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1.
Dust storms in Northeast China become more se-rious in recent years due to the global warming and local land use and cover change (LUCC) around the sand lands in western and northwestern Jilin Province. Field investigations and urban testing re-vealed that the amount of dusts brought by dust storm reaches a higher level in the past two years. According to an experiment on the “mud-snow”in April, 2000 and an observation in March, 2002, the dusts coming from the western Jilin and fall… 相似文献
2.
There are two different dust storms in Northeast China, normal dust and alkali dust, from Kerqin sand land and Songnen saline land. As well as visible damages of the dust storms, there are some invisible influences. The authors provide evidences that the bacteria carried by dusts from remote area should not be ignored, but the damages of the alkali dusts are still not clear. 相似文献
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In this part, Levitus‘ climatological temperature and salinity are incorporated in the numerical model developed in Part I. Diagnostic and prognostic experiment on the thermohaline circulation were conducted. The smooth Levitus‘ data do not include any information on the South China Sea Warm Current (SCSWC), so it is not in the model-produced diagnostic thermohaline circulation. Although the SCSWC does not appear in the wind-driven circulation in the barotropic case, it appears in the prognostic wind-driven circulation in the baroclinic case. This implies that the differing circulation pat-terns between barotropic case and bareclinic case are due to the stratification. The prognostic thermohaline circulation with wind stress and inflow/outflow transports at open boundaries are also discussed. Coupling of density and dynamic forces makes the circulation pattern more complicated, Even though the stratification is not always a direct cause of the formation of the SCSWC, it is at least an indirect cause. 相似文献
4.
?????CORS??2?????????д?????????????????????????У???????CATS???????????????????CORS??????????????е??????????????з??????????????1??CORS??????????????в????а???????????????????2??CORS?????????????????N??E??U??????????????????????????￡????У?N??E????????????????WN+FN??U????????????????WN+FN+RWN;3???????CORS????????????????????????????????????????????????????????????????????????????????? 相似文献
5.
GNSS����ƽ̨���ݴ���Ŀɿ��Է��� 总被引：1，自引：0，他引：1
????????????????GNSS?????????????????????????????????????????????????????????????????????????????????GPS????GLONASS?????????????????????????Galileo???????????η?????????澫?????????????????????????????????????????????? 相似文献
6.
现代引潮位质疑与调和分析方法评论 总被引：5，自引：3，他引：2
郗钦文 《大地测量与地球动力学》2002,22(2):7-9
一些现代引潮位展开的潮波振幅中包含时间项，即振幅具有时间依赖性，它们不属于完全调和展开。由于潮波振幅的时间依赖性，振幅或发散或收敛，使得远离起始历元的潮波振幅变得毫无确定意义，不仅失去了坐标组合滤波的基础，而且使Venedikov调和分析方法的应用出现理论障碍，难以为用。按照平差变换理论，只有满秩变换，才能得到与原观测完全等价的平差结果。Venedikov调和分析方法中的数字滤波过程并非满秩变换，自然不能得到安全等价的平差结果，凡是预先采用数字滤波的调和分析方法，其结果会因滤波变换而异。 相似文献
7.
利用遗传算法反演山西地区非弹性衰减系数、场地响应和震源参数 总被引：1，自引：0，他引：1
利用山西台网的数字波形资料,基于遗传算法,用Atkinson方法得到山西地区介质的品质因子Q值随频率的关系为Q =420.7f0.369.采用Moya方法反演山西数字地震台网40个台站的场地响应均表现与频率有关,其中27个台站的场地响应在频率域不平坦,只有13个台站的场地响应基本没有放大.震源参数的计算结果表明,地震震级与地震距呈线性关系,但地震距与应力降以及应力降与震源半径之间的依赖关系不太明确. 相似文献
8.
张志强 《广东海洋大学学报》1994,(1)
粤西沿海与广西沿海一带有马氏珠母贝人工育苗场达数百家之多，但由于种种原因，多数育苗效果欠佳。本文就育苗期间经常出现的面盘幼虫发育参差不齐，壳顶初期前后幼虫大量下沉，附着初期幼虫难变态及附着后脱落等三个主要问题进行分析，并提出相应的对策。 相似文献
9.
????IGS??????????????????????Allan???????????????????????????????????????????????????????????????????????????????о????????????1??GPS???????????GLONASS???????????4??????????????????????????????1??1/2??1/3??1/4???2???????????????GPS????????Allan????????????仯????GLONASS????????Allan????????????????仯??????GPS????????д???????????GLONASS???????????????????????????????仯??????С??3????????ε?????????????????仯??? 相似文献
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11.
虽然华北地区属于克拉通类型的地质单元,然而在其地壳内部,尤其是东部地区的地壳内,低速层相当发育。这些低速层多位于上地壳底部15~25 km的深度范围内。同活动造山带内的低速层相比,华北地区的壳内低速层表现出明显不同的特点。壳内低速层水平延伸尺度不大,互相之间不太连接。同时,低速层内外速度差较小,大都小于5%。考虑到华北盆地岩石圈底部的热侵蚀作用和地壳的热状态,认为部分熔融是产生壳内低速层的一个重要因素。 相似文献
12.
Acidic species, such as Nitrate, in polar snow and firn layers are “reversibly” deposited, and are sufficiently volatile to undergo significant postdepositional exchange between snow/firn and the atmosphere. Through comparison of the snowpit and snowpack nitrate concentrations from central East Antarctica and the headwater of ürumqi River, we conclude that the nitrate peaks in the uppermost surface snow layers in central Antarctica are not related to an atmospheric signal and must account for post-depositional effects. Such effects, however, are not found in the surface snowpack nitrate profiles from the headwater of ürumqi River. Two reasons may account for the post-depositional difference. At first, nitrate in the polar snow and firn layers appears to be hydrated ion, which can be taken up by the atmosphere, while at the headwater of ürumqi River it seems mainly as mineral ion, which assembles the behavior of aerosol-derived species that are “irreversibly” deposited and do not undergo significant post-depositional exchange with the atmosphere. Secondly, the chemical features of the snow and ice on the Antarctica are mainly determined by wet deposition, to the contrary, dry deposition is more significant at the headwater of lUrumqi River than that on the East Antarctic Plateau. 相似文献
13.
严密推导了利用水准资料计算地壳垂直剖面内剪应变量的两套公式，并分别阐述了其不同的物理含义和地质含义。这两套公式分别表示垂直剖面内两组不同方向间的地壳表层的垂直剪应变，第一个模型表征地壳表层倾斜变化的程度，第二个模型表征地壳表层曲率变化的程度，二者从不同的侧面反映了地壳变化的状态。 相似文献
14.
外向型汉语学习词典是为母语非汉语的学习者编纂的学习汉语用的词典。20世纪80年代以来,词典编纂成果数量较多,品种较全,类型意识在逐渐增强,培育出了几部品牌产品;但在类型定位、用户意识、编纂技术、品牌观念等方面仍需加强。在研究方面,出现了一批较有分量的论文和专著,研究内容不断深入,研究队伍不断壮大;但与国外发达水平相比,仍有较大差距,主要表现在理论研究滞后于编纂实践、学科仍不成熟、学术流派尚未形成等。 相似文献
15.
While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance. 相似文献
16.
地壳形变与地震预测研究中的测量精度 总被引：2，自引：0，他引：2
对地壳形变与地震预测研究中普遍存在对测量成果精度要求过于苛刻的问题进行了分析,结果认为这可能导致以前很多有价值的信息未能得到充分的利用。追求高质量的观测数据是对的,但针对实际问题的性质和需求,首先应强调如何充分发挥历史资料的作用,因为历史资料可能精度不高,但更可能是无法取代的。因此要最大限度地挖掘原有数据中的有用信息,切不可因误差较大而放弃可能获取有用信息的机会。并以中国大陆1999—2009两期GPS垂直形变速率场及其分析和应用为例,用实例进一步阐释这一观点。 相似文献
17.
河南省自然地质条件复杂 ,生态环境脆弱 ,不仅分布有特殊不良地质环境条件和严重的地质灾害 ,而且存在由人类活动引起的诸多环境地质问题。特殊不良地质环境条件主要有特殊不良岩土体 (湿陷性黄土与胀缩土 )、原生地球化学异常 (高氟水、低碘水、咸水 )和次生地球化学异常(土壤盐渍化 ) ;地质灾害有崩塌、滑坡、泥石流、水土流失、地面塌陷、矿坑突水、瓦斯爆炸等 ;环境地质问题有水资源枯竭、水质污染、固体废弃物堆放等。这些已成为制约我省人民生活水平提高和社会经济发展的重要因素 相似文献
18.
对华北地区定点台站形变观测资料,采用傅立叶去年周期和线性拟合的方法进行处理.结果表明,华北地区现阶段的变化未形成主体异常时段,反映出断层未进入强烈活动阶段;首都圈地区跨断层资料异常数量不多,没有形成同步异常,异常变化幅值也不是很大,中短临地震异常不明显. 相似文献
19.
樊双虎 《地球科学与环境学报》1993,(Z1)
大地构造环境对玄武质岩浆成分有影响,但却不是主要的,更不是唯一的因素。源区物质成分、岩浆作用过程、地壳或岩石圈的混染及地球演化历史过程等是影响岩浆成分的主要因素。把玄武岩成分与大地构造环境紧密地联系在一起,并提出用玄武岩成分判别大地构造环境的作法,已经遇到了许多困难,这种方法用于变质玄武岩区问题更多。本文通过对目前常用的几种玄武岩成分-大地构造环境判别图的分析,认为如果不考虑其它因素,这类判别图对变质玄武岩几乎是不适用的。 相似文献
20.
栾锡武 《中国海洋湖沼学报》1998,(4)
INTRODUCTIONThevalueofthestartdepthDshouldbegivenfirstinthegraVityanoInalinversion.DisthecmstthicknesswherethecorresPondinggraVityanomaliszerooragivenknownvalue.TheburieddepthofthedensityinterfacecalculatedfrOmthegraVityanomalinver-siondependsonthestaItdePthD-Whnthegivenvalue0fthestartdepthissInall(large)lthewholeburieddepthofthecalculateddensityinteifaceissInall(larg),sointhegravityan0Inalyinversion,thedeterminati0nofthestartdepthDisveryimPortant.Usually,Disgivenbasedonseismic,ear… 相似文献