PERFORMANCE AND APPLICATION OF RADAR WIND PROFILE AND GROUND-BASED MICROWAVE RADIOMETER DATA IN TORRENTIAL RAIN EVENTS IN URUMQI, AN ARID REGION IN CHINA

摘要

A deeper understanding of the dynamic changes in the atmosphere during Urumqi rainstorms is necessary to improve the early warning capabilities for torrential rain in this arid region. Thus, the horizontal wind field and vertical velocity characteristics based on radar wind profile data and the characteristics of atmospheric temperature, relative humidity and water vapor content based on ground- based microwave radiometer data are analyzed during three heavy rain events (labeled process ', process 2 and process 3) that occurred in this region in 2015-2016. The research results suggest the following: the radar wind profile and ground-based microwave radiometer data can record the continuous state of the atmospheric wind field, vertical velocity, temperature, relative humidity, and water vapor density during heavy rain events in this region and can therefore improve the ability to monitor heavy rain at the observation site. The entire atmosphere exhibited northwesterly or northerly wind during process 1, and an obvious shear line was located at 1500 m during process 2. During these two processes, sudden changes in wind direction and increases in wind speed corresponded to short-term heavy precipitation. During process 3, the shear line gradually rose from 1500 m to 5500 m. In all three rainstorms, the vertical speed increased rapidly 1-2 hours before the start of the rainstorms. Furthermore, the vertical speed below 3000 m was more than 6 m/s during process 1 and process 2, and the sinking speed below 1500 m was more than 2 m/s during process 3. For process 1 and process 2, the temperature of the atmosphere increased approximately 2 hours before the start of the rainstorm, and several significant temperature peaks occurred during the entire rainstorm process. For process 3, the temperature of the rainstorm process also increased significantly, but the temperature peaks were not as sharp as those in the other two events. The atmospheric relative humidity increased with fluctuating conditions approximately 1 hour before the start of the three rainstorms, and the region of saturated relative humidity exhibited fluctuations throughout the heavy rain events.Approximately 1-2 hours before the start of the three heavy rain events, the atmospheric water vapor density increased relatively significantly, and water vapor density peaks existed in the form of large fluctuations during the whole process of the heavy rain events. The high-value centers of vertical velocity, atmospheric temperature, relative humidity and water vapor density correspond well to the precipitation in terms of duration and intensity, and all significantly decreased when precipitation weakened and stopped. In short, this study deepens our comprehension of the fine atmospheric structure during rainstorms in Urumqi and is improves the use of radar wind profile and ground-based microwave radiometer data in the analysis of torrential rain in this area.