IOCCG Summer Lecture Series 2012

2 – 14 July 2012 - Villefranche-sur-Mer

The International Ocean Colour Coordinating Group (IOCCG) organized the first IOCCG Summer Lecture Series dedicated to high level training in the fundamentals of ocean optics, bio‐optics and ocean colour remote sensing. This was a 2‐week intensive course that took place from July 2nd – 14th at the Laboratoire d'Océanographie de Villefranche (LOV), Villefranche‐sur‐mer, France. A total of 13 renowned lecturers were invited to teach at the course and 17 students from 13 different countries took part in the course. More than 100 students had applied to participate in the course and the 17 remaining applicants were primarily chosen with respect to their motivation and on the basis of their academic background. The majority of them were PhD students and post‐Docs, and some were starting their careers as young researchers. The participants came from a broad range of backgrounds, but all were familiar with at least some domains of ocean colour science and had a solid understanding of ocean colour remote sensing.

Ocean colour remote sensing in turbid coastal waters (1)

by Kevin Ruddick, Royal Belgian Institute of Natural Sciences (RBINS), B‐1200 Brussels, Belgium

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Abstract

The use of ocean colour remote sensing data has increased dramatically over the last ten years, particularly for coastal waters where impacts between the marine environment and human activities may be particularly intense. Many of these coastal waters will be turbid because of high concentrations of suspended particulate matter caused by a variety of processes including high biomass algal blooms, sediment resuspension by wind/tide, river plumes, etc. Within these lectures on “Ocean Colour Remote Sensing in turbid coastal waters” the specific challenges and opportunities presented by turbid waters will be presented, where “turbid” is understood here to indicate waters with high particulate scattering.

There are two major additional difficulties for ocean colour remote sensing in turbid coastal waters. Firstly, atmospheric correction is more difficult in turbid waters because it is not possible to assume zero near infrared marine reflectance (“black pixel assumption”), thus complicating the decomposition of top of atmosphere measurements into atmospheric and marine reflectances. Secondly, the optical properties of non‐algae particles, such as mineral particles from bottom resuspension or from river discharges, need to be considered in addition to algal particles. If the absorption and scattering of nonalgae particles is significant compared to that of algal particles it may become difficult or even impossible to distinguish the optical properties of the algal particles. In such conditions the estimation of chlorophyll a may become severely degraded or suffer from a detection limit problem. In turbid waters both the atmospheric correction and the chlorophyll retrieval problems are highly dependent on the technical specification of the remote sensors being used, and in particular on the spectral band set. These two key issues will be explained in detail, via lectures and via simple computer‐based exercises.

The algorithmic approaches that can be used to deal with these problems will be outlined, based on the current state of the art and with reference to the capabilities of past, current and future ocean colour sensors such as SeaWiFS, MODIS, MERIS, GOCI and OLCI.
In addition to aspects of chlorophyll retrieval in turbid coastal waters, other relevant parameters will be discussed, including diffuse attenuation coefficient, euphotic depth, suspended particulate matter, etc. The links with applications in marine science and coastal zone management will be described.

Requirements for the lectures

  • A basic knowledge of the definitions of optical properties (scattering, absorption, attenuation) from other lectures from this IOCCG summer school, particularly those of Mark Dowell, Zhongping Lee and Curtis Mobley.
  • An ability to use basic functions of Excel.

Bibliography

IOCCG report #3 on “Remote Sensing of Ocean Colour in Coastal, and Other Optically‐ Complex, Waters”, available from http://www.ioccg.org/reports/report3.pdf


Speaker(s) : Kevin Ruddick, Royal Belgian Institute of Natural Sciences (RBINS), B‐1200 Brussels, Belgium
Public : All
Date : Wednesday 11 july 2012
Place : Villefranche-sur-Mer