Observing optically complex oceans in situ and from space

The radiative transfer approach to interpretation of ocean colour remote sensing (OCRS) data is based upon quantitative measurement of inherent optical properties such as absorption, attenuation and backscattering coefficients along with associated constituent concentrations. These data are used to establish realistic simulations of underwater and water leaving light fields that can be used as a test-bed for algorithm development. The award of this Advanced Fellowship has led to significant progress in a number of key areas: •Advances in determining scattering properties of marine particles.•Significant improvement in measurement methodologies for in situ absorption and attenuation measurements.•New insight into the effect of multiple scattering on the angular distribution of scattered photons.•Further development of remote sensing algorithms for suspended sediment concentrations.•Analysis of links between physical and biogeochemical processes based on ocean colour observations.Each of these areas has resulted in publications published or submitted to leading journals. In addition there are several areas of on-going work that are close to publication readiness, including: development of a comprehensive set of specific inherent optical properties for the Ligurian Sea using state of the art IOP methods, development of a new spectral deconvolution method for OCRS data, based upon a well-established physical model, that is specifically designed to provide optimal estimates of constituent concentrations and associated uncertainties, analysis of OCRS algorithm performance using radiative transfer simulations and accounting for measurement uncertainty in both radiometric observations and measurement errors for validating constituents. The vast majority of initial objectives has therefore been achieved or will be within a short period from now. This work has benefitted from extensive collaborations with pre-existing and new partners including the NATO Underwater Research Centre (Italy), HZG (Germany), WETLabs Inc (USA), IOPAN (Poland), Argans Ltd (UK) and LOV (France). This international network has ensured that the work performed under the auspices of the Advanced Fellowship has been closely integrated with the wider marine optics and oceanographic community. Within the UK there has been on-going collaboration with NOC (Southampton and Liverpool) as well as the Universities of Plymouth and Bangor. OCRS data is increasingly been prepared for validation and assimilation into coupled physical-ecosystem models. There is also considerable interest from government agencies in the potential for using OCRS data for monitoring compliance with environmental legislation. During the course of the Fellowship I have provided advice to both the Scottish Government and also the European Space Agency on aspects of both OCRS data and in situ IOPs. The rigorous physical approach that has been developed here is closely aligned with user demand for quality assured products. My focus on determining product uncertainty has placed this research in the vanguard (with other leading groups) of a movement towards more accurate, quantitative OCRS and in situ IOP products. This is reflected in the growing international reputation of the Strathclyde Marine Optics and Remote Sensing Group and in continuing invitations to collaborate with other leading groups in the field.