MODELING THE VERTICAL-DISTRIBUTION OF CHLOROPHYLL IN THE CALIFORNIA CURRENT SYSTEM

Remote sensing of ocean color provides data on the average photosynthe tic pigment concentration in the first optical depth. To model primary productivity in the water column, estimates of the vertical distribut ion of pigment concentration are required. We used a Gaussian distribu tion function proposed by Platt et al. [1988] to represent the pigment vertical profile with four parameters. Empirical relationships were d erived to estimate these parameters for the California Current System between 28 degrees and 37 degrees N, using California Cooperative Ocea nic Fisheries Investigations (CalCOFI) data (1978-1992); The studied a rea was divided into six spatial subregions and temporally into warm a nd cool seasons. Regression models were developed for each subregion a nd season to estimate each of the parameters as functions of surface c hlorophyll. Comparison of chlorophyll profiles obtained during the 199 4 CalCOFI cruises (not used for constructing the models) with those es timated with our models shows a general agreement. Assuming a homogene ous biomass profile resulted in underestimation of integrated primary productivity (pp) by as much as 30%, whereas the modeled profiles gave equal or overestimated pp (up to 23%), with respect to the values der ived from the real 1994 profiles.