Application of auto-regressive (AR) analysis to improve short-term prediction of water levels in the Yangtze estuary

Due to the complex interaction between the fluvial and tidal dynamics, estuarine tides are less predictable than ocean tides. Although the non-stationary tidal harmonic analysis (NS_TIDE) model can account for the influence of the river discharge, the predictive accuracy of the water levels in the tide-affected estuaries is yet to be improved. The results from recent studies using the NS_TIDE model in the lower reach of the Yangtze estuary showed the best root-mean-square-error (RMSE) between the predicted and measured water levels being in a range of 0.22 similar to 0.26 m. From the spectral analysis of the predictive errors, it was also found that the inaccurate description of tides in the sub-tidal frequency band was the main cause. This study is to develop a hybrid model in combination of the auto-regressive (AR) analysis and the NS_TIDE model in an attempt to further improve short-term (with time scale of days) water level predictions in the tide-affected estuaries. The results of the application of the hybrid model in the Yangtze estuary show a significant improvement for water level predictions in the estuary with the RMSE of 24 h prediction being reduced to 0.10 similar to 0.13 m.