# Multivariate Regression Modeling for Coastal Urban Air Quality Estimates
## 3 Results  
### Satellite Images of Yellow Dust Transport  
We used GONE-2 (METOP-B) KNMI/O3 MAF/EUMETSAT satellite images reflecting a cloud of dust before and during yellow sand periods in 2015 to investigate the transport of yellow dust from northern China, including desert and dry areas, to the downwind regions, such as South China, Korea and Japan, in the dust transport route in Figure 2a,b. Figure 2a shows that the GONE-2 (METOP-B) satellite images can reflect the yellow sand and dust initially raised from the arid areas in the east of Lake Baikal in Siberia (Russia), the Gobi Desert and Inner Mongo in northern China. Then, the dust clouds move toward eastern China, extending to southern China at the same time on 18 March. After that, on 19 March, as shown in Figure 2a, the dust clouds moved further eastward and passed by Beijing and Tianjin, with the dust belt extended to southern China and Vietnam. However, the yellow dust did not reach the Korean peninsula, including the Korean east coast and Kangnung. Another dust belt was detected from Hokkaido in northern Japan to Honshu in the middle of Japan that extended to the east of the Philippines. In Figure 2b, the METOP-B images show the dust belt from Vladivostok (Russia) to the Korean peninsula, including its east coast (Kangnung city, Republic of Korea), Kyusu Island (Japan), Taiwan and Luzon Island (Philippines) on 22 March, when PM\({}_{10}\) concentration was very high at Kangnung during the yellow sand event from 00:01 LST, 21 March to 00:00 LST, 23 March. This dust belt is attributed to the transport of the previous dust belt that was on the line of Beijing-southern China-Vietnam on 19 March in Figure 2a. Hourly PM\({}_{10}\), PM\({}_{2.5}\) and PM\({}_{1}\) Concentrations before, during and after the Dust Periods  
Figures 3 and 4 indicate the hourly distribution of PM (PM\({}_{10}\) and PM\({}_{2.5}\)) and gas (SO\({}_{2}\), CO, O\({}_{3}\) and NO\({}_{2}\)) concentrations and meteorological parameters (air temperature, wind speed and relative humidity) at the Okcheondong observation point in Kangnung (Korea). Figure 5 also indicates the hourly distribution of PM (PM\({}_{10}\) and PM\({}_{2.5}\)) and gas (SO\({}_{2}\), CO, O\({}_{3}\) and NO\({}_{2}\)) concentrations at the Yongdingmen observation point in Beijing (China). Figure 2: GONE-2 (METOP-B) KNMI/O3 MSAF/EUMETSAT satellite images reflecting a cloud of dust on (**a**) 19 March 2015 (before) and (**b**) 22 March (during the period of the yellow sand event in Korea). Small blue squares and circles denote Beijing (China) and Kangnung (Korea). ([[https://www.temis.nl/aviation/aai-archive.php?Year=2015&Month=03&Day=19](https://www.temis.nl/aviation/aai-archive.php?Year=2015&Month=03&Day=19)]([https://www.temis.nl/aviation/aai-archive.php?Year=2015&Month=03&Day=19](https://www.temis.nl/aviation/aai-archive.php?Year=2015&Month=03&Day=19)), accessed on 25 February 2023). [PERSON] and [PERSON] [17] indicated that the transportation of pollutants from Beijing (China) to Kangnung (Korea) takes about two days via a northwesterly wind of about 10 m/s. Thus, PM and gas pollutants for the second sand period in Beijing in Figure 5 may contribute to pollutant concentrations in Kangnung two days later in Figure 3. Thus, PM concentrations for the yellow sand event (on 00 LST, 21 March to 00 LST, 23 March) detected at the Okcheondong observation point in Kangnung could have been affected by PM and gaseous pollution at the Yongdingmen observation point in Beijing two days earlier (00 LST, 19 March to 00 LST, 21 March), corresponding to the second yellow sand period in Beijing.