【作者】 刘斌；

【导师】 管长龙；

【作者基本信息】 中国海洋大学 ， 物理海洋学， 2007， 博士

【摘要】 探寻海气界面的动量、热量及物质交换过程及其影响机制是海气相互作用研究的核心问题,长期以来都是大气、海洋科学家们关注的热点问题之一。海浪作为海气界面普遍存在的现象,一方面通过海浪状态对海气之间的动量、热量以及物质交换产生重要影响,另一方面海浪的破碎及海面风切削波峰等生成的海面飞沫在海面形成水滴蒸发层,直接或间接地影响着海气界面的动量、热量及水汽通量。准确地理解和参数化海浪状态和海面飞沫对海气间动量和热量通量的影响,是海气相互作用研究的重要课题,是建立大气-海浪耦合模式的基础。基于前人的研究与观测,本文给出了一个同时考虑波浪状态和海面飞沫影响的、适用于从中低风速到极端高风速条件的无量纲海面动力学粗糙度与波龄的关系。新提出关系对应的海面拖曳系数与海面10-m风速的关系同已有的外海和实验室观测数据符合得较好。此关系表明:在中低风速可以忽略飞沫影响时,无量纲的海面粗糙度与波龄并非单调的增减关系,而是随波龄先增大后减小;而在高风速下,飞沫的影响使得海面拖曳系数随风速的增大而不再增大,反而减小;不同波龄对应的海面拖曳系数在风速为25-33 m/s范围时出现极大值。本文还回顾了中低风速下海面标量粗糙度的参数化方法,讨论了大气底层耗散加热效应以及海面飞沫对海气热通量的影响。通过考虑波浪状态对白冠覆盖率的影响给出了适用于气泡生成沫滴的飞沫生成函数,将其同Zhao et al.(2006)受波浪状态影响、适用于飞滴的生成函数连接起来得到了受波浪状态影响、适用于各种半径的飞沫生成函数。进一步将得到的飞沫生成函数应用于Andreas(1992)估计飞沫热通量的方法,同时考虑海面飞沫热力学过程的反馈效应,进而得到了考虑波浪状态影响的飞沫感热和潜热通量的估计方法。由此方法估计的飞沫感热和潜热通量在给定的大气、海面环境条件下,一方面随风速的增大而增大,另一方面相同风速条件下,随波龄和风海雷诺数的增大而增大。基于对大气-海浪模式耦合基础的讨论,本文将新一代天气研究与预报WRF模式和第三代海浪模式WAVEWATCHⅢ耦合起来,建立了一个大气-海浪耦合系统。将耦合系统应用于一个理想台风的模拟中,通过对不同试验方案模拟结果的分析与对比,研究了不同海面动力学粗糙度参数化方案、大气底层耗散加热以及海面飞沫热通量对台风系统的影响。波浪状态对海面粗糙度的影响增大了海面摩擦,减弱了台风强度,减小了台风浪的有效波高,但不同海面粗糙度参数化方案对台风移动路径及海气热通量影响不大;应用本文新提出的海面动力学粗糙度参数化方案时,模拟的理想台风强度相对非耦合的控制试验减弱约5%,最大有效波高减小约6%。大气底层耗散加热效应能增大海气界面总热通量,增强台风的强度,使台风的中心海平面气压加深8-10%,最大海面10 m风速增大6-10%,最大有效波高增大10-15%。海面飞沫热通量能显著地增强台风强度,增大海面风速和海面动量通量以及海面波高;同时海面飞沫热通量直接影响着海气界面的总热量和水汽通量,显著地增大海气界面的潜热和水汽通量。此外,海面状态影响的海面动力学粗糙度、大气底层耗散加热效应以及海面飞沫热通量三者对台风系统的影响并不是孤立的,而是互相影响的。同时考虑以上三种效应时,模拟的台风最低中心海平面气压相对于控制试验加深了10.7 hPa,台风强度增强14%,最大海面10-m风速和最大有效波高相对于控制试验也分别增大了18%和4%;海气之间总的热通量相对于控制试验增大约10%,而海气间总潜热通量增大得更为显著(约18%)。本文还将大气-海浪耦合系统应用于200509号台风Matsa个例的模拟,并通过对耦合试验与非耦合的控制试验模拟结果的分析与对比研究了大气-海浪模式的耦合对Matsa台风的影响。结果表明:考虑了海浪状态、大气底层耗散加热以及海面飞沫对海气动量和热量通量的影响,大气-海浪模式的耦合增大了海面动力学粗糙度及海气热量和水汽通量;同非耦合的控制试验相比,耦合试验模拟的Matsa台风强度有所增强,中心气压及表面最大风速同最佳路径资料符合得更好;对于Matsa台风浪的模拟,同卫星高度计观测资料的对比也表明耦合试验模拟的有效波高同观测资料更为接近。更多还原

【Abstract】 Understanding the processes and mechanisms of air-sea momentum, heat and mass transfers is essential to the study of air-sea interaction, and has taken on community interests in the past. As ubiquitous phenomena on the sea surface, surface waves can influence air-sea momentum, heat and mass exchanges through sea-state-dependent surface roughness. Meanwhile, sea spray produced by bursting bubbles in whitecaps and wind tearing of breaking wave crests can modify transfers of momentum, heat and mass across the air-sea interface directly or indirectly. Reliable understanding and parameterizing the impacts of wave state and sea spray on air-sea momentum and heat fluxes is crucial to air-sea interaction research, and is the physical basis of the coupled atmosphere-wave model.Based on previous studies and measurements, a parameterization of sea surface areodynamic roughness, which adapts to from low-to-moderate wind conditions to extremely-high wind conditions, is given by taking wave state and sea spray effects into account. The relationship between drag coefficient and wind speed corresponding to the new proposed parameterization agrees well with the existing field and laboratory observational data. According to this relation, under low-to-moderate wind conditions when the sea spray effects can be neglected, the nondimensional areodynamic roughness first increases and then decreases as the wave age increases. While under high wind conditions the drag coefficient decreases with increasing wind speed because of the modification of logarithmic wind profile by spray droplets. In addition, drag coefficients corresponding to different wave states reach their maximum value when the wind speed is between 25 to 33 m s-1.Parameterization of sea surface scalar roughness under low-to-moderate wind is reviewed, and dissipative heating and sea spray effects on air-sea heat flux are discussed in this paper. Taking into account the effect of wave state on whitecap coverage, a sea spray generation function (SSGF) for bubble-derived droplets is presented. Combined it with the wave-state-dependent SSGF for spume droplets (Zhao et al., 2006), a SSGF applicable to both bubble-derived and spume droplets with wave state effects included is obtained. Applying this SSGF to Andreas (1992)’s method for estimating sea spray heat flux and considering the thermodynamical feedback of sea spray, an algorithm to estimate wave state affected sea spray heat flux is accomplished. Given the atmospheric and oceanic environment, sea spray heat flux estimated by this algorithm increases with wind speed, wave age and windsea Reynolds number as well. Based on the discussion of air-sea momentum and heat fluxes, the next generation Weather Research and Forecasting (WRF) model is coupled with the third generation wave model WAVEWATCH III to establish a coupled atmosphere-wave system. In order to investigate the impacts of different sea-state-dependent roughness, dissipative heating and sea spray heat flux on typhoon system, the coupled model is applied to an idealized typhoon. It is found that sea-state-dependent roughness increases sea surface friction, reduces typhoon intensity and surface wave height. Whereas the impacts of different sea-state-dependent areodynamic roughness parameterizations on air-sea heat flux and typhoon track are insignificant. When using the new presented wave state and sea spray affected areodynamic roughness parameterization, the minimum central pressure for the coupled simulation is reduced by about 5% relative to the uncoupled simulation, and the simulated maximum significant wave height is also reduced by about 6%. The inclusion of dissipative heating increases the air-sea heat flux, thus intensifies the typhoon system, leading to an 8-10% increase of minimum central pressure, a 6-10% increase of maximum wind speed at 10-m height and a 10-15% increase of maximum significant wave height. Incorporating sea spray heat flux substantially strengthens the typhoon system, and increases surface wind and wave height. It also influences air-sea heat fluxes directly, and significantly increases the air-sea latent heat and water vapor fluxes. In addition, it should be pointed out that the impacts of sea-state-dependent sea surface roughness, dissipative heating and sea spray heat flux on the typhoon system are not isolated, but dependent upon each other. With all the three effects included, the minimum central pressure in the coupled simulation is 10.7 hPa deeper than in the uncoupled simulation, corresponding to a 14% increase of the intensity of typhoon system. The simulated maximum wind speed and significant wave height increase by 18% and 4% respectively. The simulated total air-sea heat flux for the coupled simulation also increases about 10%, while the air-sea latent heat flux increases more significantly by about 18%.The coupled atmosphere-wave system is further used in the simulation of Typhoon Matsa (2005). The effects on the typhoon system of the coupling between atmosphere and wave models are investigated through the analyses and comparisons of the results of the coupled and control simulations. It is shown that, considering the impacts of sea state, dissipative heating and sea spray heat flux, the coupled experiment simulates a stronger typhoon whose central pressure and maximum sustained wind agree better with the data in the best track from RSMC. In addition, comparison with the observed significant wave heights of Jason-1 altimeter indicates that the significant wave heights simulated by the coupled experiment are better consistent with the observations along the satellite tracks.更多还原