The Stirring Tropics: The Ubiquity of Moisture Modes and Moisture-Vortex Instability
The Stirring Tropics: The Ubiquity of Moisture Modes and Moisture-Vortex Instability
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DOI：
10.1175/jcli-d-23-0145.1
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发表时间：
2024-01
影响因子：
4.9
通讯作者：
V. Mayta;Ángel F. Adames Corraliza
中科院分区：
文献类型：
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作者：
V. Mayta;Ángel F. Adames Corraliza
在热带地区对柱水蒸气的观察在时空和时间上显示出显着的变化，表明它受到天气系统通过的强烈影响。假设许多影响系统是水分模式，其热力学由水分控制。在四个客观标准的基础上，结果表明所有海洋对流耦合的热带抑郁样波（TD波）和赤道rossby波都是水分模式。这些模式出现在水平柱水分梯度陡峭而不是柱水蒸气含量高的地方。尽管地理基本状态差异，但水分模式还是由所有盆地的相同机制驱动的。潮湿的静态能量（MSE）异常通过贸易风向西传播。它们的生长取决于背景水分的对流，而异常的子午风和异常辐射加热。色谱柱水分和850 HPA流函数的水平图表明，对流几乎与低级循环部分相交。这种结构和生长过程都表明水分模式是由于水分 - 涡流不稳定性而生长的。最后，时空光谱分析表明，柱水分和低水平的子午风是连贯的，并且表现出与极向潜能传输一致的相位。总的来说，这些结果表明，在热带地区，水分模式无处不在。它们发生在陡峭的水分水分梯度区域，并从水分 - 涡流不稳定性生长，这表明这些梯度本质上是不稳定的，并且可能会连续搅拌。
Observations of column water vapor in the tropics show significant variations in space and time, indicating that it is strongly influenced by the passage of weather systems. It is hypothesized that many of the influencing systems are moisture modes, systems whose thermodynamics are governed by moisture. On the basis of four objective criteria, results suggest that all oceanic convectively-coupled tropical depression-like waves (TD-waves) and equatorial Rossby waves are moisture modes. These modes occur where the horizontal column moisture gradient is steep and not where the column water vapor content is high. Despite geographical basic state differences, the moisture modes are driven by the same mechanisms across all basins. The moist static energy (MSE) anomalies propagate westward by horizontal moisture advection by the trade winds. Their growth is determined by the advection of background moisture by the anomalous meridional winds and anomalous radiative heating. Horizontal maps of column moisture and 850 hPa streamfunction show that convection is partially collocated with the low-level circulation in nearly all the waves. Both this structure and the process of growth indicate that the moisture modes grow from moisture-vortex instability. Lastly, space-time spectral analysis reveals that column moisture and low-level meridional winds are coherent and exhibit a phasing that is consistent with a poleward latent energy transport. Collectively, these results indicate that moisture modes are ubiquitous across the tropics. That they occur in regions of steep horizontal moisture gradients and grow from moisture-vortex instability suggests that these gradients are inherently unstable and are subject to continuous stirring.