干旱区生态环境知识资源中心

Intense measurements on a giant dust event sweeping over the Asian continent during springtime were conducted in Beijing from 16 to 20 April 2006. Beijing suffered from a large amount of mineral dust transported long range from upwind regions, identified as the desert areas of Mongolia and Inner Mongolia. During the prime time of dust event, hourly PM10 concentrations increased drastically to 1200 mu g/m(3), corresponding to the lowest visibility of 3 km. The mass concentrations of major crustal elements in aerosols during dusty days were nearly double those of nondusty days. The quasistationary front had great contributions to the formation of severe dusty days over Beijing because of an equiponderant confluence of northern cold air masses from a Siberian anticyclone and southern warm air masses. During the dust event, northeast jets below the convective atmosphere boundary layer occurred at multilevel heights of 50-65 m, 100-160 m, and 160-260 m, with the highest wind speed exceeding 14 m s(-1). Humidity inversions usually occurred at heights of 160-240 m, 60-140 m, and 5-30 m due to the cold air horizontal advection. The enhancement of dust loadings in the atmosphere of Beijing during the dust event resulted in a cooling effect by -62.0 W m(-2) radiative forcing at the top of atmosphere.