近海边湍流谱特征分析

Characteristics of Turbulent Spectrum in the Boundary Layer by Sea

采用三维超声风速仪测量了近海边三维风速和虚温数据。谱分析表明:近海边近地层湍流基本满足局地均匀各向同性的假定。提出了一种确定谱幂率的方法一连续滑动线性回归法,对利用此法算出的风速谱谱幂率和温度谱谱幂率进行统计分析发现,风速谱谱幂率概率分布于以“-5/3”为中心的置信区间内,基本上满足Komogorov的“-5/3”定律;而温度谱幂率的概率分布则偏离“-5/3”。结合层结稳定度分析发现:在稳定层结下, 44.3%的温度谱幂率满足“-5/3”;在不稳定层结下, 16.1%的谱幂率满足“-5/3”。据此认为,大气层结状态可能是造成温度谱幂率偏离“-5/3”的主要原因。

Three-dimensional velocity components and virtual temperature were measured using ultrasonic anemometer above an area by sea. Turbulent characteristics were analyzed with the spectra theory, and the local homogeneous isotropy was satisfied. A method of calculating spectra-index named as CSLR （continuous smoothing linear regression） was put forward. With this method, velocity spectra-index and temperature spectra-index are calculated, and the velocity spectra are identical with Komogorov＇s ＂-5/3＂ law as the spectra-indices are within the believable-interval equivalently spanned ＂-5/3＂, and that the probability distri- bution of temperature spectra is apart from ＂-5/3＂. Further analysis under different layers with special status was carried out and the phenomenon was found that 44.3% of temperature spectra-index locates equivalently around ＂-5/3＂ under stable layer but only 16.1% under unstable layer. Different stability is possibly the major reason that causes the apart-from-＂-5/3＂ distribution of temperature spectra-index.