Linear effects of nontraditional Coriolis terms on intertropical convergence zone forced large‐scale flow
Linear effects of nontraditional Coriolis terms on intertropical convergence zone forced large‐scale flow
复制标题
非传统科里奥利项对热带辐合带强迫大尺度流的线性影响
DOI：
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发表时间：
2019
影响因子：
8.9
通讯作者：
P. Roundy
中科院分区：
文献类型：
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作者：
H. Ong;P. Roundy
本文提出了一种通过标度纬向动量方程中的非传统科里奥利项（NCT）来验证流体静力近似的方法。为了证明尺度，这项研究模拟了由指定热源强迫的大尺度流动，使用线性化强迫耗散模型模拟热带辐合区（ITCZ）。该模型解决了两个类似的方程，其中唯一的区别是包括NCT。方程是使用下列近似导出的：滞弹性、赤道β平面、线性化、带状对称、稳定和恒定耗散系数。在纬向-垂直环流、纬向风和位温方面，比较了有无NCT模拟的大尺度流动。这两个结果都类似于Hadley环流。在控制模型参数的情况下，由于忽略NCT，无NCT和有NCT的结果之间的差异产生线性偏差。最突出的偏差是ITCZ加热区出现的西风偏差，因为省略NCT阻止了相关的向西加速度，当加热引起的垂直运动存在时。当ITCZ模拟5月东太平洋ITCZ时，纬向风偏差除以NCT的纬向风偏差，西风最大值为0.120 ± 0.007，均方根值为0.0452 ± 0.0005。这些标准化措施的纬向风偏置增加与较窄的ITCZ或ITCZ更接近赤道，因为一个较弱的副热带急流相同的垂直加热廓线。这种差异可以通过一个无量纲参数来追踪，该参数将NCT与传统的科里奥利项之比进行缩放。缩放鼓励将NCT恢复为全球模型。
This article promotes a measure to validate the hydrostatic approximation via scaling the nontraditional Coriolis term (NCT) in the zonal momentum equation. To demonstrate the scaling, this study simulates large‐scale flow forced by a prescribed heat source, mimicking the intertropical convergence zone (ITCZ) using a linearized forced‐dissipative model. The model solves two similar equations, between which the only difference is the inclusion of NCTs. The equations are derived using the following approximations: anelastic, equatorial beta‐plane, linearized, zonally symmetric, steady, and a constant dissipation coefficient. The large‐scale flows simulated with and without NCTs are compared in terms of the meridional–vertical circulation, the zonal wind, and the potential temperature. Both results appear like the Hadley circulation. With the model parameters controlled, the differences between the results without NCTs and those with NCTs yield the linear biases due to omitting NCTs. The most prominent bias is a westerly wind bias in the ITCZ heating region that emerges because omitting NCTs prevents the associated westward acceleration when heating‐induced vertical motion is present. The zonal wind bias divided by the zonal wind with NCTs is 0.120 ± 0.007 in terms of the westerly maximum and 0.0452 ± 0.0005 in terms of the root mean square (RMS) when the prescribed ITCZ mimics the observed ITCZ in May over the East Pacific. These normalized measures of the zonal wind bias increase with a narrower ITCZ or an ITCZ closer to the Equator, because of a weaker subtropical jet stream given the same vertical heating profile. This difference can be traced by a nondimensional parameter scaling the ratio of the NCT to the traditional Coriolis term. The scaling encourages the restoration of NCTs into global models.