海洋飞沫对台风强度影响研究

How the sea spray affects the intensity of the typhoon is one of most concerned issues in the world-wide community of physical oceanography. There is still a lack of systematic research on the influence of the thermodynamic and dynamic effects of sea spray on typhoon intensity, due to the difficulty in the observation and the lack of data under typhoon conditions. Research on the heat transfer coefficients under the influence of sea spray is insufficient, and there are great uncertainties and some disputes among different research results, which has not been solved theoretically. So it is difficult to establish a complete parameterization scheme for the air-sea heat flux including the effect of droplets, which brings difficulties to the numerical prediction of typhoons. In view of the above problems, this project intends to use the observation data of advanced GPS dropsonde data during typhoons to analyze the relationship between the heat transfer coefficients under the influence of sea spray and the surrounding environmental factors (such as wind speed, sea surface temperature, air humidity, etc.), and give a parameterized scheme. The effects of thermodynamic, dynamic and comprehensive effects of sea spray on typhoon intensity will be studied using the ocean-wave-atmosphere coupling model. It will provide a strong support for the development and improvement of the ocean-wave-atmosphere coupling typhoon forecasting model so as to improve the accuracy of typhoon intensity forecasting.

海洋飞沫如何影响台风强度是国际上物理海洋学中的热点研究问题。受台风条件下观测困难、资料缺乏的限制，有关海洋飞沫的热力学和动力学效应对台风强度的影响尚缺乏系统的研究；在海洋飞沫影响下的热量交换系数方面，研究较少，不同研究结果之间存在较大不确定性和一些争议，并未从理论上得到根本解决，难以建立完善的包含飞沫效应的海气热量通量参数化方案，这就为台风数值预报带来了难题。针对上述问题本项目拟利用先进的GPS下投式探空仪在台风期间的观测资料，分析飞沫影响下的热量交换系数与周围环境因子（如风速、海表温度、空气湿度等）的关系，给出相应的参数化方案；结合海洋-海浪-大气耦合模式，深入了解海洋飞沫的热力学效应、动力学效应和总体效应对台风强度的影响。为发展和完善台风预报耦合模式进而提高台风强度预报的准确度提供有力支撑。

当代的台风数值预报模式已经可以较好地预报或模拟台风路径，但对台风强度的预报或模拟仍存在较大误差。探其原因，主要是人们对海洋、海浪、大气三者之间的相互作用认识尚不全面和系统，特别是海洋飞沫在海气界面上对海气通量的影响。台风过程中，在风和浪的共同作用下，海面附近出现大量海洋飞沫；海洋飞沫可使海洋与大气之间的动量、热量和水汽交换发生不可忽略的改变，进而对台风强度产生重要影响。但受台风条件下观测困难、资料缺乏的限制，有关海洋飞沫对台风强度影响的探讨尚显不足，难以建立完善的包含飞沫效应的海气通量参数化方案，进而为台风数值预报带来了难题。本项目针对上述问题，利用高风速下风浪水槽内的实验结果，结合海-气-浪耦合数值模式，研究了台风过程中海洋飞沫对动量通量、热量通量及其对台风强度和发展过程的影响，给出了适用于强台风和超强台风的热焓交换系数参数化方案，完善了耦合模式中海气通量参数化方案。研究结果显示，海洋飞沫的热力学效应对热带气旋的影响要显著强于其动力学效应；海洋飞沫的热力学效应可使海气界面间的潜热通量大幅增长，使得热带气旋获得足够的能量发展起来，可使热带气旋强度增强至超强台风级别；在热带气旋的衰减过程中，海洋飞沫效应有利于热带气旋强度的维持，减缓衰减速度。本项目的研究成果有效提高了耦合数值模式对强台风、超强台风的增强和衰减整个发展过程的模拟准确度，减小了强台风和超强台风的强度模拟误差。