垂直分辨率对广州"5·7"特大暴雨数值模拟影响的研究

精细化的垂直分辨率能够更好地反映大气动热力环境和中尺度系统生消演变过程,不同层次高度垂直分辨率的加密对暖区对流系统触发及组织发展机制的影响有待深入研究。本文针对2017年5月6日（UTC）广州局地突发的特大暴雨受复杂地形影响、其对流中尺度系统局地触发、后向传播及组织化的特点,运用WRFV3.9.1,采用GFS资料较好地模拟和再现了此次大暴雨过程,并进行了不同高度垂直分辨率的敏感性试验,以探究垂直分辨率对此次暖区暴雨触发及组织化过程的影响。结果表明:低层垂直分辨率加密试验能够模拟出更强的偏南回流、偏东风和较强的低层风场辐合以及较强的温度扰动,进而引起更强的对流触发;中层垂直分辨率加密更有利于大范围的强干冷空气侵入对流系统,其造成的潜热和不稳定能量的释放,是对流系统发展的重要原因;高空垂直分辨率的加密试验则描述出了对流系统上部与高空急流出流相关的高空辐散中心、对流系统周围的高空强辐散中心以及相邻对流单体的垂直环流,细致再现了对流单体合并为对流系统的组织化过程。

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 .