2008年初极端寒冷天气对荔枝龙眼成花的利弊分析   总被引：4，自引：1，他引：3  

陈国保  李莲英 《气象研究与应用》2008,29(2):57-59,65

2008年初玉林市出现了一次与历史同期相比持续时间最长,平均温度最低、日照时数最少、总降水量居历史第二位的极端寒冷天气过程。通过对2008年1~4月份荔枝龙眼的观测和调查资料进行分析后发现,这次阴冷无霜的天气过程对荔枝龙眼的成花是既有利,也有弊,但总体上是弊大于利。因为持续长时间的低温和日照严重不足既抑制了冬梢,也抑制了花芽分化,最终导致了成花率明显偏低、花质差、雌花比率低、花期短等不良后果。鉴于这次罕见的极端寒冷天气对荔枝龙眼成花的影响,今后应从提高中长期天气预报准确率和栽培管理技术等方面来做好应对全球气候变暖背景下极端气象灾害的防御工作。  相似文献   

Spatial dynamics of estuarine water surface temperature from airborne remote sensing     

Richard D. Hedger  Tim J. Malthus  Andrew M. Folkard  Peter M. Atkinson 《Estuarine, Coastal and Shelf Science》2007,71(3-4):608-615

This paper examines the applicability of airborne remote sensing to the characterization and quantification of the spatial dynamics of water surface temperature (WST) within estuaries. For this, a series of successive airborne Thematic Mapper thermal images was acquired of Kirkcudbright Bay, an estuary in the United Kingdom, on two dates. Spatial dynamics were determined by two techniques: (1) qualitatively, which involved interpreting features ‘by eye’; and (2) by the velocimetric technique of maximum cross correlation (MCC). Qualitatively, complex spatial dynamics were identified over a wide range of spatial and temporal scales, associated with the creation and dissipation of eddies, and the convergence and divergence of fronts, all of which were superimposed on the synoptic tidal flow. MCC was effective for producing synoptic velocity fields, but the minimum cell size was constrained by image noise, limiting the ability to analyze small-scale spatial dynamics. The effectiveness of MCC was related to the ratio of spatially correlated variance to spatially independent variance, as estimated from the variogram. Suggestions for optimizing the application of airborne remote sensing to estuarine spatial dynamics are presented.  相似文献   

An investigation into technetium binding in sediments     

Miranda J. Keith-Roach  Katherine Morris  Henning Dahlgaard 《Marine Chemistry》2003,81(3-4):149-162

Coastal environments with reducing waters and/or sediments represent potential sinks for ⁹⁹Tc discharged to sea. Here, we have examined estuarine sediments from four geochemically distinct locations that have been exposed to ⁹⁹Tc discharged from Sellafield. Both the relative uptake and the operationally defined sediment “component” that holds the Tc were investigated in order to establish whether particular biogeochemical processes are predominately responsible for reducing and binding Tc in sediments. Despite the artefacts that can pose problems for sequential extractions, this scheme [Int. J. Environ. Anal. Chem. 51 (1993) 187] appears to be robust with regard to Tc. The results show that relative uptake of Tc varied greatly between the sites, with the highest occurring at an almost permanently anoxic fjord (Mariager Fjord, Denmark), followed by a brackish, seasonally eutrophic fjord (Roskilde Fjord, Denmark), then a sub-oxic salt marsh (which receives particle bound radionuclides from a more reducing mud patch; Esk Estuary, UK) and finally sulfidic and iron-reducing muddy sandy sediments (Needle's Eye, Solway Firth, Scotland). High relative uptake at the fjords was explained by the greater mixing of Tc-labelled oxic seawater into the part of the system where reduction of TcO₄⁻ was possible. Uptake at Mariager Fjord was higher than at Roskilde Fjord, reflecting the highly reducing geochemical conditions in the water body. Low uptake at Needle's Eye may be related to the speciation of technetium at this site as the sequential extraction data suggest that Tc is associated with the carbonate phase here. Tc carbonates are largely soluble, and this is the first observation of Tc association with carbonate fractions in the natural environment. The other three sites showed that organic matter, in conjunction with reducing conditions, was very important for binding and retaining Tc in sediments. The specific role of sulfides in controlling Tc retention in sediments was unclear because sulfides and organic matter are leached simultaneously in the sequential extraction scheme we applied, but there was evidence that Tc was not associated with acid-volatile iron monosulfides.  相似文献   

一部具有理论意义和应用价值的科学论著——评《土地资源开发与区域协调发展》     

冯海燕 《山地学报》2006,24(4):510-512

《土地资源开发与区域协调发展》一书是对陕北榆林典型地区近10多年跟踪研究的初步总结,是基于科学发展观,全面审视我国重点能源重化工基地区域土地资源开发与区域发展协调关系的最新科研成果,具有理论意义和应用价值。该成果将在区域土地资源开发、经济发展与生态建设的具体实践,以及统筹区域协调发展的科学决策中发挥指导作用。  相似文献   

玉林市近50年来干旱的发生规律及防御对策   总被引：11，自引：0，他引：11  

陈国保陈利东  陆小林 《广西气象》2006,27(3):40-43

根据玉林市春、夏、秋三个季节干旱对农业生产的影响，参照历年的旱情资料，确定出干旱的农业气象指标，分析47a来干旱的时空分布规律和特点，并针对玉林市的具体情况提出一些防御干旱的对策。  相似文献   

Mechanism and regulation of land degradation in Yulin district     

LIU Yansui  ZHANG Xiaoping  LI Xianwen  Jay Gao 《地理学报》2003,13(2):217-224

Yulin district is located in the transitional zone between Mu Us Desert and Loess Plateau of northern Shaanxi Province, thus it is particularly vulnerable to degradation due to its fragile ecosystem and intense human activities there. The purpose of this study is to explore the mechanism, process and driving force of land degradation in area with vulnerable eco-environment within the context of increasing population and intensifying human economic activities, and then find out the patterns and countermeasures of how to control them using the economic and technological ways. In detail, this study includes three main sections: the first section analyzes the mechanism, causes and characteristics of land degradation, which can be achieved by the typical field investigations and systematical analysis within the regional natural, social and economic context. Based on the technologies of remote sensing and GIS, and combined with the modeling methods, the second section reveals the change characteristics of land use and its driving force from 1990 to 2000; As to the third section, feasible countermeasures of how to prevent the degradation and rehabilitate the regional ecology are proposed, which are studied from the perspective of harmony between nature and economy, and the conception of regional sustainable development.  相似文献   

陕北榆林地区沙漠化土地类型及时空变化分析   总被引：8，自引：1，他引：8       下载免费PDF全文

张　莉王飞跃  张铁军 《中国地质》2002,29(4):426-430

根据1987年和1999年两个时相TM遥感影像解译成果，运用地理信息系统空间分析方法及数理统计方法，分析了陕北榆林地区1987-1999年间土地沙漠化程度和土地沙漠化时空分布变化特征。并有所好转，这主要得益于当地政府对土地沙漠化的积极治理和有效政策，生态环境脆弱，气候干燥，多风是本区土地沙漠化的主要自然驱动因素，不合理的人类活动则是沙漠化的诱因，人为的积极治理措施可以有效控制沙漠化的进程。  相似文献   

A GIS-based research on the distribution of rural settlements in Yulin of northern Shaanxi     

ZHAO Mu-dan  TANG Guo-an  SHI Wen-zhong  LIU Yong-mei 《地理学报》2002,12(2):171-176

The development and distribution pattern of rural settlements was greatly limited by their natural and social environment. Taking Yulin prefecture in northern Shaanxi’s Loess Plateau area as an example, 1:250,000 map-scale national geographical database as a major information source, a GIS-based research was conducted to investigate the spatial distribution of the rural settlements. In this paper, many significant characteristics of the rural settlement distribution are reviewed by means of a series of GIS-based information processing methodology. The results obtained in this study should be helpful for the urban and rural settlements reconstruction planning in this area.  相似文献   

遥感与GIS支持下的榆林地区土地利用动态变化研究   总被引：24，自引：9，他引：15  

高小红  王一谋 《干旱区地理》2004,27(1):106-111

利用1986、1996和2000年人机交互解译的遥感影像资料,采用GIS空间分析技术,通过叠加3个不同时期的土地利用图,分析了榆林地区1986～2000年期间土地利用时空变化特征,同时还分析了榆林地区14年间沙地逆转恢复的情况。结果表明：1986～1996年期间土地利用变化主要表现为：沙地减少了22．25％,草地、林地和城乡居住建设用地分别增加了6．51％、4．63％和3．55％。1996～2000期间,沼泽地、盐碱地分别减少了26．11％、24．39％,沙地仅减少0．79％,草地减少了2．86％,林地仅增加了0．17％,而旱地增加了3．28％。城乡居住建设用地增加了14．13％。14年间沙地面积减少了128684．17hm^2,沙地净逆转为草地118872．99h^2、旱地3605．07hm^2、林地4049．52hm^2。  相似文献   

基于RS和GIS长城沿线沙漠化动态研究   总被引：1，自引：1，他引：0  

王晓峰  任志远  马智民 《中国沙漠》2009,29(4):623-627

基于遥感影像,以长城沿线榆林地区为研究对象,在野外实地观测和验证的基础上利用RS和GIS平台对该地区沙漠化进行动态变化研究。结果表明:在1988—2002年沙漠化面积在逐步减少;按照沙漠化的类型分析,在1999年之前,逆转区的面积为1 221 682.0 hm2,发展区的面积为1 285 603.0 hm2,发展区的面积大于逆转区的面积;1999年之后,发展区的面积为680 374.6 hm2,逆转区的面积为1 488 989.0 hm2,逆转区的面积远大于发展区的面积;从沙漠化程度分析,轻度和潜在沙漠化的面积在大幅度地降低,但中度以上的沙漠化面积仍然在蠕动扩展,这一数据表明榆林地区沙漠化的形势仍然不容乐观,要居安思危。  相似文献