-interaction processes are causing significant generation of kinetic energy in CB1 and CB2, as well as dissipation of energy to subgrid scales. The major interaction horizontal advection term is contributing to export of energy away from CB1 and CB2. The NC area is characterized by much weaker scale-interaction processes. Analyses of the 400-100 mb layer distributions for the major interaction terms show that thunderstorms appear to be responsible for significant changes in (delta)-scale wind and height components which, in concert with pre-existing large-scale wind and mass fields, are causing the observed interaction effects.

Degree

Ph.D.

Subject Area

Atmosphere

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