Combining Satellite Ocean Color Imagery and Circulation Modeling to Forecast Bio-Optical Properties: Comparison of Models and Advection Schemes
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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Remote sensing of ocean color provides synoptic surface ocean bio-optical properties but is limited to real-time or climatological applications. Many applications, including navy mission planning using electro-optical sensor performance models, would benefit from a forecast capability. To achieve this, we couple satellite imagery with numerical circulation models to provide short-term 24-48 hr forecasts of bio-optical properties. These are first-order approaches they do not account for any biogeochemical mechanistic processes growth, grazing, sinking, resuspension, only dynamical processes currents. Nonetheless, by comparing forecast distributions with next-day satellite imagery, we can assess errors and estimate how strongly the physical processes control the bio-optical distribution patterns. We compare optical forecast results from three Navy models and two advection approaches. The Intra-Americas Seas NowcastForecast System IASNFS, the Hybrid Coordinate Ocean Model H YCOM, and the Northern Gulf of Mexico NowcastForecast System NGOMNFS provide current direction and magnitude at hourly time-steps, at 6km, 4km, and 2km resolution, respectively. We apply the current vectors from these models to 1km resolution SeaWiFS-derived bio-optical properties chlorophyll, backscattering coefficient, total and inorganic suspended particulate matter concentration to produce advected, surface forecast images, using both a passive tracer advection scheme Eulerian approach and a particle trajectoryaccumulation scheme Lagrangian approach. Difference images between the next-day, satellite-derived optical fields and the model-advected fields provide a quantitative assessment of the forecast accuracy of the three models and two advection schemes, to assess the degree to which physical dynamics control the bio-optical distribution patterns. We compare different seasons spring vs. fall as well as different forecast periods 24 vs. 48hr.
- Physical and Dynamic Oceanography