The influence of stratospheric potential vorticity on baroclinic instability
The influence of stratospheric potential vorticity on baroclinic instability
复制标题
平流层位涡对斜压不稳定的影响
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
R. K. Scott
中科院分区：
文献类型：
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作者：
L. A. Smy;R. K. Scott
本文通过考虑平流层位涡的直接扰动对中纬度斜压不稳定演变的影响，在Eady模式的简单推广中考察了平流层和对流层之间的动力耦合。在平流层位涡完全为零的模拟中，同时考虑了纬向对称和非对称扰动对平流层位涡的影响，前者代表了强极涡，后者代表了一次重大突然变暖后的平流层状态。这两种类型的平流层扰动都会导致天气尺度的地表温度演变以及纬向和全球平均对流层数量的显著变化。在纬向对称扰动的情况下，所有不稳定模态的线性增长率随扰动幅度的增加而减小。具有明显不对称扰动情况下的初始增长率也比对照情况弱，但由于初始平流层扰动触发的低纬向波数的增长，最终涡动能值要大得多。对纬向对称扰动和非对称扰动的比较，有助于深入了解突变变暖前后条件对对流层演化的可能影响。版权所有©2009英国皇家气象学会
This article examines the dynamical coupling between the stratosphere and troposphere by considering the effect of direct perturbations to stratospheric potential vorticity on the evolution of midlatitude baroclinic instability in a simple extension of an Eady model. A simulation in which stratospheric potential vorticity is exactly zero is used as a control case, and both zonally symmetric and asymmetric perturbations to the stratospheric potential vorticity are then considered, the former representative of a strong polar vortex, the latter representative of the stratospheric state following a major sudden warming. Both types of stratospheric perturbation result in significant changes to the synoptic‐scale evolution of surface temperature, as well as to zonally and globally averaged tropospheric quantities. In the case of a zonally symmetric perturbation, the linear growth rate of all unstable modes decreases with increasing perturbation amplitude. Initial growth rates in cases with significant asymmetric perturbations are also weaker than those of the control case, but final eddy kinetic energy values are much larger due to the growth of low zonal wavenumbers triggered by the initial stratospheric perturbation. A comparison of the zonally symmetric and asymmetric perturbations gives some insight into the possible influence of pre‐ or post‐sudden‐warming conditions on tropospheric evolution. Copyright © 2009 Royal Meteorological Society