Variability of Near-Ground Ozone Concentrations During Cold Front Passages – a Possible Effect of Tropopause Folding Events     

H. Kunz  P. Speth 《Journal of Atmospheric Chemistry》1997,28(1-3):77-95

The analysis of surface ozone variability requires besides chemicalstudies the consideration of meteorological conditions and dynamicprocesses. Our research focuses on the mechanisms in connection with coldfront passages. A statistical study and case studies of cold front passageswere carried out at six German ground-based sites during the year 1990.After the passage of cold fronts three typical developments of thenear-ground ozone concentrations could be identified. Usually the ozoneconcentrations decrease due to advection of clean air masses or due toenhanced cloudiness preventing the photochemical production of ozone,chemical destruction by nitrogenoxides, and heterogeneous chemistry. In somecases the concentrations increased by reason of downward mixing of ozoneenriched air intruded from the stratosphere into the troposphere bytropopause foldings. For a few cases no modification set in. The decreasewas mostly twice as strong as the increase. The latter was between 4 and 8ppb on the average. Special emphasis is given to the transport ofstratospheric ozone down to the ground. There is no direct evidence forstratospheric ozone at ground level, because it cant be distinguished fromthe tropospheric one, but from case studies circumstantial evidence is foundin favour of it. As an example of increasing ozone behind the passage ofcold fronts one case study typical of all other case studies is presented.It shows the characteristic properties of the corresponding fronts, whichare fast movement, a vertical split structure and strong convection.  相似文献   

A two-layers model for the summer circulation of the East China Sea   总被引：1，自引：0，他引：1  

Liang Xiangsan  Su Jilan 《海洋学报(英文版)》1994,13(3):325-344

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场匹配处理法反演介质层系声参数     

林俊轩 《中国海洋大学学报(自然科学版)》1996,(4)

采用场匹配处理法反演层系介质参数，在匹配处理前先对层系模型参数进行预估。参数预估将大大地减少匹配运算时间。模拟实验的反演结果与取样实测结果相当符合  相似文献   

基岩海岸海水入侵特征及对策——以长岛县南北长山岛为例   总被引：6，自引：0，他引：6  

杜国云 《海洋科学》2002,26(5):55-59

山东省长岛县南、北长山岛地下海水入侵于20世纪70年代，至90年代有明显扩大。海水入侵存在海湾层状况沉积体孔隙式层状入侵、岩岸裂隙式脉状入侵和层状基岩层隙式面状入侵3种基本形式，造成海水入侵不断加剧的原因一方面受大气降水的明显影响，另一方面由于当地经济与社会发展带来的地下淡水过量开采引起，形成了地下水质恶化与城镇和人口稠密区、机井密集区相对应的社会-地质灾害空间组合。防止海水入侵、切实保护地下淡水资源，首先应采取重点地段上实施拦蓄结合的地下水工程，也可以借用天然形成的糜棱岩带作为拦蓄工程基础，以节约资金投入；其次是减少地表径流与地表蒸发，扩大地下淡水量；以及采取以减少地下水资源开发量为目标的开源节流等方面的措施。  相似文献   

海水入侵造成的山东沿海生态变化     

季明川  耿秀山 《海岸工程》1992,11(1):61-67

本文通过典型研究发现,近十几年来连续干旱和过量超采地下淡水,是导致山东沿岸海水向内陆地下入侵的主要原因。由此酿成了严重的生态灾害:水生态、农田生态、滨海盐土生态、城镇经济生态和生态工程环境严重恶化,造成海水入侵区水源破坏、农田减产或绝产及盐生天然植物生态群落向内陆扩展,干扰了工农业和工程规划布局以及社会文明和人民生活,提高了地方病发病率。  相似文献   

莱州湾南岸海水入侵发展动态和原因   总被引：2，自引：0，他引：2  

丰爱平  谷东起  夏东兴 《海岸工程》2006,25(3):7-13

以莱州市监测资料为基础,结合已有的研究结果,对莱州湾南岸海水入侵发展动态进行了研究.研究结果表明,1980-1989年是莱州湾南岸海水入侵发展最快的时期,其后海水入侵发展速度有所减缓,入侵南界基本在1995年线附近摆动.BP网络计算结果表明,莱州湾南岸海水入侵主要原因是降水量减少,直接原因则是地下水超采.降水量增加比地下水超采量减少所引起的海水入侵速度降低量要大;即使恢复了海水入侵前的水量供需状况,海水入侵也不会完全停止.  相似文献   

硇洲岛海水入侵数值模拟     

段梅 《地质灾害与环境保护》2016,(1):108-112

通过对硇洲岛地质和水文地质条件的综合分析,建立了本研究区三维地下水数值模型,并获取了相关含水层参数。从而建立海水入侵数值模型,对硇洲岛在不同开采条件下的海水入侵趋势进行了模拟预测,结果表明,减少开采量能减缓硇洲岛海水入侵;在满足当地供水需求的前提下,减少浅层水开采量,在远离沿海区域的中部地区适当增加中层水开采量的开采方案优于现状开采条件下的方案。本研究也为减缓海水入侵提供了相关科学依据。  相似文献   

塔里木板块东北缘坡七侵入体金属硫化物矿物学特征及成矿指示作用     

芮会超 《地质与勘探》2016,52(6):1107-1115

坡七侵入体位于新疆塔里木板块东北缘,是坡北岩体第三期次岩浆作用的产物。该侵入体主要的岩石类型有二辉橄榄岩、橄榄辉石岩、方辉辉石岩、橄长岩、苏长岩、辉长岩以及辉长闪长岩。橄榄岩相和苏长岩相中赋存铜镍硫化物矿(化)体,矿石构造类型有浸染状、稠密浸染状和块状。金属硫化物主要为磁黄铁矿、镍黄铁矿、黄铜矿和黄铁矿,金属矿物生成顺序为:铬尖晶石-(第1世代镍黄铁矿Pn~1、第1世代黄铜矿Ccp~1)-NC型磁黄铁矿-(第2世代镍黄铁矿Pn~2、4C型磁黄铁矿、第2世代黄铜矿Ccp~2、第1世代黄铁矿Py~1)-第3世代镍黄铁矿Pn~3-(第2世代黄铁矿Py~2、第3世代黄铜矿Ccp~3)。其中,磁黄铁矿、镍黄铁矿矿物学特征表明,岩(矿)体侵位过程中,高温阶段温度下降缓慢,低温阶段温度下降较快,晚期有热液作用叠加。成矿期可以划分为岩浆成矿期(岩浆熔离阶段和单硫化物固溶体分异阶段)及热液成矿期。依据矿石结构构造、金属矿物矿物学特征综合分析,坡七侵入体深部硫化物熔离充分,成矿潜力大。  相似文献   

Comparison of Methods for Determining Specific-surface Area of Fine-grained Soils     

D. N. Arnepalli  S. Shanthakumar  B. Hanumantha Rao  D. N. Singh 《Geotechnical and Geological Engineering》2008,26(2):121-132

Characteristics of fine-grained soils primarily depend on their specific-surface area and hence, reliable determination of this parameter is essential. In this context, researchers have employed quite sophisticated instruments (viz., a BET surface area analyzer, the mercury intrusion porosimetry, internal reflectance spectroscopy, X-Ray diffraction and gas pycnometer etc.) and methodologies (viz., sorption of Methylene Blue dye, Ethylene Glycol Monoethyl Ether and p-Nitrophenol) to determine specific-surface area of these soils. However, most of these methodologies are found to be quite tedious, cost and time intensive. Apart from this, the results obtained are contentious due to the inherent limitations associated with either the instruments employed or the basic assumptions made for computing the specific-surface area of the soil. Hence, it becomes mandatory to evaluate the efficiency of these methodologies for determining specific-surface area of fine-grained soils. With this in view, different types of soils were considered in this study and their specific-surface area was determined, by following different methodologies, and the results were evaluated critically. In addition, attempts were made to develop relationships between the basic properties of fine-grained soils (viz., liquid limit, cation-exchange capacity, activity, and free swell index) and the specific-surface area. These relationships will be of immense help to the practicing engineers and research fraternity.  相似文献   

海岸带咸淡水界面位置确定方法的介绍   总被引：1，自引：1，他引：0  

周训 《现代地质》2008,22(1):123-128

Ghyben-Herzberg公式依赖潜水位确定海岸带咸淡水界面位置,被广泛应用但存在误差。Hubbert公式严格描述突变界面问题的水头和界面位置之间的关系,但在实际中难以应用。通过考察咸淡水界面之下咸水带任意点的压力平衡关系和咸水带及淡水带任意点的水头描述得知,当地下水流处于稳定状态且满足Dupuit假设时,可以根据同一垂直线上界面之下咸水带任意点(含界面)的咸水测压水头和界面之上淡水带任意点(自潜水面至界面)的淡水测压水头确定滨海均质各向同性潜水含水层咸淡水界面的位置。Ghyben-Herzberg公式是这一方法的特例,描述界面位置的Hubbert公式也是该方法的一个特例。这一方法需要两个相邻的分别揭露淡水带和咸水带的测压孔。  相似文献