Study on the mesoscale structure of the heavy rainfall on Meiyu front with dual-Doppler RADAR

Abstract

This paper retrieves the three dimensional (3D) wind fields and studies the evolution of the 3D wind fields and the formation mechanism of the sudden heavy rainfall on Meiyu front on 26th–27th June 2003 in Huaihe river basin in China, using the volume scan data of the dual-Doppler radar located in Hefei and Maanshan cities. Due to the effect of the low level trough, low level jet and the convergence line at the low and medium levels, it produced a heavy precipitation in Anhui province. It shows clearly that the primary feature of this event is local, sudden and short timed. It is a convective-stratiform mixed cloud precipitation based on the radar echo analyses. The meso-β-scale convective system (MβCS) and the meso-γ-scale system located on the MβCS played an important role on this heavy rainfall. The meso-β-scale convective cloud has high precipitation efficiency. The dual-Doppler retrieved wind reveals that the heavy rainfall was caused by the meso-β-scale convergence lines at the low and the medium levels. The convergence line triggered and maintained the heavy rainfall. There were strong convergence and vorticity at the low and medium levels of the MβCS. The convergence line spread from west to east and the position of the convergence line at the medium levels is westward of the ones at the low levels. When the convergence line at the low and medium levels began to weak, the precipitation began to weak too. The intensity of the precipitation weakened remarkably when the convergence line dissipated. The 3D kinematic conceptual structure model of this heavy rainfall case is also given.