Intercomparison of one-dimensional detecting methods of unveiling the global ocean striations
Zhang Yu1; Guan Yu-Ping1; Chen Zhao-Hui1; Liu Hai-Long1; Huang Rui-Xin1;
摘要Striation in the ocean is a research frontier in physical oceanography. Interestingly, it has some "sisters and brothers" in Mother Nature, such as the Jovian belts, subtropical jet streams in the atmosphere, and zonal flows in plasma. This meso-scale oceanic phenomenon is, however, concomitant with but covered up by the macro-scale ocean currents or circulations. In order to unveil such zonal jet-like structures, a spatial filtering must be applied to the commonly available time-average data. Previous studies mostly focused on prominent features of striations, such as banded structures, and the generation mechanism; however, the differences revealed by applying different types of filtering methods have not received enough attention. In this paper we present a comprehensive study on the effectiveness of the different detection approaches to unveiling the striations. Three one-dimensional filtering methods: Gaussian smoothing, Hanning and Chebyshev high-pass filtering, are used to analyze SODA data and LICOM model outputs. The first two methods have been used in many previous studies; on the other hand, the Chebyshev filter is a newcomer for this purpose. Our results show that all three methods can reveal ocean banded structures, but the Chebyshev filtering is the best choice. The Gaussian smoothing is not a high pass filter, and it can merely bring regional striations, such as those in the Eastern Pacific, to light. The Hanning high pass filter can introduce a northward shifting of stripes, so it is not as good as the Chebyshev filter. In addition, a cutoff frequency is often needed in applying the high-pass filter, and this frequency depends on the spectrum analysis of the original data. In this paper, we discuss the filtering output and its spatial power spectra of three normalized cutoff-frequencies, 0.1, 0.3 and 0.7. When the cutoff-frequency is too low, the filtering is insufficient; on the other hand, if the cut-off frequency is too high, excessive filtering can happen. Our study shows that for analyzing the global ocean striations, the best normalized cutoff frequency domain is between 0.1 and 0.4. In addition, the bandwidth of striation for using the Chebyshev high pass filter to analyze the SODA data in a depth of 300 m is 150-300 km. In the general case, we propose to use the Chebyshev filter in lieu of Hanning or other methods for investigating ocean striations.
关键词Turbulence Ocean Striations Zonal Flows High-pass Filtering
作者单位1.[Zhang Yu] Zhejiang Ocean Univ, Marine Sci & Technol Coll, Zhoushan 316000, Peoples R China
2.[Zhang Yu
3.Guan Yu-Ping] Chinese Acad Sci, South China Sea Inst Oceanol, State Key Lab Trop Oceanog, Guangzhou 510301, Guangdong, Peoples R China
4.[Chen Zhao-Hui] Ocean Univ China, Key Lab Phys Oceanog, Qingdao 266003, Peoples R China
5.[Liu Hai-Long] Chinese Acad Sci, Inst Atmospher Phys, State Key Lab Numer Modeling Atmospher Sci & Geop, Beijing 100029, Peoples R China
6.[Huang Rui-Xin] Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA
GB/T 7714
Zhang Yu,Guan Yu-Ping,Chen Zhao-Hui,et al. Intercomparison of one-dimensional detecting methods of unveiling the global ocean striations[J]. ACTA PHYSICA SINICA,2015,64(14):149201-.
APA Zhang Yu,Guan Yu-Ping,Chen Zhao-Hui,Liu Hai-Long,Huang Rui-Xin,& of one-dimensional detecting methods of unveiling the global ocean striations.ACTA PHYSICA SINICA,64(14),149201-.
MLA Zhang Yu,et al."Intercomparison of one-dimensional detecting methods of unveiling the global ocean striations".ACTA PHYSICA SINICA 64.14(2015):149201-.
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