Intraseasonal modulation of Wyrtki jet in the eastern Indian Ocean by equatorial waves during spring 2013
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Intraseasonal modulation of Wyrtki jet in the eastern Indian Ocean by equatorial waves during spring 2013 Yongliang Duan1, 2, Hongwei Liu3, 4, 5, Lin Liu1, 2*, Weidong Yu6, 7, 8 1 Center for Ocean and Climate Research, First Institute of Oceanography, Ministry of Natural Resources, Qingdao
266061, China 2 Laboratory for Regional Oceanography and Numerical Modeling, Pilot National Laboratory for Marine Science and
Technology (Qingdao), Qingdao 266061, China 3 Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao
266071, China 4 Laboratory for Ocean and Climate Dynamics, Pilot National Laboratory for Marine Science and Technology
(Qingdao), Qingdao 266071, China 5 Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China 6 School of Atmospheric Sciences, Sun Yat-Sen University, Zhuhai Campus, Zhuhai 519082, China 7 Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-Sen University), Ministry of Education, Zhuhai
519082, China 8 Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
Received 8 January 2020; accepted 4 February 2020 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
A strong spring Wyrtki jet (WJ) presents in May 2013 in the eastern equatorial Indian Ocean. The entire buildup and retreat processes of the spring WJ were well captured by two adjacent Acoustic Doppler Current Profilers mounted on the mooring systems. The observed zonal jet behaved as one intraseasonal event with the significant features of abrupt emergence as well as slow disappearance. Further research illustrate that the pronounced surface westerly wind burst during late-April to mid-May, associated with the active phase of a robust eastwardpropagating Madden–Julian oscillation in the tropical Indian Ocean, was the dominant reason for the rapid acceleration of surface WJ. In contrasting, the governing mechanism for the jet termination was equatorial wave dynamics rather than wind forcing. The decomposition analysis of equatorial waves and the corresponding changes in the ocean thermocline demonstrated that strong WJ was produced rapidly by the wind-generated oceanic downwelling equatorial Kelvin wave and was terminated subsequently by the westward-propagating equatorial Rossby wave reflecting from eastern boundaries of the Indian Ocean. Key words: Wyrtki jet, equatorial wave dynamics, Madden–Julian oscillation, tropical Indian Ocean Citation: Duan Yongliang, Liu Hongwei, Liu Lin, Yu Weidong. 2020. Intraseasonal modulation of Wyrtki jet in the eastern Indian Ocean by equatorial waves during spring 2013. Acta Oceanologica Sinica, 39(7): 11–18, doi: 10.1007/s13131-020-1576-2
1 Introduction The surface circulation of the tropical Indian Ocean (TIO) is primary modulated by the seasonal monsoon winds (Schott and McCreary, 2001; Schott et al., 2009). During monsoon transition seasons, the strong eastward surface Wyrtki jets (WJs), forced directly by the semia
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