The proportions and variations of the light absorption coefficients of major ocean color components in the East China Sea

Sea surface salinity (SSS) is an important tracer for monitoring the Changjiang Diluted Water (CDW) extension into Korean coastal regions; however, observing the SSS distribution in near real time is a difficult task. In this study, SSS detection algorithm was developed based on the ocean color measurements by Geostationary Ocean Color Imager (GOCI) in high spatial and temporal resolution using multilayer perceptron neural network (MPNN). Among the various combinations of input parameters, combinations with three to six bands of GOCI remote sensing reflectance (Rrs), sea surface temperature (SST), longitude, and latitude were most appropriate for estimating the SSS. According to model validations with the Soil Moisture Active Passive (SMAP) and Ieodo Ocean Research Station (I-ORS) SSS measurements, the coefficient of determination (R2) were 0.81 and 0.92 and the root mean square errors (RMSEs) were 1.30 psu and 0.30 psu, respectively. In addition, a sensitivity analysis revealed the importance of SST and the red-wavelength spectral signal for estimating the SSS. Finally, hourly estimated SSS images were used to illustrate the hourly CDW distribution. With the model developed in this study, the near real-time SSS distribution in the East China Sea (ECS) can be monitored using GOCI and SST data.

Download Full-text

A research on statistical retrieval algorithms and spectral characteristics of the total absorption coefficients in the Yellow Sea and the East China Sea

Chinese Journal of Oceanology and Limnology ◽

10.1007/bf02842622 ◽

2006 ◽

Vol 24 (3) ◽

pp. 236-242 ◽

Cited By ~ 1

Author(s):

Wang Xiaomei ◽

Tang Junwu ◽

Song Qingjun ◽

Ding Jing ◽

Ma Chaofei

Keyword(s):

East China Sea ◽

Yellow Sea ◽

Spectral Characteristics ◽

The Yellow Sea ◽

East China ◽

Total Absorption ◽

The East China Sea ◽

Absorption Coefficients ◽

China Sea ◽

Retrieval Algorithms

Download Full-text

Influence of the Changjiang River on the light absorption properties of phytoplankton from the East China Sea

Biogeosciences ◽

10.5194/bg-11-1759-2014 ◽

2014 ◽

Vol 11 (7) ◽

pp. 1759-1773 ◽

Cited By ~ 21

Author(s):

S. Q. Wang ◽

J. Ishizaka ◽

H. Yamaguchi ◽

S. C. Tripathy ◽

M. Hayashi ◽

...

Keyword(s):

Chlorophyll A ◽

East China Sea ◽

Light Absorption ◽

Size Fraction ◽

East China ◽

The East China Sea ◽

Absorption Properties ◽

China Sea ◽

Fraction Versus ◽

Phytoplankton Size

Abstract. Phytoplankton light absorption properties were investigated at the surface and subsurface chlorophyll a maximum (SCM) layer in the East China Sea (ECS), a marginal sea which is strongly influenced by the Changjiang discharge in summer. Results from ECS were compared with those from the Tsushima Strait (TS) where the influence of Changjiang discharge is less. The probable controlling factors, packaging effect (cell size) and pigment composition of total chlorophyll a (Tchl a)-specific absorption coefficient (aph&ast;(λ)) were examined by the corresponding measurements of pigments identified by high-performance liquid chromatography. We observed distinct phytoplankton size structure and thereby absorption properties between ECS and TS. At the surface, mixed populations of micro-, nano- and pico-phytoplankton were recorded in ECS while pico-phytoplankton dominated in TS, generating a lower average aph&ast;(λ) in ECS than in TS. Within SCM, average aph&ast;(λ) was higher in ECS than in TS because of the dominance of nano- and micro-phytoplankton in ECS and TS, respectively. By pooling surface and SCM samples, we found regular trends in phytoplankton size-fraction versus Tchl a; and correlations between aph&ast;(λ) and Tchl a consistent with previous observations for the global ocean in TS but not in ECS. In ECS phytoplankton size-fraction was not correlated with Tchl a, which consequently caused poor relationships between aph&ast;(λ) and Tchl a. The abnormal values mainly originated from the surface low-salinity waters and SCM waters beneath them. At high Tchl a, aph&ast;(λ) of these samples was substantially higher compared to the values in TS and from the global regressions, which was attributable to the lower micro-phytoplankton fraction, and higher nano- and/or pico-phytoplankton fractions in ECS. These observations indicated that the distinct light absorption properties of phytoplankton in ECS were possibly influenced by the Changjiang discharge. Our findings imply that general bio-optical algorithms proposed based on the correlations between aph&ast;(λ) and Tchl a or the patterns in size-fraction versus Tchl a are not applicable in ECS, and need to be carefully considered when using these general algorithms in river-influenced regions.

Download Full-text

The Applicability of the Geostationary Ocean Color Imager to the Mapping of Sea Surface Salinity in the East China Sea

Remote Sensing ◽

10.3390/rs13142676 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2676

Author(s):

Jong-Kuk Choi ◽

Young-Baek Son ◽

Myung-Sook Park ◽

Deuk-Jae Hwang ◽

Jae-Hyun Ahn ◽

...

Keyword(s):

East China Sea ◽

Ocean Color ◽

Sea Surface ◽

Sea Surface Salinity ◽

East China ◽

Red Tides ◽

The East China Sea ◽

Surface Salinity ◽

China Sea

During the summer season, low-salinity water (LSW) inputs from the Changjiang River are observed as filamentous or lens-like features in the East China Sea. Sea surface salinity (SSS) is an important factor in ocean science, and is used to estimate oceanic carbon fluxes, trace red tides, and calculate other physical processes at the surface. In this study, a proxy was developed using remote sensing reflectance (Rrs) from the Geostationary Ocean Color Imager (GOCI) centered at 490 nm (band 3), 555 nm (band 4), 660 nm (band 5), and 680 nm (band 6), and salinity (data from summer cruises during the period of 2011–2016). It was then validated to map LSW plumes in the East China Sea. The GOCI-derived surface salinity was determined by the empirical relationships between Rrs at the four bands and in situ wave glider SSS data (August 2016), and was validated with synchronous in situ hydrographic SSS data (August 2011, 2012, 2013, and 2016). The GOCI-derived SSS was considered reliable in terms of the validation with the in situ measurement with a high coefficient of determination along with a low RMSE (R2 = 0.803, RMSE = 0.914, N = 21), and in comparisons with two previous models that were used to derive SSS in the East China Sea. The GOCI-derived SSS was successfully used to examine time-series variations on diurnal and daily scales, and the effects of a typhoon in terms of marine physical and biological properties in combination with the chlorophyll-a concentration and sea surface temperature.

Download Full-text