# Feasibility of Wave Simulation in Typhoon Using WaveWATCH-III Forced by Remote-Sensed Wind
## 3 Results
### Validation of WW3-Simulated Waves  
It was proven in previous studies [3; 13; 14] that WW3 has good performances in hindcasting typhoon-induced waves over many parts of the global ocean. Assembling wind, CEMES currents, and CMES sea levels are treated as forcing in WW3 (version 6.07). In our study, the WW3-simulated waves for June-October 2022 are validated against the measurements from SWIM onboard CFOSAT and measurements observed from altimeter Jason-3. The WW3-simulated SWHs map during Typhoon Mindulle at 00:00 UTC on 26 September 2021 is shown in Figure 5a,c, in which the along-track SWHs from SWIM and Jason-3 are also shown. As shown in Figure 5d, there are over 500,000 matchups between the WW3 simulations and the measurements from altimeter Jason-3, with a 0.44 m RMSE, 0.28 SI, and a 0.83 Cor. The variation in SWH via the ERA-5 wave, the utilized approach, WW3 forced by ERA-5 wind, and the footprint of SWIM is illustrated in Figure 5b. The variation in SWH via assembling winds from WW3 and the footprint of SWIM is consistent at SWH up to 8 m. Furthermore, the wave simulations using assembling wind products are better than those in ERA-5 and the SWH via the WW3 model forced by ERA-5 wind, with an improvement of up to about 1 m. Additionally, the time difference between WW3 and SWIM is less than 30 min. Statistical analysis was conducted for 30 typhoons, yielding a 0.80 Cor of wave spectrum with a 0.49 Err, a 0.48 m RMSE of SWH with a 0.25 SI (Figure 6a), and a 0.95 s RMSE of PWP with a 0.1 SI (Figure 6b). Under this circumstance, it  
Figure 4: (**a**) Comparison of the maximum wind speed \(V_{max}\) between assembling data, ERA-5 data, and the measurements from NHC in 30 typhoons. (**b**) Comparison between assembling wind and ERA-5 data from 30 typhoons.  
is believed that assembling wind derived from multiple remote-sensed products is reliable for typhoon-induced wave simulation via WW3.  
As mentioned in Section 2, ERA-5 provides wave data over the global ocean, especially in TCs. Therefore, the bias of SWH (WW3-simulated SWH minus ERA-5) relative to the bias of wind (assembling minus ERA-5) was analyzed, as exhibited in Figure 7. It is not surprising that a positive bias occurs as the bias of wind speeds is larger than 5 m/s, which means that the bias of SWH has a positive relation with the bias of wind speed. This is because the sea surface wave is mainly determined by wind stress [13]. Moreover, the bias of SWH increases with the increasing bias of wind speed. In particular, the bias of SWHs could reach 4 m as the wind speed bias is greater than 30 m/s. Therefore, the assembling wind from multiple scatterometers and radiometers is a promising source of data for wave simulation via the WW3 model during typhoons because the underestimation of strong wind from the atmospheric model (i.e., ERA-5) is improved.  
Figure 5: (**a**) Distributions of SWHs from WAVEWATCH-III (WW3), in which along-track SWHs were measured via SWIM onboard CFOSAT. (**b**) Along-track variation in SWHs from ERA-5, WW3, and the footprint of SWIM. (**c**) SWH map from WAVEWATCH-III (WW3), in which along-track SWHs were measured using the Jason-3 altimeter. (**d**) SWH comparison between WW3 and measurements from the Jason-3 altimeter.