Result
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In order to see the change in the average monthly atmospheric stability by year, the daily average atmospheric stability was calculated by using the total solar radiation from January 1, 1998 to December 31, 2019 and wind speed data from 6 to 20. Using the Pasquill stability classification table, the A grade was numerically expressed as 1, B grade as 2, C grade as 3, and D grade as 4. The annual average atmospheric stability values for each region are as follows.
The correlation coefficients between the year and the annual average atmospheric stability are -0.79 in Gwangju, -0.75 in Daegu, -0.80 in Daejeon, -0.76 in Busan, -0.28 in Seoul, and 0.56 in Incheon. Incheon has a clear positive correlation, Seoul has a weak negative correlation, and Gwangju, Daegu, Daejeon, and Busan have a strong negative correlation. Since the slope of the trendline of the graph of atmospheric stability in cities except Incheon is negative, it can be seen that the atmosphere becomes unstable as the year passes in the five regions. On the other hand, in Incheon, the slope of the trendline is positive, which means that the atmosphere is stabilizing.
When looking at the correlation between the annual average fine dust concentration by region and the annual average atmospheric stability by region, Gwangju 0.58, Daegu 0.73, Daejeon 0.50, Busan 0.69, Seoul 0.04, and Incheon -0.55. In other words, Daegu has a strong positive linear relationship, Gwangju, Daejeon, and Busan have a clear positive linear relationship, Seoul has a nearly negligible linear relationship, and Incheon has a clear negative linear relationship. Therefore, the atmosphere in Daegu, Gwangju, Daejeon, and Busan is becoming unstable, and the concentration of fine dust is also decreasing. On the other hand, it can be seen that the concentration of fine dust in Incheon is high even when the atmosphere becomes stable. In Seoul, there is little relationship between atmospheric stability and fine dust concentration.