ISENTROPIC TRAJECTORY ANALYSES OF POLLUTANT TRANSPORT IN NORTHEAST ASIA-INFLUENCE ON CHINA FROM NEIGHBORING COUNTRIES^*

The transport of air pollutants from several big cities in the north of China and the neighboring countries is researched by using the isentropic trajectory model. The trajectories are calculated twice daily for the cities in January, April. July and October for the period of 1992-1994. The statistical method has been used to deal with trajectory dots at intervals of 30 min forthe for ward and backward trajectories during 0-24 h and 24-48 h. The probability distribution diagrams of trajectory show clearly the ensemble properties of isentropic trajectories for each city and the dominant transport directions of pollutants. They possess notable seasonal variations. The forward trajectory areas of the Ulaan Baatar in Mongolia can spread over North China. and those of the Chita in Russia can influence Northeast China except in summer. In July the forward trajectory of Pyongyang and Seoul can extend northward to the boundaries of China.