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| 1 | Modeling study of regional severe hazes over mid-eastern China in January 2013 and its implications on pollution prevention and control显示文摘The Nested Air Quality Prediction Model System(NAQPMS)was used to investigate the temporal and spatial variations of PM2.5over tropospheric central eastern China in January 2013.The impact of regional transport and its implications on pollution prevention and control were also examined.Comparison between simulated and observed PM2.5showed NAQPMS was able to reproduce the evolution of PM2.5during heavy haze episodes.The results indicated that regional transport of PM2.5played an important role in regional haze episodes in the city cluster including Hebei,Beijing and Tianjin(HBT).The cross-city clusters transport outside HBT and transport among cities inside HBT contributed 20%–35%and 26%–35%of PM2.5as compared with local emission,in HBT respectively.To meet the Air Quality Standards for Grade II,90%,90%and65%of emissions would have to be cut down in Hebei,Tianjin and Beijing,if non-control strategy was taken in the surrounding city clusters of HBT.This implicated that control of emissions in one city cluster is not sufficient to reduce regional haze events,and joint efforts among city clusters are essential.Besides regional transports,two-way feedback between boundary-layer evolution and PM2.5also significantly contributed to the formation of heavy hazes,which contributed 30%of monthly average PM2.5concentration in HBT. | WANG ZiFa LI Jie WANG Zhe YANG WenYi TANG Xiao GE BaoZhu YAN PinZhong ZHU LiLi CHEN XueShun CHEN HuanSheng WAND Wei LI JianJun LIU Bing WANG XiaoYan WAND Wei ZHAO YiLin LU Ning SU DeBin | 2014 | Science China Earth Sciences2014，57，1： | 106 |
| 2 | A preliminary report on the Great Wenchuan Earthquake显示文摘The May 12, 2008 Great Wenchuan Earthquake has resulted in more than 68,858 deaths and losses in the hundreds of billions RMB as of May 30, 2008, and these numbers will undoubtedly increase as more information becomes available on the extent of the event. Immediately after the earthquake, the China Earthquake Administration (CEA) responded quickly by sending teams of experts to the affected region, eventually including over 60 staff members from the Institute of Engineering Mechanics (IEM). This paper reports preliminary information that has been gathered in the first 18 days after the event, covering seismicity, search and rescue efforts, observed ground motions, and damage and loss estimates. The extensive field investigation has revealed a number of valuable findings that could be useful in improving research in earthquake engineering in the future. Once again, this earthquake has shown that the vertical component of ground motion is as significant as horizontal ground motions in the near-source area. Finally, note that as more information is gathered, the numbers reported in this paper will need to be adjusted accordingly. | Wang Zifa | 2008 | Earthquake Engineering and Engineering Vibration2008，7，2： | 35 |
| 3 | Effect of urbanization on the winter precipitation distribution in Beijing area显示文摘According to the urbanization extent of Beijing area, and with 1980 as a turning point, the duration from 1961 to 2000 is divided into two periods: one is defined as the slow urbanization period from 1961 to 1980, and other one as the fast urbanization period from 1981 to 2000. Based on the 40-year’s precipi-tation data of 14 standard weather stations in Beijing area, the effect of urbanization on precipitation distribution is studied. It is found that there has been a noticeable and systematic change of winter precipitation distribution pattern between these two periods in Beijing area: in the slow urbanization period, the precipitation in the southern part of Beijing is more than that in the northern part; but in the fast urbanization period, the precipitation distribution pattern is reverse, i.e. the precipitation in the southern part is less than that in the northern part; But in other seasons, the precipitation distribution pattern did not change remarkably in general. The possible cause resulting in the change of winter precipitation distribution pattern, might be that with urban area extension, the effects of 'urban heat island' and 'urban dry island' become more and more intensified, and increase hydrometeors evapo-ration below precipitable cloud, and then cause less precipitation received on the ground surface in the downtown and the southern part. It is also noteworthy to further research why the precipitation distri-bution pattern does not change systematically in other seasons except winter after intense urbaniza-tion in Beijing area. | WANG XiQuan WANG ZiFa QI YanBin GUO Hu | 2009 | Science China Earth Sciences2009，52，2： | 13 |
| 4 | Investigating the Transport Mechanism of PM2.5 Pollution during January 2014 in Wuhan, Central China显示文摘Severe haze pollution that occurred in January 2014 in Wuhan was investigated. The factors leading to Wuhan’s PM2.5 pollution and the characteristics and formation mechanism were found to be significantly different from other megacities, like Beijing. Both the growth rates and decline rates of PM2.5 concentrations in Wuhan were lower than those in Beijing, but the monthly PM2.5 value was approximately twice that in Beijing. Furthermore, the sharp increases of PM2.5 concentrations were often accompanied by strong winds. A high-precision modeling system with an online source-tagged method was established to explore the formation mechanism of five haze episodes. The long-range transport of the polluted air masses from the North China Plain (NCP) was the main factor leading to the sharp increases of PM2.5 concentrations in Wuhan, which contributed 53.4% of the monthly PM2.5 concentrations and 38.5% of polluted days. Furthermore, the change in meteorological conditions such as weakened winds and stable weather conditions led to the accumulation of air pollutants in Wuhan after the long-range transport. The contribution from Wuhan and surrounding cities to the PM2.5 concentrations was determined to be 67.4% during this period. Under the complex regional transport of pollutants from surrounding cities, the NCP, East China, and South China, the five episodes resulted in 30 haze days in Wuhan. The findings reveal important roles played by transregional and intercity transport in haze formation in Wuhan. | Miaomiao LU Xiao TANG Zifa WANG Lin WU Xueshun CHEN Shengwen LIANG Hui ZHOU Huangjian WU Ke HU Longjiao SHEN Jia YU Jiang ZHU | 2019 | Advances in Atmospheric Sciences2019，36，11： | 10 |
| 5 | Probabilistic Automatic Outlier Detection for Surface Air Quality Measurements from the China National Environmental Monitoring Network显示文摘Although quality assurance and quality control procedures are routinely applied in most air quality networks, outliers can still occur due to instrument malfunctions, the influence of harsh environments and the limitation of measuring methods. Such outliers pose challenges for data-powered applications such as data assimilation, statistical analysis of pollution characteristics and ensemble forecasting. Here, a fully automatic outlier detection method was developed based on the probability of residuals, which are the discrepancies between the observed and the estimated concentration values. The estimation can be conducted using filtering—or regressions when appropriate—to discriminate four types of outliers characterized by temporal and spatial inconsistency, instrument-induced low variances, periodic calibration exceptions, and less PM_(10) than PM_(2.5) in concentration observations, respectively. This probabilistic method was applied to detect all four types of outliers in hourly surface measurements of six pollutants(PM_(2.5), PM_(10),SO_2,NO_2,CO and O_3) from 1436 stations of the China National Environmental Monitoring Network during 2014-16. Among the measurements, 0.65%-5.68% are marked as outliers. with PM_(10) and CO more prone to outliers. Our method successfully identifies a trend of decreasing outliers from 2014 to 2016,which corresponds to known improvements in the quality assurance and quality control procedures of the China National Environmental Monitoring Network. The outliers can have a significant impact on the annual mean concentrations of PM_(2.5),with differences exceeding 10 μg m^(-3) at 66 sites. | Huangjian WU Xiao TANG Zifa WANG Lin WU Miaomiao LU Lianfang WEI Jiang ZHU | 2018 | Advances in Atmospheric Sciences2018，35，12： | 10 |
| 6 | Evaluation of the effect of air pollution control during the Beijing 2008 Olympic Games using Lidar data显示文摘To examine the effect of pollution control measures on Beijing air quality during the 2008 Olympic Games, this paper analyzes the variation of aerosol extinction coefficient observed with a Dual-wavelength Polarized Lidar in Beijing during the Olympic Games. The results show that (1) during the Beijing Olympic Games, the aerosol extinction coefficient decreased to about 42.3% in the surface layer (below 250 m) compared with that in 2007 under almost the same meteorological conditions, indicating the effectiveness of local air pollution control measures in Beijing areas; (2) the analysis of the aerosol extinction coefficient obtained before (Jul. 20–Aug. 7, 2008) and during the Beijing Olympic Games (Aug. 8–Aug. 24, 2008) shows a maximum decrease of daily aerosol extinction coefficient in layer of 0.5-1.5 km. To elucidate such a phenomenon, the transport of PM10 from surrounding areas to Beijing was simulated by NAQPMS (the Nested Air Quality Prediction Modeling System) during Jul. 20 to Aug. 24, 2008. Analysis of PM10 transport from neighboring areas indicated a decrease of 36.6% during the Olympic Games. This demonstrated the efficiency of pollution control measures in surrounding areas in improving air quality in Beijing. | YANG Ting WANG ZiFa ZHANG Bai WANG XiQuan WANG Wei GBAUIDI Alex GONG YanBang | 2010 | Chinese Science Bulletin2010，55，13： | 9 |
| 7 | Optimal Planning of Charging Station for Electric Vehicle Based on Quantum PSO Algorithm显示文摘 | LIU Zifa ZHANG Wei WANG Zeli | 2012 | 中国电机工程学报2012，32，22： | 9 |
| 8 | Distributed reinforcement learning to coordinate current sharing and voltage restoration for islanded DC microgrid显示文摘A novel distributed reinforcement learning(DRL)strategy is proposed in this study to coordinate current sharing and voltage restoration in an islanded DC microgrid.Firstly, a reward function considering both equal proportional current sharing and cooperative voltage restoration is defined for each local agent. The global reward of the whole DC microgrid which is the sum of the local rewards is regarged as the optimization objective for DRL. Secondly,by using the distributed consensus method, the predefined pinning consensus value that will maximize the global reward is obtained. An adaptive updating method is proposed to ensure stability of the above pinning consensus method under uncertain communication. Finally, the proposed DRL is implemented along with the synchronization seeking process of the pinning reward, to maximize the global reward and achieve an optimal solution for a DC microgrid. Simulation studies with a typical DC microgrid demonstrate that the proposed DRL is computationally efficient and able toprovide an optimal solution even when the communication topology changes. | Zifa LIU Ya LUO Ranqun ZHUO Xianlin JIN | 2018 | Journal of Modern Power Systems and Clean Energy2018，6，2： | 7 |
| 9 | Air quality during the 2008 Beijing Olympic Games显示文摘 | David G. Streets Joshua S. Fu Carey J. Jang Jiming Hao Kebin He Xiaoyan Tang Yuanhang Zhang Zifa Wang Zuopan Li Qiang Zhang Litao Wang Binyu Wang Carolyne Yu | 2006 | Atmospheric Environment2006，，3： | 6 |
| 10 | Modeling study of source contributions and emergency control effects during a severe haze episode over the Beijing-Tianjin-Hebei area显示文摘In February 2014, the Beijing-Tianjin-Hebei(BTH) area experienced a weeklong episode of heavy haze pollution. Cities such as Beijing(BJ) and Shijiazhuang(SJZ) issued heavy pollution alerts for the first time and took emergency control measures. This study employed the Nested Air Quality Prediction Modeling System(NAQPMS) to simulate and analyze the three-dimensional structure of the source contributions of PM2.5 in the BTH area during this pollution episode and quantitatively assessed the effects of the emergency control measures. The results showed that during the polluted period(February 19–26), surface PM2.5 mainly originated from local sources(48%–72%). In the entire BTH area, southern Hebei(SHB) represented the largest internal contribution(33%), while the main external contributions came from Shandong(SD)(10%) and Henan(HN)(4%). Vertically, the local contribution was constrained below the near-ground layer, and rapidly decreased with altitude. The regional transport path from SHB and Shanxi(SX) to BJ appeared at 0.5–1.5 and 1.5–2.5 km, with contributions of 32%–42% and 13%–27%, respectively. The non-local source regions for the BTH area were SD below 1 km and mainly SX and HN above 1 km. Compared to the non-polluted period(February 27–28), the contribution from regional transport increased during the polluted period, indicating the key role of regional transport in the pollution formation. The emergency control measures had a relatively large effect on NOx and SO2 concentrations, but a limited effect on PM2.5. The stronger regional transport during the polluted period may have weakened the effects of the local emergency control measures. These results indicated that a coordinated emission control should be implemented not only over the BTH area but also over its surrounding provinces(e.g. SD, HN). | Huansheng Chen Jie Li Baozhu Ge Wenyi Yang Zifa Wang Si Huang Yuanlin Wang Pingzhong Yan Jianjun Li Lili Zhu | 2015 | Science China Chemistry2015，58，9： | 5 |
| 11 | Simulating Dry Deposition Fluxes of PM_(10) and Particulate Inorganic Nitrogen over the Eastern China Seas During a Severe Asian Dust Event Using WRF-Chem Model显示文摘A WRF-Chem model including a comprehensive gas-phase nitrogen chemistry module was used to simulate a severe dust event appearing in the eastern China on 19-25 March, 2002. The modeling result well reproduced PM10 concentrations in various distances from the dust sources and the transport pathway of the dust strom. The results showed that both the concentrations and the dry deposition fluxes of PM10 increased over the China seas during the dust event following the passage of a cold front system. The maximum fluxes of PM10 in the Yellow Sea and the East China Sea during the dust event were 5.5 and 8.4 times of those before the event, respectively. However, the temporal variations of the dry deposition fluxes of particulate inorganic nitrogen differed over the Yellow Sea from those over the East China Sea. Nitrate and ammonium in the whole northern China rapidly decreased because of the intrusion of dust-loaded air on 19 March. The dust plume arrived in the Yellow Sea on 20 March, decreasing the particulate inorganic nitrogen in mass concentration accordingly. The minimum dry deposition fluxes of nitrate and ammonium in the Yellow Sea were about 3/5 and 1/6 of those before the dust arrival, respectively. In contrast, when the dust plume crossed over the Yangtze Delta area, it became abundant in nitrate and ammonium and increased the concentrations and dry deposition fluxes of particulate inorganic nitrogen over the East China Sea, where the maximum dry deposition fluxes of nitrate and ammonium increased approximately by 4.1 and 2.6 times of those prior to the dust arrival. | YAN Han GAO Huiwang YAO Xiaohong WANG Zifa | 2012 | Journal of Ocean University of China2012，11，3： | 5 |
| 12 | Chemical formation and source apportionment of PM_(2.5) at an urban site at the southern foot of the Taihang mountains显示文摘The region along the Taihang Mountains in the North China Plain(NCP) is characterized by serious fine particle pollution. To clarify the formation mechanism and controlling factors, an observational study was conducted to investigate the physical and chemical properties of the fine particulate matter in Jiaozuo city, China. Mass concentrations of the water-soluble ions(WSIs) in PM_(2.5) and gaseous pollutant precursors were measured on an hourly basis from December 1, 2017, to February 27, 2018. The positive matrix factorization(PMF) method and the FLEXible PARTicle(FLEXPART) model were employed to identify the sources of PM_(2.5). The results showed that the average mass concentration of PM_(2.5) was 111 μg/m^(3) during the observation period. Among the major WSIs, sulfate, nitrate, and ammonium(SNA) constituted 62% of the total PM_(2.5) mass, and NO_(3)^(-) ranked the highest with an average contribution of 24.6%. NH_(4)^(+) was abundant in most cases in Jiaozuo. According to chemical balance analysis, SO_(2)-4, NO_(3)^(-), and Cl^(-) might be present in the form of(NH_4)_(2)SO_4, NH_4NO_3, NH_4Cl, and KCl. The liquid-phase oxidation of SO_(2) and NO_(2) was severe during the haze period. The relative humidity and pH were the key factors influencing SO_(4)^(2-) formation. We found that NO_(3)^(-) mainly stemmed from homogeneous gas-phase reactions in the daytime and originated from the hydrolysis of N_(2)O_5 in the nighttime, which was inconsistent with previous studies. The PMF model identified five sources of PM_(2.5) : secondary origin(37.8%), vehicular emissions(34.7%), biomass burning(11.5%), coal combustion(9.4%), and crustal dust(6.6%). | Xiaoyong Liu Mingshi Wang Xiaole Pan Xiyue Wang Xiaolong Yue Donghui Zhang Zhigang Ma Yu Tian Hang Liu Shandong Lei Yuting Zhang Qi Liao Baozhu Ge Dawei Wang Jie Li Yele Sun Pingqing Fu Zifa Wang Hong He | 2021 | Journal of Environmental Sciences2021，33，5： | 5 |
| 13 | Observation of Wind Shear during Evening Transition and an Estimation of Submicron Aerosol Concentrations in Beijing Using a Doppler Wind Lidar显示文摘The wind speed and direction measured over six months by a Doppler wind lidar(Windcube-8)were compared with wind cup anemometers mounted on the 325-m Beijing meteorological tower(BMT).Five mountain–plain wind cases characterized by wind direction shear were selected based on the high-frequency(1.1 s)wind profile of the Windcube-8 and analyzed with 1-h mesoscale surface weather charts.Also analyzed was the relationship between insitu PM_1(aerodynamic diameter≤1μm)concentrations measured at 260 m on BMT and the carrier-to-noise ratio(CNR)of the co-located Windcube-8.The results showed that the 10-min averaged wind speed and direction were highly correlated(R=0.96–0.99)at three matched levels(80,140,and 200 m).The evening transition duration was1–3 h,with an average wind speed of 1 m s^(–1) at 80 m above the ground.In addition,there was a zero horizontalwind-speed zone along the wind direction shear line,and in one case,the wind speed was characterized by a Kelvin–Helmholtz gravity wave.The variability of the PM_1 concentrations was captured by the CNR of the Windcube-8 in a fair weather period without the long-range transport of dust. | Yong CHEN Junling AN Xiquan WANG Yele SUN Zifa WANG Jing DUAN | 2017 | Journal of Meteorological Research2017，31，2： | 5 |
| 14 | Improving simulations of sulfate aerosols during winter haze over Northern China: the impacts of heterogeneous oxidation by NO2显示文摘 | Meng Gao Gregory R. Carmichael Yuesi Wang Dongsheng Ji Zirui Liu Zifa Wang | 2016 | Frontiers of Environmental Science & Engineering2016，10，5： | 4 |
| 15 | Deep learning for P-wave arrival picking in earthquake early warning显示文摘Fast and accurate P-wave arrival picking significantly affects the performance of earthquake early warning(EEW)systems.Automated P-wave picking algorithms used in EEW have encountered problems of falsely picking up noise,missing P-waves and inaccurate P-wave arrival estimation.To address these issues,an automatic algorithm based on the convolution neural network(DPick)was developed,and trained with a moderate number of data sets of 17,717 accelerograms.Compared to the widely used approach of the short-term average/long-term average of signal characteristic function(STA/LTA),DPick is 1.6 times less likely to detect noise as a P-wave,and 76 times less likely to miss P-waves.In terms of estimating P-wave arrival time,when the detection task is completed within 1 s,DPick′s detection occurrence is 7.4 times that of STA/LTA in the 0.05 s error band,and 1.6 times when the error band is 0.10 s.This verified that the proposed method has the potential for wide applications in EEW. | Wang Yanwei Li Xiaojun Wang Zifa Shi Jianping Bao Enhe | 2021 | Earthquake Engineering and Engineering Vibration2021，20，2： | 3 |
| 16 | Composition and mixing state of water soluble inorganic ions during hazy days in a background region of North China显示文摘Knowledge of haze particles in background areas of North China is limited, although they have been studied well in urban settings. Atmospheric aerosol particles were collected at a background site in the North China Plain during 16–31 January, 2011. Water soluble inorganic ions of PM2.5 and physicochemical characteristics of individual particles on hazy and clean days were measured by Ion Chromatography(IC) and Transmission Electron Microscopy(TEM), respectively. Average PM2.5 mass concentration was 50.4±29.9 μg m?3 with 62.5±26.8 μg m?3 on hazy days and 19.9±11.5 μg m?3 on clean days. SO42?, NO3?, and NH4+ with a combined mass concentration of 19.0±11.5 μg m?3 accounted for 69.8%–89.4% of the total water soluble inorganic ions. Size distributions of SO42? and NH4+ showed one unimodal peak at 0.56–1.8 μm on hazy days, whereas NO3? appeared as bimodal peaks at 0.56–1.8 and 5.6–10 μm, respectively. Individual particle analyses showed that the dominant aerosols were a mixture of sulfate, nitrate, and carbonaceous species, which together determine their mixing states. 48-h air mass back trajectories on hazy days suggested that air masses crossed the polluted continental areas(such as Jing-jin-ji region and Shandong province) and entrained ground air pollutants 11–19 hours before reaching the background area. During long-range transport particles undergo ageing and tend to be internally mixed mainly due to condensation in the background atmosphere. Our results suggest that hygroscopic and optical properties of these aerosol particles in the background area differ substantially from those in urban areas. | LU YaLing CHI JianWei YAO Lan YANG LingXiao LI WeiJun WANG ZiFa WANG WenXing | 2015 | Science China Earth Sciences2015，58，11： | 3 |
| 17 | Seasonal variation of the temperature profile and its characteristics within urban roughness sublayer显示文摘By using conventional micro-meteorological observation data of Beijing Yuetan Park Tower (180 m), the temperature profile of urban boundary layer (UBL), its characteristics and seasonal variation are analyzed. The main results are as follows: (1) In winter, the interdiurnal surface air temperature varia- tion at the surface is not synchronized with that of the upper levels, other than in summer and other seasons, which illuminates the impacts of Beijing’s geographical location, sky view factor and stably stratified nocturnal inversion. (2) Except that the stratification is unstable around noon, the stratifica- tion in the roof layer or above-roof layer is of seasonal variability, which is weak unstable or weak sta- ble in winter or summer respectively. This weak stable stratification possibly inhibits urban pollutant dispersion upwards in summer season. (3) The effect of urban building rooftop on the UBL thermal state has seasonal difference, that is, the rooftop plays the role of heating or cooling the urban roughness sublayer, in summer or winter respectively, which is similar to the effects of the Qing- hai-Tibet Plateau on the atmospheric thermal state. | WANG XiQuan WANG ZiFa GUO HU | 2009 | Chinese Science Bulletin2009，54，3： | 3 |
| 18 | Ambient TSP concentration and dustfall variation in Urumqi,China显示文摘Total suspended particulate(TSP, particle diameter≤100 μm) was the dominant air pollutant and significantly influenced local air quality. In this paper, we investigated the interannual and seasonal variations of TSP and dustfall of the atmosphere over Urumqi, the capital city of Xinjiang Uygur autonomous region, northwestern China, basing on environmental monitoring records and meteorological data from 1986–2012. The results showed that during the study period, annual average TSP concentration decreased from 716 to 260 μg/m3, with an average level of 422.9 μg/m3, while dustfall intensity reduced from 350.4 to 166.6 t/(km2?a), with an average level of 259 t/(km2?a). Over 50% of the annual pollution days were induced mainly by TSP. Spring and winter had relatively higher dustfall intensities, and dense traffic and residential areas had the highest dustfall intensities in the Urumqi metropolitan area. With an annual average precipitation of less than 300 mm, atmospheric particulates in Urumqi could be hardly removed through wet deposition. During spring and summertime prevailing winds from northwest and northeast could carry aeolian dust particles from sandy deserts to Urumqi. Aeolian dusts from deserts would remain to be a priority regarding air pollution control in arid oasis cities. | XiaoXiao ZHANG Xi CHEN YuHong GUO ZiFa WANG LianYou LIU Cottle PAUL ShengYu LI HuaWei PI | 2014 | Journal of Arid Land2014，6，6： | 3 |
| 19 | Evolutionary processes and sources of high-nitrate haze episodes over Beijing,Spring显示文摘Rare and consecutive high-nitrate haze pollution episodes were observed in Beijing in spring2012. We present detailed characterization of the sources and evolutionary mechanisms of this haze pollution, and focus on an episode that occurred between 15 and 26 April. Submicron aerosol species were found to be substantially elevated during haze episodes, and nitrates showed the largest increase and occupation(average: 32.2%) in non-refractory submicron particles(NR-PM_1), which did not occur in other seasons as previously reported. The haze episode(HE) was divided into three sub-episodes, HEa, HEb, and HEc. During HEa and HEc, a shallow boundary layer, stagnant meteorological conditions, and high humidity favored the formation of high-nitrate concentrations, which were mainly produced by three different processes —daytime photochemical production, gas-particle partitioning, and nighttime heterogeneous reactions — and the decline in visibility was mainly induced by NR-PM_1.However, unlike HEa and HEc, during HEb, the contribution of high nitrates was partly from the transport of haze from the southeast of Beijing — the transport pathway was observed at ~800–1000 m by aerosol Lidar —and the decline in visibility during HEb was primarily caused by PM_(2.5). Our results provide useful information for air quality improvement strategies in Beijing during Spring. | Ting Yang Yele Sun Wei Zhang Zifa Wang Xingang Liu Pingqing Fu Xiquan Wang | 2017 | Journal of Environmental Sciences2017，29，4： | 2 |
| 20 | Nocturnal Low-levelWinds and Their Impacts on Particulate Matter over the Beijing Area显示文摘Three-month wind profiles, 260 m PM_1 concentrations [i.e., particulate matter(PM) with an aerodynamic diameter ≤1μm], and carrier-to-noise ratio data at two Beijing sites 55 km apart(urban and suburban) were collected to analyze the characteristics of low-level nocturnal wind and PM in autumn and winter. Three mountain-plain wind events with wind shear were selected for analysis. The measurements indicated that the maximum wind speeds of the northerly weak low-level jet(LLJ) below 320 m at the suburban site were weaker than those at the urban site, and the LLJ heights and depths at the suburban site were lower than those at the urban site. The nocturnal 140 m mean vertical velocities and the variations in vertical velocity at the urban site were larger than those at the suburban site. A nocturnal breeze with a weak LLJ of ~3 m s^(-1) noticeably offset nocturnal PM transport due to southerly flow and convergence within the northern urban area of Beijing. Characteristics of the nocturnal LLJ, such as start-up time, structure, intensity, and duration, were important factors in determining the decrease in the nocturnal horizontal range and site-based low-level variations in PM. | Yong CHEN Junling AN Yele SUN Xiquan WANG Yu QU Jingwei ZHANG Zifa WANG Jing DUAN | 2018 | Advances in Atmospheric Sciences2018，35，12： | 2 |
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