A particle-tracking technique for spatial and temporal interpolation of satellite images applied to Lake Superior chlorophyll measurements

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© 2017 International Association for Great Lakes Research Ocean color satellite-derived estimates of water properties are generally discontinuous in spatial and temporal coverage due to cloud cover. We describe a novel method for providing an estimate of continuous distribution of a satellite-derived water property, chlorophyll concentration in Lake Superior. The method uses calculated wind-driven lake circulation from a hydrodynamic model to estimate the evolution of the chlorophyll concentration field between available imagery. This new technique considers hydrodynamic effects by integrating a property-carrying particle model (PCPM) and an Eulerian concentration remapping approach. The PCPM interpolation method uses computational tracer particles that move with the calculated lake currents to represent the chlorophyll field. The concentration associated with each particle is dynamically adjusted toward the satellite-derived chlorophyll field at times and locations where imagery is available and produces a spatially and temporally continuous estimate of the chlorophyll concentration field. One of the important characteristics revealed from the analysis is the seasonally-dependent and region-specific chlorophyll concentration, which is significantly controlled by seasonal hydrodynamic conditions in Lake Superior. Analysis suggests that without adding extra sampling cost, moving a few sampling locations from offshore water to sample the embayments and southern coasts can provide more accurate characterization of the spatial pattern of chlorophyll concentration in Lake Superior. Furthermore, we found that Lake Superior chlorophyll concentrations do not appear to have changed significantly over the past 12 years and likely only slightly or not at all over the last 50 years, which differs from that in the other upper Great Lakes.

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Journal of Great Lakes Research