AUTHOR=Cui He , Chen Jianyu , Jiang Xiaoyi , Fu Yu , Qiao Feng 

TITLE=A novel quantitative analysis for diurnal dynamics of Ulva prolifera patch in the Yellow Sea from Geostationary Ocean Color Imager observation

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1177997

DOI=10.3389/fmars.2023.1177997

ISSN=2296-7745

ABSTRACT=In the recent last decade, the outbreak of large-scale green tides caused by Ulva prolifera have has continuously outbroken occurred in the Yellow Sea. Satellite remote sensing techniques, because of the advantages of large-area synchronous observations, have been widely used to monitor the distribution area and duration of green tides due to their advantages of their large-area synchronous observation. Ulva prolifera in the Yellow Sea is mainly distributed in bands or large patches during its flourishing stage. Previous studies have rarely reported the quantitative analysis of a single Ulva prolifera patch and its changes in the short term. Considering the characteristics of the high temporal resolution of the Geostationary Ocean Color Imager (GOCI) sensor and the patchy distribution of floating Ulva prolifera floating on the sea surface, we developed a feasible method for monitoringway to monitor Ulva prolifera based on by performing clustering analysis with density-based spatial clustering of applications with noise (DBSCAN) clustering analysis to capture the diurnal variation characteristics of a single Ulva prolifera patch during the day. Thise new approach was used to extract information from a single Ulva prolifera patch in the Yellow Sea in 2012 and 2017. The results showed that during the time of GOCI imaging, the tidal current was the main factor driving the drift of Ulva prolifera, and the drifting direction of Ulva prolifera was consistent with the direction of the local tidal current, with a coefficient of determination of 0.94. By changing the normalized difference vegetation index (NDVI) threshold, further more accurate atmospheric correction (AC) of GOCI data during the twilight periods was indirectly achieved. By cComparing the areal change in the single patch before and after AC, we speculated that the daily change in signal intensity received by the GOCI sensor in a day may be the main reason for the diurnal variation in the Ulva prolifera coverage area. The results showed the details of the diurnal variation in Ulva prolifera patches in the dynamic marine environment, and the main reason that may cause the this diurnal variation in the Ulva prolifera detection area was speculated.