关于美中基础地理信息产品及其分发模式的思考     

顾纳  周星  刘丽芬  吴剑锋 《北京测绘》2003,(4):6-9

作为当今经济和科技最发达的国家,美国在基础地理信息产品建设和分发服务方面是代表世界最先进水平的国家之一,其丰富的基础地理信息系列产品、优秀的网络分发服务系统、完善的数据共享和更新策略等都值得我们学习和借鉴。本文介绍了美国基础地理信息产品的种类、发展及其分发服务模式,并根据我国的实际情况,在相关方面提出了几点建议。  相似文献   

New evidence for age variation and scale effects of permeabilities of young oceanic crust from borehole thermal and pressure measurements     

Keir Becker  Earl E. Davis 《Earth and Planetary Science Letters》2003,210(3-4):499-508

In 1996, long-term sealed-hole hydrological observatories with subseafloor temperature and pressure sensors were installed in four cased holes drilled by the Ocean Drilling Program into sedimented young oceanic crust east of the Juan de Fuca Ridge. Data recovered over a year later showed that all four holes displayed temperature profiles indicative of vertical fluid flow immediately prior to their being sealed. Warm water was being produced from basement in two cases, and cool ocean bottom water was being drawn into basement at the others. Linear flow rates of 60–200 m/h were estimated from the perturbation of the temperature profiles relative to undisturbed geothermal gradients at the sites. The pressure differentials driving the flow were also measured at the time of the observatory installations, allowing estimates of permeabilities of the upper crustal sections penetrated by the holes. Estimated permeabilities vary systematically with age, ranging from about 10⁻¹⁰ m² in the youngest site (0.9 Ma) to 10⁻¹² m² in the oldest site (3.6 Ma), confirming an apparent reduction of permeability with age determined with packer experiments at three of the same sites. Combined with other estimates of permeabilities in the same holes using methods with different scales of investigation, the new permeability estimates also provide evidence for a significant scale dependence of permeability in the upper oceanic crust.  相似文献   

The closing of a seaway: ocean water masses and global climate change     

Caroline H. Lear  Yair Rosenthal  James D. Wright 《Earth and Planetary Science Letters》2003,210(3-4):425-436

The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Northern Hemisphere Glaciation (NHG). The cause and effects of these changes are still debated. We use a multiproxy approach to determine the relative timing of the closure of the Panama gateway, changes in Atlantic circulation, global cooling and ice sheet growth. Benthic foraminiferal Mg/Ca records from a Pacific and an Atlantic Site have been produced and are interpreted in terms of bottom water temperatures. These Mg-temperature records are combined with published benthic δ¹³C, δ¹⁸O and erosion records to reconstruct the flow of proto-North Atlantic Deep Water (proto-NADW) over the past 12 Ma. The results suggest that between 12.5 and 10.5 Ma, and again between about 8.5 and 6 Ma, a nutrient-depleted water mass that was colder (by 1–2°C) and fresher than the intervening deep water mass filled the Atlantic basin. This proto-NADW became warmer (by 1°C) and saltier between 6 and 5 Ma, coincident with the restriction of surface water flow through the Central American Seaway. The Mg-temperature records define a subsequent global cooling trend of 3.5°C between 5 Ma and today. Early NHG in the late Miocene was perhaps related to the formation of the relatively cold, fresh proto-NADW. The formation of the warmer and saltier proto-NADW in the early Pliocene may have initially limited Northern Hemisphere ice growth. However, the increased moisture released at high northern latitudes associated with formation of ‘warm’ proto-NADW, coupled with the global temperature decrease of deep (and hence polar surface) waters, likely helped initiate the intense NHG of the Plio–Pleistocene.  相似文献   

西部大开发战略背景下的地区工业化   总被引：1，自引：0，他引：1  

曾刚  纪慰华 《世界地理研究》2003,12(2):74-78,60

目前，阻碍西部地区工业化的主要问题包括：(1)土地、劳动力、基础设施等要素条件差；(2)离经济核心区距离远；(3)生态保护压力大，产业进入门槛高；(4)所有制结构不太适合市场经济发展的要求；(5)政策等软环境有待进一步改善。西部大开发战略为西部地区工业化提供了历史性机遇。首先，植树种草的生态环境政策迫使农民从乡村走进城市；其次，中央政府向西部地区转移支付的资金支持增多；第三，东西部人员交流逐渐增多；第四，对外开放程度提高。因此，应该扩大开放度，注意投资多元化建设，提高基础设施建设规划的针对性，重点支持第三方物流发展，规范市场，大力发展劳动密集型工业，以推动我国西部地区工业化进程。  相似文献   

A Catalogue of Earthquakes With Moment Magnitude of the Center-Southern Asia Test Area of the Global Seismic Hazard Assessment Program     

Yang Zhixian  Zhang PeizhenInstitute of Crustal Dynamics  SSB  Beijing  China Institute of Geology  SSB  Beijing  China 《中国地震研究》1998,(1)

We compile a regional catalogue of earthquakes with moment magnitude of the Center-Southern Asia test area(20°-35°N,85°-105°E)for the Global Seismic Hazard Assessment Program(GSHAP).There are significant inhomogeneous and uncompleted data,and n uniformity of earthquake magnitudes in this test area because this region is situated on the boundaries of many countries,such as China,India,Nepal,Vietnam,etc.We establish a relationship between Gutenberg surface-wave magnitude and IASPEI surface-wave magnitude,which can be used for conversion of different magnitude scales into moment magnitude for this catalogue.A catalogue of events with Mw≥6.0 of this test area is given at the end of this paper.  相似文献   

90年代国际岩石圈计划研究进展     

王军芝  聂高众 《地球科学进展》1998,13(1):27-33

概要地介绍了90年代国际岩石圈计划及其下属任务组和工作委员会的活动情况和研究进展,并报道了可能被纳入该计划的新研究项目。  相似文献   

《中国21世纪议程气象行动计划》简介     

陈新强  郑国光  周天军 《地球科学进展》1998,13(3):306-311

阐述了《中国21世纪议程气象行动计划》制定的背景及其对国家可持续发展的重要意义,在此基础上,扼要地介绍了《中国21世纪议程气象行动计划》的主要内容,包括气象可持续发展的战略与对策、防灾减灾、保护气候和大气环境、气候资源开发利用、人工影响天气、科技与教育、政策法规、社会参与和国际合作等。  相似文献   

高放废物地质处置战略讨论          下载免费PDF全文

傅冰骏 《探矿工程》2004,31(9):1-5

概述了全球核电开发情况，介绍了高放废物地质处置国际态势及发展动向，对我国有关工作提出了意见和建议。  相似文献   

The oxygen isotopic composition and temperature of Southern Ocean bottom waters during the last glacial maximum     

Mitchell J Malone  Jonathan B Martin  Ulysses S Ninnemann  Timothy S White 《Earth and Planetary Science Letters》2004,222(1):275-283

We provide two new determinations of the oxygen isotopic composition of seawater during the last glacial maximum (LGM). High-resolution oxygen isotopic measurements were made on interstitial waters from Ocean Drilling Program (ODP) Sites 1168 and 1170 in the southeast Indian Ocean sector of the Southern Ocean. We use a diffusion-advection numerical model to calculate the glacial-interglacial change in bottom-water δ¹⁸O_sw from the pore water δ¹⁸O profiles; the first such determinations from this part of the oceans. Statistical analyses of the model runs indicate that Circumpolar Deep Water (CDW) δ¹⁸O_sw changed by 1.0-1.1±0.15‰ since the last glacial maximum (LGM). Our results are consistent with a previous calculation from a South Atlantic Southern Ocean location (ODP Site 1093) also situated within CDW. The new values determined in this study, together with previous estimates, are converging on a global average Δδ¹⁸O_sw of 1.0-1.1‰.Using the calculated bottom-water δ¹⁸O_sw, we have extracted the temperature component from the benthic foraminiferal δ¹⁸O record at Sites 1168 and 1170. Since the LGM, bottom waters at these two sites warmed by 2.6 and 1.9°C, respectively. The absolute temperature estimates for the LGM (−0.5°C [Θ=−0.6°C] at Site 1168 and −0.2°C [Θ=−0.4°C] at Site 1170) are slightly warmer than those reported from previous studies using the same technique, but are consistent with more homogenous deep-ocean temperatures during the LGM relative to the modern.  相似文献   

The Weather Forecasting System for Poseidon - an Overview     

A. Papadopoulos  P. Katsafados  G. Kallos  S. Nickovic 《Journal of Atmospheric & Ocean Science》2002,8(2):219-237

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