The Interplay Between Background Atmospheric Boundary Layer Winds and Downburst Outflows. A First Physical Experiment
This paper studies the interaction between downburst outflows and the background atmospheric boundary layer (ABL) winds close to the surface. Downburst is a buoyancy-driven downdraft of cold air that emerges from cumuliform clouds and results in a vigorous starburst outflows upon reaching the surface. Currently, there are neither satisfactory analytical models nor experimental results on the highly complex interaction between these two wind systems. One of the advanced modes of the WindEEE Dome operation, at Western University in Canada, enables the simultaneous generation of downbursts and ABL winds. In accordance with the WindEEE Dome capabilities, an experiment is designed to address this long-standing question on the relationship between ABL winds and downbursts. This paper shows the interaction between downburst and ABL winds for seven azimuthal positions in respect to the incoming ABL wind direction and six heights. The results show that the traditional approach of adding ABL winds to downburst outflow as either vector or algebraic sum is inaccurate for all heights and azimuth angles. A new empirical relationship between downbursts with and without ABL winds is presented herein.
KeywordsDownburst Thunderstorm Wind simulator Flow interaction WindEEE Dome
The authors thank Julien LoTufo for his technical help in conducting the experiments in the WindEEE Dome. Constructive comments from two anonymous reviewers are highly appreciated.
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