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An oil slick spectral experiment of nearshore sea water in the East China Sea

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Acta oceanologica Sinica 2013年第11期32卷 34-40页

作者： WANG Difeng PAN Delu GONG Fang WANG Tianyu ZHAN Yuanzeng state key laboratory of satellite ocean environment dynamics Second Institute of OceanographyState Oceanic Administration

Along with the rapid advance in global industrialization, oil spill events caused by offshore operations, trans- portation and accidents are increasing. Compared with ship surveys, monitoring oil spills through remote sensing has real-time, comprehensive, low-cost advantages, which can effectively guide cleaning and evalu- ation, and reduce the marine ecological destruction resulting from oil spills. Therefore, studying the remote sensing mechanism used to monitor marine oil spills is of great significance for ecological environmen- tal protection. This paper describes an experiment and corresponding analysis based on the above-water method, using the East China Sea coastal turbid water. The analysis shows that ＂upward short-wave＂ in ultraviolet and blue-purple bands and its displacement, along with the changing thickness, are important characteristics for distinguishing between the oil slick and the sea water, and also to differentiate oil slicks of different thicknesses. From blue to near-infrared bands, the spectrum of lube oil is flatter than that of diesel, and the diesel spectrum rises faster than the lube spectrum on the right side of the trough at 400 nm. These two features form an important basis for differentiating diesel from lube oil. These analyses will further the development of oil spill remote sensing in the East China Sea.

关键词： oil slick spectral experiment East China Sea

A joint method to retrieve directional ocean wave spectra from SAR and wave spectrometer data

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Chinese Journal of oceanology and Limnology 2016年第4期34卷 847-858页

作者：任林杨劲松郑罡王隽 state key laboratory of satellite ocean environment dynamics Second Institute of OceanographyState Oceanic Administration

This paper proposes a joint method to simultaneously retrieve wave spectra at dif ferent scales from spaceborne Synthetic Aperture Radar(SAR) and wave spectrometer data. The method combines the output from the two dif ferent sensors to overcome retrieval limitations that occur in some sea states. The wave spectrometer sensitivity coeffi cient is estimated using an ef fective signifi cant wave height(SWH), which is an average of SAR-derived and wave spectrometer-derived SWH. This averaging extends the area of the sea surface sampled by the nadir beam of the wave spectrometer to improve the accuracy of the estimated sensitivity coeffi cient in inhomogeneous sea states. Wave spectra are then retrieved from SAR data using wave spectrometer-derived spectra as fi rst guess spectra to complement the short waves lost in SAR data retrieval. In addition, the problem of 180° ambiguity in retrieved spectra is overcome using SAR imaginary cross spectra. Simulated data were used to validate the joint method. The simulations demonstrated that retrieved wave parameters, including SWH, peak wave length(PWL), and peak wave direction(PWD), agree well with reference parameters. Collocated data from ENVISAT advanced SAR(ASAR), the airborne wave spectrometer STORM, the PHAROS buoy, and the European Centre for Medium-Range Weather Forecasting(ECMWF) were then used to verify the proposed method. Wave parameters retrieved from STORM and two ASAR images were compared to buoy and ECMWF wave data. Most of the retrieved parameters were comparable to reference parameters. The results of this study show that the proposed joint retrieval method could be a valuable complement to traditional methods used to retrieve directional ocean wave spectra, particularly in inhomogeneous sea states.

关键词： Synthetic Aperture Radar(SAR) wave spectrometer directional ocean wave spectrum joint method

Wave effects on the retrieved wind field from the advanced scatterometer(ASCAT)

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Acta oceanologica Sinica 2015年第1期34卷 79-84页

作者： REN Lin YANG Jingsong ZHENG Gang WANG Juan CHEN Peng state key laboratory of satellite ocean environment dynamics Second Institute of OceanographyState Oceanic Administration

To improve retrieval accuracy, this paper studies wave effects on retrieved wind field from a scatterometer. First, the advanced scatterometer （ASCAT） data and buoy data of the National Data Buoy Center （NDBC） are collocated. Buoy wind speed is converted into neutral wind at 10 m height. Then, ASCAT data are com- pared with the buoy data for the wind speed and direction. Subsequently, the errors between the ASCAT and the buoy wind as a function of each wave parameter are used to analyze the wave effects. Wave param- eters include dominant wave period （dpd）, significant wave height （swh）, average wave period （apd） and the angle between the dominant wave direction （dwd） and the wind direction. Collocated data are divided into sub-datasets according to the different intervals of each wave parameter. A root mean square error （RMSE） for the wind speed and a mean absolute error （MAE） for the wind direction are calculated from the sub-datasets, which are considered as the function of wave parameters. Finally, optimal wave conditions on wind retrieved from the ASCAT are determined based on the error analyses. The results show the ocean wave parameters have correlative relationships with the RMSE of the retrieved wind speed and the MAE of the retrieved wind direction. The optimal wave conditions are presented in terms of dpd, swh, apd and angle.

关键词： advanced scatterometer ASCAT wind field wave effects wave parameters

Annual and interannual variations of the Western Pacific Warm Pool volume and sources of warm water revealed by Argo data

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Science China Earth Sciences 2014年第12期57卷 2269-2280页

作者： WU XiaoFen ZHANG QiLong LIU ZengHong Second Institute of oceanography State Oceanic Administration key laboratory of ocean Circulation and Waves Institute of Oceanology Chinese Academy of Sciences state key laboratory of satellite ocean environment dynamics State Oceanic Administration

Based on gridded Argo profile data from January 2004 to December 2010, together with the P-vector inverse method, the three-dimensional structure, annual and inter-annual variations in volume of the Western Pacific Warm Pool （WPWP） are studied. The variations of latitudinal and longitudinal warm water flowing into and out of the WPWP and the probable mecha- nism of warm water maintenance are also discussed. From the surface to the bottom, climatic WPWP tilts southward and its area decreases. The maximum depth could extend to 120 m, such that its volume could attain 1.86x10^5 m3. Annual variation of the WPWP volume shows two obvious peaks that occur in June and October, whereas its inter-annual variations are related to ENSO events. Based on a climatic perspective, the warm water flowing latitudinally into the pool is about 52 Sv, which is mainly through upper layers and via the eastern boundary. Latitudinally, warm water flowing outward is about 49 Sv, and this is mainly through lower layers and via the western boundary. In contrast, along the latitude, warm water flowing into and out of the pool is about 28 Sv and 23 Sv, respectively. Annual and inter-annual variations of the net transportation of the warm water demonstrate that the WPWP mainly loses warm water in the west-east direction, whereas it receives warm water from the north-south direction. The annual variation of the volume of WPWP is highly related to the annual variation of the net warm water transportation, however, they are not closely related on inter-annual time scale. On the inter-annual time scale, in- fluences of ENSO events on the net warm water transportation in the north-south direction are much more than that in the west-east direction. Although there are some limitations and simplifications when using the P-vector method, it could still help improve our understanding of the WPWP, especially regarding the sources of the warm water.

关键词： Western Pacific Warm Pool volume variability latitudinal flow longitudinal flow Argo data P-vector method

Overlooked contribution of the biological pump to the Pacific Arctic nitrogen deficit

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Science China Earth Sciences 2022年第8期65卷 1477-1489页

作者： Hongliang LI Jianfang CHEN Diana RUIZ-PINO Jingjing ZHANG Haiyan JIN Yanpei ZHUANG Youcheng BAI Jian REN Yangjie LI key laboratory of Marine Ecosystem dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou310012China state key laboratory of satellite ocean environment dynamics Hangzhou310012China Sorbonne Universités(UPMC UniversitéParis 06)-CNRS-IRD-MNHNLOCEAN Laboratory4 Place JussieuParisF-75005France Southern Marine Science and Engineering Guangdong laboratory(Zhuhai) Zhuhai519080China Polar and Marine Research Institute Jimei UniversityXiamen361021China

The nutrient-rich Pacific ocean seawater that flows through the Bering Strait into the Chukchi Sea is generally considered to be the most important source of nutrients to the Arctic euphotic *** inflow is characterized by nitrogen deficit and low nitrate/phosphate(N/P)ratios;this is ascribed to sedimentary denitrification on the Chukchi shelf by preoccupant ***,the Chukchi Sea also has high primary production,which raises the question of whether the biological pump may also significantly modulate nutrient properties of the ***,we show that nitrate concentrations of the Pacific inflow gradually decrease northward in association with notable biological *** phytoplankton N/P uptake ratio was 8.8±2.27,higher than the N/P ratio of Pacific inflow water(5-6).This uptake ratio,in combination with efficient vertical nitrogen export,serves to preferentially remove nitrogen(relative to phosphorus)from upper waters,thereby further intensifying the Arctic nitrogen ***,as large as about 111.7×10^(9)mol N yr^(−1)of nitrate was extra consumed,according to the real N/P uptake ratio rather than the ratio of the Pacific inflow,which may be as great as half the nitrogen loss ascribed to sedimentary *** findings suggest that besides sedimentary denitrification,biological disproportionate utilization of nutrients in the Chukchi Sea upper water is another important contributor to the nitrogen limitation and excess phosphorus in the upper Arctic *** the rapid Arctic change era,the predicted reinforced biological carbon pump could further impact the nutrient dynamics and biogeochemical process of the Arctic ocean.

关键词： Nitrogen deficit Biological pump Nutrient Sinking particles Arctic ocean

Incremental 4D-VAR assimilation scheme based on Lorenz model

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Acta oceanologica Sinica 2008年第Z1期27卷 93-100页

作者： WANG Xidong XU Dongfeng XU Xiaohua state key laboratory of satellite ocean environment dynamics Second Institute of Oceanography State Oceanic Administra-tion Hangzhou 310012China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography State Oceanic Administra-tion Hangzhou 310012China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography State Oceanic Administra-tion Hangzhou 310012China

Four-dimensional variational(4D-VAR) data assimilation method is a perfect data assimilation solution in theory, but the computational issue is quite difficult in operational *** incremental 4D-VAR assimilation scheme is set up in order to reduce the computational cost. It is shown that the accuracy of the observations, the length of the assimilation window and the choice of the first guess have an important influence on the assimilation outcome through the contrast experiment. Compared with the standard 4D-VAR assimilation scheme, the incremental 4D-VAR assimilation scheme shows its advantage in the computation speed through an assimilation experiment.

关键词： 4D-VAR assimilation,incremental 4D-VAR assimilation Lorenz model

Variations of temperature, salinity and current in the southern tidal passage of the Hangzhou Bay, China

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Acta oceanologica Sinica 2016年第3期35卷 30-37页

作者： HE Zhiguo HUANGFU Kailong YUAN Yeping SONG Dan LI Li ocean College Zhejiang University state key laboratory of satellite ocean environment dynamics Second Institute of OceanographyState Oceanic Administration

Field surveys covering a spring-neap tidal period were conducted to investigate the characteristics of tidal dynamics within a curved channel in the southern Hangzhou Bay, China. The channel has a maximum depth of more than 100 m with an average tidal range of 2.5 m, serving as the main tidal passage in the southern part of the Hangzhou Bay. Water salinity, temperature and velocity data were collected from the ship-based transects and mooring measurements. During flood tide, the tidal current intrudes into the Hangzhou Bay through the northern side of the channel with a maximum velocity of about 2 m/s, while retreats through the southern side during ebb tide with a maximum velocity of 1.8 m/s. Due to the pressure, density gradients, the Coriolis force and centrifugal effect, a lateral exchange flow is generated as the tidal current relaxes from flood to ebb. Salinity and temperature data show that the water in the channel is weakly stratified during both spring and neap tides in summer ***, mixing in the middle region will be enhanced by the lateral circulation. Mooring data indicate that the temperature and salinity are varying at a frequency similar to tidal current but higher than sea level *** results support the hypothesis that the high frequency salinity and temperature variations could be generated by combination of the tidal current and the lateral exchanging flow.

关键词： macro-tidal estuary mooring observations temperature and salinity variations tidal current curved channel

A numerical study on the effect of tidal flat's slope on tidal dynamics in the Xiangshan Bay, China

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Acta oceanologica Sinica 2018年第9期37卷 29-40页

作者： LI Li YE Taoyan HE Zhiguo XIA Yuezhang ocean College Zhejiang University state key laboratory of satellite ocean environment dynamics Second Institute of OceanographyState Oceanic Administration

The Xiangshan Bay is a semi-enclosed and narrow bay, which is characterized by large scale tidal flats and has been historically utilized through coastal construction and aquaculture engineering. The hydrodynamic model using the Finite Volume Coastal ocean Model（FVCOM） was constructed to examine the changes of tidal dynamics due to the variation of tidal flat slopes. According to the model results, a decreased slope of a tidal flat would amplify the M2 tidal amplitude and delay the M2 tidal phase in the inner harbor, due to an increased tidal prism, and vice versa. The amplitude of the main shallow-water tide M4 would be amplified/dampened in the entire bay due to the changed bottom friction, if the tidal flat＇s slope were reduced/increased at the Tie inlet. The phase was advanced. The change of a tidal flat＇s slope at the Tie inlet had greater impacts on tidal amplitude,phase and duration asymmetry, than that at the Xihu inlet. The impact of changes of the tidal flat slope at the Xihu inlet was small and was constrained locally. Changes in the tidal flats＇ slopes at the Tie and Xihu inlets changed the tidal duration asymmetry, residual current and tidal energy via modulating tides. The ebb dominance decreased when the tidal flat＇s slope at the Tie inlet was changed. Decreased/increased ebb dominance occurred when the tidal flat＇s slope was reduced/increased at the Xihu inlet. The residual current and tidal energy density was amplified/dampened and more/less tidal energy was dissipated, with reduced/increased slope at both of the inlets. The findings in this study are instructive to coastal engineering and estuarine management.

关键词： tidal flat's slope tidal dynamics tidal asymmetry tidal energy Xiangshan Bay

Effects of Sea-Surface Waves and ocean Spray on Air-Sea Momentum Fluxes

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Advances in Atmospheric Sciences 2018年第4期35卷 469-478页

作者： Ting ZHANG Jinbao SONG ocean College Zhejiang University state key laboratory of satellite ocean environment dynamics Second Institute of OceanographyState Oceanic Administration

The effects of sea-surface waves and ocean spray on the marine atmospheric boundary layer （MABL） at different wind speeds and wave ages were investigated. An MABL model was developed that introduces a wave-induced component and spray force to the total surface stress. The theoretical model solution was determined assuming the eddy viscosity coefficient varied linearly with height above the sea surface. The wave-induced component was evaluated using a directional wave spectrum and growth rate. Spray force was described using interactions between ocean-spray droplets and wind-velocity shear. Wind profiles and sea-surface drag coefficients were calculated for low to high wind speeds for wind-generated sea at different wave ages to examine surface-wave and ocean-spray effects on MABL momentum distribution. The theoretical solutions were compared with model solutions neglecting wave-induced stress and/or spray stress. Surface waves strongly affected near-surface wind profiles and sea-surface drag coefficients at low to moderate wind speeds. Drag coefficients and near-surface wind speeds were lower for young than for old waves. At high wind speeds, ocean-spray droplets produced by wind-tearing breaking-wave crests affected the MABL strongly in comparison with surface waves, implying that wave age affects the MABL only negligibly. Low drag coefficients at high wind caused by ocean-spray production increased turbulent stress in the sea-spray generation layer, accelerating near-sea-surface wind. Comparing the analytical drag coefficient values with laboratory measurements and field observations indicated that surface waves and ocean spray significantly affect the MABL at different wind speeds and wave ages.

关键词： drag coefficient marine atmospheric boundary layer ocean spray droplets surface waves