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首页> 外文期刊>Aquatic Sciences >Persistent weak thermal stratification inhibits mixing in the epilimnion of north-temperate Lake Opeongo, Canada
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Persistent weak thermal stratification inhibits mixing in the epilimnion of north-temperate Lake Opeongo, Canada

机译：持久的弱热分层抑制了加拿大北温带湖Opeongo上层的混合

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摘要

Persistent weak temperature stratification characterizes the epilimnion of Lake Opeongo, Ontario, Canada, and reduces the magnitude of turbulent mixing. Throughout July and August 2009, the epilimnion was isothermal for only 34 % of the record, while for 28 % of the record there was at least a 2 ℃ temperature difference across the 5 m deep epilimnion. During these stratified periods, there were increases in gradient Richardson numbers (Ri_g), and decreases in rates of dissipation of turbulent kinetic energy (ε), the turbulence activity parameter (I = ε/vN~2), an indicator of active mixing, and vertical eddy diffusivity (K_z) inferred from temperature microstructure profiles. During periods of shear induced mixing, values of ε approached 10~(-6) m~2 s~(-3) and decreased during periods of increasing Ri_g. For 0 ＜ Ri_g ＜ 1, average values of I were ~ 1,000 and values of K_z were slightly higher than 10~(-4) m~2 s~(-1). For Ri_g ＞1, average values of I were ～ 300 and K_z was reduced by one to three orders of magnitude. Mixing during cold fronts occurred over time scales of minutes to hours, which worked to erode diurnal thermoclines. However, during periods of persistent secondary thermoclines, mixing was suppressed throughout the epilimnion.
机译：持续的弱温度分层是加拿大安大略湖Opeongo湖的特征，并减少了湍流混合的幅度。在整个2009年7月和2009年8月期间，上扬期等温仅占记录的34％，而在28％的记录中，在5 m深的上期期中至少有2℃的温差。在这些分层期间，理查森梯度数（Ri_g）有所增加，湍流动能（ε），湍流活动参数（I =ε/ vN〜2）（主动混合的指标）的耗散率降低了，从温度微观结构轮廓推断出垂直涡流扩散率（K_z）。在剪切诱导的混合过程中，ε值接近10〜（-6）m〜2 s〜（-3），在Ri_g增加的过程中减小。当0 ＜Ri_g ＜1时，I的平均值为〜1,000，K_z的值略高于10〜（-4）m〜2 s〜（-1）。当Ri_g＞ 1时，I的平均值约为300，而K_z减小1-3个数量级。冷锋期间的混合发生在几分钟到几小时的时间范围内，这有助于侵蚀昼夜温床。但是，在持续的次生高温跃迁期间，整个上层期都抑制了混合。

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  • 来源
    《Aquatic Sciences》 |2014年第2期|187-201|共15页
  • 作者

    Patricia Pernica; Mathew G. Wells; Sally MacIntyre;

  • 作者单位

    Department of Physical and Environmental Sciences, University of Toronto, Toronto, ON M1C1A4, Canada;

    Department of Physical and Environmental Sciences, University of Toronto, Toronto, ON M1C1A4, Canada;

    Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA 93106-9620, USA;

  • 收录信息 美国《科学引文索引》(SCI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Environmental fluid dynamics; Stratification; Turbulence; Mixing;

    机译：环境流体动力学;分层;湍流混合;

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