1.College of Atmospheric Sciences,Chengdu University of Information Technology;2.Hebei Meteorological Observatory;3.Key Laboratory of Cloud–Precipitation Physics and Severe Storms,Institute of Atmospheric PhysicsLACS
Based on the mesoscale regional numerical modelS(WRF) and spectral nudging method, this study simulates a cold air pool (CAP) process during the 2021 Winter Olympics test competition. In this paper, the vertical change of the wind temperature field during this process has been analyzed, and the specific reasons for the formation and dissipation of the CAP has been revealed. The results show that the stationary synoptic situation is the general background for the maintenance and development of the CAP. During the development of the CAP, the temperature inversion layer was rapidly established from top to bottom, and the southeast cold air flow appeared at the bottom of the valley. Affected by the downward gravitational wind, the cold air accumulated to the bottom of the valley continuously, and the depth of the CAP increased. After sunrise, the large-scale system winds over the mountain was reestablished. The temperature inversion layer was eroded from the bottom, and the structure of the CAP was destroyed. The strong radiation cooling at night time is the main reason for the formation of the CAP. The difference in the intensity of the radiation cooling will cause the difference in the cooling range of the CAP. The sudden enhancement of the radiation cooling after midnight created favorable conditions for the maintenance and development of the CAP in the middle and later periods. By analyzing the evolution of the potential temperature profile, friction velocity and boundary layer height during the process, it can be confirmed that the development of turbulent activity is an important factor in influencing the dissipation of temperature inversion and the destruction of CAP structure.