海浪和海洋飞沫对“珊珊”台风影响的数值研究

Numerical study of the effects of ocean waves and sprays on Typhoon “Shan Shan”

  • 摘要: 台风是剧烈的天气系统,在开放的海上强风激起大浪,改变了海表粗糙度,同时,海浪顶端的白泡沫破碎,在海气界面处会出现大量的海洋飞沫。基于共享内存的进程间通信技术应用到区域大气和海浪模式的耦合中,大气模式引入了Fairall和Andreas两种海洋飞沫参数化方案,对2006年“珊珊”台风进行了模拟对比试验,结果表明:耦合模式通过海气相互作用,对台风的强度产生影响,由于耦合模式在海表粗糙度的计算上考虑了海表状况,使得耦合模式模拟的台风强度更接近实况,而对台风的移动路径影响不大;耦合模式中海气相互作用主要通过动力因素来对台风产生影响,海表状况影响了海表粗糙度,从而使台风的动量输送发生变化,具体的台风强度增强还是减弱主要取决于海表状况与实况的符合程度;海洋飞沫参数化主要通过热力场的改变来影响动力场,Fairall方案中潜热通量和感热通量得到很大程度的加强,使得台风的热力结构得以改变,台风强度明显加强,从而影响了动力场结构;Andreas方案由于其界面通量算法在高相对湿度条件下计算界面通量时得到的量值较小,虽然高风速条件下感热通量加大,但总的潜热通量、感热通量较Fairall方案为弱,因此,模拟的台风强度不强;海洋飞沫参数化方案通过影响台风的结构和强度,对台风移动路径产生一定影响。

     

    Abstract: Typhoon is a severe weather system. Over the open sea, strong winds are able to stir up big waves and change the sea surface roughness. When the white foam breaks on the top of waves, a lot of sprays are produced in the airsea interface. Based on the shared memory and semaphores interprocess communications in the Linux system, the coupled mesoscale atmospherewave model is used in the simulation of typhoon “Shan Shan” with the involvement of the Fairall or Andreas sea spray parameterization. The results show that the airsea interaction has influence on the typhoon intensity, but little effect on the typhoon track. Since the coupled model considers the impact of ocean status on the sea surface roughness, the simulated typhoon intensity is closer to the observation than the uncoupled model. The air-sea interaction influences typhoon in terms of dynamic fields and, the momentum flux is changed with the sea surface roughness. Whether the simulated typhoon is realistic or not is largely determined by the matching condition between the simulated ocean status and the observation. The sea spray affects the dynamic structure through thermodynamic fields. The latent and sensible heat fluxes in the Fairall parameterization are significantly increased, which changes the thermodynamic structure of the typhoon and strengthens it. The interface flux calculated via the Andreas parameterization under highrelative humidity conditions is small, and, as a result, although the sensible heat flux is increased under high wind speed conditions, the total latent and sensible heat fluxes via the Andreas parameterization are smaller than those via the Fairall parameterization, resulting in a weaker typhoon. The sea spray has effect on the typhoon track through changes in its structure and intensity.

     

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