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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.
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Keywords:
- turbulence /
- ocean striations /
- zonal flows /
- high-pass filtering
[1] Williams G P 1978 J. Atmosph. Sci. 35 1399
[2] Soomere T 1995 Phys. Rev. Lett. 75 2440
[3] Lu H L, Chen Z Y, Li Y X, Yang K 2011 Acta Phys. Sin. 60 085202 (in Chinese) [陆赫林, 陈忠勇, 李跃勋, 杨恺 2011 60 085202]
[4] Chen R, Liu A D, Shao M L, Hu G H, Jin X L 2014 Acta Phys. Sin. 63 185201 (in Chinese) [陈冉, 刘阿娣, 邵明林, 胡广海, 金晓丽 2014 63 185201]
[5] Zhang Y Z, Xie T 2014 Acta Phys. Sin. 63 035202 (in Chinese) [章扬忠, 谢涛 2014 63 035202]
[6] Shi B R 2010 Chin. Phys. B 19 095201
[7] Baldwin M P, Rhines P B, Huang H P 2007 Science 315 467
[8] Maximenko N A, Bang B, Sasaki H 2005 Geophys. Res. Lett. 32 L12607
[9] van Sebille E, Kamenkovich I, Willis J K 2005 Geophys. Res. Lett. 38 L02606
[10] Ollitrault M, Lankhorst M, Fratantoni D, Richardson P, Zenk W 2006 Geophys. Res. Lett. 33 L05605
[11] Wang J B, Spall M A, Flierl G R, Malanotte-Rizzoli P 2012 Geophys. Res. Lett. 39 L10601
[12] Maximenko N A, Melnichenko O V, Niller P P, Sasaki H 2008 Geophys. Res. Lett. 35 L08603
[13] Buckingham C E, Cornillon P C 2013 J. Geophys. Res. 118 448
[14] Cravatte S, Kessler W S, Marin F 2012 J. Phys. Oceanography 42 1475
[15] Kamenkovich I, Berloff P, Pedlosky J 2009 J. Phys. Oceanography 39 1631
[16] Huang R X 2013 J. Tropical Oceanography 32 1 (in Chinese) [黄瑞新 2013 热带海洋学报 32 1]
[17] Qiu B, Rudnick D L, Chen S M, Kashino Y J 2013 Geophys. Res. Lett. 40 2183
[18] Davis A, Lorenzo E D, Luo H, Belmadani A, Maximenko N, Melnichenko O, Schneider N 2014 Geophys. Res. Lett. 41 L057956
[19] Ivanov L M, Collins C A, Margolina T M 2012 J. Atmosph. Oceanic Technol. 29 1111
[20] Melnichenko O V, Maximenko N A, Schneider N, Sasaki H 2010 Ocean Dynamics 60 653
[21] Yu Y Q, Liu H L, Lin P F 2012 Chin. Sci. Bull. 57 3908
[22] Feng X, Liu H L, Wang F C, Yu Y Q, Yuan D L 2013 Chin. Sci. Bull. 58 3504
[23] Rhines P B 1975 J. Fluid Mech. 69 417
[24] Richards K J, Maximenko N A, Bryan F O, Sasaki H 2006 Geophys. Res. Lett. 33 L03605
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[1] Williams G P 1978 J. Atmosph. Sci. 35 1399
[2] Soomere T 1995 Phys. Rev. Lett. 75 2440
[3] Lu H L, Chen Z Y, Li Y X, Yang K 2011 Acta Phys. Sin. 60 085202 (in Chinese) [陆赫林, 陈忠勇, 李跃勋, 杨恺 2011 60 085202]
[4] Chen R, Liu A D, Shao M L, Hu G H, Jin X L 2014 Acta Phys. Sin. 63 185201 (in Chinese) [陈冉, 刘阿娣, 邵明林, 胡广海, 金晓丽 2014 63 185201]
[5] Zhang Y Z, Xie T 2014 Acta Phys. Sin. 63 035202 (in Chinese) [章扬忠, 谢涛 2014 63 035202]
[6] Shi B R 2010 Chin. Phys. B 19 095201
[7] Baldwin M P, Rhines P B, Huang H P 2007 Science 315 467
[8] Maximenko N A, Bang B, Sasaki H 2005 Geophys. Res. Lett. 32 L12607
[9] van Sebille E, Kamenkovich I, Willis J K 2005 Geophys. Res. Lett. 38 L02606
[10] Ollitrault M, Lankhorst M, Fratantoni D, Richardson P, Zenk W 2006 Geophys. Res. Lett. 33 L05605
[11] Wang J B, Spall M A, Flierl G R, Malanotte-Rizzoli P 2012 Geophys. Res. Lett. 39 L10601
[12] Maximenko N A, Melnichenko O V, Niller P P, Sasaki H 2008 Geophys. Res. Lett. 35 L08603
[13] Buckingham C E, Cornillon P C 2013 J. Geophys. Res. 118 448
[14] Cravatte S, Kessler W S, Marin F 2012 J. Phys. Oceanography 42 1475
[15] Kamenkovich I, Berloff P, Pedlosky J 2009 J. Phys. Oceanography 39 1631
[16] Huang R X 2013 J. Tropical Oceanography 32 1 (in Chinese) [黄瑞新 2013 热带海洋学报 32 1]
[17] Qiu B, Rudnick D L, Chen S M, Kashino Y J 2013 Geophys. Res. Lett. 40 2183
[18] Davis A, Lorenzo E D, Luo H, Belmadani A, Maximenko N, Melnichenko O, Schneider N 2014 Geophys. Res. Lett. 41 L057956
[19] Ivanov L M, Collins C A, Margolina T M 2012 J. Atmosph. Oceanic Technol. 29 1111
[20] Melnichenko O V, Maximenko N A, Schneider N, Sasaki H 2010 Ocean Dynamics 60 653
[21] Yu Y Q, Liu H L, Lin P F 2012 Chin. Sci. Bull. 57 3908
[22] Feng X, Liu H L, Wang F C, Yu Y Q, Yuan D L 2013 Chin. Sci. Bull. 58 3504
[23] Rhines P B 1975 J. Fluid Mech. 69 417
[24] Richards K J, Maximenko N A, Bryan F O, Sasaki H 2006 Geophys. Res. Lett. 33 L03605
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