## 4 Results
### Simulations  
We validated the simulations with the YSU, MYJ, MYNN, and ACM2 PBL schemes using the radiosonde observation data and the ground meteorological data from Gangnam AWS (Figure 2). We show the simulated and observed 2-m air temperature and 10-m wind speed at the location of Gangnam AWS (Figure 6a,b). We also show the air temperatures and wind speeds from the numerical simulations and radiosonde observation at 925 and 850 hPa (Figure 6c-f). The WRF model overestimated the daily minimum air temperature on 17 January, but the diurnal variation of the observed 2-m air temperature was well-reproduced in all four simulations in general. Especially, in the four simulations, the air temperature decrease from 0000 to 0600 LST on 18 January was small due to the weakened radiative cooling by the cloudy weather, as exhibited in the observation. After 1800 LST on 18 January, the four simulations underestimated 2-m air temperature. The haze at the night on 18 January was not well-reproduced in the four simulations, resulting in an overestimation of radiative cooling from 1800 LST 18 January. The simulated 10-m wind speed was generally larger than the observed one. The magnitude of the 10-m wind speed increase from 1000 LST on 18 January was larger in the four simulations than in the observations. The wind speed decrease in urban areas due to buildings was not well-represented in the numerical simulations, similar to other numerical simulations [28; 29; 30]. At 925 and 850 hPa, the general tendencies of the simulated air temperatures in the four simulations reproduced those in the radiosonde observation. However, small-scale perturbations in the air temperature observation were not captured by the simulations in general. The general tendencies of the simulated 925 and 850 hPa wind speeds in the four simulations were similar to the observations, except for the wind speed increase from 0000 to 0600 LST on 18 January. The air flow in the upper troposphere related to the wind speed increase (Figure 4b) was not accurately reproduced in the simulations. Figure 6: Time series of simulated and observed (**a**) 2-m air temperature and (**b**) 10-m wind speed at Gangnam AWS; (**c**) air temperature and (**d**) wind speed at 925 hPa, and (**e**) air temperature and (**f**) wind speed at 850 hPa. Table 1 shows the mean bias error (MBE) and root mean square error (RMSE) of the simulated air temperature and wind speed near the surface at 925 and 850 hPa. Near the surface, the MBE and RMSE of the air temperature and wind speed were the smallest in the simulation with the MYJ scheme [31]. At 925 hPa, the MBE and RMSE of the air temperature were the smallest in the simulations with the YSU and MYJ schemes, respectively. The MBE and RMSE of the wind speed at 925 hPa were smallest in the simulation with the ACM2 scheme. At 850 hPa, the MBE and RMSE of the air temperature were the smallest in the simulations with the YSU and ACM2 schemes, respectively. For the 850 hPa wind speed, the simulations with the ACM2 and YSU schemes had the smallest MBE and RMSE, respectively. The MYJ scheme reproduced the second most accurate air temperature and wind speed at 850 hPa. By comparing the MBE and RMSE of the air temperature and wind speed, we concluded that the MYJ scheme reproduced the most accurate simulation results. To compare the structures of the lower troposphere in the four simulations, Hovmoller diagrams of the potential temperature and water vapor mixing ratio using the simulation data at the location of the radiosonde launch site are shown in Figure 7. From 0800 to 1300 LST on 17 January, the potential temperature below \(\sim\)1 km slowly increased in the four simulations compared with that in the observations. The four simulations did not reproduce the abrupt development of the layer with nearly constant potential temperature at 1300 LST. The process of the residual layer with a small vertical temperature gradient becoming a part of the CBL was not well-simulated in the four simulations.