the sulfur cycle, and (c) to study the distributions and budgets of CO2, CH4, and N2O over eastern Asia and the western Pacific.
The first phase of PEM-West was completed in the fall of 1991. Scientific results were presented recently at the Western Pacific Conference held in Hong Kong and will be reported in various journals and other conferences over the next few years. A second phase is being planned for the spring of 1994. The background atmosphere stations in China have made some valuable measurements. However, the capabilities of these stations are severely limited by lack of funding and advanced instruments. Without additional support, the future of these stations is uncertain.
Current research in aerosol chemistry in China is more limited than in other areas of atmospheric chemistry. As discussed above, aerosol studies focus primarily on urban- and regional-scale problems. Only a few studies directly address global aerosol distributions and trends or link aerosols to climate change. From the information available to the panel, it appears that the importance of aerosols to climate change is not generally appreciated by researchers in China.
Wind-blown dust is believed to contribute significantly to particulate loading, especially in northern China (Yang et al. 1990). Dust storms carry not only soil mineral particles, but also air pollutants released from populated areas over which a dust cloud passes. These pollutants include sulfate, nitrate, soot carbon, trace metals, and organic compounds. During transport, several natural and pollution constituents may undergo chemical interaction and transformation and result in a complex aerosol mixture with atmospheric physics, chemistry, radiation, and other properties different from those of any single original soil mineral or pollution particulate constituent. Measurements of aerosols over China, Japan, and the northern Pacific have shown convincingly that dust storms originating from central Asia are the major sources of dust, sulfate, nitrate, and other particulate matter transported to the northern Pacific (Darzi and Winchester 1982, Iwasaka et al. 1988, Muayama 1988).
Given the important role played by aerosol particles in atmospheric radiation, the effect of Asian dust storms on regional—as well as global—climate needs to be carefully studied.2 CAMS has a program to study the meteorological characteristics of dust storms, including the formation and transport of the storm's dust. A comprehensive program that addresses the chemical as well as physical