Daji Huang | Second Institute of Oceanography,SOA (original) (raw)
Papers by Daji Huang
Acta Oceanologica Sinica -English Edition-
Journal of Marine Systems, 2015
Water exchange between Sanggou Bay and the Yellow Sea in China was estimated based on current pro... more Water exchange between Sanggou Bay and the Yellow Sea in China was estimated based on current profiles measured by four bottom-mounted Acoustic Doppler Current Profilers at the entrance of the bay during the kelp seeding and kelp harvesting periods. Hydrodynamics in the bay were dominated by tidal currents, especially semi-diurnal constituents. The effect of suspended kelp culture on the water exchange was investigated in terms of the tidal flux and tidal prism of the bay during a semi-diurnal period. Suspended kelp culture was found to significantly affect water exchange by changing the spatial pattern of the tidal flux but not the tidal prism. The inward tidal flux was reduced by 10% to 70% in the upper layers in the kelp seeding to kelp harvesting periods. Meanwhile, the inward tidal flux was increased by 10% to 140% in the lower layers. The mean inward tidal prism was 2.31 × 10 8 m 3 and 2.17 × 10 8 m 3 during the kelp seeding period and kelp harvesting period, respectively. Comparing with previous numerical simulations, our results did not show a prominent reduction in total water exchange across the entrance of the bay by suspended kelp culture.
Journal of Marine Systems, 2015
Journal of Marine Systems, 2014
Hypoxia off the Changjiang Estuary has been frequently reported using short time duration field d... more Hypoxia off the Changjiang Estuary has been frequently reported using short time duration field data. However, its evolution was unknown because of a lack of long-term data and its associated dominant factor. A 104-day long dataset was collected with a bottom mounted system off the Changjiang Estuary in summer 2009. The monitored parameters were bottom dissolved oxygen (DO), temperature, pressure and current. Two hypoxia events were identified, showing that hypoxia was severe and lasted for more than a half month. The first event appeared on July 18 and lasted 17 days. During this hypoxia period, the minimum DO was down to 0.17 mg/L, which broke the historical record. The second hypoxia event appeared on August 30 and lasted 18 days with a minimum DO of 1.29 mg/L. The variation of bottom DO was closely related to that of stratification. The monitored data showed that almost every increase/decrease of DO was associated with a weakening/enhancing of stratification, which were recorded as many as 12 times during the monitoring period. Wind mixing modulated or broke the stratification, which affected the variation of bottom DO and hypoxia events. Using a lagged correlation analysis, the stratification and wind mixing were significantly correlated with a coefficient of determination r 2 = 0.72, and stratification lagged wind by 35 h. The bottom DO and wind mixing were significantly correlated with a coefficient of determination r 2 = 0.65, and DO lagged wind by 33 h. The formation periods of two hypoxia events estimated from monitored data were 20 and 15 days, which were much shorter than that from on-board experiments. Strong wind mixing played a dual role on hypoxia. It could relieve hypoxia conditions by supplying DO through mixing. It accelerated the formation of hypoxia afterward as a result of the enhanced phytoplankton bloom induced by wind mixing and high organic decomposition rates consuming more DO.
Deep Sea Research Part II: Topical Studies in Oceanography, 2015
An array of four bottom-mounted acoustic Doppler current profilers (ADCPs) were deployed during t... more An array of four bottom-mounted acoustic Doppler current profilers (ADCPs) were deployed during the winter of 2008 (28 December 2008 to 12 March 2009) along a cross-shelf section in the western East China Sea to investigate the winter circulation and its response to wind. During the observation period, the observed subtidal currents exhibit coherent spatial structure and temporal variation in terms of their mean (seasonal), trend (intra-seasonal), and synoptic variability. The subtidal currents are polarized roughly in the alongshore direction parallel to local isobaths, and the weak cross-shore current is closely linked to the alongshore component. The temporal variation of the currents follows the rhythm of wind stress, sea level, and sea level difference at the synoptic scale.
Journal of Marine Systems, 2015
The tidal residual current may play an important role in the mean flow in the Changjiang Bank reg... more The tidal residual current may play an important role in the mean flow in the Changjiang Bank region, in addition to other residual currents, such as the Taiwan Warm Current, the Yellow Sea Coastal Current, and the Yellow Sea Warm Current. In this paper, a detailed structure of the tidal residual current, in particular the meso-scale eddies, in the Changjiang Bank region is observed from model simulations, and its role in the mean flow is quantified using the well-validated Finite Volume Coastal Ocean Model. The tidal residual current in the Changjiang Bank region consists of two components: an anticyclonic regional-scale tidal residual circulation around the edge of the Changjiang Bank and some cyclonic meso-scale tidal residual eddies across the Changjiang Bank. The meso-scale tidal residual eddies occur across the Changjiang Bank and contribute to the regional-scale tidal residual circulation offshore at the northwest boundary and on the northeast edge of the Changjiang Bank, southeastward along the 50 m isobath. Tidal rectification is the major mechanism causing the tidal residual current to flow along the isobaths. Both components of the tidal residual current have significant effects on the mean flow. A comparison between the tidal residual current and the mean flow indicates that the contribution of the tidal residual current to the mean flow is greater than 50%.
摘要 用 2008 年冬季在东海西南部的 4 个 ADCP 测流阵列数据, 分析了冬季浙闽沿岸流和 台湾暖流在浙江南部近海的时空特征. 滤除潮流和周期短于 1 d 的高频波动后得到余流, 余流 ... more 摘要 用 2008 年冬季在东海西南部的 4 个 ADCP 测流阵列数据, 分析了冬季浙闽沿岸流和 台湾暖流在浙江南部近海的时空特征. 滤除潮流和周期短于 1 d 的高频波动后得到余流, 余流 沿着岸线方向流动, 主轴方向大致与等深线平行. 浙闽沿岸流靠近岸, 主要分布在 50 m 等深线 的向岸一侧, 向西南流动, 最大平均流速为 0.24 m s 1 , 随着接近海面其范围向离岸方向扩展, 在表层可以扩展到 60 m 等深线附近. 台湾暖流则主要分布在 50 m 等深线的向外海一侧, 向东 北方向流动, 平均流速小于 0.09 m s 1 , 随着接近海底其范围向岸靠近, 在底层影响可达 30 m 等 深线附近; 台湾暖流在 70 m 等深线附近出现分叉, 一支继续向东北, 另一支转向东. 浙闽沿岸 流和台湾暖流主要是正压流, 平均的正压涡动动能占总涡动动能的 84.3%; 台湾暖流的时间平 均和时间变化部分都有较显著的垂向变化流, 而浙闽沿岸流的垂向变化流主要在时间平均部 分. 沿岸方向的余流用经验正交分解方法分析得到的第一模态解释总方差的 80%, 第一模态空 间分量其位相在断面上呈步调一致的分布, 其振幅在离岸 70 km 处最大, 第一模态的时间分量 主要是周期为 1.5, 2~4 和 15 d 左右的波动成分; 第二模态解释总方差的 8%, 其空间分量在断面 上呈两个位相东西相反、 振幅相当的中心, 第二模态的时间分量主要是周期为 1.2 和 5 d 左右的 波动成分. 观测期间平均风是北风, 平均风应力方向向南; 浙闽沿岸流和台湾暖流沿岸方向分 量的第一模态与风应力的时间变化有很好的相关性, 交叉谱分析显示, 沿岸方向余流与风应力 在周期为 1.5 和 2~5 d 的波动成分上信号最强且相关性最显著, 浙闽沿岸流和台湾暖流的变化滞 后于风场变化约 13 h. 关键词 风生环流 浙闽沿岸流 台湾暖流 浙江近海 浙闽沿岸流和台湾暖流是东海陆架环流的重要 组成部分, 它们与浙江近海的水文状况、渔业资源和 气候变化等有密切的联系. 已有的水文分析和短期 的测流结果表明台湾暖流在东海西部陆架终年存在, 沿 50~100 m 等深线向北流动 [1] . 台湾暖流在近底层 具有显著的爬坡和向岸移动的趋势, 其位置在冬季
A kind of trawl-resistant bottom mounts (TRBMs) is introduced about its design, construction and ... more A kind of trawl-resistant bottom mounts (TRBMs) is introduced about its design, construction and application in coastal areas. This platform balances the safety and versatile observation in design. It was accomplished by developing the technologies of floating body machining, instruments layout, system integration, deployment and reclaim. It can be deployed two months long in coastal areas shallower than 150 meters to monitor multi-disciplinary parameters by mounting with instruments, which including one ADCP, one CTD, one nitrate sensor, two acoustic releases and one battery pack. This TRBM has been deployed 20 times in East China sea, and was often used to acquire the multi-disciplinary parameters data relative to bottom hypoxia off Changjiang estuary. The applications in summer of 2009 and 2011 off northern Changjiang estuary shows that the TRBM worked well in heavily trawl-fished and typhoon condition.
In spring 2013, 33 repeat shipboard Acoustic Doppler Current Profile (ADCP) surveys were conducte... more In spring 2013, 33 repeat shipboard Acoustic Doppler Current Profile (ADCP) surveys were conducted to measure the tidal current in the Qiongzhou Strait (QS). The major tidal currents and the residual current along a section across the QS were estimated using a modified tidal harmonic analysis method based on the inverse technique. A simple simulation and comparisons with previous observations demonstrated that the tidal currents estimated using the modified tidal harmonic analysis method are reasonable, and this method was able to control the magnitude and deviation of the estimation error. The direction of the major axis of tidal current ellipses is generally along the strait. Diurnal tidal constituents are dominant among the five tidal current constituents (K 1 , O 1 , M 2 , S 2 , and MSf). The ratio of the amplitudes of O 1 , K 1 , M 2 , S 2 , and MSf, averaged along the section across the QS is 1:0.79:0.42:0.27:0.29. The residual current along the entire section is all westward; the averaged velocity over the section is 6.062.1 cm s 21 ; the associated volume transport through the section is 20.065 6 0.046 Sv (Sv 5 10 6 3 m 3 s 21 ), in which the second value denotes the uncertainty of first value. Dynamic analysis indicates that tidal current activity is more dominant than mean current and eddy activity, and tidal rectification and sea level difference between two entrances of the QS are important in maintaining the residual current through the strait.
Deep Sea Research Part II: Topical Studies in Oceanography, 2015
Journal of Geophysical Research: Oceans, 2015
A high-resolution, 3-dimensional primitive equation model is used to investigate the crossshelf e... more A high-resolution, 3-dimensional primitive equation model is used to investigate the crossshelf exchange in the East China Sea (ECS). Favorable comparisons between field data and model simulations from both climatological run and hindcast run for 2006 indicate that the model has essential skills in capturing the key physics of the ECS. Temporal and spatial variations of the cross-shelf exchanges are further analyzed. It was demonstrated from both observations and simulations that in 2006 high saline water could be delivered to the north of the Changjiang River mouth (near 32 N) as a result of stronger than typical cross-shelf exchanges at the shelf break and flows through the Taiwan Strait with an annual mean rate of 2.59 and 1.83 Sv, respectively. A few new places at the shelf break were also identified where persistent and vigorous onshore or offshore exchanges occur throughout the year. Cross-shelf exchange is largely determined by the along-shelf geostrophic balance with weak seasonality, which is modulated in upper layers by northeasterly monsoon from early-fall to late-spring and at seabed by bottom friction during December-January, May, and August-September. Nonlinear effect, with strong spatial variations and intraseasonal variability, is a secondary but persistent contributor to the net seaward transport, except for northeast of Taiwan where the nonlinear effect becomes significant but more varied.
Science China Earth Sciences, 2010
Inverse calculations using data from 16 repeat hydrographic transects collected from April 2003 t... more Inverse calculations using data from 16 repeat hydrographic transects collected from April 2003 to June 2007 have yielded velocity structures and volume transports (VTs) of the Ryukyu Current in the region east of the northern Ryukyu Islands. The inverse calculation results show that the Ryukyu Current is dominated by a subsurface velocity core with maximum velocities from 15.1 to 80.0 cm/s, whose positions vary between 110 and 600 dbar and 27.2°-28.2°N along the transect. The mean velocity exhibits a subsurface velocity core with a maximum value of 24.6 cm/s at 326 dbar depth, a VT of 14.0 Sv (1 Sv 10 ≡ 6 m 3 /s), a vertical dimension of 800 m, and a horizontal dimension of 60 km. The seasonal mean velocities show that the Ryukyu Current is stronger in autumn than in other seasons. It is suggested that this seasonal variation is coincident with the intensification of the anticyclonic eddy south of Shikoku, Japan.
Science in China Series D: Earth Sciences, 2008
In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy ... more In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy were observed from combined measurements of hydrocasts, an upward-looking moored acoustic Doppler current profiler (MADCP), pressure-recording inverted echo sounders (PIESs), satellite altimetry, and a coastal tide gauge. The hydrographic data showed that the lowest/highest temperature (T) and salinity (S) anomalies from a 13-year mean for the same season were respectively −3.0/+2.5℃ and −0.20/+0.15 psu at 380/500 dbar for the cyclonic/anticyclonic eddies. From the PIES data, using a gravest empirical mode method, we estimated time-varying surface dynamic height (D) anomaly referred to 2000 dbar changing from −20 to 30 cm, and time-varying T and S anomalies at 500 dbar ranging through about ±2 and ℃ ±0.2 psu, respectively. The passage of the eddies caused variations of both satellite-measured sea surface height anomaly (SSHA) and tide-gauge-measured sea level anomaly to change from about -20 to 30 cm, consistent with the D anomaly from the PIESs. Bottom pressure sensors measured no variation related to these eddy activities, which indicated that the two eddies were dominated by baroclinicity. Time series of SSHA map confirmed that the two eddies, originating from the North Pacific Subtropical Countercurrent region near 20°-30°N and 150°-160°E, traveled about 3000 km for about 18 months with mean westward propagation speed of about 6 cm/s, before arriving at the region southeast of Okinawa Island.
Science in China Series D, 2002
Journal of Oceanography, 2013
The temporal and spatial variability of the Kuroshio Current was analyzed. Current data were esti... more The temporal and spatial variability of the Kuroshio Current was analyzed. Current data were estimated from hydrographic data collected from areas within the central East China Sea (PN section) from 1955 to 2010 and the Tokara Strait (TK section) from 1987 to 2010. To reduce the bias caused by cruise-dependent spatial resolution among the data, grid-consistent temperature and salinity fields were reconstructed by use of a regression relationship to account for anomalies between observed stations and grid points. The mass imbalance problem between the PN and TK sections, which appears stochastically when viewed by use of the dynamic method, was solved by use of the inverse method. The estimated Kuroshio volume transport (KVT) was found to be closely consistent with that of current observations and had an uncertainty of 2.4 Sv. The KVT seemed to have neither a regime shift in approximately 1976 nor a sharply increasing trend. The KVT was dominated by 2-5 year modulating interannual variability with an amplitude of 2.8 Sv, followed by weak 20-year decadal variability with an amplitude of 0.33 Sv. Empirical orthogonal function analysis of the currents suggested that the temporal and spatial variability of the Kuroshio Current in the PN section was dominated by a transport mode, manifested by the high variability of current on the seaward side of current core with expansion or shrinkage of the core. In contrast, the temporal and spatial variability of the Kuroshio Current in the TK section was dominated by a meandering mode, as indicated by the migration of the Kuroshio axis in the south gap of the Tokara Strait.
Acta Oceanologica Sinica -English Edition-
Journal of Marine Systems, 2015
Water exchange between Sanggou Bay and the Yellow Sea in China was estimated based on current pro... more Water exchange between Sanggou Bay and the Yellow Sea in China was estimated based on current profiles measured by four bottom-mounted Acoustic Doppler Current Profilers at the entrance of the bay during the kelp seeding and kelp harvesting periods. Hydrodynamics in the bay were dominated by tidal currents, especially semi-diurnal constituents. The effect of suspended kelp culture on the water exchange was investigated in terms of the tidal flux and tidal prism of the bay during a semi-diurnal period. Suspended kelp culture was found to significantly affect water exchange by changing the spatial pattern of the tidal flux but not the tidal prism. The inward tidal flux was reduced by 10% to 70% in the upper layers in the kelp seeding to kelp harvesting periods. Meanwhile, the inward tidal flux was increased by 10% to 140% in the lower layers. The mean inward tidal prism was 2.31 × 10 8 m 3 and 2.17 × 10 8 m 3 during the kelp seeding period and kelp harvesting period, respectively. Comparing with previous numerical simulations, our results did not show a prominent reduction in total water exchange across the entrance of the bay by suspended kelp culture.
Journal of Marine Systems, 2015
Journal of Marine Systems, 2014
Hypoxia off the Changjiang Estuary has been frequently reported using short time duration field d... more Hypoxia off the Changjiang Estuary has been frequently reported using short time duration field data. However, its evolution was unknown because of a lack of long-term data and its associated dominant factor. A 104-day long dataset was collected with a bottom mounted system off the Changjiang Estuary in summer 2009. The monitored parameters were bottom dissolved oxygen (DO), temperature, pressure and current. Two hypoxia events were identified, showing that hypoxia was severe and lasted for more than a half month. The first event appeared on July 18 and lasted 17 days. During this hypoxia period, the minimum DO was down to 0.17 mg/L, which broke the historical record. The second hypoxia event appeared on August 30 and lasted 18 days with a minimum DO of 1.29 mg/L. The variation of bottom DO was closely related to that of stratification. The monitored data showed that almost every increase/decrease of DO was associated with a weakening/enhancing of stratification, which were recorded as many as 12 times during the monitoring period. Wind mixing modulated or broke the stratification, which affected the variation of bottom DO and hypoxia events. Using a lagged correlation analysis, the stratification and wind mixing were significantly correlated with a coefficient of determination r 2 = 0.72, and stratification lagged wind by 35 h. The bottom DO and wind mixing were significantly correlated with a coefficient of determination r 2 = 0.65, and DO lagged wind by 33 h. The formation periods of two hypoxia events estimated from monitored data were 20 and 15 days, which were much shorter than that from on-board experiments. Strong wind mixing played a dual role on hypoxia. It could relieve hypoxia conditions by supplying DO through mixing. It accelerated the formation of hypoxia afterward as a result of the enhanced phytoplankton bloom induced by wind mixing and high organic decomposition rates consuming more DO.
Deep Sea Research Part II: Topical Studies in Oceanography, 2015
An array of four bottom-mounted acoustic Doppler current profilers (ADCPs) were deployed during t... more An array of four bottom-mounted acoustic Doppler current profilers (ADCPs) were deployed during the winter of 2008 (28 December 2008 to 12 March 2009) along a cross-shelf section in the western East China Sea to investigate the winter circulation and its response to wind. During the observation period, the observed subtidal currents exhibit coherent spatial structure and temporal variation in terms of their mean (seasonal), trend (intra-seasonal), and synoptic variability. The subtidal currents are polarized roughly in the alongshore direction parallel to local isobaths, and the weak cross-shore current is closely linked to the alongshore component. The temporal variation of the currents follows the rhythm of wind stress, sea level, and sea level difference at the synoptic scale.
Journal of Marine Systems, 2015
The tidal residual current may play an important role in the mean flow in the Changjiang Bank reg... more The tidal residual current may play an important role in the mean flow in the Changjiang Bank region, in addition to other residual currents, such as the Taiwan Warm Current, the Yellow Sea Coastal Current, and the Yellow Sea Warm Current. In this paper, a detailed structure of the tidal residual current, in particular the meso-scale eddies, in the Changjiang Bank region is observed from model simulations, and its role in the mean flow is quantified using the well-validated Finite Volume Coastal Ocean Model. The tidal residual current in the Changjiang Bank region consists of two components: an anticyclonic regional-scale tidal residual circulation around the edge of the Changjiang Bank and some cyclonic meso-scale tidal residual eddies across the Changjiang Bank. The meso-scale tidal residual eddies occur across the Changjiang Bank and contribute to the regional-scale tidal residual circulation offshore at the northwest boundary and on the northeast edge of the Changjiang Bank, southeastward along the 50 m isobath. Tidal rectification is the major mechanism causing the tidal residual current to flow along the isobaths. Both components of the tidal residual current have significant effects on the mean flow. A comparison between the tidal residual current and the mean flow indicates that the contribution of the tidal residual current to the mean flow is greater than 50%.
摘要 用 2008 年冬季在东海西南部的 4 个 ADCP 测流阵列数据, 分析了冬季浙闽沿岸流和 台湾暖流在浙江南部近海的时空特征. 滤除潮流和周期短于 1 d 的高频波动后得到余流, 余流 ... more 摘要 用 2008 年冬季在东海西南部的 4 个 ADCP 测流阵列数据, 分析了冬季浙闽沿岸流和 台湾暖流在浙江南部近海的时空特征. 滤除潮流和周期短于 1 d 的高频波动后得到余流, 余流 沿着岸线方向流动, 主轴方向大致与等深线平行. 浙闽沿岸流靠近岸, 主要分布在 50 m 等深线 的向岸一侧, 向西南流动, 最大平均流速为 0.24 m s 1 , 随着接近海面其范围向离岸方向扩展, 在表层可以扩展到 60 m 等深线附近. 台湾暖流则主要分布在 50 m 等深线的向外海一侧, 向东 北方向流动, 平均流速小于 0.09 m s 1 , 随着接近海底其范围向岸靠近, 在底层影响可达 30 m 等 深线附近; 台湾暖流在 70 m 等深线附近出现分叉, 一支继续向东北, 另一支转向东. 浙闽沿岸 流和台湾暖流主要是正压流, 平均的正压涡动动能占总涡动动能的 84.3%; 台湾暖流的时间平 均和时间变化部分都有较显著的垂向变化流, 而浙闽沿岸流的垂向变化流主要在时间平均部 分. 沿岸方向的余流用经验正交分解方法分析得到的第一模态解释总方差的 80%, 第一模态空 间分量其位相在断面上呈步调一致的分布, 其振幅在离岸 70 km 处最大, 第一模态的时间分量 主要是周期为 1.5, 2~4 和 15 d 左右的波动成分; 第二模态解释总方差的 8%, 其空间分量在断面 上呈两个位相东西相反、 振幅相当的中心, 第二模态的时间分量主要是周期为 1.2 和 5 d 左右的 波动成分. 观测期间平均风是北风, 平均风应力方向向南; 浙闽沿岸流和台湾暖流沿岸方向分 量的第一模态与风应力的时间变化有很好的相关性, 交叉谱分析显示, 沿岸方向余流与风应力 在周期为 1.5 和 2~5 d 的波动成分上信号最强且相关性最显著, 浙闽沿岸流和台湾暖流的变化滞 后于风场变化约 13 h. 关键词 风生环流 浙闽沿岸流 台湾暖流 浙江近海 浙闽沿岸流和台湾暖流是东海陆架环流的重要 组成部分, 它们与浙江近海的水文状况、渔业资源和 气候变化等有密切的联系. 已有的水文分析和短期 的测流结果表明台湾暖流在东海西部陆架终年存在, 沿 50~100 m 等深线向北流动 [1] . 台湾暖流在近底层 具有显著的爬坡和向岸移动的趋势, 其位置在冬季
A kind of trawl-resistant bottom mounts (TRBMs) is introduced about its design, construction and ... more A kind of trawl-resistant bottom mounts (TRBMs) is introduced about its design, construction and application in coastal areas. This platform balances the safety and versatile observation in design. It was accomplished by developing the technologies of floating body machining, instruments layout, system integration, deployment and reclaim. It can be deployed two months long in coastal areas shallower than 150 meters to monitor multi-disciplinary parameters by mounting with instruments, which including one ADCP, one CTD, one nitrate sensor, two acoustic releases and one battery pack. This TRBM has been deployed 20 times in East China sea, and was often used to acquire the multi-disciplinary parameters data relative to bottom hypoxia off Changjiang estuary. The applications in summer of 2009 and 2011 off northern Changjiang estuary shows that the TRBM worked well in heavily trawl-fished and typhoon condition.
In spring 2013, 33 repeat shipboard Acoustic Doppler Current Profile (ADCP) surveys were conducte... more In spring 2013, 33 repeat shipboard Acoustic Doppler Current Profile (ADCP) surveys were conducted to measure the tidal current in the Qiongzhou Strait (QS). The major tidal currents and the residual current along a section across the QS were estimated using a modified tidal harmonic analysis method based on the inverse technique. A simple simulation and comparisons with previous observations demonstrated that the tidal currents estimated using the modified tidal harmonic analysis method are reasonable, and this method was able to control the magnitude and deviation of the estimation error. The direction of the major axis of tidal current ellipses is generally along the strait. Diurnal tidal constituents are dominant among the five tidal current constituents (K 1 , O 1 , M 2 , S 2 , and MSf). The ratio of the amplitudes of O 1 , K 1 , M 2 , S 2 , and MSf, averaged along the section across the QS is 1:0.79:0.42:0.27:0.29. The residual current along the entire section is all westward; the averaged velocity over the section is 6.062.1 cm s 21 ; the associated volume transport through the section is 20.065 6 0.046 Sv (Sv 5 10 6 3 m 3 s 21 ), in which the second value denotes the uncertainty of first value. Dynamic analysis indicates that tidal current activity is more dominant than mean current and eddy activity, and tidal rectification and sea level difference between two entrances of the QS are important in maintaining the residual current through the strait.
Deep Sea Research Part II: Topical Studies in Oceanography, 2015
Journal of Geophysical Research: Oceans, 2015
A high-resolution, 3-dimensional primitive equation model is used to investigate the crossshelf e... more A high-resolution, 3-dimensional primitive equation model is used to investigate the crossshelf exchange in the East China Sea (ECS). Favorable comparisons between field data and model simulations from both climatological run and hindcast run for 2006 indicate that the model has essential skills in capturing the key physics of the ECS. Temporal and spatial variations of the cross-shelf exchanges are further analyzed. It was demonstrated from both observations and simulations that in 2006 high saline water could be delivered to the north of the Changjiang River mouth (near 32 N) as a result of stronger than typical cross-shelf exchanges at the shelf break and flows through the Taiwan Strait with an annual mean rate of 2.59 and 1.83 Sv, respectively. A few new places at the shelf break were also identified where persistent and vigorous onshore or offshore exchanges occur throughout the year. Cross-shelf exchange is largely determined by the along-shelf geostrophic balance with weak seasonality, which is modulated in upper layers by northeasterly monsoon from early-fall to late-spring and at seabed by bottom friction during December-January, May, and August-September. Nonlinear effect, with strong spatial variations and intraseasonal variability, is a secondary but persistent contributor to the net seaward transport, except for northeast of Taiwan where the nonlinear effect becomes significant but more varied.
Science China Earth Sciences, 2010
Inverse calculations using data from 16 repeat hydrographic transects collected from April 2003 t... more Inverse calculations using data from 16 repeat hydrographic transects collected from April 2003 to June 2007 have yielded velocity structures and volume transports (VTs) of the Ryukyu Current in the region east of the northern Ryukyu Islands. The inverse calculation results show that the Ryukyu Current is dominated by a subsurface velocity core with maximum velocities from 15.1 to 80.0 cm/s, whose positions vary between 110 and 600 dbar and 27.2°-28.2°N along the transect. The mean velocity exhibits a subsurface velocity core with a maximum value of 24.6 cm/s at 326 dbar depth, a VT of 14.0 Sv (1 Sv 10 ≡ 6 m 3 /s), a vertical dimension of 800 m, and a horizontal dimension of 60 km. The seasonal mean velocities show that the Ryukyu Current is stronger in autumn than in other seasons. It is suggested that this seasonal variation is coincident with the intensification of the anticyclonic eddy south of Shikoku, Japan.
Science in China Series D: Earth Sciences, 2008
In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy ... more In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy were observed from combined measurements of hydrocasts, an upward-looking moored acoustic Doppler current profiler (MADCP), pressure-recording inverted echo sounders (PIESs), satellite altimetry, and a coastal tide gauge. The hydrographic data showed that the lowest/highest temperature (T) and salinity (S) anomalies from a 13-year mean for the same season were respectively −3.0/+2.5℃ and −0.20/+0.15 psu at 380/500 dbar for the cyclonic/anticyclonic eddies. From the PIES data, using a gravest empirical mode method, we estimated time-varying surface dynamic height (D) anomaly referred to 2000 dbar changing from −20 to 30 cm, and time-varying T and S anomalies at 500 dbar ranging through about ±2 and ℃ ±0.2 psu, respectively. The passage of the eddies caused variations of both satellite-measured sea surface height anomaly (SSHA) and tide-gauge-measured sea level anomaly to change from about -20 to 30 cm, consistent with the D anomaly from the PIESs. Bottom pressure sensors measured no variation related to these eddy activities, which indicated that the two eddies were dominated by baroclinicity. Time series of SSHA map confirmed that the two eddies, originating from the North Pacific Subtropical Countercurrent region near 20°-30°N and 150°-160°E, traveled about 3000 km for about 18 months with mean westward propagation speed of about 6 cm/s, before arriving at the region southeast of Okinawa Island.
Science in China Series D, 2002
Journal of Oceanography, 2013
The temporal and spatial variability of the Kuroshio Current was analyzed. Current data were esti... more The temporal and spatial variability of the Kuroshio Current was analyzed. Current data were estimated from hydrographic data collected from areas within the central East China Sea (PN section) from 1955 to 2010 and the Tokara Strait (TK section) from 1987 to 2010. To reduce the bias caused by cruise-dependent spatial resolution among the data, grid-consistent temperature and salinity fields were reconstructed by use of a regression relationship to account for anomalies between observed stations and grid points. The mass imbalance problem between the PN and TK sections, which appears stochastically when viewed by use of the dynamic method, was solved by use of the inverse method. The estimated Kuroshio volume transport (KVT) was found to be closely consistent with that of current observations and had an uncertainty of 2.4 Sv. The KVT seemed to have neither a regime shift in approximately 1976 nor a sharply increasing trend. The KVT was dominated by 2-5 year modulating interannual variability with an amplitude of 2.8 Sv, followed by weak 20-year decadal variability with an amplitude of 0.33 Sv. Empirical orthogonal function analysis of the currents suggested that the temporal and spatial variability of the Kuroshio Current in the PN section was dominated by a transport mode, manifested by the high variability of current on the seaward side of current core with expansion or shrinkage of the core. In contrast, the temporal and spatial variability of the Kuroshio Current in the TK section was dominated by a meandering mode, as indicated by the migration of the Kuroshio axis in the south gap of the Tokara Strait.