摘要
海-气通量交换过程是气候系统各层圈相互作用的主要过程之一。海洋表面能量、物质交换反映了海洋-大气之间相互作用和联系,海-气通量输送强烈地影响上层海洋结构及大气边界层结构,进而影响大气环流和海洋环流,造成不同尺度的天气及气候变化。而且海-气通量的观测研究对于模拟和理解海洋-大气系统的耦合、变化性质也十分重要,天气预报及气候模式中海洋边界层参数的不确定性极大的影响了其模拟能力。
利用涡动相关法测量边界层通量是目前最可靠的测量方法之一,但由于海上环境复杂以及一些具体条件的限制,使得其在海上进行观测的难度很大。本文利用国家海洋局2006-2007年“908专项”-ST02区块水体环境调查及2005年国家863规范化外海实验两个项目的近海层大气湍流观测资料,尝试克服在海上观测所面临的大量硬件及软件方面的困难,利用涡动相关法计算了海-气间的分析和计算了北黄海、南海北部及吕宋海峡海域及西太平洋近海面层动量通量、风速标准差、曳力系数、空气动力粗糙度,分析了部分特征量与水平平均风速(U)的关系。进而得到了一些有意义的结论:
(1)通过计算稳定度参数发现近海面层大气绝大多数时间处于不稳定、弱不稳定的状态。
(2)在东方红2号综合海洋调查船上用相同的仪器相同的观测方法及后期处理方法,计算了3个海区的动量通量值。北黄海秋、冬季、南海北部及吕宋海峡海域及西太平洋海域动量通量平均值分别为:0.079、0.081、0.107、0.070 N/m2。
(3)各海区曳力系数值对平均风速不敏感,随平均风速变化较小,在平均风速大于4m/s时,北黄海秋、冬季、南海北部及吕宋海峡海域及西太平洋海域103CD平均值分别为:1.335、1.359、1.046、1.324。
(4)近海面层大气湍流强度数值量级约为10-2,比近地面层大气湍流强度普遍低一个量级,且近海面层大气湍流强度与风速呈负相关关系。
(5)当平均风速大于4m/s时,各海区水平风速标准差与稳定度参数的关系不明显,数据较离散,北黄海秋、冬季节无量纲垂直风速标准差与稳定度参数相似性关系较好,满足Monin-Obukhov相似理论。秋季最佳拟合关系为σw/u*=1.9(-Z/L)11/3,冬季为σw/u*=2.0(-Z/L)1/3。
(6)当平均风速大于4m/s时,各海区粗糙度与平均风速均呈线性关系。北黄海秋、冬季、南海北部及吕宋海峡海域及西太平洋海域拟合关系式分别为:103Z0=0.0350U-0.1335、103Z0=0.0414U-0.1719、103Z0=0.0429U-0.2004、103Z0=0.0303U-0.1031。
The sea-air flux exchange is the main process of interaction of each climate system layer laps. The energy and material exchange between atmosphere and ocean's surface reflects ocean-atmosphere and interaction influences the up Marine structure and low atmospheric boundary layer structure, which affect the atmosphere general circulation and ocean circulation caused by different scales, then the weather and climate change. The study of the flux is also very important to understand the Marine-the coupling, changes atmospheric system. Weather and climate patterns of Marine boundary parameter uncertainty have greatly influenced the simulation capability.
Using eddy correlation method for measuring the flux boundary is the most reliable measurement method, but due to the complex environment and some specific conditions, the observation is difficulty. Use the atmospheric turbulence observation data of 908 project of ST02 during 2006-2007 and the standardization of national offshore sea experiment of 863 project in 2005,try to overcome the difficulty of observation and calculation, using eddy correlation method to calculate the momentum fluxes, drag coefficient deviations, air force, analyzes the characteristics of roughness of the north and south of north yellow sea, the sea and the west Pacific Luzon. Some significant conclusions:
(1)Through calculating stability parameters of offshore surface, it was found that atmosphere in a stable, weak instability state at most of the time
(2) Three areas' momentum fluxes are calculated, which observed in the R/V dongfanghong 2 with the same equipment of the same observation method and calculation method. The North Yellow sea in autumn and winter, north china sea and Luzon channel, the western Pacific momentum fluxes average respectively is 0.079,0.081,0.107,0.070 N/m2.
(3) The drag and bulk aerodynamic coefficients are sensitive to changes of the average wind speed, when the average wind speed smaller than 4m/s. The North Yellow sea in autumn and winter, north China sea and Luzon channel, the western Pacific momentum 103CD respectively is 1.335,1.359,1.046,1.324.
(4) Results show the magnitude of turbulence intensity that over the sea surface is 10-2, which is lower than that of the land underlying surface.
(5) The relationship between standard deviations of horizontal wind and stability parameters is not obvious. Autumn and winter data over the North Yellow sea verify that standard deviation of vertical velocity meets Monin-Obukhov similarity theory very well. The best fitting relationship in autumn and winter isσw/u*= .9(-Z/L)1/3 andσw/u*=2.0(-Z/L)1/3
(6)The sea average wind speed and the roughness are linear relationship, when the average speed more than 4m/s. The best fitting relationship of the North Yellow sea in autumn and winter, north china sea and Luzon channel, the western Pacific momentum 1 respectively is 103Z0=0.0350U-0.1335,103Z0=0.0414U-0.1719,103Z0=0.0429U-0.2004, 103Z0=0.0303U-0.1031。
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