The Southeasterly Gale in Tianshan Grand Canyon in Xinjiang, China: A Case Study

The southeasterly gale in Xinjiang, China is a severe local weather phenomenon that is occasionally observed near the northwest opening of the Tianshan Grand Canyon. On 8 June 2013, a strong southeasterly gale attacked Urumchi with an average ground wind velocity of 15 m s−1 and wind gusts that reached 30 m s−1. The gale lasted for over 24 h, making it the strongest wind in the last 20 years. Through observations and numerical simulation, this study describes the southeasterly gale's formation. The large-scale, topographic forcing from the Tianshan Mountains led to an intensification of the pressure gradient across the Tianshan Grand Canyon, creating a favorable gale condition. When air currents traveled through the canyon, establishing a critical layer with zero-wind velocity, the orographic forcing activated a non-linear process. The air current sank on the canyon's northwest opening due to unstable stratification which in turn strengthened the gale.