The effect of atmospheric aerosols and regional haze from air pollution on the yields of rice and winter wheat grown in China is assessed. The assessment is based on estimates of aerosol optical depths over China, the effect of these optical depths on the solar irradiance reaching the earth's surface, and the response of rice and winter wheat grown in Nanjing to the change in solar irradiance. Two sets of aerosol optical depths are presented: one based on a coupled, regional climate͞air quality model simulation and the other inferred from solar radiation measurements made over a 12-year period at meteorological stations in China. The model-estimated optical depths are significantly smaller than those derived from observations, perhaps because of errors in one or both sets of optical depths or because the data from the meteorological stations has been affected by local pollution. Radiative transfer calculations using the smaller, modelestimated aerosol optical depths indicate that the so-called ''direct effect'' of regional haze results in an Ϸ5-30% reduction in the solar irradiance reaching some of China's most productive agricultural regions. Crop-response model simulations suggest an Ϸ1:1 relationship between a percentage increase (decrease) in total surface solar irradiance and a percentage increase (decrease) in the yields of rice and wheat. Collectively, these calculations suggest that regional haze in China is currently depressing optimal yields of Ϸ70% of the crops grown in China by at least 5-30%. Reducing the severity of regional haze in China through air pollution control could potentially result in a significant increase in crop yields and help the nation meet its growing food demands in the coming decades.

Highly ordered mesoporous carbons and silicas with ultralarge accessible pores have been successfully synthesized by using laboratory-made poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers as templates via the evaporation-induced self-assembly (EISA) approach. Resols and tetraethyl orthosilicate (TEOS) serve as carbon and silica precursors, respectively. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) measurements show that the mesoporous carbons (denoted as C-FDU-18) possess face centered cubic closed-packing (fcc) mesostructure (Fm3m) with large-domain ordering. N2 sorption isotherms reveal a large mesopore at the mean value of 22.6 nm with a narrow pore-size distribution. Mesoporous silicas (Si-FDU-18) also display a highly ordered fcc closed-packing mesostructure with an ultralarge unit cell (a = 54.6 nm). A hydrothermal recrystallization was introduced for the first time to produce micropores in thick silica walls (approximately 7.7 nm) and thus to generate ultralarge accessible mesopores (30.8 nm). Notably, the amphiphilic diblock copolymer with high molecular weight (PEO125-PS230, 29700 g mol-1) in this report was prepared via a simple method of atom transfer radical polymerization (ATRP). It can be easily available for chemists even without any experience in polymer synthesis.

Hierarchical carbonaceous monoliths with ordered 2-D hexagonal mesostructures have been successfully synthesized by using phenolic resols as precursors and mixed triblock copolymers as templates via a one-step hydrothermal approach.

[1] A regional coupled climate-chemistry-aerosol model is developed. It is used to assess the direct and indirect effects of anthropogenic sulfate and carbonaceous aerosols on regional climate over east Asia with a focus on precipitation. The simulated direct and first indirect effects for the most part reduce the solar radiation and hence decrease the surface temperature, while the second indirect effect generates both negative solar forcing and a substantial positive long-wave forcing. It decreases the precipitation, but because of the cancelling effect, surface temperature does not change very much. With the interactively model-calculated current aerosol loading and the combined direct/semidirect/ first indirect effect, the simulated precipitation is reduced by about 10% in the fall and winter and by about 5% in the spring and summer. The second indirect effect has the largest impact, by itself decreasing the fall and winter precipitation from about 3% to 20%, depending on the autoconversion scheme assumed. The semidirect effect on precipitation is relatively small. An empirical orthogonal function analysis of climatological precipitation over east Asia since the last century shows a decreasing trend of the leading modes over most of China in the fall and winter, which is generally geographically consistent with the distribution of the model-simulated precipitation reduction from anthropogenic aerosols.

A regional coupled climate-chemistry-aerosol model is developed to examine the impacts of anthropogenic aerosols on surface temperature and precipitation over East Asia. Besides their direct and indirect reduction of short-wave solar radiation, the increased cloudiness and cloud liquid water generate a substantial downward positive long-wave surface forcing; consequently, nighttime temperature in winter increases by ؉0.7°C, and the diurnal temperature range decreases by ؊0.7°C averaged over the industrialized parts of China. Confidence in the simulated results is limited by uncertainties in model cloud physics. However, they are broadly consistent with the observed diurnal temperature range decrease as reported in China, suggesting that changes in downward longwave radiation at the surface are important in understanding temperature changes from aerosols.anthropogenic aerosols ͉ diurnal temperature range ͉ long-wave radiative forcing ͉ regional climate change ͉ second indirect effect A tmospheric aerosols influence the climate directly by scattering and absorbing incoming solar radiation and indirectly by acting as cloud condensation nuclei and͞or ice nuclei, therefore modifying the microphysics, radiative properties, and lifetime of clouds. Consequently, they alter the net radiation both at the top and bottom of the atmosphere (1-5). Since preindustrial times, anthropogenic aerosols, consisting mainly of sulfate and carbonaceous aerosols [black carbon (BC) and organic carbon], have substantially increased, especially over urban͞ industrial regions (6-8). This perturbation in aerosol concentrations is believed to have had significant climatic impacts, especially at the regional scale (7, 9-11).Recently, Zhou et al. (12), following the technique advanced by Kalnay and Cai (13), found a larger decrease in the diurnal temperature range (DTR) over the industrialized parts of China using the land-surface air temperature data recorded at 194 meteorological stations of China from 1979 to 1998 than that using the National Centers for Environmental Prediction͞ Department of Energy Atmospheric Model Intercomparison Project (AMIP)-II Reanalysis data (R-2) (14). The authors interpreted their results as an indication of the climatic effect from urbanization and͞or land use changes through the modifications of boundary conditions. However, the aerosol indirect effect includes changes in cloud properties, which possibly lead to a long-wave surface warming at night, in addition to daytime cooling from aerosol-solar radiation interaction. The decrease of DTR has been hypothesized to result from increasing cloudiness and, hence, the reduction of the daytime solar heating at the surface (15-17). However, cloud cover has only increased slightly in southern China (18). Could some other cloud changes contribute to the observed decrease of DTR?To address the question, we present an attempt to use a coupled regional climate-chemistry-aerosol model to assess the effects of anthropogenic aerosols on cloud properties and hence on regional ...

No abstract

[1] We consider two independently derived data sets. The first represents the annually averaged distribution of anthropogenic aerosols over East Asia as derived by a coupled regional climate/ chemical transport model. The other is the annually averaged distributions of cloud optical depths and cloud amount over East Asia derived by the International Satellite Cloud Climatology Project (ISCCP) for 1990, 1991, 1992, and 1993. We find a remarkable similarity in the distributions of model-calculated anthropogenic aerosols and ISCCP-reported cloud optical depths, with both exhibiting a region of enhanced values extending over the east central portion of China, between the Sichuan Basin and the Yangtze Delta, and then in an easterly direction over the East China Sea, Japan, and So uth Kore a, and the wes tern edge of the Pacifi c Ocea n. Linear regres sion between the estimated aerosol column burdens and the cloud optical depths yields an r 2 > 0.6, indicating that the correlations are statistically significant at a confidence level that is >99.9% and that more than 60% of the variation in the cloud optical depths is related to variations in the anthropogenic aerosol abundances. Multivariate analysis involving the distributions of boundary layer relative humidity and precipitation over East Asia, as well as that of the model-calculated anthropogenic aerosols and the ISCCP-reported cloud properties, indicates that the relationship between anthropogenic aerosols and cloud optical depth is unique to these two variables and not symptomatic of a more general mechanism involving the hydrologic cycle. Trend analysis of the ISCCP data suggests that there was an upward trend in cloud optical depths over areas in East Asia impacted by air pollution during the early 1990s that would have corresponded to the likely increase in anthropogenic aerosol concentrations over this period in East Asia in response to growing anthropogenic emissions. A likely explanation for these findings is that there is a mechanistic coupling between anthropogenic aerosol concentrations and cloud optical properties; one such mechanism is the so-called first and second indirect effect by which aerosols enhance the optical depths and albedos of clouds by increasing the number of droplets within clouds and suppressing precipitation from clouds, respectively. The regressions further suggest that the cloud optical depths increase on average by 0.16 for each 1 mg m -2 increase in the column-integrated anthropogenic aerosol burden. Simple box-model calculations suggest that this is equivalent to a cooling over the model domain from anthropogenic aerosols via the indirect effect that is a factor of about 1.5 times that from the direct effect. Accounting for a possible underestimate in modelsimulated aerosol concentrations over the model domain of as much as a factor of 0.6 would lower the estimated cooling from the indirect effect to about 1 times that from the direct effect. In contrast to the results using ISSCP-derived cloud optical depths, the correlation be...

We discuss a series of simulations of anthropogenic sulfur over East Asia with a SO2/SO42− chemistry‐transport model driven in on‐line mode by a regional climate model. Sensitivity to OH and H2O2 concentration, cloud parameters, SO2 dry deposition and emission strength is analyzed and the different components of the sulfur budget are examined. The SO2 and SO2−4 column burdens show pronounced variability at temporal scales from seasonal to synoptic and sub‐daily, with SO2 and SO2−4 behaving differently due to the interplay of chemical conversion, removal and transport processes. Both SO2 and SO2−4 show marked spatial variability, with emission being the dominant term in regulating the SO2 spatial distribution. The atmospheric SO2 and SO2−4 amounts show close to a linear response to surface emission. Aqueous phase SO2→SO2−4 conversion and wet removal are the primary factors that regulate the SO2−4 amounts, with dry deposition and gas phase SO2→SO2−4 conversion being of secondary importance. Aqueous phase conversion and dry deposition are the dominant loss mechanisms for SO2 . The model shows low sensitivity to variations in OH, H2O2, and cloud parameters, while the sensitivity to prescribed dry deposition velocity is more pronounced. Overall, our results are in line with previous modeling studies and with very limited available observations.