## 3 Simulations and Discussion
### Initial Analyses after Data Assimilation
To verify the assimilation results with the RO data, the wind, temperature, and geometric height analyses at 850 hPa at 0000 UTC 4 July 2016 (the end assimilation) are compared with the ECMWF reanalysis (ERA-Interim) [50] in Figure 5. There is a cut-off high extending from the western flank of the subtropical high, where all three experiments gave a colder temperature compared to ERA-Interim. REF provided the weakest intensity of the warm air with the narrowest high core than both GTS and BND, which could be possibly due to the colder and drier increments induced by the RO data assimilation in Figure 4. Near the inner typhoon, there are few differences in the geometric height for the three experiments, which compared well with ERA-Interim. However, the wind and pressure intensities of the typhoon for BND and GTS (Figure 5b,d) are considerably stronger than those for REF (Figure 5c) and are also more intense than the ERA-Interim (Figure 5a). Typhoon intensity may be somewhat under-predicted by the global model assimilation as in the ERA-Interim. Indeed, the CWB best-track maximum wind (shown later) is stronger than that for both BND and GTS. The overall wind and geometric height distributions in the environment surrounding the typhoon are consistent with the ERA-Interim for the three experiments, except for the region of the cut-off high. All the experiments are conducted with the resolution of 60-15 km and initialized 5-day MPAS forecasts at 0000 UTC 4 July 2016. Figure 6 shows the track and intensity of the forecasted typhoon for GTS, REF, and BND, compared to the CWB best track data. The results without any DA (NoDA) are also included for comparison. The forecasted tracks for all the experiments are in good agreement with the best track before 0000 UTC 7 July,  
Figure 5: Geometric height (contours at an interval of 10 m), temperature (shaded in K), and wind vector (m s\({}^{-1}\)) at 850 hPa at 0000 UTC 04 July 2016 (the end assimilation) for (**a**) the ERA-Interim, (**b**) GTS, (**c**) REF, and (**d**) BND. but closer to the best track in the earlier three days obviously for the DA experiments (GTS, BND, and REF) compared to NoDA. It is noticed that that NoDA gives a much slower translation when moving closer to the terrain with the largest northward track deflection after 3 days (Figure 6a). The track for REF is associated with a generally southward deviation after 24 h, compared to BND and GTS. However, the track errors for REF are comparable to those for BND in the first three days and indeed are smaller afterward due to the fact that the BND track has deviated northward afterwards (Figure 6b). The typhoon intensities for all DA experiments are weaker than the best track intensity, especially near and after landfall in Taiwan; however, only the intensity for NoDA is stronger than the best track intensity at the initial time and on the first day (Figure 6c). Consequently, NoDA still maintains a stronger typhoon more comparable to the best track intensity than the other experiments throughout the forecast. It is apparent that the typhoon intensity for BND is much stronger than that for REF, as already shown earlier. Although BND and GTS have further under-predicted typhoon intensities than NoDA; their intensification rates are similar in the first three days. Again, REF obtains the weakest typhoon intensity in the first three days, which is consistent with Figure 5. In this study, we focused on the track and intensity evolution of the typhoon before landfall as the topographic effect of Taiwan terrain will greatly complicate the responses of the impinging typhoon near and after landfall. The typhoon intensity may correlate to the accumulated mid-lower tropospheric increments during the DA, as discussed in [PERSON] et al. (2014). The impacts of RO data appear to be substantially larger for typhoon track forecasts than intensity forecasts ([PERSON] and [PERSON], 2014, 2015) as the RO observations can only directly retrieve the thermodynamic information from (1).