Triggering Mechanism of an Extreme Rainstorm Process near the Tianshan Mountains in Xinjiang, an Arid Region in China, Based on a Numerical Simulation

Yong Zeng,Lianmei Yang

doi:10.1155/2020/8828060

Abstract

The current study investigated the triggering mechanism of a record-breaking heavy rain process in the area near the Tianshan Mountains in Xinjiang, an arid region in China, from July 31 to August 1, 2016, based on the simulation using the Weather Research and Forecasting (WRF) model. The results illustrated that the rainstorm system was generated in the middle atmosphere of the western Aksu region near the Tianshan Mountains and gradually evolved into a multicell linear echo during system evolution. The cold air transported from the Tianshan Mountains partly reached the low altitudes during the downhill process, and the warm southwest air from Aksu was lifted, forming oblique updraft airflow. The other part of the cold air converged with the southeastern warm air in the middle atmosphere, and the transportation and convergence of the water vapor related to the southwestern, southeastern, and oblique updraft airflows provided good water vapor conditions for the storm system. Meanwhile, the inclined upward air transported cloud water and ice-phase particles to high altitudes, mixing the two and generating a large amount of supercooled cloud water, which was very beneficial for the development and maintenance of the storm system. These conditions were favorable for power, heat, water vapor, and water condensate particles, which enabled the development and maintenance of the rainstorm system on the convergence line, thus triggering this rare rainstorm process during the movement to the northeast.

Highlights

Under the background of global warming, extreme heavy rainfall shows an increasing trend, which has an important impact on arid regions [1,2,3]
A rare rainstorm process in the area near the Tianshan Mountains in China under the background of an arid climate was investigated based on numerical simulation
By studying the different performances of the rainstorm system in different stages of evolution, the trigger mechanism of the storm was revealed from the evolution of power, heat, water vapor, and water condensate particles, and the trigger mechanism is significantly different from other parts of China. e warm-sector heavy rainfall in South China is mainly caused by terrain uplift and near-ground air instability in the afternoon induced by heating via solar radiation [42], and the combined effect of urban heat islands, sea breezes, and the terrain is the key to the rainstorm [43]. e heavy rain in the Yangtze–Huai River basin is closely related to the mesoscale convective system on the Meiyu front [44, 45]

Summary

Research Article

Triggering Mechanism of an Extreme Rainstorm Process near the Tianshan Mountains in Xinjiang, an Arid Region in China, Based on a Numerical Simulation. E current study investigated the triggering mechanism of a record-breaking heavy rain process in the area near the Tianshan Mountains in Xinjiang, an arid region in China, from July 31 to August 1, 2016, based on the simulation using the Weather Research and Forecasting (WRF) model. E cold air transported from the Tianshan Mountains partly reached the low altitudes during the downhill process, and the warm southwest air from Aksu was lifted, forming oblique updraft airflow. E other part of the cold air converged with the southeastern warm air in the middle atmosphere, and the transportation and convergence of the water vapor related to the southwestern, southeastern, and oblique updraft airflows provided good water vapor conditions for the storm system. The inclined upward air transported cloud water and ice-phase particles to high altitudes, mixing the two and generating a large amount of supercooled cloud water, which was very beneficial for the development and maintenance of the storm system. ese conditions were favorable for power, heat, water vapor, and water condensate particles, which enabled the development and maintenance of the rainstorm system on the convergence line, triggering this rare rainstorm process during the movement to the northeast

Introduction

Results

Discussion and Conclusions