Sumeeta Srinivasan. 2010. “Linking travel behavior and location in Chengdu, China: A geographically weighted approach.” Transportation Research Record, 2193, Pp. 85-95. Publisher's VersionAbstract
This study uses geographically weighted regressions and multilevel models to understand the implications of location and attitudinal characteristics for travel behavior in Chengdu, China. In particular, the estimated distance traveled and the mode choice of nonmotorized versus motorized vehicles for work- and school-related trips were examined by using a recent household trip diary data set. The results suggest that location characteristics may be influential in the prediction of travel behavior but cannot be fully captured by simple categorization such as inner ring location versus peripheral location. Variations in travel behavior can be related to socioeconomic and location variables in ways that vary by location in a complex manner. Policy makers should therefore reconsider the role that location and attitudinal implications may play in meeting travel demand in rapidly developing cities like Chengdu.
Jieping Li, Joan L Walker, Sumeeta Srinivasan, and William P Anderson. 2010. “Modeling private car ownership in China: Investigating the impact of urban form across mega-cities.” Transportation Research Record , 2193, Pp. 76-84. Publisher's VersionAbstract
The rising prevalence of private cars in the developing world is causing serious congestion and pollution. In China, private cars started to emerge as an important travel mode in the past decade. Prospective research on the relationship between urban form and car ownership is relatively uncommon in the developing world, and China offers a unique study opportunity, given the tremendous increases in private cars and fast-paced urbanization over the past decade. This study investigates the influence of urban form on car ownership as well as the impact of other socioeconomic and demographic factors on private car ownership across megacities in China. Analysis was conducted through the use of data from 36 megacities and two household survey data sets collected in Beijing and the city of Chengdu, China. Ordinary least squares regression and discrete choice models were employed to execute the aggregate and disaggregate analysis of the urban form impact on private car ownership across cities. The statistical model results demonstrate that urban affluence, urban scale, and road infrastructure supply factors have significant positive effects on the city level of private car ownership across cities. Population density calculated at the subdistrict level, however, had a significant negative effect on private car ownership across cities. Households with private cars were found to prefer to live close to urban centers where amenities were readily available. The results provide evidence for urban planners and policy makers.

This paper uses data from the Project's household survey in Chengdu, Sichuan.

Jintai Lin, Chris P Nielsen, Yu Zhao, Yu Lei, Yang Liu, and Michael B. McElroy. 2010. “Recent changes in particulate air pollution over China observed from space and ground: Effectiveness of emission control.” Environmental Science and Technology, 44, 20, Pp. 7771-7776. Publisher's VersionAbstract
The Chinese government has moved aggressively since 2005 to reduce emissions of a number of pollutants including primary particulate matter (PM) and sulfur dioxide (SO2), efforts inadvertently aided since late 2008 by economic recession. Satellite observations of aerosol optical depth (AOD) and column nitrogen dioxide (NO2) provide independent indicators of emission trends, clearly reflecting the sharp onset of the recession in the fall of 2008 and rebound of the economy in the latter half of 2009. Comparison of AOD with ground-based observations of PM over a longer period indicate that emission-control policies have not been successful in reducing concentrations of aerosol pollutants at smaller size range over industrialized regions of China. The lack of success is attributed to the increasing importance of anthropogenic secondary aerosols formed from precursor species including nitrogen oxides (NOx), non-methane volatile organic compounds (NMVOC), and ammonia (NH3).
Joan L Walker, Jieping Li, Sumeeta Srinivasan, and Denis Bolduc. 2010. “Travel demand models in the developing world: Correcting for measurement errors.” Transportation Letters, 2, 4, Pp. 231-243. Publisher's VersionAbstract
While transport modelers in developed countries are accustomed to working with relatively rich datasets including transport networks and land use data, such databases are rarely available in developing countries. However, developing countries such as China with its immense rate of economic growth are, arguably, most in need of demand models. The research addressed in this paper is how to develop mode choice models for planning and policy analysis when high quality level of service data are not available. The research makes use of a 1,001 household travel and activity survey from Chengdu collected by the China Project at Harvard University in 2005. Chengdu has an urban population of over 3 million and a GDP growth rate of over 20% per year. The survey contains a rich array of self-assessed information on available modes and accessibility and also includes a number of attitudinal questions. The approach taken here is to treat level of service as a latent (i.e., unobservable) variable. Measurement equations (from the structural equation model paradigm) are used to infer latent level of service, and these equations are integrated with the mode choice model. Our initial results indicate that models that do not correct for measurement error may significantly underestimate travelers' values of time. The methodological approach employed has potential for improving models estimated with higher quality network data, because it can correct for measurement error that exists, for example, in network-derived level of service variables.

This paper is based on data from the Project's household survey in Chengdu, Sichuan.

Yuxuan Wang, Michael B. McElroy, J. William Munger, Jiming Hao, Hong Ma, and Chris P Nielsen. 2010. “Year-round measurements of O3 and CO at a rural site near Beijing: Variations in their correlations.” Tellus B: Chemical and Physical Meteorology, 62, 4, Pp. 228-241. Publisher's VersionAbstract
We examine seasonal variations of carbon monoxide (CO), ozone (O3), and their relationships observed over the course of 3 yr (2005–2007) at Miyun, a rural site 100 km north of Beijing. Monthly mean afternoon mixing ratios of CO have broad maxima in winter and a secondary peak in June. Monthly mean afternoon O3 shows a clear seasonal pattern with a major peak in June (85 ppb), a secondary peak in September (65 ppb) and minimum in winter (50–55 ppb). The seasonal cycles of O3 and CO are associated with seasonal changes in dominant synoptic pattern. Substantial interannual variability is found for CO which is attributed to the interannual variability of meteorology and emissions from biomass burning. The seasonality and magnitude of background CO and O3 derived at Miyun are consistent with observations at upwind remote continental sites. The O3–CO correlation slope is about 0.07 ppb ppb−1 on average in summer, significantly lower than the typical slope of 0.3 ppb ppb−1 reported for developed countries. The O3–CO correlation slope shows large gradients for different types of air masses (0.133 ± 0.017 ppb ppb−1 in aged urban pollution plumes and 0.047 ± 0.008 ppb ppb−1 in biomass burning plumes), suggesting that the conventional method of direct scaling the mean O3–CO slope by CO emissions to deduce O3 production rate is subject to large uncertainties if applied for China.
Jieping Li. 2009. “Application of latent variables in transport planning models.” Department of Geography and Environment, Boston University. Publisher's Version
Jing Cao, Richard Garbaccio, and Mun S Ho. 2009. “China's 11th Five-Year Plan and the environment: Reducing SO2 emissions.” Review of Environmental Economics and Policy, 3, 2, Pp. 189-208. Publisher's VersionAbstract
China's rapid economic growth has been accompanied by a high level of environmental degradation. One of the major sources of health and ecosystem damages is sulfur dioxide (SO2). Reducing SO2 emissions is a priority of China's environmental authorities, and the 11th Five-Year Plan (2006–2010) includes the target of reducing total SO2 emissions by 10 percent from the 2005 level. Given the rapid increase in SO2 emissions that is expected to occur in absence of intervention, attaining this target will require a significant effort. This article examines the two major policy measures the government is taking to achieve the SO2 target: a shutdown of many small, inefficient power plants and the installation of desulfurization equipment on existing and new coal-fired plants. We present results from a joint U.S.–China study that we participated in, which estimated the costs and benefits of these policies. We then estimate the economy-wide impacts of the two policies using a multisector model of the Chinese economy. We find that in the aggregate, the economic benefits of the shutdown of the small power plants are large enough to offset the costs of the desulfurization equipment, even without considering the substantial environmental benefits from the reduction of emissions of SO2 and other pollutants.
Xiaoqi Guo and James K Hammitt. 2009. “Compensating wage differentials with unemployment: Evidence from China.” Environmental and Resource Economics, 42, 2, Pp. 187-209. Publisher's VersionAbstract
We estimate the economic value of mortality risk in China using the compensating-wage-differential method. We find a positive and statistically significant correlation between wages and occupational fatality risk. The estimated effect is largest for unskilled workers. Unemployment reduces compensation for risk, which suggests that some of the assumptions under which compensating wage differentials can be interpreted as measures of workers’ preferences for risk and income are invalid when unemployment is high. Workers may be unwilling to quit high-risk jobs when alternative employment is difficult to obtain, violating the assumption of perfect mobility, or some workers (e.g., new migrants) may be poorly informed about between-job differences in risk, violating the assumption of perfect information. These factors suggest our estimates of the value per statistical life (VSL) in China, which range from approximately US$30,000 to US$100,000, may be biased downward. Alternative estimates adjust for heterogeneity of risk within industry by assuming that risk is concentrated among low-skill workers. These estimates, which are likely to be biased downward, range from US$7,000 to US$20,000.

This study developed a new approach to the valuation of health risk in China, for monetizing health damages of environmental degradation.

Youn Daeok, Kenneth O Patten, Jin-Tai Lin, and Donald J. Wuebbles. 2009. “Explicit calculation of indirect global warming potentials for halons using atmospheric models.” Atmospheric Chemistry and Physics, 9, 22, Pp. 8719-8733. Publisher's VersionAbstract
The concept of Global Warming Potentials
(GWPs) has been extensively used in policy consideration
as a relative index for comparing the climate impact of an
emitted greenhouse gas (GHG), relative to carbon dioxide
with equal mass emissions. Ozone depletion due to emission
of chlorinated or brominated halocarbons leads to cooling
of the climate system in the opposite direction to the direct
warming contribution by halocarbons as GHGs. This
cooling is a key indirect effect of the halocarbons on climatic
radiative forcing, which is accounted for by indirect GWPs.
With respect to climate, it is critical to understand net influences
considering direct warming and indirect cooling effects
especially for Halons due to the greater ozone-depleting efficiency
of bromine over chlorine. Until now, the indirect
GWPs have been calculated using a parameterized approach
based on the concept of Equivalent Effective Stratospheric
Chlorine (EESC) and the observed ozone depletion over the
last few decades. As a step towards obtaining indirect GWPs
through a more robust approach, we use atmospheric models
to explicitly calculate the indirect GWPs of Halon-1211
and Halon-1301 for a 100-year time horizon. State-of-theart
global chemistry-transport models (CTMs) were used as
the computational tools to derive more realistic ozone depletion
changes caused by an added pulse emission of the
two major Halons at the surface. The radiative forcings on
climate from the ozone changes have been calculated for indirect
GWPs using an atmospheric radiative transfer model
(RTM). The simulated temporal variations of global average
total column Halons after a pulse perturbation follow an exponential
decay with an e-folding time which is consistent
with the expected chemical lifetimes of the Halons. Our cal-
Correspondence to: D. J. Wuebbles
culated indirect GWPs for the two Halons are much smaller
than those from past studies but are within a single standard
deviation of WMO (2007) values and the direct GWP values
derived agree with the published values. Our model-based
assessment of the Halon indirect GWPs thus confirms the
significant importance of indirect effects on climate.
Xi Lu, Michael B. McElroy, and Juha Kiviluoma. 2009. “Global potential for wind generated electricity.” Proceedings of the National Academy of Sciences, 106, 27, Pp. 10933-10938s. Publisher's VersionAbstract

The potential of wind power as a global source of electricity is assessed by using winds derived through assimilation of data from a variety of meteorological sources. The analysis indicates that a network of land-based 2.5-megawatt (MW) turbines restricted to nonforested, ice-free, nonurban areas operating at as little as 20% of their rated capacity could supply >40 times current worldwide consumption of electricity, >5 times total global use of energy in all forms. Resources in the contiguous United States, specifically in the central plain states, could accommodate as much as 16 times total current demand for electricity in the United States. Estimates are given also for quantities of electricity that could be obtained by using a network of 3.6-MW turbines deployed in ocean waters with depths <200 m within 50 nautical miles (92.6 km) of closest coastlines.

Wind power accounted for 42% of all new electrical capacity added to the United States electrical system in 2008 although wind continues to account for a relatively small fraction of the total electricity-generating capacity [25.4 gigawatts (GW) of a total of 1,075 GW] (ref. 1; The Global Wind Energy Council projected the possibility of a 17-fold increase in wind-powered generation of electricity globally by 2030 (ref. 2; Short et al. (3), using the National Renewable Energy Laboratory's WinDs model, concluded that wind could account for as much as 25% of U.S. electricity by 2050 (corresponding to an installed wind capacity of ≈300 GW).

Archer and Jacobson (4) estimated that 20% of the global total wind power potential could account for as much as 123 petawatt-hours (PWh) of electricity annually [corresponding to annually averaged power production of 14 terawatts (TW)] equal to 7 times the total current global consumption of electricity (comparable to present global use of energy in all forms). Their study was based on an analysis of data for the year 2000 from 7,753 surface meteorological stations complemented by data from 446 stations for which vertical soundings were available. They restricted their attention to power that could be generated by using a network of 1.5-megawatt (MW) turbines tapping wind resources from regions with annually averaged wind speeds in excess of 6.9 m/s (wind class 3 or better) at an elevation of 80 m. The meteorological stations used in their analysis were heavily concentrated in the United States, Europe, and Southeastern Asia. Results inferred for other regions of the world are subject as a consequence to considerable uncertainty.

The present study is based on a simulation of global wind fields from version 5 of the Goddard Earth Observing System Data Assimilation System (GEOS-5 DAS). Winds included in this compilation were obtained by retrospective analysis of global meteorological data using a state-of-the-art weather/climate model incorporating inputs from a wide variety of observational sources (5), including not only surface and sounding measurements as used by Archer and Jacobson (4) but also results from a diverse suite of measurements and observations from a combination of aircraft, balloons, ships, buoys, dropsondes and satellites, in short the gamut of observational data used to provide the world with the best possible meteorological forecasts enhanced by application of these data in a retrospective analysis. The GEOS-5 wind field is currently available for the period 2004 to the present (March 20, 2009) with plans to extend the analysis 30 years back in time. The GEOS-5 assimilation was adopted in the present analysis to take advantage of the relatively high spatial resolution available with this product as compared with the lower spatial resolutions available with alternative products such as ERA-40, NECP II, and JRA-25. It is used here in a detailed study of the potential for globally distributed wind-generated electricity in 2006.

We begin with a description of the methodology adopted for the present study. The land-based turbines envisaged here are assumed to have a rated capacity of 2.5 MW with somewhat larger turbines, 3.6 MW, deployed offshore, reflecting the greater cost of construction and the economic incentive to deploy larger turbines to capture the higher wind speeds available in these regions. In siting turbines over land, we specifically excluded densely populated regions and areas occupied by forests and environments distinguished by permanent snow and ice cover (notably Greenland and Antarctica). Turbines located offshore were restricted to water depths <200 m and to distances within 92.6 km (50 nautical miles) of shore.

These constraints are then discussed, and results from the global analysis are presented followed by a more detailed discussion of results for the United States.

Jing Cao, Mun S Ho, Dale W Jorgenson, Rouen Ren, Linlin Sun, and Ximing Yue. 2009. “Industrial and aggregate measures of productivity growth in China, 1982-2000.” Review of Income Wealth , 55, s1, Pp. 485-513. Publisher's VersionAbstract
We estimate productivity growth for 33 industries covering the entire Chinese economy using a time series of input–output tables covering 1982–2000. Capital input is measured using detailed investment data by asset and labor input uses demographic information from household surveys. We find a wide range of productivity performance at the industry level. We then show how these industry growth accounts may be consistently aggregated to deliver a decomposition of aggregate GDP growth. For the 1982–2000 period aggregate TFP growth was 2.5 percent per year; decelerating from a rapid rate in the early 1980s to negative growth during 1994–2000. The main source of growth during the 1982–2000 period was capital accumulation, with a small negative contribution from the reallocation of factors across industries.
Jing Cao, Mun S Ho, and Dale W Jorgenson. 2009. “The local and global benefits of green tax policies in China.” Review of Environmental Economics and Policy, 3, 2, Pp. 231-250. Publisher's VersionAbstract
This article describes a multidisciplinary study of market-based policies for controlling air pollution in China. While previous studies have examined the costs and benefits of pollution control separately, this approach determines them together using an economy–environment model for China. We employ air dispersion simulations and population maps to calculate health damages due to air pollution. This provides estimates of incremental damages for industry output and fuel use. Based on these marginal damages, we simulate the effect of “green taxes” on the economy and show that the environmental benefits exceed the aggregate costs, ignoring adjustment costs for individual sectors.
Yuxuan Wang, Jiming Hao, Michael B. McElroy, J. William Munger, Hong Ma, Dan Chen, and Chris P Nielsen. 2009. “Ozone air quality during the 2008 Beijing Olympics: Effectiveness of emission restrictions.” Atmospheric Chemistry and Physics, 9, 14, Pp. 5237-5251. Publisher's VersionAbstract
A series of aggressive measures was launched by the Chinese government to reduce pollutant emissions from Beijing and surrounding areas during the Olympic Games. Observations at Miyun, a rural site 100 km downwind of the Beijing urban center, show significant decreases in concen-trations of O3, CO, NOy, and SO2 during August 2008, rel-ative to August 2006–2007. The mean daytime mixing ratio of O3 was lower by about 15 ppbv, reduced to 50 ppbv, in August 2008. The relative reductions in daytime SO2, CO, and NOy were 61%, 25%, and 21%, respectively. Changes in SO2 and in species correlations from 2007 to 2008 indicate that emissions of SO2, CO, and NOx were reduced at least by 60%, 32%, and 36%, respectively, during the Olympics. Analysis of meteorological conditions and interpretation of observations using a chemical transport model suggest that although the day-to-day variability in ozone is driven mostly by meteorology, the reduction in emissions of ozone pre-cursors associated with the Olympic Games had a signifi-cant contribution to the observed decrease in O3 during Au-gust 2008, accounting for 80% of the O3 reduction for the month as a whole and 45% during the Olympics Period (8–24 August). The model predicts that emission restrictions such as those implemented during the Olympics can affect O3 far beyond the Beijing urban area, resulting in reductions in boundary layer O3 of 2–10 ppbv over a large region of the North China Plain and Northeastern China.
Potential for wind generated electricity in China
Michael B. McElroy, Xi Lu, Chris P Nielsen, and Yuxuan Wang. 2009. “Potential for wind generated electricity in China.” Science, 325, 5946, Pp. 1378-1380. Publisher's VersionAbstract
Wind offers an important alternative to coal as a source of energy for generation of electricity in China with the potential for substantial savings in carbon dioxide emissions. Wind fields derived from assimilated meteorological data are used to assess the potential for wind-generated electricity in China subject to the existing government-approved bidding process for new wind farms. Assuming a guaranteed price of 0.516 RMB (7.6 U.S. cents) per kilowatt-hour for delivery of electricity to the grid over an agreed initial average period of 10 years, it is concluded that wind could accommodate all of the demand for electricity projected for 2030, about twice current consumption. Electricity available at a concession price as low as 0.4 RMB per kilowatt-hour would be sufficient to displace 23% of electricity generated from coal.

Final Manuscript in DASH
This paper was the cover article of this issue of Science; click here ( to see the cover image of wind turbines near the Great Wall of China.

Dan Chen, Yuxuan Wang, Michael B. McElroy, Kebin He, Robert M Yantosca, and Phillipe Le Sager. 2009. “Regional CO pollution in China simulated by the high-resolution nested-grid GEOS-Chem model.” Atmospheric Chemistry and Physics, 9, 11, Pp. 3825-3839. Publisher's VersionAbstract
An updated version of the nested-grid GEOS-Chem model is developed allowing for higher horizontal (0.5×0.667) resolution as compared to global models. CO transport over a heavily polluted region, the Beijing-Tianjin-Hebei (BTH) city cluster in China, and the pattern of outflow from East China in summertime are investigated. Compari-son of the nested-grid with global models indicates that the fine-resolution nested-grid model is capable of resolving in-dividual cities with high associated emission intensities. The nested-grid model indicates the presence of a high CO col-umn density over the Sichuan Basin in summer, attributable to the low-level stationary vortex associated with the Basin’s topographical features. The nested-grid model provides good agreement also with measurements from a suburban monitor-ing site in Beijing during summer 2005. Tagged CO simula-tion results suggest that regional emissions make significant contributions to elevated CO levels over Beijing on polluted days and that the southeastward moving cyclones bringing northwest winds to Beijing are the key meteorological mech-anisms responsible for dispersion of pollution over Beijing in summer. Overall CO fluxes to the NW Pacific from Asia are found to decrease by a factor of 3–4 from spring to sum-mer. Much of the seasonal change is driven by decreas-ing fluxes from India and Southeast Asia in summer, while fluxes from East China are only 30% lower in summer than in spring. Compared to spring, summertime outflow from Chi-nese source regions is strongest at higher latitudes (north of 35 N). The deeper convection in summer transporting CO to higher altitudes where export is more efficient is largely responsible for enhanced export in summer.
Yu Zhao, Lei Duan, Jia Xing, Thorjorn Larssen, Chris P Nielsen, and Jiming Hao. 2009. “Soil acidification in China: Is controlling SO2 emissions enough?” Environmental Science and Technology, 43, 21, Pp. 8021-8026. Publisher's VersionAbstract
Facing challenges of increased energy consumption and related regional air pollution, China has been aggressively implementing flue gas desulfurization (FGD) and phasing out small inefficient units in the power sector in order to achieve the national goal of 10% reduction in sulfur dioxide (SO2) emissions from 2005 to 2010. In this paper, the effect of these measures on soil acidification is explored. An integrated methodology is used, combining emission inventory data, emission forecasts, air quality modeling, and ecological sensitivities indicated by critical load. National emissions of SO2, oxides of nitrogen (NOX), particulate matter (PM), and ammonia (NH3) in 2005 were estimated to be 30.7, 19.6, 31.3, and 16.6 Mt, respectively. Implementation of existing policy will lead to reductions in SO2 and PM emissions, while those of NOX and NH3 will continue to rise, even under tentatively proposed control measures. In 2005, the critical load for soil acidification caused by sulfur (S) deposition was exceeded in 28% of the country’s territory, mainly in eastern and south-central China. The area in exceedance will decrease to 26% and 20% in 2010 and 2020, respectively, given implementation of current plans for emission reductions. However, the exceedance of the critical load for nitrogen (N, combining effects of eutrophication and acidification) will double from 2005 to 2020 due to increased NOX and NH3 emissions. Combining the acidification effects of S and N, the benefits of SO2 reductions during 2005−2010 will almost be negated by increased N emissions. Therefore abatement of N emissions (NOX and NH3) and deposition will be a major challenge to China, requiring policy development and technology investments. To mitigate acidification in the future, China needs a multipollutant control strategy that integrates measures to reduce S, N, and PM.
Rui Wang. 2009. “The structure of Chinese urban land prices: Estimates from benchmark land price data.” Journal of Real Estate Finance and Economics, 39, 1, Pp. 24-38. Publisher's VersionAbstract
Taking the recent benchmark land prices published by the Chinese city governments, the paper estimates commercial and residential land price curves of Chinese cities using cross-sectional data, controlling for urban population size and income level. The urban land leasing price–distance relationship is estimated based on the argument that monocentric urban structure is representative for Chinese cities. Both population size and income level are found to positively affect urban land price and price–distance gradients. Commercial land prices are higher than residential land prices except in suburbs or outer central urban areas, where the land prices of different uses converge. In most situations, commercial use price gradients are larger than those of residential use.
Rui Wang. 2008. “Autos, transit and bicycles: Transport choices in Chinese cities.” Kennedy School of Government, Harvard University.
Peter Rogers and Sumeeta Srinivasan. 2008. “Comparing sustainable cities—Examples from China, India and the USA.” In Sustainable urban development in China: Wishful thinking or reality?, edited by Marco Keiner. Munster, Germany: Verlagshaus Monsenstein und Vannerdat OHG. Publisher's VersionAbstract
Due to an unprecedented economic
growth, fuelled by a pro-growth policy,
China’s cities are mushrooming.

In the coming years, the mass migration
from rural to urban areas will continue.

The demand for energy and resources will
continue to rise.

China’s cities will increasingly contribute
to global warming and the depletion of
the environment.

The crucial question is: Can urban development
in China become sustainable?
Jin-Tai Lin, Daeok Youn, Xin-Zhong Liang, and Donald J. Wuebbles. 2008. “Global model simulation of summertime U.S. ozone diurnal cycle and its sensitivity to PBL mixing, spatial resolution, and emissions.” Atmospheric Environment, 41, 36, Pp. 8470-8483. Publisher's VersionAbstract
Simulation of summertime U.S. surface ozone diurnal cycle is influenced by the model representation of planetary boundary layer (PBL) mixing, spatial resolution, and precursor emissions. These factors are investigated here for five major regions (Northeast, Midwest, Southeast, California, and Southwest) by using the Model for Ozone And Related chemical Tracers version 2.4 (MOZART-2.4), with important modifications, to conduct sensitivity experiments for summer 1999 with three PBL mixing schemes, two horizontal resolutions and two emissions datasets. Among these factors, the PBL mixing is dominant. The default non-local scheme well reproduces the observed ozone diurnal variation, where the timing for the afternoon maximum and the morning minimum is within 1 h of the observed; biases for the minimum are less than 5 ppb except over the Southeast; and the ozone maximum–minimum contrast (OMMC) is within 10 ppb of observations except for the overprediction by 18.9 ppb over the Northeast. In contrast, the local scheme significantly overestimates the OMMC by 10–34 ppb over all regions as ozone and precursors are trapped too close to the ground. On the other hand, the full-mixing assumption underestimates the OMMC by 0–25 ppb, except over the Northeast, as the nighttime ozone decline is greatly underpredicted. As compared to PBL mixing, the effects of horizontal resolutions and precursor emissions being used are smaller but non-negligible. Overall, with the non-local mixing scheme, relatively high horizontal resolution (∼1.1°) and updated emissions data, the modified MOZART is capable of simulating the main features of the observed ozone diurnal cycle.

This paper identifies improvements in representation of the boundary layer applicable to the Project's atmospheric model of China.