Observation-based Estimation of Aerosol-induced Reduction of Planetary Boundary Layer Height

Radiative aerosols are known to influence the surface energy budget and hence the evolution of the planetary boundary layer. In this study, we develop a method to estimate the aerosol-induced reduction in the planetary boundary layer height （PBLH） based on two years of ground-based measurements at a site, the Station for Observing Regional Processes of the Earth System （SORPES）, at Nanjing University, China, and radiosonde data from the meteorological station of Nanjing. The observations show that increased aerosol loads lead to a mean decrease of 67.1 W m-2 for downward shortwave radiation （DSR） and a mean increase of 19.2 W m-2 for downward longwave radiation （DLR）, as well as a mean decrease of 9.6 W m-2 for the surface sensible heat flux （SHF） in the daytime. The relative variations of DSR, DLR and SHF are shown as a function of the increment of column mass concentration of particulate matter （PM2.5）. High aerosol loading can significantly increase the atmospheric stability in the planetary boundary layer during both daytime and nighttime. Based on the statistical relationship between SHF and PM2.5 column mass concentrations, the SHF under clean atmospheric conditions （same as the background days） is derived. In this case, the derived SHF, together with observed SHF, are then used to estimate changes in the PBLH related to aerosols. Our results suggest that the PBLH decreases more rapidly with increasing aerosol loading at high aerosol loading. When the daytime mean column mass concentration of PM2.5 reaches 200 mg m-2, the decrease in the PBLH at 1600 LST （local standard time） is about 450 m.

Numerical Study of Boundary Layer Structure and Rainfall after Landfall of Typhoon Fitow(2013): Sensitivity to Planetary Boundary Layer Parameterization

The boundary layer structure and related heavy rainfall of Typhoon Fitow(2013), which made landfall in Zhejiang Province, China, are studied using the Advanced Research version of the Weather Research and Forecasting model, with a focus on the sensitivity of the simulation to the planetary boundary layer parameterization. Two groups of experiments—one with the same surface layer scheme and including the Yonsei University(YSU), Mellor–Yamada–Nakanishi–Niino Level 2.5,and Bougeault and Lacarrere schemes; and the other with different surface layer schemes and including the Mellor–Yamada–Janjic′ and Quasi-Normal Scale Elimination schemes—are investigated. For the convenience of comparative analysis, the simulation with the YSU scheme is chosen as the control run because this scheme successfully reproduces the track, intensity and rainfall as a whole. The maximum deviations in the peak tangential and peak radial winds may account for 11% and 33%of those produced in the control run, respectively. Further diagnosis indicates that the vertical diffusivity is much larger in the first group, resulting in weaker vertical shear of the tangential and radial winds in the boundary layer and a deeper inflow layer therein. The precipitation discrepancies are related to the simulated track deflection and the differences in the simulated low-level convergent flow among all tests. Furthermore, the first group more efficiently transfers moisture and energy and produces a stronger ascending motion than the second, contributing to a deeper moist layer, stronger convection and greater precipitation.

VARIATION CHARACTERISTICS OF THE PLANETARY BOUNDARY LAYER HEIGHT AND ITS RELATIONSHIP WITH PM2.5 CONCENTRATION OVER CHINA

The planetary boundary layer height(PBLH) was calculated using the radiosonde sounding data, including120 L-band operational sites and 8 GPS sites in China. The diurnal and seasonal variations of PBLH were analyzed using radiosonde sounding(OBS-PBLH) and ERA data(ERA-PBLH). Based on comparison and error analyses, we discussed the main error sources in these data. The frequency distributions of PBLH variations under different regimes(the convective boundary layer, the neutral residual layer, and the stable boundary layer) can be well fitted by a Gamma distribution and the shape parameter k and scale parameter s values were obtained for different regions of China. The variation characteristics of PBLH were found in summer under these three regimes for different regions. The relationships between PBLH and PM_(2.5) concentration generally follow a power law under very low or no precipitation conditions in the region of Beijing, Tianjin and Hebei in summer. The results usually deviated from this power distribution only under strong precipitation or high relative humidity conditions because of the effects of hygroscopic growth of aerosols or wet deposition. The OBS-PBLH provided a reasonable spatial distribution relative to ERA-PBLH.This indicates that OBS-PBLH has the potential for identifying the variation of PM_(2.5) concentration.

Validation and Spatiotemporal Distribution of GEOS-5-Based Planetary Boundary Layer Height and Relative Humidity in China

Few studies have specifically focused on the validation and spatiotemporal distribution of planetary boundary layer height （PBLH） and relative humidity （RH） data in China. In this analysis, continuous PBLH and surface-level RH data simulated from GEOS-5 between 2004 and 2012, were validated against ground-based observations. Overall, the simulated RH was consistent with the statistical data from meteorological stations, with a correlation coefficient of 0.78 and a slope of 0.9. However, the simulated PBLH was underestimated compared to LIDAR data by a factor of approximately two, which was primarily because of poor simulation in late summer and early autumn. We further examined the spatiotemporal distribution characteristics of two factors in four regions--North China, South China, Northwest China, and the Tibetan Plateau. The results showed that the annual PBLH trends in all regions were fairly moderate but sensitive to solar radiation and precipitation, which explains why the PBLH values were ranked in order from largest to smallest as follows： Tibetan Plateau, Northwest China, North China, and South China. Strong seasonal variation of the PBLH exhibited high values in summer and low values in winter, which was also consistent with the turbulent vertical exchange. Not surprisingly, the highest RH in South China and the lowest RH in desert areas of Northwest China （less than 30%）. Seasonally, South China exhibited little variation, whereas Northwest China exhibited its highest humidity in winter and lowest humidity in spring, the maximum values in the other regions were obtained from July to September.

The Uncertainty of Tropical Cyclone Intensity and Structure Based on Different Parameterization Schemes of Planetary Boundary Layer

Based on different parameterization schemes of planetary boundary layer (PBL), the uncertainty of intensity and structure of the Super-strong Typhoon Rammasun (1409) is investigated using the WRF model (v3.4) with six PBL parameterization schemes. Results indicate that PBL uncertainty leads to the uncertainty in tropical cyclone (TC)prediction, which increases with forecast time. The uncertainty in TC prediction is mainly reflected in the uncertainty in TC intensity, with significant differences in the TC intensity forecasts using various PBL schemes. The uncertainty in TC prediction is also reflected in the uncertainty in TC structures. Greater intensity is accompanied by smaller vortex width,tighter vortex structure, stronger wind in the near-surface layer and middle and lower troposphere, stronger inflow(outflow) wind at the lower (upper) levels, stronger vertical upward wind, smaller thickness of the eye wall, smaller outward extension of the eye wall, and warmer warm core at the upper levels of eye. PBL height, surface upward heat flux and water vapor flux are important factors that cause the uncertainty in TC intensity and structure. The more surface upward heat flux and water vapor flux and the lower PBL height, the faster TC development and the stronger TC intensity.

Diurnal variability of the planetary boundary layer height estimated from radiosonde data

Diurnal variations in the planetary boundary layer height(PBLH)at different latitudes over different surface characteristics are described,based on 45 years(1973−2017)of radiosonde observations.The PBLH is determined from the radiosonde data by the bulk Richardson number(BRN)method and verified by the parcel method and the potential temperature gradient method.In general,the BRN method is able to represent the height of the convective boundary layer(BL)and neutral residual layer cases but has relatively large uncertainty in the stable BL cases.The diurnal cycle of the PBLH over land is quite different from the cycle over ocean,as are their seasonal variations.For stations over land,the PBLH shows an apparent diurnal cycle,with a distinct maximum around 15:00 LT,and seasonal variation,with higher values in summer.Compared with the PBLH over land,over oceans the PBLH diurnal cycles are quite mild,the PBLHs are much lower,and the seasonal changes are less pronounced.The seasonal variations in the median PBLH diurnal cycle are positively correlated with the near-surface temperature and negatively correlated with the near-surface relative humidity.Finally,although at most latitudes the daytime PBLH exhibits,over these 45 years,a statistically significant increasing trend at most hours between 12:00 LT and 18:00 LT over both land and ocean,there is no significant trend over either land or ocean in the nighttime PBLH for almost all the studied latitudes.

Comparisons in the global planetary boundary layer height obtained from COSMIC radio occultation,radiosonde,and reanalysis data

The global planetary boundary layer height(PBLH)estimated from 11 years(2007–17)of Integrated Global Radiosonde Archive(IGRA)data,Constellation Observing System for Meteorology,Ionosphere and Climate(COSMIC)soundings,and European Center for Medium-Range Weather Forecasts(ECMWF)interim reanalysis(ERAInterim)data,are compared in this study.In general,the spatial distribution of global PBLH derived from ERAInterim is consistent with the one from IGRA,both at 1200 UTC and 0000 UTC.High PBLH occurs at noon local time,because of strong radiation energy and convective activity.There are larger differences between the results of COSMIC and the other two datasets.PBLHs derived from COSMIC are much higher than those from radiosonde and reanalysis data.However,PBLHs derived from the three datasets all exhibit higher values in the low latitudes and lower ones in the high latitudes.The latitudinal difference between IGRA and COSMIC ranges from−1700 m to−500 m,while it ranges from−500 m to 250 m for IGRA and ERA-Interim.It is found that the differences among the three datasets are larger in winter and smaller in summer for most studied latitudes.

Effects of Turbulent Dispersion of Atmospheric Balance Motions of Planetary Boundary Layer

New Reynolds' mean momentum equations including both turbulent viscosity and dispersion are used to analyze atmospheric balance motions of the planetary boundary layer. It is pointed out that turbulent dispersion with r 0 will increase depth of Ekman layer, reduce wind velocity in Ekman layer and produce a more satisfactory Ekman spiral lines fit the observed wind hodograph. The wind profile in the surface layer including tur-bulent dispersion is still logarithmic but the von Karman constant k is replaced by k1 = 1 -2/k, the wind increasesa little more rapidly with height.

The Wind Structure in Planetary Boundary Layer

The investigations on the dynamies of the PBL have been developed in recent years. Some authors emphasized macro-dynamics and others emphasized micro-structure of the PBL. In this paper, we study and review some main characteristics of the wind field in the PBL from the view point connecting the macro-dynamics and micro-stucture of the PBL, thus providing the physical basis for the further research of the dynamics and the parameterization of the PBL.

Development of a Tropospheric Lidar for Observations of the Planetary Boundary Layer above Medellin, Colombia

In the Universidad Nacional de Colombia, Sede Medellin, the Lasers and Spectroscopy Group （GLEO） has been designed and manufactured a tropospheric lidar station based on a pulsed Nd：YAG laser operating at 532-nm wavelength. The main scientific objective has been to evaluate the vertical structure of the Planetary Boundary Layer （PBL） in urban sites of Medellin-Colombia, South America, （Longitude 75°34′05″ West, Latitude 6°13′55″ North）, using suspended aerosols as tracers of the atmospheric motion. This paper reports the design, manufactures and performance of an elastic lidar system, which was operated under varying air pollution and meteorological conditions and the observations presented here were performed in early 2010, over the metropolitan area of Medellin, city included in the Andean region of Colombia.

中国省域环境可持续性时空格局及其影响因素

人类活动已成为人类世背景下全球环境变化的主要驱动力,因此将其合理调控在地球环境边界之内是实现可持续发展的前提条件。作为全球尺度的环境边界,行星边界秉持“地球系统观”,为统筹不同区域的环境可持续性评估提供了新视角。以行星边界为切入点,评估中国省域主要人类活动的环境可持续性状况,揭示其时空格局演变及社会经济影响因素。结果表明:(1)中国省域碳、氮、磷排放的不可持续性北部整体高于南部,分异程度随时间逐步拉大,不可持续省份数量的占比均已超出2/3;省域水、土地利用的可持续性南部整体高于北部,保持相对稳定,可持续省份数量的占比均已超出3/4。(2)中国省域环境可持续性大体受人口、经济、技术等因素的综合影响,且各类环境要素的可持续性之间存在一定的协同效应。其中,各类环境可持续性均受人口规模的正向驱动,同时氮、磷、水和土地的可持续性均受农业活动的负向驱动。(3)碳排放可持续性主要受能源消费强度的负向驱动,而磷排放可持续性同时受人口城镇化率的负向驱动,水可持续性受二产占比的负向驱动。基于行星边界的环境可持续性研究,可为区域合理界定和有效承担全球环境可持续性责任提供科学参考。

冷轧变形Pb-Ca-Sn-Al合金在回复和再结晶过程中的晶界特征分布

采用电子背散射衍射(EBSD)技术研究了冷轧变形Pb-0．1％Ca-1．5％Sn-0．026％Al合金在回复和再结晶过程中的晶界特征分布(GBCD)．结果表明:在回复过程中,合金内形成了比例接近50％的平直∑3晶界,这类晶界不处在由一般大角度晶界构成的晶界网络上,不能使合金的GBCD得到优化;相反,在再结晶过程中,除了生成比例超过50％的∑3晶界外, 还出现了较多的∑9和∑27等低∑重位点阵晶界(CSL),并且这些晶界和相当多的弯曲的∑3晶界均处在由一般大角度晶界构成的晶界网络上,可以使合金的GBCD得到优化．进一步的分析指出:回复过程中所形成的平直的∑3晶界是共格孪晶界, 它们能量很低,很难迁移;在再结晶过程中,除了生成不可迁移的共格的∑3孪晶界外,还可形成大量可迁移的弯曲的非共格∑3 晶界,这类晶界的迁移和彼此会合可形成∑9和∑27等∑3n(n为正的整数)晶界,这是合金GBCD得到优化的根源．

滇中新元古代澄江组层型剖面锆石U-Pb年代学及其地质意义

澄江组是华南新元古代地层中的重要地层单元之一,其确切沉积时限对于建立和完善华南新元古代区域地层格架具有关键意义。对滇中澄江组层型剖面顶部的凝灰岩夹层进行高精度SHRIMP锆石U-Pb定年研究,获得3组有效的206Pb/238U加权平均年龄值,其分别为(819±14)Ma(MSWD=0.15)、(781±11)Ma(MSWD=0.24)和(725±11)Ma(MSWD=0.65)。其中,最年轻的一组年龄值(725±11)Ma被解释为澄江组顶部凝灰岩夹层的形成时间,可以代表滇中澄江组的顶界年龄,从而进一步确认澄江组的沉积时限为800～725 Ma。结合相关研究资料,证实澄江组与开建桥组、莲沱组的沉积时限基本相当,三者与下冰期长安组不存在对比关系,而应与冰期前板溪群的上部进行对比。此外,推测两组年龄值较老的锆石可能是与新元古代罗迪尼亚(Rodinia)超大陆裂解有关的幕式岩浆活动的记录。

贵州盘县峨眉山玄武岩系顶部凝灰岩LA-ICP-MS锆石U-Pb年龄:对峨眉山大火成岩省与生物大规模灭绝关系的约束

在20世纪90年代,有学者认为峨眉山大火成岩省(Emeishan Large Igneous Province,ELIP)大规模火山活动与二叠-三叠系之交(Permian-Triassic Boundary,P-TB)的生物大灭绝事件在时间上有耦合关系,随后的40Ar/39Ar同位素测年结果也显示峨眉山大火成岩省是晚二叠世形成的。但是,近些年大量的SHRIMP U-Pb测年结果表明,ELIP大规模火山喷发约在～260Ma;因此有研究认为,ELIP火山活动与中二叠世瓜德卢普期末(end-Guadalupian)的生物灭绝事件在时间上联系更加紧密。至于P-T界线生物大灭绝,现在多数学者认为是,由于西伯利亚大火成岩省火山强烈活动释放大量气体和火山灰所造成环境变化引起的。最近,我们在ELIP东部的贵州盘县峨眉山玄武岩系剖面中发现顶部发育厚度达近百米的凝灰岩层,其LA-ICP-MSU-Pb法测年结果为251.0±1.0Ma,与浙江煤山剖面中二叠系-三叠系边界处黏土层或火山灰层的锆石U-Pb年龄接近。因此,峨眉山玄武岩喷发结束的时间应该在P-T边界,与西伯利亚大火成岩省的主体喷发时间一致。新的测年结果暗示了ELIP火山活动与地球历史上最大的一次生物灭绝事件(P-T边界)可能存在着成因联系。

固溶和预时效Pb合金冷轧退火后的晶界特征分布

采用电子背散射衍射(EBSD)技术研究了不同固溶及预时效状态下Pb-0．05Ca-1．5Sn-0．026Al(质量分数,％)合金冷轧退火后的晶界特征分布(GBCD)．结果表明,290℃固溶处理后冷轧退火的合金样品中出现了较多的特殊晶界,∑3和(∑9+∑27)晶界的比例分别达到49．6％和7．2％,并且特殊晶界能较好地阻断一般大角度晶界网络的连通性;固溶后先进行100及200℃预时效处理,然后再进行冷轧退火的合金样品中形成了较少的特殊晶界,∑3和(∑9+∑27)晶界的比例分别低于35．9％和2．5％,特殊晶界几乎不能阻断一般大角度晶界网络的连通性．

福建潘田铁矿床花岗岩岩石地球化学特征、锆石U-Pb年代学及其与成矿的关系

潘田铁矿床矿体主要赋存于潘田花岗岩体外接触带的"硅钙岩性界面"中,其成矿与花岗岩侵入关系密切,是一个具有很大找矿潜力的富铁矿床。但前人对该花岗岩的研究还很薄弱,本文对潘田铁矿花岗岩进行了岩石地球化学特征、锆石U-Pb定年研究,探讨其岩石成因、形成时代、构造环境、及其与成矿的关系。LA-ICP-MS锆石U-Pb定年获得其结晶年龄为131.68±0.48Ma。该岩体为高钾钙碱性系列,属弱过铝质-准铝质岩石;稀土元素总量较低,轻稀土相对于重稀土富集,具有明显铕负异常,重稀土配分模式相对平坦,中稀土相对亏损。微量元素中相对富集大离子亲石元素而亏损高场强元素。岩石地球化学特征表明潘田岩体为高分异I型花岗岩,形成于碰撞后拉张环境。潘田铁矿床矿体与花岗岩体的空间分布规律与成因关系表明,花岗岩侵入作用是控制主成矿阶段矿体空间定位的地质作用,花岗岩是铁矿床的成矿地质体,林地组碎屑岩与黄龙组-栖霞组碳酸盐岩的接触界面是成矿有利部位,矿床类型属于典型"硅钙岩性界面"成矿,本矿床的成因类型属于"多因耦合、临界转换、边界成矿"的典型案例。

冀北滦平地区中生代火山岩地层锆石U-Pb测年及启示

在冀北—辽西地区,冀北的滦平地区是中生代地层最为齐全,也是唯一的晚中生代沉积作用基本连续的地区.许多研究者认为该地区的土城子组与张家口之间存在着J3—K1界线和中生代的构造转换界面.该地区分布的主要中生代地层自下而上依次为髫髻山组、土城子组、张家口组、大北沟组、大店子组和西瓜园组.通过LAICPMS方法的锆石UPb测年,获得了该地区中生代火山岩地层的年代格架,即髫髻山组的顶界年龄为(162.8±3.2)Ma,土城子组形成的主体年代范围是(142.6±1.3)～(136.4±1.9)Ma,张家口组形成的年代范围是(135.7±1.8)～(135.2±2.3)Ma,大店子组顶部安山岩的年龄是(131.4±3.7)～(130.2±3.0)Ma.锆石的稀土元素分析表明:土城子组中锆石的稀土元素特征与张家口组中锆石的特征一致,而与髫髻山组中的锆石有较大的区别.综合以上分析数据及野外地质特征可以得出以下结论:(1)该地区的土城子组与髫髻山组之间不仅时间间隔较长,而且二者中火山岩的源区也有较大的区别;土城子组与张家口组之间不仅时间上基本连续,而且二者中火山岩的源区也有明显的一致性.这就表明了滦平地区的土城子组与张家口组是同一地质背景下的产物,即该地区二者之间应不存在J3—K1界面和构造转换界面.(2)滦平地区大店子组顶部火山岩在年代上与辽西北票—义县地区的义县组底部、辽西凌源地区的张家口组顶部基本相当.

华北吕梁地区汉高山群和小两岭组的地层时代——火山岩锆石U-Pb年龄的约束

华北吕梁地区出露的以陆源碎屑沉积为主的汉高山群为中元古界底界界线层型的理想候选剖面,其时代的确定对认识华北前寒武纪地质演化历史及初始盖层的确定及Nuna超大陆聚散的研究具有重要的意义。目前,汉高山群的时代、划分对比及其意义还存在较大争议。本研究使用SHRIMP(二次离子质谱仪)对汉高山群安山岩中的锆石进行了U-Pb同位素分析,获得其^(207)Pb/^(206)Pb年龄加权平均值为1769±9 Ma(2σ)。这是首次直接测得汉高山群锆石U-Pb年龄。另测得同一层位的小两岭组3个不同部位火山岩中的锆石^(207)Pb/^(206)Pb年龄加权平均值分别为1792±18 Ma、1773±19 Ma和1778±20 Ma,与汉高山群的年龄在误差范围内一致,故认为汉高山群和小两岭组的时代分别为1769±9 Ma和1792~1773 Ma。结合前人的研究资料,认为汉高山群和小两岭组的形成时代为1780 Ma左右。吕梁地区汉高山群的剖面地层连续,发育区域上分布较为稳定的安山岩,是华北克拉通中南部极好的区域等时标志层。该时期的裂谷沉积和火山岩在扬子陆块西部、劳伦大陆西北部、澳大利亚北部、南美巴西圣弗兰西斯科(São Francisco)克拉通、非洲刚果克拉通及西伯利亚克拉通均有产出,且可以对比,显示同时期由Nuna超大陆初始裂解引起的陆内裂谷沉积地层的全球分布特征,由此提出国际中元古界底界应该下移,并且汉高山剖面可作为国际上新的中元古界底界的候选层型剖面。

大巴山西段上奥陶统-下志留统五峰组-龙马溪组斑脱岩锆石U-Pb年龄及其地质意义

扬子板块北缘大巴山地区上奥陶统-下志留统地层中斑脱岩较发育。笔者对大巴山西段陕西紫阳麻柳和四川万源皮窝乡上奥陶统五峰组-下志留统龙马溪组剖面的斑脱岩进行采样,开展了高精度锆石U-Pb测年,首次在该地区获得了445.1±3.5Ma和446.1±7.2Ma的锆石U-Pb年龄,限定了五峰组-龙马溪组地层沉积年龄,为扬子板块北缘大巴山地区奥陶系-志留系界线附近火山喷发事件、地层年代学研究提供了依据。本文所获得的年龄数据与秦岭-大别山造山带奥陶纪岩浆弧形成时间同步,略晚于华北克拉通西南缘奥陶系斑脱岩(449.0~465.8Ma),其火山活动可能与古秦岭洋壳向北的俯冲有关,火山凝灰质可能源自沿古秦岭洋盆北缘的火山弧喷发。中奥陶世晚期至早志留世早期,多幕次的高频火山喷发事件影响了当时海洋化学条件、碳循环波动、气候变冷和生物辐射脉动,造成了晚奥陶世末期的冰川启动和生物集群绝灭。

Pb在GH871合金晶界的偏聚

利用PERKIN ELMERPHI 5 95型俄歇谱仪研究了新型含铌铁基高温合金GH871的晶界上各元素的含量。结果表明 :Pb含量在 5× 10 -6时其晶界偏聚比达到 12 0 0～ 170 0左右 ,当Pb含量在 2× 10 -6时其晶界偏聚比减少到 5 0 0。另外合金中的Ce、P、S、B。