千百年尺度气候快速变化及其数值模拟研究进展   总被引：1，自引：0，他引：1  

靳立亚  陈发虎 《地球科学进展》2007,22(10):1054-1065

千百年尺度全球气候快速变化是古气候研究中的一个重要内容。研究发现，末次冰期和全新世都存在着千年、百年尺度的快速气候变化，其变化幅度可以达到典型的地质变化或天文因子所造成的冰期/间冰期的气候振荡幅度，同时这些古气候事件具有全球性。对冰期和全新世气候变化的数值模拟揭示了气候系统对地球轨道参数变化的响应以及海洋、植被、冰盖、温室气体等反馈因子的重要性,其中大洋温盐环流对北大西洋淡水注入的敏感性与末次冰期和全新世气候快速变化密切相联。利用中等复杂程度的气候模式（EMIC）CLIMBER 2模拟了末次冰期典型时段（60~20 ka BP）D/O和Heinrich事件以及东亚气候的响应过程。模拟研究揭示了全新世青藏高原冰雪环境对亚洲—非洲季风气候的显著影响。今后的古气候模拟研究将在改进模式分辨率、结合古气候代用资料确定更加符合历史时期边界条件以进一步改善气候模式的基础上,更加注重气候突变机制的研究以及加强全球变化背景下的区域气候的长期变化研究。  相似文献   

关于地震灾害快速评估系统的思考   总被引：5，自引：0，他引：5  

杨天青  姜立新 《地震》2005,25(3):123-128

基于地震快速评估经济损失结果与地震现场调查得到的经济损失结果有较大的差异现象, 为了进一步提高地震快速评估经济损失结果的精确性, 笔者通过对地震快速评估经济损失结果和实际现场调查得到的经济损失结果进行对比研究, 并从建筑物单价和建筑物损失比的角度对快速评估结果进行修正, 以发生在云南境内的10次典型地震为例, 初步得出了对地震经济损失快速评估结果粗略的修正系数。 在一定程度上较大提高了地震快速评估经济损失的精确性。 为地震救援指挥工作提供了更加可靠的依据。  相似文献   

Assessing the optimal preprocessing steps of MODIS time series to map cropping systems in Mato Grosso,Brazil     

《International Journal of Applied Earth Observation and Geoinformation》2020

The adoption of new cropping practices such as integrated Crop-Livestock systems (iCL) aims at improving the land use sustainability of the agricultural sector in the Brazilian Amazon. The emergence of such integrated systems, based on crop and pasture rotations over and within years, challenges the remote sensing community who needs to implement accurate and efficient methods to process satellite image time series (SITS) in order to come up with a monitoring protocol. These methods generally include a SITS preprocessing step which can be time consuming. The aim of this study is to assess the importance of preprocessing operations such as temporal smoothing and computation of phenological metrics on the mapping of main cropping systems (i.e. pasture, single cropping, double cropping and iCL), with a special emphasis on the iCL class. The study area is located in the state of Mato Grosso, an important producer of agriculture commodities located in the Southern Brazilian Amazon. SITS were composed of a set of 16-day composites of MODIS Vegetation Indices (MOD13Q1 product) covering a one year period between 2014 and 2015. Two widely used classifiers, i.e. Random Forest (RF) and Support Vector Machine (SVM), were tested using five data sets issued from a same SITS but with different preprocessing levels: (i) raw NDVI; (ii) raw NDVI + raw EVI; (iii) smoothed NDVI; (iv) NDVI-derived phenometrics; (v) raw NDVI + phenometrics. Both RF and SVM classification results showed that the “raw NDVI + raw EVI” data set achieved the highest performance (RF OA = 0.96, RF Kappa = 0.94, SVM OA = 0.95, SVM Kappa = 0.93), followed closely by the “raw NDVI” and the “raw NDVI + phenometrics” datasets. The “NDVI-derived phenometrics” alone achieved the lowest accuracies (RF OA = 0.58 and SVM OA = 0.66). Considering that the implementation of preprocessing steps is computationally expensive and does not provide significant gains in terms of classification accuracy, we recommend to use raw vegetation indices for mapping cropping practices in Mato Grosso, including the integrated Crop-Livestock systems.  相似文献   

Land-based adaptation to global change: What drives soil and water conservation in western Africa?     

《Global Environmental Change》2015

Conservation of land resources is a promising strategy for sustainable agricultural intensification in order to adapt dryland farming systems to climate, market and other stresses. At a local level, factors that drive the adoption of conservation measures operate and interact in specific ways. Linking our knowledge of the local specifications of these drivers to regional and global patterns of vulnerability can significantly enhance our understanding of land-based adaptation to global change. However, the factors that influence the adoption of conservation practices remain actively debated. Therefore, this study presents a meta-analysis of case studies that investigate the adoption of soil and water conservation measures, as an important approach to resource conservation. Synthesising 63 adoption cases in the drylands of western Africa, this meta-analysis reveals a multitude of factors that drive the adoption of soil and water conservation practices. The drivers differ strongly between particular practices and methods of analysis used in the case studies. Contributing to the broader debate on resource conservation, the findings highlight the adoption of soil and water conservation measures as an emergent property of farming systems. They demonstrate the need to better understand the socio-ecological foundation of adoption and the pathways along which adoption evolves in space and time. This study concludes with methodological principles to advance future research on the factors that drive the adoption of soil and water conservation measures as a pre-requisite of improving land-based adaptation efforts.  相似文献   

When enough should be enough: Improving the use of current agricultural lands could meet production demands and spare natural habitats in Brazil     

《Global Environmental Change》2014

Providing food and other products to a growing human population while safeguarding natural ecosystems and the provision of their services is a significant scientific, social and political challenge. With food demand likely to double over the next four decades, anthropization is already driving climate change and is the principal force behind species extinction, among other environmental impacts. The sustainable intensification of production on current agricultural lands has been suggested as a key solution to the competition for land between agriculture and natural ecosystems. However, few investigations have shown the extent to which these lands can meet projected demands while considering biophysical constraints. Here we investigate the improved use of existing agricultural lands and present insights into avoiding future competition for land. We focus on Brazil, a country projected to experience the largest increase in agricultural production over the next four decades and the richest nation in terrestrial carbon and biodiversity. Using various models and climatic datasets, we produced the first estimate of the carrying capacity of Brazil's 115 million hectares of cultivated pasturelands. We then investigated if the improved use of cultivated pasturelands would free enough land for the expansion of meat, crops, wood and biofuel, respecting biophysical constraints (i.e., terrain, climate) and including climate change impacts. We found that the current productivity of Brazilian cultivated pasturelands is 32–34% of its potential and that increasing productivity to 49–52% of the potential would suffice to meet demands for meat, crops, wood products and biofuels until at least 2040, without further conversion of natural ecosystems. As a result up to 14.3 Gt CO₂ Eq could be mitigated. The fact that the country poised to undergo the largest expansion of agricultural production over the coming decades can do so without further conversion of natural habitats provokes the question whether the same can be true in other regional contexts and, ultimately, at the global scale.  相似文献   

Capacity,capability and cross-border challenges associated with marine eradication programmes in Europe: The attempted eradication of an invasive non-native ascidian,Didemnum vexillum in Wales,United Kingdom     

《Marine Policy》2014

Increasing recognition of the threat which invasive non-native species present to ecological and economic assets has led to a recent surge in international, regional and national policies. Within the European Union, a draft EU Regulation on the prevention and management of invasive alien species has been developed. The draft Regulation, published in 2013, recommends the creation of a list of invasive alien species of Union concern, wherein any Member State identifying newly establishing populations of these species must implement rapid eradication measures. The first recording of the invasive non-native ascidian Didemnum vexillum in Britain in 2008 in Wales, and subsequent eradication efforts, presents a timely opportunity to evaluate the United Kingdom׳s existing capability and capacity to undertake a rapid eradication in the marine environment in light of the draft EU Regulation, as well as highlighting some of the cross-border challenges facing the EU. Although the UK is often cited within Europe as having made significant progress in the field of invasion management, the lessons learned from the eradication process in Wales highlight that the UK is inadequately prepared to undertake rapid eradication measures in the marine environment and that the lack of a coordinated approach between nations has significant potential to devalue localised eradication efforts. A number of measures are discussed to enhance future capability both in the UK and the wider European Union including enhanced alerting mechanisms, science-based monitoring programmes to enable early detection, increased commitment of resources and the need for cross-border collaboration.  相似文献   

ANALYSIS OF EFFECT OF ENVIRONMENTAL POTENTIAL VORTICITY LOCATED AT SOUTH EDGE OF SOUTH ASIA HIGH ON INTENSIFICATION OF TROPICAL CYCLONES     

丁治英  邢蕊  徐海明  高勇 《热带气象学报(英文版)》2014,20(1):74-86

The NCEP 1°×1°reanalysis of June-to-September dataset between 2002 to 2009 is used in this study to conduct statistical analysis of the relationship between the environmental potential vorticity(PV)on 150 hPa located at the south edge of South Asia High(SAH)and TCs making landfall.The results show that 23 of the TCs are affected by the PV on 150 hPa located at the south edge of SAH between 2002 to2009,and three TCs'center pressure decline after the high-value environmental PV moves to the center of the TCs.These three TCs are Senlaku(0216),Bilis(0604)and Linfa(0903).Through diagnostic analysis from the viewpoint of isolines,we determined the relationship between the intensification of these TCs and the PV anomaly at high levels;the isentropic surface is close to the high level’s PV anomaly under the influence of the 150-hPa PV anomaly,leading to the decline of isentropic surfaces on both sides of the PV anomaly.Then the warm core of the middle and high levels of the TC strengthens and PV increases at the middle level,and both of them are beneficial to the reinforcement of the cyclonic vorticity in the low level.As a result,the center pressure of the TC declines.According to Wu’s theory of Slantwise Vorticity Development(SVD),the incline of the isentropic surfaces leads to the development of vertical vorticity,contributing to the vertical motion and the release of the latent heat.Then the warm core of the TC strengthens and the TC strengthens,too.Otherwise,piecewise PV inversion also shows that the high-level PV influences the mid-level more than the low level.  相似文献   

WRF-RUC在2014年江西汛期降水预报中的检验分析   总被引：1，自引：0，他引：1  

徐星生  万明  薛谌彬  王海 《气象与减灾研究》2014,(3):23-28

利用江西省92个国家气象观测站雨量资料,对2014年汛期江西WRF-RUC系统的降水预报进行逐6 h、12 h和24 h晴雨检验、降水分级检验以及同期区域暴雨个例检验分析。结果表明:1)6 h、12 h、24 h晴雨检验PC评分分别达0.6、0.7、0.8,系统表现了稳定的预报性能。2)系统对小雨、中雨和大雨具有较好的预报能力,对局地暴雨、大暴雨的预报能力较弱,而对区域暴雨的预报具参考意义。3)系统有效地缩短了spin-up时间,系统在积分6 h后达到最佳预报性能,并在起报后6—12 h时段,预报效果最佳。4)系统对降水范围以及小雨、中雨、大雨过度预报,对暴雨、大暴雨范围预报比较合理。  相似文献   

红土型金矿中痕量金分析应用研究   总被引：1，自引：0，他引：1  

王枫  王毅泽  吕鹏飞 《云南地质》2011,30(3):353-356

总结红土型金矿运用痕量金分析的理论基础,对不同金标样样品进行准确度、精密度检查,表明痕量金分析可以满足矿点的检查、异常查证的基本要求。与室内法相比,本法有方便、快捷、低成本、高效率及易掌握等特点。  相似文献   

曼氏无针乌贼(Sepiella maindroni)-肌动蛋白基因的 cDNA 全长克隆与序列分析     

李继姬  郭宝英  吴常文 《海洋与湖沼》2011,42(6):787-793

采用RT-PCR和快速扩增cDNA末端(rapid amplification of cDNA ends, RACE)技术首次克隆了曼氏无针乌贼?-肌动蛋白基因的 cDNA 全序列, 该序列全长为 2000bp, 由长 197bp 的 5’非翻译区(untranslated region, UTR), 669bp 的 3’非翻译区, 和 1134bp 的开放阅读框(open reading frame, ORF)组成。阅读框共编码 377 个氨基酸, 推算的分子量约为 42.0kDa, 理论等电点为 5.16。曼氏无针乌贼-actin 氨基酸序列中 Ile12、Ser172、Ser174、Gln223、His227、Ile231、Gly232、Ser320、Glu328、 Thr360等10个氨基酸残基具有特异性, 以及2个特殊的氨基酸残基位点和2个软体动物特有的氨基酸残基。曼氏无针乌贼?-actin 氨基酸序列与软体动物、节肢动物、脊椎动物的相似性高达 97%。NJ法系统进化分析显示曼氏无针乌贼首先与软体动物聚在一起, 然后与节肢动物聚在一起, 再与鱼类、两栖类、哺乳类聚在一起。  相似文献