## 6 Conclusions  
This study aimed to improve the forecast skill of the sea breeze circulation along the east coast of Yeongdong in the Korean Peninsula by finding the optimal set of physical parameterization schemes in the Weather Research and Forecasting (WRF) using a global optimization method called the micro-Genetic Algorithm (GA). We developed a system that combines the WRF and the micro-GA (WRF-\(\upmu\)GA) and applied it to a combinational optimization problem.  
We selected nine observation stations in Yeongdong coastal region of the Korean Peninsula for the optimization and validation. The fitness function was composed of the normalized root mean squared error (\(RMSE\)) considering \(T_{2m}\), \(RH_{2m}\), \(WS_{10m}\), \(WD_{10m}\), \(WS\), and \(WD\). We simultaneously optimized three sea breeze cases selected by the sea breeze selection algorithm. Based on the WRF-\(\upmu\)GA system, we found that the optimal combination consists of the MYNN2 (PBL), Noah-MP (land surface), RRTMG (shortwave radiation), and RRTMG (longwave radiation) schemes.  
We first conducted validation tests for the variables used for optimization and confirmed that the optimized model results showed generally good matches with the observations. We then compared the optimized vs. non-optimized experiments and found that the overall performance of WRF using the optimal parameterization scheme set (OPTM) was excellent in sea breeze simulations. We noticed that an experiment with the scheme set of YSU, NoahMP, Dudhia, and RRTM also showed comparable performance. The YSU and MYNN2 schemes simulated well the PBL structure in the coastal areas and the sea breezes, respectively, in previous studies: the Noah-MP, commonly employed in the two experiments is also known as the best land surface scheme for simulating the sea breeze circulation. In the sensitivity experiments, we found that the optimized set of parameterization schemes was adjusted to show better features of the PBL structure and evolution.  
Figure 7: Time variation of PBL height (black line), horizontal wind speed (shading), and vector (arrow) on 15 April 2021. (a) OPTM, (b) EXP1, (c) EXP2, (d) EXP3, and (e) EXP4.  
We conclude that the dynamical and thermodynamical characteristics of sea breeze circulation can be analyzed more accurately using the optimal combination of the physical parameterization schemes, obtained by the WRF-uGA system; thus, this kind of combinational optimization can lay the foundation for understanding the local circulations and meteorological phenomena in the coastal areas, including the low-level air convergence, precipitation, and atmospheric pollutant.  
Conceptualization, J.W.Y. and S.K.P.; methodology, J.W.Y. and S.K.P.; software, J.W.Y., S.K.P. and S.L.; validation, J.W.Y.; investigation, J.W.Y. and S.K.P.; writing--original draft preparation, J.W.Y.; writing--review and editing, J.W.Y., S.K.P. and S.L. All authors have read and agreed to the published version of the manuscript.  
This research is supported under the grant of Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2018R1A6A1A0025520). It is partly supported by the NRF grant funded by the Korea government (MSIT) (NRF-2021R1A2C1095535).  
Not applicable.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.