Diagnostic Analysis and Radar Echo Features of a Hailstorm Severe Convective Weather Process over the Tibetan Plateau

Through the use of C-band dual-polarization radar datasets from the Third Tibetan Plateau Atmospheric Scientific Experiment, ERA-Interim 0.125°(latitude)×0.125°(longitude) reanalysis data, and conventional meteorological radiosonde data, the diagnostic analysis and radar echo feature extraction of a hailstorm severe convective weather process in the Naqu area of Tibet on the afternoon of 30 Jul 2014 are conducted. Results show that: 1) The hailstorm severe convective weather process occurs during the eastward movement of a plateau vortex accompanied by shear lines. The forward-tilting shear lines at the rear of the vortex provide energy and water vapor for this process. 2) The water vapor provided for the severe convective weather mainly comes from the Bay of Bengal, India, and Nepal, which strengthens significantly before the severe convective weather. The water vapor in the lower layer concentrates below 400 hPa, with obvious convergence and upward transportation. 3) Under the obvious convective instability, energy accumulation, and dynamic uplift conditions below 400 hPa in Naqu, the overlap area of the pseudo-equivalent potential temperature decreases with the height, horizontal convergence, and upward movement. 4) The radar echo images show that the severe convective weather is obviously local and is mainly caused by multiple γ mesoscale isolated convection cells, the movement path of which is consistent with the southwest airflow in front of shear lines. Most of the cells have small horizontal scales and short life, whereas some cells have large horizontal scales and long life. Local airflow convergence may cause the production of new cells, and the occurrence, development, and maintenance of cells depend on the low-level airflow convergence to provide dynamic conditions. 5) The range height indicator shows the characteristics of a weak hail cloud, with the top reaching approximately 16 km but not breaking through the top of the troposphere, which is higher than the general convective clouds in plain areas, and the 0℃ layer being lower than that in plain areas. The cloud indicates deep strong convective precipitation, and the precipitation center is located at the bottom of the cloud, including precipitation and hail dominated by radon particles. Strong inflows and updrafts occur in the vertical direction. The suspended echoes appear above the inflowing updrafts, with the airflow sinking zone below the middle-level convergence zone corresponding to the hail zone. The combination of the middle-level convergence and high-level divergence leads to the upward growth and strong development of convective storms.