Yellow Sea In Summer Research Articles

Forcing mechanisms of heat content variations in the Yellow Sea

Forcing mechanisms of heat content variations in the Yellow Sea (YS) are studied through analysis of a hindcast simulator for 1958–2007 using a two–way nested global—Northwest Pacific model. During the cooling season (September to February of next year), changes in heat content integrated over the YS are primarily caused by variations in latent and sensible heat fluxes at surface, which can be further related to variations of the East Asian Winter Monsoon and the Arctic Oscillation. The lateral heat transport by the Yellow Sea Warm Current (YSWC) contributes to heat content variation in the deep region. Variation of the YSWC can be related to wind variation over the YS. During the warming season (March to August), variation in the changes of heat content in the upper layer is primarily caused by variation in shortwave radiation at surface, which can be related to variation in the atmospheric pressure system of the Western Pacific Subtropical High that influences the YS in summer.

The Variations of the Abundance and Distribution Pattern of <i>Calanus sinicus</i> Brodsky in the Western South Yellow Sea in Spring and Summer

Multidisciplinary comprehensive investigations were conducted in the western South Yellow Sea in the summer, 2006 and spring, 2007. The abundance and distribution pattern of a dominant zooplankton species, Calanus sinicus, and its relationship with the environmental conditions are analyzed. The data of C. sinicus and hydrological parameter in the spring and summer of 1959 are used to compare the variations of C. sinicus and hydrographical conditions in the past 50 years. Results show that the abundance of C. sinicus was significantly higher in 2006 and 2007 than that in 1959 which may be correlate with both the bottom-up and top-down effects; the distribution pattern in the spring of the two years was similar, on the contrary, However, the hydrographical characteristics were conspicuously different between the two springs, for example, the coverage and strength of the Qingdao Cold Water Mass, the penetrating pathway of Yellow Sea Warm Current and the distribution pattern of the oceanic front. Correspondingly, the distribution pattern of C. sinicus in the summer of the two years showed great differences. Thus, it is suggested that the distribution pattern of C. sinicus in summer might be influenced by the hydrographical characteristics in spring, which probably further affects the present of some economically important fishes which fed on C. sinicus.

Summer surface layer thermal response to surface gravity waves in the Yellow Sea

The Princeton Ocean Model (POM) with generalized coordinate system (POMgcs) is used to study the summer surface-layer thermal response to surface gravity waves in the Yellow Sea (YS). The parameterization schemes of wave breaking developed by Mellor and Blumberg (J Phys Oceanogr 34:693–698, 2004) and Kantha and Clayson (Ocean Model 6:101–124, 2004), respectively, and Stokes production developed by Kantha and Clayson (Ocean Model 6:101–124, 2004) are both included in the Mellor–Yamada turbulence closure model Mellor and Yamada (Rev Geophys 20:851–875, 1982) of POMgcs. Numerical results show that surface gravity waves impact the depth of surface mixed layer of temperature in the YS in summer. The surface mixed layer in the YS cannot be reproduced well and has a visible difference from the observation if the parameterization schemes are not included. A diagnostic analysis of turbulent kinetic energy suggests that both Stokes production and wave breaking play key roles in enhancing the turbulent mixing near the sea surface in the YS. Stokes production seems to have a greater impact throughout the upper mixed layer in the YS in summer than that of wave breaking. In addition, a diagnostic analysis of the momentum balance shows that Coriolis–Stokes forcing has a significant effect on the momentum budget in the upper layer in the YS, and surface gravity waves are able to reduce the velocity of mean flow near the surface and make the mean flow near the surface more homogeneous vertically in the YS.

Semi-continuous measurement of water-soluble ions in PM2.5 in Jinan, China: Temporal variations and source apportionments

Abstract To better understand secondary aerosol pollution and potential source regions, semi-continuous measurement of water-soluble ions in PM2.5 was performed from December 2007 to October 2008 in Jinan, the capital of Shandong Province. The data was analyzed with the aid of backward trajectory cluster analysis in conjunction with redistributed concentration field (RCF) model and principal component analysis (PCA). SO 4 2 − , NO 3 − and NH 4 + were the most abundant ionic species with annual mean concentrations (±standard deviations) of 38.33 (±26.20), 15.77 (±12.06) and 21.26 (±16.28) μg m−3, respectively, which are among the highest levels reported in the literatures in the world. Well-defined seasonal and diurnal patterns of SO 4 2 − , NO 3 − and NH 4 + were observed. The fine sulfate and nitrate oxidation ratios (SOR and NOR) were much higher in summer (SOR: 0.47 ± 0.13; NOR: 0.28 ± 0.03) than those in other seasons (SOR: 0.17–0.30; NOR: 0.12–0.14), indicating more extensive formations of SO 4 2 − and NO 3 − in summer. The most frequent air masses connected with high concentrations of SO 4 2 − , NO 3 − and NH 4 + originated from Shandong Province in spring, autumn and winter, while from the Yellow Sea in summer, and then slowly traveled in Shandong Province to Jinan. RCF model indicated that Shandong Province was the main potential source region for SO 4 2 − and NO 3 − and other potential source regions were also identified including the provinces of Hebei, Henan, Anhui and Jiangsu and the Yellow Sea. Principal component analysis indicated that the major sources contributing to PM2.5 pollution were secondary aerosols, coal/biomass burnings and traffic emissions.

하계 동중국해 북부 해역에서 저층 냉수괴의 거동

황해저층냉수는 지난 동계의 차고 건조한 바람에 의해 생성되어, 하계에 황해 중앙골을 따라 남하하는 것으로 알려져 있다. 동중국해 북부해역에서 황해저층냉수의 특성과 거동을 파악하기 위해 2003년부터 2009년까지 하계에 관측한 자료를 분석하였다. 수괴분석을 통해 본 연구해역에 영향을 미치는 황해저층냉수를 새롭게 정의하여 북서저층냉수라고 명명하였고, 수온 <TEX>$13.2^{\circ}C$</TEX> 이하, 염분 32.6~33.7 psu와 밀도 <TEX>$24.7{\sim}25.5\;{\sigma}_t$</TEX>로 특성지었다. 지형류 계산에 의해 연구해역에서 북서저층냉수는 약 2 cm/s 이하의 속도로 남하하는 것으로 추정하였다. 정의한 북서저층냉수는 수온의 범위와 자지하고 있는 영역에서 연간 변동을 보이며, 이러한 변동은 이전 해 동계 황동중국해의 표층수온의 변화와 밀접한 관련이 있었고, 동계 표층수온의 변화는 동계 기온에 의한 영향이 지배적임을 확인하였다. 동계 동중국해 표층수온은 북극진동 지수와 높은 상관성을 보이며, 동계의 북극진동이 음일 때 동중국해 표층수온이 하강하였고, 이러한 영향으로 북서저층냉수 세력이 동중국해 북부 해역까지 저수온을 보이면서 확장하였다. 동 연구는 동계의 북극진동지수, 황동중국해 겨울철 표층수온, 동중국해 북부의 북서저층냉수가 역학적으로 관련이 있음을 보였고, 이를 바탕으로 하계 동중국해 북부해역에서 저층냉수의 거동을 유추할 수 있을 것으로 사료된다. The Yellow Sea Cold Water (YSCW) is formed by cold and dry wind in the previous winter, and is known to spread southward along the central trough of the Yellow Sea in summer. Water characteristics of the YSCW and its movement in the northern East China Sea (ECS) are investigated by analyzing CTD (conductivity-Temperature-Depth) data collected from summertime hydrographic surveys between 2003 and 2009. By water mass analysis, we newly define the North Western Cold Water (NWCW) as a cold water mass observed in the study area. It is characterized by temperature below <TEX>$13.2^{\circ}C$</TEX>, salinity of 32.6~33.7 psu, and density (<TEX>${\sigma}_t$</TEX>) of 24.7~25.5. The NWCW appears to flow southward at about a speed less than 2 cm/s according to the geostrophic calculation. The newly defined NWCW shows an interannual variation in the range of temperature and occupied area, which is in close relation with the sea surface temperature (SST) over the Yellow Sea and the East China Sea in the previous winter season. The winter SST is determined by winter air temperature, which shows a high correlation with the winter-mean Arctic Oscillation (AO) index. The negative winter-mean AO causes the low winter SST over the Yellow Sea and the East China Sea, resulting in the summertime expansion and lower temperature of the NWCW in the study area. This study shows a dynamic relation among the winter-mean AO index, SST, and NWCW, which helps to predict the movement of NWCW in the northern ECS in summer.

Effect of surface wave breaking on the surface boundary layer of temperature in the Yellow Sea in summer

Near-surface enhancement of turbulent mixing and vertical mixing coefficient for temperature owing to the effect of surface wave breaking is investigated using a two-dimensional (2-D) ocean circulation model with a tidal boundary condition in an idealized shelf sea. On the basis of the 2-D simulation, the effect of surface wave breaking on surface boundary layer deepening in the Yellow Sea in summer is studied utilizing a 3-D ocean circulation model. A well-mixed temperature surface layer in the Yellow Sea can be successfully reconstructed when the effect of surface wave breaking is considered. The diagnostic analysis of the turbulent kinetic energy equation shows that turbulent mixing is enhanced greatly in the Yellow Sea in summer by surface wave breaking. In addition, the diagnostic analysis of momentum budget and temperature budget also show that surface wave breaking has an evident contribution to the turbulent mixing in the surface boundary layer. We therefore conclude that surface wave breaking is an important factor in determining the depth of the surface boundary layer of temperature in the Yellow Sea in summer.

Simultaneous enumeration of diatom, protozoa and meiobenthos from marine sediments using Ludox-QPS method

The Ludox-QPS method is a newly developed technique, which combines the Ludox HS 40 density centrifugation and quantitative protargol stain, to enumerate marine ciliates with good taxonomic resolution. We tested the method for simultaneous enumeration of diatoms, protozoa and meiobenthos and compared its extraction efficiency for meiobenthos with that of the routine Ludox-TM centrifugation and a modified protocol using Ludox HS 40. We conducted the evaluation with a sample size of 8.3 ml each from sandy, muddy-sand and muddy sediments collected from the intertidal area of the Yellow Sea in summer 2006 and spring 2007. The Ludox-QPS method not only produced high extraction efficiencies of 97±1.3% for diatoms and 97.6±0.8% for ciliates, indicating a reliable enumeration for eukaryotic microbenthos, but also produced excellent extraction efficiencies of on average 97.3% for total meiobenthos, 97.9% for nematodes and 97.8% for copepods from sands, muddy sands and mud. By contrast, the routine Ludox-TM centrifugation obtained only about 74% of total meiobenthos abundance with one extraction cycle, and the modified Ludox HS 40 centrifugation yielded on average 93% of total meiobenthos: 89.4±2.0% from sands, 93±4.1% from muddy sands and 97.1±3.0% from mud. Apart from the sediment type, sample volume was another important factor affecting the extraction efficiency for meiobenthos. The extraction rate was increased to about 96.4% when using the same modified Ludox centrifugation for a 4 ml sediment sample. Besides the excellent extraction efficiency, the Ludox-QPS method obtained higher abundances of meiobenthos, in particular nematodes, than the routine Ludox centrifugation, which frequently resulted in an uncertain loss of small meiobenthos during the sieving process. Statistical analyses demonstrated that there were no significant differences between the meiobenthos communities revealed by the Ludox-QPS method and the modified Ludox HS 40 centrifugation, showing the high efficiency of the Ludox-QPS method for simultaneous enumeration of diatom, protozoa and meiobenthos. Moreover, the comparatively high taxonomic resolution of the method, especially for diatoms and ciliates, makes it feasible to investigate microbial ecology at community level.

Upwelling and surface cold patches in the Yellow Sea in summer: Effects of tidal mixing on the vertical circulation

A three-dimensional, prognostic, wave–tide–circulation coupled numerical model is developed to study the effects of tidal mixing on the summertime vertical circulation in the Yellow Sea (YS). The distribution and mechanisms of upwelling are investigated by numerical means. Validated by historical tide gauge data, satellite sea surface temperature (SST) data, and cruise observation data, the model shows satisfactory performances in reproducing the dominant tidal system and three-dimensional sea temperature structure. Model results suggest that strong tidal mixing plays an important role in the formation of the vertical circulation in the YS. The Yellow Sea Cold Water Mass (YSCWM) is fringed by typical tidal mixing fronts (TMFs), which separate the cold, stratified water at the offshore side from the warm, well-mixed, shallow water at the other side. Considerable baroclinic gradient across the TMF makes the frontal zone the spot where the most active vertical circulation occurs; a secondary circulation is triggered with a distinct upwelling branch occurring mainly on the mixed side of the front. The numerical model produces systematic upwelling belts surrounding the YSCWM, and the upwelling is essentially induced by the TMF over sloping topography. The relative importance of tidal mixing and wind forcing for upwelling is further examined in numerical experiments. The southerly wind enhances the upwelling off the western coasts, but its overall influences in the whole YS are less important than tidal mixing. As shown by both satellite data and numerical modeling, the summertime SST field in the YS is featured by the stable existence of several site-selective surface cold patches (SCPs), most of which scatter in the waters off convex coastlines. One of the SCPs is found off Subei Bank, and the others are located off the eastern tip of Shandong Peninsula and off the three tips of Korean Peninsula. Two processes give rise to the SCP: on the one hand, TMF-induced upwelling supplies cold water from the deep layer; on the other hand, tidal mixing itself can stir the bottom water upward and homogenize the water column vertically. In the waters around the tips of peninsula in the YS, the tidal currents are extraordinarily strong, which provides a possible explanation for the site-selectivity of the SCPs.

Tidal current observation in the southern Yellow Sea in the summers of 2001 and 2003

Direct current observations in the Yellow Sea interior are very scarce due to intense fishing and trawling activities. Most previous studies on tides in the area were based on coastal measurements or satellite altimeter sea levels and have not been rigorously compared with direct measurements. In this paper, tidal currents are studied with current profiles from three bottom-moored Sontek Acoustic Doppler Profilers (ADPs) deployed in the southern Yellow Sea in summer of 2001 and 2003. The measured current series were dominated by tidal currents. Maximum velocities are between 40–80 cm/s at the mooring stations. M2 current is the most dominant primary tidal constituent, while MS4 and M4 are the most significant shallow water tides with much smaller amplitudes than the primary tides.

Meso-scale spatial distribution of large tintinnids in early summer in southern Yellow Sea

The spatial distribution of some large tintinnid species (nominally>76 mu m) was investigated according to samples collected by vertical towing in cruises to the southern Yellow Sea in summer 2000-2002 and 2004. Eight species were identified: Codonellopsis mobilis, Leprotintinnus netritus, Tintinnopsis karajacensis, T. japonica, T. kiaochowensis, T. butschlii, T. radix, and Parafavella sp. With maximum abundance of 158.2 ind/L in June 2004, C mobilis was the dominant species, lasting from May to July 2004. Tintinnid communities were patchy and distributed mainly in shallow waters along the shore.

Vertical Migration of Sound Scatterers in the Southern Yellow Sea in Summer

Acoustic volume backscattering strength data were collected and Conductivity Temperature Depth (CTD) measur e m e n t s were conducted in the southern Yellow Sea in summer 2005 and 2006. The high temporal and vertical resolution acoustic data measured with a 307 kHz Acoustic Doppler Current Profiler (ADCP) and a 250 kHz acoustic Doppler profile (ADP) had dominant diel variation, which resulted from vertical migration of sound scatterers. Some scatterers congregating in the bottom layer in the daytime migrated upward at dusk, and migrated downward into the bottom layer at dawn. The migration speeds were estimated. More than 33 days data show that the diel migration varies with time. The feature of migration measured with ADCP and ADP is consistent to some extent with what is described in the study on vertical migration of zooplankton in the southern Yellow Sea with conventional net samples.

Diversity of benthic boundary layer fauna in a section of the Yellow Sea in summer

Diversity of benthic boundary layer fauna in a section of the Yellow Sea in summer

Current observations in the southern Yellow Sea in summer

Current data from three moored Acoustic Doppler Profilers (ADPs) deployed in the southern Yellow Sea at sites A (124.17°E, 34.82°N), B (122.82°E, 35.65°N) in summer 2001 and site C (120.85°E, 34.99°N) in summer 2003 were analyzed in this paper. Features of the tidal and residual currents were studied with rotary spectral and cross-spectral methods. Main achievements were as follows: 1) Tides dominated the currents. At sites A and B, the semidiurnal tidal current was basically homogeneous in the whole depth, taking a clockwise rotation at site A, and near-rectilinear counterclockwise rotation at site B; while the diurnal tidal current was strong and clockwise near the surface, but decreased and turned counterclockwise with depth; at site C, semidiurnal tidal current dominated and diurnal current took the second, both of which were counterclockwise and vertically homogeneous. Inertial motion contributed to the clockwise component of diurnal fluctuations; 2) The 3–5d fluctuation of residual current was found at site C and attributed to the response of current to meridional wind, with a lag time of approximately 1.8d; 3) Mean residual flows at sites A and B in 2001 probably suggested an anticyclonic inner circulation in the middle of the southern Yellow Sea in summer.

Statistic characteristics of thermal structure in the southern Yellow Sea in summer

Based on the temperature data along 34°N, 35°N and 36°N sections in August from 1977 to 2003, the structure and formation of the Southern Yellow Sea Cold Water Mass (SYSCWM) and its responses to El Nino events are analyzed. Results show that: (1) There exist double cold cores under the main thermocline along the 35°N and 36°N sections. Also, double warm cores exist above the main thermocline along the 36°N section. (2) Thermocline dome by upwelling separates the upper warm water into two parts, the eastern and western warm waters. Additionally, the circulation structure caused by upwelling along the cold front and northeastward current along the coast in summer is the main resons of double warm cores along the 36°N section. The intermediate cold water is formed in early spring and moves eastward slowly, which results in the formation of the western one of double cold cores. (3) Position of the thermocline dome and its intensity vary interannually, which is related to El Nino events. However, the deep cold water temperature is hardly affected by El Nino events. In most El Nino years, position of the thermocline dome shifted eastwards and depth of the dome upper limit decreases.

Surface circulation patterns observed by drifters in the Yellow Sea in summer of 2001, 2002 and 2003

In summer of 2001, 2002 and 2003, ten, six and seventeen satellite-tracked surface drifters with drogues centered at 15 and 4 m were deployed, respectively, in the southern Yellow Sea (YS). 23 drifters of them transmitted useful data of at least 30 days. The wind-driven component of the drift was removed from the original drift velocity of drifters. The wind data used are from NCEP (National Center for Environmental Prediction), USA.

The combined effects of temperature and food supply on Calanus sinicus in the southern Yellow Sea in summer

The effects of temperature and food availability on the life history strategy of the planktonic copepod Calanus sinicus in the southern Yellow Sea in summer were studied in this paper. The fifth copepodite stage (CV) dominates the population in the central part of the southern Yellow Sea, where the Yellow Sea Cold Water Mass (YSCWM) occurs below the thermocline. Incubation experiments were conducted on CV C. sinicus caught from the YSCWM to examine the effects of temperature and food availability. Temperature at the surface (27degreesC) is lethal to CVs regardless of food availability. At the temperature in the middle of the thermocline (18degreesC), survival time of the specimens depends on food availability, being similar to20 days in treatments without extra food supply. At the temperature in the YSCWM (9degreesC), most animals survive at the end of 27 day incubation even in treatments without food supply. Developmental rate of CVs at 9degreesC without extra food supply is extremely low. The increase of either temperature or food supply promotes the developmental rate of CVs. According to these results, the surface layers with high temperature and low food abundance are detrimental for the survival and reproduction of C. sinicus. Low temperature and low food availability in the YSCWM help CV to maintain a much lower developmental rate and higher survival rate. The ecological trait of C. sinicus in the southern Yellow Sea in summer cannot be sufficiently explained solely by the effects of temperature.

Life history strategies of Calanus sinicus in the southern Yellow Sea in summer

Ecological and physiological features of the planktonic copepod Calanus sinicus in the southern Yellow Sea in summer were studied to reveal its life history strategy. From the coastal shallow waters to the central part of the southern Yellow Sea, a shift of the stage composition occurs from being dominated by the egg-nauplius stage to being dominated by the fifth copepodite (CV) stage. Most CVs reside in the Yellow Sea Cold Water Mass (YSCWM), where both temperature and food abundance are low. CVs in the YSCWM have longer body lengths, heavier body weights and higher carbon contents than those outside the YSCWM. Onboard incubations show that the development of CVs in the YSCWM is suspended. Energy conservation, development suspension and lack of diel vertical migration (DVM) behavior suggest a diapause status for the CVs in the YSCWM, although vertical distribution patterns indicate the CV individuals are not fully synchronous in physiology and development. This adaptive oversummering strategy would help C. sinicus to live through the warm and food-limited summer in the central part of the southern Yellow Sea; both low temperature and low food supply are necessary for CV to maintain the resting state in the YSCWM. Calanus sinicus exhibits different life history strategies in different regions of the southern Yellow Sea in summer.

Spatial distribution of Euphausia pacifica (Euphausiacea: Crustacea) in the Yellow Sea

Euphausia pacifica were collected in the Yellow Sea in summer (August, 1997) and winter (February, 1998), and their distribution was investigated in terms of the developmental stages in relation to environmental factors (temperature, salinity and chlorophyll a). In summer, the water column was highly stratified with a thermocline between 10-30 m depth, whereas the water column was well mixed in winter. Seasonal variation in temperature was large, ranging between 6.3 and 28.8°C in summer and 3.9 and 12.2°C in winter. Chlorophyll a concentration changed little seasonally but a high concentration was observed in coastal areas. Salinity in the two seasons varied little spatio- temporally. In the studied area and sampling period, E.pacifica was the most dominant euphausiid species (99.7 and 99.8% in summer and winter, respectively), and comprised adults and juveniles (74.6% in summer and 41.9% in winter), furcilia (17.5 and 44.9%) and calyptopis (7.9 and 13.1%). The spatial distribution of the E.pacifica population varied seasonally depending on developmental stage and appeared to be related primarily to the seawater temperature and secondly to the chloro- phyll a concentration, but not to salinity. In summer, adults were abundant in areas below 10°C, and furcilia and calyptopis above 9°C. In winter, adults were confined to areas between 7 and 10°C, and furcilia and calyptopis, to areas between 6 and 8°C. Furcilia and calyptopis were concentrated in the vicinity, or at the center of chlorophyll a-rich water masses, whereas adults seemed to avoid those water masses.

Influence of stratification on residual tidal currents in the Yellow Sea

The M2 tide and residual current generation in the Yellow Sea are examined using the Blumberg and Mellor [1987] numerical coastal ocean circulation model. With no stratification the model tide and tidal currents show good agreement with the observed tide and tidal currents. Coherent residual currents are predicted around the southwest of Korea, flowing northward as a strong jet with a maximum speed of 8 cm s−1, and around Yangtze Bank, flowing southeastward as a weak broad current. With initial stratification, tidal mixing occurs in the bottom boundary layer, which leads to surface tidal fronts around Yangtze Bank and the southwest of Korea, and our model experiments reproduce successfully the basic water property structure in these regions. The resulting stratified tidal rectification intensifies the residual currents at the front and at the top of the bottom boundary layer over the sloping bottom, so that the vertical structure of the residual currents is modified. The strong residual currents in the top of the bottom mixed layer around Yangtze Bank support the interpretation of Kim et al. [1991] for the southeastward movement of Yellow Sea Bottom Cold Water in summer. The residual currents in the surface layer reach ∼40% of the mean currents observed by Beardsley et al. [1992] using satellite‐tracked drifters deployed in the Yellow Sea in summer. These results suggest that stratified tidal rectification is an important process in driving the summertime subtidal flow in the Yellow Sea.

Seasonal variation of circulations in the East China Sea and the Yellow Sea

Seasonal variation of the water circulations in the East China Sea and the Yellow Sea is investigated with use of a robust diagnostic numerical model. Water circulations in four season are calculated diagnostically from the observed water temperature and salinity data from JODC (Japan Oceanographic Data Center) and wind data from COADS (Comprehensive Ocean-Atmosphere Data Set). Counter-clockwise circulations are developed at the upper and middle layers and a clockwise one at the lower layer in the central part of he Yellow Sea in summer. On the other hand, a clockwise circualtion is developed from the surface to the bottom in the Yellow Sea and a counter-clockwise one in, the northern part of the East China Sea in winter.