跃温层厚度对内波破坏水体分层特性的影响

为探求人工诱导内波混合技术在实际大水深分层湖泊水库中的应用效果,采用自主研制的机械混合装置和分层水库物理模型,开展不同跃温层厚度条件下内波破坏分层的中试研究.机械混合装置出流形成水流循环,在水体分层状态下,出流动能转化为内波波能,环流减弱但依旧存在,在内波破坏水体分层过程中,变温层与等温层的水温差别逐渐减小,跃温层逐渐上移且厚度减小,直至水体分层被完全破坏.在跃温层温度梯度、水流扰动强度、水深均相同的条件下,随着跃温层厚度的增加,水体稳定系数增大,临界层内波波能损失减小,内波波幅和能流密度增加,混合效率提高,内波周期不变,波速稍有减小.实验说明内波混合水体技术应用于大水深水体中时将有更高的效率.

分层水环境曝气诱导形成内波的过程与特性

采用分层水库模型,在平均温度梯度为0.37℃/cm条件下,开展了系统的曝气诱导内波的中试研究.分析了曝气诱导形成内波的过程,探究了曝气诱导形成内波的类型,重点揭示了曝气扰动源形式和跃温层厚度对内波形成过程和特性的影响.实验结果表明:扬水曝气产生的气水两相流是一种非定常的周期性扰动源,气水两相流的尾迹带动整个模型水体上下振动,这种振动在分层水体跃温层处诱导形成内波.从激发源角度上说,它是一种尾迹效应波.气弹释放周期在44.06~58.69s之间时,内波波高达到最大,当气弹释放周期达到180s时不能形成连续的内波;曝气器出流口增大,内波波高、周期呈增大趋势.分层水体的跃温层厚度也影响内波的形成,相同温度梯度条件下,随着跃温层厚度的增加,内波的波高、周期随之增大.

池塘蓝藻的危害及处理措施

在粤西地区的南美白对虾养殖过程中,蓝藻是常见的水质调控问题,略大意,往往会影响南美白对虾的摄食,诱发细菌性等疾病的发生,造成南美白对虾大量的死亡。因此,对于蓝藻,应引起足够的重视。下面介绍蓝藻的危害与成因及应对措施。一、蓝藻危害高位池中的蓝藻爆发时,当中的微囊藻与颤藻常在水面形成一层翠绿色的水华。

Variations of SST and Thermocline Depth in the Tropical Indian Ocean During Indian Ocean Dipole Events

Interannual variations in the surface and subsurface tropical Indian Ocean were studied using HadlSST and SODA datasets. Wind and heat flux datasets were used to discuss the mechanisms for these variations. Our results indicate that the surface and subsurface variations of the tropical Indian Ocean during Indian Ocean Dipole （IOD） events are significantly different. A prominent characteristic of the eastern pole is the SSTA rebound after a cooling process, which does not take place at the subsurface layer. In the western pole, the surface anomalies last longer than the subsurface anomalies. The subsurface anomalies are strongly correlated with ENSO, while the relationship between the surface anomalies and ENSO is much weaker. And the subsurface anomalies of the two poles are negatively correlated while they are positively correlated at the surface layer. The wind and surface heat flux analysis suggests that the thermocline depth variations are mainly determined by wind stress fields, while the heat flux effect is important on SST.

Characteristics of the Transition Layer in the South China Sea in 1998

CTD data on standard levels collected during July and December in 1998 and the cubic spline interpolating method were used to study the characteristics of the transition layer temperature and salinity. The thermocline undergoes remarkable seasonal variation in the South China Sea (SCS), and especially in the region of the north shelf where the thermocline disappears in December. The thermocline is stronger and thicker in July than in December. There is no obvious seasonal variation in the halocline. Due to the upper Ekman transport caused by monsoon over the SCS, the thermocline slopes upward in July and downward in December from east to west in the northern SCS. The characteristics of the thermocline and halocline are influenced by local eddies in the SCS. The Zhujiang diluted flow influences significantly the SCS shelf’s halocline.

The Kelvin Wave Processes in the Equatorial Indian Ocean during the 2006-2008 IOD Events

The present study investigates the role of Kelvin wave propagations along the equatorial Indian Ocean during the 2006-2008 Indian Ocean Dipole(IOD).The 2006 IOD lasted for seven months,developing in May and reaching its peak in December,while the 2007 and 2008 IODs were short-lived events,beginning in early May and ending abruptly in September,with much weaker amplitudes.Associated with the above IODs,the impulses of the sea surface height(SSH) anomalies reflect the forcing from an intraseasonal time scale,which was important to the evolution of IODs in 2007 and 2008.At the thermocline depth,dominated by the propagation of Kelvin waves,the warming/cooling temperature signals could reach the surface at a particular time.When the force is strong and the local thermocline condition is favorable,the incoming Kelvin waves dramatically impact the sea surface temperature(SST) in the eastern equatorial Indian Ocean.In July 2007 and late July 2008,the downwelling Kelvin waves,triggered by the Madden-Julian Oscillation(MJO) in the eastern and central equatorial Indian Ocean,suppressed the thermocline in the Sumatra and the Java coast and terminated the IOD,which made those events short-lived and no longer persist into the boreal fall season as the canonical IOD does.

Events of decadal thermocline variations in the South Pacific Ocean

The SODA data generated from a numerical model with data assimilation axe used to study the decadal thermal anomalies in the thermocline of the South Pacific. Three notable events of decadal thermocline variations are found. First, two major warm subduction events originated from outcrop regions centered at 30°S, 150°W in the South Pacific Ocean occurred between 1960s and 1980s propagating toward the western Tropics and at 30°S, 90°W in the late 1970s propagating directly toward the eastern Tropics. Second, a special westward warm event originating from the eastern boundary around 15°S occurred in the early 1980s. Thirdly, a distinct zonal location transition of the positive temperature anomalies near 10°S took place in the late 1970s. The results suggest that the warm events in the subtropical South Pacific region are important to the decadal variability of the western tropical Pacific before the late 1970s and to the eastern tropical Pacific after the late 1970s.

Long-term variability of the sharp thermocline in the Yellow and East China Seas

Based on observed temperature data since the 1950s, long-term variability of the summer sharp thermocline in the Yellow Sea Cold Water Mass （YSCWM） and East China Sea Cold Eddy （ECSCE） areas is examined. Relationships between the thermocline and atmospheric and oceanic forcing were investigated using multiyear wind, Kuroshio discharge and air temperature data. Results show that： 1） In the YSCWM area, thermocline strength shows about 4-year and 16-year period oscillations. There is high correlation between summer thermocline strength and local atmospheric temperature in summer and the previous winter; 2） In the ECSCE area, interannual oscillation of thermocline strength with about a 4-year period （stronger in El Nifio years） is strongly correlated with that of local wind stress. A transition from weak to strong thermocline during the mid 1970s is consistent with a 1976/1977 climate shift and Kuroshio volume transport; 3） Long-term changes of the thermocline in both regions are mainly determined by deep layer water, especially on the decadal timescale. However, surface water can modify the thermocline on an interannual timescale in the YSCWM area.

Long-term temperature variation of the Southern Yellow Sea Cold Water Mass from 1976 to 2006

This paper discusses the long-term temperature variation of the Southern Yellow Sea Cold Water Mass(SYSCWM)and examines those factors that infl uence the SYSCWM,based on hydrographic datasets of the China National Standard Section and the Korea Oceanographic Data Center.Surface air temperature,meridional wind speed,and sea surface temperature data are used to describe the seasonal changes.Mean temperature of the two centers of the SYSCWM had diff erent long-term trends.The temperature of the center in the west of the SYSCWM was rising whereas that of the center in the east was falling.Mean temperature of the western center was related to warm water intrusion of the Yellow Sea Warm Current,the winter meridional wind,and the winter air temperature.Summer process played a primary role in the cooling trend of temperature in the eastern center.A decreasing trend of salinity in the eastern half of the SYSCWM showed that warm water intrusion from the south might weaken,as could the SYSCWM circulation.Weakened circulation provided less horizontal heat input to the eastern half of the SYSCWM.Less lateral heat input may have led to the decreasing trend in temperature of the eastern center of the SYSCWM.Further,warmer sea surface temperatures and less heat input in the deep layers intensifi ed the thermocline of the eastern SYSCWM.A stronger thermocline had less heat fl ux input from upper layers to this half of the SYSCWM.Stronger thermocline and weakened heat input can be seen as two main causes of the cooling temperature trend of the eastern center of the SYSCWM.

Optimal Precursor Perturbations of El Ni?o in the Zebiak-Cane Model for Different Cost Functions

Optimal precursor perturbations of El Nino in the Zebiak-Cane model were explored for three different cost functions. For the different characteristics of the eastern-Pacific （EP） El Nino and the central-Pacific （CP） El Nino, three cost functions were defined as the sea surface temperature anomaly （SSTA） evolutions at prediction time in the whole tropical Pacific, the Nino3 area, and the Nino4 area. For all three cost functions, there were two optimal precursors that developed into El Nino events, called Precursor Ⅰ and Precursor Ⅱ. For Precursor Ⅰ, the SSTA component consisted of an east-west （positive-negative） dipole spanning the entire tropical Pacific basin and the thermocline depth anomaly pattern exhibited a tendency of deepening for the whole of the equatorial Pacific. Precursor Ⅰ can develop into an EP-El Nino event, with the warmest SSTA occurring in the eastern tropical Pacific or into a mixed El Nino event that has features between EP-El Nino and CP-El Nino events. For Precursor Ⅱ, the thermocline deepened anomalously in the eastern equatorial Pacific and the amplitude of deepening was obviously larger than that of shoaling in the central and western equatorial Pacific. Precursor Ⅱ developed into a mixed El Nino event. Both the thermocline depth and wind anomaly played important roles in the development of Precursor Ⅰ and Precursor Ⅱ.

Research on the Propagation Acting of the Equatorial Planetary Waves on the Western Equatorial Pacific Warm Pool Heat

Based on the long-term buoy data from the Tropical Atmosphere Ocean ( TAO ) —array during the TOGA ( Tropical Ocean and Global Atmosphere ) Program (19801996), the propagation acting of the Equatorial planetary waves on the Western Equatorial Pacific warm pool heat is analyzed. Results show that the zonal heat transmission in the Western Equatorial Pacific takes palace mainly in the subsurface water and spreads eastwards along the thermocline; while the seasonal westward-spreading heat change structure occurs in the mixed layers in the middle and western Pacific. The standing-form transmission in the western Pacific appears in the thermocline layer, while in the eastern pacific, it exists in the mixed layer as well as in the thermocline layer. The standing-form and eastward-spreading sign of zonal heat transmitting in the upper water is predominant and strong, and the westward sign is weak.The component force of Kelvin Equatorial wave pressure runs through the western and eastern Equatorial pacific, and transmits heat energy eastwards. And the heat transmitted by zonal current component occurs mostly in the western Pacific; The heat transmitted by the component force of Rossby wave pressure mainly appears in the eastern and middle areas of the Pacific, while the zonal current component transmitting occurs mainly in the western Pacific; Mixed-Rossby gravity wave’s action on the zonal current is stronger than that of the thermocline layer. In the mean state, the standing wave model of Equatorial Pacific up layer ocean temperature confines the transport of western Pacific warm pool heat to the eastern Pacific. Under abnormal conditions, the standing wave model of Equatorial Pacific up layer ocean temperature weakens, the eastwardly transmitting model enhances, and subsequently n^the El Ni o event occurs.

Research on the Distance of the Active Sonar under the Effects of the Thermocline

The existence of thermocline changes the acoustic structure and effects the direction of the stared rays. This paper analyzes the working processs of the active sorer, and the mathematical models. The detection probaility of the active sonar under thenmoline is studied. First, the detection distance without thermocline is estimat- ed, then the effect of thermocline＇s depth and sound velocity changes on detecting submarine probability are discussed, and based on this, the effects of the sea condition on searching submarine probability is discussed, lastly the distance of active sonar is calculatod under thermocline. The results indicate that tufter thennocline, the distance of the active sonar becomes obvious short, and with the sea condition becoming rough, the effect is more dear.

Thermocline Thickness Evaluation on Stratified Thermal Energy Storage Tank of Co-generated District Cooling Plant

Temperature distribution of water inside of thermal storage tank reflects the condition of cooling energy stored in the tank. It can be used to define important parameters required for evaluation the performance of thermal storage tank. In this study, the thermocline thickness was evaluated for two cases of charging cycles： case Ⅰ at 393 m^3 / hr and case Ⅰ at 524 m^3 / hr. Hourly data were used for the study. Curve fitting approach was used to plot the temperature distribution profiles. Results obtained revealed that the fitting function enabled quantification of thermocline thickness of the thermal storage tank. The parameters that were determined are average cool-warm water temperatures and cool water depth in the tank. The approach offer an advantage to determine the thermocline thickness based on functionally relationship of temperature distribution profile. Results obtained shown that thermocline thickness increases at the higher flow rate. This was due to increased mixing of cool and warm water. It was also noted that thicker thermocline occurred in the region nearby the inlet diffuser. The findings indicate that the operating thermal energy storage as performing as a stratified tank.

Change of Indonesian Throughflow outflow in response to East Asian Monsoon and ENSO activities since the Last Glacial

The Indonesian Throughflow （ITF） links upper ocean waters of the west Pacific and Indian Ocean, modulates heat and fresh water budgets between these oceans, and in turn plays an important role in global climate change. The climatic phenomena such as the East Asian monsoon and E1 Nifio-Southern Oscillation （ENSO） exert a strong influence on flux, water properties and vertical stratification of the ITF. This work studied sediments of Core SO 18462 that was retrieved from the outflow side of the ITF in the Timor Sea in order to investigate response of the ITF to monsoon and ENSO activities since the last glacial. Based on Mg/Ca ratios and oxygen isotopes in shells of planktonic foraminiferal surface and thermocline species, seawater temperatures and salinity of both surface and thermocline waters and vertical thermal gradient of the ITF outflow were recon- structed. Records of Core SO18462 were then compared with those from Core 3cBX that was recovered from the western Pa- cific warm pool （WPWP）. The results displayed that similar surface waters occurred in the Timor Sea and the WPWP during the last glacial. Since -16 ka, an apparent difference in surface waters between these two regions exists in salinity, indicated by much fresher waters in the Timor Sea than in the WPWP. In contrast, there is little change in difference of sea surface temper- atures （SSTs）. With regard to thermocline temperature （TT）, it increased until -11.5 ka since the last glacial, and then re- mained an overall unchanged trend in the WPWP but continuously decreased in the Timor Sea towards the late Holocene. Since ~6 ka, thermocline waters have tended to be close to each other in between the Timor Sea and the WPWP. It is indicated that intensified precipitation due to East Asian monsoon and possible ENSO cold phase significantly freshened surface waters over the Indonesian Seas, impeding the ITF surface flow and in turn having enhanced thermocline flow during the Holocene. Consequently, thermocline water of the ITF outflow was cooling and thermocline was shoaling towards the late Holocene. It is speculated that, in addition to strengthening of East Asian winter monsoon, increasing ENSO events during the late Holocene likely played an important role in influencing thermocline depth of the ITF outflow.

Tropical storm-forced near-inertial energy dissipation in the southeast continental shelf region of Hainan Island

Near-inertial motion is an important dynamic process in the upper ocean and plays a significant role in mass, heat, and energy transport across the thermocline. In this study, the dissipation of wind-induced near-inertial energy in the thermocline is investigated by using observation data collected in July and August 2005 during the tropical storm Washi by a moored system at(19°35′N, 112°E) in the continental shelf region off Hainan Island. In the observation period, the near-inertial part dominated the observed ocean kinetic energy and about 80% of the near-inertial energy dissipated in the upper layer. Extremely strong turbulent mixing induced by near-inertial wave was observed in the thermocline, where the turbulent energy dissipation rate increased by two orders of magnitude above the background level. It is found that the energy loss of near-inertial waves in the thermocline is mainly in the large-scales. This is different from the previous hypothesis based on "Kolmogorov cascade" turbulence theory that the kinetic energy is dissipated mainly by small-scale motions.