The China Project's atmospheric research is committed to building observationally validated, fundamental research on the physical and chemical dimensions of China’s atmospheric environment and the emissions that influence it, from urban to global scales. In addition to the model-based research described below, it includes observational research described here. It is also a core component of a Project-wide interdisciplinary framework now being applied to evaluation of national GHG and pollution control policies, described here.

The primary tool is the GEOS-Chem global chemical transport model developed at Harvard, and a nested, high-resolution window over China developed by WANG Yuxuan (Tsinghua University Department of Environmental Science and Engineering, formerly Harvard) and China Project chair Michael B. McElroy (Harvard School of Engineering and Applied Sciences, HSEAS, and the Department of Earth and Planetary Sciences). Post-doctoral fellow LIN Jintai (HSEAS) also now tests, develops, and applies the GEOS-Chem China model in his work,  drawing on his research experience in the science and structure of alternative chemical tracer models.

Validated by agreement of modeled concentrations with measurements made by ground stations and offshore aircraft, the model differentiates air transport mechanisms for individual sub-regions of China on a finer scale than previously possible (Wang et al. 2004a) and captures critical seasonal effects of meteorology—notably cold fronts in winter and monsoonal patterns in summer—on regional and urban air quality.

Applied in inverse mode—in which atmospheric concentrations observed by ground stations, aircraft, and satellites are use to derive optimized emissions—the model provides independent checks on “bottom-up” inventories of carbon monoxide (CO), nitrogen oxides (NOX), other pollutants, and greenhouse gases. Collaborating with WANG Tao (Hong Kong Polytechnic University, Department of Civil and Structural Engineering; Chinese Research Academy of Environmental Sciences, Beijing), the team has estimated that official estimates of emissions of CO and NOX in 2001 should be raised as much as 43% and 47%, respectively, to explain the levels observed in the atmosphere (Wang et al. 2004b). Another paper proposes that the discrepancy for NOX may be explained by processes largely overlooked previously: the mobilization of nitrogen though the management of human and animal wastes and the use of chemical fertilizers, oxidized in part to NOX by bacterial action (McElroy and Wang 2005). This proposition of a large biological source of NOX over rural areas in China is supported also by satellite observations of column NO2 (Wang et al. 2007a).

These capabilities can inform emission control policies. For a given region, if biological sources of NOX—a main precursor of health-endangering secondary pollutants including fine particles and ozone—approach the total contribution from fossil fuel combustion, pollution control strategies may need to be broadened in directions unanticipated by experience in the differing conditions of western countries: waste management and agricultural practices.

An inverse application to near-real-time satellite observations of atmospheric concentrations yielded encouraging evidence to officials preparing for the Beijing Olympics in 2008. It shows that measures to restrict vehicular traffic in Beijing during the Sino-African Summit of November of 2006 had the intended effect: a large reduction of NOX emissions, as much as 40%, during the period in which the restrictions were in place (Wang et al. 2007b). The figure above compares model estimates and observations, illustrating the capability of the GEOS-Chem China model to capture local variation in NO2 column concentrations. The natural experiment of the Sino-African summit thus has had both practical and scientific value, serving to validate the efficacy of emission control policies and the Project's atmospheric model itself. The results of the Sino-African summit paper were reported on the online news of Science and in other science and general news media, and were cited by Beijing authorities in news conferences prior to the Olympics.

A paper in Atmospheric Chemistry and Physics (ACP) uses station data to investigate variations of O3 and CO in summertime in the Beijing area (Wang et al. 2008). It demonstrates a decline in conditions conducive to O3 formation in August compared to June and July, attributable to increased cloudiness from monsoonal climate patterns.

Chen et al. 2009, in ACP, adapts the GEOS-Chem China model to new assimilated meteorological data now available, improving the spatial resolution of the model to 0.5 X 0.67 degrees (Chen et al. 2009).

A new paper in ACP (Wang et al. 2009) uses this higher-resolution version of GEOS-Chem China and data from the Miyun station to differentiate how much of reduced ozone levels observed during the Beijing Olympics can be attributed to policy-driven restrictions of emissions, and how much to natural meteorological conditions.

Another new paper (Lin et al. 2009, submitted to ACP) has developed a new approach to constraining Chinese anthropogenic emissions of NOx from four major emitting sectors. It combines tropospheric NO2 column retrievals from two satellites in July 2008, taking advantage of their different passing times over China and explicitly accounting for diurnal variations in anthropogenic emissions as well as variations in tropospheric lifetimes.

The GEOS-Chem China model is also part of the "grand collaboration" initiated to link all of the China Project's major research capacities for assessment of the costs and benefits -- in economic, greenhouse gas, air quality,  human health, and agricultural terms -- of emission control and energy policy options in China. This new effort is described in a separate link here.