关键词: 强对流, 物理量, 中尺度分析

Abstract:

Based on conventional observation data, mesoscale encryption weather stations data, satellite images and radar products, a local strong convective weather process occurring in centre Shanxi Province on 28 July 2016 was analyzed. The results show that the strong convective weather occurred under the circulation background of northwest airflow behind the vortex. The low-level shear line, surface convergence line and dry line were the main triggering factors of the strong convection weather. The instability of atmosphere increased due to invasion of the lower level cold air, which promoted the vertical upward motion and provided favorable conditions for the development of strong convective weather. Before the occurrence of strong convection, there was an obvious inversion layer on 850 hPa, which was beneficial to the accumulation of energy in low level. The vertical superposition of positive and negative moist potential vorticity in the upper and lower troposphere layer was conducive to the development of symmetrical instability. Strong convective weather happened near moist potential vorticity tongue which was on the edge of moist potential vorticity contour and the junction of warm and cold air. Elliptic hailstorm clouds appearing on the satellite cloud image was the main mesoscale system causing the hail and severe wind weather. Analysis on radar reflectivity factor, there were obvious side lobe echoes and three body scattering spikes, which was a typical characteristic of the hailstones, and it appeared 15-20 minutes before the hail falling. Thunderstorm wind occurred at the head of bow echo and the fracture of strong echo center. Strong echo weakening fast had important indicative significance to the occurrence of thunderstorm gale. According to the radial velocity products of Doppler radar, the medium-strength meso-cyclone and the obvious radial convergence in the middle level were favorable to the occurrence of thunderstorm gale. The leap of the echo top height and the vertically integrated liquid water content indicated that there was a possibility of large hail, at the mean time the rapid decrease of the vertically integrated liquid water content also meant that there was a great potential for thunderstorm gale.

Key words: strong convection, physical quantity, meso-scale analysis