Dust storm originate in the regions of northern and western China along with the Mongolian region, which includes Xinjiang, Gansu, Hetao, inner Mongolia, Mongolia, and other regions. The annual rain fall in this region is consistently below 400mm and seasonal division is highly uneven. This is the main source of dust storm that occur in east Asia. Winter and spring seasons are the main periods where dust storm occur, especially from the months of March to May which account for 60% of dust storm per year. The number of dust storm that occur annually are not uniform. The conditions of dust storm occurring are loose, dry soil without vegetation and no accumulated snow. When coupled with weather conditions such as strong ground winds, unstable vertical weather conditions and the lack of rain or snow fall, dust storm occur.
When large scale dust storm form, the abundance of sand in the atmosphere obstructs sunlight and reduces visibility to zero, while super strong dust storm are called black storms. When dust storm occur, larger sand particles usually affect the source or neighboring areas, then return to the earth; smaller particles of sand are transported upwards of 850-700 hPa which is approximately 1000-3000 meters, then carried by the west wind belt to the east. During transportation, a portion may be dispersed or dilluted causing the transportation distances to be even further; the lower density is caused in part by snow or rain fall which bring the particles back to earth. When moving east, the dust storm of northwestern China can affect Japan, Korea, or even Hawaii which is 10000 km away. They can also affect southern neighbors such as Taiwan, Hong Kong, or even the Phillipines; apparently, the affected areas are very wide. Even back in 479 and 700 A.D., there were records of dust storm invading Korea.
Studies show that sand from desert regions are the main source of suspended particles on the planet. The Sahara Desert itself accounts for 25% of the suspended micro particles in the atmosphere (Zhao and Yu, 1990). Northwest China resides in the desert region of central asia which is the runner up in the four major desert regions in the world (ranking is central Africa, central Asia, north America, and Australia); therefore, the influence of northerwestern China's desert region greatly impacts the atmospheric environment of east Asia. The conditions for dust storm are:
- Geographical Conditions: Loose, dry dirt with no vegetation and no snow.
- Climate Conditions: Strong winds on the ground, vertical and unstable weather conditions and the lack of rain or snow fall.
Winter (November to May) is east Asia's most likely season to have dust storm. Dust storm occur easily in dry desert regions when high pressure fronts move into regions to induced by geography or when low pressure fronts form to produce strong winds at ground level.