Tidal energy budget in the Zhujiang (Pearl River) Estuary

Abstract

Tidal energy budget in the Zhujiang (Pearl River) Estuary (ZE) is evaluated by employing high-resolution baroclinic regional ocean modeling system (ROMS). The results obtained via applying the least square method on the model elevations are compared against the tidal harmonic constants at 18 tide stations along the ZE and its adjacent coast. The mean absolute errors between the simulation and the observation of M2, S2, K1 and O1 are 4.6, 2.8, 3.2 and 2.8 cm in amplitudes and 9.8°, 15.0°, 4.6° and 4.6° in phase-lags, respectively. The comparisons between the simulated and observed sea level heights at 11 tide gauge stations also suggest good model performance. The total tidal energy flux incoming the ZE is estimated to be 343.49 MW in the dry season and larger than 336.18 MW in the wet season, which should due to higher mean sea level height and heavier density in the dry season. M2, K1, S2, O1 and N2, the top five barotropic tidal energy flux contributors for the ZE, import 242.23 (236.79), 52.97 (52.08), 24.49 (23.96), 16.22 (15.91) and 7.10 (6.97) MW energy flux into the ZE in dry (wet) season, successively and respectively. The enhanced turbulent mixing induced by eddies around isolated islands and sharp headlands dominated by bottom friction, interaction between tidal currents and sill topography or constricted narrow waterways together account for the five energy dissipation hotspots, which add up to about 38% of the total energy dissipation inside the ZE.