大涡技术对模拟台风眼墙替换过程的影响

眼墙替换是影响台风强度和内核结构的一种重要过程。本研究在高分辨率的数值理想试验中加入大涡模拟技术,对比分析大涡模拟对眼墙替换过程的影响。结果表明:大涡模拟的加入使得模拟台风的强度和边界层入流增强。整个眼墙替换过程共用时约20～22 h,但大涡模拟试验中外眼墙形成更迅速,同时强度和上升运动偏弱。外眼墙完全取代内眼墙之后的台风强度超过替换过程之前的强度。此外,使用大涡技术可以更好地模拟出眼墙替换过程中内外眼墙之间的moat区下沉运动,结构特征与前人观测中所发现的结构特征一致。因此,在台风数值研究中引入大涡模拟技术,有助于更好地模拟眼墙替换过程中的台风结构特征和变化。

The influences of large-eddy simulation on typhoon eyewall replacement

The eyewall replacement cycle plays an important role in changes regarding typhoon intensity and inner-core structure.In this study,in order to investigate the influences of large-eddy simulation(LES) on eyewall replacement,two ideal numerical experiments were conducted,of which one was coupled with LES.The study results indicate that the typhoon intensity of the LES experiment was stronger with larger inflow in the boundary layers.It took the two typhoon approximately 20-22 hours to complete the entire eyewall replacement,but the typhoon in the LES experiment had a faster enclosing of the outer eyewall.At the same time,the intensity and updraft in the outer eyewall were also greater.After the eyewall replacement,the typhoon in the LES experiment continued to intensify,and its intensity became greater than it was before the eyewall replacement.Of more importance is that the LES can more effectively simulate the downdraft within the moat region which is at the outside of the inner eyewall.In addition,the downward motion can more effectively induce the formation and development of convections near the outer eyewall regions,and is in line with the observational features found by previous studies.