  The ROMS modeling system was applied to the California Upwelling System
(CalUS) to understand the key hydrodynamic conditions and dynamics of the
nitrogen-based ecosystem using the NPZD model proposed by Powell et al. (2006).
A new type of sponge layer has been successfully implemented in the ROMS
modelling system in order to stabilize the hydrodynamic part of the modeling
system when using so-called reduced boundary conditions. The hydrodynamic
performance of the model was examined using a tidal analysis based on tidal
measurement data, a comparison of the modeled sea surface temperature (SST)
with buoy and satellite data, and vertical sections of the currents along the
coast and the water temperature. This validation process shows that the
hydrodynamic module used in this study can reproduce the basic hydrodynamic and
circulation characteristics within the CalUS. The results of the ecosystem
model show the characteristic features of upwelling regions as well as the
well-known spotty horizontal structures of the zooplankton community. The model
thus provides a solid basis for the hydrodynamic and ecological characteristics
of the CalUS and enables the ecological model to be expanded into a complex
ecological model for investigating the effects of climate change on the
ecological balance in the area investigated.
