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Observation and simulation of the diffuse attenuation coefficient of downwelling irradiance in the Polar Ocean

Science China Earth Sciences 2023年第7期66卷 1535-1546页

作者： Weibo WANG Chunsheng JING Xiaogang GUO Ocean Dynamic Laboratory Third Institute of OceanographyMinistry of Natural ResourcesXiamen 361005China Fujian Provincial Key Laboratory of Marine Physical and Geological Processes Xiamen 361005China

The three-stream radiation transfer model is used to investigate the fluctuation in the underwater diffuse attenuation coefficient of downwelling irradiance in the polar ocean with a high solar zenith angle and different direct radiation ***,the applicability of the three-stream radiation model in the polar region is validated by using 18 in situ observation data from September to October 2009 in the Beaufort *** show that in the absence of sea ice,the average relative errors between the simulation and observation values for 490 nm downwelling irradiance (E_(d)(490)) and its diffuse attenuation coefficient (K_(d)(490)) are 7.04%and 9.88%,*** the stations surrounded by sea ice,the radiation is relatively small due to ice blocking,and the average relative errors simulated by the model reach 15.89%and 15.55%,***,simulations with different chlorophyll concentrations and different proportions of direct radiation reveal that a high solar zenith angle has a greater impact on K_(d)(490) in the surface water.K_(d)(490) is less affected by the light field (affected by the solar zenith angle and the proportion of direct radiation) at depths greater than 30 m,and meets the linear relationship with the inherent optical parameters(the sum of the absorption coefficient and backscattering coefficient).The surface K_(d)(490) is still consistent with that at a depth of more than 50 meters under a high solar zenith angle,implying that the surface K_(d)(490) can also be considered as an inherent optical parameter at a high solar zenith angle (greater than 60 degrees).The relative error of obtaining surface K_(d)(490) by using the linear relationship at the 50 m layer is found to be less than 8%in the seawater with chlorophyll concentration greater than0.05 mg m^(-3).The effect of the solar zenith angle and proportion of direct radiation can be ignored when measuring the diffuse attenuation coefficient in the polar ***,the

关键词： “three-stream”radiation transfer model diffuse attenuation coefficient Solar zenith angle Proportion of direct radiation Polar ocean

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Variation of diffuse attenuation coefficient of downwelling irradiance in the Arctic Ocean

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Acta Oceanologica Sinica 2014年第6期33卷 53-62页

作者： WANG Weibo ZHAO Jinping Key Laboratory of Physical Oceanography Ministry of EducationOcean University of China

The diffuse attenuation coefficient （Kd） for downwelling irradiance is calculated from solar irradiance data measured in the Arctic Ocean during 3rd and 4th Chinese National Arctic Research Expedition （CHINARE）, including 18 stations and nine stations selected for irradiance profiles in seawater respectively. In this study, the variation of attenuation coefficient in the Arctic Ocean was studied, and the following results were obtained. First, the relationship between attenuation coefficient and chlorophyll concentration in the Arctic Ocean has the form of a power function. The best fit is at 443 nm, and its determination coefficient is more than 0.7. With increasing wavelength, the determination coefficient decreases abruptly. At 550 nm, it even reaches a value lower than 0.2. However, the exponent fitted is only half of that adapted in low-latitude ocean because of the lower chlorophyll-specific absorption in the Arctic Ocean. The upshot was that, in the case of the same chlorophyll concentration, the attenuation caused by phytoplankton chlorophyll in the Arctic Ocean is lower than in low-latitude ocean. Second, the spectral model, which exhibits the relationship of attenuation coefficients between 490 nm and other wavelength, was built and provided a new method to estimate the attenuation coefficient at other wavelength, if the attenuation coefficient at 490 nm was known. Third, the impact factors on attenuation coefficient, including sea ice and sea water mass, were discussed. The influence of sea ice on attenuation coefficient is indirect and is determined through the control of enter- ing solar radiation. The linear relationship between averaging sea ice concentration （ASIC, from 158 Julian day to observation day） and the depth of maximum chlorophyll is fitted by a simple linear equation. In addition, the sea water mass, such as the ACW （Alaskan Coastal Water）, directly affects the amount of chlo- rophyll through taking more nutrient, and results in the higher

关键词： diffuse attenuation coefficient Arctic Ocean average sea ice concentration Alaskan Coastal Water

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Seasonal and spatial distributions of euphotic zone and longterm variations in water transparency in a clear oligotrophic Lake Fuxian, China

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Journal of Environmental Sciences 2018年第10期30卷 185-197页

作者： Qichao Zhou Yunlin Zhang Kaidi Li Licheng Huang Fengle Yang Yuanyang Zhou Junjun Chang Taihu Laboratory for Lake Ecosystem Research State Key Laboratory of Lake Science and Environment Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Yunnan Key Laboratory of Pollution Process and Management of Plateau Lake-Watershed Yunnan Institute of Environmental Science(Kunming China International Research Center for Plateau Lake) School of Ecology and Environmental Science Yunnan University

To assess the seasonal and spatial variations and long-term trends in water optical properties in Lake Fuxian, investigations based on field work in four seasons and a long-term analysis of data from 1980 to 2014 were conducted. The results show that there was no significant variation in the euphotic depth（Z（eu）） across the four seasons, and no significant correlations between Z（eu） and potential influencing factors in seasons other than summer, suggesting that the water itself may be a major factor regulating the Z（eu）in general. Nevertheless, significant differences in Z（eu） between the north region（NR） and the south region（SR） were observed in all seasonal tests except spring. This finding relates to a higher abundance of chromophoric dissolved organic matter（CDOM） in the NR due to runoff, especially in the rainy seasons（summer and autumn）.CDOM and its terrigenous component had an important impact on Z（eu）in summer, with the highest precipitation, and impacts from suspended solids and non-algal particles were also found in the NR in summer. The Secchi disk depth in the lake decreased clearly over the years,with significantly negative correlations with the increasing permanganate index and air temperature, implying that organic contaminants（CDOM and/or phytoplankton） are important regulators of water transparency. We estimate that the combined effects of climate warming and changes in land use and land cover are also indirect regulating factors. These findings should be considered in the protection of Lake Fuxian, owing to the importance of light penetration in aquatic ecosystems.

关键词： Photosynthetic active radiation diffuse attenuation coefficient Euphotic depth Secchi disk depth Chromophoric dissolved organic matter Yunnan-Guizhou Plateau

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Characteristics of water masses and bio-optical properties of the Bering Sea shelf during 2007–2009

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Acta Oceanologica Sinica 2022年第10期41卷 140-153页

作者： Yubin Yao Tao Li Xingyuan Zhu Xiaoyu Wang College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao266100China Pilot National Laboratory for Marine Science and Technology(Qingdao) Qingdao266237China Frontier Science Center for Deep Ocean Multispheres and Earth System(FDOMES)and Physical Oceanography Laboratory Ocean University of ChinaQingdao266100China

The hydrographic and bio-optical properties of the Bering Sea shelf were analyzed based on in-situ measurements obtained during four cruises from 2007 to *** to the temperature and salinity of the seawater,the spring water masses on the Bering Sea shelf were classified as the Alaskan Coast Water,Bering Sea Shelf Water,Anadyr Water,Spring Mixed Layer Water,Remnant Winter Water,and Winter Water,each of which had varying chlorophyll a *** them,the highest chlorophyll a concentration occurred in the nutrient-rich Anadyr Water((7.57±6.16)mg/m^(3) in spring).The spectrum-dependent diffuse attenuation coefficient(Kd(λ))of the water column for downwelling irradiance was also calculated,exhibiting a decrease at 412-555 nm and then an increase within the range of 0.17-0.48 m-1in ***,a strong correlation between the chlorophyll a concentration and the attenuation coefficient was found at visible wavelengths on the Bering Sea ***,the chlorophyll a concentration was higher on the northern shelf((5.18±3.78)mg/m^(3))than on the southern shelf((3.64±2.51)mg/m^(3)),which was consistent with the distribution of the attenuation ***,the consumption of nutrients by blooms resulted in minimum chlorophyll a concentration((0.78±0.51)mg/m^(3))and attenuation coefficient values in *** terms of the vertical structure,both the attenuation coefficient and the chlorophyll a concentration tended to reach maximum values at the same depth,and the depth of the maximum values increased as the surface temperature increased in ***,an empirical model was fitted with a power function based on the correlation between the chlorophyll a concentration and the attenuation coefficient at 412-555 *** addition,a spectral model was constructed according to the relationship between the attenuation coefficients at 490 nm and at other wavelengths,which provides a method for estimating the bio-optical properties of the Berin

关键词： diffuse attenuation coefficient water mass Bering Sea shelf chlorophyll a empirical model

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Temporal-spatial variations of euphotic depth of typical lake regions in Lake Taihu and its ecological environmental significance

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Science China Earth Sciences 2006年第4期49卷 431-442页

作者： ZHANG Yunlin1, 2, QIN Boqiang1, HU Weiping1, WANG Sumin1, CHEN Yuwei1 & CHEN Weimin1 1. Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences, Nanjing 210008, China 2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China Nanjing Institute of Geography & Limnology Chinese Academy of Sciences Nanjing China Graduate School of the Chinese Academy of Sciences Beijing China

By using the data of underwater irradiance measured in the different lakeregions of Lake Taihu during 1998—2004 and total suspended solids (TSS), wind speeds of the total13 stations in typical lake regions during 1993—2003, this paper analyzes the factors ofinfluencing on PAR (pho-tosynthetically available radiation) attenuation, euphotic depth, andpresents the temporal and spatial variations of euphotic depth of typical lake regions in LakeTaihu, and the spectral distributions of euphotic depth at station 2. The results show that theconcentration of TSS is the most important factor impacting PAR attenuation, followed by chlorophylla; chromophoric dissolved organic matter (CDOM) has little impact on the PAR euphotic depth. During1993—2003, the mean yearly PAR euphotic depths of the typical lake regions ranged from 1.04 to1.95 m with a mean value of 1.35±0.23 m. The PAR euphotic depth fell into 3 spatial zone types:Type Ⅰ, the lowest, including the lake center and the inflows of rivers; Type Ⅱ, intermediate,including Meiliang Bay, Wulihu Lake and Gonghu Bay; Type Ⅲ, the greatest, including the East LakeTaihu; corresponding mean depths were approximately 1.1, 1.4, 2.0 m, respectively. The seasonalvariations of euphotic depths were not quite the same in different lake regions. In the lake center,the mean values of PAR euphotic depth in summer and autumn were significantly greater than those inwinter and spring; in the Meiliang Bay, winter means were significantly greater than in the otherthree seasons; in the East Lake Taihu, winter means were significantly less than in the other threeseasons. However, no distinct seasonal change was recorded in the Wulihu Lake, Gonghu Bay and theinflows of rivers. The spectral distributions of euphotic depth present a minimal value at the bluelight wave band of 400 nm, and a peak at the green light wave band of around 580 nm. In 1998 and1999, based on the seasonal many-day continuous measurements, the PAR euphotic depths at station 2w

关键词： lake taihu euphotic depth diffuse attenuation coefficient total suspendedsolid ecological

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The vertical attenuation of irradiance as a function of turbidity: a case of the Huanghai (Yellow) Sea in spring

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Acta Oceanologica Sinica 2009年第5期28卷 66-75页

作者： LIN Shaoying ZOU Tao GAO Huiwang GUO Xinyu Key Laboratory of Marine Environment and Ecology Ministry of Education of China Ocean University of China Qingdao 266100 China Center for Marine Environmental Studies Ehime University 2-5 Bunkyo-Cho Matsuyama 790-8577 Japan

The planar photosynthetically available radiation （PAR）, turbidity and concentration of chlorophyll a （chl a）, were measured at 26 stations in the Huanghai （Yellow） Sea during a cruise of China SOLAS from 19 to 27 March 2005. Due to low chl a （〈0.35 mg · m^-3 ） in upper layers （above 5 m）, suspended particulate matter became the major factor that influenced the turbidity in early spring. The calculated vertical diffuse attenuation coefficient of PAR, K PAR , varied with water depths with a maximum value in the upper 5 m layer. The mean K PAR in survey area was 0.277 ± 0.07 m^-1 that is considerably higher than most of the other case 2 waters. Within the survey area, K PAR also showed distinct regional characteristics, corresponding to the distribution of turbidity. Based on measurements, the relationship between K PAR and turbidity as well as chl a was established. It was suggested that suspended particulate matter plays an important role in light attenuation in the Huanghai （Yellow） Sea in spring.

关键词： Photosynthetically available radiation diffuse attenuation coefficient Turbidity Chlorophyll a the Huanghai (Yellow) Sea

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