Hydrographic condition and variability in the Yellow Sea and East China Sea during winter

This paper deals with the hydrographic condition and variability in the Yellow Sea and East China Seas during winter. It is based on data obtained from the joint Chinese(Norwegian surveys during the period 1984 to 1995. The results indicated that:(1) From November to March, the water temperature there was decreasing, the Yellow Sea Cold Water, the Yellow Sea Warm Current and Yellow Sea Coastal Current mainly dominated the survey areas;(2) The vertical distribution of hydrographic factors varied through the winter. From November to March the thickness of upper homogeneous layer became thicker and the thermocline, halocline and Yellow Sea Cold Water less pronounced, in January March, these features disappeared and the hydrographic conditions were almost homogenous through the whole water column from surface to bottom;(3) The Yellow Sea Cold Water mass and Yellow Sea Warm Current showed strong clear inter annual variation. The temperature and salinity of Yellow Sea Cold Water were more stable. However, its relative volume in the stronger year(November, 1986) was 4 44 times that in the weaker year(Novemner, 1985). The Yellow Sea Warm Current’s speed in the stronger year(January, 1986) was 1.21 times that in the weaker year(January, 1992);(4) Anchovy was mainly distributed in the warm or cold water tongue areas formed by Yellow Sea Warm Current or Yellow Sea Coastal Current with temperature of 11 13℃.The thermocline had apparent effects on their vertical migration and they tended to stay above it most of the day.

An N-shape thermal front in the western South Yellow Sea in winter

An N-shape thermal front in the western South Yellow Sea （YS） in winter was detected using Advanced Very High Resolution Radiation （AVHRR） Sea Surface Temperature data and in-situ observations with a merged front-detecting method. The front, which exists from late October through early March, consists of western and eastern wings extending roughly along the northeast-southwest isobaths with a southeastward middle segment across the 20--50 m isobaths. There are north and south inflexions connecting the middle segment with the western and eastern wings, respectively. The middle segment gradually moves southwestward from November through February with its length increasing from 62 km to 107 km and the southern inflexion moving from 36.2°N to 35.3°N. A cold tongue is found to coexist with the N-shape front, and is carried by the coastal jet penetrating southward from the tip of the Shandong Peninsula into the western South YS as revealed by a numerical simulation. After departing from the coast, the jet flows as an anti-cyclonic recirculation below 10 m depth, trapping warmer water originally carried by the compensating Yellow Sea Warm Current （YSWC）. A northwestward fowing branch of the YSWC is also found on the lowest level south of the front. The N-shape front initially forms between the cold tongue and warm water involved in the subsurface anti-cyclonical recirculation and extends upwards to the surface through vertical advection and mixing. Correlation analyses reveal that northerly and easterly winds tend to be favorable to the formation and extension of the N-shape front probably through strengthening of the coastal jet and shifting the YSWC pathway eastward, respectively.

Wintertime meso-scale horizontal distribution of large tintinnids in the southern Yellow Sea

Spatial distribution of some large tintinnid species (nominally > 76 μm) is investigated on samples vertically towed in the southern Yellow Sea in winters of 2001 to 2004. Nine tintinnid species are recorded: Codonellopsis morchella, Stenosemella pacifica, S. steini, Tintinnopsis schotti, T. radix, T. karajacensis, Eutintinnus tenuis, Parafavella sp., Leprotintinnus neriticus, of which C. morchella and T. radix dominated in the warm tongue-shaped zone of the Yellow Sea Warm Current (YSWC), and S. pacifica is the next in abundance. Our study shows that these tintinnids occur repeatedly in certain special distribution patterns.

Winter Meso-Scale Shear Front in the Yellow Sea and Its Sedimentary Effects

In this paper,the authors explored the presence of shear fronts between the Yellow Sea Coastal Current(YSCC) and the monsoon-strengthened Yellow Sea Warm Current(YSWC) in winter and their sedimentary effects within the shear zone based on a fully validated numerical model.This work added the wind force to a tidal model during simulating the winter baroclinic circulation in the Yellow Sea.The results indicate that the YSWC is significantly strengthened by wind-driven compensation due to a northeast monsoon during winter time.When this warm current encounters the North Shandong-South Yellow Sea coastal current,there is a strong reverse shear action between the two current systems,forming a reverse-S-shaped shear front that begins near 34?N in the south and extends to approximately 38?N,with an overall length of over 600 km.The main driving force for the formation of this shear front derives from the circulation system with the reverse flow.In the shear zone,temperature and salinity gradients increase,flow velocities are relatively small and the flow direction on one side of the shear zone is opposite to that on the other side.The vertical circulation structure is complicated,consisting of a series of meso-and small-scale anti-clockwise eddies.Particularly,this shear effect significantly hinders the horizontal exchange of coastal sediments carried by warm currents,resulting in fine sediments deposition due to the weak hydrodynamic regime.

Grain size records reveal variability of the East Asian Winter Monsoon since the Middle Holocene in the Central Yellow Sea mud area,China

Three cores （ZY-1, ZY-2 and ZY-3） retrieved from the Central Yellow Sea mud （CYSM） were analyzed in sensitive grain size and AMS J4C dating to reconstruct the history of the East Asian Winter Monsoon （EAWM） since the Middle Holocene in the study area. The results show that these data provide a continuous history of the EAWM over the past 7.2 ka and that the EAWM can be divided into three periods： strong and highly fluctuating during 7.2-4.2 ka BP; moderate and relatively stable during 4.2-1.8 ka BP; and weakened during 1.8-0 ka BP. Compared with the East Asian Summer Monsoon （EASM） recorded in the previous studies, the evolutionary history of the EAWM broadly follows the orbital-derived winter insolation with a similar long-term step-decreased trend as the EASM. At the centennial scale, however, the EAWM intensified events correlate well with the EASM weakened events and the North Atlantic climatic variations （Bond events 0 to 5） within the dating error, most likely forced by the reduction of solar irradiance through changes in the oceanic-atmospheric circulation patterns.

Climatic change features of fog and haze in winter over North China and Huang-Huai Area

This paper revealed the climatic change characteristics of fog and haze of different levels over North China and Huang-Huai area(NCHH).It was found that the haze-prone period has changed from winter into a whole year,and the haze days(HD)in winter have increased significantly.The foggy days(FD)are half of HD.There are little difference on the number of days and trends of fog at various levels.The HD and FD show no obvious positive correlation until the 1980s.Fog has larger spatial scale,showing more in the south than in the north.Haze occurs mainly around large cities with a discrete distribution.In the background of weakened East Asian Winter Monsoon(EAWM)and sufficient particulate matter,the negative correlation between haze and wind speed is weakened,but the positive correlation between haze and moisture conditions(precipitation and humidity)is significantly strengthened.In recent years,small wind and variability appear frequently.Meanwhile,as the stable source and strong moisture absorption of the aerosol particles,the moisture condition becomes one key control factor in the haze,especially wet haze with less visibility.In contrast,the FD presents a stable positive correlation with precipitation and relative humidity,but has no obvious negative correlation with wind speed.