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1.
In-situ sodar and lidar measurements were coupled with numerical simulations for studying a sea-breeze event in a flat coastal area of the North Sea. The study’s aims included the recognition of the dynamics of a sea-breeze structure, and its effects on the lower troposphere stratification and the three-dimensional (3D) pollutant distribution. A sea breeze was observed with ground-based remote sensing instruments and analysed by means of numerical simulations using the 3D non-hydrostatic atmospheric model Meso-NH. The vertical structure of the lower troposphere was experimentally determined from the lidar and sodar measurements, while numerical simulations focused on the propagation of the sea breeze inland. The sea-breeze front, the headwind, the thermal internal boundary layer, the gravity current and the sea-breeze circulation were observed and analysed. The development of a late stratification was also observed by the lidar and simulated by the model, suggesting the formation of a stable multilayered structure. The transport of passive tracers inside the sea breeze and their redistribution above the gravity current was simulated too. Numerical modelling showed that local pollutants may travel backward to the sea above the gravity current at relatively low speed due to the shearing between the landward gravity current and the seaward synoptic wind. Such dynamic conditions may enhance an accumulation of pollutants above coastal industrial areas.  相似文献   

2.
基于激光雷达探测设备、风廓线雷达、探空以及常规地面探测设备,研究了乌鲁木齐2017年3月5—12日一次重污染过程气溶胶光学特性的垂直分布特征及重污染成因。结果表明:此次重污染过程中7—10日PM2.5日平均值分别为176、215.5、215.9μg/m3和176.3μg/m3,最高时刻达到364μg/m3;激光雷达探测结果表明污染物主要集中在600 m以下,且午后—傍晚阶段的消光系数是夜间的7倍左右;污染物的退偏振很小,结合探空湿度廓线得到混合层内相对湿度基本80%,说明气溶胶颗粒主要为水凝物的球形粒子。由风廓线雷达结果得到乌鲁木齐站附近500 m高度以下水平风速普遍低于2 m/s;从北到南地面5个加密气象站的小风频率依次为99%、100%、81%、48%和67%。在市中心高新区附近受城市建筑物的阻挡,整个污染过程中平均风速仅为0.66 m/s;靠近峡口的乌拉泊风速最大,平均风速达到2.3 m/s,重污染阶段7—9日的平均边界层高度为433 m,低的边界层高度和低风速是造成此次污染的主要原因。  相似文献   

3.
Simulation of local atmospheric dynamics in the coastal region of Dunkerque   总被引：1，自引：0，他引：1  
The structure of the lower troposphere has been studied during the sea-breeze and post sea-breeze events in an industrialized coastal area of the North Sea. Atmospheric dynamics and dispersion of pollutants in the lower troposphere have been analyzed by the experimental results of the 3D nonhydrostatic Meso-NH model in Dunkerque area (51°N, 2.20°E), in the north of France. The simulations were verified and extended by data of the measurement campaign. Ground-based remote sensing systems (lidar and sodar), surface meteorology and air quality network stations data have been employed. We illustrate the different pollution scenarios and breeze structure by the analysis of Lagrangian tracers and back trajectories.  相似文献   

4.
Functional relationships linking at λ0=351 nm aerosol extinction αλ0aer and backscatter coefficient βλ0aer of maritime and desert type aerosols are determined to allow for inversion of the single-wavelength lidar signals. Such relationships are derived as mean behavior of 20,000 extinction versus backscatter computations, performed for aerosol size distributions and compositions whose describing parameters are randomly chosen within the naturally observed variability. For desert-type aerosols, the effect of the particle non-sphericity is considered and it is shown that the extinction to backscatter ratio of non-spherical dust particles can be up to 60% larger than the values obtained for spherical particles. Aerosol extinction and backscatter coefficient profiles obtained inverting the single-wavelength lidar signal with the modeled relationships are then compared to the same profiles measured by a combined elastic-Raman lidar operating at 351 nm. Analytical back trajectories and satellite images are used to characterize advection patterns during lidar measurements and to properly choose the modeled functional relationship. A good accordance between the two techniques is found for advection patterns over the lidar site typical of maritime and dust conditions. Maximum differences between the model-based αλ0aer and βλ0aer vertical profiles and the corresponding ones measured by the combined elastic-Raman lidar technique are of 30% and 40% in maritime and desert dust conditions, respectively. The comparison of elastic-Raman lidar measurements and model-based results also reveals that particle non-sphericity must be taken into account when mineral dust-type aerosols are directly advected over the measurement site.  相似文献   

5.
2019年3月,利用相干多普勒测风激光雷达首次在辽东湾西部绥中地区进行了风廓线测量试验。根据研究区域海岸线走向采用风向的十六分位法定义局地海风和陆风,分析和提取海陆风特征验证了多普勒测风激光雷达在春季季风间断期间观测海陆风的可行性,并计算和分析了大气边界层湍流能量的变化以及回流水平变化等特性。结果表明：1）绥中地区春季存在明显的海陆风环流特征,测风激光雷达观测海陆风出现的时间与地面自动气象站观测的数据较为一致,符合海陆风日的定义。2）海陆风日发生时,水平局地回流指数（RF）较小,1.2 km以下的RF值小于0.5,使得污染物循环累积,较易形成雾霾天气;但是海风时大气边界层的高度可达1 km以上,有利于低层大气污染物向高层扩散,减轻低层大气污染。研究结果为该地边界层参数化方案的设计和污染的防治提供了参考依据。  相似文献   

6.
The vertical distribution of single scattering albedos （SSAs） of Asian dust mixed with pollutants was derived using the multi-wavelength Raman lidar observation system at Gwangju （35.10°N,126.53°E）.Vertical profiles of both backscatter and extinction coefficients for dust and non-dust aerosols were extracted from a mixed Asian dust plume using the depolarization ratio from lidar observations.Vertical profiles of backscatter and extinction coefficients of non-dust particles were input into an inversion algorithm to retrieve the SSAs of non-dust aerosols.Atmospheric aerosol layers at different heights had different light-absorbing characteristics.The SSAs of non-dust particles at each height varied with aerosol type,which was either urban/industrial pollutants from China transported over long distances at high altitude,or regional/local pollutants from the Korean peninsula.Taking advantage of independent profiles of SSAs of non-dust particles,vertical profiles of SSAs of Asian dust mixed with pollutants were estimated for the first time,with a new approach suggested in this study using an empirical determination of the SSA of pure dust.The SSAs of the Asian dust-pollutants mixture within the planetary boundary layer （PBL） were in the range 0.88-0.91,while the values above the PBL were in the range 0.76-0.87,with a very low mean value of 0.76 ± 0.05.The total mixed dust plume SSAs in each aerosol layer were integrated over height for comparison with results from the Aerosol Robotics Network （AERONET） measurements.Values of SSA retrieved from lidar observations of 0.92 ± 0.01 were in good agreement with the results from AERONET measurements.  相似文献   

7.
2013年1月持续性霾天气中影响污染程度的气象条件分析   总被引：6，自引：3，他引：3  
利用南京本站气象观测记录、环保局监测数据以及NCEP/NCAR再分析资料,分析2013年1月持续性污染天气过程的大气环流背景,并结合南京地区探空资料、风廓线雷达资料以及激光雷达资料,分析这次持续性污染过程中空气质量属良好、轻度污染、中度污染、重度污染典型个例的大气垂直特征和边界层内气象条件的差异。得到如下结论:2013年1月份北方冷空气活动较弱,南京地区大气层结稳定,近地层风速小,污染物气象扩散条件差。加之近地层以弱偏东风为主,水汽较多,有利于污染物颗粒直径增大。大气垂直结构以及边界层内水平风速均对大气污染程度起到一定影响。AQI与逆温层高度存在显著负相关关系;大气污染时,1000 m以下出现逆温结构,且逆温层越低、越厚,污染程度越大;重度污染时,近地层出现贴地逆温层,厚度为700m左右。逆温层高度下降,PM10颗粒物高浓度区高度也明显下降,近地层污染物浓度对垂直方向上污染物浓度正响应的高度降低。在空气质量良好时, 150~1500m存在风速大值区,且风无空,湍流作用明显,有利于污染物和周围的洁净空气相混合而得到稀释,加速污染物的垂直扩散进程。当中度污染日和典型重度污染日时,150~1500 m之间并不存在大风速区。此外, PM10的300μg·m-3高浓度垂直高度延伸至300 m附近时,近地层PM2.5明显上升至100μg·m-3以上,高浓度区数值越大,近地层PM2.5越大。  相似文献   

8.
    
A new Lagrangian—Eulerian coupling model system is developed to study regional air quality. The system consists of mesoscale dynamical meteorological model (MM), Monte—Carlo model (MCM), parameterized model on planetary boundary layer (PBL) turbulent statistics, dry and wet removal model, and Eulerian nonlinear chemical model (ENCM). The physical, chemical and biological processes on air pollutants are considered comprehensively. 3—D distribution laws tor acidic gaseous pollutants (SO2 and NOx) emitted by Thai Mae Moh Power Plant and the secondary pollutants are studied in detail. The results simulated by the coupling model system are in good agreement with observational concentration data. The authors wish to express their thanks to Prof. Zeng Q. C. for his support to this research and to Dr. Han Z. W. and Zhang M. G. for their help in programming and numerical calculation of IAP, Chinese Academy of Sciences. Thanks are also due to NSTD and EGAT in Thailand for supporting this research.  相似文献   

9.
Observed pollutants are of both primary and secondary origins, influenced by local topography and meteorology. Identifying sources and relative contribution often require vast detailed data collection and complicated models. This study applied a statistical time series analysis to two selected pollution events, spring and fall, at two sites in northern Taiwan. Vector moving average representations were used to quantitatively examine relationships among chemical pollutants and estimate their lifetimes. Results from impulse responses show that wind direction change alters the characteristic of pollution observed in opposite sites of Taipei City, from chemical dominant system to transport dominant one and vice versa. Chemicals are clearly separated into photochemical pollutants and primary pollutants. Results pointed out that Taipei City is the major source of photochemical smog, but not these primary pollutants. Derived chemical lifetimes at same location vary from 20% to four times under different meteorological condition. Estimated concentrations of hydroxyl radical range between 2 to 8 × 107 cm−3. Photochemical pollutants are responsible for parts of PM10 collected in both station observed. Oxidation of SO2 is only important in PM10 observed at one station. This study provides a simpler tool to derive information usually from complex models, therefore, is suitable as complement in decision-making process.  相似文献   

10.
A network of remote and in-situ sensors was deployed in a Paris suburb in order to evaluate the mesoscale evolution of the daily cycle of CO2 and related tracers in the atmospheric boundary layer (ABL) and its relation to ABL dynamics and nearby natural and anthropogenic sources and sinks. A 2-μm heterodyne Doppler differential absorption lidar, which combines measurements of, (1) structure of the atmosphere, (2) radial velocity, and (3) CO2 differential absorption was a particularly unique element of the observational array. We analyse the differences in the diurnal cycle of CO, CO2, lidar reflectivity (a proxy for aerosol content) and H2O using the lidar, airborne measurements in the free troposphere and ground-based measurements made at two sites located few kilometres apart. We demonstrate that vertical mixing dominates the early morning drawdown of CO and aerosol content trapped in the former nocturnal layer but not the H2O and CO2 mixing ratio variations. Surface fluxes, vertical mixing and advection all contribute to the ABL CO2 mixing ratio decrease during the morning transition, with the relative importance depending on the rate and timing of ABL rise. We also show evidence that when the ABL is stable, small-scale (0.1-km vertical and 1-km horizontal) gradients of CO2 and CO are large. The results illustrate the complexity of inferring surface fluxes of CO2 from atmospheric budgets in the stable boundary layer.  相似文献   

11.
The airborne lidar LEANDRE was deployed from Kiruna (Sweden) in January1995, during Phase III of the Second European Stratospheric Arctic andMid-latitude Experiment (SESAME). Polar Stratospheric Clouds (PSC) weredetected on several flights. Four lidar retrievals, on two different days, arepresented together with the thermal history of air masses, derived from 5-daybackward trajectories calculated from the TOPCAT model, using ECMWF analyses.The first PSC case was observed at the synoptic scale and at a temperatureclose to the ice frost point, with no significant depolarization, suggestingthat particles were in the liquid phase, probably liquid ternaryH2SO4/HNO3/H2Osolution forming a Type 1b cloud. Locally, on the same day, a Type II PSC (icecloud) was detected above the Scandinavian Mountains and was related tomesoscale processes. On another day, the third lidar retrieval only showedbackground aerosols signature, whereas the last one was performed at the NATequilibrium temperature and its measured depolarization ratio was consistentwith few solid state Type Ia particles, probably composed of NAT. From thethermal histories, the different behaviour of the two Type I clouds isexplained in terms of cooling rates and compositional hysteresis, driven bytemperature.  相似文献   

12.
1.IntroductionLidarisincreasinglyusedinmeasuringtheopticalpropertiesofaerosolsandcloudssincethe1960's.Ithasbeenshownthatthedeterminationoftheextinctioncoefficientasafunctionofheightisfeasible(Klett,1980;Fernald,1984;LuDarenetal.,1977;Spinhirneetal.,...  相似文献   

13.
A key question of the backward integration algorithm to lidar equation is how to determine the far-end boundary value. This paper develops a Constraint Inversion Algorithm (CIA) for deriving the value and then the aerosol extinction profile from lidar signals, which uses the ground-level horizontal lidar signals as the constraint information. The smaller the wavelength is, the more sensitive to the variation of aerosol ex-tinction to backscatter ratio solved by CIA. According to the property an algorithm is further proposed to simultaneously retrieve the aerosol extinction profile, the size distribution and the imaginary part of its re-flective index from the multi-wavelength lidar observations. CIA is tested in the inversion simulations with satisfactory result.  相似文献   

14.
Described is a system for analyzing and forecasting the air quality in the central regions of Russia, During the operation of the system, the detailed meteorological information provided by the WRF-ARW model is used by the CHIMERE chemistry transport model for simulating the processes of transport, chemical transformation, and deposition of atmospheric minor constituents. Considered is the quality of retrieved and forecasted (with the lead time up to three days) concentrations of O3, NO2, NO, CO, and PM10. The presented verification scores of pollutant concentrations demonstrate a relative success of the system. Demonstrated is a need in improving the data on the emissions of the air pollutants used for simulations. A procedure for the statistical correction of computed concentrations is described and verification scores of its results are given.  相似文献   

15.
地面观测提供空间点的浓度信息,三维化学模式提供网格面的浓度信息,两者在进行对比验证或同化融合时会因为空间尺度不匹配引入误差,即观测代表性误差。本研究将大气污染地面国控监测站与区县监测站结合起来,获得了京津冀地区高密度地面观测数据,利用该数据首次对京津冀地区6项常规大气污染物（PM2.5、PM10、SO2、NO2、CO和O3）的地面观测代表性误差进行了客观估计,并与Elbern et al.（2007）方法估计的代表性误差进行了对比。结果发现:两种方法对京津冀地区NO2地面观测代表性误差估计非常接近,但Elbern et al.（2007）方法显著低估了SO2、CO和O3地面观测的代表性误差。在此基础上,我们对Elbern et al.（2007）方法及其误差特征参数进行了本地化修正,并增加了PM2.5和PM10的代表性误差特征参数,建立了京津冀大气污染地面观测代表性误差的客观估计方法。  相似文献   

16.
利用北京地区2017年11月至2018年1月连续3个月的激光雷达资料和无线电探空数据,按照清洁天、污染天和多云天3种天气条件,对大气边界层高度的计算方法和结果进行对比分析。结果表明,基于激光雷达消光系数的梯度法、标准差法和小波法都能够较好地提取边界层高度。清洁天标准差法计算的边界层高度高于梯度法和小波法,08:00（当地时间,下同）和20:00由无线电探空得到的清洁天边界层高度平均值分别为1176 m和1224 m。污染天标准差法的计算结果要低于梯度法和小波法,污染天无线电探空得到的边界层高度平均值约为956 m,和清洁天相比降低了两百多米,重污染时最低降低至562 m,逆温层高度和PM2.5浓度具有明显的反相关关系。有云时,梯度法和小波法确定的边界层高度和云高非常接近,标准差法计算的结果略低。总体而言,气溶胶激光雷达计算的边界层高度随着污染等级的提高没有明显的降低趋势,相反在重度污染情况下反而有所增加,这可能是由于污染物的不断堆积导致的。梯度法确定的边界层高度易受到污染物传输过程的影响,略高于逆温层高度。另外,激光雷达确定的边界层高度受到残留层影响时,也会高于逆温层。  相似文献   

17.
A technique of retrieving temperature gradient in the atmospheric boundary layer from measurements of signal to noise ratio derived from a CO2pulsed Doppler infrared lidar is proposed.  相似文献   

18.
北京秋季一次典型大气污染过程多站点分析   总被引：3，自引：1，他引：2  
多站点多种大气污染物的同步在线观测对深入剖析大气污染的成因和演变机制有重要意义。以龙潭湖、北京325 m塔、双清路和阳坊4监测站点实时NOx、SO2、O3、PM2.5和PM10浓度观测数据为基础,介绍了北京地区2010年10月3～11日发生的一次典型污染过程。不同污染物在污染过程中变化特征不一致,表现为NOx、SO2、O3浓度有明显日变化,而PM浓度升高后一直维持在高值,日变化幅度很小。通过分析不同站点、相同污染物之间的相关性和变异系数发现,4站点间一次污染物NO和SO2空间浓度差别大,变异系数分别为77%和70%,相关系数低于0.44;而二次污染物NO2、PM2.5、O3空间浓度差别较小,变异系数分别为34%、36%和29%,相关系数均超过0.54。结合中尺度气象模式研究发现,该污染过程中,850 hPa高空持续的西南暖平流造成华北地区显著平流逆温,与近地层辐射逆温共同作用,使北京地区混合层高度维持在1200 m以下。低混合层高度和低风速限制了大气垂直和水平扩散,造成北京地区近地层污染物累积,形成重度污染。  相似文献   

19.
We examine the influence of a modern multi-megawatt wind turbine on wind and turbulence profiles three rotor diameters ( $D$ D ) downwind of the turbine. Light detection and ranging (lidar) wind-profile observations were collected during summer 2011 in an operating wind farm in central Iowa at 20-m vertical intervals from 40 to 220 m above the surface. After a calibration period during which two lidars were operated next to each other, one lidar was located approximately $2D$ 2 D directly south of a wind turbine; the other lidar was moved approximately $3D$ 3 D north of the same wind turbine. Data from the two lidars during southerly flow conditions enabled the simultaneous capture of inflow and wake conditions. The inflow wind and turbulence profiles exhibit strong variability with atmospheric stability: daytime profiles are well-mixed with little shear and strong turbulence, while nighttime profiles exhibit minimal turbulence and considerable shear across the rotor disk region and above. Consistent with the observations available from other studies and with wind-tunnel and large-eddy simulation studies, measurable reductions in wake wind-speeds occur at heights spanning the wind turbine rotor (43–117 m), and turbulent quantities increase in the wake. In generalizing these results as a function of inflow wind speed, we find the wind-speed deficit in the wake is largest at hub height or just above, and the maximum deficit occurs when wind speeds are below the rated speed for the turbine. Similarly, the maximum enhancement of turbulence kinetic energy and turbulence intensity occurs at hub height, although observations at the top of the rotor disk do not allow assessment of turbulence in that region. The wind shear below turbine hub height (quantified here with the power-law coefficient) is found to be a useful parameter to identify whether a downwind lidar observes turbine wake or free-flow conditions. These field observations provide data for validating turbine-wake models and wind-tunnel observations, and for guiding assessments of the impacts of wakes on surface turbulent fluxes or surface temperatures downwind of turbines.  相似文献   

20.
Cirrus clouds related to transported dust layers were identified on 22 occasions with ground-based polarization lidar from December 2012 to February 2018 over Wuhan (30.5°N, 114.4°E), China. All the events occurred in spring and winter. Cirrus clouds were mostly located above 7.6 km on top of the aloft dust layers. In-cloud relative humidity with respect to ice (RHi) derived from water vapor Raman lidar as well as from ERA5 reanalysis data were used as criteria to determine the possible ice nucleation regimes. Corresponding to the two typical cases shown, the observed events can be classified into two categories: (1) category A (3 cases), in-cloud peak RHi ≥ 150%, indicating competition between heterogeneous nucleation and homogeneous nucleation; and (2) category B (19 cases), in-cloud peak RHi < 150%, revealing that only heterogeneous nucleation was involved. Heterogeneous nucleation generally took place during instances of cirrus cloud formation in the upper troposphere when advected dust particles were present. Although accompanying cloud-top temperatures ranged from –51.9°C to –30.4°C, dust-related heterogeneous nucleation contributed to primary ice nucleation in cirrus clouds by providing ice nucleating particle concentrations on the order of 10?3 L?1 to 102 L?1. Heterogeneous nucleation and subsequent crystal growth reduced the ambient RHi to be less than 150% by consuming water vapor and thus completely inhibited homogeneous nucleation.  相似文献   

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