SEASONAL VARIATION OF CHLOROPHYLL AND PRIMARY PRODUCTIVITY IN CENTRAL ARABIAN SEA : A MACROCALIBRATED UPPER OCEAN ECOSYSTEM MODEL

M.K. Sharada and K.S. Yajnik*

CSIR Centre for Mathematical Modelling and Computer Simulation (C-MMACS),
Bangalore 560 037, India
*Present address : Regal Manor, 2/1 Bride Street, Langford Town, Bangalore 560 025, India;
Email : ksy@letterbox.com

Seasonal variation of chlorophyll has been of considerable interest on account of the effect of photosynthesis on ocean-atmosphere carbon exchange. It can be predicted by a dynamical system model of the marine ecosystem coupled with a physical oceanographic model. There is however a major difficulty in the calibration of contemporary ecosystem models on account of sparse data and a large number of model parameters. This paper reports a new approach of macrocalibration in which values of six parameters are determined by examining in detail the seasonal variation of chlorophyll and primary productivity keeping in view the observations of two Indian JGOFS cruises. Both switching and non-switching versions of grazing functions are used in a 7-component FDM model. Detailed simulations are reported for one station (16^oN, 65^oE). They show the effects of dependence of grazing preference on prey density on the behaviour of the ecosystem. The results of the simulation also provide a partial basis for developing correlations of primary production with chlorophyll and sediment flux.