Forecasting Coastal Optical Properties using Ocean Color and Coastal Circulation Models

摘要

Coupling the 3-d ocean optical imagery with 3-d circulation models provides a new capability to understand coastal processes. Particle distribution derived from ocean color optical properties were coupled with numerical circulation models to determine a 24 hour forecast of particle concentrations. A 3-d particle concentration field for the coastal ocean was created by extending the surface satellite bio-optical properties vertically by parameterzing an expediential Gaussian depth profile. The shape of the vertical particle profile was constrained by 1) the depth of the 1% light level 2) the mixed layer depth 3) the intensity of the layer stratification 4) and subsurface current field and the surface bio-optical properties. These properties were obtained from MODIS ocean optical products (phytoplankton absorption and backscattering) and the Intra-America Sea Nowcast Forecast System - Naval Coastal Ocean Model. The 3-d particle distribution was imbedded into a 3-d circulation model and the particles advected hourly using forecast model 3-d current. The particles were diffused, dispersed and differentially settled during the advection processes. Following the 24 hour advection, the resultant particle distribution were accumulated into 1 km spatial grid and vertically to a 1 attenuation length (satellite penetration depth) and the forecast ocean color backscattering image determined. The forecast image was compared with the next day ocean color backscattering image to define the error budget. The ocean color particle tracking, defines fine spatial scales processes such as local upwelling and downwelling, which are essential in understanding the coupling of physical and bio-optical processes. The methods provide new capability for characterizing how subsurface particles layers change in response to cross and along shelf exchange processes. Results show methods to forecast satellite optical properties in coastal areas and examine how sequential MODIS imagery of the particle scattering is related to particle transport and physical processes.