Numerical case study of a clear-air turbulence event over the Tibetan Plateau

The Tibetan Plateau is known as the “Third Pole”. However, there are few studies on clear-air turbulence (CAT) event over the Tibetan Plateau. On 11 February 2023, a severe clear-air turbulence (CAT) event occurred along Lhasa-Chongqing route. To verify the role of mountain waves in this aircraft turbulence event, using ERA5 reanalysis data and the Weather Research and Forecasting (WRF) Model, the characteristics and generation mechanisms of this event are investigated. In synoptic features, the warm advection in the lower troposphere benefits the atmospheric instability, promoting the development of atmospheric turbulence. The CAT primarily occurred near the upper-level jet stream core. The significant vertical wind shear decreases the Richardson number (Ri). Kelvin–Helmholtz (K-H) instability with small Ri generates the CAT. To a certain extent, the WRF model can reproduce this turbulence event and accurately simulate the vertical motions over the plateau. Though previous studies indicated that the Tibetan Plateau is one of the main causes of CAT along Sichuan-Tibet route for the complex topography, our results of terrain sensitive experiments reveal that the topography of the plateau has little impact on this turbulence event. Therefore, K-H instability related to tropopause folding is the main mechanism causing this aircraft turbulence.