夏季青藏高原大气热源与西南地区东部旱涝的关系   总被引：9，自引：5，他引：9  

李永华  卢楚翰  徐海明 《大气科学》2011,35(3):422-434

利用1959～2006年西南地区东部20个测站逐日降水量资料和NCEP/NCAR再分析月平均资料,分析了夏季青藏高原大气热源特征,指出了影响西南地区东部夏季旱涝的热源关键区域,并就关键区大气热源对该区域夏季旱涝的影响进行了诊断,得出了以下主要结论:西南地区东部夏季降水与高原主体东南部的热源变化关系密切,当该区域(该区域...  相似文献   

A Comparative Analysis of Primary and Extreme Characteristics of Dry or Wet Status between Asia and North America   总被引：1，自引：0，他引：1  

HUA Lijuan  MA Zhuguo  ZHONG Linhao 《大气科学进展》2011,28(2):352-362

In this study, the Palmer Drought Severity Index (PDSI) was used to analyze the average and extreme dry/wet states of Asia and North America from 1953 to 2003. The results indicate that the two continents underwent drying trends during this period. Compared with North America, Asia showed more severe drought trends. However, more significant and regular seasonal variation for drought was found in North America. The driest regions in Asia were located in the northern region of China, Mongolia, and eastern mid-Siberian plateau. Most regions in central North America were relatively wetter than other regions. The northern and southwestern regions of North America, as well as the Atlantic and Pacific coastal areas, experienced the most drought during this period. A sharp increase of the drought area and the number of extreme drought events took place from 1997 to 2003 in both Asia and North America. Severe drought events were more likely to occur during the summer on both continents. Asia had the most extreme drought events during July, but North America reached its highest drought frequency from June to September. In Asia, a persistent increasing trend of extreme drought emerged throughout the studied period. However, a more complex evolution of drought emerged in North America: a decreasing trend appeared before the mid-1960s and an increasing trend appeared after the late 1970s. A relatively steady dry/wet status was observed between the mid-1960s and the late 1970s. The role of exceptional, extreme drought events with respect to the La Nin?a event was considered during 1997–2003.  相似文献   

Inland capture fisheries in the Mekong and their place and potential within food-led regional development     

R.I. Arthur  R.M. Friend   《Global Environmental Change》2011,21(1):219-226

The inland capture fisheries of the Mekong represent critical sources of nutrition in rural diets in a region that faces endemic food and nutritional deficits. However within regional development debates that prioritize utilising the waters of the Mekong to generate electricity, capture fisheries are often presented as ultimately doomed, and therefore as an unfortunate, but necessary trade-off for hydropower. At the heart of these debates, lie contested definitions of development. The notion that fisheries could or should be traded-off for some other form of development exemplifies this tension.This paper draws on anthropological approaches to policy analysis based on discourse and narratives. We begin by placing the conventional wisdom regarding the place of fisheries in regional development under closer scrutiny. We then explore the potential for a counter narrative based around food and food sovereignty, in which fisheries and fishers are drivers, rather than costs of development. We argue that fisheries provide a range of livelihood and developmental values that cannot be replaced and that their management continues to hold potential for strengthening independence and self-reliance. In doing so, we build on empirical evidence from the Lao PDR, a country with a rich capture fishery but also endemic food crises, and also a national policy commitment to both poverty reduction and extensive large-scale hydropower development. As such, this paper attempts to reframe the debate on development in the Mekong. The paper has wider significance for considering how a broader focus on food and food producers can generate alternative development pathways.  相似文献   

PCBs in Central Vietnam coastal lagoons: levels and trends in dynamic environments     

Giuliani S  Piazza R  Bellucci LG  Cu NH  Vecchiato M  Romano S  Mugnai C  Nhon DH  Frignani M 《Marine pollution bulletin》2011,62(5):1013-1024

PCBs were analysed in surficial sediments and selected sediment cores collected between 2002 and 2008 in Central Vietnam coastal lagoons. The aim was to determine contamination levels and trends, and to evaluate the effects of anthropogenic pressures and natural events. Samples were mostly fine-grained with low total PCB concentrations (0.367-44.7 μg kg⁻¹). Atmospheric transport and post depositional processes modify to some degree the fingerprint of PCB inputs to the environment favouring the predominance of 3, 4 and 5 chlorinated congeners. The similarity of congener distributions in contemporary surficial samples also suggests the presence of a unique source over the entire study area, probably connected to mobilisation and long range transports from land-based stocks. The removal of consistent sediment layers is hypothesised based on repeated samplings of the same area. Natural meteorological events (such as typhoons) are suspected to be responsible for these sediment losses.  相似文献   

Proximate environmental drivers of coral communities at Palmyra Atoll: establishing baselines prior to removing a WWII military causeway     

Williams GJ  Knapp IS  Maragos JE  Davy SK 《Marine pollution bulletin》2011,62(8):1842-1851

A management proposal aims to partly remove a WWII military causeway at Palmyra Atoll to improve lagoon water circulation and alleviate sedimentation stress on the southeast backreef, an area of high coral cover and diversity. This action could result in a shift in sedimentation across reef sites. To provide management advice, we quantified the proximate environmental factors driving scleractinian coral cover and community patterns at Palmyra. The proportion of fine sedimentation was the optimal predictor of coral cover and changes in community structure, explaining 23.7% and 24.7% of the variation between sites, respectively. Scleractinian coral cover was negatively correlated with increases in fine sedimentation. Removing the causeway could negatively affect the Montipora corals that dominate the western reef terrace, as this genus was negatively correlated with levels of fine sedimentation. The tolerance limits of corals, and sediment re-distribution patterns, should be determined prior to complete removal of the causeway.  相似文献   

中国南天山晚石炭世—早二叠世花岗质侵入岩的岩石成因与地壳增生   总被引：9，自引：0，他引：9  

黄河  张招崇  张东阳  杜红星  马乐天  康健丽  薛春纪 《地质学报》2011,85(8):1305-1333

晚石炭世—早二叠世在中亚南天山造山带形成了大量的花岗质侵入岩.中国境内这些岩体以晚石炭世Ⅰ型花岗岩、早二叠世Ⅰ型和S型花岗岩以及最晚期的A型花岗岩为代表.不同类型的岩石在源区特征和岩浆形成的温压条件上存在一定的差异,而这些差异性反映了该时期内构造环境的演化过程.本文选取铁列克岩体、盲起苏岩体、英买来岩体、川乌鲁杂岩体、...  相似文献   

Geochemistry of lower Jurassic shales of the Shemshak Formation, Kerman Province, Central Iran: Provenance, source weathering and tectonic setting     

S.M. Moosavirad  M.R. Janardhana  M.S. Sethumadhav  M.R. Moghadam  M. Shankara 《Chemie der Erde / Geochemistry》2011,71(3):279-288

Lower Jurassic shales of the Shemshak Formation of Kerman Province, Central Iran, were analyzed for major and selected trace elements to infer their provenance, intensity of palaeoweathering of the source rocks and tectonic setting. Plots of shales on Al₂O₃ wt.% versus TiO₂ wt.% diagram and Cr (ppm) versus Ni (ppm) diagram indicate that acidic (granitic) rocks constitute the source rocks in the provenance. Average CIA, PIA and CIW values (84%, 92%, 93%, respectively) imply intense weathering of the source material. Plots of shales on bivariate discriminant function diagram reveal an active continental margin setting for the provenance. The inferred tectonic setting for the Lower Jurassic shales of the Shemshak Formation of Kerman Province is in agreement with the tectonic evolutionary history of the Central Iran during the Jurassic period.  相似文献   

对SQIP方法数据处理部分的尝试性改进的研究     

许晓庆  罗国富  马禾青 《地震研究》2011,34(3):365-371

从地震学定量综合预测方法(SQIP)的预报思路出发,对SQIP方法的具体数据处理作了探索性改进,针对西北地区东部中强震进行综合预测检验.结果表明改进后的方法具有一定地震预测能力和实用性,预测结果符合渐近式的预报思路.  相似文献   

地震分布非均匀性指标Kcv值及其在亚洲大地震预测中的应用研究     

邱玉荣  王晓青  郑友华  丁香  李智 《地震》2011,31(3):27-36

理论研究和实际预测表明地震空间分布非均匀性指标Cv值是一种有效的预测指标.但目前使用的Cv值在同一信度水平下,其置信区间大小与空间分布的事件样本数大小有关,不便于结果的分析比较.本文在Cv值基础上定义了一个新的预测指标Kcv,并基于强震时空概率增益预测模型及其单项预测方法预测效能检验的方法,依据亚洲地震重点研究区近20...  相似文献   

Imaging the mantle transition zone beneath eastern and central China with CEArray receiver functions   总被引：1，自引：0，他引：1  

Xinling Wang  Fenglin Niu 《地震学报(英文版)》2011,(1):65-75

We analyzed a total of 37 427 receiver-function data recorded by national and regional broadband seismic networks of the China Earthquake Administration to study the mantle transition zone beneath eastern and central China.Significant topography on both the 410-km and 660-km discontinuities was clearly imaged in the 3D volume of CCP (common-conversion-point) stacked images that cover an area of 102.5 E-122.5 E and 22.0 N-42.0 N.3D crustal and mantle velocity models were used in computing the Ps time moveout...  相似文献