Response of the Pearl River Estuarine Complex to the Meteorological Forcing and River Inflow: A Cybernetics Approach
Keywords:Sub-tidal, sea level, system simulation, CAR model, multistep prediction, China
The present paper is a study on the sub-tidal sea level dynamic system from an extensive investigation on the "sea-river-atmosphere" system in the Pearl River Delta, Guangdong, China. The two-year long continuous time series records of sea level and meteorological forcing collected from more than 18 stations in the Pearl River Delta area reveal large amplitude fluctuations within the sub-tidal range 0.01-0.5 cpd. These fluctuations, according to power spectrum and coherence spectrum analysis, represent direct or indirect response of the estuary to variations in river inflow, wind stress and atmospheric pressure. MISO CAR model for each station is identified based on 1982 time series records. The system output is sub-tidal sea level, system inputs are river discharge, wind stress and atmospheric pressure. Models obtained and validated are used to conduct multistep prediction of 1983 subtidal sea level with good agreement. Frequency response analysis based on the models provides some important insights into the system. It is found that the maximum response of the estuary occurs at the frequencies 0.025-0.07 cpd. System simulations reveal, quantitatively, the relative importance and variations of the control variables on sea level in the estuarine complex. Response analyses in both frequency and time domains indicate that the nontidal sea level system is an oscillatory system. Its effects on estuarine circulation, volume, salt and sediment transport, and the formation of turbidity maximum need further study.