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1.
Proc Natl Acad Sci U S A ; 116(49): 24463-24469, 2019 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-31740599

RESUMO

From 2013 to 2017, with the implementation of the toughest-ever clean air policy in China, significant declines in fine particle (PM2.5) concentrations occurred nationwide. Here we estimate the drivers of the improved PM2.5 air quality and the associated health benefits in China from 2013 to 2017 based on a measure-specific integrated evaluation approach, which combines a bottom-up emission inventory, a chemical transport model, and epidemiological exposure-response functions. The estimated national population-weighted annual mean PM2.5 concentrations decreased from 61.8 (95%CI: 53.3-70.0) to 42.0 µg/m3 (95% CI: 35.7-48.6) in 5 y, with dominant contributions from anthropogenic emission abatements. Although interannual meteorological variations could significantly alter PM2.5 concentrations, the corresponding effects on the 5-y trends were relatively small. The measure-by-measure evaluation indicated that strengthening industrial emission standards (power plants and emission-intensive industrial sectors), upgrades on industrial boilers, phasing out outdated industrial capacities, and promoting clean fuels in the residential sector were major effective measures in reducing PM2.5 pollution and health burdens. These measures were estimated to contribute to 6.6- (95% CI: 5.9-7.1), 4.4- (95% CI: 3.8-4.9), 2.8- (95% CI: 2.5-3.0), and 2.2- (95% CI: 2.0-2.5) µg/m3 declines in the national PM2.5 concentration in 2017, respectively, and further reduced PM2.5-attributable excess deaths by 0.37 million (95% CI: 0.35-0.39), or 92% of the total avoided deaths. Our study confirms the effectiveness of China's recent clean air actions, and the measure-by-measure evaluation provides insights into future clean air policy making in China and in other developing and polluting countries.

2.
Sci Total Environ ; 682: 541-552, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31129542

RESUMO

A three-dimensional variational (3DVAR) lidar data assimilation method is developed based on the Community Radiative Transfer Model (CRTM) and Weather Research and Forecasting model coupled to Chemistry (WRF-Chem) model. A 3DVAR data assimilation (DA) system using lidar extinction coefficient observation data is established, and variables from the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) mechanism of the WRF-Chem model are employed. Hourly lidar extinction coefficient data from 12:00 to 18:00 UTC on March 13, 2018 at four stations in Beijing are assimilated into the initial field of the WRF-Chem model; subsequently, a 24 h PM2.5 concentration forecast is made. Results indicate that assimilating lidar data can effectively improve the subsequent forecast. PM2.5 forecasts without using lidar DA are remarkably underestimated, particularly during heavy haze periods; in contrast, forecasts of PM2.5 concentrations with lidar DA are closer to observations, the model low bias is evidently reduced, and the vertical distribution of the PM2.5 concentration in Beijing is distinctly improved from the surface to 1200 m. Of the five aerosol species, improvements of NO3- are the most significant. The correlation coefficient between PM2.5 concentration forecasts with lidar DA and observations at 12 stations in Beijing is increased by 0.45, and the corresponding average RMSE is decreased by 25 µg·m-3, which respectively compared to those without DA.

3.
Sci Total Environ ; 626: 887-898, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29898557

RESUMO

Despite the implementation of strict air pollution control measures in recent years, severe haze events were still encountered in the Beijing-Tianjin-Hebei (Jing-Jin-Ji) region during the winter 2016. In this work, seasonal differences in correlations between air pollution and geographic terrain, atmospheric dynamical and thermal structures, and PBL height over the Jing-Jin-Ji region in history and recent years were investigated and a comprehensive model of atmospheric factors affecting winter air pollution formation was proposed. We found that the distribution of PM2.5 concentration closely correlated with the topography feature of China and the difference in haze pollution intensity between winter and other seasons was the most significant in the Jing-Jin-Ji region. The "semi-enclosed" terrain along with the enhanced winter "downdraft" strongly inhibited the diffusion and convection of air pollutants in this region. Meanwhile, seasonal variations of the vertical thermal structure over the Jing-Jin-Ji region, i.e., the anomalous pattern of "upper warming and bottom cooling" structure in the middle troposphere, and the "weak wind zone" were more distinct in winter 2016 than historical record, providing an important precondition for the frequent occurrence of thermal inversion layers and severe pollution episodes in the lower troposphere. In addition, abnormally low PBL heights occurred in the Jing-Jin-Ji region during severe pollutant episodes in winter 2016, with mean postmeridian PBL height in December of only 869.4 m, the minimum value since 2013. PM2.5 concentration was not only closely related to PBL height but also the "warm cover" structure in the middle troposphere. The stronger the structure was, the lower the PBL height became, and severer the pollution event was encountered, accompanying water vapor accumulation and intensification of the thermal inversion layer in the lower troposphere. All above observations revealed the mutual feedback correlations between air pollutants concentration and meteorological factors.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Conceitos Meteorológicos , Material Particulado/análise , Poluição do Ar/estatística & dados numéricos , Pequim , Estações do Ano
4.
Sci Total Environ ; 642: 543-552, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29909321

RESUMO

The Beijing-Tianjin-Hebei (BTH) region in China suffers from heavy air pollution, especially in heating period. SO2 and NO2 are two of the key primary gaseous pollutants emitted by coal burning. The increase in air pollution caused by heating in the south-central part of the BTH region is higher than that in the northern part. And the distribution of SO2 and NO2 increment has significant differences. In this work, SO2 and NO2 emissions over the BTH region are determined using an adaptive "nudging" constrained method and a variational processing technique based on Ozone Monitoring Instrument (OMI) satellite data and surface measurement data collected in 2015. The application of the method can provide reliable, up-to-date and high-resolution mapping of sources of SO2 and NO2 emissions. These SO2 and NO2 emissions reflect the spatial differences in point and area sources in urban agglomerations and rural areas under different meteorological conditions during the non-heating and heating seasons. The intensity and influence of SO2 and NO2 emissions, particularly those of SO2, are significantly greater during the heating season than those during the non-heating season. Winter increases in SO2 emissions in the northern areas of the BTH region are larger than those in the southern part. In addition, significant increases in SO2 emissions occur mainly in suburban and rural areas, while those of NO2 emissions mainly occur in urban agglomerations. In the major urban areas, where coal has been replaced by natural gas or electric power for heating, winter heating causes much smaller increases in SO2 emissions than in other areas. The large amounts of bulk coal consumption in the suburban and rural areas could cause significant regional air pollution. Clear increases in SO2 and NO2 emissions in winter occur along a belt from southern Beijing to Langfang, Baoding, Shijiazhuang and Xingtai, which is consistent with a special "quasi-steady" air pollutant transport belt in the region. All above results show that the adaptive "nudging" constrained emission method could be an effective tool for air pollution control during certain seasons.

5.
Sci Rep ; 8(1): 5504, 2018 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-29615824

RESUMO

In addition to weather conditions and pollutant emissions, the degree to which topography influences the occurrence and development of haze pollution in downtown Beijing and the mechanisms that may be involved remain open questions. A series of atmospheric chemistry simulations are executed by using the online-coupled Weather Research and Forecasting with Chemistry (WRF-Chem) model for November-December 2015 with different hypothetical topographic height scenarios. The simulation results show that topography exerts an important influence on haze pollution in downtown Beijing, particularly the typical development of haze pollution. A possible mechanism that underlies the response of haze pollution to topography is that the mountains that surround Beijing tend to produce anomalous southerly winds, high relative humidity, low boundary layer heights, and sinking motion over most of Beijing. These conditions favor the formation and development of haze pollution in downtown Beijing. Furthermore, the reduction percentage in PM2.5 concentrations due to reduced terrain height in the southerly wind (S) mode is almost three times larger than that in the northerly wind (N) mode. In the context of the regional topography, the simple S and N modes represent useful indicators for haze prediction in Beijing to some extent, especially over medium to long time scales.

6.
Huan Jing Ke Xue ; 38(2): 476-484, 2017 Feb 08.
Artigo em Chinês | MEDLINE | ID: mdl-29964502

RESUMO

Based on the MODIS-Aqua aerosol optical depth (AOD) products from 2003 to 2014, Nighttime Lights Time data from DMSP satellites and basic meteorological data, the AOD spatial distributions of interannual and seasonal variations over three northeastern provinces of China(Liaoning, Jilin, Heilongjiang) were analyzed. It was found that there was a northeast-southwest area of high annual average AOD composed of Dalian, Shenyang, Changchun, Harbin and other cities, the 12-year average AOD value was 0.4-0.8. The low AOD occurred in the eastern and northern areas of the three northeastern provinces of China, where the forest-covering rate was high, and the 12-year average AOD value was less than 0.3. The seasonal variations of annual average AOD showed an increasing trend from spring to summer, then decreased in autumn and increased again in winter. The interannual variations of AOD over three northeastern provinces of China showed a decreasing trend in most areas, but the increasing trend occurred in the northeast-southwest region with the axis formed by Shenyang, Changchun and Harbin, revealing the polarization in recent 10 years over three northeastern provinces of China. In addition, spatial distribution of annual average AOD over three northeastern provinces of China in the years of strong and weak Western North Pacific Summer Monsoon was studied. Affected by the surface wind field, annual average AOD in weak monsoon years was higher than that in strong monsoon years.

7.
Sci Rep ; 4: 4451, 2014 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-24663145

RESUMO

Tropical cyclones (TC) are one of the most threatening natural hazards to human beings. Although significant improvements have been made in the track prediction of TCs during the past several decades, considerable uncertainties still exist, especially for recurving tracks. In this study, we explore the physical mechanisms that drove the large recurvature of super typhoon Megi through numerical sensitivity experiments using a regional atmospheric model. The results indicate that the cold air intrusion from the northwest to the southeast of China is the main cause of the sharp turning of Megi. This finding suggests that a cold air intrusion could be taken as an indicator for predicting the recurvature of a tropical cyclone in the future.


Assuntos
Tempestades Ciclônicas , Clima Tropical , China , Humanos , Modelos Teóricos
8.
Sci Rep ; 3: 1522, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23519311

RESUMO

Accurate prediction of where and when typhoons (or named hurricanes which form over the North Atlantic Ocean) will make landfall is critical to protecting human lives and properties. Although the traditional method of typhoon track prediction based on the steering flow theory has been proven to be an effective way in most situations, it slipped up in some cases. Our analysis of the long-term Chinese typhoon records reveals that typhoons, especially super typhoons (those with maximum sustained surface winds of greater than 51 ms(-1)), have a trend to make landfalls toward warmer land in China over the past 50 years (1960-2009). Numerical sensitivity experiments using an advanced atmospheric model further confirm this finding. Our finding suggests an alternative approach to predict the landfall tracks of the most devastating typhoons in the southeastern China.


Assuntos
Clima , Tempestades Ciclônicas , Modelos Teóricos , Oceano Atlântico , Atmosfera , China , Humanos , Vento
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