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Effects of a sharp change of emergent vegetation distributions on thermally driven flow over a slope

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Abstract

In this study, thermally driven flow within a sharp change of rooted emergent vegetation distributions is discussed. A conceptual and linear model is developed to study the interferences and competitions between two forcing mechanisms (vegetation shading and sloping bottom effects) on circulation patterns. The two forcing mechanisms can counteract or reinforce each other according to the presence of emergent vegetation in shallow or deep regions. For tall vegetation in shallows and open water in deep regions, vegetation shading leads to opposite temperature gradients against those from a slope. A critical vegetation blockage \(B_{\textit{critical}}\) is found to cause a minimum horizontal exchange flowrate and divide the flow regime as topographic or vegetation shading dominated. In clear water, opposite circulation from the bottom is produced and gradually spreads to the whole water column. On the contrary, in turbid water, the opposite circulation emerges from the water surface and gradually propagates to the sloping bottom. The circulation in turbid water is more easily affected by a sharp change of vegetation distributions rather than clear water. For open in shallows and tall vegetation in deep water, pressure gradients from vegetation shading can enhance buoyancy from the sloping bottom and lead to greater horizontal exchange flowrates. Due to a sharp change of emergent vegetation distributions, horizontal exchange flowrates are possibly increased and greater than those without vegetation. In short, circulation patterns and strength can be significantly affected by a sharp change of emergent vegetation distributions.

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Acknowledgments

The authors would like to thank funding support from the National Chiao-Tung University of Taiwan and National Science Council of Taiwan through grants NSC 102-2218-E-009-005. The authors thank two anonymous reviewers and Dr. H.J.S. Fernando, Editor-in-Chief, for their helpful comments and suggestions for improvement of the paper.

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Authors and Affiliations

  1. Ocean College, Zhejiang University, Hangzhou, 310058, Zhejiang, China

    Ying-Tien Lin

  2. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Ocean Hall, Zijingang Campus, Zhejiang University, Hangzhou, 310058, Zhejiang, China

    Ying-Tien Lin

  3. Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA

    Chin H. Wu

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  1. Ying-Tien Lin
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  2. Chin H. Wu
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Correspondence to Ying-Tien Lin.

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Lin, YT., Wu, C.H. Effects of a sharp change of emergent vegetation distributions on thermally driven flow over a slope. Environ Fluid Mech 15, 771–791 (2015). https://doi.org/10.1007/s10652-014-9382-z

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  • DOI: https://doi.org/10.1007/s10652-014-9382-z

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