项目名称: 不同下垫面大气湍流相干结构特征及其对地表通量传输的贡献
项目编号: No.41275016
项目类型: 面上项目
立项/批准年度: 2013
项目学科: 天文学、地球科学
项目作者: 张宇
作者单位: 中国科学院寒区旱区环境与工程研究所
项目金额: 96万元
中文摘要: 近代湍流研究的重大进展之一是发现剪切湍流中存在相干结构,由于大尺度相干涡旋对地表-大气间的能量物质输送存在显著贡献,因此成为近年来大气湍流研究中的重要主题。对不同下垫面相干结构的研究,不仅有助于我们认识大气湍流的本质,并且对边界层参数化方案的发展与改进有着至关重要的影响。小波变换方法在湍流结构分析中的广泛应用,使相干结构特征及其对通量的贡献有了大量的研究,但由于使用方法的不一致,所得到的结果有着很大的差异,从而无法进行深入的比较。本研究拟在目前小波变换检测相干结构方案的基础上,考虑标量间非相似性,以及不同标量的传输机理,对方案进行发展;使用统一的小波变换方法,针对不同动力、水热性质下垫面观测得到的大气湍流资料进行分析处理,研究相干结构的特征,如周期、间歇时间、振动强度、发生频率、Taylor长度尺度,及其与动力、热力因子的相互关系;通过条件采样的方法,研究相干结构对通量的贡献。
中文关键词: 相干结构;小波分析;湍流特征;通量贡献;
英文摘要: One of the most impotant progress in turbulence research is the finding of coherent structures in shear flow. It has been get more and more attention in the recent years for their great contributions on the transfer of momentum, heat and matters between land and atmosphere.The study on characteristics of coherent structure and their flux contributions could help us better understanding the nature of turbulence, but also be importance on the development of subgrid-scale in numerical model. Since the widely application of wavelet transform in the turbulence time series analysis, there are many studies on the dection of coherent structures and their contributions to the fluxes. Because of the inconsistence of algorithms used among various works and the lack of long-term observation data, it became impossible of comparison research among different surface type. In this study, the improved method will be developed with consideration of dissmilarity among scalars and difference of transferring machanisms for scalars.This method will be applied on the data from observation over various surface type with different hydrothermal and dynamical conditions. The characteristics of coherent structures, i.e. temperal scale, intermitent time, ramp intensity, and Tayler length scale, and their relation with thermal and dynamic f
英文关键词: coherent structure;wavelet transform;turbulence characteristics;flux contribution;