VERTICAL DISTRIBUTION CHARACTERISTICS OF ATMOSPHERIC AEROSOLS IN LIAONING^*          下载免费PDF全文

YANG Jun  ZHOU Deping  GONG Fujiu  GAO Jianchun  LI Zihua 《Acta Meteorologica Sinica》2000,14(3):373-382

16 aircraft missions were conducted for the measurement of atmospheric aerosols in separate days of late spring and early summer of 1996 and 1997.The paper deals with detailed analysis of the variation in vertical/horizontal distributions of the concentration of the particles and their size distribution at 0-5 km above ground,and with the relations to temperature and relative humidity documented in general.Evidence suggests that the concentrations show different distribution features in vertical above and below the cap of the mixed layer:the particle size distribution is subject to a range of forming mechanisms,displaying a multi-modal pattern:the horizontal concentration experiences remarkable variation:temperature and relative humidity stratifications have conspicuous influence on the concentration and size distribution of aerosols.  相似文献   

Trace element distributions in aquatic sediments of Danang – Hoian area, Vietnam     

H. T. T. Thuy  H. J. Tobschall  P. V. An 《Environmental Geology》2000,39(7):733-740

 Distribution of the trace elements Cr, Cu, Ni, Pb and Zn in surficial sediments of the river/sea environment in Danang – Hoian area (Vietnam) was investigated to examine the degree of metal pollution caused by anthropogenic activities. Point sources from domestic and industrial wastes are identified as dominant contributors of trace element accumulation. Surficial sediments of Hoian River show extremely high total concentrations of Cu (Average Concentration 295 μg/g), Ni (AC 112 μg/g), Pb (AC 396 μg/g) and Zn (AC 429 μg/g) that exceed assigned safety levels ER-M. Similarly, the sediments of Han River show high Pb (AC 188 μg/g) and Zn (AC 282 μg/g) contents. In marine sediments of Thanhbinh beach Pb is also enriched (138 μg/g) above guideline levels. In contrast the sediments of the Cude River are dominated by trace element concentrations close to background values. Received: 17 December 1998 · Accepted: 6 May 1999  相似文献   

Environmental impact assessment on water quality deterioration caused by the decreased Ganges outflow and saline water intrusion in south-western Bangladesh   总被引：3，自引：0，他引：3  

Md. Mokhlesur Rahman  Muhammad Qumrul Hassan  Mohammad Saiful Islam  S. Z. K. M. Shamsad 《Environmental Geology》2000,40(1-2):31-40

 This paper deals with an environmental impact assessment of low water flow in the river Ganges during a dry period at the Khulna and Mongla port areas in south-western Bangladesh. Large-scale surface water withdrawal in India after commissioning the Farakka Barrage causes a drastic fall in the Ganges low-flow condition within the Bangladesh territory during every dry period. The average lowest discharge in the Ganges is 552 m³/s, which is about 73% less than that in the pre-Farakka time. This has caused the deterioration of both surface and groundwater quality of the study area. Salinity is the principal cause of water quality degradation in the area. Present observation shows that the surface water of the area is sulphate-chloride dominated, which signifies high salinity whereas the groundwater is categorized as of medium to high salinity. To maintain the Rupsa River's maximum salinity below 1000 μS/cm the discharge in the Ganges should be ∼1500 m³/s, whereas that at Garai basin is ∼10 m³/s. If this present situation continues it will be a crippling blow to the environment of the area in the long term. An integrated multidisciplinary approach to hydrogeological research is urgently required to salvage the area from further deterioration. Received: 9 August 1999 · Accepted: 8 March 2000  相似文献   

基于近地层垂直速度能谱尺度特征确定复杂下垫面零平面位移     

宋薇  彭珍  邹钧  孙鉴泞 《气象科学》2024,44(1):157-165

本文利用位于南京市郊区的南京大学仙林校区SORPES观测站多层湍流观测数据分析了湍流谱特征,以白天不稳定条件下垂直速度能谱谱峰对应的长度尺度也就是离地高度为判据,探讨了运用该方法确定复杂下垫面零平面位移的可行性。统计分析表明,该方法确定的长度尺度呈现出较为一致的概率分布形状,概率最大的长度尺度对应于离地高度,在复杂下垫面情况下这个高度就是零平面位移高度到观测高度之间的距离,将观测点的离地高度减去这个距离就能得到零平面位移。本文同时运用不稳定条件下垂直速度方差在近地层中的相似关系来确定零平面位移,并与谱方法得到的结果进行对比。结果表明,谱方法和方差法得到的零平面位移非常接近。  相似文献   

沙纹弹道成因理论评析   总被引：7，自引：5，他引：2  

孙显科  张凯  张大治  吕亚军  喻利华 《中国沙漠》2003,23(4):471-475

运用风沙地貌蚀积原理对长期风靡于风沙地貌学研究领域的R·A·拜格诺跃移质冲击起动学说进行了评析,在肯定该学说正确方面和历史贡献的同时,对其中的沙纹弹道成因理论提出了异议。在分析弹道理论特点后认为,跃移质等量、等高、等距的三等特性是拜氏冲击起动学说在沙纹成因上的具体运用和观点的集中体现。分析认为沙粒跃移特性轨迹只存在于少量的跃移质中,且很少具有连续性;它不能取代普遍存在于风沙移动之中沙粒的3种运动形式,也无法体现沙粒两种起动的相互关系和沙粒在移动中所表现出来的高低不一,移距长短不同的差异性和分选性。评析强调沙粒起动和沙粒运移的多样性,在寻求它们的规律时,不应简化其多样性,或追求运动的单一性和特殊性。实验证明,沙纹无论在初始的形成阶段,还是在后续的演进阶段,均有风力起动和冲击起动的参与,而不是跃移质单一冲击的结果。沙纹有规则的排列主要是贴地夹沙气流周期性脉动的反映,而不是跃移质特性轨迹的重演。  相似文献   

城市化影响地下水水质的正负效应   总被引：3，自引：0，他引：3  

于开宁万力  都沁军 《地球科学》2003,28(3):333-336

以石家庄市为例, 通过城市化水平和地下水污染态势的定量计算、分析, 对城市化影响地下水水质的机理及其正负效应进行了探讨.结果表明: 石家庄城市化发展处于初级阶段; 城市化影响地下水水质有正负两方面的效应, 城市化水平的提高, 有助于改善地下水水质, 但却易于加剧地下水盐污染.本研究为以地下水作为主要、甚至唯一供水水源城市的可持续发展提供了一种理论和根本途径.   相似文献   

正交直墙前直立圆柱的波浪绕射的解析研究     

宁德志  滕斌  宋向群 《海洋科学进展》2004,22(1):29-35

应用镜像原理,将正交直墙前单个圆柱的波浪绕射问题,转化为4个对称布置圆柱的4向入射波浪的绕射问题。然后应用速度势的特征展开方法和Graf加法定理,建立了正交直墙前垂直圆柱的波浪绕射解析解。通过数值计算研究了圆柱与正交直墙间距离大小、波浪入射角等因素与圆柱上总波浪作用力的解析关系。  相似文献   

试论伏牛山南坡土壤垂直分异规律——兼论亚热带北界的划分   总被引：12，自引：1，他引：11  

马建华 《地理学报》2004,59(6):998-1011

在野外土壤调查和室内土壤理化分析的基础上,开展了伏牛山南坡土壤组成和性质垂直分异、土壤类型划分以及亚热带北界问题的讨论。研究表明：(1) 调查断面上土壤表层HA/FA随高度增加而增大,且均小于1,海拔900 m左右土壤胡敏酸的芳构化程度最低;随高度增加土壤pH和盐基饱和度先下降后上升;海拔900 m以下的土壤中均有明显的黏化层,向上土壤黏粒淋溶淀积逐渐减弱;海拔900 m以下的土壤土体风化程度高,大部分氧化物的平均迁移系数和土体淋溶率小于1,土体Saf小于5.06,淀积层游离铁含量大于20 g·kg-1,铁游离度大于40%,具有弱富铁铝作用,剖面中出现明显的铁锰新生体,而向上土体风化程度减弱,不发生富铁铝作用,剖面中不出现铁锰新生体。(2) 伏牛山南坡海拔550 m以下出现黏磐黄褐土 (饱和黏磐湿润淋溶土),550~950 m出现普通黄棕壤 (普通铁质湿润淋溶土),950~1900 m出现棕壤 (普通简育湿润淋溶土或暗沃简育湿润雏形土),1900 m以上出现暗棕壤性土或草甸暗棕壤 (暗沃冷凉湿润雏形土)。(3) 伏牛山南坡亚热带北界约在海拔950 m。  相似文献   

西太平洋副热带高压对热带 海温异常响应的研究   总被引：34，自引：5，他引：29  

应明  孙淑清 《大气科学》2000,24(2):193-206

利用多年的观测资料,研究了西太平洋副热带高压对热带海温异常的响应及其相互作用过程。着重研究冬、夏季西太平洋副高对同期及前期不同海域（特别是赤道东、西太平洋以及印度洋海域）海温异常的响应;用SVD方法分析了夏季副热带高压与前冬、前春及同期各月全球海温的最佳耦合模态。在对比研究西太平洋副热带高压异常时其垂直环流变化的基础上,进而研究海气相互作用对副热带高压影响的物理过程。  相似文献   

Observations of vertical ground accelerations exceeding gravity during the 1997 Umbria-Marche (central Italy) earthquakes     

M. Bouchon  S. Gaffet  C. Cornou  M. Dietrich  J.P. Glot  F. Courboulex  A. Caserta  G. Cultrera  F. Marra  R. Guiguet 《Journal of Seismology》2000,4(4):517-523

We found extensive evidence that the vertical ground accelerations produced during the largest shock (M = 6.0) of the 1997 Umbria-Marche earthquake sequence exceeded 1g in two areas close to the heavily-damaged villages of Annifo and Colle Croce. This evidence comes from the striking observation of thousands of freshly fractured and broken rocks and stones in these areas. Some of the broken stones lie isolated on soft detritic soil while others had been previously piled up, probably a long time agoto clear the fields for farming. The freshness of the cuts and fractures and the consistency of the observations for thousands of rocks and stones in these areas indicate that these rocks were thrown upwards during the earthquake, with breakage occurring at the time of impact. Ground motion calculations consistent with the static deformation inferred from GPS and interferometry data, show that the broken stones and rocks are found in the zone where the strongest shaking took place during the earthquake and that most of the shaking there was vertical.  相似文献