一次垂直切变不稳定背景下的重力波过程分析

Analysis on a gravity wave process under vertical shear instability environment

利用常规气象观测数据以及再分析资料,对2022年1月30—31日,广西中部至南部出现大面积具有波动特征的带状回波过程中重力波的发展及传播进行了诊断分析。结果表明:(1)此过程广西受南支槽前西南急流控制,强垂直风切变为重力波的发展提供了扰动背景。广西位于锋面冷空气一侧,低层静力稳定层结为重力波的传播提供了必要条件。(2)此过程受到周期为5~7h的重力波影响。在过程初期,切变不稳定增强对重力波具有激发作用。在波动成熟和维持阶段,基本气流向重力波的能量输送,弥补了波动传播过程中的能量耗散。Richardson数具有较好的指示意义。(3)波动中的上升运动将水汽向高层输送,潜热加热的正反馈以及不稳定能量释放使得重力波的抬升扰动可以延展至更高层次。

Based on the conventional observation and reanalysis data, the development and propagation of gravity wave in the process of large-area band echo with fluctuating characteristics from central to southern Guangxi from January 30 to 31, 2022 were diagnosed and analyzed. The results showed that(1) Guangxi was controlled by the southwest jet in front of the south branch trough during the whole process, and the strong vertical wind shear provided the disturbance background for the development of gravity waves. On the cold side of the front, the static stable layer in low level provided the necessary conditions for gravity wave propagation.(2)Wavelet analysis showed that the process was affected by gravity waves with a period of 5~7h. In the early stage of the process, the enhanced shear instability excited the gravity wave. During the wave maturation and maintenance stage, the energy transferred from the basic flow to the gravity wave compensating the energy dissipation by the wave propagation. The Richardson number has a good indicative significance in the above process.(3) The upward motion of the wave transported water vapor to the upper level, and the positive feedback of latent heating and unstable energy release made the gravity wave uplifting disturbance extend to a higher level.