March 31, 2007, marked opening ceremonies for the first “Green China Day,” established to increase awareness of the need for environmental protection. As reported by ShanghaiDaily.com, however, the ceremony in Beijing saw an unwelcome guest: Gobi Desert dust. Roughly 2,000 kilometers south of the capital city, air quality also suffered, in this case from fires in Southeast Asia.
The Ozone Monitoring Instrument (OMI) flying onboard the Aura satellite measures the thickness of light-absorbing aerosols—tiny solid or liquid particles suspended in the atmosphere. OMI captured these images on March 30 (top) and March 31 (bottom). The images superimpose a color-coded scale of aerosol thickness onto a natural-color image of eastern Asia, the Sea of Japan, and the western Pacific Ocean. These images track the eastward movement of aerosols into the Beijing region, and show aerosols blowing eastward out of Southeast Asia, dissipating as they travel. Red areas indicate where aerosols are thickest or where aerosols float over reflective clouds, which tend to make the aerosol concentration appear more intense than it actually is.
Aerosols south of 30 degrees latitude likely result from smoke from biomass burning. To the north, aerosols probably result from dust. In both cases, the time of year plays a role. Southeast Asian farmers often prepare for the growing season by setting agricultural fires each spring. Accidental fires also spring up readily at this time of year. Meanwhile, Gobi Desert dust storms generally peak in the spring then gradually decline throughout the summer. The March 31 dust storm that blanketed Beijing marked the first such storm of 2007.
Images and interpretation courtesy Colin Seftor and Omar Torres, Aura Science Team.
