【作者】 薛宇欢；

【导师】 高会旺；

【作者基本信息】 中国海洋大学 ， 流体力学， 2009， 硕士

【摘要】 大气边界层又称为行星边界层,通常指从地面到高度约为1~1.5千米之间的大气层,以海洋为下垫面的大气边界层即为海洋大气边界层。边界层大气湍流运动方面的研究表明,湍流属性的输送过程对于边界层以及更高层次大气中的动量、热量、水汽等物理量的输送和平衡都有着重要的作用。海洋大气边界是海洋—大气能量和物质交换的桥梁。进入20世纪以来,人们越来越意识到海洋对于人类的重要性,而且也认识到海洋与大气运动有着密切的联系。海气之间湍流通量的观测在全球气候变化研究中有着十分重要的意义。本文尝试性的利用船体运动姿态监测系统辅助涡动相关系统的观测,使其精确记录涡动相关系统相对于地球坐标系下的移动速度和系统对于自自身重心的旋转、俯仰、摇摆的偏离角度,并根据Edson(1998)提出的船体运动修正公式计算出真实的三维风速。通过这一方法,初步解决了船体晃动对实际观测的影响。利用2005年渤海夏季的观测数据,分析了不同典型天气条件下的湍流特征结构和海气通量,以及风速、温度对湍流强度和海气通量的影响。研究表明:①渤海夏季在晴天时,海气边界层湍流不稳定层结时,风速分量的归一化谱在惯性副区中仍遵循-2/3指数率,但是在稳定度参数参数ξ接近于0,即近似中性层结时,风速分量的归一化谱在惯性副区中的不符合-2/3指数率。在雾天时,风速分量的归一化谱在惯性副区中也仍遵循-2/3指数率。在晴天时,湍流近似满足各向同性条件;在雾天时,湍流很好地满足各向同性的条件,在雾天条件下的空气湍流相比晴天条件下具有更显著的各向同性的性质。②在晴天时,随着稳定度的增加,湍流强度也随之增加,湍流强度与水平风速有显著的负相关关系。在雾天时,随着稳定度的增加,湍流强度降低;风速对湍流强度影响不明显。台风过程时,随着稳定度的增加,湍流强度也增加,湍流强度与水平风速有显著的正相关关系。在中性层结条件下,湍流强度均为Iu>Iv>Iw,但是在台风时的Iv与Iw已经十分接近。Iw在晴天时最大,而Iu和Iv在台风时最大,湍流总强度从大到小依次为台风、晴天、雾天。③在不同天气条件下,水平风速对湍流强度的影响不同。在晴天时,湍流强度与水平风速有显著的负相关关系;在雾天时,二者的相关性不明显;在台风过程中,二者为显著的正相关关系。中性层结条件下,湍流强度均为Iu>Iv>Iw,但是在台风时的Iv与Iw已经十分接近,在个别时段,Iv>Iu。Iw在晴天时最大,而Iu和Iv在台风时最大,湍流总强度从大到小依次为台风、晴天、雾天。④在晴天和雾天时,感热通量均与气温有显著的负相关关系。晴天条件下,感热通量日平均值为3.0W/m2;雾天条件下,感热通量日平均值为-5.9W/m2。雾天时感热由大气向海洋传输;而在晴天时,当气温变化时,感热输送方向可能改变。晴天时潜热通量与水平风速有显著的正相关关系,其日平均值为88.5W/ m2。⑤在高海况条件下使用涡动相关法进行海气边界层观测时,使用船体运动姿态监测系统对观测的三维风速进行修正是十分必要的。如不进行修正,计算出的结果往往偏大。更多还原

【Abstract】 Previous studies on turbulence in the atmosphere boundary layer showed that the transferring of turbulence properties plays significant roles in the transferring and balance of momentum, heat and water vapor. Since the 20 century, people have realized the importance of ocean, and also known the close relationship between ocean and atmosphere. Atmospheric-oceanic boundary is the bridge of energy and matter exchange between air and sea. The observation of turbulent flux between air and sea is much important in the study of global climatic variation.In this study, we tried to observe the air-sea momentum, heat and CO2 fluxes in the summer over Bohai Sea by eddy correlation system with help of ship movement and gesture monitoring system. The ship movement and gesture monitoring system could record the speed of eddy correlation system relative to earth coordinate, and also the rotating, rocking and rolling angles in high precision. Moreover, we calculated the real 3-D wind speed according to boat movement modified equation proposed by Edson (1998). By this observation and data process, we studied the basic effects of ship shaking on air-sea flux observation.Based on the observation data from summer cruise over the Bohai Sea in 2005, we analyzed turbulence structure and air-sea fluxes in different weather conditions. Moreover, the influences of wind speed and air temperature on turbulence intensity and air-sea flux are also investigated. Conclusions are listed as follows.1. In clear sky condition, when air-sea boundary layer is in unsteady stratification, the normalized spectrum of wind speed complies with -2/3 exponential rule in the inertial subarea, but when the stabilization parameterξis close to 0, i.e. the neutral stratification, the normalized spectrum of wind speed doesn’t comply with this classic rule in the inertial subarea. In foggy condition, the spectrum still abides by the rule in this subarea. Additionally, turbulence meets the isotropic condition approximately in clear sky, and it entirely meets the isotropic condition in foggy sky. 2. In clear sky condition, turbulent intensity increases with increases of the stabilization, which indicates the particularity of turbulent intensity. In foggy condition, turbulent intensity decreased with increases of the stabilization, and the wind speed has no clear effect on the turbulent intensity. In a typhoon process, turbulent intensity increases with the increases of the stabilization, and they have significant positive correlation.3. The influences of wind speed on turbulent intensity are different in different sky conditions. If it is in the neutral stratification, turbulent intensities are Iu>Iv>Iw, but in the typhoon, Iv is usually close to Iw, and in some times, Iv>Iu. Iw reaches the maximum in the clear condition, but Iu and Iv get the maximum in the typhoon process. The total turbulent intensity in typhoon is the strongest, and then the clear sky condition and the weakest is in the foggy condition.4. Both in clear and foggy conditions, sensible and latent heat flux have negative correlations to the air temperature. In clear sky, the daily mean of sensible heat flux is 3.0 W/m~2. In foggy condition, it is -5.9 W/m~2, and transferred from atmosphere to ocean. However in the clear condition, transfer direction of sensible heat may alter due to the variation of air temperature. Latent heat flux has significantly positive correlation with wind speed in the clear sky, and the daily mean value is 88.5 W/m2.5. In clear sky, the mean wind speed is 8.2 m/s; mean momentum flux is 0.138 N/m~2s. In foggy sky, wind speed is 6.1 m/s; momentum flux is 0.03 N/m~2s. In typhoon process, wind speed is 12.0 m/s, momentum flux is 0.30 N/m~2s. We could sum up that the wind speed is key factor of the momentum flux.6. In worse sea environment, it is necessary to revise the 3-D wind speed by ship movement and gesture monitoring system when we use eddy correlation to observe the air-sea boundary layer. If it is not revised, the calculation result will deviate a lot from the real condition.更多还原