Land use/land cover change detection and prediction in the north-western coastal desert of Egypt using Markov-CA     

《Applied geography (Sevenoaks, England)》2015

Detecting land-use change has become of concern to environmentalists, conservationists and land use planners due to its impact on natural ecosystems. We studied land use/land cover (LULC) changes in part of the northwestern desert of Egypt and used the Markov-CA integrated approach to predict future changes. We mapped the LULC distribution of the desert landscape for 1988, 1999, and 2011. Landsat Thematic Mapper 5 data and ancillary data were classified using the random forests approach. The technique produced LULC maps with an overall accuracy of more than 90%. Analysis of LULC classes from the three dates revealed that the study area was subjected to three different stages of modification, each dominated by different land uses. The use of a spatially explicit land use change modeling approach, such as Markov-CA approach, provides ways for projecting different future scenarios. Markov-CA was used to predict land use change in 2011 and project changes in 2023 by extrapolating current trends. The technique was successful in predicting LULC distribution in 2011 and the results were comparable to the actual LULC for 2011. The projected LULC for 2023 revealed more urbanization of the landscape with potential expansion in the croplands westward and northward, an increase in quarries, and growth in residential centers. The outcomes can help management activities directed toward protection of wildlife in the area. The study can also be used as a guide to other studies aiming at projecting changes in arid areas experiencing similar land use changes.  相似文献   

Monitoring land changes in an urban area using satellite imagery,GIS and landscape metrics     

《Applied geography (Sevenoaks, England)》2015

Monitoring land changes is an important activity in landscape planning and resource management. In this study, we analyze urban land changes in Atlanta metropolitan area through the combined use of satellite imagery, geographic information systems (GIS), and landscape metrics. The study site is a fast-growing large metropolis in the United States, which contains a mosaic of complex landscape types. Our method consisted of two major components: remote sensing-based land classification and GIS-based land change analysis. Specifically, we adopted a stratified image classification strategy combined with a GIS-based spatial reclassification procedure to map land classes from Landsat Thematic Mapper (TM) scenes acquired in two different years. Then, we analyzed the spatial variation and expansion of urban land changes across the entire metropolitan area through post classification change detection and a variety of GIS-based operations. We further examined the size, pattern, and nature of land changes using landscape metrics to examine the size, pattern, and nature of land changes. This study has demonstrated the usefulness of integrating remote sensing with GIS and landscape metrics in land change analysis that allows the characterization of spatial patterns and helps reveal the underlying processes of urban land changes. Our results indicate a transition of urbanization patterns in the study site with a limited outward expansion despite the dominant suburbanization process.  相似文献   

利用扫描电镜-电子探针研究四川杨柳坪镍铜硫化物矿床铂钯的赋存状态及沉淀机制   总被引：2，自引：2，他引：0  

戴婕  徐金沙  杜谷  王坤阳 《岩矿测试》2015,34(2):161-168

本文利用电子探针和配备能谱分析功能的扫描电镜对四川杨柳坪镍-铜硫化物矿床中铂钯的赋存状态进行了研究。结果表明,铂以独立矿物相砷铂矿和自然铂存在;钯以碲化物、碲铋化物、碲锑化物、锑化物及自然钯独立矿物相存在,也以类质同象形式分布在碲镍矿中(钯含量约10%),另外还以锑铋钯碲矿、六方锑碲钯矿、碲钯矿独立矿物相存,并以类质同象形式分布在Vavrinite(钯含量5%)和砷铂矿(钯含量1%~5%)中。杨柳坪矿床中铂钯元素沉淀与贱金属矿物(BMS)及晚期热液蚀变矿物蛇纹石、方解石密切相关,其沉淀经历了3个阶段:1早期高温阶段(1200~900℃),铂钯元素沉淀并包裹在BMS中;2中期中高温阶段(650~250℃),分离结晶作用使铂钯元素沉淀并分布BMS矿物的边部,同时该阶段热液来源的铂钯元素沉淀于BMS粒间;3晚期热液蚀变阶段(500~300℃),热液蚀变作用引起铂钯元素沉淀在蚀变矿物中或嵌布在BMS裂隙。本文研究成果为认识该矿床及同类型镍-铜硫化物矿床的铂钯成矿过程提供了新的依据。  相似文献   

Resilience as transformative capacity: Exploring the quadripartite cycle of structuration in a Mozambican resettlement programme     

《Geoforum》2015

The concept of resilience has emerged out of a complex literature that has sought to make sense of an increasingly interconnected world that appears ever more beset by crises. Resilience’s appeal is reflected by the burgeoning mass of literature that has appeared on the subject in the past five years. However, there is ongoing debate surrounding its usage, with some commentators claiming that the term is inherently too conservative a one to be usefully applied to situations of vulnerability in which more radical social change is required. This article extends existing efforts to formulate more transformative notions of resilience by reframing it as a double-edged outcome of the pre-reflective and critical ways in which actors draw upon their internal structures following the occurrence of a negative event, thus reproducing or changing the external structural context that gave rise to the event in the first place. By employing a structuration-inspired analysis to the study of small-scale farmer responses to a flood-induced resettlement programme in central Mozambique, the article presents a systematic approach to the examination of resilience in light of this reframing. The case study findings suggest that more attention should be paid to the facilitative, as well as constraining, nature of structures if vulnerable populations are to be assisted in their efforts to exert transformative capacity over the wider conditions that give rise to their difficulties.  相似文献   

武都万象洞方解石现代沉积体系δ~(18)O值月变化特征   总被引：1，自引：0，他引：1  

白晓  桑文翠  李丰山  张德忠 《地球化学》2015,44(3):245-253

万象洞所在地大气降水同位素值年内波动较大,变化起止时间存在显著的年际差异。观测期内,武都降水同位素δD-δ18O组合特征与周边城市降水同位素多年平均值重建的区域降水雨水线基本重合,洞穴所在地区降水同位素具有很好的区域代表性。洞穴滴水同位素值年内变化幅度较小,基本反映了当地大气降水同位素值的月加权平均水平。洞穴次生碳酸盐与洞穴滴水之间符合同位素平衡分馏基本规律。季节尺度上,不同监测点滴水及次生碳酸盐δ18O值因受地下水混合作用强弱差异及洞穴温度的小幅变化等影响而略有差异;年际变化上,夏季风爆发前后降雨量的权重及爆发时间的早晚对洞穴滴水-碳酸盐体系同位素水平存在一定的影响。万象洞洞穴滴水、石笋氧同位素信号在年代际尺度上可以很好地指示区域内大气降水的同位素变化特征。  相似文献   

孟加拉湾超级风暴费林对西藏强降水的影响分析     

德庆  徐珺  宗志平  赤曲  罗布坚参  代华光 《气象》2015,41(9):1086-1094

利用NCEP/NCAR(2.5°×2.5°)再分析资料和常规、非常规观测资料,通过环境场和中尺度特征较全面细致地分析了孟加拉湾风暴费林（Phailin）对西藏特大暴雪的影响。研究表明：“费林”对强降水的影响主要是登陆减弱为低压后,低压云系分两个阶段形成三个中尺度对流云团,对流云团在南支槽的作用下上高原。而强降水的发生和南风风速的大小有直接的对应关系,西南低空急流建立后西藏南部才出现强降水,而低空急流的建立是靠南支槽的贡献。南风风速和强降水的这一重要关系为此类天气提供了预报着眼点。  相似文献   

“频率匹配法”在集合降水预报中的应用研究   总被引：8，自引：1，他引：7  

李俊  杜钧  陈超君 《气象》2015,41(6):674-684

基于“频率匹配法”的思路,采用两种方法进行了集合降水预报的订正研究,一种方法是利用集合成员降水频率订正简单集合平均平滑效应的“概率匹配平均”法,另一种方法是利用实况降水频率订正集合成员降水预报系统偏差的“预报偏差订正”法,通过个例和批量试验,结果表明:(1)概率匹配平均法可以矫正简单集合平均的平滑作用所造成的小量级降水分布范围增大而强降水被削弱的负作用,这种改进对强降水区更显著,并且集合系统离散度越大这种改进也越大;但该方法对预报区域内总降水量的预报没有改进作用,不能改善预报的系统性偏差.(2)虽然预报偏差订正法对降水落区预报的改进有限,但可以订正模式降水预报的系统性误差,改进雨量预报以及集合预报系统的离散度特征和概率预报技巧;直接对集合平均预报进行偏差订正的效果优于单个成员偏差订正后的简单算术平均.(3)在对每个集合成员的降水预报进行偏差订正后,概率匹配平均仍可改善其简单平均的效果,因此在实际业务中,应该综合采用上述两种方法,以获得在消除系统性偏差的同时各量级降水分布又合理的集合平均降水预报.  相似文献   

2014年中国气候概况   总被引：6，自引：4，他引：2  

侯威  邹旭凯  王朋岭  叶殿秀  周兵  黄大鹏  李莹  赵琳  王有民  朱晓金  赵珊珊  王阳  钟海玲 《气象》2015,41(4):480-488

2014年,全国平均气温较常年偏高0.5℃,与1999年并列为1961年以来第六暖年;四季气温均偏高。全国平均降水量636.2 mm,接近常年,比2013年偏少3%;降水时空分布不均,辽宁、北京和河北偏少明显,冬、春、夏三季降水量均接近常年同期,秋季偏多。华南前汛期开始早、雨量多;西南雨季开始晚、结束早、雨量少;梅雨区降水量南多北少,江淮出现空梅;华北雨季不明显,出现空汛;华西秋雨开始早、结束晚、雨量多。夏季副热带高压脊线位置偏南,南海夏季风爆发晚,东亚夏季风强度略偏弱。2014年,我国气候属正常年景,极端天气气候事件少于2013年,暴雨洪涝、干旱等灾害偏轻,因灾造成死亡人数和受灾面积明显偏少,气象灾害属于偏轻年份。  相似文献   

青藏高原、中国东部及北美副热带地区夏季降水系统发生频次的TRMM资料分析   总被引：2，自引：1，他引：1  

周胜男  罗亚丽  汪会 《气象》2015,41(1):1-16

利用1998—2011年夏季（6—8月）TRMM卫星资料分析青藏高原（TP）、中国东部（EC）及北美副热带西部（WNA）和东部（ENA）降水系统的发生频次,定义降水系统为TRMM测雨雷达观测到近地面有降水的相邻像元组成的个体,即RPF （Radar Precipitation Feature）,将RPF分为全体RPF、大面积RPF（面积＞1000 km2）和小面积RPF（面积不＜400 km2）3组,对比分析四个区域内各组的RPF个数发生频次和RPF像元个数发生频次,主要结果如下：（1）全体RPF的个数发生频次在青藏高原地区最高,北美东部地区最低;全体RPF的降水像元个数发生频次在中国东部最高,青藏高原最低。（2）四个区域内RPF发生频次的日变化主要为单峰结构,峰值出现在当地午后至傍晚,且大面积RPF的峰值时间晚于小面积RPF的;中国东部地区RPF降水像元个数发生频次则具有双峰结构。（3）RPF降水像元个数发生频次的分析结果与以往基于地面观测降水量的分析结果相似。  相似文献   

一种改进的数值预报降水偏差订正方法及应用   总被引：3，自引：3，他引：0       下载免费PDF全文

孙靖  程光光  张小玲 《应用气象学报》2015,26(2):173-184

对传统的消除偏差法进行改进,形成分等级消除偏差法,并使用混合训练期和60 d滑动训练期方案分别对2012年6—8月ECMWF (European Centre for Medium-Range Weather Forecasting) 模式夏季1~5 d的降水预报进行订正试验。为了尽可能符合中国东部夏季降水具有移动性及多种时间尺度变化的特点,混合训练期以预报期前30 d与预报期前一年同日的前后各15 d组成。结果表明:在使用分等级消除偏差法的基础上,相比ECMWF模式降水预报,两种训练期方案的订正结果几乎对各个阈值的ETS评分均有一定提高,特别是对25 mm以上降水预报评分的提高幅度,混合训练期方案的订正结果明显高于60 d滑动训练期方案;在区域性强降水预报的订正中,混合训练期方案优势更为明显。另外,通过分析两种训练期方案的预报偏差发现,分等级订正是此次消除偏差订正试验中提高强降水预报评分的关键,选择合适的训练期可以增加评分提高的幅度。由于上述试验使用的ECMWF模式预报和站点实况均是业务上常用数据,因此,该方法具有一定的业务应用价值。  相似文献