In January 2013, a long-lasting episode of severe haze occurred in central and eastern China, and it attracted attention from all sectors of society. The process and evolution of haze pollution episodes were observed ...In January 2013, a long-lasting episode of severe haze occurred in central and eastern China, and it attracted attention from all sectors of society. The process and evolution of haze pollution episodes were observed by the ＂Forming Mechanism and Con- trol Strategies of Haze in China＂ group using an intensive aerosol and trace gases campaign that simultaneously obtained data at 11 ground-based observing sites in the CARE-China network. The characteristics and formation mechanism of haze pollu- tion episodes were discussed. Five haze pollution episodes were identified in the Beijing-Tianjin-Hebei （Jing-Jin-Ji） area; the two most severe episodes occurred during 9-15 January and 25-31 January. During these two haze pollution episodes, the maximum hourly PMz5 mass concentrations in Beijing were 680 and 530 ~tg m-3, respectively. The process and evolution of haze pollution episodes in other major cities in the Jing-Jin-Ji area, such as Shijiazhuang and Tianjin were almost the same as those observed in Beijing. The external cause of the severe haze episodes was the unusual atmospheric circulation, the depres- sion of strong cold air activities and the very unfavorable dispersion due to geographical and meteorological conditions. How- ever, the internal cause was the quick secondary transformation of primary gaseous pollutants to secondary aerosols, which contributed to the ＂explosive growth＂ and ＂sustained growth＂ of PM2.5. Particularly, the abnormally high amount of nitric ox- ide （NOx） in the haze episodes, produced by fossil fuel combustion and vehicle emissions, played a direct or indirect role in the quick secondary transformation of coal-burning sulphur dioxide （SO2） to sulphate aerosols. Furthermore, gaseous pollutants were transformed into secondary aerosols through heterogeneous reactions on the surface of fine particles, which can change the particle＇s size and chemical composition. Consequently, the proportion of secondary inorganic ions, such as sulphate and nitrate, gradually incr展开更多
By searching literature databases, we obtained more than 200 articles published since 1993 that related to the measurements of topsoil organic carbon (SOC) in different regions. To objectively evaluate the changes in ...By searching literature databases, we obtained more than 200 articles published since 1993 that related to the measurements of topsoil organic carbon (SOC) in different regions. To objectively evaluate the changes in the SOC over the last two decades, we selected 132 representative articles from these documented articles. More than sixty thousand soil samples and/or sampling sites were included in the selected articles. Results from ana- lyzing these data sets indicated that the concentra- tion of SOC increased in 53%-59%, decreased in 30%-31% and stabilized in 4%-6% of the national croplands, respectively. A further investigation showed that the total increment of SOC in Chinese croplands ranged from 311.3 Tg to 401.4 Tg. In terms of administrative region, significant increase occurred in eastern and northern China and decrease in northeastern China, respectively. When evaluated by soil great groups, the SOC increased considerably in paddy soils and fluvo-aquic soils and reduced con- spicuously in black soils. The increase of SOC is attributed to the amendments of crop residues and organic manure, the augment of synthetic fertilizer application and the optimal combination of nutrients, and the development of no-tillage and reduced-tillage practice. Water loss and soil erosion and low input induced a great decrease of the SOC in black soils. In order to effectively enhance soil C sequestrations and to greatly control the SOC reduction in north- eastern China, future efforts should be made in de- veloping new techniques, training farmers and con- summating the policy of governmental compensation,by which the application of crop straw, the improve- ment of fertilization, the practice of no-tillage and reduced-tillage, and the control of water loss and soil erosion could be further realized. To respond to the increasing pressure from the Kyoto Protocol thence- forward, four aspects were further addressed for fu- ture research needs, including the quantification of SOC storage in the Second State Soil Survey and at p展开更多
Tropospheric ozone（O3） and aerosols are major air pollutants in the atmosphere. They have also made significant contributions to radiative forcing of climate since preindustrial times. With its rapid economic develo...Tropospheric ozone（O3） and aerosols are major air pollutants in the atmosphere. They have also made significant contributions to radiative forcing of climate since preindustrial times. With its rapid economic development, concentrations of air pollutants are relatively high in China; hence, quantifying the role of air pollutants in China in regional climate change is especially important. This review summarizes existing knowledge with regard to impacts of air pollutants on climate change in China and defines critical gaps needed to reduce the associated uncertainties. Measured monthly, seasonal, and annual mean surface-layer concentrations of O3 and aerosols over China are compiled in this work, with the aim to show the magnitude of concentrations of O3 and aerosols over China and to provide datasets for evaluation of model results in future studies. Ground-based and satellite measurements of O3 column burden and aerosol optical properties, as well as model estimates of radiative forcing by tropospheric O3 and aerosols are summarized. We also review regional and global modeling studies that have investigated climate change driven by tropospheric O3and/or aerosols in China; the predicted sign and magnitude of the responses in temperature and precipitation to O3/aerosol forcings are presented. Based on this review, key priorities for future research on the climatic effects of air pollutants in China are highlighted.展开更多
Objective To investigate the seasonal characteristics and the sources of elements and ions with different sizes in the aerosols in Beijing. Methods Samples of particulate matters （PM2,5）, PM10, and total suspended p...Objective To investigate the seasonal characteristics and the sources of elements and ions with different sizes in the aerosols in Beijing. Methods Samples of particulate matters （PM2,5）, PM10, and total suspended particle （TSP） aerosols were collected simultaneously in Beijing from July 2001 to April 2003. The aerosol was chemically characterized by measuring 23 elements and 18 water-soluble ions by inductively coupled plasma-atomic emission spectroscopy （ICP-AES） and ion chromatography （IC）, respectively. Results The samples were divided into four categories： spring non-dust, spring dust, summer dust, and winter dust. TSP, PM10, and PM2.5 were most abundant in the spring dust, and the least in summer dust. The average mass ratios of PM〉10, PM2,5-10, and PM2.5 to TSP confirmed that in the spring dust both the large coarse （PM〉10） and fine particles （PM2.5） contributed significantly in summer PM2.5, PM2,5-10, and PM〉10 contributed similar fractions to TSP, and in winter much PM2.5. The seasonal variation characteristics of the elements and ions were used to divide them into four groups： crustal, pollutant, mixed, and secondary. The highest levels of crustal elements, such as AI, Fe, and Ca, were found in the dust season, the highest levels of pollutant elements and ions, such as As, F, and Cl^-, were observed in winter, and the highest levels of secondary ions （SO4^2-, NO3^-, and NH4^＋） were seen both in summer and in winter. The mixed group （Eu, Ni, and Cu） showed the characteristics of both crustal and pollutant elements. The mineral aerosol from outside Beijiug contributed more than that from the local part in all the reasons but summer, estimated using a newly developed element tracer technique.展开更多
A regional nitrogen cycle model, named IAP-N, was designed for simulating regional nitrogen （N） cycling and calculating N fluxes flowing among cultivated soils, crops, and livestock, as well as human, atmospheric an...A regional nitrogen cycle model, named IAP-N, was designed for simulating regional nitrogen （N） cycling and calculating N fluxes flowing among cultivated soils, crops, and livestock, as well as human, atmospheric and other systems. The conceptual structure and calculation methods and procedures of this model are described in detail. All equations of the model are presented. In addition, definitions of all the involved variables and parameters are given. An application of the model in China at the national scale is presented. In this example, annual surpluses of consumed synthetic N fertilizer; emissions of nitrous oxide （N2O）, ammonia （NH3） and nitrogen oxide （NOx）; N loss from agricultural lands due to leaching and runoff; and sources and sinks of anthropogenic reactive N （Nr） were estimated for the period 1961-2004. The model estimates show that surpluses of N fertilizer started to occur in the mid 1990s and amounted to 5.7 Tg N yr^-1 in the early 2000s. N20 emissions related to agriculture were estimated as 0.69 Tg N yr^-1 in 2004, of which 58% was released directly from N added to agricultural soils. Total NH3 and NOx emissions in 2004 amounted to 4.7 and 4.9 Tg N yr^-1, respectively. About 3.9 Tg N yr^-1 of N was estimated to have flowed out of the cultivated soil layer in 2004, which accounted for 33% of applied synthetic N fertilizer. Anthropogenic Nr sources changed from 2.8 （1961） to 28.1 Tg N yr^-1 （2004）, while removal （sinks） changed from to 2.1 to 8.4 Tg N yr^-1. The ratio of anthropogenic Nr sources to sinks was only 1.4 in 1961 but 3.3 in 2004. Further development of the IAP-N model is suggested to focus upon： Ca） inter-comparison with other regional N models; （b） overcoming the limitations of the current model version, such as adaptation to other regions, high-resolution database, and so on; and （c） developing the capacity to estimate the safe threshold of anthropogenic Nr source to sink ratios.展开更多
A facility of BaPS （Barometric Process Separation） was used to determine soil respiration, gross nitrification and denitrification in a winter wheat field with depths of 0-7, 7--14 and 14-21 cm. N2O production was d...A facility of BaPS （Barometric Process Separation） was used to determine soil respiration, gross nitrification and denitrification in a winter wheat field with depths of 0-7, 7--14 and 14-21 cm. N2O production was determined by a gas chromatograph. Crop root mass and relevant soil parameters were measured. Results showed that soil respiration and gross nitrification decreased with the increase of soil depth, while denitrification did not change significantly. In comparison with no-plowing plot, soil respiration increased significantly in plowing plot, especially in the surface soil of 0-7 cm, while gross nitrification and denitrification rates were not affected by plowing. Cropping practice in previous season was found to affect soil gross nitrification in the following wheat-growing season. Higher gross nitrification rate occurred in the filed plot with preceding crop of rice compared with that of maize for all the three depths of 0-7, 7-14 and 14-21 cm. A further investigation indicated that the nitrification for all the cases accounted for about 76% of the total nitrogen transformation processes of nitrification and denitrification and the N2O production correlated with nitrification significantly, suggesting that nitrification is a key process of soil N2O production in the wheat field. In addition, the variations of soil respiration and gross nitrification were exponentially dependent on root mass （p〈0.00l）.展开更多
Utilizing aircraft sounding data collected from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1998) campaign, the authors evaluated commonly-used profile methods for Arctic ABL height estimation by validating ag...Utilizing aircraft sounding data collected from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1998) campaign, the authors evaluated commonly-used profile methods for Arctic ABL height estimation by validating against the'true'ABL height from aircraft sounding profiles, where ABL height is defined as the top of the layer with significant turbulence. Furthermore, the best performing method was used to estimate ABL height from the one-year GPS soundings obtained during SHEBA (October 1997-October 1998). It was found that the temperature gradient method produces a reliable estimate of ABL height. Additionally, the authors determined optimal threshold values of temperature gradient for stable boundary layer (SBL) and convective boundary layer (CBL) to be 6.5 K/100 m and 1.0 K/100 m, respectively. The maximum ABL height during the year was 1150 m occurred in May. Median values of Arctic ABL height in May, June, July, and August were 400 m, 430 m, 180 m, and 320 m, respectively. Arctic ABL heights are clearly higher in the spring than in the summer.展开更多
Ground observation data from 8 meteorological stations in Xi＇an, air mass concentration data from 13 environmental quality monitoring sites in Xi＇an, as well as radiosonde observation and wind profile radar data, we...Ground observation data from 8 meteorological stations in Xi＇an, air mass concentration data from 13 environmental quality monitoring sites in Xi＇an, as well as radiosonde observation and wind profile radar data, were used in this study. Thereby, the process,causes and boundary layer meteorological characteristics of a heavy haze episode occurring from 16 to 25 December 2013 in Xi＇an were analyzed. Principal component analysis showed that this haze pollution was mainly caused by the high-intensity emission and formation of gaseous pollutants（NO_2, CO and SO_2） and atmospheric particles（PM_（2.5）（fine particles） and PM10（respirable suspended particle）. The second cause was the relative humidity and continuous low temperature. The third cause was the allocation of the surface pressure field. The presence of a near-surface temperature inversion at the boundary layer formed favorable stratification conditions for the formation and maintenance of heavy haze pollution. The persistent thick haze layer weakened the solar radiation. Meanwhile, a warming effect in the urban canopy layer and in the transition zone from the urban friction sublayer to the urban canopy was indicated. All these conditions facilitated the maintenance and reinforcement of temperature inversion. The stable atmospheric stratification finally acted on the wind field in the boundary layer, and further weakened the exchange capacity of vertical turbulence. The superposition of a wind field with the horizontal gentle wind induced the typical air stagnation and finally caused the deterioration of air quality during this haze event.展开更多
Based on an intermediate coupled model （ICM）, a probabilistic ensemble prediction system （EPS） has been developed. The ensemble Kalman filter （EnKF） data assimilation approach is used for generating the initial ...Based on an intermediate coupled model （ICM）, a probabilistic ensemble prediction system （EPS） has been developed. The ensemble Kalman filter （EnKF） data assimilation approach is used for generating the initial ensemble conditions, and a linear, first-order Markov-Chain SST anomaly error model is embedded into the EPS to provide model-error perturbations. In this study, we perform ENSO retrospective forecasts over the 120 year period 1886-2005 using the EPS with 100 ensemble members and with initial conditions obtained by only assimilating historic SST anomaly observations. By examining the retrospective ensemble forecasts and available observations, the verification results show that the skill of the ensemble mean of the EPS is greater than that of a single deterministic forecast using the same ICM, with a distinct improvement of both the correlation and root mean square （RMS） error between the ensemble-mean hindcast and the deterministic scheme over the 12-month prediction period. The RMS error of the ensemble mean is almost 0.2℃ smaller than that of the deterministic forecast at a lead time of 12 months. The probabilistic skill of the EPS is also high with the predicted ensemble following the SST observations well, and the areas under the relative operating characteristic （ROC） curves for three different ENSO states （warm events, cold events, and neutral events） are all above 0.55 out to 12 months lead time. However, both deterministic and probabilistic prediction skills of the EPS show an interdecadal variation. For the deterministic skill, there is high skill in the late 19th century and in the middle-late 20th century （which includes some artificial skill due to the model training period）, and low skill during the period from 1906 to 1961. For probabilistic skill, for the three different ENSO states, there is still a similar interdecadal variation of ENSO probabilistic predictability during the period 1886~2005. There is high skill in the late 19th century from 1886 to 1905, 展开更多
Retrieval experiment was made for global total column ozone using the first year measurements of Total Ozone Unit (TOU) on board the second generation polar orbiting meteorological satellite of China, FY-3/A. The retr...Retrieval experiment was made for global total column ozone using the first year measurements of Total Ozone Unit (TOU) on board the second generation polar orbiting meteorological satellite of China, FY-3/A. The retrieval results were analyzed and validated by comparison with AURA/OMI, Meteop/GOME-2 global ozone products and ground-based ozone measurement data. The qualititative comparisons over the globe especially over Antarctica and the Tibetan Plateau show that the spatial and temporal distribution characteristics are consistent with OMI and GOME-2 products. The quantitative comparisons with ground-based measurements and AURA/OMI ozone product were made over 74 stations, the TOU total ozone retrieval has a 3% rms relative error compared with AURA/OMI ozone product and 4.2% rms relative error with ground-based measurements. The maximum difference between satellite retrieval and ground-based measurements was found in the Antarctica ozone hole. The TOU global ozone product is operational and distributed to all users.展开更多
Based on our developed ENSO (El Nio-Southern Oscillation) ensemble prediction system (EPS), the impacts of stochastic initial-error and model-error perturbations on ENSO ensemble predictions are examined and discussed...Based on our developed ENSO (El Nio-Southern Oscillation) ensemble prediction system (EPS), the impacts of stochastic initial-error and model-error perturbations on ENSO ensemble predictions are examined and discussed by performing four sets of 14-a retrospective forecast experiments in both a deterministic and probabilistic sense. These forecast schemes are differentiated by whether they considered the initial or model stochastic perturbations. The comparison results suggest that the stochastic model-error perturbations, which are added into the modeled physical fields to mainly represent the uncertainties of the physical model, have significant, positive impacts on improving the ensemble prediction skills during the entire 12-month forecast process. However, the stochastic initial-error perturbations have relatively small impacts on the ensemble prediction system, and its impacts are mainly focusing on the first 3-month predictions.展开更多
When gasoline is burned to power an automotive engine, a portion of the fuel remains unburned or is partially burned and leaves the engine as hydrocarbon and oxygenated compounds. In addition, a small portion of the f...When gasoline is burned to power an automotive engine, a portion of the fuel remains unburned or is partially burned and leaves the engine as hydrocarbon and oxygenated compounds. In addition, a small portion of the fuel can escape the vehicle through evaporation. Changes in alkanes, olefins and aromatics each affect emissions differently, which could complicate control strategies for air pollution. In this study, we collected 31 gasoline samples over five provinces and cities(Beijing, Tianjin, Hebei, Shandong, and Shaanxi) in North China between 2012 and 2013. The organic composition of the gasoline samples was analyzed using the gas chromatography-mass spectrometry(GC-MS) method, and the aniline compounds were analyzed by solvent extraction and the GC-MS method. The ratios of alkanes, aromatics, olefins and other organic compounds in gasoline were 40.6%, 38.1%, 12.9% and 8.4%, respectively. The aromatic and benzene exceedances were 15 and 8 based on the China's gasoline standards(III), and they accounted for 48.4% and 25.8% of all the gasoline samples, respectively. Strong carcinogen aniline compounds were detected in all 31 samples, and the content of aniline compounds in 3 samples exceeded 1%. The high proportion of aromatics and olefins in the gasoline increased the emissions of carbon monoxide(CO) and toxics, as well as the atmospheric photochemical reactivity of exhaust emissions, which could hasten the formation of secondary pollutants. Our results are helpful for redefining government strategies to control air pollution in North China and relevant for developing new refining technology throughout China.展开更多
The Tibetan Plateau has substantial impacts on the weather and climate of the Northern Hemisphere, due in large part to the thermal effects of the plateau surface. Surface temperature over the Tibetan Plateau is the m...The Tibetan Plateau has substantial impacts on the weather and climate of the Northern Hemisphere, due in large part to the thermal effects of the plateau surface. Surface temperature over the Tibetan Plateau is the most important parameter in determining these thermal effects. We present a method for verifying widely used reanalysis temperature products from NCEP-R2, ERA-Interim, and JRA-25 over the Tibetan Plateau, with the aim of obtaining a reliable picture of surface temperature and its changes over the plateau. Reanalysis data are validated against the topography elevation, satellite observations, and radiosonde data. ERA-Interim provides the most reliable estimates of Tibetan Plateau surface temperature among these three reanalyses. We therefore use this dataset to study the climatology and trends of surface temperature over the Tibetan Plateau. ERA-Interim data indicate a dramatic warming over the Tibetan Plateau from 1979 to 2010, with warming rates of 0.33℃ per decade in annual mean temperature, 0.22℃ per decade in summer and 0.4℃ per decade in winter mean temperatures. Comparison with the results of previous studies suggests that surface warming over the Tibetan Plateau has accelerated during the past 30 years. This warming is distributed heterogeneously across the Tibetan Plateau, possibly due to topographic effects.展开更多
Vehicular emissions in China in 2006 and 2010 were calculated at a high spatial resolution based on the data released by the National Bureau of Statistics, by taking the emission standards into consideration. China＇s...Vehicular emissions in China in 2006 and 2010 were calculated at a high spatial resolution based on the data released by the National Bureau of Statistics, by taking the emission standards into consideration. China＇s vehicular emissions of carbon monoxide （CO）, nitrogen oxides （NOx）, volatile organic compounds （VOCs）, ammonia （NH3）, fine particulate matters （PM2.5）, inhalable particulate matters （PMlo）, black carbon （BC）, and organic carbon （OC） were 30,113.9, 4593.7, 6838.0, 20.9, 400.2, 430.5,285.6, and 105.1 Gg, respectively, in 2006 and 34,175.2, 5167.5, 7029.4, 74.0, 386.4, 417.1, 270.9, and 106.2 Gg, respectively, in 2010. CO, VOCs, and NH3 emissions were mainly from motorcycles and light-duty gasoline vehicles, whereas NOx, PMzs, PMlo, and BC emissions were mainly from rural vehicles and heavy- duty diesel trucks. OC emissions were mainly from motorcycles and heavy-duty diesel trucks. Vehicles of pre-China I （vehicular emission standard of China before phase I） and China I （vehicular emission standard of China in phase I） were the primary contributors to all of the pollutant emissions except NH3, which was mainly from China III and China IV gasoline vehicles. The total emissions of all the pollutants except NH3 changed little from 2006 to 2010. This finding can be attributed to the implementation of strict emission standards and to improvements in oil quality.展开更多
An ocean reanalysis system for the joining area of Asia and Indian-Pacific Ocean (AIPO) has been developed and is currently delivering reanalysis data sets for study on the air-sea interaction over AIPO and its climat...An ocean reanalysis system for the joining area of Asia and Indian-Pacific Ocean (AIPO) has been developed and is currently delivering reanalysis data sets for study on the air-sea interaction over AIPO and its climate variation over China in the inter-annual time scale.This system consists of a nested ocean model forced by atmospheric reanalysis,an ensemble-based multivariate ocean data assimilation system and various ocean observations.The following report describes the main components of the data assimilation system in detail.The system adopts an ensemble optimal interpolation scheme that uses a seasonal update from a free running model to estimate the background error covariance matrix.In view of the systematic biases in some observation systems,some treatments were performed on the observations before the assimilation.A coarse resolution reanalysis dataset from the system is preliminarily evaluated to demonstrate the performance of the system for the period 1992 to 2006 by comparing this dataset with other observations or reanalysis data.展开更多
In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature an...In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature and precipitation during the severe snowstorm that occurred in southern China during 0800 26 January to 0800 29 January 2008 （Note that all times are local time except when otherwise stated）. Black carbon aerosol was simulated online within the WRF-Chem. The model resuits showed that surface-albedo, averaged over 27-28 January, can be reduced by up to 10% by the deposition of BC. As a result, relative to a simulation that does not consider deposition of BC on snow/ice, the authors predicted surface air temperatures during 27-28 January can differ by -1.95 to 2.70 K, and the authors predicted accumulated precipitation over 27-28 January can differ by -2.91 to 3.10 mm over Areas A and B with large BC deposition. Different signs of changes are determined by the feedback of clouds and by the availability of water vapor in the atmosphere.展开更多
The wind data of four typhoons were obtained and analyzed. The wind speeds were measured by sonic anemometers at four observation sites in Guangdong and Hainan provinces. Detailed analysis of the wind data was conduct...The wind data of four typhoons were obtained and analyzed. The wind speeds were measured by sonic anemometers at four observation sites in Guangdong and Hainan provinces. Detailed analysis of the wind data was conducted to investigate the turbulence characteristics of the typhoons. Characteristics of the gust factor and the turbulence integral scale of the typhoons were concluded with high confidence. The relationships among the gust factor, gust duration time, mean wind speed, roughness length, and turbulence intensity were described. The turbulence integral scale was found to be closely related to the segment length and turbulence intensity.展开更多
基金supported by the Chinese Academy of Sciences Strategic Priority Research Program(Grant Nos.XDB05020000 and XDA05100100)the National Natural Science Foundation of China(Grant Nos.41230642 and 41021004)
文摘In January 2013, a long-lasting episode of severe haze occurred in central and eastern China, and it attracted attention from all sectors of society. The process and evolution of haze pollution episodes were observed by the ＂Forming Mechanism and Con- trol Strategies of Haze in China＂ group using an intensive aerosol and trace gases campaign that simultaneously obtained data at 11 ground-based observing sites in the CARE-China network. The characteristics and formation mechanism of haze pollu- tion episodes were discussed. Five haze pollution episodes were identified in the Beijing-Tianjin-Hebei （Jing-Jin-Ji） area; the two most severe episodes occurred during 9-15 January and 25-31 January. During these two haze pollution episodes, the maximum hourly PMz5 mass concentrations in Beijing were 680 and 530 ~tg m-3, respectively. The process and evolution of haze pollution episodes in other major cities in the Jing-Jin-Ji area, such as Shijiazhuang and Tianjin were almost the same as those observed in Beijing. The external cause of the severe haze episodes was the unusual atmospheric circulation, the depres- sion of strong cold air activities and the very unfavorable dispersion due to geographical and meteorological conditions. How- ever, the internal cause was the quick secondary transformation of primary gaseous pollutants to secondary aerosols, which contributed to the ＂explosive growth＂ and ＂sustained growth＂ of PM2.5. Particularly, the abnormally high amount of nitric ox- ide （NOx） in the haze episodes, produced by fossil fuel combustion and vehicle emissions, played a direct or indirect role in the quick secondary transformation of coal-burning sulphur dioxide （SO2） to sulphate aerosols. Furthermore, gaseous pollutants were transformed into secondary aerosols through heterogeneous reactions on the surface of fine particles, which can change the particle＇s size and chemical composition. Consequently, the proportion of secondary inorganic ions, such as sulphate and nitrate, gradually incr
文摘By searching literature databases, we obtained more than 200 articles published since 1993 that related to the measurements of topsoil organic carbon (SOC) in different regions. To objectively evaluate the changes in the SOC over the last two decades, we selected 132 representative articles from these documented articles. More than sixty thousand soil samples and/or sampling sites were included in the selected articles. Results from ana- lyzing these data sets indicated that the concentra- tion of SOC increased in 53%-59%, decreased in 30%-31% and stabilized in 4%-6% of the national croplands, respectively. A further investigation showed that the total increment of SOC in Chinese croplands ranged from 311.3 Tg to 401.4 Tg. In terms of administrative region, significant increase occurred in eastern and northern China and decrease in northeastern China, respectively. When evaluated by soil great groups, the SOC increased considerably in paddy soils and fluvo-aquic soils and reduced con- spicuously in black soils. The increase of SOC is attributed to the amendments of crop residues and organic manure, the augment of synthetic fertilizer application and the optimal combination of nutrients, and the development of no-tillage and reduced-tillage practice. Water loss and soil erosion and low input induced a great decrease of the SOC in black soils. In order to effectively enhance soil C sequestrations and to greatly control the SOC reduction in north- eastern China, future efforts should be made in de- veloping new techniques, training farmers and con- summating the policy of governmental compensation,by which the application of crop straw, the improve- ment of fertilization, the practice of no-tillage and reduced-tillage, and the control of water loss and soil erosion could be further realized. To respond to the increasing pressure from the Kyoto Protocol thence- forward, four aspects were further addressed for fu- ture research needs, including the quantification of SOC storage in the Second State Soil Survey and at p
基金supported by the National Basic Research Program of China (Grant No. 2014CB441202)the Chinese Academy of Sciences Strategic Priority Research Program (Grant No. XDA05100503)+1 种基金the National Natural Science Foundation of China (Grant Nos. 41475137 and 41321064)Special Funding in Atmospheric Science (Grant No. GYHY200906020)
文摘Tropospheric ozone（O3） and aerosols are major air pollutants in the atmosphere. They have also made significant contributions to radiative forcing of climate since preindustrial times. With its rapid economic development, concentrations of air pollutants are relatively high in China; hence, quantifying the role of air pollutants in China in regional climate change is especially important. This review summarizes existing knowledge with regard to impacts of air pollutants on climate change in China and defines critical gaps needed to reduce the associated uncertainties. Measured monthly, seasonal, and annual mean surface-layer concentrations of O3 and aerosols over China are compiled in this work, with the aim to show the magnitude of concentrations of O3 and aerosols over China and to provide datasets for evaluation of model results in future studies. Ground-based and satellite measurements of O3 column burden and aerosol optical properties, as well as model estimates of radiative forcing by tropospheric O3 and aerosols are summarized. We also review regional and global modeling studies that have investigated climate change driven by tropospheric O3and/or aerosols in China; the predicted sign and magnitude of the responses in temperature and precipitation to O3/aerosol forcings are presented. Based on this review, key priorities for future research on the climatic effects of air pollutants in China are highlighted.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 29837190, 30230310, 20077004, and 20477004),and Beijing Natural Science Foundation (Grant No. 8991002 and 8041003).
文摘Objective To investigate the seasonal characteristics and the sources of elements and ions with different sizes in the aerosols in Beijing. Methods Samples of particulate matters （PM2,5）, PM10, and total suspended particle （TSP） aerosols were collected simultaneously in Beijing from July 2001 to April 2003. The aerosol was chemically characterized by measuring 23 elements and 18 water-soluble ions by inductively coupled plasma-atomic emission spectroscopy （ICP-AES） and ion chromatography （IC）, respectively. Results The samples were divided into four categories： spring non-dust, spring dust, summer dust, and winter dust. TSP, PM10, and PM2.5 were most abundant in the spring dust, and the least in summer dust. The average mass ratios of PM〉10, PM2,5-10, and PM2.5 to TSP confirmed that in the spring dust both the large coarse （PM〉10） and fine particles （PM2.5） contributed significantly in summer PM2.5, PM2,5-10, and PM〉10 contributed similar fractions to TSP, and in winter much PM2.5. The seasonal variation characteristics of the elements and ions were used to divide them into four groups： crustal, pollutant, mixed, and secondary. The highest levels of crustal elements, such as AI, Fe, and Ca, were found in the dust season, the highest levels of pollutant elements and ions, such as As, F, and Cl^-, were observed in winter, and the highest levels of secondary ions （SO4^2-, NO3^-, and NH4^＋） were seen both in summer and in winter. The mixed group （Eu, Ni, and Cu） showed the characteristics of both crustal and pollutant elements. The mineral aerosol from outside Beijiug contributed more than that from the local part in all the reasons but summer, estimated using a newly developed element tracer technique.
文摘A regional nitrogen cycle model, named IAP-N, was designed for simulating regional nitrogen （N） cycling and calculating N fluxes flowing among cultivated soils, crops, and livestock, as well as human, atmospheric and other systems. The conceptual structure and calculation methods and procedures of this model are described in detail. All equations of the model are presented. In addition, definitions of all the involved variables and parameters are given. An application of the model in China at the national scale is presented. In this example, annual surpluses of consumed synthetic N fertilizer; emissions of nitrous oxide （N2O）, ammonia （NH3） and nitrogen oxide （NOx）; N loss from agricultural lands due to leaching and runoff; and sources and sinks of anthropogenic reactive N （Nr） were estimated for the period 1961-2004. The model estimates show that surpluses of N fertilizer started to occur in the mid 1990s and amounted to 5.7 Tg N yr^-1 in the early 2000s. N20 emissions related to agriculture were estimated as 0.69 Tg N yr^-1 in 2004, of which 58% was released directly from N added to agricultural soils. Total NH3 and NOx emissions in 2004 amounted to 4.7 and 4.9 Tg N yr^-1, respectively. About 3.9 Tg N yr^-1 of N was estimated to have flowed out of the cultivated soil layer in 2004, which accounted for 33% of applied synthetic N fertilizer. Anthropogenic Nr sources changed from 2.8 （1961） to 28.1 Tg N yr^-1 （2004）, while removal （sinks） changed from to 2.1 to 8.4 Tg N yr^-1. The ratio of anthropogenic Nr sources to sinks was only 1.4 in 1961 but 3.3 in 2004. Further development of the IAP-N model is suggested to focus upon： Ca） inter-comparison with other regional N models; （b） overcoming the limitations of the current model version, such as adaptation to other regions, high-resolution database, and so on; and （c） developing the capacity to estimate the safe threshold of anthropogenic Nr source to sink ratios.
基金The Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX1-SW-01-13)
文摘A facility of BaPS （Barometric Process Separation） was used to determine soil respiration, gross nitrification and denitrification in a winter wheat field with depths of 0-7, 7--14 and 14-21 cm. N2O production was determined by a gas chromatograph. Crop root mass and relevant soil parameters were measured. Results showed that soil respiration and gross nitrification decreased with the increase of soil depth, while denitrification did not change significantly. In comparison with no-plowing plot, soil respiration increased significantly in plowing plot, especially in the surface soil of 0-7 cm, while gross nitrification and denitrification rates were not affected by plowing. Cropping practice in previous season was found to affect soil gross nitrification in the following wheat-growing season. Higher gross nitrification rate occurred in the filed plot with preceding crop of rice compared with that of maize for all the three depths of 0-7, 7-14 and 14-21 cm. A further investigation indicated that the nitrification for all the cases accounted for about 76% of the total nitrogen transformation processes of nitrification and denitrification and the N2O production correlated with nitrification significantly, suggesting that nitrification is a key process of soil N2O production in the wheat field. In addition, the variations of soil respiration and gross nitrification were exponentially dependent on root mass （p〈0.00l）.
基金supported by the China Meteorological Administration under Grant GYHY201006024the Chinese Academy of Sciences Strategic Priority Research Program under Grant XDA05110104spon-sorship of National Science Foundation
文摘Utilizing aircraft sounding data collected from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1998) campaign, the authors evaluated commonly-used profile methods for Arctic ABL height estimation by validating against the'true'ABL height from aircraft sounding profiles, where ABL height is defined as the top of the layer with significant turbulence. Furthermore, the best performing method was used to estimate ABL height from the one-year GPS soundings obtained during SHEBA (October 1997-October 1998). It was found that the temperature gradient method produces a reliable estimate of ABL height. Additionally, the authors determined optimal threshold values of temperature gradient for stable boundary layer (SBL) and convective boundary layer (CBL) to be 6.5 K/100 m and 1.0 K/100 m, respectively. The maximum ABL height during the year was 1150 m occurred in May. Median values of Arctic ABL height in May, June, July, and August were 400 m, 430 m, 180 m, and 320 m, respectively. Arctic ABL heights are clearly higher in the spring than in the summer.
基金funded by the National Natural Science Foundation of China (Nos.41175107,41275139)the “Strategic Priority Research Program” of the Chinese Academy of Sciences (Nos.XDA05100100,XDB05020000)
文摘Ground observation data from 8 meteorological stations in Xi＇an, air mass concentration data from 13 environmental quality monitoring sites in Xi＇an, as well as radiosonde observation and wind profile radar data, were used in this study. Thereby, the process,causes and boundary layer meteorological characteristics of a heavy haze episode occurring from 16 to 25 December 2013 in Xi＇an were analyzed. Principal component analysis showed that this haze pollution was mainly caused by the high-intensity emission and formation of gaseous pollutants（NO_2, CO and SO_2） and atmospheric particles（PM_（2.5）（fine particles） and PM10（respirable suspended particle）. The second cause was the relative humidity and continuous low temperature. The third cause was the allocation of the surface pressure field. The presence of a near-surface temperature inversion at the boundary layer formed favorable stratification conditions for the formation and maintenance of heavy haze pollution. The persistent thick haze layer weakened the solar radiation. Meanwhile, a warming effect in the urban canopy layer and in the transition zone from the urban friction sublayer to the urban canopy was indicated. All these conditions facilitated the maintenance and reinforcement of temperature inversion. The stable atmospheric stratification finally acted on the wind field in the boundary layer, and further weakened the exchange capacity of vertical turbulence. The superposition of a wind field with the horizontal gentle wind induced the typical air stagnation and finally caused the deterioration of air quality during this haze event.
基金supported by the Chinese Academy of Science (Grant No. KZCX2-YW-202)National Basic Research Program of China (2006CB403600)National Natural Science Foundation of China (Grant Nos. 40437017 and 40805033).
文摘Based on an intermediate coupled model （ICM）, a probabilistic ensemble prediction system （EPS） has been developed. The ensemble Kalman filter （EnKF） data assimilation approach is used for generating the initial ensemble conditions, and a linear, first-order Markov-Chain SST anomaly error model is embedded into the EPS to provide model-error perturbations. In this study, we perform ENSO retrospective forecasts over the 120 year period 1886-2005 using the EPS with 100 ensemble members and with initial conditions obtained by only assimilating historic SST anomaly observations. By examining the retrospective ensemble forecasts and available observations, the verification results show that the skill of the ensemble mean of the EPS is greater than that of a single deterministic forecast using the same ICM, with a distinct improvement of both the correlation and root mean square （RMS） error between the ensemble-mean hindcast and the deterministic scheme over the 12-month prediction period. The RMS error of the ensemble mean is almost 0.2℃ smaller than that of the deterministic forecast at a lead time of 12 months. The probabilistic skill of the EPS is also high with the predicted ensemble following the SST observations well, and the areas under the relative operating characteristic （ROC） curves for three different ENSO states （warm events, cold events, and neutral events） are all above 0.55 out to 12 months lead time. However, both deterministic and probabilistic prediction skills of the EPS show an interdecadal variation. For the deterministic skill, there is high skill in the late 19th century and in the middle-late 20th century （which includes some artificial skill due to the model training period）, and low skill during the period from 1906 to 1961. For probabilistic skill, for the three different ENSO states, there is still a similar interdecadal variation of ENSO probabilistic predictability during the period 1886~2005. There is high skill in the late 19th century from 1886 to 1905,
基金supported by the National High-Tech Research & Development Program of China (2008AA121703)the National Natural Science Foundation of China (40905056)+3 种基金the State Key Labora-tory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC-KF-2008-11)Beijing Urban Meteorology Research Fund (UMRF-200704)the 11th Five-Year Plan of National Science and Technology Key Project (2008BAC34B04-2)the National Basic Research Program of China (2005CB422200x and 2006CB403702)
文摘Retrieval experiment was made for global total column ozone using the first year measurements of Total Ozone Unit (TOU) on board the second generation polar orbiting meteorological satellite of China, FY-3/A. The retrieval results were analyzed and validated by comparison with AURA/OMI, Meteop/GOME-2 global ozone products and ground-based ozone measurement data. The qualititative comparisons over the globe especially over Antarctica and the Tibetan Plateau show that the spatial and temporal distribution characteristics are consistent with OMI and GOME-2 products. The quantitative comparisons with ground-based measurements and AURA/OMI ozone product were made over 74 stations, the TOU total ozone retrieval has a 3% rms relative error compared with AURA/OMI ozone product and 4.2% rms relative error with ground-based measurements. The maximum difference between satellite retrieval and ground-based measurements was found in the Antarctica ozone hole. The TOU global ozone product is operational and distributed to all users.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (Grant Nos. KZCX2-YW-202 and KZCX1-YW-12-03)National Basic Research Program of China (Grant No. 2006CB403600)National Natural Science Foun-dation of China (Grant Nos. 40805033 and 40221503)
文摘Based on our developed ENSO (El Nio-Southern Oscillation) ensemble prediction system (EPS), the impacts of stochastic initial-error and model-error perturbations on ENSO ensemble predictions are examined and discussed by performing four sets of 14-a retrospective forecast experiments in both a deterministic and probabilistic sense. These forecast schemes are differentiated by whether they considered the initial or model stochastic perturbations. The comparison results suggest that the stochastic model-error perturbations, which are added into the modeled physical fields to mainly represent the uncertainties of the physical model, have significant, positive impacts on improving the ensemble prediction skills during the entire 12-month forecast process. However, the stochastic initial-error perturbations have relatively small impacts on the ensemble prediction system, and its impacts are mainly focusing on the first 3-month predictions.
基金supported by Chinese Academy of Sciences Strategic Priority Research Program Grant(XDB05020000,XDA05100100)the National Natural Science Foundation of China(41230642,41021004,41203053)
文摘When gasoline is burned to power an automotive engine, a portion of the fuel remains unburned or is partially burned and leaves the engine as hydrocarbon and oxygenated compounds. In addition, a small portion of the fuel can escape the vehicle through evaporation. Changes in alkanes, olefins and aromatics each affect emissions differently, which could complicate control strategies for air pollution. In this study, we collected 31 gasoline samples over five provinces and cities(Beijing, Tianjin, Hebei, Shandong, and Shaanxi) in North China between 2012 and 2013. The organic composition of the gasoline samples was analyzed using the gas chromatography-mass spectrometry(GC-MS) method, and the aniline compounds were analyzed by solvent extraction and the GC-MS method. The ratios of alkanes, aromatics, olefins and other organic compounds in gasoline were 40.6%, 38.1%, 12.9% and 8.4%, respectively. The aromatic and benzene exceedances were 15 and 8 based on the China's gasoline standards(III), and they accounted for 48.4% and 25.8% of all the gasoline samples, respectively. Strong carcinogen aniline compounds were detected in all 31 samples, and the content of aniline compounds in 3 samples exceeded 1%. The high proportion of aromatics and olefins in the gasoline increased the emissions of carbon monoxide(CO) and toxics, as well as the atmospheric photochemical reactivity of exhaust emissions, which could hasten the formation of secondary pollutants. Our results are helpful for redefining government strategies to control air pollution in North China and relevant for developing new refining technology throughout China.
基金Supported by the China Meteorological Administration Special Public Welfare Research Fund(GYHY201206041)National (Key) Basic Research and Development(973)Program of China(2009CB421403)+2 种基金National Natural Science Foundation of China(40905067)Public Science and Technology Research Projects of Ocean(201005017-5)Antarctic and Arctic Environmental Expeditions and Assessment Project(CHINARE2012-02-03 and 2012-04-04)
文摘The Tibetan Plateau has substantial impacts on the weather and climate of the Northern Hemisphere, due in large part to the thermal effects of the plateau surface. Surface temperature over the Tibetan Plateau is the most important parameter in determining these thermal effects. We present a method for verifying widely used reanalysis temperature products from NCEP-R2, ERA-Interim, and JRA-25 over the Tibetan Plateau, with the aim of obtaining a reliable picture of surface temperature and its changes over the plateau. Reanalysis data are validated against the topography elevation, satellite observations, and radiosonde data. ERA-Interim provides the most reliable estimates of Tibetan Plateau surface temperature among these three reanalyses. We therefore use this dataset to study the climatology and trends of surface temperature over the Tibetan Plateau. ERA-Interim data indicate a dramatic warming over the Tibetan Plateau from 1979 to 2010, with warming rates of 0.33℃ per decade in annual mean temperature, 0.22℃ per decade in summer and 0.4℃ per decade in winter mean temperatures. Comparison with the results of previous studies suggests that surface warming over the Tibetan Plateau has accelerated during the past 30 years. This warming is distributed heterogeneously across the Tibetan Plateau, possibly due to topographic effects.
基金supported by the Chinese Academy of Sciences Strategic Priority Research Program Grant (No.: XDB05020000)the National Natural Science Foundation of China (No. 41230642)the National key technology research and development program of the ministry of Science and technology of China (No. 2014BAC22B06)
文摘Vehicular emissions in China in 2006 and 2010 were calculated at a high spatial resolution based on the data released by the National Bureau of Statistics, by taking the emission standards into consideration. China＇s vehicular emissions of carbon monoxide （CO）, nitrogen oxides （NOx）, volatile organic compounds （VOCs）, ammonia （NH3）, fine particulate matters （PM2.5）, inhalable particulate matters （PMlo）, black carbon （BC）, and organic carbon （OC） were 30,113.9, 4593.7, 6838.0, 20.9, 400.2, 430.5,285.6, and 105.1 Gg, respectively, in 2006 and 34,175.2, 5167.5, 7029.4, 74.0, 386.4, 417.1, 270.9, and 106.2 Gg, respectively, in 2010. CO, VOCs, and NH3 emissions were mainly from motorcycles and light-duty gasoline vehicles, whereas NOx, PMzs, PMlo, and BC emissions were mainly from rural vehicles and heavy- duty diesel trucks. OC emissions were mainly from motorcycles and heavy-duty diesel trucks. Vehicles of pre-China I （vehicular emission standard of China before phase I） and China I （vehicular emission standard of China in phase I） were the primary contributors to all of the pollutant emissions except NH3, which was mainly from China III and China IV gasoline vehicles. The total emissions of all the pollutants except NH3 changed little from 2006 to 2010. This finding can be attributed to the implementation of strict emission standards and to improvements in oil quality.
基金supported by the Chinese Academy of Sciences (Grant No. KZCX2-YW-202)the 973 Pro-gram (Grant No. 2006CB403606),the 863 Program (Grant No.2009AA12Z138)the National Natural Science Foundation of China (Grant Nos. 40606008,40437017,and 40221503)
文摘An ocean reanalysis system for the joining area of Asia and Indian-Pacific Ocean (AIPO) has been developed and is currently delivering reanalysis data sets for study on the air-sea interaction over AIPO and its climate variation over China in the inter-annual time scale.This system consists of a nested ocean model forced by atmospheric reanalysis,an ensemble-based multivariate ocean data assimilation system and various ocean observations.The following report describes the main components of the data assimilation system in detail.The system adopts an ensemble optimal interpolation scheme that uses a seasonal update from a free running model to estimate the background error covariance matrix.In view of the systematic biases in some observation systems,some treatments were performed on the observations before the assimilation.A coarse resolution reanalysis dataset from the system is preliminarily evaluated to demonstrate the performance of the system for the period 1992 to 2006 by comparing this dataset with other observations or reanalysis data.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant KZCX2-YW-205)the National Natural Science Foundation of China (Grant Nos.40825016,90711004,and 40775083)
文摘In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature and precipitation during the severe snowstorm that occurred in southern China during 0800 26 January to 0800 29 January 2008 （Note that all times are local time except when otherwise stated）. Black carbon aerosol was simulated online within the WRF-Chem. The model resuits showed that surface-albedo, averaged over 27-28 January, can be reduced by up to 10% by the deposition of BC. As a result, relative to a simulation that does not consider deposition of BC on snow/ice, the authors predicted surface air temperatures during 27-28 January can differ by -1.95 to 2.70 K, and the authors predicted accumulated precipitation over 27-28 January can differ by -2.91 to 3.10 mm over Areas A and B with large BC deposition. Different signs of changes are determined by the feedback of clouds and by the availability of water vapor in the atmosphere.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 90715031, 40775018, and 40875008the National Science & Technology Pillar Program under Grant No. 2008BAC37B00
文摘The wind data of four typhoons were obtained and analyzed. The wind speeds were measured by sonic anemometers at four observation sites in Guangdong and Hainan provinces. Detailed analysis of the wind data was conducted to investigate the turbulence characteristics of the typhoons. Characteristics of the gust factor and the turbulence integral scale of the typhoons were concluded with high confidence. The relationships among the gust factor, gust duration time, mean wind speed, roughness length, and turbulence intensity were described. The turbulence integral scale was found to be closely related to the segment length and turbulence intensity.
