The Impact of Vertical Resolution at Different Levels on the Numerical Simulation of the Torrential Rain in Guangzhou on 7 May 2017

Refined vertical resolution can better reflect atmospheric dynamics-thermodynamics environment and evolution processes of mesoscale systems. The impact of vertical resolution on the mechanism of trigger and development of convective systems in the warm sector needs to be studied further. This study simulated the local burst torrential rain that occurred in Guangzhou on 7 May 2017 using the WRFV3.9.1 model driven by the GFS data. Several sensitivity experiments have been conducted with varying vertical resolution in different levels of the troposphere to illustrate the impact on local trigger, back-building and organizing processes during this rainstorm. The simulated results show that the experiment with higher vertical resolution at low levels (LOW62) simulated stronger southerly returning flow, easterly winds, low-level wind convergence and temperature disturbance, which led to a stronger convective trigger. Higher vertical resolution at the middle levels (experiment MID68) was favorable for a wide range of strong dry and cold air intrusion into the convective system. The released latent heat and instability energy may be two important reasons for the development of convective system. Higher vertical resolution at upper levels (experiment UPP71) not only well described the upper divergence centers related to the outflow of upper level jet of the upper convective system, but also well simulated other high divergence centers around the convective system .