Journal of Tropical Oceanography ›› 2018, Vol. 37 ›› Issue (3): 35-44.doi: 10.11978/2017067CSTR: 32234.14.2017067

Special Issue: 南海专题

• Orginal Article • Previous Articles     Next Articles

The spectral characteristics of phytoplankton absorption coefficient and assessment of MODIS-Aqua products in typical sea areas of the South China Sea

Wenjing ZHAO1(), Wenxi CAO2(), shuibo HU3, Guifen WANG2, Zhenyu LIU4, Min XU1   

  1. 1. South China Institute of Environmental Sciences, the Ministry of Environmental Protection of RPC, Guangzhou 510535, China
    2. State Key Laboratory of Tropical Oceanography (South China Sea Institute of Oceanology, Chinese Academy of Sciences), Guangzhou 510301, China
    3. Shenzhen Key Laboratory of Spatial Information Smart Sensing and Services and Key Laboratory for Geo-Environment Monitoring of Coastal Zone of the National Administration of Surveying, Mapping and Geo-Information, Shenzhen University, Shenzhen 518060, China
    4. College of Resources and Environmental Science, South-central University for Nationalities, Wuhan 430074, China;
  • Received:2017-06-08 Revised:2017-08-15 Online:2018-06-10 Published:2018-05-03
  • Supported by:
    National Natural Science Foundation of China (41506202);Natural Science Foundation of Guangdong Province (2014A030310287);State Key Laboratory of Tropical Oceanography Under Independent Project (LTO1509);Project of Basic Scientific Research Expenses Supported by the Central Public Welfare Research Institute (South China Institute of Environmental Sciences, Ministry of Environmental Protection, PM-zx703-201601-014);Ministry of Environmental Protection department budget Project (The policy research of coastal areas pollution prevention and control technology);Science and Technology Planning Project of Guangxi (AB16380339);Natural Science Foundation of Hubei Province (BZY15028)

Abstract:

Using remote sensing to accurately estimate phytoplankton absorption coefficient aph(l) can provide basic data and useful method to distinguish different functions of phytoplankton species for long time and large spatial scale. In this paper, the characteristics of aph(l) spectral are compared and analyzed in four typical areas of the South China Sea (SCS), east area of Qiongdong (QD), Guangdong Coastal area (GD), and the Pearl River Estuary (PE) by using field data collected during2003-2012.Then, the phytoplankton population structure differences are preliminarily identified. Furthermore, the performances of MODIS-Aqua aph(l) products derived from the semi-analytical algorithm QAA and empirical algorithm PL by using MODIS-Aqua remote sensing reflectance Rrs(l) products are compared in the SCS and QD waters based on the relaxed match-ups between MODIS-Aqua products and field data. The results show the differences of aph(l) spectral features are obvious among the clear water represented by the SCS and QD and turbid waters represented by GD and PE. In the clear waters, the aph(l) value is small but in a dominant position of particle absorption, while in the GD and PE areas, the aph(l) value is relatively large but not in a dominant position. The aph(l) coefficient have obvious spatial differences, and the possible causes are pigment packaging effect and the variation of pigment composition and concentration. MODIS-Aqua aph(l) products derived from the empirical algorithm PL perform better than those from the semi-analytical algorithm QAA. The algorithm QAA-derived aph(l) products underestimate the results compared to the field data, while the algorithm PL overestimate the results, with the average relative error (APD)less than 22% for both algorithms. There is a great improvement in the accuracy of the PL algorithm by using the Chl-a products derived from the optimized algorithm of OCI (named algorithm NOCI), with the APD less than 14%. In summary, there are strong application prospects to discuss different functions of ocean phytoplankton species by using remote sensing products.

Key words: South China Sea, phytoplankton absorption coefficient, spectral characteristics, remote sensing product