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

Abstract

 The Southeasterly Gale in Xinjiang, China is a severe local gale weather phenomenon which occasionally happens near the northwest opening of 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 gust speed that reached 30 m s^-1. The gale lasted for over 24 hours making it the strongest wind in latest 20 years. Through observations and numerical simulation, this study represents the formation of this southeasterly gale incident. The large-scale topographic forcing of the Tianshan Mountains led to the intensification of pressure gradient across the Tianshan Grand Canyon, and therefore an advantageous condition for the generation of the southeasterly gale had been provided. When air currents travelled through the canyon, a critical layer with zero wind velocity was established, and nonlinear process was activated by orographic forcing. It is suggested that air current sank on the northwest opening of the canyon due to unstable stratification and thus strengthened the gale.