Assessing covariate-dependent contaminant time-series in the marine environment     

Fryer  R. J.; Nicholson  M. D. 《ICES Journal of Marine Science》2002,59(1):1-14

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南海台风中期路径趋势判别预报方法     

胡基福  黄立文  洪光 《中国海洋大学学报(自然科学版)》1996,(3)

根据历史台风的相似路径将台风分为西行、西北沿海登陆和海上转向三类，并分析了各类500hPa高度场的特征。通过对台风位移与其相应的500hPa高度场的典型相关分析，提取了天气强迫信息，连同台风的一些气候学和持续性特征作为待选因子，采用多级逐步判别方法，建立台风72h路径趋势的各类判别函数。预报时，代入72h500hPa数值预报产品及气候持续性因子。通过对1990～1994年的独立台风进行了试报检验。结果表明，试报的准确率为88.8％，Heidke技巧得分为0．80。该方法为南海台风中期路径趋势预报提供了一种客观方法。  相似文献   

Successful colonization of the calanoid copepod Acartia tonsa in the oligo-mesohaline area of the Gironde estuary (SW France) – Natural or anthropogenic forcing?     

Valrie David  Benoît Sautour  Pierre Chardy 《Estuarine, Coastal and Shelf Science》2007,71(3-4):429-442

The copepod Acartia tonsa appeared in Europe in the first half of the 20th century and colonized progressively European seas and estuaries, possibly transferred from North Atlantic Coast of America. It had been reported in the polyhaline area of the Gironde estuary for a long time but was first recorded in the oligo-mesohaline area in 1983. Its abundance has been increasing significantly. High abundances of A. tonsa were reported since 1999, supplanting the abundances of its autochthonous congeneric species, Acartia bifilosa. This colonization was characterized by analyzing the mean seasonal variability: (1) for three 5-year periods corresponding to three different steps of A. tonsa appearance (1978–1982, A. tonsa was absent; 1988–1992, low abundances of the species; and 1999–2003, high abundances of A. tonsa) in the oligo-mesohaline area and (2) for three stations distributed along the salinity gradient during the recent period. The aim of this work was to define if this colonization was due to natural or anthropogenic forcing and to evaluate its possible impact on autochthonous zooplanktonic community.Both natural and anthropogenic forcings seem to explain the colonization of Acartia tonsa in the oligo-mesohaline area of the Gironde estuary. First records (1983–1988) could be due to marine water inputs caused by high values of the North Atlantic Oscillation index. The global warming which caused the increase of the summer warm period, the marinisation of the system and the local decrease of the turbidity should have been the key factors favoring the establishment of the species. Anthropogenic forcings as the establishment of the nuclear power plant which locally causes warmer conditions are also important factors explaining the differences of seasonal cycle observed between oligo-mesohaline area and other stations: the seasonal pattern of A. tonsa in the oligo-mesohaline area was indeed characterized by an autumnal peak of abundances which has been observed in other stations and in many North European estuaries, and by a second spring peak that had only been observed in Southern estuaries.The introduction of Acartia tonsa in the Gironde estuary significantly changed the seasonal pattern of autochthonous copepods, by limiting their seasonal abundances without affecting their long-term population stability. Finally, the successful colonization of A. tonsa had led to the spread of the seasonal zooplanktonic production which could have had an impact on fish and shrimp productions.  相似文献   

Geographical and temporal variation in levels of organochlorine contaminants in marine mammals   总被引：1，自引：0，他引：1  

Aguilar A  Borrell A  Reijnders PJ 《Marine environmental research》2002,53(5):425-452

The interpretation of the spatial and temporal patterns of variation in organochlorine concentrations in marine mammal populations is complex because of the lack of wide-scale, long-term surveys. Therefore the results from several surveys must be combined and this causes undesired heterogeneity due to differences in the sampling and analytical techniques used and in the biological characteristics of the individuals sampled. Moreover, information is not homogeneously distributed in either space or in time. Most research is concentrated in western Europe, northern America and certain areas of Asia, while it is extremely limited or non-existent in Africa and most regions of the southern hemisphere. Marine mammals from the temperate fringe of the northern hemisphere, particularly fish-eating species which inhabit the mid-latitudes of Europe and North America, show the greatest organochlorine loads; noteworthy are the extremely high levels found in the Mediterranean Sea and certain locations on the western coasts of the United States. Concentrations in the tropical and equatorial fringe of the northern hemisphere and throughout the southern hemisphere are low or extremely low. The polar regions of both hemispheres showed the lowest concentrations of DDTs and PCBs, although levels of HCHs, chlordanes and HCB were moderate to high in the cold waters of the North Pacific. During recent decades, concentrations have tended to decrease in the regions where pollution was initially high but they have increased in regions located far from the pollution source as a consequence of atmospheric transport and redistribution. It is expected that the Arctic and, to a lesser extent, the Antarctic, will become major sinks for organochlorines in the future; this process may already be significant for some compounds such as HCB and HCHs. Effort should be devoted to both assessment of organochlorine trends in the now highly polluted populations of the temperate fringe of the northern hemisphere and to the implementation of long-term monitoring of marine mammal populations inhabiting polar regions.  相似文献   

Hydrologic metrics for status‐and‐trends monitoring in urban and urbanizing watersheds          下载免费PDF全文

Derek B. Booth  Christopher P. Konrad 《水文研究》2017,31(25):4507-4519

Local governmental agencies are increasingly undertaking potentially costly “status‐and‐trends” monitoring to evaluate the effectiveness of stormwater control measures and land‐use planning strategies or to satisfy regulatory requirements. Little guidance is presently available for such efforts, and so we have explored the application, interpretation, and temporal limitations of well‐established hydrologic metrics of runoff changes from urbanization, making use of an unusually long‐duration, high‐quality data set from the Pacific Northwest (USA) with direct applicability to urban and urbanizing watersheds. Three metrics previously identified for their utility in identifying hydrologic conditions with biological importance that respond to watershed urbanization—T_Qmean (the fraction of time that flows exceed the mean annual discharge), the Richards‐Baker Index (characterizing flashiness relative to the mean discharge), and the annual tally of wet‐season day‐to‐day flow reversals (the total number of days that reverse the prior days' increasing or decreasing trend)—are all successful in stratifying watersheds across a range of urbanization, as measured by total contributing area of urban development. All metrics respond with statistical significance to multidecadal trends in urbanization, but none detect trends in watershed‐scale urbanization over the course of a single decade. This suggests a minimum period over which dependable trends in hydrologic alteration (or improvement) can be detected with confidence. The metrics also prove less well suited to urbanizing watersheds in a semi‐arid climate, with only flow reversals showing a response consistent with prior findings from more humid regions. We also explore the use of stage as a surrogate for discharge in calculating these metrics, recognizing potentially significant agency cost savings in data collection with minimal loss of information. This approach is feasible but cannot be implemented under current data‐reporting practices, requiring measurement of water‐depth values and preservation of the full precision of the original recorded data. With these caveats, however, hydrologic metrics based on stage should prove as or more useful, at least in the context of status‐and‐trends monitoring, as those based on subsequent calculations of discharge.  相似文献   

Long‐term records of dissolved organic carbon flux from peat‐covered catchments: evidence for a drought effect?     

F. Worrall  T. P. Burt  J. Adamson 《水文研究》2008,22(16):3181-3193

This study considers three long records of dissolved organic carbon (DOC) flux from two catchments with peat‐covered headwaters. The catchments vary in size from 11 to 818 km² and the records are at least 12 years old, with one record going back to 1965. The study compares both annual and monthly DOC flux records with a range of hydroclimatic indicators in order to test which component of droughts may contribute to increasing DOC flux. The study found that: (1) there was no significant correlation between any of the proposed drought variables and DOC flux in any of the study catchments over periods of up to 34 years; (2) the most important variable for explaining the DOC flux was the runoff from the catchments overlying a seasonal cycle and an underlying upward trend was present in some records; (3) the residual time‐series, after removal of the best‐fit models, showed no evidence of increased production after times of severe drought. The lack of any evidence for any additional biogeochemical reactions associated with drought supports evidence that DOC loss from peat is limited by its solubility and that its production is fast on the time‐scale of runoff events. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Some thoughts on the integration of spatial analysis and Geographic Information Systems   总被引：5，自引：0，他引：5  

Duane F. Marble 《Journal of Geographical Systems》2000,2(1):31-35

It is past time for us to examine the relationship that exists between what we commonly call spatial analysis on the one hand, and geographic information systems or GIS on the other. GIS technology is widely used but seems to incorporate only a portion of the tools found in spatial analysis. Spatial analysis can be accused of overly simplistic approaches that severely limit its practical utility. This paper suggests that discarding myopic views and meeting upon a common ground of increased knowledge of modern computing concepts and techniques, including object-orientation, can prove extremely fruitful to both sides.  相似文献   

卫星资料揭示的青藏高原对流层上层温度气候演变趋势特征     

明绍慧  秦正坤  黄瑜 《高原气象》2019,(2):264-277

利用1982—2016年MSU/AMSU-A亮温资料,分析了青藏高原地区对流层上层温度的气候趋势及其演变特征,并利用ERA-Interim和NCEP-R2再分析资料的相应高度大气温度资料进行了对比分析。结果表明,青藏高原地区对流层高层卫星亮温资料总体表现为逐渐增暖现象,这与再分析资料的对应层次大气温度变化有很好的相似性。基于集合经验模式分解方法 EEMD的非线性趋势分析表明,青藏高原地区对流层上层亮温的增温首先出现在青藏高原中部,随着时间演变,增温现象逐渐向青藏高原四周扩散,最后在整个青藏高原地区都出现了一致增温现象。相比于NCEP-R2再分析资料而言,ERA-Interim再分析资料300 h Pa大气温度的演变趋势与观测亮温有很好的相似性,只是增温现象是首先在青藏高原附近,随着时间推移,增温现象逐步向周边地区扩张,最终整个青藏高原地区出现了整体升温现象。但是NCEP-R2再分析资料则是与上述两种资料的温度演变特征有很大的差异,其300 h Pa高度大气温度在前20年表现为明显的降温特征,在最近10年才出现了增温,并逐步向周边地区扩张的现象。  相似文献   

Completion and stimulation trends in North American unconventional plays and resulting impact on well productivity          下载免费PDF全文

Roman Galchenko  Qing Liu  Yan Gao  Yu Liu  David He  Josh Zhang  Huailiang Liu  Xiaohua Ke 《探矿工程》2021,48(10):1-12

过去十年,非常规油气勘探开发在全球范围内大幅扩张。水平钻井和多级水力压裂技术也在不断地发展和创新,使得超长水平井成为可能。同时,因为压裂强度不断增加,作业者可以最大限度地提高储层接触面积和对储层的改造体积 （SRV）。然而,完井优化方面的挑战仍然存在,作业者持续不断地尝试和试验各种完井与增产参数组合,以确保非常规油气藏开发的经济可行性。优选最佳的完井与增产参数组合是一项非常关键的任务,应结合油气田的具体储层特征进行优化。本文总结了2014—2020年间北美9个主要非常规油气藏的压裂增产趋势,包括Marcellus, Haynesville, Barnett, Utica, Bone Spring, Bakken, Wolfcamp Midland, Eagle Ford, Scoop/Stack。分析了各油气田几个关键的完井和增产参数的整体趋势,同时还评估了单个参数（如水平段压裂长度、支撑剂强度、段间距等）对井产能的影响。然后对比分析相应的初始井产量（90 天平均初始产量）,评估各个参数对产能的影响,从而确定每个完井参数的最佳范围,以实现产能最优化。  相似文献   

地貌学研究趋向与教材内容构建   总被引：1，自引：0，他引：1  

付旭东  张桂宾  潘少奇 《测绘科学》2015,(10):171-174

针对我国地貌学教材既滞后于学科发展,又不能适应新时期人才培养的问题,该文基于近20年来国际地貌学研究内容及发展趋势的分析,提出在现行地貌学教材基础上,增加行星地貌、生物地貌、地貌系统与气候变化、数字地貌、中国地貌概要五个版块内容;教材结构可设计为绪论、内营力地貌、外营力地貌、行星地貌、中国地貌概要、地貌调查与研究方法六部分;将部门地貌学内容删减至整个教材的50%左右;在绪论中增补近20年地貌学理论、技术方法进展,在每章末尾增列建议阅读文献和书目;更新地貌灾害和应用地貌案例、地貌调查与研究方法;制作教学课件和光盘;编写与教材配套的实习指导书。  相似文献