Mixing rates calculated from potential vorticity
Mixing rates calculated from potential vorticity
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根据位涡计算混合率
DOI：
10.1029/jd093id05p05221
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发表时间：
1988
影响因子：
--
通讯作者：
J. Rosenfield
中科院分区：
文献类型：
--
作者：
P. Newman;M. Schoeberl;R. A. Plumb;J. Rosenfield
利用通量和位涡梯度来计算水平混合系数(Kyy和Kyz)。结果表明，中纬到极地的混合系数依赖于非地转风的使用。地转风产生的Kyy值在极地附近大部分为负值，这意味着涡旋对位涡的逆梯度输送，而非地转风产生的Kyy值大多为正值。北半球冬季平流层中上层、南半球春季平流层中上层、对流层南北半球对流层均有较大的Kyy值(超过106m2 S−1)。作为一种替代方法，还利用位涡通量和剩余环流之间的动量平衡计算了Kyy值。平流层上层的这些剩余环流平衡的Kyy值比由位涡通量和梯度确定的值要大得多。这种差异可能是上层平流层和下层中间层重力波破裂的结果。
The flux and the gradient of potential vorticity are used to calculate horizontal mixing coefficients (Kyy and Kyz). It is found that the mid-latitude to polar mixing coefficients depend on the use of nongeostrophic winds. Geostrophic winds yield Kyy values which are largely negative near the polar region, implying counter-gradient transport of potential vorticity by eddies, while nongeostrophic winds yield Kyy values which are mostly positive. Typically, large Kyy values (in excess of 106 m2 s−1) are found in the middle to upper stratosphere during winter in the northern hemisphere, the middle to upper stratosphere during spring in the southern hemisphere, and the troposphere for both northern and southern hemispheres. As an alternative procedure, Kyy values have also been calculated using the momentum balance between the flux of potential vorticity and the residual circulation. These residual circulation balanced Kyy values in the upper stratosphere are much larger than those determined from the potential vorticity fluxes and gradients. This difference may be a result of breaking gravity waves in the upper stratosphere and lower mesosphere.