Actual Analysis Results
According to an analysis of the wind speed in six cities from 1998 to 2019, Gwangju, Daejeon, Daegu and Busan are on the decline, while Seoul and Incheon are on the rise. As a result of numericalizing the air stability values, Gwangju, Daejeon, Daegu and Busan showed strong declines, Seoul showed weak declines and Incheon showed an increase. In other words, Gwangju, Daejeon, Daegu, Busan, and Seoul have become more unstable than in the past, and Incheon has become stable. Fine dust levels are on the decline in all six cities. We expected that the atmosphere would stabilize as wind speed decreased, which would increase fine dust levels. However, there were no areas that showed this trend. However, as wind speeds decreased in Gwangju, Daejeon, Daegu, and Busan except for Seoul and Incheon, we could find a relationship in which air stability decreased and fine dust concentrations decreased.
Why is it different?
According to the results released by Yoon Jin-ho, a professor at the Gwangju Institute of Science and Technology, atmospheric stability has increased by 10% since the mid-2000s. Estimating the different reasons from our analysis, the air stability value considered by Yoon Jin-ho's team classifies the mixing degree of the atmosphere, such as the temperature lapse rate and turbulence intensity caused by wind direction fluctuations. An important factor in determining atmospheric stability in this study is the temperature distribution, which varies with height, and they targeted 1000-975 hPa. However, the factors used in grading atmospheric stability in our study are solar radiation from 6 to 20 o'clock and wind speeds of 10m above. It is estimated that our results and the results from the research team were different in this process. In addition, the research team set a period of 60 years to investigate atmospheric changes. However, in our case, data only from 1998 to 2019 were used to compare with the PM10 data, so this may be the cause.
The government enacted the Capital area Air Quality Improvement Special Act in 2003 to improve the air environment and established and implemented a basic air environment management plan for the Seoul metropolitan area. As a result, not only air pollution emissions but also fine dust concentrations decreased. The decrease in the concentration of fine dust is a characteristic that can be found not only in Korea, but also in China and other OECD countries. Nevertheless, why do we feel that the fine dust problem is getting serious? Despite the overall improvement in air quality, the days of high concentration of fine dust continue to occur. In addition, the environmental standards for fine dust (PM2.5) have been strengthened to the same level as in the United States and Japan from March 27, 2018, and the upper limit of 'normal' has decreased from 50㎍/㎥ in 2018 to 35㎍/㎥. The 'bad' section that was 50~100㎍/㎥ was adjusted to 36~75㎍/㎥. The “very bad” section starting from 101㎍/㎥ or higher starts from 76㎍/㎥. As the changed forecast standard was applied, the number of days to issue an advisory notice increased by 2.7 times and the number of days to issue an alert doubled. Although the concentration of fine dust is on a decreasing trend, the number of days the warning is issued has rather increased, reinforcing public awareness that the concentration of fine dust is vaguely increasing.
fig1. From 1990 to 2018, it shows that fine dust levels have decreased not only in Korea, but also in China and other OECD countries. Provide Seoul Institute for Health and Environment
Suggestion
- The reason why wind speeds are different in the upper and lower atmosphere
- The degree of urbanization(humanitarian environment-building etc) affect the speed of wind
- Adding factors that affect the air stability rating, such as clouds, wind volume, and temperature
- Identify the characteristics of each city
- Consider other fine dust factors such as PM2.5.
- Consider Topographical Factors