Impacts of Insufficient Observations on the Monitoring of Short- and Long-Term Suspended Solids Variations in Highly Dynamic Waters, and Implications for an Optimal Observation Strategy
Zhou, Q; Tian, LQ; Wai, OWH; Li, J; Sun, ZH; Li, WK; quzhou@whu.edu.cn; tianliqiao@whu.edu.cn; onyx.wai@polyu.edu.hk; lijian@whu.edu.cn; Joeysun@scsio.ac.cn; lwk1542@hotmail.com
2018
发表期刊REMOTE SENSING
卷号10期号:2页码:-345
摘要Coastal water regions represent some of the most fragile ecosystems, exposed to both climate change and human activities. While remote sensing provides unprecedented amounts of data for water quality monitoring on regional to global scales, the performance of satellite observations is frequently impeded by revisiting intervals and unfavorable conditions, such as cloud coverage and sun glint. Therefore, it is crucial to evaluate the impacts of varied sampling strategies (time and frequency) and insufficient observations on the monitoring of short-term and long-term tendencies of water quality parameters, such as suspended solids (SS), in highly dynamic coastal waters. Taking advantage of the first high-frequency in situ SS dataset (at 30 min sampling intervals from 2007 to 2008), collected in Deep Bay, China, this paper presents a quantitative analysis of the influences of sampling strategies on the monitoring of SS, in terms of sampling frequency and time of day. Dramatic variations of SS were observed, with standard deviation coefficients of 48.9% and 54.1%, at two fixed stations; in addition, significant uncertainties were revealed, with the average absolute percent difference of approximately 13%, related to sampling frequency and time, using nonlinear optimization and random simulation methods. For a sampling frequency of less than two observations per day, the relative error of SS was higher than 50%, and stabilized at approximately 10%, when at least four or five samplings were conducted per day. The optimal recommended sampling times for SS were at around 9:00, 12:00, 14:00, and 16:00 in Deep Bay. The pseudo MODIS SS dataset was obtained from high-frequency in situ SS measurements at 10:30 and 14:00, masked by the temporal gap distribution of MODIS coverage to avoid uncertainties propagated from atmospheric correction and SS models. Noteworthy uncertainties of daily observations from the Terra/Aqua MODIS were found, with mean relative errors of 19.2% and 17.8%, respectively, whereas at the monthly level, the mean relative error of Terra/Aqua MODIS observations was approximately 10.7% (standard deviation of 8.4%). Sensitivity analysis between MODIS coverage and SS relative errors indicated that temporal coverage (the percentage of valid MODIS observations for a month) of more than 70% is required to obtain high-precision SS measurements at a 5% error level. Furthermore, approximately 20% of relative errors were found with the coverage of 30%, which was the average coverage of satellite observations over global coastal waters. These results highlight the need for high-frequency measurements of geostationary satellites like GOCI and multi-source ocean color sensors to capture the dynamic process of coastal waters in both the short and long term.
部门归属[Zhou, Qu; Li, Jian] Wuhan Univ, Sch Remote Sensing & Informat Engn, Wuhan 430079, Hubei, Peoples R China; [Zhou, Qu; Tian, Liqiao; Li, Wenkai] Wuhan Univ, State Key Lab Informat Engn Surveying Mapping & R, Wuhan 430079, Hubei, Peoples R China; [Wai, Onyx W. H.] Hong Kong Polytech Univ, Dept Civil & Environm Engn, Kowloon, Hong Kong, Peoples R China; [Sun, Zhaohua] Chinese Acad Sci, South China Sea Inst Oceanol, State Key Lab Trop Oceanog, Guangzhou 510301, Guangdong, Peoples R China
关键词Coastal Waters Suspended Solids Remote Sensing Sampling Strategy High Frequency
学科领域Remote Sensing
资助项目LTO
文献类型期刊论文
条目标识符http://ir.scsio.ac.cn/handle/344004/17099
专题热带海洋环境国家重点实验室(LTO)
通讯作者quzhou@whu.edu.cn; tianliqiao@whu.edu.cn; onyx.wai@polyu.edu.hk; lijian@whu.edu.cn; Joeysun@scsio.ac.cn; lwk1542@hotmail.com
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Zhou, Q,Tian, LQ,Wai, OWH,et al. Impacts of Insufficient Observations on the Monitoring of Short- and Long-Term Suspended Solids Variations in Highly Dynamic Waters, and Implications for an Optimal Observation Strategy[J]. REMOTE SENSING,2018,10(2):-345.
APA Zhou, Q.,Tian, LQ.,Wai, OWH.,Li, J.,Sun, ZH.,...&lwk1542@hotmail.com.(2018).Impacts of Insufficient Observations on the Monitoring of Short- and Long-Term Suspended Solids Variations in Highly Dynamic Waters, and Implications for an Optimal Observation Strategy.REMOTE SENSING,10(2),-345.
MLA Zhou, Q,et al."Impacts of Insufficient Observations on the Monitoring of Short- and Long-Term Suspended Solids Variations in Highly Dynamic Waters, and Implications for an Optimal Observation Strategy".REMOTE SENSING 10.2(2018):-345.
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