ISWFM-NSCS v2.0: advancing the internal solitary wave forecasting model with background currents and horizontally inhomogeneous stratifications

Abstract. A new version of an internal solitary wave (ISW) model, the Internal Solitary Wave Forecasting Model-Northern South China Sea version 2.0 (ISWFM-NSCS v2.0), is presented. The background currents and horizontally inhomogeneous stratifications are implemented in ISWFM-NSCS v2.0 to better reproduce ISW properties, including arrival time, mode-1 wave amplitude, wave-induced velocity, characteristic half-width and propagation direction. Optimized viscosity and diffusivity coefficients (i.e., 1.0×10^-2 m² s^-1 in horizontal and 1.0×10^-5 m² s^-1 in vertical) are also introduced in ISWFM-NSCS v2.0 to maintain stable stratifications within the model domain, thereby prolonging the model’s valid forecasting period. A mooring station around the Dongsha Atoll is presented for model evaluation and numbers of sensitivity experiments are implemented to illustrate the individual effect of the major updates. In comparison with ISWFM-NSCS v1.0, ISWFM-NSCS v2.0 significantly enhances model accuracy in forecasting ISW characteristics, with a 37 % improvement in arrival time, a 34 % improvement in mode-1 wave amplitude, a 25 % improvement in wave-induced velocity, and an 85 % improvement in half-width.