利用连续小波提取近海大气湍流中的相干结构

Isolating the Coherent Structure in Atmospheric Turbulence over the Sea Using Continuous Wavelet Transform

利用Morlet子波对南海塔基风脉动资料进行连续小波分析,并根据能量极大值法则辨识相干结构的尺度,从而构建基于相干结构主要尺度的湍流模型。通过对小波系数进行谱分析,得到相干结构的生成周期,进而刻画相干结构的演变特征。结果表明:相干尺度提取的准周期结构在数值和波形上能够很好的反映原信号的主要结构。在分析频段内,大气湍流相干结构的生命尺度和生成周期相近,相干结构以连续出现为主,而小尺度涡旋结构的生成存在明显的不连续。最后,结合观测期间天气过程以及相应的湍流统计特征分析,给出了典型天气条件下相干结构涡动能量分布及其随时间的变化特征。

Continuous Morlet wavelet transform is used to analysis atmospheric turbulence over the South China Sea. According to the energy maxima criterion, the coherent structures can be detected and isolated from the turbulence signals. The spectral analysis of the wavelet transform coefficients gives the evolution process of the coherent structure by identifying their durations and periods. The conclusions show that the primary structure of original signal can be well reflected by the quasi-periodic structures in numeric value and waveform. In the analyzed frequency band, the periods of the coherent structures close to its durations, which means the coherent structure occur continuously. While the small-scale eddy structures occur intermittently. Finally, the weather process and the statistical characteristics of turbulence.during the observation period are analyzed, and the eddy energy distribution and transformation of the coherent structure are investigated as well.