## 3 Results
### Verification of the ATs
Figure 10: The observed and simulated 10-m wind (in arrow; intervals of 5 kt) and lowest model-level radar reflectivity (in color; dBZ) from 0600 to 0800 UTC (1400 to 1600 LST) on 5 August 2018, (**a–c**) observations, same as Figure 4, (**d–f**) DA01, (**g–i**) DA02, (**j–l**) DA03, and (**m–o**) DA04 simulations. Additionally shown are the approximate location of Pingtung Air Force Base (black star) and vertical cross-section planes (black line) for subsequent figures. Similar to Figure 9, the lines between x and x’ are plotted for further comparison. At 0600-0800 UTC in the C2 group, the AT entered its mature stage. From 0600 to 0700 UTC, the onshore wind was strengthened by the sea breeze effect on the coasts of Tainan, Kaohsiung, and Pingtung in the experiments of DA01 (Figure 10d,e), DA02 (Figure 10g,h), DA03 (Figure 10j,k), and DA04 (Figure 10m,n), and the maximum surface wind speed ranged from 8 to 12 kt. From 0700 to 0800 UTC, as the AT developed and moved to the west, the wind on the east side of the ATs shifted to east-southeast in the experiments of DA01 (Figure 10e,f), DA02 (Figure 10h,i), DA03 (Figure 10k,l), and DA04 (Figure 10n,o). A vertical cross-section of the precipitation radar echoes in the C1 experiments without data assimilation, NDA02 (Figure 10a-c) as an example, the locations of AT development were farther west, the ATs moved much faster, and precipitation radar echoes of ATs dissipated quicker than those of observations. A vertical cross-section of the precipitation radar echoes in the C2 experiments (Figure 11) revealed that the onshore wind from the west coast and downdrafts collided on the surface, triggering deep convection with high radar reflectivity as in Ref. [52], especially for the experiments of DA02, DA03, and DA04. The ATs associated with deep convection with sufficient convergence extended from near the surface to above 10 km vertically (Figure 11). In contrast to the C1 experiments, the C2 experiments DA02, DA03, and DA04 revealed substantial improvements and successfully forecasted the mature stage of ATs at 0700 UTC, which was characterized by vigorous updrafts and downdrafts [53; 54; 55]. Compared with the observations, DA02 exhibited more accurate results in forecasting the locations and intensities of ATs and the associated wind fields than did the other three experiments of DA01, DA03, and DA04. To have a common basis for comparison of vertical cross sections of the precipitation radar echoes between the C2 and C3 experiments, it is better to use the same initial forecast time of model simulations. Therefore, DA04 (Figure 12j-l) of C2 experiments and CDA03 (Figure 13a-c) of C3 experiments, which both had the same initial forecast time and better forecast performance, were used as examples for comparisons. In contrast to the C2 DA04 experiment, the C3 CDA03 experiment was similar in the locations of convective cells but quite different in the convective intensity. At 0700 UTC (Figure 13b), the convective intensity of the C3 CDA03 experiment at the east of Pingtung Airport was weaker than that of the C2 DA04 experiment (Figure 12k). However, two convective cells formed at the west  
Figure 11: Vertical cross section of maximum reflectivity and horizontal wind vector of NDA02 simulations at (**a**) 0600, (**b**) 0700, and (**c**) 0800 UTC (from 1400 to 1600 LST) on 5 August 2018, along the northwest-to-southeast plane (from x to x\({}^{\prime}\)) depicted in Figure 9. The title of each chart showed the accurate location of reflectivity we selected and the approximate location of Pingtung Air Force Base was depicted as black star. of Pingtung Airport in the C3 CDA03 experiment were stronger than those at the same location in the C2 DA04 experiment.