Abstract
<p> <p id="x-x-sp0090"> Since the outbreak of a large-scale <em> Ulva prolifera </em> bloom in the Yellow Sea during the Qingdao Olympic Sailing Competition in summer 2008, <em> Ulva </em> blooms have been a marine hazard every summer. Accurate and timely information on <em> Ulva </em> areal coverage and biomass is of critical importance for governmental responses, decision making, and field studies. Previous studies have shown that <a title="Learn more about satellite remote sensing from ScienceDirect's AI-generated Topic Pages"> satellite remote sensing </a> is the most effective method for this purpose, yet <em> Ulva </em> areal coverage has been estimated in different ways with significantly different results. The objective of this paper is to determine the lower and upper bounds (T <sub> 0 </sub> and T <sub> 1 </sub> ) of algae-containing pixels in Floating Algae Index images with an objective method that accurately estimates the <em> Ulva </em> areal coverage in individual images, and then converts coverage to biomass using a previously established conversion equation. First, a seawater background image, FAI <sub> sw </sub> , is constructed to determine T <sub> 0 </sub> , which varies for different algae patches. Then, T <sub> 1 </sub> is determined from water tank and <a title="Learn more about in situ measurements from ScienceDirect's AI-generated Topic Pages"> in situ measurements </a> as well as <a title="Learn more about radiative transfer from ScienceDirect's AI-generated Topic Pages"> radiative transfer </a> simulations to account for different sensor configurations, solar/viewing geometry, and atmospheric conditions. Such determined T <sub> 1 </sub> for <a title="Learn more about MODIS from ScienceDirect's AI-generated Topic Pages"> MODIS </a> 250-m resolution data is validated using concurrent and collocated 2-m resolution WorldView-2 data. Finally, <em> Ulva </em> areal coverage derived from MODIS data using this method are compared with those from the high-resolution data (OLI/Landsat, WFV/GaoFen-1), with a mean relative difference of 9.6%. Furthermore, an analysis of 17 same-day MODIS/Terra and MODIS/Aqua image pairs shows that large viewing angles, atmospheric <a title="Learn more about turbidity from ScienceDirect's AI-generated Topic Pages"> turbidity </a> , and sunglint can lead to an underestimation of <em> Ulva </em> coverage of up to 45% under extreme conditions. </p></p>
Original language | American English |
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Journal | Remote Sensing of Environment |
Volume | 223 |
DOIs | |
State | Published - Jan 1 2019 |
Keywords
- Ulva prolifera
- Remote sensing
- Areal coverage
- Biomass
Disciplines
- Life Sciences