Intermittent Bursting of Turbulence in a Stable Boundary Layer with Low-level Jet |
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| Authors: | Yuji Ohya Reina Nakamura Takanori Uchida |
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| Institution: | (1) Ocean-Atmosphere Dynamics Division, Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan |
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| Abstract: | The atmospheric stable boundary layer (SBL) with a low-level jet is simulated experimentally using a thermally stratified
wind tunnel. The turbulence structure and flow characteristics are investigated by simultaneous measurements of velocity and
temperature fluctuations and by flow visualization. Attention is focused on the effect of strong wind shear due to a low-level
jet on stratified boundary layers with strong stability. Occasional bursting of turbulence in the lower portion of the boundary
layer can be found in the SBL with strong stability. This bursting originates aloft away from the surface and transports fluid
with relatively low velocity and temperature upward and fluid with relatively high velocity and temperature downward. Furthermore,
the relationship between the occurrence of turbulence bursting and the local gradient Richardson number (Ri) is investigated.
The Ri becomes larger than the critical Ri, Ricr = 0.25, in quiescent periods. On the other hand, the Ri number becomes smaller than Ricr during bursting events. |
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| Keywords: | Atmospheric boundary layer Intermittent turbulence Low-level jet Stable stratification Turbulence bursting Wind-tunnel experiment |
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