Sandstorms and/or duststorms that are affecting the Korean peninsula occur most frequently in the spring season in the arid and semi-arid area of sand deserts including Badainjaran, Tengger, Mu Us, Hunsandakue and Keoeolchin, Gobi region and Loess Plateau in the Asian continent. The area of Asian dust source regions cover most of northern China and Mongolia.
The traveling low-pressure systems accompanied with strong winds behind the associated cold fronts cause to raise dust into the atmosphere (Yellow Sand) resulting in visibility reduction of less than 1 ㎞ quite frequently.
The first record of the dust phenomenon in Korea is found in the reign of Silla Dynasty's King Ahdalla (174 A.D.). It was called "Woo-To". At that time, the people believed that the God in the heaven became so angry that they lashed down dirt instead of rain or snow. This is why, whenever the King or his subjects saw a dust phenomenon, they would be frightened.
In the reign of Baekje Dynasty's King Kungusu in 379 A.D., there was the following record in April: "Dust fell all day long." There was a record that the sky of the Baekje's capital was darkened like night by dustfall in march in the reign of King Mu (606 A.D.).
Although these dust phenomena mainly occur during the springtime, there were some records of them occurred in winter as well. During the reign of Goguryeo Dynasty's King Bojang in 644 A.D., it was recorded that there was a red snow that fell from the sky in October. We can guess that Asian Dust was mixed with snow at that time.
The definition of Asian Dust event was introduced in the 「Goryeosa」 as follow: "There was dirt on clothes without getting wet by rain." It was called "Mae () or To-Woo".
In the Joseon Dynasty(1392~1910 A.D.), there was the following record in March 22, 1549: "Dust fell in Seoul. At Jeonju and Namwon in the Jeolla province, located in the southwestern part of Korea, there was a fog that looked like smoke creeping into every corner in all directions. The tiles on the house roofs, grass on the fields and leaves on the trees were entirely covered by yellow-brown and white dusts. When the dust was swept, it wiped away like dirt, and when it was shaken, it dispersed, too. This weather condition lasted until March 25, 1549." This record clearly depicts the characteristics of a dust phenomenon in Korea.
The size of sand particles ranges 1-1,000 ㎛ in the source region. However, long-range transported particles size ranges 1-10 ㎛. The typical size of dust particles observed in Korea ranges 1-10 ㎛ during the Yellow Sand events. However, the size of particles quite depends upon the weather condition and the travelling distance from the source.
In order to forecast dust phenomena, the operational meteorological model, Regional Data Assimilation and Prediction System(RDAPS), used in the operational aerosol model developed by Prof. S. U. Park. The model results are compared with the monitored PM10 concentration in Seoul.
Advisory is issued when the hourly averaged dust(PM10) concentration is expected to exceed 400㎛/㎡ for over 2 hours.
Warning is issued when the hourly averaged dust(PM10) concentration is eixpected to exceed 800 ㎛/㎡ for over 2hours.