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The state-of-the-art OpenFOAM technology is used to develop a numerical model that can be devoted to numerically investigating wake-collapse internal waves generated by a submerged moving body. The model incorporates body geometry, propeller forcing, and stratification magnitude of seawater. The generation mechanism and wave properties are discussed based on model results. It was found that the generation of the wave and its properties depend greatly on the body speed. Only when that speed exceeds some critical value, between 1.5 and 4.5 m/s, can the moving body generate wake-collapse internal waves, and with increases of this speed, the time of generation advances and wave amplitude increases. The generated wake-collapse internal waves are confirmed to have characteristics of the second baroclinic mode. As the body speed increases, wave amplitude and length increase and its waveform tends to take on a regular sinusoidal shape. For three linearly temperature-stratified profiles examined, the weaker the stratification, the stronger the wake-collapse internal wave.

To acquire high-quality operational data products for Chinese in-orbit and scheduled ocean color sensors, the performances of two operational atmospheric correction (AC) algorithms (ESA MEGS 7.4.1 and NASA SeaDAS 6.1) were evaluated over the East China Seas (ECS) using MERIS data. The spectral remote sensing reflectance R rs(λ), aerosol optical thickness (AOT), and Angstrom exponent (α) retrieved using the two algorithms were validated using in situ measurements obtained between May 2002 and October 2009. Match-ups of R rs, AOT, and α between the in situ and MERIS data were obtained through strict exclusion criteria. Statistical analysis of R rs(λ) showed a mean percentage difference (MPD) of 9%–13% in the 490–560 nm spectral range, and significant overestimation was observed at 413 nm (MPD>72%). The AOTs were overestimated (MPD>32%), and although the ESA algorithm outperformed the NASA algorithm in the blue-green bands, the situation was reversed in the red-near-infrared bands. The value of α was obviously underestimated by the ESA algorithm (MPD=41%) but not by the NASA algorithm (MPD=35%). To clarify why the NASA algorithm performed better in the retrieval of α, scatter plots of the α single scattering albedo (SSA) density were prepared. These α-SSA density scatter plots showed that the applicability of the aerosol models used by the NASA algorithm over the ECS is better than that used by the ESA algorithm, although neither aerosol model is suitable for the ECS region. The results of this study provide a reference to both data users and data agencies regarding the use of operational data products and the investigation into the improvement of current AC schemes over the ECS.

The SMOS (soil moisture and ocean salinity) mission undertaken by the European Space Agency (ESA) has provided sea surface salinity (SSS) measurements at global scale since 2009. Validation of SSS values retrieved from SMOS data has been done globally and regionally. However, the accuracy of SSS measurements by SMOS in the China seas has not been examined in detail. In this study, we compared retrieved SSS values from SMOS data with in situ measurements from a South China Sea (SCS) expedition during autumn 2011. The comparison shows that the retrieved SSS values using ascending pass data have much better agreement with in situ measurements than the result derived from descending pass data. Accuracy in terms of bias and root mean square error (RMS) of the SSS retrieved using three different sea surface roughness models is very consistent, regardless of ascending or descending orbits. When ascending and descending measurements are combined for comparison, the retrieved SSS using a semi-empirical model shows the best agreement with in situ measurements, with bias -0.33 practical salinity units and RMS 0.74. We also investigated the impact of environmental conditions of sea surface wind and sea surface temperature on accuracy of the retrieved SSS. The SCS is a semi-closed basin where radio frequencies transmitted from the mainland strongly interfere with SMOS measurements. Therefore, accuracy of retrieved SSS shows a relationship with distance between the validation sites and land.

The semi-closed Rushan Bay is one of the largest aquaculture bases in North China, with its only navigation channel connecting the Rushan harbour and the Yellow Sea. Recent economic growth with increased import and export demands have stimulated a dredging operation, starting on 26 March 2010, which was paused on 17 June 2010 after numerous reports of mortality of cultured shellfish, such as clam (Ruditapes philippinarum), among other precious marine animals. A lawsuit was filed to settle the dispute between the dredging company and an aquaculture company, yet there was endless debate on whether the mortality was caused by the dredging operations. Here, using multi-sensor remote-sensing data collected by Landsat/ETM+, HJ-1A&1 B/CCD, and Aqua & Terra/MODIS, we addressed the two critical questions of (1) whether there was a significant increase in the suspended particulate matter (SPM) in the aquaculture area during and after the dredging operations; and (2) if the answer is yes, whether such an increase wa...

Optical models for the retrieval of shallow water bottom depth and albedo using multispectral data usually require in situ water depth data to tune the model parameters. In the South China Sea (SCS), however, such in situ data are often lacking or obsolete (perhaps from half a century ago) for most coastal waters around its islands and reefs. Here, we combine multispectral data collected by MODIS and Landsat to estimate bottom depth and albedo for four coral reef regions in the SCS, with results partially validated by some scarce in situ data. The waters in these remote regions are oligotrophic whose optical properties can be well derived from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements when the waters are optically deep. The MODIS-derived optical properties are used to estimate the water column attenuation to the Landsat measurements over shallow waters, thus eliminating the requirement of model tuning using field measured water depths. The model is applied to four Landsat Thematic...

An optical closure study on bio-optical relationships was carried out using radiative transfer model matrix operator method developed by Freie Universitat Berlin. As a case study, the optical closure of bio-optical relationships empirically parameterized with in situ data for the East China Sea was examined. Remote-sensing reflectance (Rrs) was computed from the inherent optical properties predicted by these biooptical relationships and compared with published in situ data. It was found that the simulated Rrs was overestimated for turbid water. To achieve optical closure, bio-optical relationships for absorption and scattering coefficients for suspended particulate matter were adjusted. Furthermore, the results show that the Fournier and Forand phase functions obtained from the adjusted relationships perform better than the Petzold phase function. Therefore, before bio-optical relationships are used for a local sea area, the optical closure should be examined.

Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar (SAR) image of waves. Based on the general dispersion relation of ocean waves, the wavelength changes of a surface wave over varying water depths can be derived from SAR. Approaching the analysis of SAR images of waves and using the general dispersion relation of ocean waves, this indirect technique of remote sensing bathymetry has been applied to a coastal region of Xiapu in Fujian Province, China. Results show that this technique is suitable for the coastal waters especially for the near-shore regions with variable water depths.

Previous studies of the Mediterranean Sea outflow and meddies (O&M) were limited by the poor spatial and temporal resolution of conventional in situ observations as well as the confinement of satellite observations to the ocean’s surface. Accordingly, little is known about the formation and transport of meddies and the spatial and temporal variation of O&M trajectories, which are located, on average, at a depth of 1000 m. However, a new remote sensing method has been developed by the authors to observe and study the O&M through unique approaches in satellite multisensor data integration analyses. Satellite altimeter, scatterometer, infrared satellite imagery, and XBT data were used to detect and calculate the trajectories and the relative transport of the O&M (January 1993–December 2002). Two experiments [covering 1993–95: A Mediterranean Undercurrent Seeding Experiment (AMUSE) and Structures des Echanges Mer–Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale (SEMAPHORE)] and XBT temperature measurements were used to directly validate the method presented herein. The monthly mean features derived from floats and XBTs for multiple meddies and the results of the presented method were significantly correlated based on a statistical chi-square test. In addition, the complex singular value decomposition method was used to identify the propagating features and their phase speeds. It was found that saltier water from the Mediterranean Sea was transported into the North Atlantic Ocean over the Strait of Gibraltar in boreal spring and summer relative to boreal autumn and winter. Streamfunctions using altimetry, and time–frequency energy distributions using the Hilbert–Huang transform, were computed to evaluate the meddy interactions with the sea surface variation. Since the O&M play a significant role in carrying salty water from the Mediterranean Sea into the Atlantic, such new knowledge about their trajectories, transport, and life histories is important to the understanding of their mixing and interaction with North Atlantic water. This may lead to a better understanding of the global ocean circulation and global climate change.

[1] A massive bloom of the green macroalgae Ulva prolifera (previously known as Enteromorpha prolifera) occurred in June 2008 in the Yellow Sea (YS), resulting in perhaps the largest “green tide” event in history. Using a novel index (Floating Algae Index) and multiresolution remote sensing data from MODIS and Landsat, we show that U. prolifera patches appeared nearly every year between April and July 2000–2009 in the YS and/or East China Sea (ECS), which all originated from the nearshore Subei Bank. A finite volume numerical circulation model, driven by realistic forcing and boundary conditions, confirmed this finding. Analysis of meteorological/environmental data and information related to local aquaculture activities strongly supports the hypothesis that the recurrent U. prolifera in the YS and ECS resulted from aquaculture of the seaweed Porphyra yezoensis (or nori) conducted along the 200 km shoreline of the Subei Bank north of the Changjiang (Yangtze) River mouth. Given the continuous growth in aquaculture efforts in the region, similar macroalgae bloom events, such as the summer 2008 event, are likely to occur in the future, particularly between May and July. This was confirmed by the 2009 bloom event in the same regions and the same period. The profit of the local P. yezoensis aquaculture industry (∼16,000 Ha in 2007) is estimated as U.S. $53 million, yet the cost to manage the impact of the summer 2008 U. prolifera bloom exceeded U.S. $100 million. Therefore, better strategies are required to balance the economic benefit of seaweed aquaculture and the costs of environmental impacts.

[1] The heat storage anomaly of the upper ocean can be estimated using altimeter data, based on the thermal dynamics equation. In this study, we analyzed both nonthermal and thermal steric height measured by altimetry, and removed nonthermal steric height from altimeter measurements to calculate the heat storage anomaly from thermal steric height alone in the global oceans, but with a focus on the Pacific Ocean. After examining nonthermal steric height (salinity, waves, and wind), we believe that wind stress is a major component to the change in sea surface height. Blended TOPEX/Poseidon and ERS-1/2 altimeter 1° × 1° sea surface height anomaly from January 1993 to October 2000 were used to calculation of the heat storage anomaly. In addition, we used expendable bathythermograph (XBT) data to the global oceans to determine a reference heat storage, from which the altimeter estimation of the heat storage was compared. The wind stress curls, from scatterometer data obtained from January 1993 to October 2000, were used for analyzing the wind effects on sea surface height variation. The correlation coefficients between heat storage from altimeter data (HAlt′) and that from the XBT (HXBT′) are larger than 0.6 in the global oceans, except in the regions of 20°N in the eastern Pacific, the eastern tropical Pacific, the tropical Atlantic, and the western tropical Indian Ocean. The root mean square (RMS) of the differences (HAlt′ − HXBT′) has large values in the Gulf Stream and the Kuroshio Extension regions as well as the eastern and western tropical Pacific, and eastern Indian Ocean. The wind-induced sea surface height variation exhibits strong annual and interannual cycles, so the empirical orthogonal function (EOF) method was employed to extract the cycles. The annual cycle has two modes, whereas the interannual cycle is characterized by El Nino events. Wind stress can affect the estimation of the heat storage through mechanisms derived from quasi-geostrophic and barotropic theory. We calculated the correlation coefficient between the differences (HAlt′ − HXBT′) and wind stress curl. The result shows that El Nino Southern Oscillation (ENSO) related wind stress curl anomalies are responsible for estimating discrepancy in the regions west of South and North America and tropical oceans. The high correlation suggests that in these regions the barotropic and linear theory is the dynamic mechanism underlying the wind effects on heat storage estimation. Furthermore, we focus on baroclinic signal in sea level resulting from Ekman upwelling in the tropical oceans. The effect of wind-forcing has the most important role in sea level change during the 1997–1998 El Nino event. For instance, the heat storage anomaly (Q′) due to the strong coastal upwelling off the west coast of Peru closely relates to sea surface temperature (SST), wind-forcing, remnant sea level height anomaly (Δη′) after removing the contributions of the heat, salt, and waves to the sea level height, and Ekman depth (DEK). However, the Q′ in the west coast of America and western Pacific warm pool areas did not closely relate to SST, wind-forcing, Δη′, and DEK.

[1] A frontal feature visible on a synthetic aperture radar (SAR) image acquired by the Radarsat satellite over the East China Sea on 19 November 2000 is analyzed in conjunction with data acquired by Quikscat, TOPEX/Poseidon, Tropical Rain Measurement Mission (TRMM), Defense Meteorological Satellite Program (DMSP), and National Oceanic and Atmospheric Administration (NOAA) satellites, and with data obtained from ship measurements. Although this frontal feature is located close to the Kuroshio front, it is demonstrated that it is not a sea surface manifestation of an oceanic front, but rather of an atmospheric front extending over 800 km from an area of the Pacific Ocean northeast of Taiwan to the southern coast of Korea. It is a cold front moving in the southeast direction with a speed of approximately 45–50 km/hour and associated with a 40-km-wide rainband trailing the front. The Radarsat image, which has a resolution of 50 m, reveals fine-scale structures of the atmospheric front, in particular small-scale convective rain cells embedded in the front. Conclusion is drawn that accurate interpretation of frontal features in SAR images requires use of additional meteorological and remote sensing data and information.

[1] Sea-viewing Wide Field-of-view Sensor observation of the east Asian seas during the March–April 2001 Aerosol Characterization Experiment-Asia shows large areas of underestimated or even negative water-leaving radiance in the blue. To investigate the cause of the problem, three cloud-free matchup stations around Japan were analyzed, where in situ measurements were made onboard R/V Ronald H. Brown at the time of satellite overpass. Using an optimization method, information on the possible composition of aerosols was obtained from sky radiance data collected onboard the ship. An iterative radiative transfer simulation was carried out in an attempt to reproduce the satellite-measured top-of-atmosphere reflectance. The resulting water reflectance and aerosol optical thickness (AOT) agreed well with in situ measurements when the effect of submicron absorbing particles was considered in the radiative transfer simulation. The error in the retrieved water reflectance was much decreased, with average values of about 6% at 412 and 443 nm for the three stations. The effect of the Asian dust was also simulated in comparison with that of small absorptive aerosols. The underestimation could not be solely attributed to Asian dust. It was also found that at one of the stations, where the presence of dust aerosols was anticipated, an aerosol model mixed with both dust and soot improved the accuracy of the estimated AOT compared with the case of soot as the only absorptive aerosol (error of 13% at 865 nm instead of 44%). Submicron absorbing particles, in addition of the Asian dust, should be considered in the optical remote sensing of east Asian waters.

[1] The equilibrium Bowen ratio (Bo*) can be estimated empirically from the sea surface temperature (SST) only when the air is saturated with water vapor at the sea surface. However, since most of the sea surface is not saturated with water vapor, several studies have been conducted for the empirical Bowen ratio (BoE = Bo*(SST)), which was formulated with many sources of data from many areas. Hicks and Hess' [1977] linear regression formula for the BoE as a function of SST alone was used to estimate the empirical Bowen ratio in the tropical Pacific. Climatological and long-term time series Optimum Interpolation Sea Surface Temperature (OISST) data was used for the climatological study of the BoE. The climatological mean Bowen ratio showed the regions, where the latent heat flux was most dominant. The Bowen ratio in the western Pacific warm pool (WPWP) area (O (0.04)) was 10% smaller than those in the upwelling coastal areas (O (0.14)). Along 5°N and 5°S, a 0.7 correlation coefficient between the BoE and the bulk formulated Bowen ratio (BoB), using climatological data, was found in the weak wind zone of the doldrums. BoB is the ratio of the bulk formulated sensible heat flux to the bulk formulated latent heat flux. EOF analysis was used to find out dominant temporal and spatial signals of the BoE. The first temporal EOF of the BoE, using 156 months (1986–1999) of OISST anomaly was related to El Nino events with an approximate 12-month lag when compared to the El Nino-Southern Oscillation (ENSO) index (SOI). The second and third temporal EOF showed annual and interannual signals, respectively. In order to estimate the discrepancy between the BoE and the BoB and to correct for the wind effect and the humidity effect, long-term time series of Tropical Atmosphere Ocean (TAO) data was used. Our results showed that the eastern Pacific demonstrated a stronger correlation between the BoB and the BoE than the western Pacific. However, the Bowen ratio differences (BoD = |BoE − BoB|) were small in the western Pacific, and a larger margin of error was found at the eastern Pacific, where ocean dynamics perturb the upper ocean heat balance. The sensitivity of the humidity and the winds on the BoE was tested using linear correlation of the BoD while varying the winds and humidity. The BoD was small, especially in the southwest Pacific, where there are weak winds and high levels of the humidity. Thus the BoE in our study will be more useful to study involving heat fluxes in the WPWP area rather than those in the eastern Pacific. The correction of the humidity and the wind was applied using a linear regression of the humidity and the winds. After the corrections, the BoD was reduced by an average of 70.2%. Using TAO data, we obtained BoE = 0.033Bo* in the western Pacific with Bo*'s standard deviation of 0.008 at sea surface temperature 29.27°C ± 0.54°C.

Extensive patches of floating algae have appeared since mid-June in coastal waters off Qingdao, China, where the Olympic sailing competitions will be held on 9–23 August. By 27 June, field surveys showed that the patches occupied about 30%, or 15 square kilometers, of the 50-square-kilometer region designated for the competitions, posing potential problems for them, according to reports in local news media. The floating algae, whose spatial extent is the largest ever reported in the literature for the world's oceans (as revealed by satellite estimates indicated below), have attracted wide national and international attention since late June.