## 3 Results and Discussion  
### Satellite Images of Yellow Dust Transport  
COMS-AI (the Communication, Ocean and Meteorological Satellite, Korean Meteorological Administration (KMA)) satellite images were used to more accurately understand the real-time transport of yellow sand particles toward downwind regions. These images are very useful to verify the effect of dust particles raised from Gobi Desert passing through Beijing city, China on the local air quality of Gangneung city, Korea. Figure 2 shows the Korean COMS-AI satellite images reflecting dust which were originated from the Gobi Desert and spread in the Gobi Desert, within its vicinity, to Inner mongo of northern China and Beijing city, and to the northern Korean peninsula at 15:00 LST (Korean Local Standard Time = UTC + 9 h) 10 March 2015 (before dust period at Gangneung city). However, the yellow dusts did not reach Gangneung city. On the other hand, after the yellow dusts reached Gangneung city, the effect of yellow dust appeared in the city, showing rapid increases in PM\({}_{10}\), PM\({}_{2.5}\) and PM\({}_{1}\) concentrations, especially in the case of PM\({}_{10}\) at over 120 \(\upmu\)g/m\({}^{3}\) at 21:00 LST, 21 March, and 134.67 \(\upmu\)g/m\({}^{3}\) at 05:00 22 March. COMS satellite images in Figure 2 show the real-time transport of dusts raised from Gobi Desert, passing by Beijing city, China (B in Table 1) and finally reaching Gangneung city, Korea (G in Table 1) at 09:00 LST, 21 March (the starting day of the dust period). Thus, the air quality at Gangneung city can be greatly influenced by the transport of large dust particles of the Gobi Desert combined with air pollutants of Beijing city. This kind of transport pattern of the dusts continued near the end of the dust period until 00:00 LST, 23 March. Thus, except for the dust period, the air quality of this city with no factories depends upon its own pollutants from vehicles on the road and residential heating boilers. Hourly PM\({}_{10}\), PM\({}_{2.5}\) and PM\({}_{1}\) Concentrations before, during and after the Dust Periods  
In Figure 3, before the inflow of dusts from the Gobi Desert to Gangneung city (00:00 LST, March 18 to 00:00 LST, March 21), the minimum concentration of PM\({}_{10}\) (PM\({}_{2.5}\); PM\({}_{1}\)) was 28.83 \(\upmu\)g/m\({}^{3}\) (22.02 \(\upmu\)g/m\({}^{3}\); 15.92 \(\upmu\)g/m\({}^{3}\)) and its maximum was 82.17 \(\upmu\)g/m\({}^{3}\) (71.13 \(\upmu\)g/m\({}^{3}\); 57.95 \(\upmu\)g/m\({}^{3}\)) for each hour. In contrast, during the dust period, the minimum concentration of PM\({}_{10}\) (PM\({}_{2.5}\); PM\({}_{1}\)) was 34.90 \(\upmu\)g/m\({}^{3}\) (17.27 \(\upmu\)g/m\({}^{3}\); 9.75 \(\upmu\)g/m\({}^{3}\)) and its maximum was 134.67 \(\upmu\)g/m\({}^{3}\) (81.03 \(\upmu\)g/m\({}^{3}\); 64.42 \(\upmu\)g/m\({}^{3}\)), respectively. After the dust  
Figure 2: Korean COMS satellite images reflecting dusts at **(a)** 15:00 LST 20 March 2015 (before dust period at Gangneung city) and **(b)** 21:00 LST, 21 March (for dust period). Red small circle, small and big squares denote Gangneung (Korea), Beijing (China) and the Gobi Desert (M Mongolia). (The Korea Meteorological Administration (KMA) supplied the images.) ([[http://www.kma.go.kr](http://www.kma.go.kr)]([http://www.kma.go.kr](http://www.kma.go.kr)), accessed on 15 February 2021). period, the minimum concentration of PM\({}_{10}\) (PM\({}_{2.5}\); PM\({}_{1}\)) was 19.90 \(\upmu\)g/m\({}^{3}\) (1.93 \(\upmu\)g/m\({}^{3}\); 7.12 \(\upmu\)g/m\({}^{3}\)) and its maximum was 61.58 \(\upmu\)g/m\({}^{3}\) (48.25 \(\upmu\)g/m\({}^{3}\); 41.53 \(\upmu\)g/m\({}^{3}\)), slightly less than that before the dust period. Since most of the yellow dusts raised from the Gobi Desert and arid Inner Mongolia pass through Beijing city, China, by a northerly wind or northwesterly wind and reach Gangneung city in the eastern coast of Korea, the PM concentrations in Gangneung are directly affected by the PM concentrations of Beijing, containing much of the dusts originated from the Gobi Desert and arid area of northern China.