In this thesis, we estimate the proper exposure time for the UV radiation in Korea. The UV radiation is prominent for the harmful effect so that it should be avoided. However, the UV radiation is also a decisive source of the vitamin D synthesis, which is necessary to prevent an immune disease. Hence, the optimal exposure time for the UV radiation should be estimated for a balanced exposure to the sunlight. The optimal exposure time considering vitamin D synthesis recently got attention in some countries, but there has been no attempt to thoroughly estimate the exposure time in Korea. Here, we present a heuristics to calculate the optimal exposure time in Korea. We improved the previous algorithm for the calculation of the exposure time, by considering the time dependency of the UV radiation. By the heuristics, we calculated the exposure time based on the data from KMA''s UV radiation observation network, and validated the calculation via the comparison of it with a separate calculation based on the forecast of the unified model.
We calculated the exposure time for the six regions in Korea as follows: (1) Gangneung, (2) Seoul, (3) Anmyeondo, (4) Pohang, (5) Mokpo, and (6) Gosan. For each of the regions, the calculation was specified for each of the four seasons in Korea. The optimal exposure time was shorter in summer than in winter, and the UV radiation in winter was insufficient to synthesize the vitamin D in all the six regions in Korea. The result revisits the necessity of the concise knowledge on the optimal exposure time, especially for the minimum requirement of the exposure in contrast to the popular belief on the harm by UV. Most of all, we analyzed the sensitivity of the calculation to the meteorological factor including cloud and aerosol. The amount of cloud showed the positive correlation with the optimal exposure time, and the concentration of aerosol also showed the positive correlation. The correlation of a meteorological factor varied jointly with the other factor. We discuss in detail the joint correlation, and speculate the reason for the variance. The thorough estimation of the optimal exposure time for the UV radiation in Korea, which is up-to-the-minute, is a fundamental requirement to provide a detailed UV guideline to the Korean society. We expect this thesis, which specify the minimal requirements and the maximal threshold of the exposure time, to be utilized for the UV guideline so that the social acknowledgement on the positive effect of the UV exposure takes place.