The shelf-edge frontal structure in the central East China Sea and its impact on low-frequency acoustic propagation

CORC > 南海海洋研究所 > 中国科学院南海海洋研究所 > 热带海洋环境国家重点实验室(LTO)

	The shelf-edge frontal structure in the central East China Sea and its impact on low-frequency acoustic propagation
	Ramp, SR ; Chiu, CS ; Bahr, FL ; Qi, YQ ; Dahl, PH ; Miller, J ; Lynch, JF ; Zhang, RH ; Zhou, JX
	2004
关键词	environmental acoustics internal waves Kuroshio current shelf circulation
卷号	29
期号	4
页码	1011-1031
中文摘要	Two field programs, both parts of the Asian Seas International Acoustics Experiment (ASIAEX), were carried out in the central East China Sea (28degrees to 30degreesN, 126degrees 30' to 128degreesE) during April 2000 and June 2001. The goal of these programs was to study the interactions between the shelf edge environment and acoustic propagation at a wide range of frequencies and spatial scales. The low-frequency across-slope propagation was studied using a synthesis of data collected during both years including conductivity-temperature-depth (CTD) and mooring data from 2000, and XBT, thermistor chain, and wide-band source data front 2001. The water column variability during both years was dominated by the Kuroshio Current flowing from southwest to northeast over the continental slope. The barotropic tide was a mixed diurnal/semidiurnal tide with moderate amplitude compared to other parts of the Yellow and East China Sea. A large amplitude semidiurnal internal tide was also a prominent feature of the data during both years. Bursts of high-frequency internal waves were often observed, but these took the form of internal solitons only once, when a rapid off-shelf excursion of the Kuroshio coincided with the ebbing tide. Two case studies in the acoustic transmission loss (TL) over the continental shelf and slope were performed. First, anchor station data obtained during 2000 were used to study how a Kuroshio warm filament on the shelf induced variance in the transmission loss (TL) along the seafloor in the NW quadrant of the study region. The corresponding modeled single-frequency TL structure explained the significant fine-scale variability in time primarily by the changes in the multi path/multimode interference pattern. The interference was quite sensitive to small changes in the phase differences between individual paths/modes induced by the evolution of the warm filament. Second, the across-slope sound speed sections from 2001 were used to explain the observed phenomenon of abrupt signal attenuation as the transmission range lengthened seaward across the continental shelf and slope. This abrupt signal degradation was caused by the Kuroshio frontal gradients that produced an increasingly downward-refracting sound-speed field seaward from the shelf break. This abrupt signal dropout was explained using normal mode theory and was predictable and source depth dependent. For a source located above the turning depth of the highest-order shelf-trapped mode. none of the propagating modes on the shelf were excited, causing total signal extinction on the shelf.
收录类别	SCI
会议网址	IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
会议录	IEEE JOURNAL OF OCEANIC ENGINEERING
学科主题	Engineering, Civil; Engineering, Ocean; Engineering, Electrical & Electronic; Oceanography
ISSN号	0364-9059
WOS记录号	WOS:000226732700011
内容类型	会议论文
源URL	[http://ir.scsio.ac.cn/handle/344004/5591]
专题	南海海洋研究所_热带海洋环境国家重点实验室(LTO)
推荐引用方式 GB/T 7714	Ramp, SR,Chiu, CS,Bahr, FL,et al. The shelf-edge frontal structure in the central East China Sea and its impact on low-frequency acoustic propagation[C]. 见:.IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC.