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Based on the hydrochemical characteristics of water bodies in the northwestern part of the southern Aral Sea region, limnic ecosystems are shown to be liable to anthropogenic changes. The dynamics of the salinity, ionic composition, oxygen content of water, and nutrients under human impact on water bodies of the southern Aral Sea region are shown. 相似文献
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Hans J.A Neu 《Marine pollution bulletin》1982,13(2):44-47
The first part of this article (Mar. Pollut. Bull., 13, 7–12, 1982) described the impact of the seasonal fresh water runoff on bodies of water—such as the Gulf of St. Lawrence and the coastal region—through changes in the salinity and temperature distribution and through changes in the current generated by the density difference between the fresh river water and the ocean. The strength of the current and thus the transport of deep ocean water to the coastal region depends on the amount of fresh water released into the ocean. Therefore modifying the natural seasonal runoff by storing water for power production during the winter interferes with the timing of the physical and dynamic balance of the coastal region. The impact of this interference on the marine life and on the climate of the region is now discussed. 相似文献
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Assimilation experiments are performed with the Weather Research and Forecasting (WRF) models’ three-dimensional variational
data assimilation (3D-Var) scheme to evaluate the impact of directly assimilating the Advanced Television and Infrared Observation
Satellite Operational Vertical Sounder (ATOVS) radiance, including AMSU-A, AMSU-B and HIRS, on the analysis and forecasts
of a mesoscale model over the Indian region. The present study is, to our knowledge, the first where the impact of ATOVS radiance
has been evaluated on the analysis and forecasts of a mesoscale model over the Indian region. The control (without ATOVS radiance)
as well as experimental (which assimilated ATOVS radiance) run were made for 48 h starting at 0000 UTC during the entire July
2008. The impacts of assimilating the radiances from different instruments (e.g., AMSU-A, AMSU-B and HIRS) were measured in
comparison to the control run. The assimilation experiments for July 2008 (30 cases) demonstrated a positive impact of the
assimilated ATOVS radiance on both the analysis state as well as subsequent short-range forecasts. Relative to the control
run, the moisture analysis was improved with the assimilation of AMSU-B and HIRS radiance, while AMSU-A was mainly responsible
for improved temperature analysis. The comparison of the model-predicted temperature, moisture and wind with NCEP analysis
indicated that a positive forecast impact is achieved from each of the three instruments. HIRS and AMSU-A radiance yielded
only a slight positive forecast impact, while AMSU-B radiance had the largest positive forecast impact for moisture, temperature
and wind. The comparison of model-predicted rainfall with observed rainfall indicates that ATOVS radiance, particularly AMSU-B
and HIRS, impacted the rainfall positively. This study clearly shows that the improved analysis of mid-tropospheric moisture,
due to the assimilation of AMSU-B radiances, is a key factor to improve the short-term forecast skill of a mesoscale model. 相似文献
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S. Rajamani D. R. Talwalkar P. U. Upasani D. R. Sikka 《Pure and Applied Geophysics》1982,120(3):422-436
The monsoon sub-programme of FGGE deployed a variety of observing systems such as research aircraft, research vessels, floating ballooms, and a geostationary satellite, etc. during the special observational period of Monex-79, with a view to making the best possible data set available for studies on various aspects of the monsoon circulation. Whether the data obtained from the various observational platorms improve the representation of the monsson systems, flow patterns, etc. in the analysis is the basis of this study. For this, the objective analyses of the wind field were made with different data sets, first using only the data from conventional observation platforms, subsequently including the data from aircraft and ships and then finally including the data from the satellite. These analyses were compared with carefully made subjective analyses.It is inferred that the addition of data has a positive impact on the objective analysis and the improvement in the analysis is more marked in the data-void region like the Arabian Sea compared to the region where observational stations are distributed fairly stisfactorily. It is also inferred that the impact of the aircraft/ship data on the analysis is more consistent than the data from the satellite. 相似文献
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北京及邻区中等地震前的近南北向异常小震条带 总被引：1，自引：0，他引：1
北京是我国政治、经济和文化中心,中等有感地震会引起极大的社会影响。北京地区面积小、地震较少,缺少有效的中等地震短期预测指标。通过对1970年以来首都圈中部地区的小震活动图像全时空扫描与研究,认为该地区的近南北向异常小震条带可以作为北京及邻近地区中等地震前短期预测指标。 相似文献
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A sediment quality triad (SQT) assessment was made of the impact of copper mine tailings disposal on littoral meiofaunal assemblages in the Atacama region of northern Chile. This situation is unusual in that the disposal is direct into the high-energy coastal system and not via a river estuary or other low-energy environment. This situation also allows for the examination of the impact of copper mine tailings in the absence of confounding effects from other pollutants. The three components of the SQT were: 1. an analysis of the bioavailable metals in both the sedimentary porewater and the adjacent seawater, 2. a microcosm bioassay of both sediments and seawaters using meiofaunal assemblages, and 3. quantitative field samples of the meiofaunal assemblages. Twelve study sites with varying degrees of impact were used, including three reference sites. The study identified that both the meiofaunal assemblage densities and taxa diversities decrease with increasing levels of bioavailable copper, that the Foraminifera and Harpacticoida are sensitive to copper, and that otoplanid Turbellaria are often characteristic of impacted sites; tailings also have both chemical and physical impacts on the environment. In some cases the physical impact of tailings is more important in excluding some organisms e.g. the interstitial polychaete, Saccocirrus sonomacus, from a site than is their chemical impact. 相似文献
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在分析沁水盆地北部煤层气富集与地下水和地质构造之间的关系基础上,采用大地电磁法探测地下水分布以及有利和不利煤层气富集影响因素、间接探测煤层气相对富集区;根据煤层气富集地质模型设计了地球物理模型,利用有限单元法开展典型薄层模型正演模拟,讨论了探测方法的可行性;选择山西沁水盆地北部煤层气勘探区开展可控源音频大地电磁探测技术试验,结合已有地质、钻井及测井资料完成了试验资料的处理与解释;试验结果表明,利用可控源音频大地电磁法能有效获得地层电性结构,推断含水、富水区,结合煤层气有利富集地质条件和影响因素,可以实现间接预测煤层气的有利富集区. 相似文献
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Cui Tong Yang Tao Xu Chong-Yu Shao Quanxi Wang Xiaoyan Li Zhenya 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(6):1849-1866
The source region of Yellow river is an alpine river sensitive to climate changes, but the potential effects of climate change on hydrological regime characteristics and ecological implications are less understood. This study aims to assess the response of the alterations in the flow regimes over the source region of Yellow river to climate change using Soil and Water Integrated Model driven by different Global Circulation Models (GFDL-ESM2M, IPSL-CM5A-LR and MIROC-ESM-CHEM) under three Representative Concentration Pathway emission scenarios (RCP2.6, RCP4.5 and RCP8.5). Indicators of hydrological alteration and River impact index are employed to evaluate streamflow regime alterations at multiple temporal scales. Results show that the magnitude of monthly and annual streamflow except May, the magnitude and duration of the annual extreme, and the number of reversals are projected to increase in the near future period (2020–2049) and far future period (2070–2099) compared to the baseline period (1971–2000). The timing of annual maximum flows is expected to shift backwards. The source region of Yellow river is expected to undergo low change degree as per the scenarios RCP2.6 for both two future periods and under the scenarios RCP4.5 for the near future period, whereas high change degree under RCP4.5 and RCP8.5 in the far period on the daily scale. On the monthly scale, climate changes mainly have effects on river flow magnitude and timing. The basin would suffer an incipient impact alteration in the far period under RCP4.5 and RCP8.5, while low impact in other scenarios. These changes in flow regimes could have several positive impacts on aquatic ecosystems in the near period but more detrimental effects in the far period.
相似文献12.
Lg波的QLg值是描述区域地壳结构及介质衰减特性的重要参数之一,QLg层析成像被广泛应用于地壳衰减结构横向不均匀性的研究中.但是,对QLg在垂直方向上的不均匀性的研究较少.当发现一个地区发生QLg值低时,我们希望进一步了解这种介质衰减深度.本文通过数值模拟合成地震图的方法,通过分析不同震源深度和介质模型计算QLg,判断Lg波发生主要衰减的深度.研究结果显示：（1）当震源深度浅时,上地壳介质衰减对于Lg波Q值的影响明显比下地壳的影响更大.而震源深度深时,两者贡献基本相当;（2）如果上地壳介质衰减强,则随着震源深度的增加,η值逐渐减小;如果下地壳介质衰减强,η值先增大后减小;但如果下地壳存在低速层,则η值持续增大;（3）如果上地壳介质衰减强,则随着震源深度的增加,Q0逐渐增大;反之如果下地壳介质衰减强,则Q0逐渐减小.因此,我们可以通过调查某一区域不同深度地震的Lg波衰减规律,来判断这一地区的地壳介质衰减情况. 相似文献
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识别显著影响重点监视区地震检测能力的“敏感台站”, 对有针对性地开展地震台网运行维护和加强相关区域天然地震与非天然地震的监视跟踪工作有重要意义。 利用基于概率的最小完整性震级(PMC)方法, 通过对研究区地震台站进行“检测能力评分”(Dscore)和“缺失评分”(Missing Score)方式进行识别研究, 以龙门山断裂南段强震危险区为例的重点监视区“敏感台站”识别结果表明, 研究区内51个台站的“检测能力评分”及“缺失评分”, 可识别对重点监视区地震检测能力影响最大的台站, 给出台站停止运行引起的最小完整性震级的变化, 并探讨了多台站停止运行等造成影响的极限情况。 上述“敏感台站”的识别方式, 可为地震台网运行维护、 针对特定目标区的地震监视跟踪和进一步的台网优化改造提供参考。 相似文献
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Reproductive seasonality of the fish fauna and limnoecology of semi-arid Brazilian reservoirs 总被引：1，自引：1，他引：0
Sathyabama Chellappa Regina M.X. Bueno Thiago Chellappa Naithirithi T. Chellappa Vera Maria Fonseca Almeida e Val 《Limnologica》2009,39(4):325-329
The native fish fauna commonly found in the drainage basins of rivers and reservoirs of Latin America, including those of the semi-arid Northeastern Brazil, are representatives of the Neotropical region. This work reports on the reproductive ecology of five commercially important and consumable native fish species, in relation to rainfall and hydrological variables of the semi-arid reservoirs in Brazil. Pluviometric precipitation, temperature, pH, dissolved oxygen and electrical conductivity of the water were registered, and maturation of fish gonads was assessed on a monthly basis. This region is characterized with short spells of rain interspersed with long dry season and rainfall seems to be the main environmental factor which modulates the timing of the spawning period of fish. Construction of reservoirs without adequate facilities for fish migration has an adverse impact on the migratory fish species which are of commercial and ecological importance to semi-arid Northeastern Brazil. 相似文献
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M. Zarei 《Ground water》2016,54(3):354-362
Salt diapirs in southern Iran are typically in contact with karstic and alluvial aquifers and consequently they are the most likely sources of groundwater salinization in this arid region. However, there are some salt diapirs that have no significant degradation effect on adjacent aquifers. Assessments of 62 of 122 Iranian‐emerged salt diapirs based on geological, geomorphological, hydrogeological, and hydrochemical investigations indicated that 45% of the studied salt diapirs did not have a negative impact on surrounding water resources, whereas 55% of the salt diapirs have degraded water quality of adjacent aquifers. The impacts ranged from low‐ to high‐grade salinization. We characterize here four major factors that control the impact of salt diapirs on surrounding water resources: (1) the evolutionary stage of the diapir, (2) the geological and (3) hydrogeological setting of the diapir, and (4) human activities. Identification of the major factors governing the influence of salt diapirs on the adjacent aquifers is necessary to understand the mechanism of salt diapir impact on adjacent aquifers, and subsequently to decide how to mitigate the deteriorating effect of the diapirs on the surrounding water resources. 相似文献
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S. P. Smyshlyaev A. I. Pogoreltsev V. Ya. Galin E. A. Drobashevskaya 《Geomagnetism and Aeronomy》2016,56(1):95-109
The planetary wave impact on the polar vortex stability, polar stratosphere temperature, and content of ozone and other gases was simulated with the global chemical–climatic model of the lower and middle atmosphere. It was found that the planetary waves propagating from the troposphere into the stratosphere differently affect the gas content of the Arctic and Antarctic stratosphere. In the Arctic region, the degree of wave activity critically affects the polar vortex formation, the appearance of polar stratospheric clouds, the halogen activation on their surface, and ozone anomaly formation. Ozone anomalies in the Arctic region as a rule are not formed at high wave activity and can be registered at low activity. In the Antarctic Regions, wave activity affects the stability of polar vortex and the depth of ozone holes, which are formed at almost any wave activity, and the minimal ozone values depend on the strong or weak wave activity that is registered in specific years. 相似文献
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Zizhen Jin Qiudong Zhao Xiang Qin Jingtian Zhang Hui Zhang Jia Qin Yu Qin Hongyuan Li Jizu Chen Yushuo Liu Yanzhao Li Lihui Wang 《水文研究》2021,35(10):e14392
Quantifying the impact of landscape on hydrological variables is essential for the sustainable development of water resources. Understanding how landscape changes influence hydrological variables will greatly enhance the understanding of hydrological processes. Important vegetation parameters are considered in this study by using remote sensing data and VIC-CAS model to analyse the impact of landscape changes on hydrology in upper reaches of the Shule River Basin (URSLB). The results show there are differences in the runoff generation of landscape both in space and time. With increasing altitude, the runoff yields increased, with approximately 79.9% of the total runoff generated in the high mountains (4200–5900 m), and mainly consumed in the mid-low mountain region. Glacier landscape produced the largest runoff yields (24.9% of the total runoff), followed by low-coverage grassland (LG; 22.5%), alpine cold desert (AL; 19.6%), mid-coverage grassland (MG; 15.6%), bare land (12.5%), high-coverage grassland (HG; 4.5%) and shrubbery (0.4%). The relative capacity of runoff generation by landscapes, from high to low, was the glaciers, AL, LG, HG, MG, shrubbery and bare land. Furthermore, changes in landscapes cause hydrological variables changes, including evapotranspiration, runoff and baseflow. The study revealed that HG, MG, and bare land have a positive impact on evapotranspiration and a negative impact on runoff and baseflow, whereas AL and LG have a positive impact on runoff and baseflow and a negative impact on evapotranspiration. In contrast, glaciers have a positive impact on runoff. After the simulation in four vegetation scenarios, we concluded that the runoff regulation ability of grassland is greater than that of bare land. The grassland landscape is essential since it reduced the flood peak and conserved the soil and water. 相似文献
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V. V. Safargaleev N. F. Blagoveshchenskaya L. J. Baddeley V. F. Grigor’ev T. D. Borisova 《Geomagnetism and Aeronomy》2018,58(5):663-672
We have analyzed the artificial pulsations detected in several cases in the hertz range in terms of the eastern electrojet dynamics. The pulsations were detected in 30% cases of pulse HF wave impact on the ionosphere during an experiment on modulated ionosphere heating at the Space Plasma Exploration by Active Radar (SPEAR) facility (Spitsbergen Archipelago) in November 2013. The pulsations occur when the polar edge of the eastern electrojet approaches the assumed region of influence on the ionosphere due to the northward drift of the electrojet or its extension with increased intensity. The pulsations vanish when the electrojet moves away from the influenced region, drifting southward. The beginning of pulsations is delayed by several minutes with respect to the starting of the HF transmitter. The pulsations are observed only in one of the horizontal components of the geomagnetic field at a distance of 50 km from the SPEAR facility, and they vanished at a distance of about 1300 km. 相似文献
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The Blue Ridge Province contains ubiquitous northeast-southwest-trending thrust faults or smaller thrust "slivers" that greatly impact the nature and character of ground water flow in this region. Detailed investigations at a field site in Floyd County, Virginia, indicate that high-permeability zones occur in the brittle crystalline rocks above these thrust faults. Surface and borehole geophysics, aquifer tests, and chlorofluorocarbon and geochemical data reveal that the shallow saprolite aquifer is separated from the deeper fault-zone aquifer by a low-fracture permeability bedrock confining unit, the hydraulic conductivity of which has been estimated to be six orders of magnitude less than the conductivity of the fault zones at the test site. Within the Blue Ridge Province, these fault zones can occur at depths of 300 m or more, can contain a significant amount of storage, and yield significant quantities of water to wells. Furthermore, it is expected that these faults may compartmentalize the deep aquifer system. Recharge to and discharge from the deep aquifer occurs by slow leakage through the confining unit or through localized breach zones that occur where quartz accumulated in high concentrations during metamorphism and later became extensively fractured during episodes of deformation. The results of this investigation stress the importance of thrust faults in this region and suggest that hydrogeologic models for the Blue Ridge Province include these ancient structural features. Faults in crystalline-rock environments may not only influence the hydrology, they may dominate the flow characteristics of a region. 相似文献